What is an Animal (pgs 6-11) (Functions of Animals (Obtaining Food and…
What is an Animal (pgs 6-11)
Structure of Animals
Animals are many celled organisms that feed on other organisms.
is the basic unit of structure and function in living things.
The cells of most animals are organized into higher levels of structure, including tissues, organs, and systems.
A group of similar cells that perform a specific function is called a
Tissues may combine to form an
, which is a group of several different tissues.
Groups of structures that perform the broadest functions of an animal are called
Tissues form organs, organs form systems to complete functions in an animal's body.
Functions of Animals
The major functions of animals are to obtain food and oxygen, keep internal conditions stable, move, and reproduce.
Structures or behaviors that allow animals to perform these basic functions in their environments are called
Obtaining Food and Oxygen
An animal cannot make food for itself. It obtains food by eating other organisms such as plants, other animals, or a combination of both.
They have adaptations to allow them to eat particular kinds of food.
Food provides animals with raw materials for growth and with energy for their bodies' activities such as breathing and moving.
Most animals take food into a cavity inside their bodies. Inside, food is digested, or broken down into substances that the animal's body can absorb and use.
Keeping Conditions Stable
Animals must maintain a stable environment within their bodies. If this balance is lost, the animals cannot survive for long.
All animals move in some way at some point in their lives.
Animal movement is usually related to meeting the basic needs of survival.
Animals do not live forever and so, need to reproduce.
is the process by which a new organism develops from the joining of two sex cells, a male sperm cell and a female egg cell.
The joining of sperm and eggs is called
. Sperm and egg cells carry information about the characteristics of the parents that produced them such as size and color. New individuals resulting from sexual reproduction have a combination of characteristics from both parents.
is the process by which a single organism produces a new organism identical to itself.
Classification of Animals
Biologists have already identified over 1.5 million species of distinct types of animals and they are discovering more every year.
Biologists have classified animals into about 35 major groups called phyla.
Biologists do not know the exact way in which evolution took place but, they can make inferences on the basis of the best evidence available. They hypothesize that all animals arose from single-celled ancestors.
Animals are classified according to how they are related to other animals. These relationships are determined by an animal's body structure, the way the animal develops, and its DNA.
Vertebrates are classified in one phylum and invertebrates are classified in another.