Insects (from Latin insectum, a calque of Greek ἔντομον [éntomon], "cut into sections") are a class of invertebrates within the arthropod phylum that have a chitinous exoskeleton, a three-part body (head, thorax and abdomen), three pairs of jointed legs, compound eyes and one pair of antennae. They are the most diverse group of animals on the planet, including more than a million described species and representing more than half of all known living organisms. The number of extant species is estimated at between six and ten million, and potentially represent over 90% of the differing animal life forms on Earth. Insects may be found in nearly all environments, although only a small number of species reside in the oceans, a habitat dominated by another arthropod group, crustaceans. 

The life cycles of insects vary but most hatch from eggs. Insect growth is constrained by the inelastic exoskeleton and development involves a series of molts. The immature stages can differ from the adults in structure, habit and habitat, and can include a passive pupal stage in those groups that undergo 4-stage metamorphosis (see holometabolism). Insects that undergo 3-stage metamorphosis lack a pupal stage and adults develop through a series of nymphal stages. The higher level relationship of the Hexapoda is unclear. Fossilized insects of enormous size have been found from the Paleozoic Era, including giant dragonflies with wingspans of 55 to 70 cm (22–28 in). The most diverse insect groups appear to have coevolved with flowering plants.
What is the life cycle of insects?
How is it's growth constrained?
How else?
How many stages of metamorphosis are there?
What are insects?
How many body parts do they have?
What are they?
Are they diverse?
How many species?
How many extant species are there?
What does that represent?
What kind of environment can they be found?
Even in oceans?
What have they found in the Paleozoic Era?
What kind was found in this era?
How big?
Have they coevolved with anything?
What?
What is the metamorphosis stage of an adult?
What do they lack when the go through 3-stage metamorphosis?
It varies but most hatch from eggs
The life cycles of insects vary but most hatch from eggs
by the inelastic exoskeleton
Insect growth is constrained by the inelastic exoskeleton
development involves a series of molts
development involves a series of molts
Four
 that undergo 4-stage metamorphosis
a class of invertebrates
Insects (from Latin insectum, a calque of Greek ἔντομον [éntomon], "cut into sections") are a class of invertebrates
Three
a three-part body
head, thorax and abdomen
head, thorax and abdomen
Yes
They are the most diverse group of animals on the planet
more than a million
including more than a million described species 
estimated at between six and ten million
estimated at between six and ten million
represent over 90% of the differing animal life forms on Earth.
represent over 90% of the differing animal life forms on Earth.
nearly all
 Insects may be found in nearly all environments
Yes
 only a small number of species reside in the oceans
Fossilized insects of enormous size
Fossilized insects of enormous size have been found from the Paleozoic Era, i
giant dragonflies
 giant dragonflies
with wingspans of 55 to 70 cm
 with wingspans of 55 to 70 cm
Yes
 The most diverse insect groups appear to have coevolved with flowering plants.
flowering plants.
appear to have coevolved with flowering plants.
series of nymphal stages
adults develop through a series of nymphal stages
a pupal stage
Insects that undergo 3-stage metamorphosis lack a pupal stage