1. What is An Animal?

2. Characteristics of Animals
All animals are heterotrophs – they have to get food from other organisms.
They are multicellular.
They have eukaryotic cells with NO cell wall.

3. Animals have epithelial, muscular, connective, and nervous tissues.
Epithelial tissue covers body surfaces.
Muscular tissues have proteins that allow the cells to contract and move the animal.
Connective tissue, like bone and blood, support an animal’s body.
Nervous tissue is made of nerve cells that carry information throughout the body.

4. Invertebrates do not have a backbone
Invertebrates do not have a backbone. This group includes animals like sea stars, worms, jellyfish, and insects.
Vertebrates have a backbone.
Read through pgs. 658 – 659.

5. Animal Development Animals will begin as a zygote (fertilized egg).
The zygote forms a blastula – a hollow ball of cells.
The blastula will fold in on itself and make a blastopore. The blastopore becomes the central tube of the animal. If the blastopore becomes the mouth the animal is called a protostome. If the animal anus is formed from the blastopore then it is called a deuterostome.
Echinoderms and all vertebrates are deutrostomes.
During development three cell layers also form. The endoderm is forms into a digestive tract and respiratory system. Mesoderm is the middle layer and it forms muscles and the circulatory, reproductive, and excretory systems.
The ectoderm is the outermost level - it forms sense organs, nerves, and the outer layer of skin.

6. Body Symmetry All animals, except sponges have some sort of symmetry.
Radial symmetry is when an animal has body parts that repeat around the center of the body, like a sea anemone. The animal can be cut any way through the center and form equal halves.
Bilateral symmetry there is only a single imaginary plane that can divide the body into left and right halves. Bilaterally symmetrical animals have left and right sides. They also usually have front and back ends and upper and lower sides.

7. Cephalization and Formation of a Body Cavity
Cephalization is the concentration of sense organs and nerve cells at the front of the body (gives the animal a head).
A body cavity is a fluid-filled space that is between the digestive tract and the body wall. This allows internal organs to be suspended and also allows for internal organs to grow and expand.