Organism growth and the environment

WEBVTT
Kind: captions
Language: en

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- [Instructor] Hey, have you ever seen

00:00:01.760 --> 00:00:03.120
this kind of plant before?

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It's called a dandelion.

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If you live in a tropical
climate, it might be unfamiliar,

00:00:07.970 --> 00:00:10.010
but if you live in a more temperate zone,

00:00:10.010 --> 00:00:13.080
you'll probably recognize it
as it's a very common plant.

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Dandelions make yellow flowers
that develop into balls

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of these fluffy white seed
heads that fly off the plant.

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This can happen by a gust of wind,

00:00:22.070 --> 00:00:23.560
by animals spreading them,

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or even by someone blowing on the plant.

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When this happens, it
seeds fly into the air

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and land on new spots on the ground.

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From there, the seeds can
grow into new dandelions,

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starting the whole cycle over.

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But why do dandelions do this?

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Why do they turn into puff balls?

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Why are they yellow?

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If they don't have brains,

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how do they seem to know
when to release their seeds?

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These are all complicated questions.

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But to begin answering them,

00:00:53.090 --> 00:00:56.440
we can talk about what influences
the growth and development

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of dandelions and in
turn all living things.

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So what determines how
a dandelion will grow?

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Its genes and its environment.

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Let's take a moment to
review what genes are.

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Genes make up the hereditary material

00:01:12.370 --> 00:01:14.540
inside an organism cells.

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Genes provide the information

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about what traits an organism has.

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So the reason that our
dandelion has yellow pedals

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and develops fluffy white seed heads

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lies within its genes.

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Any influence genes have on
the way an organism grows

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is called a genetic factor.

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So if one dandelion has
more seeds than another

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as a result of which version
of a certain gene it has,

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we can say that the
difference in seed number

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is due to a genetic factor.

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The other major influence
on how a dandelion grows

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is its environment.

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But what makes up an
organism's environment?

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The environment is the set of conditions

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an organism is exposed to during its life.

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For a dandelion, this
includes temperature,

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how much light and water it gets,

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and which nutrients
are present in the soil

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where it grows.

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Any influence the environment
has on an organism's growth

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is called an environmental factor.

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So if one dandelion plant
is exposed to more sunlight

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than another and grows
bigger, as a result,

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we can say that the difference is due

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to an environmental factor.

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But plants aren't the
only living organisms

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that are motivated by these factors.

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Animals are also influenced by
their genes and environment.

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For example, let's look at dogs.

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Dogs come in many different
shapes, sizes, colors,

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and each have their own unique features.

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We can see this when
looking at different breeds,

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like pugs which are
small with squishy faces,

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and golden retrievers,

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which are large with
flowing locks of golden fur.

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These traits are largely determined

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by which genes each breed of dog has,

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or in other words, by genetic factors.

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But dogs are also influenced
by environmental factors too.

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For instance, how much
food they get as they grow

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helps determine their size,

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and what they learn from other dogs,

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and from people help
determine their behaviors.

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Like when you teach your dog a new trick.

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And now you know how
organisms are influenced

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by genetics and their environment

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when it comes to growth and development.

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Let's do a quick review of
what you've learned today.

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First, there are two main factors

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that influence an organism's growth,

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these are genetic and
environmental factors.

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Genetic factors are the
genes the organism gets

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from its parent or parents.

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While environmental
factors are the conditions

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and organism is exposed to as it grows.

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These factors show that
all living organisms

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have a couple things in common
even dogs and dandelions.

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So while our interactions
with them may differ

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like how you can't
teach a dandelion to sit

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like you can with a dog,

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both organisms experience
growth and development

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through their own unique
genes and environments.


Sensory processing and the brain

WEBVTT
Kind: captions
Language: en

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- [Narrator] As humans,
we have a lot of senses

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that we put to use on a regular basis.

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They include sight, smell,
taste, touch, and hearing.

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But have you ever
wondered how it all works?

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How do you look at a beautiful
painting in an art museum,

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or smell the rain outside on a stormy day,

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or feel that your favorite pair of socks

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are still a little damp,

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and need another cycle in the dryer?

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How does that information make its way

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from our sensory organs to our brains?

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Well, the answer lies
in the nervous system.

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If you remember, our bodies are made up

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of multiple complex organ
systems that work together

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to perform all different
kinds of functions.

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Today, let's talk specifically
about the nervous system,

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which is an organ system that allows us

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to sense and respond to our environment.

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To begin, the nervous system
contains specialized cells

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and cell parts, called sensory receptors,

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which are able to pick up
signals from the environment.

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These signals are called stimuli,

00:01:01.760 --> 00:01:04.970
or stimulus if you're
talking about just one.

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Stimuli can come in many different forms.

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For instance, mechanical
stimuli are physical in nature,

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and are involved with our
senses of touch and hearing.

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You can strum a guitar,

00:01:16.910 --> 00:01:19.360
feeling the strings
against your fingertips,

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and listening to the
unique tones it produces

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as the strings vibrate.

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Those are all mechanical stimuli.

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Chemical stimuli are made up of molecules,

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and are involved with our
senses of smell and taste.

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To illustrate an example,

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imagine eating a tasty bowl
of chicken noodle soup.

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As you spoon mouthfuls
of soup into your mouth,

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your taste and olfactory receptors

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are flooded with molecules

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that signal the qualities
of the food you're eating.

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These molecular signals
are chemical stimuli.

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And in this case,

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the molecules from the chicken noodle soup

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convey that the food
you're eating is savory,

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and extremely delicious.

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Lastly, electromagnetic stimuli

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are involved with our sense of sight,

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and include the light that
comes into our eyes every day.

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The sunlight that makes you squint,

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the traffic lights you see on the street,

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and the vibrant and diverse
colors all around you.

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These are just a few examples

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of electromagnetic stimuli
in the form of light.

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So then what happens after
sensory receptors detect stimuli?

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Well, once a sensory receptor
receives the information,

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it passes this information
along nerve cells.

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Here's a picture of a nerve cell,

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which is specialized
to transmit information

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in the form of electrical signals.

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These signals are transmitted
along nerves to the brain,

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which is then responsible for processing,

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or organizing sensory information

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from different sensory receptors.

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After processing the information,

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the brain can elicit a response,

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and also store the information
in the form of a memory

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for future use.

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For example, imagine you're playing catch

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with friends in a park.

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Your sensory receptors pick up information

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as you watch the ball come towards you,

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and feel the wind on your skin.

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Signals from these receptors

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travel along nerve cells to your brain,

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where all these different
signals are organized.

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Then your brain elicits a response,

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such as moving to just the right spot,

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and putting your hands
out to catch the ball.

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And the brain also stores a memory,

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perhaps remembering playing catch

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as a fun activity that
you'd wanna do again.

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You can almost think of
this flow of information

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from a stimulus to sensing, to processing,

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and finally, to eliciting a
response or storing information,

00:03:35.230 --> 00:03:37.660
like a complex relay race.

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Sensory receptors pick up
message in the form of stimuli,

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and pass this information along
to nerves, and to the brain.

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Only in this relay, the end
result at the finish line

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is a response to the stimulus
and information storage.

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So to summarize,

00:03:52.760 --> 00:03:55.270
today, we talked about
how our bodies sense,

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and respond to the environment.

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Information is transferred from a stimulus

00:04:00.110 --> 00:04:02.880
to a sensory receptor, to nerve cells,

00:04:02.880 --> 00:04:06.350
and finally to the brain,
where processing occurs.

00:04:06.350 --> 00:04:08.210
Whether we're aware of it or not,

00:04:08.210 --> 00:04:12.400
our nervous system is working
at rapid-fire speed every day

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to provide us with the information

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our bodies need to sense
what's in our environment,

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and thrive in it.


Writing fraction division story problems

WEBVTT
Kind: captions
Language: en

00:00:00.180 --> 00:00:04.100
- [Instructor] We're told
that Darryl spent 24 1/4 hours

00:00:04.100 --> 00:00:06.610
writing a chapter of a novel.

00:00:06.610 --> 00:00:11.090
And then they ask us, what
are some things that 24 1/4

00:00:11.090 --> 00:00:16.090
divided by 3/4 could
represent in this context?

00:00:16.290 --> 00:00:18.090
So my understanding of this

00:00:18.090 --> 00:00:21.280
is they really just want us
to be a little bit creative

00:00:21.280 --> 00:00:24.610
about what division by a fraction

00:00:24.610 --> 00:00:28.270
could represent in a given context.

00:00:28.270 --> 00:00:31.190
So, well, one, I encourage
you to pause your video

00:00:31.190 --> 00:00:34.100
and think about that a little
bit before I think about it.

00:00:34.100 --> 00:00:39.100
But one thing I think about
is, well, if I took 24 1/4,

00:00:39.340 --> 00:00:43.280
and if I were to divide it
into chunks of 3/4 of an hour

00:00:43.280 --> 00:00:47.140
because this is in hours,
how many chunks would I have?

00:00:47.140 --> 00:00:52.080
So this could represent,
let's say that he spent,

00:00:52.080 --> 00:00:55.280
he spent 45 minutes,

00:00:55.280 --> 00:00:57.140
which is the same thing of 3/4 of an hour,

00:00:57.140 --> 00:01:00.950
3/4 hours, of an hour, I should say,

00:01:00.950 --> 00:01:05.950
3/4 of an hour each day.

00:01:08.710 --> 00:01:13.710
How many days, how many days
did it take him, did it take?

00:01:19.990 --> 00:01:24.670
And then you could evaluate
this, 24 1/4 divided by 3/4.

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We've talked about how to
evaluate that in other videos.

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So that's one context.

00:01:29.270 --> 00:01:34.270
Another one could be some
type of a comparison.

00:01:34.470 --> 00:01:36.520
So let's say that 24 1/4

00:01:36.520 --> 00:01:41.250
is 3/4 of the amount of time

00:01:41.250 --> 00:01:43.950
that he spent doing something else.

00:01:43.950 --> 00:01:47.630
So let's say, so this is now a
completely different context.

00:01:47.630 --> 00:01:48.640
I'm gonna put a line here.

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I'll do it in a different
color just to make it clear

00:01:50.460 --> 00:01:52.030
it's a different context.

00:01:52.030 --> 00:01:55.860
So another one could be to
justify doing this division,

00:01:55.860 --> 00:02:00.720
he spent 3/4 as long writing,

00:02:03.230 --> 00:02:08.230
writing as he spent illustrating,

00:02:10.120 --> 00:02:12.713
illustrating the chapter.

00:02:14.390 --> 00:02:15.630
And so then the question

00:02:15.630 --> 00:02:18.380
is how long did he spend illustrating?

00:02:18.380 --> 00:02:23.380
How long did he spend illustrating?

00:02:27.510 --> 00:02:29.030
Now, I really want you
to think about this one.

00:02:29.030 --> 00:02:31.900
My brain, actually, this one
takes a little bit longer

00:02:31.900 --> 00:02:34.280
for my brain to process.

00:02:34.280 --> 00:02:35.240
But when you think about it,

00:02:35.240 --> 00:02:38.280
if you divide by a fraction
that is less than one,

00:02:38.280 --> 00:02:39.700
you're gonna get a number larger

00:02:39.700 --> 00:02:41.600
than the one that you're dealing with.

00:02:41.600 --> 00:02:43.410
Or another way to think about it,

00:02:43.410 --> 00:02:47.600
the time spent illustrating,
time illustrating,

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I'll write it like this,

00:02:48.870 --> 00:02:52.330
the time illustrating times 3/4

00:02:52.330 --> 00:02:55.030
should be equal to the time spent writing

00:02:55.030 --> 00:02:57.280
because it says he spent,

00:02:57.280 --> 00:03:00.110
or he spent, I forgot to write that,

00:03:00.110 --> 00:03:03.550
he spent 3/4 as long writing
as he spent illustrating.

00:03:03.550 --> 00:03:05.430
So time illustrating times 3/4

00:03:05.430 --> 00:03:08.810
should be time writing or 24 1/4.

00:03:08.810 --> 00:03:12.530
So if something times
3/4 is equal to 24 1/4,

00:03:12.530 --> 00:03:17.530
then 24 1/4 divided by 3/4

00:03:18.090 --> 00:03:23.090
should be equal to time illustrating.

00:03:23.710 --> 00:03:26.240
So these are the two
contexts that I can think of

00:03:26.240 --> 00:03:27.170
that might make sense,

00:03:27.170 --> 00:03:29.220
but you might be able to think of others.


