CH 24 WHAT IS AN ANIMAL?
Jan 18, 2016
CH 24 WHAT IS AN ANIMAL?
CHARACTERISTICS OF ALL ANIMALS
Eukaryotic
Multicellular
Specialized cells (tissues & organs)
Ingestive heterotrophs
1.5 million species
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
Invertebrates – animals without backbones
- 95-99% 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)
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
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
SEXUAL REPRODUCTION (MOST)
Sperm + Egg = Zygote
Cleavage - - > zygote divides
Embryo -> an organism in the early stages of development
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)
SYMMETRYRadial - round, or sphere shaped
Bilateral – right and left halves form a mirror image
Asymmetrical – no definite shape
BODY PLANESDorsal - back surfaceVentral - belly surfaceAnterior - top (head)Posterior - tail end
BODY CAVITIES
Coelum - fluid-filled cavity - mesoderm (earthworms)
Acoelomate - no body cavity (flatworms)