Animals AP Biology Mrs. Ramon

Intro. To Animal Evolution What is an animal?  Multicellular, heterotrophic eukaryotes  Lack cell walls  Two unique types of tissues: nervous tissue for impulse conduction and muscle tissue for movement.  Most animals reproduce sexually, with the diploid stage usually dominating the life cycle

Porifera Cnidaria Platyhelminthes spongesjellyfishflatworms roundworms Nematoda MolluscaArthropodaChordata AnnelidaEchinodermata mollusks multicellularity Ancestral Protist tissues bilateral symmetry body cavity segmentation Animal Evolution coelom starfishvertebrates endoskeleton segmented worms insects spiders backbone specialization &  body complexity specialized structure & function, muscle & nerve tissue distinct body plan; cephalization  body complexity  digestive & repro sys  digestive sys  body size redundancy, specialization,  mobility  body & brain size,  mobility radial bilateral

Early Embryonic Development

From Protozoans to Animals

Body Cavity ectoderm mesoderm endoderm ectoderm mesoderm endoderm mesoderm endoderm acoelomate pseudocoelomate coelomate coelom cavity pseudocoel Space for organ system development  increase digestive & reproductive systems increase food capacity & digestion increase gamete production Coelem  mesoderm & endoderm interact during development  allows complex structures to develop in digestive system ex. stomach protostome vs. deuterostome

Body Cavities (cont.) Acoelomates (the phylum Platyhelminthes) have a solid body and lack a body cavity.

Body Cavities (cont.) In some organisms, there is a body cavity, but it is not completely lined by mesoderm.  This is termed a pseudocoelom.  These pseudocoelomates include the rotifers (phylum Rotifera) and the roundworms (phylum Nematoda).

Body Cavities (cont.) Coelomates are organisms with a true coelom, a fluid-filled body cavity completely lined by mesoderm.

Invertebrates: Porifera Sponges  Adults sessile  No distinct tissues or organs  No symmetry

Invertebrates: Cnidaria Hydras, jellies, sea anemones and corals Tissues, but no organs Two cell layers Gastrovascular cavity Sessile (anemone) or floating (jelly) Cnidocytes (tentacles)

Invertebrates: Platyhelminthes Flatworms  Tapeworm, planaria  Mostly parasitic  Bilateral symmetry  Cephalization  Acoelomates with gastrovascular cavities  Asexual or sexual reproduction

Invertebrates: Nematoda Roundworms  Bilateral symmetry  Nonsegmented pseudocoelomates covered with tough cuticles  Digestive system  Many are parasitic: Hook worm Trichinella spiralis causes trichinosis  Undercooked meat

Invertebrates: Mollusca Snails, slugs, clams squid  Bilateral symmetry (some exceptions)  True coelem Polyplacophora (chitons) Gastropoda (snails and slugs), Bivalvia (clams, oysters, and other bivalves) Cephalopoda (squids, octopuses and nautiluses).

Invertebrates: Annelida Segmented worms  Earthworms, leeches  Segments Increase mobility Redundancy in body sections  Bilateral symmetry  True coelem

Invertebrates: Arthropoda Spiders, insects, crustaceans A billion billion (10 18 ) individuals (2/3 organisms) Bilateral symmetry Body segmentation Hard exoskeleton  Chitin and protein Jointed appendages

Arthropod Classes: Insecta 26 different orders within the Class Insecta Defining features:  6 legs  3 body parts

Arthropod Classes: Crustacea Lobsters, crab, crayfish, shrimp and barnacles Defining features:  Gills  2 pairs of antennae

Invertebrates: Echinodermata Sea stars, brittle stars, sea urchins, sand dollars and sea cucumbers Sessile or slow moving Water vascular system  Locomotion, feeding and gas exchange Spiny endoskeleton Radial symmetry

Vertebrates: Chordata Fish, amphibians, reptiles, birds and mammals  Features:  Notochord  Disks  Nerve chord  Brain and spinal chord  Pharyngeal slits  Muscular postanal tail

Vertebrates: Fish salmon, trout 450 mya Characteristics  body structure bony & cartilaginous skeleton jaws & paired appendages (fins) scales  body function gills for gas exchange two-chambered heart; single loop blood circulation ectotherms  reproduction external fertilization external development in aquatic egg gills body

Transition to Land Evolution of tetrapods Tibia Femur Fibula Humerus Shoulder Radius Ulna Tibia Femur Pelvis Fibula Lobe-finned fish Humerus Shoulder Radius Ulna Pelvis Early amphibian

lung buccal cavity glottis closed Vertebrates: Amphibian Characteristics  body structure legs (tetrapods) moist skin  body function lungs (positive pressure) & diffusion through skin for gas exchange three-chambered heart; veins from lungs back to heart ectotherms  reproduction external fertilization external development in aquatic egg metamorphosis (tadpole to adult) frogs salamanders toads 350 mya

Vertebrates: Reptiles Characteristics  body structure dry skin, scales, armor  body function lungs for gas exchange thoracic breathing; negative pressure three-chambered heart ectotherms  reproduction internal fertilization external development in amniotic egg 250 mya dinosaurs, turtles lizards, snakes alligators, crocodile embryo leathery shell chorion allantois yolk sac amnion

Vertebrates: Birds (Aves) Characteristics  body structure feathers & wings thin, hollow bone; flight skeleton  body function very efficient lungs & air sacs four-chambered heart endotherms  reproduction internal fertilization external development in amniotic egg 150 mya finches, hawk ostrich, turkey trachea anterior air sacs lung posterior air sacs

Vertebrates: Mammals 220 mya / 65 mya mice, ferret elephants, bats whales, humans muscles contract diaphragm contracts Characteristics  body structure hair specialized teeth  body function lungs, diaphragm; negative pressure four-chambered heart endotherms  reproduction internal fertilization internal development in uterus  nourishment through placenta birth live young mammary glands make milk

Vertebrates: Mammals Sub-groups  monotremes egg-laying mammals lack placenta & true nipples duckbilled platypus, echidna  marsupials pouched mammals  offspring feed from nipples in pouch short-lived placenta koala, kangaroo, opossum  placental true placenta  nutrient & waste filter shrews, bats, whales, humans