Area with fraction division example

WEBVTT
Kind: captions
Language: en

00:00:00.540 --> 00:00:02.840
- [Instructor] We're told a
yoga mat is 3/5 of a meter wide.

00:00:02.840 --> 00:00:06.620
It has an area of 1
and 2/25 square meters.

00:00:06.620 --> 00:00:09.250
What is the length of the mat?

00:00:09.250 --> 00:00:12.100
Well, we know that length times width

00:00:12.100 --> 00:00:14.260
is going to give you area,

00:00:14.260 --> 00:00:16.070
or another way of thinking about it,

00:00:16.070 --> 00:00:19.040
if the product of two numbers
gives you a third number,

00:00:19.040 --> 00:00:20.170
if you take that third number

00:00:20.170 --> 00:00:21.720
and divide it by one of these,

00:00:21.720 --> 00:00:22.700
you're going to get the other one.

00:00:22.700 --> 00:00:23.770
So another way of thinking about it

00:00:23.770 --> 00:00:28.770
is length would be the same
thing as area divided by width.

00:00:29.460 --> 00:00:32.200
So we're trying to figure
out the length here.

00:00:32.200 --> 00:00:34.550
We have the area, we have the width.

00:00:34.550 --> 00:00:37.980
So our length is going to be 1 and 2/25,

00:00:37.980 --> 00:00:42.980
1 and 2/25 divided by 3/5.

00:00:44.730 --> 00:00:46.970
Now this is going to be the same thing as,

00:00:46.970 --> 00:00:49.320
let me write this as an improper fraction,

00:00:49.320 --> 00:00:52.430
it's gonna be easier to do
some arithmetic with it.

00:00:52.430 --> 00:00:57.430
So one is the same thing
as 25/25, plus 2/25,

00:00:58.030 --> 00:01:03.030
this is 27/25 divided by 3/5.

00:01:05.630 --> 00:01:07.590
And we've already talked
about how this is saying

00:01:07.590 --> 00:01:11.250
how many 3/5 can fit into 27/25.

00:01:11.250 --> 00:01:13.860
And we've given the intuition
why this is the same thing

00:01:13.860 --> 00:01:18.860
as just multiplying 27/25
times the reciprocal of 3/5,

00:01:21.030 --> 00:01:24.230
which is 5/3.

00:01:24.230 --> 00:01:26.270
And so this is going to be equal to,

00:01:26.270 --> 00:01:28.300
and actually I'm gonna
factor this out a little bit

00:01:28.300 --> 00:01:30.340
to simplify things a bit.

00:01:30.340 --> 00:01:34.110
27 is 3 x 3 x 3.

00:01:34.110 --> 00:01:36.910
25 is 5 x 5.

00:01:36.910 --> 00:01:38.120
So this is going to be equal to,

00:01:38.120 --> 00:01:40.980
in our numerator we're
gonna have 3 x 3 x 3 x 5.

00:01:40.980 --> 00:01:45.250
3 x 3 x 3 x 5.

00:01:45.250 --> 00:01:49.220
And then in our denominator
we're gonna have 5 x 5 x 3.

00:01:49.220 --> 00:01:52.290
5 x 5 x 3.

00:01:52.290 --> 00:01:55.310
And then we can reduce this a little bit.

00:01:55.310 --> 00:01:56.670
We can divide both the numerator

00:01:56.670 --> 00:01:58.180
and the denominator by five.

00:01:58.180 --> 00:01:59.470
We can divide both the numerator

00:01:59.470 --> 00:02:01.290
and the denominator by three.

00:02:01.290 --> 00:02:06.290
So in the numerator, we're
gonna 3 x 3, which is 9/5.

00:02:06.680 --> 00:02:09.820
So this is all going to be equal to 9/5.

00:02:09.820 --> 00:02:13.380
So the yoga mat is 3/5 of a meter wide

00:02:13.380 --> 00:02:16.690
and 9/5 of a meter long.

00:02:16.690 --> 00:02:19.320
Now let's make sure that this makes sense.

00:02:19.320 --> 00:02:21.030
So I'm gonna make a grid.

00:02:21.030 --> 00:02:26.030
So this right over here is 1/5 of a meter.

00:02:26.998 --> 00:02:29.050
1/5 of a meter in that dimension

00:02:29.050 --> 00:02:33.600
and 1/5 of a meter in that dimension.

00:02:33.600 --> 00:02:38.600
And then we can see, well,
if this is 1/5 of a meter,

00:02:38.840 --> 00:02:43.840
then the width right over
here is 3/5 of a meter.

00:02:44.125 --> 00:02:47.810
Our length right over
here, we have 1, 2, 3, 4,

00:02:47.810 --> 00:02:50.670
5, 6, 7, 8, 9, fifths.

00:02:50.670 --> 00:02:52.780
It is 9/5.

00:02:52.780 --> 00:02:56.900
Now each of these units, what is its area?

00:02:56.900 --> 00:03:01.750
Well, it is 1/25 meter squared.

00:03:01.750 --> 00:03:03.530
And how many of these do we have?

00:03:03.530 --> 00:03:07.810
Well, we can see, we
have three rows of nine,

00:03:07.810 --> 00:03:11.350
which is 27 of these 25ths,

00:03:11.350 --> 00:03:14.280
so we're gonna have 27/25 square meters,

00:03:14.280 --> 00:03:17.833
which is the same thing as
1 and 2/5 square meters.


Decimal multiplication place value

WEBVTT
Kind: captions
Language: en

00:00:00.620 --> 00:00:02.280
- [Instructor] This is an
exercise from Khan Academy.

00:00:02.280 --> 00:00:04.750
It tells us that the product 75 times 61

00:00:04.750 --> 00:00:08.110
is equal to 4,575.

00:00:08.110 --> 00:00:10.545
Use a previous fact to
evaluate as a decimal.

00:00:10.545 --> 00:00:11.734
This right over here,

00:00:11.734 --> 00:00:15.900
7.5 times 0.061.

00:00:15.900 --> 00:00:19.110
Pause this video and see
if you can have a go at it.

00:00:19.110 --> 00:00:21.280
All right, now let's do this together.

00:00:21.280 --> 00:00:23.110
So the first thing that you might realize

00:00:23.110 --> 00:00:28.110
is that 7.5 is the same thing as 75

00:00:28.290 --> 00:00:31.770
divided by 10.

00:00:31.770 --> 00:00:33.890
And 0.061,

00:00:33.890 --> 00:00:37.010
this is 61 thousandths.

00:00:37.010 --> 00:00:42.010
This right over here
is the same thing as 61

00:00:42.180 --> 00:00:45.770
divided by 1,000

00:00:45.770 --> 00:00:49.140
and we're gonna take the
product of these two things.

00:00:49.140 --> 00:00:51.530
Another way we could write this,

00:00:51.530 --> 00:00:53.540
75 divided by 10,

00:00:53.540 --> 00:00:54.450
this is the same thing

00:00:54.450 --> 00:00:57.490
as 75 over 10

00:00:57.490 --> 00:00:59.100
and I'm gonna take the product of that,

00:00:59.100 --> 00:01:03.490
and 61 thousandths, 61 divided by 1,000.

00:01:03.490 --> 00:01:08.490
So that would be 61/1,000.

00:01:09.130 --> 00:01:10.240
Now, when we look at it,

00:01:10.240 --> 00:01:11.380
either of these ways,

00:01:11.380 --> 00:01:13.430
well actually, I'll do both
of them at the same time.

00:01:13.430 --> 00:01:14.430
You could change the order

00:01:14.430 --> 00:01:16.120
of the multiplication
and the division here.

00:01:16.120 --> 00:01:19.800
So you could start with 75 times 61,

00:01:19.800 --> 00:01:22.760
75 times 61,

00:01:22.760 --> 00:01:24.923
and then divide that by 10,

00:01:26.160 --> 00:01:29.790
and then divide that by 1,000.

00:01:29.790 --> 00:01:32.020
You could do it that way

00:01:32.020 --> 00:01:34.130
or you could look right over here

00:01:34.130 --> 00:01:35.380
and say, all right,

00:01:35.380 --> 00:01:36.820
if I'm taking this product,

00:01:36.820 --> 00:01:39.970
my numerator is going to be 75 times 61,

00:01:39.970 --> 00:01:42.230
75 times 61.

00:01:42.230 --> 00:01:44.690
And then, my denominator

00:01:44.690 --> 00:01:48.000
is going to be 10 times 1,000

00:01:48.000 --> 00:01:49.380
which is essentially the same thing

00:01:49.380 --> 00:01:51.210
as dividing by 10,

00:01:51.210 --> 00:01:53.170
and then dividing by 1,000.

00:01:53.170 --> 00:01:57.220
And of course, that is going to be 10,000.

00:01:57.220 --> 00:02:00.900
Now on the left-hand
side, right over here,

00:02:00.900 --> 00:02:04.420
they told us what this is, it's 4,575.

00:02:04.420 --> 00:02:05.440
So it's 4,575

00:02:07.590 --> 00:02:08.920
divided by 10,

00:02:08.920 --> 00:02:10.310
and then divided by 1,000.

00:02:10.310 --> 00:02:11.470
Well, if I divide by 10,

00:02:11.470 --> 00:02:13.150
and then I divide by 1,000,

00:02:13.150 --> 00:02:17.240
that's equivalent to dividing by 10,000.

00:02:17.240 --> 00:02:21.303
This is dividing by 10,000

00:02:22.480 --> 00:02:23.530
and you could see that over here.

00:02:23.530 --> 00:02:25.140
We're dividing by 10,000

00:02:25.140 --> 00:02:26.480
as well right over here.

00:02:26.480 --> 00:02:29.040
And the 75 times 61,

00:02:29.040 --> 00:02:32.850
this is 4,575.

00:02:32.850 --> 00:02:35.130
Now they want us to
evaluate it as a decimal.

00:02:35.130 --> 00:02:37.080
We've now expressed it as a fraction

00:02:37.080 --> 00:02:39.720
and I still haven't
fully evaluated this yet.

00:02:39.720 --> 00:02:41.030
So we really wanna think

00:02:41.030 --> 00:02:44.631
about this as 4,575 ten thousandths

00:02:44.631 --> 00:02:46.630
and you can see that very explicitly here.

00:02:46.630 --> 00:02:50.350
There's 4,575 ten thousandths.

00:02:50.350 --> 00:02:52.260
So how do we write that?

00:02:52.260 --> 00:02:55.680
Well, if I have a decimal right over here,

00:02:55.680 --> 00:02:57.450
that's the tenths place.

00:02:57.450 --> 00:02:59.510
This is the hundredths,

00:02:59.510 --> 00:03:02.820
thousandths, ten-thousandths place.

00:03:02.820 --> 00:03:05.140
So we have this many ten thousandths,

00:03:05.140 --> 00:03:09.410
4,575 ten thousandths

00:03:10.290 --> 00:03:11.300
and we're done.

00:03:11.300 --> 00:03:16.193
So this is gonna be 0.4575.

00:03:16.193 --> 00:03:19.360
Now I know what some of
you might be thinking.

00:03:19.360 --> 00:03:21.700
Hey, I learned a technique

00:03:21.700 --> 00:03:23.710
where if I'm taking the
product of two numbers,

00:03:23.710 --> 00:03:25.790
I could take the product
of those two numbers,

00:03:25.790 --> 00:03:27.020
or if I'm taking the
product of two numbers

00:03:27.020 --> 00:03:28.260
that are decimals,

00:03:28.260 --> 00:03:31.280
I could remove the decimals
from them essentially,

00:03:31.280 --> 00:03:32.140
take their product

00:03:32.140 --> 00:03:34.240
which they actually
gave us right over here.

00:03:34.240 --> 00:03:36.360
And then, count how
many digits to the right

00:03:36.360 --> 00:03:38.540
of the decimal there were
in our original numbers.

00:03:38.540 --> 00:03:42.190
So we have one, two, three,

00:03:42.190 --> 00:03:46.410
four digits to the right of the decimal.

00:03:46.410 --> 00:03:48.212
And so what I do is I then move,

00:03:48.212 --> 00:03:50.020
I then make sure that there's four digits

00:03:50.020 --> 00:03:52.030
to the right of the
decimal in the product.

