1. CH 24 WHAT IS AN ANIMAL?

2. CHARACTERISTICS OF ALL ANIMALS
Eukaryotic
Multicellular
Specialized cells (tissues & organs)
Ingestive heterotrophs
1.5 million species

3. STRUCTURES FOR SUPPORT AND DEVELOPMENT
Exoskeletons – - hard or tough outer coverings - provide a framework for support - protect soft body tissues - prevent water loss - protection against predators
Found on many invertebrates

4. Invertebrates – animals without backbones
% of animal species
- most have an exoskeleton
- exoskeletons are shed to make a new one as the animal grows
- Some invertebrates, sea urchins and sea stars; have internal skeletons (endoskeletons)

5. Invertebrates Examples – animals without backbones
- Sponges, Cnidarians – first animals to evolve from a multicellular ancestor
- Worms: flatworms, roundworms, segmented worms
- Mollusks: octopus, snails, squids, clams
- Arthropods: crustaceans, spiders, insects
Echinoderms: sea stars, sea urchins, sand dollars
- Invertebrate Chordates: lancelet, tunicates

6. Vertebrates – animals with a backbone
Endoskeleton – internal skeletons grow with the animal
- calcium carbonate -sea urchins/sea stars (invertebrates)
- cartilage – sharks
- bone – fishes, amphibians, reptiles, birds, mammals

7. SEXUAL REPRODUCTION (MOST)
Sperm + Egg = Zygote
Cleavage - - > zygote divides
Embryo -> an organism in the early stages of development

8. CELL LAYERS (Most have three layers)
Ectoderm - outer layer (skin & nervous tissue)
Endoderm - inner layer (digestive organs)
Mesoderm – middle layer (muscles, circulatory, excretory and respiratory systems)

9. SYMMETRY Radial - round, or sphere shaped
Bilateral – right and left halves form a mirror image
Asymmetrical – no definite shape

10. BODY PLANES Dorsal - back surface Ventral - belly surface
Anterior - top (head)
Posterior - tail end

11. BODY CAVITIES Coelum - fluid-filled cavity - mesoderm (earthworms)
Acoelomate no body cavity (flatworms)