CH 24 WHAT IS AN ANIMAL?

https://www.youtube.com/watch?v=wd-QnKlfZHI 8:07 min. Animals https://www.youtube.com/watch?v=wd-QnKlfZHI 8:07 min.

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)

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

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

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