00:03:52.030 --> 00:03:53.500
And so I would say, okay,

00:03:53.500 --> 00:03:55.970
one, two, three, four, that looks good

00:03:55.970 --> 00:03:57.660
and I've gotten the same answer

00:03:57.660 --> 00:03:59.380
a lot faster than we just did it.

00:03:59.380 --> 00:04:01.810
Well, whole reason why I
just did it the way I did

00:04:01.810 --> 00:04:04.240
is to show you why that works.

00:04:04.240 --> 00:04:07.160
When we take the product
of the two numbers

00:04:07.160 --> 00:04:08.590
without the decimals,

00:04:08.590 --> 00:04:10.170
we're essentially ignoring the fact

00:04:10.170 --> 00:04:12.530
that the original product
was dividing by 10

00:04:12.530 --> 00:04:14.290
and dividing by 1,000,

00:04:14.290 --> 00:04:16.390
and that's because we had one digit

00:04:16.390 --> 00:04:17.960
behind to the right of the decimal here,

00:04:17.960 --> 00:04:20.350
and we had three digits to the
right of the decimal there.

00:04:20.350 --> 00:04:23.000
And so later after we take the product,

00:04:23.000 --> 00:04:25.700
we have to go and then
actually take that product

00:04:25.700 --> 00:04:27.260
and divide by 10,

00:04:27.260 --> 00:04:28.490
and divide by 1,000

00:04:28.490 --> 00:04:30.290
or divide by 10,000.

00:04:30.290 --> 00:04:32.900
So that's why you can then
just say, all right, well now,

00:04:32.900 --> 00:04:34.630
we originally had four
digits to the right,

00:04:34.630 --> 00:04:36.460
so we still have to have four digits

00:04:36.460 --> 00:04:38.160
to the right of the decimal point.


Noble’s Story

WEBVTT
Kind: captions
Language: en

00:00:00.000 --> 00:00:01.810
- That was one of the
best days of my life.

00:00:01.810 --> 00:00:03.180
Honestly, like signing day,

00:00:03.180 --> 00:00:05.270
just knew that all the
hard work that I had put

00:00:05.270 --> 00:00:07.280
into this dream final paid off.

00:00:07.280 --> 00:00:09.940
I'm Noble. I'm a freshman
at Brown University.

00:00:09.940 --> 00:00:11.420
I play receiver on the football team.

00:00:11.420 --> 00:00:14.280
It became apparent to me that
when I got to high school

00:00:14.280 --> 00:00:16.220
that if I wanted to achieve the goals

00:00:16.220 --> 00:00:18.012
of going Division One football

00:00:18.012 --> 00:00:19.800
and going to school in the Ivy League,

00:00:19.800 --> 00:00:22.180
that I needed to improve on my SAT scores.

00:00:22.180 --> 00:00:25.170
A lot of people like my
peers have test anxiety.

00:00:25.170 --> 00:00:27.390
First time I took it, I got a 1210.

00:00:27.390 --> 00:00:29.510
I knew I needed to
improve if I wanted to get

00:00:29.510 --> 00:00:31.420
to a level of school that I'd envisioned.

00:00:31.420 --> 00:00:34.330
So, I dug into Khan Academy a lot.

00:00:34.330 --> 00:00:37.860
I took advantage of the option
to upload your SAT scores

00:00:37.860 --> 00:00:40.050
to Khan Academy, and it
would give you feedback

00:00:40.050 --> 00:00:41.540
on things you needed to work on.

00:00:41.540 --> 00:00:44.030
I definitely took a lot of
stress off of my shoulders

00:00:44.030 --> 00:00:45.140
and like having the confidence

00:00:45.140 --> 00:00:47.460
that I could truly go
into this test and perform

00:00:47.460 --> 00:00:49.900
to the standards that I
wanted. By using Khan Academy

00:00:49.900 --> 00:00:53.318
I was able to improve my
SAT score by 210 points.

00:00:53.318 --> 00:00:54.900
I was able to get a 1420,

00:00:54.900 --> 00:00:56.860
and that was a score that
got me accepted in the Brown.

00:00:56.860 --> 00:00:58.240
Definitely would say it's life changing.

00:00:58.240 --> 00:01:00.010
I set my life on trajectory

00:01:00.010 --> 00:01:01.360
that wouldn't have been available

00:01:01.360 --> 00:01:02.960
if I didn't have access to Khan Academy.

00:01:02.960 --> 00:01:04.700
Whether you're upper class or lower class,

00:01:04.700 --> 00:01:06.717
or anywhere you fall in between those,

00:01:06.717 --> 00:01:08.770
and it's free and available for everyone.

00:01:08.770 --> 00:01:11.120
And that's, I can't stress that enough.

00:01:11.120 --> 00:01:14.030
I wanna leave a message
that anything is possible.

00:01:14.030 --> 00:01:16.760
I definitely think the best
beginning spot would be

00:01:16.760 --> 00:01:17.810
through Khan Academy.


Dividing a whole number by a fraction with reciprocal

WEBVTT
Kind: captions
Language: en

00:00:00.180 --> 00:00:02.010
- [Instructor] In this video,
we're gonna do an example

00:00:02.010 --> 00:00:03.480
that gives us a little bit of practice

00:00:03.480 --> 00:00:05.960
to think about what does it
mean to divide by a fraction?

00:00:05.960 --> 00:00:06.860
So if we wanna figure out

00:00:06.860 --> 00:00:09.500
what eight divided by 7/5 is,

00:00:09.500 --> 00:00:12.170
but we're gonna break
it down into two steps.

00:00:12.170 --> 00:00:14.410
First of all, we're gonna
use these visuals here

00:00:14.410 --> 00:00:19.000
to think about how many
groups of 7/5 are in one.

00:00:19.000 --> 00:00:20.110
Or another way of thinking about it

00:00:20.110 --> 00:00:24.100
is how these 7/5 are in a whole?

00:00:24.100 --> 00:00:27.000
So pause this video, and just
think about this first part.

00:00:28.100 --> 00:00:31.600
All right, so let's look at 7/5.

00:00:31.600 --> 00:00:36.600
7/5 is everything from
here, all the way to there.

00:00:37.360 --> 00:00:40.730
And then one is this.

00:00:40.730 --> 00:00:44.520
So how many 7/5 are in one?

00:00:44.520 --> 00:00:45.730
Well, you can see that one,

00:00:45.730 --> 00:00:50.120
which is the same thing
as 5/5, is less than 7/5.

00:00:50.120 --> 00:00:53.560
So it's actually going
to be a fraction of a 7/5

00:00:53.560 --> 00:00:57.090
that is one, or that is in one.

00:00:57.090 --> 00:00:59.500
And you can see what that fraction is.

00:00:59.500 --> 00:01:02.750
One is what fraction of 7/5.

00:01:02.750 --> 00:01:04.270
Well, if you look at the fifths,

00:01:04.270 --> 00:01:08.760
7/5 is of course seven of
them, and a whole is 5/5,

00:01:08.760 --> 00:01:13.760
so five of the 7/5 make a whole.

00:01:13.760 --> 00:01:17.980
So the answer right over here is 5/7.

00:01:17.980 --> 00:01:22.980
5/7 of a 7/5 is equal to one.

00:01:23.460 --> 00:01:25.400
You can also see this right over here.

00:01:25.400 --> 00:01:28.460
If you take each of these to be a fifth,

00:01:28.460 --> 00:01:31.720
each of these to be a fifth,

00:01:31.720 --> 00:01:36.720
then this whole bar is equal to 7/5.

00:01:36.760 --> 00:01:39.080
And the blue part is equal to one.

00:01:39.080 --> 00:01:41.630
So how many 7/5 are in the blue part?

00:01:41.630 --> 00:01:45.520
Well, we can see it's
5/7 of the whole bar.

00:01:45.520 --> 00:01:48.020
Once again, 5/7 of the whole bar.

00:01:48.020 --> 00:01:48.992
So we can also think about this

00:01:48.992 --> 00:01:53.350
as one divided by 7/5.

00:01:53.350 --> 00:01:57.190
This is another way of saying
how many 7/5 are in one,

00:01:57.190 --> 00:01:59.820
or how many groups of 7/5 are in one?

00:01:59.820 --> 00:02:02.890
And this is equal to 5/7,

00:02:02.890 --> 00:02:04.610
which we've learned in other videos

00:02:04.610 --> 00:02:06.590
is the reciprocal of 7/5.

00:02:06.590 --> 00:02:09.800
The numerator and the
denominator is swapped.

00:02:09.800 --> 00:02:14.150
So now what is eight
divided by 7/5 going to be?

00:02:14.150 --> 00:02:17.960
Well, if one divided by 7/5 is 5/7,

00:02:17.960 --> 00:02:21.540
or if you have 5/7 of a 7/5,

00:02:21.540 --> 00:02:22.950
of a 7/5 in one,

00:02:22.950 --> 00:02:25.260
I know the oral language
gets a little bit confusing.

00:02:25.260 --> 00:02:28.350
Well, you're going to have
eight times that many in eight.

00:02:28.350 --> 00:02:29.860
So this is going to be the same thing

00:02:29.860 --> 00:02:34.510
as eight times, we could do it this way,

00:02:34.510 --> 00:02:39.030
eight times one, divided by 7/5.

00:02:39.030 --> 00:02:41.960
Or you could just view this as eight times

00:02:41.960 --> 00:02:46.910
the reciprocal of 7/5,
which is five over seven.

00:02:48.150 --> 00:02:50.900
And we've learned how
to multiply this before.

00:02:50.900 --> 00:02:54.130
Eight times 5/7 is going to be equal

00:02:54.130 --> 00:02:58.170
to 40/7, and we're done.

00:02:58.170 --> 00:03:00.280
You could obviously also
write that as a mixed number

00:03:00.280 --> 00:03:05.253
if you like, this would be
the same thing as 5 5/7.

00:03:06.890 --> 00:03:10.000
So the big picture is when we think about

00:03:10.000 --> 00:03:13.030
how many of a fraction are in one,

00:03:13.030 --> 00:03:14.140
that's the same thing as saying,

00:03:14.140 --> 00:03:16.240
what's one divided by that fraction?

00:03:16.240 --> 00:03:17.980
As you see visually here,

00:03:17.980 --> 00:03:20.330
you essentially get the
reciprocal of that fraction.

00:03:20.330 --> 00:03:22.970
And so if you take any
other number other than one

00:03:22.970 --> 00:03:24.350
divided by that fraction,

00:03:24.350 --> 00:03:25.652
you're essentially just gonna multiply it

00:03:25.652 --> 00:03:30.000
by that reciprocal, because
it's that number times one.

00:03:30.000 --> 00:03:32.120
So when you divide by that fraction,

00:03:32.120 --> 00:03:34.683
it's that number times the reciprocal.


Area of quadrilateral with 2 parallel sides

WEBVTT
Kind: captions
Language: en

00:00:00.350 --> 00:00:02.140
- [Instructor] What we're going
to try to do in this video

00:00:02.140 --> 00:00:04.430
is find the area of this figure.

00:00:04.430 --> 00:00:05.930
And we can see it's a quadrilateral.

00:00:05.930 --> 00:00:08.740
It has 1, 2, 3, 4 sides.

00:00:08.740 --> 00:00:11.180
And we know that this side and this side

00:00:11.180 --> 00:00:13.570
that they're parallel to each other.

00:00:13.570 --> 00:00:16.160
You can see that they
both form right angles

00:00:16.160 --> 00:00:18.080
with this dotted line.

00:00:18.080 --> 00:00:21.063
So pause this video and see
if you can find the area.

00:00:22.930 --> 00:00:23.763
All right.

00:00:23.763 --> 00:00:25.590
Now, if you had a little
bit of trouble with that

00:00:25.590 --> 00:00:27.160
I'll give you a hint.

00:00:27.160 --> 00:00:29.350
What if we were to take this quadrilateral

00:00:29.350 --> 00:00:32.220
and divide it into two triangles?

00:00:32.220 --> 00:00:35.470
So let me do this in a color
that you are likely to see.

00:00:35.470 --> 00:00:39.120
So if I were to draw a line like this

00:00:39.120 --> 00:00:43.670
it now divides the quadrilateral
into two triangles.

