VB Exam 1

when did vertebrates evolve?

540 mya

5 characteristics of vertebrates

1) serially arranged vertebrae

2) cranium

3) mineralized tissues

4) multichambered heart

5) muscularized gut tube

major vertebrate groups

fish, tetrapods (amphibians, amniotes (sauropsids + synapsids))

biodiversity

total amount of variation of life forms in a particular area or type

natural selection

differential survival due to phenotype

3 components of biodiversity

1) species richness

2) genetic variability

3) habitat availability

species

group of interbreeding individuals that share ancestry and have evolved independently

biological species concept

groups of interbreeding natural populations that can only reproduce with themselves

gene flow

transfer of alleles from populations

4 step process of speciation

1) barrier to gene flow

2) geographic + reproductive isolation

3) ecological divergence

4) reinforcement

reinforcement

selection against hybrids, stabilizes reproductive isolation

pre-mating isolation mechanisms

ecological, temporal, physiological, mechanical diff that prevent species from mating

ex: ecological pre-mating

different habitats

ex: temporal pre-mating

different mating season

ex: physiological pre-mating

different chemical cues

ex: mechanical pre-mating

different shape of organs

post-mating isolating mechanisms

chemical/developmental cue that prevent gametes from producing viable offspring

post-mating example

hybrid mules are sterile

problems with the biological species concept

can’t be extinct, asexual, or hybrid

phylogenetic species concept

species are branches on a phylogenetic tree

how are species defined in a phylogenetics?

groups of organisms whose members share a common ancestor

advantages of phylogenetics

can be applied to fossils, sexual + asexual, accurately reflects what taxonomists do

problems with phylogenetics

where to draw the line? and not very established

phylogeny

evolutionary history of a group

tips

terminal end of evolutionary tree

branches

lineages

nodes

where lineages split

clade

an organism and all of its decendants

root

ancestor

sister taxa

lineages that share an ancestor

synapomorphy

shared dervied characteristics

homology

similar characteristics due to common ancestor

symplesiomorphy

shared characteristics ancestral to a group but not defining

How do you know what the best phylogeny is?

principle of parsimony (simplest one)

monophyletic group

common ancestor and all its descendants

paraphyletic group

common ancestor but not all descendants

homology vs homoplasy

shared ancestry vs not

convergent evolution

independent origin of similar traits

parallel evolution

diverged recently develop similar things

evolutionary reversal

reversal of derived character state

5 synapomorphies of chordata

1) dorsal nerve tube

2) notochord

3) segmented post-anal tail

4) endostyle

5) gill slits

cephalochordata (lancelets)

burrowing adult stage, gill slits used for filter feeding

wheel organ

moves water over gill slits in lancelets for filter feeding

urochordata (tunicates)

tadpole like larvae but sessile adults

chordata subphyla

cephalochordata, urochordata, vertebrata

major groups of jawless vertebrates

cyclostomes, ostracoderms, conodonts

myxiniformes (hagfish)

scavengers on ocean floor, barbels around mouth, mucus

petromyzontiformes (lampreys)

teeth on tongue, flow through + tidal ventilation

conodont

known from teeth-like fragments,

tully monster

eyes group them as possible cyclostome

“ostracoderms”

paraphyletic, dermal plate

key synapomorphy in jawed vertebrates

ribs and vertebrae

What gave rise to vertebrate development?

Hox genes

fin fold theory

not true bc they don’t have fossil evidence

somites

give rise to vertebrae, dermis, and muscle

lateral somatic frontier

separate tissue layers in embryos

functions of medial fins

control roll and yaw

functions of paired fins

control pitch and brakes/thrust

pharyngula stage

where vertebrate embryos have similar features

branchial/gill arches

support gills

what does the jaw develop from?

mandibular arch

hyoid

supports the jaw

how did lengthening of the braincase help the origin of jaws?

provides space to form the jaws

pharyngeal jaws

second jaw to crush food

ventilation hypothesis

enlargement of mandibular arch for respiratory purposes

What is an exaptation of jaws?

biting and handling food

exaptation

trait that arises for one function but is then used for another

adaptive radiation

rapid diversification of related species

did development of jaws cause extinction of “ostracoderms”?

no, mass extinction did

placoid scales are modified ____

dermal bone

Why don’t sharks need to drink water?

their blood is hyperosmolar so blood flows into their body

Holocephalii unique jaw

fused jaw to forage on bottom

Elasmobranchii

sharks, skates, and rays

skates and rays scales

absent for more flexibility

Osteichthyes

grandma of tetrapods, bony fish

bony operculum

covers gills to prevent backflow

Branchiostegal rays

curved bones to support the gills

lineages of bony fish

Sarcopterygii and Actinopterygii

Actinopterygii

ray finned fish, homocercal tail, less fish fingers

Polypteriformes

bichirs

Acipenseriformes

sturgeons + paddlefish, evolved cartilaginous skeleton

Lepisosteiformes

gar

Amiiformes

bowfin, evolved suction feeding

Teleosti

more successful vertebrate radiation

hot water = ____ O2

less

Why do fish need to get creative with oxygen?

water is more dense, viscous, and less oxygen

gill filaments

respiratory part of gills coming off arches

secondary lamella

where gas exchange happens

countercurrent exchange

blood moves opposite of water, partial pressure causes constant passive O2 diffusion

buccal pumping

use branchial arch muscles to force water out of gills

ram ventilation

open water fish, passive

labyrinth

vascularized chambers in rear of head (betta)

what keeps the gas in the bladder?

woven collagen fibers

pressure decreases = swim bladder ____

expands

Physostomous fish

pneumatic duct, direct connection between gut + bladder, gulp air at surface, use when gills do not have enough oxygen

Physoclistous fish

gas secreted into bladder

rete mirabile

complex of capillaries extracting o2 from blood to bladder

gas gland

acidifies blood and causes hemoglobin to release o2

ovale

muscular valve that releases o2 into blood

fish swim forwards by _____

pushing backwards on water