Introduction to Animals

General Characteristics All animals are heterotrophic

Different digestive systems

Animals are either invertebrates or vertebrates

Body variations allow animals to live in a diverse range of habitats

Cells are organized into tissue, that is specialized to perform a specific function

ReproductionHermaphrodites: organism that produces both eggs and sperm in the same body (earthworms)Zygote: when sperm penetrates egg to form a fertilized egg

External Fertilization: egg and sperm combine outside the animal’s body (fish)

Internal Fertilization: sperm and egg combine inside the animal’s body

Development

Endoderm Cells: develop into digestive organs and the lining of digestive tractEctoderm Cells: Nervous tissue and skinMesoderm Cells: Muscle tissue, circulatory system, excretory system, and sometimes respiratory system

Human Development

SymmetrySymmetry describes the similarity or balance among body structures of organisms

Assymmetrical: Irregular shape and has no symmetry or balance in its body structure

Radial: Can be divided along any plane through a central axis into roughly equal halves

Bilateral: Can be divided into mirror image halves only along one plane through a central axis

Cephaliztion: animals with bilateral symmetry also have an anterior, or head end, and a posterior, or tail end & dorsal (back), ventral (front).

Body CavitiesCoelomates: Tissue formed from the mesoderm that lines and encloses the organs in the coelom

- Coelom: Huge adaptation in evolution of larger and more specialized body structure.

Pseudocoelmates: Fluid-filled cavity that develops between the mesoderm and the endoderm rather than developing entirely within the mesoderm as in coelomates.

Acoelomates: Animals that do not have a coelom. Have solid bodies, without a fluid filled body cavity between the gut and the body wall.

Segmentation• Important feature in the evolution of coelomate animals.

Two Advantages of Segmentation:1) Segmented animals

can survive damage to one section and still live because other sections may be able to carry out the function

2) Movement is more effective since each segment moves independently