00:00:43.670 --> 00:00:47.630
If I were to take this
triangle right over here

00:00:47.630 --> 00:00:50.660
I could take it out and reorient it,

00:00:50.660 --> 00:00:54.990
so it looks something like this,

00:00:54.990 --> 00:00:59.290
where the base has length 8,

00:00:59.290 --> 00:01:03.220
and then the height right
over here, the height

00:01:03.220 --> 00:01:06.070
this has length 5.

00:01:06.070 --> 00:01:07.720
So that would be that triangle.

00:01:07.720 --> 00:01:10.890
And then, this triangle over here

00:01:10.890 --> 00:01:13.230
if you were to take it out
and reorient it a little bit

00:01:13.230 --> 00:01:14.440
it could look like this,

00:01:14.440 --> 00:01:16.220
where the base is 4,

00:01:16.220 --> 00:01:19.990
and the triangle looks something like,

00:01:19.990 --> 00:01:21.270
looks something like this.

00:01:21.270 --> 00:01:24.290
So the base is 4,

00:01:24.290 --> 00:01:27.240
and then the height is going to be 5.

00:01:27.240 --> 00:01:30.680
So this height right
over here, this height,

00:01:30.680 --> 00:01:32.290
we notice this is a right angle.

00:01:32.290 --> 00:01:34.630
So from here to here,
which is the same thing

00:01:34.630 --> 00:01:37.560
as from here to right over here,

00:01:37.560 --> 00:01:39.080
we know that this is 5.

00:01:39.080 --> 00:01:41.470
So that's my fairly big hint to you,

00:01:41.470 --> 00:01:44.540
if you know how to find
the area of a triangle.

00:01:44.540 --> 00:01:49.540
The area of a triangle we
know is 1/2 base times height.

00:01:50.140 --> 00:01:51.700
So the area of this one right over here

00:01:51.700 --> 00:01:56.700
is gonna be 1/2 times 8 times 5.

00:01:57.040 --> 00:01:58.840
And the area of this one over here

00:01:58.840 --> 00:02:02.480
is going to be 1/2 times the base,

00:02:02.480 --> 00:02:07.470
which is 4 times the height, which is 5.

00:02:07.470 --> 00:02:09.480
And we could evaluate each of these,

00:02:09.480 --> 00:02:10.840
or we could just add them together.

00:02:10.840 --> 00:02:12.580
That the area of the entire thing

00:02:12.580 --> 00:02:16.960
is going to be 1/2 times
this base right over here

00:02:16.960 --> 00:02:21.690
which is 8, times the height, which is 5,

00:02:21.690 --> 00:02:26.690
plus 1/2 times this side,

00:02:27.500 --> 00:02:30.640
you could do that as
the other base, times 4

00:02:30.640 --> 00:02:33.400
times that same height, times 5.

00:02:33.400 --> 00:02:35.260
And obviously, you
could just evaluate this

00:02:35.260 --> 00:02:38.330
or we could see some
interesting things about it.

00:02:38.330 --> 00:02:40.440
We could express this as well

00:02:40.440 --> 00:02:45.440
if we were to factor
out 1/2 and the 5 here.

00:02:45.520 --> 00:02:48.403
This could be rewritten as 1/2,

00:02:49.740 --> 00:02:54.250
1/2 times 8 plus 4,

00:02:54.250 --> 00:02:58.110
8 plus 4.

00:02:58.110 --> 00:03:03.110
And then, all of that, all of
that times 5 right over here.

00:03:03.830 --> 00:03:05.770
And so, another way you
could think about it is

00:03:05.770 --> 00:03:08.670
the average of the length
of these two bases.

00:03:08.670 --> 00:03:11.220
You could view this as base 1 and base 2,

00:03:11.220 --> 00:03:12.730
you multiply that times the height

00:03:12.730 --> 00:03:15.710
and you have the area
of this quadrilateral.

00:03:15.710 --> 00:03:16.970
Well, what's that going to be?

00:03:16.970 --> 00:03:19.344
8 plus 4 is 12.

00:03:19.344 --> 00:03:22.810
1/2 times 12, this is all going to be 6.

00:03:22.810 --> 00:03:27.560
6 times 5 is going to be
equal to 30 square units.

00:03:27.560 --> 00:03:28.393
You could have figured it out here too.

00:03:28.393 --> 00:03:32.570
1/2 times 8 is 4, times 5 is 20.

00:03:32.570 --> 00:03:35.230
And then, this would've
been 1/2 times 4 is 2,

00:03:35.230 --> 00:03:36.470
times 5 is 10.

00:03:36.470 --> 00:03:40.323
20 plus 10 is 30 square units once again.


Competition, predation, and mutualism

WEBVTT
Kind: captions
Language: en

00:00:00.770 --> 00:00:02.430
- [Instructor] All across ecosystems,

00:00:02.430 --> 00:00:05.940
we know that organisms
interact in specific ways

00:00:05.940 --> 00:00:07.880
and scientists use special words

00:00:07.880 --> 00:00:11.000
to describe these types of interaction,

00:00:11.000 --> 00:00:14.990
competition, predation and mutualism.

00:00:14.990 --> 00:00:16.900
So let's first talk about competition

00:00:16.900 --> 00:00:19.590
which we have already talked
about in other videos.

00:00:19.590 --> 00:00:22.210
In this picture here,
do you see competition?

00:00:22.210 --> 00:00:24.110
Pause this video and think about that.

00:00:25.350 --> 00:00:27.710
Well, one limited resource

00:00:27.710 --> 00:00:30.830
that these animals need
to survive is water.

00:00:30.830 --> 00:00:33.090
There's only a limited
amount in this watering hole

00:00:33.090 --> 00:00:36.140
over here and so you could
imagine there is competition

00:00:36.140 --> 00:00:38.650
not just amongst the
members of a population

00:00:38.650 --> 00:00:40.520
let's say between the zebra

00:00:40.520 --> 00:00:43.090
but also between members
of different species,

00:00:43.090 --> 00:00:45.630
between different
populations in a community.

00:00:45.630 --> 00:00:48.580
The zebras are not just competing
for water with each other

00:00:48.580 --> 00:00:50.160
but also with these antelope

00:00:50.160 --> 00:00:52.880
or with these buffalo over here.

00:00:52.880 --> 00:00:54.840
There might also be competition for food.

00:00:54.840 --> 00:00:57.140
It doesn't seem like there's
a lot of grass to eat

00:00:57.140 --> 00:01:00.460
for all of these animals
that like to graze on grass.

00:01:00.460 --> 00:01:03.220
So now let's move on to predation.

00:01:03.220 --> 00:01:07.200
Predation is when one
organism eats another organism

00:01:07.200 --> 00:01:09.320
usually to its own benefit.

00:01:09.320 --> 00:01:11.930
Do you see any predation happening here?

00:01:11.930 --> 00:01:13.370
Well, we don't see any of these animals

00:01:13.370 --> 00:01:14.670
chasing and killing each other.

00:01:14.670 --> 00:01:17.250
There might be other
animals like lions offscreen

00:01:17.250 --> 00:01:20.280
that might hunt and kill
and eat these animals

00:01:20.280 --> 00:01:21.350
right over here

00:01:21.350 --> 00:01:23.670
but we know that these
animals do eat grass

00:01:23.670 --> 00:01:26.470
and as I said, it's not just about hunting

00:01:26.470 --> 00:01:29.640
and killing and eating
from one animal to another.

00:01:29.640 --> 00:01:31.480
It could be one organism to another.

00:01:31.480 --> 00:01:33.550
So the eating of the
grass by these animals

00:01:33.550 --> 00:01:36.570
could actually be considered
a form of predation

00:01:36.570 --> 00:01:38.980
especially if it kills the grass.

00:01:38.980 --> 00:01:42.190
A more obvious form of predation
is this brown bear here

00:01:42.190 --> 00:01:45.540
that has gotten the
salmon out of this river.

00:01:45.540 --> 00:01:49.340
It is clearly hunting and killing
the salmon for its benefit

00:01:49.340 --> 00:01:51.090
and it is likely that each of these bears

00:01:51.090 --> 00:01:52.940
are in competition with other bears

00:01:52.940 --> 00:01:55.360
for this limited resource.

00:01:55.360 --> 00:01:56.710
So last but not least,

00:01:56.710 --> 00:01:59.590
let's think a little bit about mutualism.

00:01:59.590 --> 00:02:02.610
Mutualism happens when
two organisms benefit

00:02:02.610 --> 00:02:04.363
from interacting with each other.

00:02:05.200 --> 00:02:07.620
Right over here, we have these starlings

00:02:07.620 --> 00:02:10.020
that actually hang out on this buffalo

00:02:10.020 --> 00:02:13.830
and pick lice and ticks
off the buffalo's fur.

00:02:13.830 --> 00:02:16.337
This is mutualism because
both parties benefit.

00:02:16.337 --> 00:02:18.310
The starlings are able to get food

00:02:18.310 --> 00:02:20.760
and the buffalo no longer
have these parasites,

00:02:20.760 --> 00:02:23.280
these things that are
living off of the buffalo

00:02:23.280 --> 00:02:25.520
sucking its blood out of its body

00:02:25.520 --> 00:02:28.280
and also probably not itching as much.

00:02:28.280 --> 00:02:30.120
Now, based on how I just described it,

00:02:30.120 --> 00:02:32.260
there's not just mutualism here.

00:02:32.260 --> 00:02:33.760
There's also predation

00:02:33.760 --> 00:02:35.980
because these birds are actually hunting

00:02:35.980 --> 00:02:39.750
and killing the lice and the
ticks on the buffalo's body.

00:02:39.750 --> 00:02:41.880
Now, related to being a
predator is another word

00:02:41.880 --> 00:02:43.190
known as being a parasite

00:02:43.190 --> 00:02:45.050
and that's what the lice
and the ticks are doing

00:02:45.050 --> 00:02:47.150
where they're sucking
the blood of the buffalo

00:02:47.150 --> 00:02:48.780
but they're not considered predators.

00:02:48.780 --> 00:02:51.860
They're more parasites because
they don't kill the buffalo.

00:02:51.860 --> 00:02:54.530
They're just taking some
resources away from it.

00:02:54.530 --> 00:02:55.560
So I'll leave you there.

00:02:55.560 --> 00:02:57.130
I encourage you when you look at nature,

00:02:57.130 --> 00:02:58.490
when you go to a park next time,

00:02:58.490 --> 00:03:00.570
when you go watch a documentary,

00:03:00.570 --> 00:03:02.960
I encourage you to think
about how competition,

00:03:02.960 --> 00:03:06.730
predation and mutualism is
happening in an ecosystem

00:03:06.730 --> 00:03:08.980
that you are seeing or
that you're a part of.


Resources and population growth

WEBVTT
Kind: captions
Language: en

00:00:00.350 --> 00:00:02.280
- [Instructor] So we have a
picture here of these animals

00:00:02.280 --> 00:00:03.570
at a watering hole.

00:00:03.570 --> 00:00:07.940
And my question to you is why
don't we see more animals?

00:00:07.940 --> 00:00:10.640
There's clearly enough
space for more animals,

00:00:10.640 --> 00:00:12.470
and we also know that if we focus

00:00:12.470 --> 00:00:15.510
on any one of these
populations, say zebra,

00:00:15.510 --> 00:00:19.960
that every one zebra can have
far more than one offspring

00:00:19.960 --> 00:00:21.020
in their lifetime.

00:00:21.020 --> 00:00:22.540
And that not only that,

00:00:22.540 --> 00:00:24.167
but those offspring can
then have offspring,

00:00:24.167 --> 00:00:25.350
and so on and so forth.

00:00:25.350 --> 00:00:27.050
So it seems like over time,

00:00:27.050 --> 00:00:29.470
these zebra should just be
able to keep multiplying

00:00:29.470 --> 00:00:31.150
until they fill up all of this land,

00:00:31.150 --> 00:00:32.630
similar for the buffalo,

00:00:32.630 --> 00:00:34.310
similar for the antelope.

00:00:34.310 --> 00:00:36.030
Why don't we see that?

00:00:36.030 --> 00:00:38.730
Pause this video and think about that.

00:00:38.730 --> 00:00:42.350
So let's start by thinking
about what any organism,

00:00:42.350 --> 00:00:44.370
or a population of organisms,

00:00:44.370 --> 00:00:47.890
or a community of
populations need to survive.

00:00:47.890 --> 00:00:50.590
Most animals that live on the
surface, like these animals,

00:00:50.590 --> 00:00:52.700
need air, especially oxygen.

00:00:52.700 --> 00:00:54.980
Plants need carbon dioxide from the air.

