Animal Evolution: Invertebrate Diversity (Learning Outline)

1. Characteristics of organisms of the Kingdom Animalia 2. Evolution of animals: diploid multi-cellular aquatic organisms from a

colonial protist. 3. Highlights of animal evolution. 4. Order of appearance of animal groups. 5. Distinguishing features of the nine animal phyla and representative

organisms. 6. Highlights of evolution of land animals from aquatic ancestors 7. Order of appearance of land animals. 8. Parasitism as an integral part of animal evolution. 9. Common parasites causing common diseases and classification

groups 10.Place animals in order of appearance on earth. 11.For organisms covered in class or lab, place each in its classification

grouping , relation to others, and know their major evolutionary features.

Colonization of land

Animals

Cenozoic

Origin of solar system and Earth

Humans

Single-celled eukaryotes Atmospheric

oxygen

Multicellular eukaryotes

Prokaryotes

Proterozoic eon

Archaean eon

1

2 3

4

Last 0.5 bilion years

Evolution of Animals

Animals are eukaryotic, multi-cellular, heterotrophic organisms that ingest their

food

The ancestor of animals was probably a colonial, flagellated protist whose cells

gradually became more specialized and layered

Reproductive cells

Somatic cells

Digestive cavity

1 Colonial protist, an aggregate of identical cells

2 Hollow sphere of unspecialized cells (shown in cross section)

3 Beginning of cell specialization (cross section)

4 Infolding (cross section)

5 Gastrula-like “proto-animal” (cross section)

Species: Felis catus

Genus: Felis

Family: Felidae

Class: Mammalia

Order: Carnivora

Phylum: Chordata

Kingdom: Animalia

Bacteria Domain: Eukarya Archaea

• Species • Genus • Family • Order • Class • Phylum • Kingdom • Domain

Animal Diversity Eukaryotic Kingdom Animalia

– Body composition • Multi-cellular evolving from a colonial protist ancestor • Later forms with organ systems, organs, and tissues

– Heterotrophic • Some free-living others parasitic

– Early forms are aquatic – Evolutionary adaptations led to evolution of land

animals

Major steps of animal evolution

– Formation of tissues – Body made of three distinct layers of cells – Body symmetry: radial and bilateral – Bilateral organisms:

• Deuterostomes (Mouth from second opening) • Protostomes (Mouth from first opening)

Two major animal forms: • Invertebrates 97% of all animals- evolved earlier • Vertebrates- later forms in one phylum only

Classification Criteria for Animals Level of Organization Tissue, organ, organ systems Body Symmetry None- asymmetric Bilateral Radial Body Plan Sac with one opening Tube within a tube-two openings Segmentation (with and without appendages)

Sac Body Plan

Tube within Tube

Organ Systems (Coelom)

Level of Organization Multicellular

Segmentation

Spon

ges

Cni

daria

ns

Flat

wor

ms

Rou

nd w

orm

s

Mol

lusc

s

Anne

lids

Radial Symmetry Bilateral Symmetry

No Body Cavity (No coelom)

Body Cavity (Pseudocoelom)

Mouth from First Embryonic

Opening

Mouth from Second Embryonic

Opening

Arth

ropo

ds

Echi

node

rms

Cho

rdat

es Phyla

Ancestral colonial protist

No true tissues True tissues

Bilateral symmetry Radial symmetry

Eumetazoans

Bilaterians

Protostomes Deuterostomes

Spon

ges

Cni

daria

ns

Echi

node

rms

Cho

rdat

es

Flat

wor

ms

Mol

lusc

s

Anne

lids

Arth

ropo

ds

Nem

atod

es

Phylogenetic Tree of

Animals with 9 Phyla mostly

invertebrates

Invertebrates & Vertebrates

Phyla (by their common names)

Mouth from Second Embryonic

Opening

Mouth from First Embryonic

Opening

Animal development may include a blastula, gastrula, and larval stage

Key

Meiosis

Metamorphosis

Haploid (n) Diploid (2n) Sperm

Egg Zygote (fertilized egg)

Adult

Blastula (cross section)

Eight-cell stage

Digestive tract

Ectoderm Larva

Early gastrula (cross section) Future

mesoderm Later gastrula (cross section) Internal sac

Endoderm

1

2

3

4

5

6

7

8

Diploid cells

Animals can be characterized by basic features of their “body plan”. They may vary in symmetry.

