Classification - a way of characterizing animals

What is the 1st division of animals?

Vertebrates and Invertebrates

what is the 2nd classification of division?

number of cells

• metazoa

• protozoa

metazoa

multicellular, development from blastula

protozoa

unicellular or acellular, not from blastula

are protozoa animals?

No

What is the 3rd characteristic that further divides Metazoans?

complexity of tissues

• parazoa

• eumetazoa

parazoa

no “true” tissues and no organs (sponges and placozoans)

Eumetazoa

with organs, mouth, and digestive system

What is the 4th characteristic that further divides Eumetazoans?

Body symmetry

• radiata

• Bilateria

Radiata

radial symmetry

Bilateria

bilateral symmetry (at least larvae)

• defined anterior and posterior ends; dorsal/ventral surfaces

• may exhibit cephalization

cephalization

the congregation of nervous tissue and nerves in one area (a head)

Cross-section

a cut that divides anterior from posterior

frontal

divides ventral + dorsal

Sagittal

divides left from right (plane of symmetry in bug)

What is the 5th characteristic that further divides Eumetazoans?

number of germ layers

• triploblastic

• diploblastic

germ layers

embryonic cell units that give rise to tissues/organs

ectoderm

outer covering, nervous system, gives rise to epidermis

endoderm

inner layer, digestive tract

mesoderm

middle layer, other structures, gives rise to muscle, bones, and circulatory structures

triploblastic

3 layers

diploblastic

2 layers

• outer = ectoderm

• inner = endoderm

What is the 6th characteristic that divides triploblastic animals?

body coelom

• acoelomates

• pseudocolomates

• coelomates

acoelomates

lack body cavity

Pseudocoelomates

have fluid-filled cavity

• forms between mesoderm and endoderm via blastocoel

• internal organs free within coelom

blastocoel

open space that forms within blastula

coelomates

fluid filled and fully lined with mesoderm

• internal organs are not free, lined with peritoneum

Schizocoely (Protosomes)

mesoderm splits, gradually enlarges

Enterocoely (Deuterosomes)

archenteron evaginates (coelomic pouches), enlarges

What are the advantages of having a body cavity?

• organs can expand and contract (heart + gonads)

• locomotive more effective

gastrulation

embryonic ball of cells that invaginates forming gastrula

• has an opening called the blastopore

protostomes

blastopore develops into mouth

• spiral cleavage (rotation in cleavage)

• determinate cleavage (fixed cell fate)

• schizocoely

deuterostomes

blastopore forms anus

• radial cleavage

• intermediate cleavage (can develop identical twins if split)

• enterocoely

Order of development

zygote → cleavage → 8 cell stage → blastula (hollow ball) w/ blastula inside → gastrulation → 3 germ layers form

How do we tell the relation of organisms?

marker genes (DNA) that are conserved and ubiquitous

• ex: 18sSU rRNA (nuclear gene) and CO1 (mitochondrial gene)

what is the marker gene process?

DNA extraction → amplification (PCR) → sequencing → alignment → compare nucleotide sequences

Higher order classification

domain → kingdom → phylum → class → order → family → genus → species

3 domains

• bacteria

• archea

• eukarya

Kingdoms in archea

prokaryotes

• bacteria like organisms

kingdoms in bacteria

prokaryotes

• more recent bacteria

kingdoms in eukarya

all other organisms

• protists (multiple kingdoms)

• kingdom fungi

• kingdom plantae

• kingdom Animalia

Protists (multiple kingdoms)

protozoans, microalgae, macroalgae

kingdom fungi

molds + yeasts

kingdom plantae

multicellular (autotrophic)

kingdom Animalia

multicellular (heterotrophic)

How do we determine relationships, and group animals with common ancestors?

construct dendrograms and phylogenetic trees

monophyletic groups

groups that contain common ancestor + all descendants

paraphyletic group

includes the common ancestor and some but not all decendents (ex: invertebrates)

polyphyletic group

multiple lines of ancestry (ex: flying animals)