00:00:54.980 --> 00:00:57.840
They need water.

00:00:57.840 --> 00:01:01.810
They need a source of energy,
which I will call food,

00:01:01.810 --> 00:01:03.840
or I could say it's energy here,

00:01:03.840 --> 00:01:05.610
because it's not always
in the form of food

00:01:05.610 --> 00:01:07.310
as we might recognize it.

00:01:07.310 --> 00:01:09.570
And I guess if we think really basically,

00:01:09.570 --> 00:01:12.400
they need space in which to exist.

00:01:12.400 --> 00:01:13.690
Now, as I mentioned,

00:01:13.690 --> 00:01:16.700
there seems to be a lot of
space here for the animals,

00:01:16.700 --> 00:01:19.080
so that doesn't seem to be the resource

00:01:19.080 --> 00:01:21.880
that is limiting their growth.

00:01:21.880 --> 00:01:24.010
So let's rule that out here.

00:01:24.010 --> 00:01:25.540
Now, it's also clear that
it seems like there's

00:01:25.540 --> 00:01:27.410
a fairly large amount of air here,

00:01:27.410 --> 00:01:30.320
more than enough air for
these populations to grow,

00:01:30.320 --> 00:01:32.590
so that doesn't seem to be a resource

00:01:32.590 --> 00:01:34.970
that's somehow putting
a maximum on how many

00:01:34.970 --> 00:01:36.610
of these organisms there are.

00:01:36.610 --> 00:01:39.450
It does not look like a limited resource,

00:01:39.450 --> 00:01:42.060
or a limiting resource.

00:01:42.060 --> 00:01:43.860
Now, what about water?

00:01:43.860 --> 00:01:45.820
Well, water does seem interesting here,

00:01:45.820 --> 00:01:47.980
because this watering hole does not seem

00:01:47.980 --> 00:01:48.970
like it's very deep.

00:01:48.970 --> 00:01:51.630
It does not seem like
there's a lot of water here.

00:01:51.630 --> 00:01:55.350
So this one could be what we
would call a limited resource

00:01:55.350 --> 00:01:57.180
that is limiting population.

00:01:57.180 --> 00:01:58.970
Maybe if they had more and more offspring,

00:01:58.970 --> 00:02:00.810
there just wouldn't be enough water

00:02:00.810 --> 00:02:02.800
for any member of a population,

00:02:02.800 --> 00:02:04.880
and then of course the
populations would be competing

00:02:04.880 --> 00:02:05.790
with each other as well,

00:02:05.790 --> 00:02:09.170
because they all need
the same water to drink.

00:02:09.170 --> 00:02:10.900
Now, what about food?

00:02:10.900 --> 00:02:13.110
Well, you might recognize that zebra,

00:02:13.110 --> 00:02:15.320
or antelope, or buffalo,

00:02:15.320 --> 00:02:17.070
they tend to graze on grasses,

00:02:17.070 --> 00:02:19.450
and there are some grasses over here,

00:02:19.450 --> 00:02:21.700
but we also see that a
lot of the grass is dead

00:02:21.700 --> 00:02:22.780
or dried out,

00:02:22.780 --> 00:02:25.480
and there's just a lot
of areas with dirt here.

00:02:25.480 --> 00:02:27.710
So it looks like the food and energy

00:02:27.710 --> 00:02:30.739
is also a limiting resource.

00:02:30.739 --> 00:02:32.470
And we have to remind
ourselves there's populations

00:02:32.470 --> 00:02:33.720
of different types of grasses,

00:02:33.720 --> 00:02:35.550
and why aren't they spreading more?

00:02:35.550 --> 00:02:37.030
Well, from the perspective of a plant,

00:02:37.030 --> 00:02:39.630
it looks like the air and
space is for sure abundant,

00:02:39.630 --> 00:02:42.130
and even energy in the form of sunlight

00:02:42.130 --> 00:02:44.120
is abundant based on this picture,

00:02:44.120 --> 00:02:46.840
so it's probably water
is the limited resource,

00:02:46.840 --> 00:02:48.640
which is keeping us
from having more plants

00:02:48.640 --> 00:02:50.790
and grasses in this picture.

00:02:50.790 --> 00:02:53.740
We can imagine a scenario
in which it rains a lot.

00:02:53.740 --> 00:02:56.510
There's a lot of water, water is abundant,

00:02:56.510 --> 00:02:59.680
then all of the different
types of populations of grasses

00:02:59.680 --> 00:03:01.050
are able to expand,

00:03:01.050 --> 00:03:03.650
and then there's more
than enough food and water

00:03:03.650 --> 00:03:06.470
for these animals to keep reproducing.

00:03:06.470 --> 00:03:09.370
In that case, space might become an issue.

00:03:09.370 --> 00:03:11.070
But the important thing to realize here

00:03:11.070 --> 00:03:15.410
is that all organisms need
resources in order to survive

00:03:15.410 --> 00:03:18.160
and in order to multiply and reproduce.

00:03:18.160 --> 00:03:20.670
Populations of many different
species are often competing

00:03:20.670 --> 00:03:21.670
for those resources.

00:03:21.670 --> 00:03:22.950
Like the water here,

00:03:22.950 --> 00:03:24.490
that will tend to put a limit

00:03:24.490 --> 00:03:27.040
on how much these populations can grow.

00:03:27.040 --> 00:03:29.770
And the limit on one
population can affect another.

00:03:29.770 --> 00:03:31.620
As we said, if you had more water,

00:03:31.620 --> 00:03:32.830
you could have more grass,

00:03:32.830 --> 00:03:35.000
which will allow them
for more food and energy

00:03:35.000 --> 00:03:37.083
for these other populations.


Populations, communities, and ecosystems

WEBVTT
Kind: captions
Language: en

00:00:00.170 --> 00:00:01.700
- [Instructor] In biology, it's useful

00:00:01.700 --> 00:00:03.350
to have some shared language

00:00:03.350 --> 00:00:06.500
so we can communicate and
describe the world around us

00:00:06.500 --> 00:00:09.580
in ways that we can all
understand together.

00:00:09.580 --> 00:00:11.650
So here, we're going to
talk about populations,

00:00:11.650 --> 00:00:13.570
communities, and ecosystems.

00:00:13.570 --> 00:00:17.060
And as we will see, these
are all related ideas.

00:00:17.060 --> 00:00:21.420
So first of all, a population
is talking about the members

00:00:21.420 --> 00:00:24.110
of a specific species in an area.

00:00:24.110 --> 00:00:26.710
So for example, in this picture,

00:00:26.710 --> 00:00:29.540
we have a population of zebra.

00:00:29.540 --> 00:00:32.970
I have one zebra there, one zebra there,

00:00:32.970 --> 00:00:35.090
there might be some
others that we can't see.

00:00:35.090 --> 00:00:36.580
In fact, there are likely to be.

00:00:36.580 --> 00:00:40.560
So, these are each members
of a population of zebra.

00:00:40.560 --> 00:00:43.060
Now, we have other
populations in this picture.

00:00:43.060 --> 00:00:45.380
We have a population of buffalo.

00:00:45.380 --> 00:00:48.240
These three are members
of that population.

00:00:48.240 --> 00:00:50.580
We have a population of antelope.

00:00:50.580 --> 00:00:53.420
In fact, there is a bunch
of antelope in this picture.

00:00:53.420 --> 00:00:55.630
So, we have many members
of that population.

00:00:55.630 --> 00:00:58.080
We even see some animals
here in the background.

00:00:58.080 --> 00:01:00.500
I can't quite make out what they are,

00:01:00.500 --> 00:01:02.560
but that could be a different population.

00:01:02.560 --> 00:01:04.010
Let's say if those are elephants,

00:01:04.010 --> 00:01:06.230
they might be elephants
the way I see them,

00:01:06.230 --> 00:01:09.030
but that could be members of
a population of elephants.

00:01:09.030 --> 00:01:13.350
So if that is a population,
what is a community?

00:01:13.350 --> 00:01:16.840
Well, a community is all
of the living species

00:01:16.840 --> 00:01:19.030
that live in the same area.

00:01:19.030 --> 00:01:21.060
So, we have a community of animals

00:01:21.060 --> 00:01:24.770
that is made up of populations of buffalo,

00:01:24.770 --> 00:01:27.770
of zebra, and of antelope.

00:01:27.770 --> 00:01:30.560
And I wanna make clear
that the populations

00:01:30.560 --> 00:01:31.930
or when we're talking
about the communities,

00:01:31.930 --> 00:01:33.550
we're not necessarily just talking

00:01:33.550 --> 00:01:36.050
about large animals like this.

00:01:36.050 --> 00:01:38.940
We could be talking about
populations of mosquitoes.

00:01:38.940 --> 00:01:41.470
We could be talking about
populations of fish in this pond,

00:01:41.470 --> 00:01:42.740
if there are any fish.

00:01:42.740 --> 00:01:45.400
We could have a population of
a certain species of plant.

00:01:45.400 --> 00:01:47.380
And likewise, when we're
talking about communities,

00:01:47.380 --> 00:01:48.330
we're talking about collectively

00:01:48.330 --> 00:01:50.890
all of the living organisms together.

00:01:50.890 --> 00:01:54.560
Now, last but not least, what
would be an ecosystem then?

00:01:54.560 --> 00:01:57.540
Well, an ecosystem is all
of the living organisms

00:01:57.540 --> 00:01:59.870
plus all of the non-living things.

00:01:59.870 --> 00:02:01.920
So, the ecosystem that we see here

00:02:01.920 --> 00:02:03.700
would also include the water,

00:02:03.700 --> 00:02:05.370
it would also include the dirt,

00:02:05.370 --> 00:02:07.370
it would also include the air.

00:02:07.370 --> 00:02:09.930
And organisms like those
that we see right here

00:02:09.930 --> 00:02:12.430
are constantly interacting
with both the living

00:02:12.430 --> 00:02:15.040
and nonliving parts of their environment.

00:02:15.040 --> 00:02:17.560
These interactions are
how organisms get food,

00:02:17.560 --> 00:02:20.070
shelter, water, and warmth.

00:02:20.070 --> 00:02:22.880
These interactions are
how organisms survive

00:02:22.880 --> 00:02:24.420
and produce offspring.

00:02:24.420 --> 00:02:26.070
So, let's get a little bit more practice

00:02:26.070 --> 00:02:30.110
with this idea of populations,
communities, and ecosystems.

00:02:30.110 --> 00:02:32.760
And we will do that by
looking at this picture

00:02:32.760 --> 00:02:34.050
right over here.

00:02:34.050 --> 00:02:36.060
Pause this video and think about

00:02:36.060 --> 00:02:38.073
what are the populations here?

00:02:40.260 --> 00:02:41.700
Well, you might not know the name

00:02:41.700 --> 00:02:43.160
of all these different types of fish,

00:02:43.160 --> 00:02:44.790
but you can see that there's a population

00:02:44.790 --> 00:02:47.870
of this gold-colored fish right over here.

00:02:47.870 --> 00:02:51.910
There's also another population
of this blue-colored fish.

00:02:51.910 --> 00:02:54.130
We could keep looking
for other populations.

00:02:54.130 --> 00:02:58.120
It looks like there's a
population of this silver-colored

00:02:58.120 --> 00:03:01.100
or I guess long-ish silver
fish right over here.

00:03:01.100 --> 00:03:02.740
But once again, it's not just the fish.

00:03:02.740 --> 00:03:04.180
There's a population of coral,

00:03:04.180 --> 00:03:06.140
there's populations of microorganisms

00:03:06.140 --> 00:03:08.210
that we can't see here.

00:03:08.210 --> 00:03:12.050
The community would be all
of these living organisms

00:03:12.050 --> 00:03:13.400
that live close to each other.

00:03:13.400 --> 00:03:15.730
And we'll see, sometimes
they compete with each other,

00:03:15.730 --> 00:03:17.460
sometimes they eat each other,

00:03:17.460 --> 00:03:18.810
but sometimes they help each other,

00:03:18.810 --> 00:03:20.930
Or sometimes they don't matter
that much to each other.

00:03:20.930 --> 00:03:23.640
And we'll study that in a lot more detail.

00:03:23.640 --> 00:03:26.950
And then the ecosystem
includes all of the above

00:03:26.950 --> 00:03:31.950
plus the water, plus the
oxygen that is in the water,

00:03:32.080 --> 00:03:35.650
plus the sand at the bottom of the ocean.

