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Download ANIMAL DIVERSITY ANIMAL – a multicellular, heterotrophic
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ANIMAL DIVERSITY ANIMAL – a multicellular, heterotrophic eukaryote that eats by ingestion (food taken inside the body) -cells lack cell walls -diploid cells and sexual reproduction -development regulated by Hox genes ANIMAL DEVELOPMENT STAGES: zygote – blastula – gastrula – embryo EARLY DEVELOPMENT: 1) Fertilization - haploid gametes (ova and sperm) form a zygote 2) Cell division results in a hollow ball of cells – the blastula (all cells are identical) 3) One side of the gastrula pulls inward forming a gastrula Gastrula Stage -cells differentiate into 3 cell types 1) ectoderm – cells on the outside that will form nervous and skin tissue 2) endoderm – cells on the inside that will form gut tissue 3) mesoderm – cells in-between endo/ecto that will form muscle, reproductive, and circulatory tissue LATE DEVELOPMENT * some animals have complex life cycles - go through a larval stage and undergo metamorphosis before reaching adult (adult is completely different than larva) GENETIC CONTROL Hox genes -have homeoboxes (Ch. 11) -found only in animals EVOLUTION From colonial protists (collection of identical unicellular organisms) colonial choanoflagellate* *Earliest animals – Phylum Portifera – the Sponges – have flagellated cells called choanocytes that are similar to choanoflagellates, and a simple body plan -hypothetically followed “blastula-gastrula” type stages (SEE 18-02Evol) Late Precambrian era – 1st animals (all soft-bodied) Cambrian explosion – fossil record shows “sudden” radiation of animal forms Why? Ecological, geological, and/or genetic changes provided conditions for change? Invertebrates evolved 1st BODY FEATURES A) BODY PLANS 1. asymmetry – body cannot be divided into equal sections along any plane (ex. some sponges) 2. radial symmetry – body can be divided from the center into equal portions (ex. Starfish) 3. bilateral symmetry – body can be divided through the center into mirror halves (ex. Earthworm, human) B) TISSUES -no true tissues -true tissues (combinations of cell types performing a single function) C) BODY CAVITY = COELOM -fluid-filled space between the digestive tract and body wall Types: -no body cavity (acoelomate) -body cavity: 2 types 1. Pseudocoelomate (“false coelom”) – body cavity is NOT lined completely w/mesoderm 2. Coelomate (“true coelom”) – body cavity is lined w/mesoderm - Protostomes – coelom develops from cell masses (opening of gastrula becomes the mouth) -Deuterostomes – coelom develops from digestive tube (opening of gastrula becomes the anus) D) CEPHALIZATION -development of a definite head end (worms) E) SEGMENTATION -arrangement of body parts into repeating segments -the development of the three major segments of animals (head, thorax, and abdomen) as diverse as fruit flies and humans controlled by the same genes, indicating early evolution E) JOINTED APPENDAGES *allowed multiple variations on appendages: -legs (arms), wings, antennae, claws, many moving mouth parts OTHER MORPHOLOGY SKELETONS Invertebrates – no backbone 1) Hydrostatic pressure – internal water pressure supports organs (ex. Earthworm) *changes in hydrostatic pressure may be used for movement (ex. Starfish) external - Marine soft bodied animals ex. Jellyfish (Phylum Cnidarian) – supported by water 2) Exoskeleton- outer skeleton Chitin in Phylum Arthropoda (insects, crustaceans, arachnids = spiders/scorpions) Shells in Phylum Mollusca (clams, snails) -must be molted during growth Vertebrates – have a notochord or a backbone Endoskeleton – internal Echinoderms (spines of starfish) Bone Cartilage In vertebrates – includes a notochord or backbone CIRCULATORY SYSTEM open vs. closed RESPIRATION -skin (simple diffusion) -gills -lungs VERTEBRATE CLASSES Phylum Chordata -all have a dorsal hollow nerve cord and a primitive notochord or backbone 5 CLASSES -evolved in this order? Fish Amphibians Reptiles Mammals Birds CLASS: Birds Characteristics: -body covering – feathers -thermoregulation- endothermic -respiration gas exchange:-lungs heart chambers:- 4 *all have closed circulation -reproduction: fertilization: internal embryonic development: eggs other: ex. shorebirds, songbirds, raptors *bodies have flight adaptations - hollow bones - resp. one-way air flow, more efficient -feathers encourage “lift”
