Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
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) – middle layer (muscles, circulatory, excretory and respiratory systems) Mesoderm SYMMETRY Radial - round, or sphere shaped – right and left halves form a mirror image Bilateral – no definite shape Asymmetrical 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)