00:03:35.650 --> 00:03:37.000
So, I'll leave you there.

00:03:37.000 --> 00:03:38.750
Hopefully, you now have a sense

00:03:38.750 --> 00:03:40.400
of what biologists are talking about

00:03:40.400 --> 00:03:42.260
when they talk about populations,

00:03:42.260 --> 00:03:44.513
communities, and ecosystems.


Photosynthesis in organisms

WEBVTT
Kind: captions
Language: en

00:00:00.120 --> 00:00:01.440
- [Narrator] Hey, I'm gonna let you in

00:00:01.440 --> 00:00:03.040
on a little secret of mine.

00:00:03.040 --> 00:00:05.200
I love gardening.

00:00:05.200 --> 00:00:07.730
In fact, I have a huge garden with apples,

00:00:07.730 --> 00:00:10.000
blueberries, pumpkins, and tomatoes.

00:00:10.000 --> 00:00:13.630
I give my plants micronutrients,
and maybe some fertilizer.

00:00:13.630 --> 00:00:15.430
But I don't give them food in the same way

00:00:15.430 --> 00:00:19.180
that I would give my dog who
eats multiple times a day.

00:00:19.180 --> 00:00:21.490
With plants, I just put them in the soil,

00:00:21.490 --> 00:00:24.240
water them regularly, and watch them grow.

00:00:24.240 --> 00:00:25.470
How do they do it?

00:00:25.470 --> 00:00:28.140
Well, they use a process
called photosynthesis.

00:00:28.140 --> 00:00:30.790
Photosynthesis is a
scientific term to describe

00:00:30.790 --> 00:00:33.330
how certain living things
use energy from sunlight

00:00:33.330 --> 00:00:34.890
to live and grow.

00:00:34.890 --> 00:00:37.180
Many different kinds of plants, algae,

00:00:37.180 --> 00:00:40.010
and various single-celled
organisms are able to carry out

00:00:40.010 --> 00:00:41.820
this amazing process.

00:00:41.820 --> 00:00:45.090
Today, let's describe
photosynthesis using tomatoes.

00:00:45.090 --> 00:00:46.960
So here you see a young tomato plant,

00:00:46.960 --> 00:00:48.970
similar to the ones I
have in my own garden.

00:00:48.970 --> 00:00:51.290
Let's name it Planty.

00:00:51.290 --> 00:00:52.300
First, let's start off

00:00:52.300 --> 00:00:54.780
by looking at Planty's
immediate surroundings.

00:00:54.780 --> 00:00:57.270
The soil Planty is
growing in contains water

00:00:57.270 --> 00:01:00.120
and the air surrounding
Planty contains molecules

00:01:00.120 --> 00:01:01.590
of carbon dioxide.

00:01:01.590 --> 00:01:04.760
These two compounds are the
starting materials or inputs

00:01:04.760 --> 00:01:08.100
that Planty needs in order
to carry out photosynthesis.

00:01:08.100 --> 00:01:10.330
Now, let's take a look
at the weather forecast.

00:01:10.330 --> 00:01:12.650
Well, it looks like it's
gonna be a sunny day today.

00:01:12.650 --> 00:01:14.260
So when the sun shines on the earth,

00:01:14.260 --> 00:01:16.620
it sends out energy in the form of light.

00:01:16.620 --> 00:01:18.620
This energy is essential for Planty

00:01:18.620 --> 00:01:20.900
to be able to carry out photosynthesis.

00:01:20.900 --> 00:01:23.020
Next, let's take a closer look at Planty,

00:01:23.020 --> 00:01:26.060
because Planty's cells are
hiding a secret of their own.

00:01:26.060 --> 00:01:28.810
Inside Planty's cells are
microscopic structures

00:01:28.810 --> 00:01:31.180
that help Planty carry out photosynthesis.

00:01:31.180 --> 00:01:33.690
These structures are called chloroplasts.

00:01:33.690 --> 00:01:36.330
Chloroplasts contain
green pigment molecules

00:01:36.330 --> 00:01:37.600
called chlorophyll.

00:01:37.600 --> 00:01:39.580
It is actually within these molecules

00:01:39.580 --> 00:01:41.880
that the sun's energy is captured for use

00:01:41.880 --> 00:01:43.310
during photosynthesis.

00:01:43.310 --> 00:01:45.560
Interestingly, chlorophyll
is where leaves get

00:01:45.560 --> 00:01:46.730
their green color.

00:01:46.730 --> 00:01:49.270
To help you remember, think
of chlorophyll like this:

00:01:49.270 --> 00:01:52.550
chloro means green and phyll means leaf.

00:01:52.550 --> 00:01:55.600
So when you put them
together, you get green leaf.

00:01:55.600 --> 00:01:58.760
Okay, so now we know that
carbon dioxide, water,

00:01:58.760 --> 00:02:01.880
and sunlight are required
for photosynthesis to occur.

00:02:01.880 --> 00:02:04.310
And we know that in plants like Planty,

00:02:04.310 --> 00:02:06.740
photosynthesis happens in the chloroplast

00:02:06.740 --> 00:02:08.580
with the help of chlorophyll.

00:02:08.580 --> 00:02:10.580
Next, let's take a look at what happens

00:02:10.580 --> 00:02:13.370
during the process of
photosynthesis itself.

00:02:13.370 --> 00:02:15.670
When the sunlight reaches
Planty's chloroplast,

00:02:15.670 --> 00:02:18.190
its energy is used to rearrange the atoms

00:02:18.190 --> 00:02:20.810
in the carbon dioxide and water molecules

00:02:20.810 --> 00:02:23.080
through a series of chemical reactions.

00:02:23.080 --> 00:02:24.670
The outputs of these reactions

00:02:24.670 --> 00:02:27.310
are oxygen molecules and sugars.

00:02:27.310 --> 00:02:30.030
These sugars are vital
to Planty's survival

00:02:30.030 --> 00:02:32.690
because they are used as a
source of chemical energy

00:02:32.690 --> 00:02:34.800
that helps Planty live and grow.

00:02:34.800 --> 00:02:37.050
In other words, they're Planty's food.

00:02:37.050 --> 00:02:38.280
Planty can do a few things

00:02:38.280 --> 00:02:40.790
with the sugars made
during photosynthesis.

00:02:40.790 --> 00:02:42.000
It can break the sugars down

00:02:42.000 --> 00:02:44.200
to get usable energy right away,

00:02:44.200 --> 00:02:47.210
or it can store the sugar
molecules for later use.

00:02:47.210 --> 00:02:49.310
If Planty stores the sugar molecules,

00:02:49.310 --> 00:02:52.140
it can then use them as a
source of energy in the future.

00:02:52.140 --> 00:02:53.830
This means that Planty can grow

00:02:53.830 --> 00:02:55.900
even when the sun isn't shining.

00:02:55.900 --> 00:02:58.170
Planty can also use the sugar molecules

00:02:58.170 --> 00:03:00.750
to build larger molecules
such as cellulose

00:03:00.750 --> 00:03:03.230
that make up the structure
of Planty itself.

00:03:03.230 --> 00:03:06.240
In this way, Planty can
grow bigger and bigger

00:03:06.240 --> 00:03:08.350
with very little help from me;

00:03:08.350 --> 00:03:11.130
all thanks to the process
of photosynthesis.

00:03:11.130 --> 00:03:13.370
Planty's other output, oxygen,

00:03:13.370 --> 00:03:15.310
is released into the atmosphere.

00:03:15.310 --> 00:03:18.390
This is really cool because
it provides organisms

00:03:18.390 --> 00:03:22.060
in the ecosystem,
including us, with oxygen.

00:03:22.060 --> 00:03:25.330
So thanks Planty and other
photosynthetic organisms

00:03:25.330 --> 00:03:28.130
for giving us the oxygen
we need to breathe.

00:03:28.130 --> 00:03:31.000
And that, my friends, is photosynthesis.

00:03:31.000 --> 00:03:32.350
So next time you're in a garden,

00:03:32.350 --> 00:03:33.830
I want you to think about this.

00:03:33.830 --> 00:03:37.480
All the plant structures you
can see, such as stems, leaves,

00:03:37.480 --> 00:03:39.560
and even the fruits and
vegetables that we eat

00:03:39.560 --> 00:03:42.100
are made up mostly of the
atoms that were once a part

00:03:42.100 --> 00:03:44.740
of the starting materials
of photosynthesis.

00:03:44.740 --> 00:03:46.490
With the help of a little sunlight,

00:03:46.490 --> 00:03:49.410
the plants made their
own food and grew bigger,

00:03:49.410 --> 00:03:51.380
taking CO2 out of the atmosphere

00:03:51.380 --> 00:03:54.560
and releasing oxygen back
in for us to breathe.

00:03:54.560 --> 00:03:57.140
And on that note, I
think I should go outside

00:03:57.140 --> 00:03:59.200
and give my own garden some water.

00:03:59.200 --> 00:04:00.053
See you later.


Plant reproductive success

WEBVTT
Kind: captions
Language: en

00:00:00.380 --> 00:00:01.270
- [Instructor] We've already talked

00:00:01.270 --> 00:00:04.280
about reproductive
success in other videos.

00:00:04.280 --> 00:00:07.240
It's related to the number of offspring

00:00:07.240 --> 00:00:10.180
an organism can have in its lifetime.

00:00:10.180 --> 00:00:11.630
And so in this video,

00:00:11.630 --> 00:00:14.030
we're going to think about strategies

00:00:14.030 --> 00:00:18.000
that plants will use for
reproductive success.

00:00:18.000 --> 00:00:21.170
A plant that has more surviving offspring

00:00:21.170 --> 00:00:24.640
has a higher reproductive success.

00:00:24.640 --> 00:00:26.970
So one major strategy that plants use

00:00:26.970 --> 00:00:30.540
to increase their chances of reproduction

00:00:30.540 --> 00:00:34.680
is by leveraging animals for pollination.

00:00:34.680 --> 00:00:36.640
You have seen pollination.

00:00:36.640 --> 00:00:38.840
This is a picture of
a bee gathering nectar

00:00:38.840 --> 00:00:42.210
from this flower, but as
it gathers that nectar,

00:00:42.210 --> 00:00:44.630
pollen also gets attached to that bee.

00:00:44.630 --> 00:00:47.500
So as that bee goes from flower to flower,

00:00:47.500 --> 00:00:50.460
from plant to plant,
it's able to pollinate,

00:00:50.460 --> 00:00:52.920
it's able to take pollen from one plant

00:00:52.920 --> 00:00:54.660
and give it to another plant,

00:00:54.660 --> 00:00:57.740
allowing for that genetic mixing to occur

00:00:57.740 --> 00:01:01.410
and also to then have
more plant reproduction.

00:01:01.410 --> 00:01:04.340
Now, once a plant is able to reproduce,

00:01:04.340 --> 00:01:06.440
we also need to think about how viable

00:01:06.440 --> 00:01:08.320
its offspring are going to be.

00:01:08.320 --> 00:01:10.700
Are they in conditions
where they are likely

00:01:10.700 --> 00:01:14.890
to succeed in living and
then reproducing themselves?

00:01:14.890 --> 00:01:17.130
And here, a common strategy,

00:01:17.130 --> 00:01:20.350
or at least a category of
strategies that plants use

00:01:20.350 --> 00:01:24.380
are known as seed dispersal.

00:01:24.380 --> 00:01:27.130
And it's really just
trying to get the seeds

00:01:27.130 --> 00:01:28.910
in as many places as possible,

00:01:28.910 --> 00:01:32.030
potentially far away
from the plant itself,

00:01:32.030 --> 00:01:34.290
to increase the chances
that more of the seeds

00:01:34.290 --> 00:01:36.800
are going to be in places
that are nutrient rich,

00:01:36.800 --> 00:01:38.600
where they can survive.

00:01:38.600 --> 00:01:41.800
And once again, you have likely seen this.

00:01:41.800 --> 00:01:45.880
This is a dandelion plant
and when a strong wind blows,

00:01:45.880 --> 00:01:48.210
these dandelion seeds catch the wind

00:01:48.210 --> 00:01:49.210
because they have these structures

00:01:49.210 --> 00:01:51.120
which are not that aerodynamic,

00:01:51.120 --> 00:01:54.300
which pull the seeds along
and can transport them

00:01:54.300 --> 00:01:56.440
for even miles and miles.

