BIOL 108 University of Alberta

Chordata

*Bilateral symmetry

*deuterostomia (triploblastic, radial cleavage)

*coelom

*segmented bodies

What makes animals unique?

-multicellular eukaryotes

-Lack cell walls

-Bodies and cells held together with collagen

-Unique nervous and muscle tissue --> movement

-Chemoheterotrophic

-Sexual reproduction (mostly)

-Capable of movement at least during one stage of life cycle

True Tissues

collections of specialized cells isolated from other tissues by membranous layers

Chemoheterotrophic

consumes other organisms for carbon-based food

Key innovations of animal evolution

1. Patterns of embryonic development

2. Development of different tissues

3. Type of body symmetry

4. Presence or absence of a body cavity

Homeobox

-Highly conserved nucleotide sequence

-Regulatory genes --> turn the other genes on/off

-Control anterior to posterior development

Hox genes

-Series of genes that controls the differentiation of cells and tissues in an embryo

Embryonic Development

1. Cleavage of the zygote

2. Creation of the Blastula

3. Blastula undergoes gastrulation forming a gastrula --> creates layers of embryonic tissue

Protostomia

First invagination of the gastrula becomes the mouth

-proto = first -stoma = mouth

Deuterostomia

Second invagination becomes the mouth becomes the mouth

-deutero = second

(First opening becomes anus, or closes)

cell cleavage

Protostomes- the new row of developing cells is twisted (spiral cleavage) (determinant development)

Deuterostomes- The new row of developing cells stacks directly on top of the previous ones (radial cleavage) (indeterminant)

direct development

a kind of growth in which an organism gets larger but doesn't go through other changes

Indirect development

intervening stages whose morphology differs greatly from the sexually mature adult

Eumetazoa

animals with true tissues

germ layers

endoderm: digestive tract

mesoderm: muscle and other organs

ectoderm: outer covering (skin and nerves)

Radiata

2 embryonic layers

DIPLOBLASTIC: endo and ectoderm

Bilateria

-3 embryonic cell layers

-TRIPLOBLASTIC: endo, ecto, and mesoderm

-varying degrees of cephalization

radial symmetry

no front and back, or left and right

(Porifera, Cnidaria, Ctenophora)

bilateral symmetry

-two sides (mirror image)

-Right, left side

-Dorsal, and ventral sides

-Anterior (head) and posterior (tail)

-Cephalization

Cephalization

Development of a "head" concentration of nerve tissue and sensory organs at the anterior end of an organism

- Adapted for forward & directional movement (response to stimuli) (better able to search for food) (better defense)

Body Cavities

-Most triploblastic animals possess a fluid-filled body cavity

- A true body cavity is called a coelom, derived from mesoderm

coelomates

-possess a true coelom

-triploblastic

Pseudocoelomate

-An animal whose body cavity is not completely lined by mesoderm

-triplobastic

Acoelomate

a triploblastic animal that lacks a coelom, or body cavity

-mass of tissue

Choanoflagellates

a group of free-living unicellular and colonial flagellate eukaryotes considered to be the closest living relatives of the animals.

-similar cell morphology to Porifera

evolution of multicellularity

Many lineages of fungi, algae, and animals evolved multicellularity independently from unicellular ancestors

Colonial Hypothesis of Multicellularity

Cells in colonies more likely had/have a better survival rate compared to unicellular counterparts. (natural selection)

-evidence is seen in collar cells of sponges as they are nearly identical to choanoflagellates

Overcoming limitations of diffusion

Evolution of bulk flow

(specialized transport cells --> vertebrate circulatory system, plant vascular system, fungal hyphae)

- exception: sponges and jellyfish

Paleozoic Era

-Cambrian explosion

-colonization of land

-land invertebrates and vascular plants

Mesozoic Era

Early mammals, gymnosperms, dinosaurs, angiosperms

Cenozoic Era

Mass extinction of land and marine animals paved the way for mammals to increase in size and exploit the new niches

Porifera

por = pore, fer = to bear

-Lack Hox Genes --> determinate growth

-Sessile except for larval stage

Cnidaria

-Radial symmetry

-Diploblastic (ecto and endoderm)

-Two basic body forms (polyp and medusa)

Polyp form (cnidaria)

-sessile form

-oral end upwards

-attached to a substrate

Medusa form (cnidaria)

-motile form

-oral end downwards

-moves freely through water (hydrostatic skeleton)

Cnidocytes

-Cells that house the stingers in cnidarians

-defense and prey capture

Acoela

-acoelomate worms

-no anus or gut cavity

Platyhelminthes

-flatworms

-acoelomates (no fluid-filled body cavity)

-Lack circulatory system and gas-exchange system

-do not have a complete digestive system

Annelidia

-segmented

-Eucoelomates

-Closed circulatory system

-Complete digestive system w/ anus

Turbellaria

-class of platyhelminths

-free-living flatworms

-eye spots

Cestoidea

-class of platyhelminths

-tape worms

-Endoparasite

-Lack digestive system

-scolex head to grip gut

-reproduce with proglottids

Trematoda

-class of platyhelminths

-flukes

-parasitic

-hermaphroditic

-Complex life cycle

Polychaeta

-class of annelids

-body segments w/ fleshy lobes (parapodia)

-differentiated head

-free spawning

Oligochaeta

-class of annelids

-lack parapodia and well developed head

-few chaetae (oligo = few)

-simultaneous hermaphrodites (copulate as both male and female)

