What do nephrons filter?
Options:
- (A) Blood
- (B) matter
- (C) solutes
- (D) Energy
- (E) SO2
- (F) Gases
- (G) Energy.
- (H) cations
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Let's think first: Nephrons are the structural and functional units of the kidneys. Blood is filtered in the kidney. Nephrons filter blood.... So the answer is [(A)]


What does the substance that male dogs have in urine to mark their territory do?
Options:
- (A) sweating
- (B) attract females
- (C) Release energy
- (D) repels females
- (E) attract enemies
- (F) attract males
- (G) adding heat
- (H) dangerous
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Let's think first: Male dogs use pheromones in urine to mark their territory. Males produce 'pheromones' to attract females. Male dogs use something that attracts females in urine to mark their territory.... So the answer is [(B)]


What is important in preventing heat loss from the body?
Options:
- (A) hydration
- (B) a cuticle
- (C) stay warm
- (D) sweating
- (E) warmth
- (F) skin
- (G) keratin
- (H) Animal fur
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Let's think first: Head hair is especially important in preventing heat loss from the body. Hair is actually composed of a protein called keratin. Keratin is especially important in preventing heat loss from the body.... So the answer is [(G)]


An animal which may have one or two hearts to pump blood is:
Options:
- (A) squid
- (B) goats
- (C) bats
- (D) mammals
- (E) toads
- (F) Birds
- (G) edible
- (H) a fish
--
Let's think first: Mollusks have a circulatory system with one or two hearts that pump blood. Interestingly, a squid is also a mollusk. Squid have a circulatory system with one or two hearts that pump blood.... So the answer is [(A)]


What do echinoderms lack?
Options:
- (A) Lungs
- (B) Mass
- (C) oxygen
- (D) eardrum
- (E) gills
- (F) ovaries
- (G) Organs
- (H) Bodies
--
Let's think first: Echinoderms lack respiratory and excretory systems. Lung mechanics and gas exchange are topics during study of the respiratory system. Echinoderms have no lungs.... So the answer is [(A)]


What is a major food source for other organisms, including humans?
Options:
- (A) gastropod shells
- (B) orchids
- (C) invertebrates
- (D) swamp vegetation
- (E) Most plants
- (F) insects
- (G) barnacles
- (H) animals
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Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
user
Let's think first: Mollusks are a major food source for other organisms, including humans. Mollusks are invertebrates and are no exception. Invertebrates are a major food source for other organisms, including humans.... So the answer is [(C)]