00:01:56.440 --> 00:01:59.280
Many of these seeds aren't going
to end up in useful places,

00:01:59.280 --> 00:02:00.650
but some of them might,

00:02:00.650 --> 00:02:02.600
and they might be in places where

00:02:02.600 --> 00:02:06.070
the future dandelion offspring
are more likely to survive

00:02:06.070 --> 00:02:08.435
and then reproduce themselves.

00:02:08.435 --> 00:02:11.593
But seed dispersal also
gets the help of animals.

00:02:12.490 --> 00:02:15.000
This right over here
is a picture of a bird

00:02:15.000 --> 00:02:16.840
eating fruit from a plant.

00:02:16.840 --> 00:02:20.190
And as that bird flies away
and munches on that fruit,

00:02:20.190 --> 00:02:22.060
that seed might be dispersed,

00:02:22.060 --> 00:02:25.330
it might be thrown down hundreds of yards

00:02:25.330 --> 00:02:28.100
or even miles away from
the original plant.

00:02:28.100 --> 00:02:30.380
In many cases, you might eat a fruit,

00:02:30.380 --> 00:02:32.880
and I am saying you, because
we do this ourselves.

00:02:32.880 --> 00:02:35.610
You might eat, say, a
watermelon or a papaya

00:02:35.610 --> 00:02:38.430
and a couple of seeds go
down while you ate it.

00:02:38.430 --> 00:02:41.130
And then later on, you
or some other animal

00:02:41.130 --> 00:02:44.470
might poop it someplace where
it might be a good place

00:02:44.470 --> 00:02:48.560
for that watermelon plant or
that papaya plant to grow.

00:02:48.560 --> 00:02:49.770
So this was just an overview

00:02:49.770 --> 00:02:52.430
of some of the strategies that plants use,

00:02:52.430 --> 00:02:55.400
but it's important to realize
that throughout nature,

00:02:55.400 --> 00:02:58.940
we see this idea of reproductive success

00:02:58.940 --> 00:03:01.880
over and over again, and
in animals' behaviors

00:03:01.880 --> 00:03:04.080
or strategies for reproductive success,

00:03:04.080 --> 00:03:09.080
and here we saw plants' strategies
for reproductive success.


Animal behavior and offspring success

WEBVTT
Kind: captions
Language: en

00:00:00.500 --> 00:00:04.500
- Let's talk a little bit
about reproductive success,

00:00:04.500 --> 00:00:08.415
which is related to the
number of surviving offspring

00:00:08.415 --> 00:00:11.670
that an animal has during its lifetime.

00:00:11.670 --> 00:00:14.690
An animal that has more
surviving offspring

00:00:14.690 --> 00:00:17.378
has a higher reproductive success.

00:00:17.378 --> 00:00:19.781
Now, there's two broad categories

00:00:19.781 --> 00:00:21.905
of traits or behaviors

00:00:21.905 --> 00:00:24.990
that might drive reproductive success.

00:00:24.990 --> 00:00:28.350
One might be behaviors
that increase the chances

00:00:28.350 --> 00:00:30.970
of an animal producing offspring.

00:00:30.970 --> 00:00:33.060
And we know that most
animals that we study,

00:00:33.060 --> 00:00:37.010
not all, but most, reproduce
via sexual reproduction.

00:00:37.010 --> 00:00:37.860
To do that,

00:00:37.860 --> 00:00:41.300
they need to mate with an
individual of the opposite sex.

00:00:41.300 --> 00:00:44.379
And that's why you see
things like peacocks,

00:00:44.379 --> 00:00:48.070
where these very elaborate
feathers are a way

00:00:48.070 --> 00:00:51.130
of signaling to members
of the opposite sex,

00:00:51.130 --> 00:00:55.760
the peahens, that this peacock
here has favorable traits,

00:00:55.760 --> 00:00:59.200
is attractive to the
peahen, has good health,

00:00:59.200 --> 00:01:00.980
which signals to the peahen

00:01:00.980 --> 00:01:02.750
that by reproducing with this peacock,

00:01:02.750 --> 00:01:06.180
they're more likely to
have reproductive success.

00:01:06.180 --> 00:01:07.390
They'll have healthier offspring,

00:01:07.390 --> 00:01:09.450
which are more likely to survive,

00:01:09.450 --> 00:01:12.340
which are more likely to
then go on and reproduce.

00:01:12.340 --> 00:01:14.790
And then assuming that
animals are able to mate

00:01:14.790 --> 00:01:16.166
and able to reproduce,

00:01:16.166 --> 00:01:19.358
another behavior that you
will see amongst animals

00:01:19.358 --> 00:01:21.420
that will increase the chances

00:01:21.420 --> 00:01:22.765
that their offspring will survive,

00:01:22.765 --> 00:01:25.029
and then be able to reproduce themselves

00:01:25.029 --> 00:01:27.350
is parental care,

00:01:27.350 --> 00:01:30.695
or behaviors that protect
offspring from predators.

00:01:30.695 --> 00:01:33.640
You see that throughout
the animal kingdom.

00:01:33.640 --> 00:01:36.330
Here are some emperor penguins taking care

00:01:36.330 --> 00:01:39.110
of their young baby penguin.

00:01:39.110 --> 00:01:42.540
Here is a mother grizzly bear
taking care of her bears.

00:01:42.540 --> 00:01:46.320
And here the parental care
might be helping them find food,

00:01:46.320 --> 00:01:48.660
giving them food, training them,

00:01:48.660 --> 00:01:50.780
protecting them from other predators

00:01:50.780 --> 00:01:52.510
or from competitors in some way.

00:01:52.510 --> 00:01:54.970
And this isn't just amongst
bears, and penguins,

00:01:54.970 --> 00:01:56.990
and potentially peacocks and peahens.

00:01:56.990 --> 00:01:59.780
It's all in service to,
at least in some level,

00:01:59.780 --> 00:02:01.833
reproductive success.


Earth's changing climate

WEBVTT
Kind: captions
Language: en

00:00:00.000 --> 00:00:01.250
- [Narrator] Have you
ever tried to imagine

00:00:01.250 --> 00:00:03.760
what the world was like
in the distant past?

00:00:03.760 --> 00:00:06.390
Maybe you'd like to explore
the age of the dinosaurs

00:00:06.390 --> 00:00:08.790
when the earth was much
hotter than it was today.

00:00:08.790 --> 00:00:09.850
Perhaps you'd prefer

00:00:09.850 --> 00:00:12.340
when temperatures dropped
too much colder than today.

00:00:12.340 --> 00:00:14.900
You could track a mammoth
alongside our early ancestors

00:00:14.900 --> 00:00:17.740
who evolved around the
end of the last ice age.

00:00:17.740 --> 00:00:19.730
We know about all of these
ancient climate trends

00:00:19.730 --> 00:00:20.760
because scientists learned

00:00:20.760 --> 00:00:23.290
how to estimate them using
evidence from ice cores,

00:00:23.290 --> 00:00:25.363
tree rings, and other natural phenomena.

00:00:26.230 --> 00:00:28.050
We now know that for
most of human history,

00:00:28.050 --> 00:00:29.190
people could expect a pattern

00:00:29.190 --> 00:00:30.500
that looks something like this graph

00:00:30.500 --> 00:00:33.160
from the National Aeronautics
and Space Administration

00:00:33.160 --> 00:00:35.330
which shows how temperatures
changed each year

00:00:35.330 --> 00:00:37.120
in comparison to this line,

00:00:37.120 --> 00:00:39.500
which represents the average
global annual temperature

00:00:39.500 --> 00:00:42.300
from 1880 to 1899.

00:00:42.300 --> 00:00:45.210
When we look at the time
period between 1880 and 1940,

00:00:45.210 --> 00:00:47.450
we can see that some years
temperatures would be higher

00:00:47.450 --> 00:00:49.770
than this average, some
years they would be lower,

00:00:49.770 --> 00:00:51.130
but they generally swing back

00:00:51.130 --> 00:00:53.080
to a pretty comfortable state.

00:00:53.080 --> 00:00:54.450
Around the 1950s, though,

00:00:54.450 --> 00:00:56.060
the global average
temperature began to climb

00:00:56.060 --> 00:00:57.850
to unprecedented levels.

00:00:57.850 --> 00:00:59.820
Our ancient temperature
records never showed

00:00:59.820 --> 00:01:01.680
such a sudden increase.

00:01:01.680 --> 00:01:04.220
When we look at the time
period from 1950 to today,

00:01:04.220 --> 00:01:05.560
we can see that while temperatures

00:01:05.560 --> 00:01:07.120
still swing back down some years,

00:01:07.120 --> 00:01:08.960
these colder years are still much hotter

00:01:08.960 --> 00:01:11.320
than the average temperatures in the past.

00:01:11.320 --> 00:01:13.700
Researchers noticed a
change in the concentration

00:01:13.700 --> 00:01:16.120
of greenhouse gases in
the Earth's atmosphere.

00:01:16.120 --> 00:01:17.760
These greenhouse gases trap heat

00:01:17.760 --> 00:01:19.140
from the sun in our atmosphere,

00:01:19.140 --> 00:01:21.480
similar to how a
greenhouse allows sunlight

00:01:21.480 --> 00:01:22.830
to pass through its glass walls

00:01:22.830 --> 00:01:25.490
but prevents the heat
it creates from leaving.

00:01:25.490 --> 00:01:27.800
This greenhouse effect is
what keeps our planet warm

00:01:27.800 --> 00:01:29.430
and habitable enough for life.

00:01:29.430 --> 00:01:31.920
However, the amount of one
particular greenhouse gas

00:01:31.920 --> 00:01:34.960
was rising, carbon dioxide or CO2.

00:01:34.960 --> 00:01:37.880
CO2 is naturally one of the
most notable greenhouse gases

00:01:37.880 --> 00:01:38.970
besides water vapor,

00:01:38.970 --> 00:01:41.620
but we can also release
CO2 by burning wood

00:01:41.620 --> 00:01:43.760
or fossil fuels like coal and oil.

00:01:43.760 --> 00:01:46.390
Over time, humans have
increasingly relied on these fuels

00:01:46.390 --> 00:01:48.900
to power things like
planes, cars, and trains

00:01:48.900 --> 00:01:51.200
as well as to generate electricity.

00:01:51.200 --> 00:01:52.740
As a result of these human activities,

00:01:52.740 --> 00:01:55.040
more CO2 is being released
into the atmosphere

00:01:55.040 --> 00:01:56.280
than ever before,

00:01:56.280 --> 00:01:58.370
much more than is normally
released by the Earth

00:01:58.370 --> 00:02:00.210
and at a much faster rate.

00:02:00.210 --> 00:02:02.460
The increasingly heavy
blanket of greenhouse gases

00:02:02.460 --> 00:02:04.240
is trapping excess heat in our atmosphere

00:02:04.240 --> 00:02:05.510
rather than allowing more of it

00:02:05.510 --> 00:02:07.430
to radiate into space as normal.

00:02:07.430 --> 00:02:09.900
This is what's causing
Earth's average temperature

00:02:09.900 --> 00:02:11.650
to rise beyond what
scientists would expect

00:02:11.650 --> 00:02:13.690
based on historical patterns.

00:02:13.690 --> 00:02:14.880
While scientists once referred

00:02:14.880 --> 00:02:16.510
to this process as global warming,

00:02:16.510 --> 00:02:19.910
most now prefer the more
general term, climate change.

00:02:19.910 --> 00:02:21.930
A world that's a little
bit warmer on average

00:02:21.930 --> 00:02:23.530
might not seem like such a big deal,

00:02:23.530 --> 00:02:25.340
but we've learned that even a small shift

00:02:25.340 --> 00:02:26.740
in the planet's natural processes

00:02:26.740 --> 00:02:29.360
can have drastic consequences.

00:02:29.360 --> 00:02:31.320
When studying the early
signs of climate change,

00:02:31.320 --> 00:02:33.190
scientists predicted that as cold places

00:02:33.190 --> 00:02:35.010
like North and South Pole got warmer,

00:02:35.010 --> 00:02:36.600
the ice would begin to melt.

00:02:36.600 --> 00:02:39.110
All of that frozen water
suddenly flowing into the oceans

00:02:39.110 --> 00:02:40.460
would cause sea levels to rise,

00:02:40.460 --> 00:02:43.340
which would affect the
planet's weather system.

