CHARACTERISTICS OF ANIMALS: WELCOME TO YOUR KINGDOM!

 Adapted from Kim Foglia - April 2015

ANIMALS

Invertebrates

(animals without a backbone)

PoriferaCnidariaWormsMollusksEchinodermsArthropods

ANIMALSV

ertebrates (

animals with backbones)

FishAmphibiansReptilesBirdsMammals

CHARACTERISITCS OF ALL ANIMALS:

1. Eukaryotic2. Heterotrophic (ingestive)3. Multicellular/differentiated cells4. Cells have NO cell walls5. Movement (at some point in

lifespan)6. Reproduction (Most sexual)

Porifera

Cnidaria

Platyhelminthes

sponges jellyfish flatworms roundworms

Nematoda

Mollusca Arthropoda Chordata

Annelida Echinoderm

mollusks

multicellularity

Ancestral Protist

tissues

bilateral symmetry

body cavity

segmentation

ANIMAL EVOLUTION

eucoelom

starfish vertebrates

endoskeleton

segmentedworms

insectsspiders

backbone

LIFE ON EARTH

EMBRYOLOGY

REPRODUCTION•M

ost animals reproduce sexually•D

iploid stage usually dominates life cycle•H

aploid 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•T

he 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 adultEats different foodOften 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•I

n 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•M

ost 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

•INVERTEBRATESexcept ECHINODERMS

•Fate of embryonic cells determined later in development(INDETERMINATE)

•RADIAL cleavage

•Blastopore becomes ANUS

•ALL VERTEBRATES (Fish, amphibians, birds, reptiles, mammals)plus ECHINODERMS

PROTOSTOMESDEUTEROSTOMES

“Exception to the rule”

ECHINODERMS ARETHE ONLY INVERTEBRATEDEUTEROSTOMES