Top

Bottom

Dorsal surface

Anterior end

Posterior end

Ventral surface

Animals and digestive cavities Incomplete gut (sac-like) radial symmetry bilateral symmetry Complete gut- type 1 bodies without shells bodies with shells bodies with segments with exoskeleton Complete gut- type 2 hydraulic tube feet bodies with notochord

Ancestral colonial protist

No true tissues True tissues

Bilateral symmetry Radial symmetry

Eumetazoans

Bilaterians

Protostomes Deuterostomes

Spon

ges

Cni

daria

ns

Echi

node

rms

Cho

rdat

es

Flat

wor

ms

Mol

lusc

s

Anne

lids

Arth

ropo

ds

Nem

atod

es

Animal guts Sac like Sac like Tube: 2 openings Tube 2: openings

INVERTEBRATES Sponges have a relatively simple, porous body

Sponges are the simplest animals and have no true tissues

Sponges filter food from the water passing through the porous body

Cnidarians are radial animals with tentacles and stinging cells and true tissues They have two body forms - Polyps, such as hydra - Medusae, the jellies

Hydra Jellyfish Sea anemone

Body covering (from ectoderm)

Tissue-filled region (from mesoderm)

Digestive tract (from endoderm)

Body covering (from ectoderm)

Muscle layer (from mesoderm)

Digestive tract (from endoderm)

Pseudocoelom

Body covering (from ectoderm)

Tissue layer lining coelom and suspending internal organs (from mesoderm)

Coelom

Digestive tract (from endoderm)

Animal body cavity-coelom

Flat worms- none

Round worms- pseudo coelom

Segmented worms- coelom

Flatworms are the simplest bilateral animals Flatworms are bilateral animals that have: - no body cavity - a sac-like gut - a simple nervous system - Free living & parasitic forms https://www.youtube.com/watch?v=wZBPqITnyME (15 minutes)

Bilateral symmetry

Gastrovascular cavity

Nerve cords

Mouth

Eyespots

Nervous tissue clusters

Parasitic flatworms e.g. Flukes and tapeworms Flukes: liver diseases - sheep and cattle (fascioliasis) fas·ci·o·li·a·sis - Human lung fluke disease (endemic hemoptysis): he·mop·ty·sis

Units with reproductive structures

Scolex (anterior end)

Hooks Sucker

Col

oriz

ed S

EM 8

0×

Tapeworms Cause diseases commonly after eating raw or undercooked meat (beef and pork) or fish that contains the immature form of the tapeworm

Parasites form a large proportion of the diversity of life on earth -Have a complex life cycles with more than one host

Round worms (Nematodes) • have a pseudocoelom and a • complete digestive tract and are • covered by a protective cuticle. • usually microscopic and colorless. • some live free in moist soil, water, or in decaying

matter. • Parasitic forms cause diseases of plants and

animals.

Trichinella juvenile

LM 3

50×

Muscle tissue

Col

oriz

ed S

EM 4

00×

Mouth

Free-living Parasitic- with

complex life-cycle

Molluscs- have a distinct body plan

• bilaterally symmetrical • a muscular foot, visceral mass, and a mantle which may

secrete a shell • well-defined organ systems: circulatory, respiratory, and

digestive with a rasping radula Visceral mass

Mantle

Radula

Mouth

Nerve cords

Foot

Mouth Radula

Digestive tract Shell

Digestive tract

Reproductive organs Heart

Coelom Kidney

Mantle cavity Anus

Gill

The largest group of molluscs includes the snails and slugs

Another group of molluscs are the bivalves have shells divided into two halves. This includes clams, oysters, mussels, and scallops

Another group are adapted to be agile predators such as squids and octopuses

Annelids (Segmented worms) – Segmentation provides added mobility for swimming and burrowing Earthworms eat their way through soil and have a closed circulatory system

Excretory organ

Giant Australian earthworm

Segment wall (partition between segments)

Mouth

Brain

Dorsal vessel

Coelom Digestive tract

Mucus-secreting organ

Segment wall

Anus

Bristles

Segment wall

Blood vessels Nerve cord

Pumping segmental vessels

Nerve cord Ventral vessel

Bristles

Epidermis Circular muscle

Longitudinal muscle Dorsal vessel Intestine

Excretory organ

The largest group of segmented worms search for prey on the seafloor or live in tubes and filter food particles

Arthropods (Jointed legs) – segmented animals – jointed appendages – exoskeleton – Extremely diverse

Antennae (sensory reception)

Head Thorax

Cephalothorax Abdomen

Swimming appendages

Walking legs

Mouthparts (feeding) Pincer (defense)

Diverse arthropods include: - Millipedes and Centipedes - Horseshoe crabs - Arachnids such as spiders, scorpions,

mites, and ticks - Crustaceans- aquatic. Include crabs,

shrimps, and barnacles - Insects

A dust mite (about 420 µm long) A scorpion (about 8 cm long)

A black widow spider (about 1 cm wide)

Col

oriz

ed S

EM 9

00×

Echinoderms have spiny skin and a water vascular system for movement - organisms such as sea stars and sea urchins - radially symmetrical as adults

Spine

Tube foot Tube foot

The water vascular system has suction cup–like tube feet used for locomotion and transport of substances including dissolved gases of respiration

Anus

Spines

Tube feet

Canals

Stomach