Two germ layers - endomorph (inside) - ectomorph (outside)

ANIMAL EVOLUTION AND DIVERSITY Flashcards by Thomas Scott

Animal Characteristics

Eukaryotic 
Heterotrophic (ingestion)
Multicellular 
Flexible
-no cell walls
-proteins connect cells
Tissues (except sponges)
-muscle and nervous tissues
Sexual reproduction (most animals)
-diploid dominant stage
Pattern of embryonic development 
-cleavage
-gastrulation

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Common ancestor

Choanoflagellates

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Factors for Cambrian Explosion (535-525 million years ago)

More oxygen
Better predators
HOX Gene evolved

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When did animals comes to land?

Invertebrates
Arthropods (450 million years ago)

Vertebrates
Tetrapods
Amphibians and amniotes (365 million years ago)

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Metazoan: Parazoa

Sponges
Lacks symmetry, defined tissues and organs
Can disaggregate and aggregate their cells

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Metazoan: Eumetazoa

All animals but sponges
Has symmetry
Distinct tissues
Irreversible differentiation for most cells

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Parazoa Phylum

Porifera

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Phylum: Porifera

No symmetry
No tissues
Mostly marine
Spicules

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Choanocytes

Phylum: Porifera
Also known as collar cells 
Flagella create current
Traps food particles
Ingestion by phagocytosis

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Amoebocytes

Phylum: Porifera
Transports nutrients to cells
Produces spicules/spongin

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Porifera Food Acquisition

Filter feed

Intracellular

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Porifera Reproduction

Sexual or asexual

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5 Innovations of Animal Body Plan

Tissues
Bilateral symmetry 
Body cavity 
Pattern of embryonic development 
Segmentation

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Diploblastic

Two germ layers

endomorph (inside)
ectomorph (outside)

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Phylums that are diploblastic

Cnidaria

Ctenophora

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Phylum: Cnidaria

Symmetry: Radial 
Tissue layers: Diploblastic 
Digestion: GV
Circulatory system: none
Respiratory system: none

Two forms
-polyps and medusa
Only animal nematocysts

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Phylum: Ctenophora

Tissue layers: triploblastic

Colloblast

3 kinds of symmetry

Asymmetric
Radial
Bilateral

Characteristics of Bilateral Symmetry

Move with directions
Dorsal and central surfaces
Anterior and posterior sides (cephalization)

3 germ layers

Ectoderm-surface and nervous system
Mesoderm- skeleton and muscles
Endoderm- organs and intestines

Coelom

Body cavity 
Repositions body fluids 
Allows complex tissues/ organs to develop
Allows larger body size 
(Not homologous)

Acoelomate

No space between digestive tract and outer body wall

Pseudocoelomate

Fluid filled space between digestive tract and outer body wall

Coelomate

Fluid filled space between digestive tract and outer body wall lined with mesodermal tissue

Deuterostome Phyla

Chordata | Echinodermata

Protostomes

Spiral cleavage Cell excision causes arrested development Determinate development Blastopore becomes mouth

Deuterostome

Radial cleavage Cell excision causes separate embryo Indeterminate development Blastopore becomes anus

Open circulatory system

Blood passes from vessels into sinuses, mixes with body fluids and re-enters the vessels

Closed circulatory system

Blood moves continuously through vessels separated from body fluids

2 kinds of protostomes

Spiralians- grow by adding mass Ecdysozoans- increase in size by molting their external cuticles or skeletons

2 main groups of spiralians

Lophotrocozoa and platyzoa

2 successful Ecdysazoan phyla

Nematoda and Arthropoda

Phylum: Plathyhelminthes

``` Spiralian Platyzoa Acoelomate Cilliated epithelial cells Gastrovacular cavity - cannot feed continuously Food acquisition through pharynx Excretion through flame cells Eyes distinguish between light and dark Hermaphroditic ```

Flukes

``` Phylum: Plathyhelminthes Parasitic worms Larval infects mollusks Adults infect vertebrates Causes schistosomiasis ```

Tapeworms

Phylum: Platyhelminthes Parasitic worms Intestines of vertebrates 3 parts: scolex, unsegmented neck, proglottids

Phylum: Rotifera

``` Spriralian Platyzoa Tiny multicellular Unsegmented Pseudocoelemate Movement: cilia Some reproduce by parthenogenesis ```

Phylum: Nemertea

Reduced coelem Mostly marine Closed circulatory system Alimentary canal

Phylum: Bryozoa

``` Spiralian Lophotrocozoa (lophophore) Radial cleavage Grow in colonies U shaped alimentary canal (mouth near anus) Asexual reproduction by budding ```

Phylum: Brachiopods

``` Spiralian Lophotrocozoa (lophophore) Radial cleavage Grow solitarily Have 2 calcified shells Shells are dorsal and central not lateral bivalves ```

Phylum: Mollusca

``` Spiralian Lophotrocozoa (trocophore) 2nd most diverse phylum Symmetry: Bilateral Circulatory: open Respiratory: diffusion and lungs Digestion: complete May have head not always (clams) Have radulas for shredding food 3 regions: foot, visceral mass, mantle Digestive,excretory, and reproductive organs in visceral mass Shell protects viscera Has mantle ```