Animals

What is an animal? Eukaryotic multicellular organisms Heterotrophs Digest food within body Can move (for what purposes?) No cell walls

Development After fertilization, cell begins to divide Forms a hollow ball of cells called a blastula Cavity in blastula folds in to form a gastrula –Structure made up of 2 layers of cells with an opening at one end

Gastrulation

Germ layers produces 2-3 germ layers (cell layers) each develops into specific structures –ectoderm (outside) --> outer covering –endoderm (inside) --> gut lining –mesoderm (middle) --> muscles and other internal organs

Germ Layers

Adaptations Symmetry Body plans Protection & support

Symmetry Balance in proportions Leads to different types of movement Asymmetry –Irregular shape –Ex. sponge Radial symmetry –Can be divided in half along any plane –Ex. hydra Bilateral symmetry –Divided along its length into right & left halves –Ex. humans

Symmetry

Body Plans Development of body cavities Only found in bilaterally symmetric animals Allowed for –Larger growth –Organ systems

Types of Body Plans Acoelomate –3 body layers but no body cavity –Organs embedded in solid tissues –Do have a digestive tract –Often flattened to allow for diffusion of nutrients, water, oxygen, & wastes –Ex. flatworms

Types of Body Plans (cont’d) Pseudocoelomates Body cavity between endoderm & mesoderm Pseudocoelom-fluid filled cavity partly lined with mesoderm Allows for quick movements Ex. roundworms Coelomates Coelom-fluid filled space completely surrounded by mesoderm Allows for development of specialized organs Ex. humans, insects, fishes

Body Plans

Protection & Support Exoskeletons –Hard, waxy covering on outside of body –Provides a framework for support –Protect soft body tissue, prevent water loss, provide protection –Secreted by epidermis –Provide place for muscle attachment

Exoskeleton

Endoskeleton Internal skeleton that provides support inside an animals body Protects internal organs Internal brace for muscles

Invertebrates Do not have a backbone Some have no skeleton –Jellyfish, worms Often have exoskeletons –Ex. crabs, spiders, grasshoppers, dragonflies, beetles Echinoderms are invertebrates but have endoskeleton –Ex. starfish, sea biscuit, sand dollar

Vertebrates Have a backbone All are bilaterally symmetric All have endoskeletons Ex. fish, birds, reptiles, amphibians, mammals