CHARACTERISTICS OF ANIMALS: WELCOME TO YOUR KINGDOM! Adapted from Kim Foglia - April 2015

ANIMALS Invertebrates (animals without a backbone) Porifera Cnidaria Worms Mollusks Echinoderms Arthropods

ANIMALS Vertebrates (animals with backbones) Fish Amphibians Reptiles Birds Mammals

CHARACTERISITCS OF ALL ANIMALS: 1.Eukaryotic 2.Heterotrophic (ingestive) 3.Multicellular/differentiated cells 4.Cells have NO cell walls 5.Movement (at some point in lifespan) 6.Reproduction (Most sexual)

Porifera Cnidaria Platyhelminthes spongesjellyfishflatworms roundworms Nematoda MolluscaArthropodaChordata AnnelidaEchinoderm mollusks multicellularity Ancestral Protist tissues bilateral symmetry body cavity segmentation ANIMAL EVOLUTION eucoelom starfishvertebrates endoskeleton segmented worms insects spiders backbone

LIFE ON EARTH

EMBRYOLOGY

REPRODUCTION Most animals reproduce sexually Diploid stage usually dominates life cycle Haploid stage characterized by sperm and eggs produced by meiotic division In most animal species, a small flagellated sperm fertilizes a larger non-motile egg, forming a zygote

DEVELOPMENT The zygote then undergoes cleavage, a succession of mitotic cell divisions with no cell growth between divisions Cleavage leads to a multicellular (usually hollow) ball called a blastula Blastula goes through gastrulation – the layers of embryonic tissues that will become adult parts are produced Result is a gastrula

Some animals, including humans, develop directly into adults Most animals include a larval stage Larva – sexually immature form of the animal that is:  morphologically different from adult  Eats different food  Often has a different habitat Larvae go through metamorphosis to juvenile stage that resembles adult

EMBRYONIC DEVELOPMENT

HISTORY OF ANIMALS SPANS MORE THAN ½ BILLION YEARS The animal kingdom includes the greatest diversity of living organisms Has an even greater diversity of extinct ones; ~99% of all species that have ever lived are now extinct Scientists estimate that the common ancestor of living animals lived sometime between 800 and 675 mya

ANIMALS CAN BE CHARACTERIZED BY BODY PLANS Despite the diversity in morphology, animals share a relatively small number of “body plans” Body plan – particular set of morphological and developmental traits, integrated into a functional “whole”

SYMMETRY A basic feature of animals is their type of symmetry – lack of it Asymmetrical (sponges) Radial symmetry: revolves around an axis (sea anemone) Bilateral symmetry: two-sided; has 2 axes of orientation, front to back and top to bottom (crawfish)

KINDS OF SYMMETRY Asymmetrical Radial Bilateral

DORSAL POSTERIOR VENTRAL ANTERIOR

CEPHALIZATION Most animals with bilateral symmetry have sensory equipment located at the anterior end, including a central nervous system (brain) in the head Provides efficient response to stimuli as sense organs encounter stimulus before rest of organism

TISSUE DEVELOPMENT In animals, true tissues are collections of specialized cells isolated from other tissues by membranous layers Sponges and a few others lack true tissues Gastrulation develops these layers – called germ layers

GERM LAYERS Ectoderm: covers surface of embryo; gives rise to outer covering on animal (and sometimes to central nervous system) Endoderm: innermost germ layer; lines the pouch that forms during gastrulation; gives rise to lining of digestive tract and organs such as liver or lungs

Animals that have only these two layers are diploblastic Examples: sponges, jellyfish, anemones

TRIPOBLASTIC ANIMALS Most animals have a middle germ layer called the mesoderm which fills much of the space between the ectoderm and the endoderm Forms muscles and most other organs between digestive tract and outer covering of animal

BODY CAVITIES Most tripoblastic animals have a body cavity – a fluid or air filled space between digestive tract and outer body wall This cavity is called a coelom A “true” coelom forms from tissues from the mesoderm Coelomates – organisms with a true coelom

Pseudocoelomates – coelom formed from mesoderm and endoderm; also a fully functional body cavity Acoelomates – lack a body cavity

PROTOSTOME & DEUTEROSTOME DEVELOPMENT Fate of embryonic cells determined very early in development (DETERMINATE) SPIRAL cleavage Blastopore becomes MOUTH INVERTEBRATES except ECHINODERMS Fate of embryonic cells determined later in development (INDETERMINATE) RADIAL cleavage Blastopore becomes ANUS ALL VERTEBRATES (Fish, amphibians, birds, reptiles, mammals) plus ECHINODERMS PROTOSTOMES DEUTEROSTOMES

“ Exception to the rule” ECHINODERMS ARE THE ONLY INVERTEBRATE DEUTEROSTOMES