Animal Evolution and Diversity

Biology 201

What is Life?

Characteristics of Life

1. They have organization.

2. They regulate themselves.

3. They grow and develop.

4. They have metabolism.

5. They are irritable.

6. They reproduce.

7. They evolve.

Organization (Order)

• All living things:– Complex organized structures

made of cells– Chemically based on carbon

Regulation• Maintain a consistent internal environment• Some will be able to homeostatically control their internal environment • Ex. Reflexes (positive and negative feedback)• What are some of the parameters controlled inside living things?

Grow and Develop

• Acquire materials and energy from external environment and convert them into to different molecules to maintain life.

Metabolism

Irritable

• Respond to stimuli from both living and nonliving sources

Reproduce• Pass on biological information to

succeeding generations• Genes and DNA

Life Evolves• Species change over time to

better adapt to their environment

Levels of Complexity

Biosphere

Ecosystems

Community

Biomes

Populations

Organism

Organ system

OrgansTissues

Cells

Molecules

Atoms

Animal Trivia

• Heart is the size of a average car.• Largest BV you could swim inside.• Tail fluke is the width of a small aircraft.

Animal Lineage

• multicellular eukaryotic heterotrophs

• ingest their food with internalized digestion, store CHO as glycogen

• most reproduce sexually• share common development• most have tissues (muscle,

nerves, etc.)

Development• most form zygote from

fertilized egg• after much cell division

(cleavage) ball of cells form hollow ball blastula

• grows and rearranges into gastrula (2-3 layered embryo) formation of germ layers which give rise to tissues and the gut

• may develop directly into adult body but many form larva that undergoes metamorphosis into adult

Metamorphsis• Larva may look and behave

very differently than adult• Change to adult completed

while in pupal stage

Development may Reflect Evolutionary History

• early protist ancestor was probably colonial flagellate• cell specialization aided colony behavior• rearrangement of colony shape allowed further cell

specialization and the development of tissues and organs

Artists conception of the Cambrium Sea (540 mya)

The Cambrian Explosion

All animal phyla were well developed by late CambriumWho is your ancestor?

Four key Events in Animal Evolution1. Development of tissues -cell lines with specific functions

2. Radial vs. Bilateral Symmetry

3. Development of body cavities

4. Protostome vs. Deutrostome developmental patterns

Symmetry

Body Cavities

(Coelomates)

Body cavities (coeloms)allow organs to moveindependently form bodyand may act as a hyrdostaticskeleton

Protostome vs. Deuterostomes

• the first hole that forms gut is either the anus or the mouth

• Protostomes form the mouth first

• Deuterstomes form anus first

Classification of Life Forms:

Three Domains

• Domains: Eukarya, Bacteria, Archae

• Bacteria and Archae are prokaryotes

• Eukarya is divided on the basis of complexity and method of nutrition

EukaryaFungiPlantae Animalia

Protista

Bacteria

Archae

Eukarya

Modes of Nutrition

Autotrophs

Photosynthetic or chemosynthetic

HeterotrophsPhoto-heterotroph

Chemo-heterotroph-absorbers-digesters

• sessile adult filter feeders• flagellated larvae, no

tissues• all aquatic, most marine• types based on composition

of skeletal elements

Sponge Body

Sponge Types: glass, carbonate and spongin sponges

• corals, anemones, hydras and jellies• two sets of tissues, radial symmetry• archenteron (gastrovascular cavity)

surrounded by tentacles• tentacles have cnidocytes (stinging

cells)• two body forms: polyp and medusa

(some alternate)

Body Forms

Polyps

Corals

Anemones

Medusans

Lion’s Mane Jelly

Purple Stripe Jelly

A Comb Jelly

Cnidocytes

Typical Cnidarian Life Cycle

• all tissues present, some head development, bilateral symmetry

• gastrovascular space, no body cavities

• Includes free living and parasitic species (flukes and tapeworms)

Platyhelminthes

Body Form

• flattened body, organs and organ systems present

• hermaphroditic• incomplete gut (one

opening only)