00:02:43.340 --> 00:02:45.070
Have you heard all the
news about weird weather

00:02:45.070 --> 00:02:46.410
in the past few years?

00:02:46.410 --> 00:02:49.020
Snow in places that's
usually warm and dry,

00:02:49.020 --> 00:02:52.060
or drought in places that
are usually cold and rainy,

00:02:52.060 --> 00:02:54.860
huge fires during extremely hot summers,

00:02:54.860 --> 00:02:58.570
severe storms battering
coastlines and flooding cities.

00:02:58.570 --> 00:03:00.770
Many of these natural hazards
used to be somewhat rare,

00:03:00.770 --> 00:03:02.480
but now they're becoming more common,

00:03:02.480 --> 00:03:05.020
exactly as climate scientists predicted.

00:03:05.020 --> 00:03:07.440
People have relied on relatively
consistent weather patterns

00:03:07.440 --> 00:03:08.350
for generations,

00:03:08.350 --> 00:03:09.730
so they aren't prepared to adapt

00:03:09.730 --> 00:03:11.870
to these changes in
their local environment.

00:03:11.870 --> 00:03:13.560
Communities that are
already feeling the effects

00:03:13.560 --> 00:03:14.930
of climate change are worried

00:03:14.930 --> 00:03:16.130
that they're gonna lose their homes,

00:03:16.130 --> 00:03:19.193
their livelihoods, or their
sources of food and water.

00:03:20.500 --> 00:03:21.940
Scientists are working on technologies

00:03:21.940 --> 00:03:23.820
that can help us remove
some of the excess CO2

00:03:23.820 --> 00:03:24.710
from the atmosphere,

00:03:24.710 --> 00:03:27.470
but in the meantime they
recommend that we emit less CO2

00:03:27.470 --> 00:03:28.650
in the first place.

00:03:28.650 --> 00:03:29.790
This would allow us to limit

00:03:29.790 --> 00:03:31.780
how much the global average
temperature increases,

00:03:31.780 --> 00:03:33.200
giving communities time to adapt

00:03:33.200 --> 00:03:35.170
to changes in their surroundings.

00:03:35.170 --> 00:03:36.520
Of course, it's complicated

00:03:36.520 --> 00:03:38.570
to change the way our societies work.

00:03:38.570 --> 00:03:40.140
To help reduce CO2 emissions,

00:03:40.140 --> 00:03:41.610
you may see some people advocating

00:03:41.610 --> 00:03:43.210
for tweaking individual behaviors,

00:03:43.210 --> 00:03:44.670
like eating plant-based diets

00:03:44.670 --> 00:03:47.420
or using low carbon
transportation methods.

00:03:47.420 --> 00:03:49.810
You may see others saying
that since large organizations

00:03:49.810 --> 00:03:52.230
in highly populated
countries emit the most CO2,

00:03:52.230 --> 00:03:53.160
we need to push them

00:03:53.160 --> 00:03:56.050
to make more wide raging
institutional changes.

00:03:56.050 --> 00:03:57.750
As someone who works in
environmental science,

00:03:57.750 --> 00:03:59.880
I know that sorting through
all of these different facts

00:03:59.880 --> 00:04:03.170
and opinions on climate
change can be overwhelming.

00:04:03.170 --> 00:04:04.990
It's difficult to think
about living in a world

00:04:04.990 --> 00:04:06.140
that may be very different

00:04:06.140 --> 00:04:08.210
from what I've always known in the past.

00:04:08.210 --> 00:04:09.250
I've found it helpful

00:04:09.250 --> 00:04:12.030
to both adopt simple sustainable
habits in my own life,

00:04:12.030 --> 00:04:13.820
while also seeking out community groups

00:04:13.820 --> 00:04:15.490
that work on bigger initiatives.

00:04:15.490 --> 00:04:17.100
It's easier to imagine the future

00:04:17.100 --> 00:04:19.510
when you help others to shape it.

00:04:19.510 --> 00:04:21.950
Now that we've taken some time
to think about Earth's past

00:04:21.950 --> 00:04:23.880
and what's happening to it in the present,

00:04:23.880 --> 00:04:26.150
try looking towards the
future of our planet.

00:04:26.150 --> 00:04:27.850
What is your ideal future?

00:04:27.850 --> 00:04:29.800
And how can you help to make it happen?


Weathering and erosion

WEBVTT
Kind: captions
Language: en

00:00:00.380 --> 00:00:02.250
- [Instructor] Growing
up in Southern Idaho,

00:00:02.250 --> 00:00:05.450
one of my favorite places
to visit was Swan Falls,

00:00:05.450 --> 00:00:08.710
a gorgeous canyon formed
by the snake river.

00:00:08.710 --> 00:00:11.400
All throughout my childhood,
I remember scrambling

00:00:11.400 --> 00:00:13.430
over the boulders down in this canyon

00:00:13.430 --> 00:00:16.560
and playing in the cool water
at the edge of the river.

00:00:16.560 --> 00:00:18.800
Over thousands and thousands of years,

00:00:18.800 --> 00:00:21.690
water slowly eroded
away rock and sediment.

00:00:21.690 --> 00:00:26.660
Water made this canyon and
water forms many landscapes,

00:00:26.660 --> 00:00:30.900
including valleys, ravines,
cliffs, coastlines,

00:00:30.900 --> 00:00:34.940
all of these were largely
shaped and affected by water.

00:00:34.940 --> 00:00:37.670
And given that water
covers most of the earth,

00:00:37.670 --> 00:00:39.990
or over 70% of it,

00:00:39.990 --> 00:00:43.430
it's no surprise that water
also shapes the earth.

00:00:43.430 --> 00:00:45.310
Water is a powerful force.

00:00:45.310 --> 00:00:47.390
It can literally wash away soil

00:00:47.390 --> 00:00:49.900
and carve away rock bit by bit,

00:00:49.900 --> 00:00:53.570
which scientists describe
through two separate processes.

00:00:53.570 --> 00:00:57.490
When water breaks rocks
apart, it's called weathering.

00:00:57.490 --> 00:01:00.830
And when water carries away
surface soil, sediments,

00:01:00.830 --> 00:01:03.683
and that broken down
rock it's called erosion.

00:01:04.810 --> 00:01:07.550
Erosion by water starts with rain.

00:01:07.550 --> 00:01:09.320
During a rain storm the impact

00:01:09.320 --> 00:01:11.710
of raindrops is actually powerful enough

00:01:11.710 --> 00:01:15.730
to dislodge soil particles
and damage soil structure.

00:01:15.730 --> 00:01:18.380
This is called mechanical weathering.

00:01:18.380 --> 00:01:20.460
As rainwater starts to accumulate,

00:01:20.460 --> 00:01:22.640
it can erode a landscape by moving soil

00:01:22.640 --> 00:01:24.880
and rock particles, called sediment,

00:01:24.880 --> 00:01:27.480
away from their original location.

00:01:27.480 --> 00:01:31.280
And as water flows down the
slope of hills and mountains,

00:01:31.280 --> 00:01:34.180
it transports sediment along with it.

00:01:34.180 --> 00:01:36.750
Eventually water gathers
into small streams

00:01:36.750 --> 00:01:40.460
and then rivers, carrying
more and more sediment.

00:01:40.460 --> 00:01:44.320
In fact, through erosion,
water carries away billions

00:01:44.320 --> 00:01:47.540
of tons of sediment to
the oceans every year.

00:01:47.540 --> 00:01:50.590
Plant roots and vegetation
can hold soil in place

00:01:50.590 --> 00:01:53.190
and prevent or slow soil erosion.

00:01:53.190 --> 00:01:56.000
But if soil has nothing to hold it down,

00:01:56.000 --> 00:01:58.643
water can erode away soil very quickly.

00:02:00.460 --> 00:02:02.710
As the volume of water increases,

00:02:02.710 --> 00:02:05.290
so does its power of erosion.

00:02:05.290 --> 00:02:08.320
In turn, a large river can erode more soil

00:02:08.320 --> 00:02:11.320
and rock quicker than a small river can.

00:02:11.320 --> 00:02:13.050
The speed of the water flow

00:02:13.050 --> 00:02:15.630
also affects its erosional power.

00:02:15.630 --> 00:02:19.900
Simply put, faster moving
water can carry more sediment.

00:02:19.900 --> 00:02:22.940
This relationship is one
reason why fast moving water

00:02:22.940 --> 00:02:25.500
causes more erosion than the same volume

00:02:25.500 --> 00:02:27.460
of slow moving water.

00:02:27.460 --> 00:02:31.190
A great example of water
erosion in relation to speed

00:02:31.190 --> 00:02:34.330
is that of meandering
rivers and Oxbow lakes.

00:02:34.330 --> 00:02:38.130
You know, the weird horseshoe
looking lake in this image.

00:02:38.130 --> 00:02:41.310
Let's take a look at how
these Oxbow lakes form.

00:02:41.310 --> 00:02:43.560
The current of the water is fastest

00:02:43.560 --> 00:02:45.730
on the outside of the bend.

00:02:45.730 --> 00:02:48.410
In turn, these are the
areas where water tends

00:02:48.410 --> 00:02:50.630
to erode away the river bank.

00:02:50.630 --> 00:02:53.680
Conversely, the current
of the water is slowest

00:02:53.680 --> 00:02:55.510
on the inside of a bend.

00:02:55.510 --> 00:02:58.600
Here, the water slows
down so much that some

00:02:58.600 --> 00:03:01.370
of the sediment that is
being carried is dropped,

00:03:01.370 --> 00:03:02.920
or deposited.

00:03:02.920 --> 00:03:04.863
This is called sedimentation.

00:03:05.740 --> 00:03:08.200
Over time, through erosion and deposition,

00:03:08.200 --> 00:03:09.900
an Oxbow lake will form,

00:03:09.900 --> 00:03:12.050
which is eventually
cut off from the river.

00:03:13.330 --> 00:03:15.070
Chemical weathering as another way

00:03:15.070 --> 00:03:16.990
that water can break rocks,

00:03:16.990 --> 00:03:19.720
such as when acids in water
dissolve certain types

00:03:19.720 --> 00:03:21.300
of rocks and minerals.

00:03:21.300 --> 00:03:24.040
Over time, flowing water
can dissolve the minerals

00:03:24.040 --> 00:03:27.020
and rocks on or under the surface.

00:03:27.020 --> 00:03:29.470
This chemical weathering
can cause sinkholes,

00:03:29.470 --> 00:03:31.630
caves, and cliffs to form.

00:03:31.630 --> 00:03:33.540
Certain rocks like limestone

00:03:33.540 --> 00:03:36.430
are especially vulnerable to erosion.

00:03:36.430 --> 00:03:39.280
In particular, limestone easily erodes due

00:03:39.280 --> 00:03:41.280
to carbonic acid and rainwater,

00:03:41.280 --> 00:03:44.530
which forms when carbon dioxide, or CO2,

00:03:44.530 --> 00:03:46.980
from the atmosphere dissolves in water.

00:03:46.980 --> 00:03:49.250
In turn limestone erosion can produce

00:03:49.250 --> 00:03:50.933
intricate cave systems.

00:03:53.050 --> 00:03:55.030
Along beaches and the ocean front,

00:03:55.030 --> 00:03:58.140
coastal erosion breaks
up and wears away rock.

00:03:58.140 --> 00:04:00.450
As waves sweep in over and over,

00:04:00.450 --> 00:04:03.103
they cause rock to weather
away and break off.

00:04:05.970 --> 00:04:08.570
Going back to the Snake
River and Swan Falls,

00:04:08.570 --> 00:04:12.089
I can see examples of weathering
and erosion all around me.

00:04:12.089 --> 00:04:15.090
I look to the cliffs which
have been slowly carved away

00:04:15.090 --> 00:04:18.920
by the Snake River over time
to reveal this amazing valley,

00:04:18.920 --> 00:04:22.460
which was formed by
weathering and water erosion.

00:04:22.460 --> 00:04:24.930
Water erosion is incredibly powerful

00:04:24.930 --> 00:04:28.380
and although it can be
destructive by removing soil

00:04:28.380 --> 00:04:31.630
and rock over thousands
and thousands of years,

00:04:31.630 --> 00:04:33.480
water erosion is also responsible

00:04:33.480 --> 00:04:34.820
for creating the beautiful

00:04:34.820 --> 00:04:37.643
and spectacular landscapes
that we enjoy today.