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