Bio Exam 3

causes of divergence

mutation, selection, genetic drift

biological species concept

main criteria for a species is reproductive isolation

Gradual process with no gene flow

disadvantages of biological species concept

doesn’t work for fossils, species that reproduce asexually, and pops that don’t overlap geographically

prezygotic isolating mechanisms

temporal, habitat, behavioral, gametic, and mechanical isolation

temporal isolation

breed at different times

habitat isolation

breed in different habitats

behavioral isolation

different mating rituals

gametic isolation

sperm/egg incompatibility

mechanical isolation

reproductive structures are incompatible

postzygotic mechanisms

hybrid validity and hybrid sterility

hybrid validity

embryo do not fully develop

hybrid sterility

heterogametic sex is sterile

morphospecies concept

main criteria for species is morphological traits

widely applicable

disadvantages of morphospecies concept

polymorphic species may be labeled as different species

hard to identify species that differ in non morphological traits

phylogenetic species concept

main criteria for species is evolutionary history

allopatric speciation

populations become geographically isolated

more common mode of speciation

allopatric speciation: dispersal

a population moves and colonizes a new area

allopatric speciation: vicariance

the habitat physically splits

parapatric speciation

when populations change gradually along a cline

cline

spatial gradient of character change in an environment

sympatry

living in the same geographic area

sympatric speciation

caused by an external event (disruptive selection) or an internal event (chromosome mutation)

niche

the range of resources a species can use and the conditions it can tolerate

polyploidy

an error in meiosis or mitosis that results in more than 2 sets of chromosomes

can polyploidy cause speciation?

yes

autopolyploid mechanism

nondisjunction during meiosis, 4n

autopolyploid

doubling of chromosome #

reproductively isolated from original population

instantaneous speciation

allopolyploid mechanism

error in mitosis prior to meiosis, 2n=10

allopolyploid

different species parents

viable offspring

offspring have 2 copies each of 2 sets of chromosomes

advantages of being a polyploid

higher level of heterozygosity

can tolerate higher level of self-fertilization and inbreeding

genes on duplicated chromosomes can diverge independently

speciation by polyploidization

driven by chromosome level mutation and occurs in sympatry

virtually instantaneous

what enabled the rapid diversification of plants?

genetic diversity of polyploids

when can population interbreed and converge?

when theres no prezygotic isolation

reinforcement

natural selection for traits that prevent interbreeding among populations (prezygotic isolating mechanisms)

hybrid zones

a geographic area where interbreeding between 2 populations occurs

can be stable or moving, small or big

outcomes of secondary contact between populations

fusion of pops

reinforcement

hybrid zone formation

extinction of one population

homology

trait due to common ancestry

homoplasy

similarity not due to common ancestry

synapomorphy

shared derived trait

monophyletic group (clade)

ancestor and all descendents

paraphyletic group

ancestor but not all descendents

polyphyletic group

not all ancestors and not all descendents

complications inferring trees

traits may be similar due to homoplasy

a reversal in character change may occur

some groups are based on one trait while other groups use another trait

parsimony

tree with the least amount of evolutionary changes

most logical tree

DNA sequencing

used by most scientists to determine phylogeny

using DNA to determine phylogeny

identify homologous region (conserved gene)

align sequences

compare differences

which are more common: transitions or transversions

transitions

molecular clock

DNA and protein sequences evolve at a relatively constant rate

can be used to date nodes

relies on natural theory

intact fossil

when decomposition does not occur and organic remains are preserved

compression fossil

sediments accumulate on top of remains and compress organic materials into a carbonaceous film

cast fossils

hole in organism fills with minerals that create a cast

permineralized fossils

remains decompose slowly as minerals fill the open space

trace fossils

preserved paths of animals

how to determine fossil age

nearby rock layers

ideal conditions for fossils

organism is buried quickly and decomposes slowly

fossil record

total collection of fossils found in the world

limitations of fossil record

habitat bias

taxonomic bias

temporal bias

abundance bias

fossilization habitat bias

organisms that live where sediment is actively being deposited are more likely to fossilize

fossilization taxonomic bias

organisms with hard parts are more likely to fossilize

fossilization temporal bias

more recent organisms are found more often

fossilization abundance bias

more abundant organisms are found more often

burgess shale

canadian rockies, 508 mya

cambrian explosion

lots of soft bodied organisms

olduvai gorge

tanzania, 2 mya

human evolution fossils

when was earth created

4.6 bya

when did life start

3.5-3.8 bya

precambrian

creation of earth - appearance of most animals (543 mya)

life is unicellular until the end of this period

absence of oxygen until evolution of photosynthetic bacteria (2 mya)

phanerozoic eon

end of precambrian - present

paleozoic, mesozoic, cenozoic

paleozoic era

543-248 mya

appearance of most major lineages

diversification of life

ends with mass extinction

when do land animals first appear?

paleozoic era

which era had the first bony fish, insects, and land plants?

paleozoic

mesozoic era

250 - 66 mya

dinosaur era

ends with cretaceous extinction

which era had the first mammals and angiosperms?

mesozoic

cenozoic era

66 mya - present

mammals and angiosperms abundant

modern animals appear

adaptive radiations

rapid production from a single lineage into many species

needs ecologic opportunity and/or evolution of a key morphological trait

favorable environment for diversification

lots of new niches

cambrian explosion

first animals (sponges) 635 mya

50 mil years later, animals become more complex

triggers of the cambrian explosion

higher oxygen levels

evolution of predation

more niches

hox genes

mass extinction

at least 60% of species die within 1 million years

there have been 5

5 mass extinctions

ordovician

devonian

permian

triassic

cretaceous

end-permian extinction

largest mass extinction

90% of species died

end of paleozoic

causes of permian extinction

lava flood added a ton of CO2, O2, and heat

caused severe acid rain that devastated plants

widespread cole fires released toxic ash

oceans became anoxic (lack oxygen)

sea levels dropped dramatically

end-cretaceous extinction

asteroid struck the earth 66 mya

ended 60-80% of species (most dinosaurs)

6th mass extinction

precipitated by humans

estimated current extinction rate is highest since the asteroid

3 domains of life

bacteria

archaea

eukarya

diversification of the 3 domains

horizontal transfer was crucial for eukaryote evolution

(mitochondria and chloroplasts)

archaea

single celled organisms like bacteria

anaerobic

live in diverse habitats like soil and ocean

extremophiles

bacteria

more diverse than archaea

mostly unicellular

diverse habitats, more moderate conditions

cynobacteria

photosynthetic bacteria

abundant in aquatic habitats

what was responsible for the initial increase in atmospheric O2?

cynobacteria

where did eukaryotes get their chloroplasts from?

cynobacteria

proteobacteria

very diverse phyla of bacteria

wide variety of pathogens

nitrogen fixation in plants

where did eukaryotes get their mitochondria from?

proteobacteria

evolution of land plants

moving from water gave them more CO2 and O2

moving also made a lack of water and support, and made reproduction more difficult

ancestor of plants

photosynthetic protist (algae)

adaptations of land plants

alternation of generations (diploid sporophyte, haploid gametophyte)

sporophyte embryo protected

produce spores that can handle tough environments

order of evolution of plants

vascular → nonvascular → vascular with seeds

bryophytes

simplest land plants

moss, liverworts, hornworts

no roots, stems, or leaves

live in moist environments

vascular plants main organs

stems, roots, and leaves

xylem

water and mineral transport from the roots up

phloem

two-way flow of water and food