-direct development

Hirudinea

-class of annelids

-lack parapodia, have clitellum

-lack chaetae, use two suckers for locomotion

Mollusca

-calcareous shell

-shell lost or reduced in many taxa

-mantle: thin layer of tissue that secretes shell

-organs in visceral mass

-radula: mouthparts

-gills

-open circulatory system

-many have trochophore

Fungi

-colonized land at the same time as plants

Five phyla of fungi

Chytridiomycota

Zygomycota

Glomeromycota

Ascomycota

Basidiomycota

Basic characteristics of fungi

-Chemo-heterotrophs

-Cell walls made of chitin

-Body composed of hyphae

Fungal Reproduction

-Produce spores both sexually and asexually

-spores grow haploid hyphae

plasmogamy and karyogamy

Karyogamy: fusing of cell nuclei

Plasmogamy: fusion of two or more cells without fusing of cell nuclei

Chytridiomycota

Digest tissues of living host

Zygomycota

Few are predators (black mold, bread mold)

Glomeromycota

form mutualistic associations with plant roots

Ascomycota

Form spores sexually in saclike asci

Basidiomycota

Pedestal reproductive structures (basidium)

Yeast

unicellular fungi

Lichen

symbiotic association between a fungus and a photosynthetic organism

Gastropoda

Glide using their large muscular foot

Torsion (anus above head)

Nudibranchs

Sea slugs

Consume cnidarians nematocysts to use as defense

Bivalvia

-Two hinged shells

-Filter feed

-no radula

Cephalapoda

-no externa shell (minus nautilus)

-Long tentacles around mouth

-Radula modified as biting beak

-Siphon (jet-propulsion)

-Maternal Care

-Do not have trochophore larvae

-Direct development

-Excellent vision

-Complex behavior

Ecdysozoa

ecdysis = molting

-entire cuticle shed at once

Cuticle

Three layers

*endocuticle (on the epidermis, innermost layer)

*exocuticle (in between the endocuticle and the epicuticle)

*epicuticle (outermost layer)

Epidermis

living cells that secrete substances to form the cuticle

Nematoda

-Morphologically similar to earthworms

-pseudocoelomates

-Complete digestive system

-No circulatory system

-Two sexes

-Eutelic

Eutelic

post-embryonic growth occurs by each cell growing, not by addition of cells

Arthropoda

-Cephalization

-Open circulatory system

-Jointed appendages

-Segmented body

-Sclerotized cuticle made of chitin

Tagmatization

specialization of body regions for specific functions

*head and thorax often fused as cephalothorax

5 main groups of arthropods

*Trilobita

*Chelicerata

*Myriapoda

*Crustacea

*Hexapoda

Crustaceans

-2 pairs of antennae (compound eyes)

-Cephalothorax

-Hard carapace

-Mandibles

-Gills

Hexapods

-1 pair of antennae

-mandibles

-tracheae

-6 legged

-Tagmatization

-Cerci

-Compound eyes

-ocelli

-Moulting

-Separate sexes

Myriapoda

-Less tagmatized

-3+ pairs of legs

Diplopoda

Millipedes - two pairs of legs per segment

Chilopoda

Centipedes - one pair of legs per segment

*poison claws

Chelicerata

Chelicerae as main mouthparts

Cephalothorax (6 pairs of legs, chelicerae, pedipalps)

Arachnia

-Ocelli

-Fluid feeding predators

-Separate sexes

Araneae

order of spiders

2-segemented chelicerae

0-4 pairs of ocelli

Tracheae and/or book lungs

Spinnerets- (abdominal appendages for spinning silk)

Poison Glands

Silk producing glands

Maternal care

Scorpiones

Pedipalps modified as grasping pincers

Fluid feeders

Poisonous stinger

Acari

mites

no separation between cephalothorax and abdomen

2 or 3 segmented chelicerae

Deuterostomes

2 phyla (Echinodermata and Chordata)

Triploblastic

radial, indeterminate cleavage

Echinodermata

Calcareous endoskeleton

diffuse nervous system

adults have penta-radial symmetry

larvae exhibit bilateral symmetry

broadcast spawning

Echinoidea (urchins)

-No arms

-penta radial

-spines

Astroidea (star fish)

-Water vascular system

-tube feet

-madreporite

Holothuroidea (sea cucumbers)

elongated with secondary bilateral symmetry

deposit feeders

4 synapomorphies of chordates

notochord, dorsal hollow nerve cord, muscular post-anal tail, pharyngeal gill slits

Cephalochordata (lancelets)

-Adult has all the chordate character traits

Urochordata (tunicates)

*Larval stage has all 4 synapomorphies

*Metamorphosis causes loss of character traits

Craniates

chordates with a head (cranium = skull)

Derived character traits of craniates

1. Two or more clusters of Hox genes

2. Neural crest

3. Endoskeleton

4. Circulatory system modified

5. Pharyngeal slits

Myxini (hagfish)

only living craniates that lack vertebrae

cartilage cranium

myxo = slime

Petromyzontida (lampreys)

Eyes with lenses, no jaw

Cartilage skeleton

Primitive vertebral column

Gnathostomes (jawed vertebrates)

Jawed fish evolved

2 pairs of fins evolved

*Further duplication of Hox genes

Origin of teeth

Outside in hypothesis

scales homologous to teeth

Chondrichthyes (sharks, rays)

-early jawed fish

-cartilaginous fish with bony teeth

-Copulation

Oviparous

egg laying

Viviparous

live birth

Ovoviviparous

eggs hatch internally and are birthed later

Bony Fish

originally --> osteichthyes

-skeleton becomes ossified

-paraphyletic

-Ossified endoskeleton

-bony scales

-operculum

-external fertilization

-flexible fins

Lungs and swim bladders

Ancestors had simple lungs and gills

*swim bladder evolved from lungs