Cestoda: Tapeworms• two hosts: herbivore and predator• each proglottid is male and female and is

a reproductive factory producing 1000s of eggs

• little organ systems• see life cycle

Scolex

Proglottids

Nematodes

• have tissues, bilateral, • pseudocoeloms, complete gut• separate sexes• most parasitic includes pinworms

and hookworms• second most abundant animal

phylum

Nematodes

• tough outer cuticle, have gastrointestinal tract but no circulatory system

• show no segmentation and have only longitudinal muscles

• may lay more than 100,000 eggs a day

Trichinosis

Heartworms

Segmented Worms

• highly segmented body separated by septum• has tissues, coelom, bilateral, complete gut• closed circulatory system and extensive

nervous system• 3 classes: earthworms, polychaetes, and

leeches

Earthworm Anatomy

Annelid Diversity

Annelid Diversity Christmas Tree Worm

Clam Worm

Annelid Diversity

Molluscs

• Triploblastic, coelomate, complete gut, bilateral

• Soft body, mostly aquatic (or very moist)• Most have shell secreted by mantle

Body Plan

• Foot –muscular locomotion organ• Visceral Mass –internal organs• Mantle –covers visceral mass, secretes

“mother of pearl”• Most have rasping tongue -radula

Gastropods –snails and slugs

• Glides on foot• Body grows with torsion• Most herbivorous

Bivalves –clams, scalops, oysters, and mussels

• Filter feeders using gills• Two half shells with hinge

Cephalopods -squids, octopus, nautilus• Internal or no shell• Most can produce ink• Use siphon for propulsion• Foot modified into tentacles

• most successful group of animals to ever live• segmentation with high degree of

specialization• exoskeleton made of chitin• Extensive sensory structures• Open circulatory system (hemolymph)

Jointed Leg Animals

Typical Anatomy• Specialized appendages, one

pair per body segment• Hard chitin exoskeleton

– Useful in protection– May be highly modified– Serves as muscle attachment– Impermeable to water– Most be molted to allow growth

Molting

Four Major Groups

1. Trilobytes –extinct

2. Chelicerates -spiders, scorpions, tickshorseshoe crabs, and mites-specialized feeding appendage (chelicera)

3. Crustacea –crabs, lobsters, crayfish, isopods

4. Uniramia –insects, millipedes, and centipedesInsects make up the largest class of animals

Chelicerates

• Horseshoe crabs represent an ancient order of arthopods

• Arachnids include scorpions, spiders, mites and ticks

Spiders

• 8 legs, chelicera modified into fangs

• Poisonous• Produces web

Crustaceans• Mainly marine, few

freshwater and one terrestrial• Have a cephalothorax and

abdomenLobster

Centipedes

• 2 pairs of legs per body segment• Can produce a foul smelling

fluid• Can roll up into spiral• herbivores

Millipedes

• 1 pair of legs per body segment

• Fast predators• poisonous

Insects

• Head, thorax and abdomen

• 6 walking legs• 2 pair of wings )only

invertebrate able to fly• Extreme diversity

Echinoderms• Deuterostomes, radial symmetry in adult• Bilateral larva• Endoskeleton with spines that protrude

through skin• Water vascular system with tube feet

Sea Star Anatomy

Feeding Star Fish

Echinoderm Diversity

Sea Lilies

Chordates

• Deuterostome, bilateral, coelomate• Complete gut, closed circulation• Includes the vertebrates (back boned

animals)

Characteristics of all Chordates

Must be present sometime during life cycle

• upper pictures: Tunicates look chordate like only as a larva, otherwise they are sessile filter feeders

• Right: Lancelets are poor swimmers but burrow in loose sand easily, filter feed to survive. An animal similar to these led to all vertebrates.

Primitive Invertebrate Chordates

Can you spot your ancestor?

Possible Chordate AncestryPre-chordate

• Sessile arm feeder• Bilateral, ciliated larva (BCL)

Living Relatives

(starfish)

Echinoderms(esp. crinoids)

Hemichordate-like• Sessile, ciliated arm feeder with

BCL• Gill slits for better feeding• Appearance of pre-notochord• Some metameric muscle in larva

Hemichordates:acorn worms; pterobranchs

• Loss of tentacles• Post-anal tail development• Some metameric muscles• Tadpole like larva; more time

spent as larva• Notochord and dorsal hollow nerve

cord in larvaUrochordata:tunicates

Primitive vertebrate

• All chordate characteristics present• Development of kidney and other

organ systems• Extensive segmental musculature• Motile filter feeder

Cephalochordata:amphioxus

neoteny

Protochordates