Animal Characteristics

Characteristics ► Eukaryotic ► Multicellular ► Ways of moving that help them reproduce, obtain food and protect themselves ► Have specialized cells that form tissues and organs ► Animal cells do not have cell walls

Characteristics ► Adults mostly fixed in size and shape ► Heterotrophic ► Must digest food

Development of Animals ► Most develop from single, fertilized egg call a _________________. ► Males produce _________, females produce ________. ► Fertilization occurs when an egg is penetrated by a sperm ► Fertilization may be internal or external

Development of Animals ► Unicellular zygote divides by mitosis ► Embryo develops until blastula formed ► Blastula develops into gastrula  Inner layer of cells called endoderm, develops digestive organs  Outer layer of cells called ectoderm, develops into skin and nervous tissue

Development of Animals ► Gastrula develops until mesoderm formed ► Mesoderm = muscles, circulatory, excretory system

Symmetry ► Asymmetry – no symmetry

Symmetry ► Radial – think equal slices of pie

Symmetry ► Bilateral – animals have anterior, posterior, dorsal and ventral surfaces

Posterior – butt, bottom Anterior – head, front Dorsal – back side Ventral – stomach side

Animal Protection and Support ► Exoskeleton or endoskeleton  Hard outer protection or inner skeleton to protect ► Invertebrates and vertebrates  Without backbone vs. with backbone