Explanation should include

warm-blooded vs. cold-blooded (endothermic [homeotherms] vs. ectothermic [poikilotherms])
skeletal systems (vertebrate and invertebrate)
respiratory systems
digestive systems
reproductive systems
muscular systems
nervous systems
size and body configuration (e.g., large body surface area to volume vs. small harsh environments such as the Arctic).

Process/Skill Questions:

What is the definition of habitat?
What are the similarities and differences between vertebrates and invertebrates?
What is the difference between ectothermic and endothermic?
What is the definition of ruminant? What advantages does a ruminant animal have over animals with other digestive systems?
How have species adapted to survive in different environments?
How is reproductive success based on habitat availability?
How does an animal’s role in the ecosystem influence its adaptations?
What advantages do different locomotion systems give to select animals?
How might the anatomy of an animal indicate its role in the ecosystem or position on the food chain?