Digestive System
Where does most chemical digestion occur?
Stomach & intestines — enzymes break food down here
Why do cheetahs have sharp teeth while cows have flat molars?
Different diets require different structures
What is the main job of the circulatory system?
To transport blood, oxygen, and nutrients throughout the body.
What structure do fish use to exchange gases?
Gills
Why does a lizard move between sunlight and shade during the day?
To regulate its body temperature through behavior.
Why is mechanical digestion important before chemical digestion?
It increases surface area so enzymes work better
What does the difference between a cow’s teeth and a cheetah’s teeth show about animal body structures?
Body structures are suited to an animal’s function and diet.
What is the difference between an open circulatory system and a closed circulatory system?
Open systems use hemolymph that is not always enclosed in vessels; closed systems keep blood inside vessels.
What structures do insects use to take in oxygen?
Spiracles
Why might coral respond more slowly to environmental changes than fish?
Some animals have more limited ability to sense and respond quickly to their environment.
What is the advantage of a complete digestive system?
One-way flow = more efficient absorption
A predator has sharp teeth but weak jaw muscles. How could this hurt its chances of survival?
It may not be able to catch, hold, or tear food effectively.
Why is a closed circulatory system usually more efficient than an open one?
Blood can be directed more quickly and precisely to tissues.
How does oxygen reach body cells differently in humans and in insects?
In humans, oxygen enters the lungs and is carried by blood; in insects, oxygen moves through tubes directly to body tissues.
How can a worm move and keep its shape even though it has no bones?
Fluid pressure inside its body provides support as a hydrostatic skeleton
Why doesn’t a tapeworm need a digestive system?
Absorbs nutrients directly from host
A bear eats both plants and animals. How should it be classified, and why?
An omnivore, because it can obtain energy from both plants and animals.
What do the atria do, and what do the ventricles do?
The atria receive blood returning to the heart, and the ventricles pump blood out.
How is excretion in insects different from excretion in vertebrates?
Insects move wastes into the digestive tract, while vertebrates remove wastes through organs such as kidneys.
What would happen if a nerve impulse started in the brain but never reached a muscle?
The muscle would not respond or move.
An animal eats but gains no nutrients—what system is failing and why?
Digestive system — nutrients aren’t being absorbed into bloodstream
Why is it incorrect to say animals simply “choose” what to eat based only on preference?
Their body structures and adaptations help determine what food they can obtain and use well.
Fish have a two-chambered heart and a single circulation path. How does this limit them compared with many other vertebrates?
Oxygen delivery is less efficient, which limits sustained activity compared with animals that have double circulation.
Why must animals that rely mainly on diffusion across the body surface stay small and moist?
Diffusion works best over short distances, and moisture helps gases move across the surface.
Why is it not enough for body systems to work separately? Why must they work together?
Life depends on systems supporting one another, such as digestion supplying nutrients and circulation transporting them