Animal Functions

When you have finished this section, take the Animals Functions Quiz.

The study of animals is called zoology.

Animals are different from plants in several important ways.

• Animals move much more freely than plants and are not rooted in the soil.
• Animals take in oxygen and give off carbon dioxide.
• Animals do not make their own food within themselves and therefore do not have chlorophyll.
• Animal cells do not have a cell wall.
• Animals eat plants, but plants do not eat animals generally..
• Animals in general are more advanced in their structure than plants.

Because animals are more complex or advanced than plants, they have different systems in their bodies to take care of the different jobs that allow them to live and function. Below is a description of these systems and illustrations of organs of these systems in humans. These systems are:

	Muscular/Skeletal - The muscular/skeletal system of an animal refers to the systems that give the animal its shape, protects its organs and allows it to move. Animals' bodies are protected in many ways. For some animals it is an outer skeleton or exoskeleton that protects their body. For others it is an inner or internal skeleton that protects the body. These skeletons give the animal bodies their shapes. An animal's form or body can be arranged to have Asymmetry - No specific form Radial Symmetry - There is a center to the animal's body from which limbs or arms come out from as if from a circle, much like the spokes on a bicycle wheel. Bilateral Symmetry - This means that an animal has two sides that are almost exactly the same on each side. Thus if you drew a line down the middle of the animal's body, one side would be a mirror image of the other side.
	Reproduction - This is how an animal makes more of itself or has babies. Animals can reproduce several ways. Fission - Splitting in half. Budding - Growing buds that break off to form new animals Sexually - This is where a male and female member of a species mates to reproduce a new animal baby.
	Excretion - This is how an animal gets rid of wastes after it uses energy to do its work. In humans kidneys and skin do this job.
	Digestion - This is how an animal breaks down the food it takes into its body. In humans the mouth, stomach and intestines are part of the digestive system.
	Respiration - This is how an animal takes in oxygen and gives off carbon dioxide as it uses energy. In humans the nose, throat and lungs would be part of the respiratory system
	Circulation - This allows food and energy to be distributed throughout the animal's body. In humans the heart, blood and blood vessels are part of the circulatory system.
	Nervous - This is how an animal takes in information from the world and uses that information to react to the world and to go about its life. This would include the animal's senses, its brain and nervous system.

All of these systems influence where an animal lives and how it survives. An animal that needs to live in water would not survive long on land and vice versa. Depending on how advanced these systems are in animals determines the group they belong in as well as how alike the systems are between and among the animals.