Bisc-120 Midterm 2

10/16, content from lectures 11-20

speciation

process in which a species splits into 2 or more distinct species, creation of new species

biological species concept

members have ability to reproduce and will produce viable/fertile offspring

reproductive isolation

species are separate because they cannot reproduce

prezygotic barriers

mechanism that prevents two species from mating/prevents fertilization if they do mate

post zygotic barriers

mechanism that prevents zygote from developing into viable/fertile adult, even if initial mating is successful prevents lineage from continuing

habitat isolation

prezygotic barrier

habitat isolation

species do not encounter each other due to living in different geographic area/habitats

ex. water garter snake vs. land garter snake

natural selection

the gradual adaption of a species to its enviroment

microevolution

the change in a population’s gene pool from one generation to the next

temporal isolation

species mate at different times of day/time of year

ex. eastern spotted skunk breeds in late winter, eastern spotted skunk breeds in fall

behavioral isolation

species will not mate due to having different courtship rituals

ex. birds perform elaborate and specific courtship rituals, similar species of birds with different courtship rituals will not mate

mechanical isolation

species are physically incompatible

ex. plants with different pollinators will never fertilize each other,

clockwise/counterclockwise snails

gametic isolation

egg/sperm will not fertilize eachother

ex. plants that release pollen into air cannot fertilize every nearby plant

temporal isolation

prezygotic barrier

behavioral isolation

prezygotic barrier

mechanical isolation

prezygotic barrier

gametic isolation

prezygotic barrier

objections to biological species concept

doesn’t apply to asexually reproducing species, cannot be determined for fossil record, sometimes morphologically or ecologically distinct species CAN mate (grizzly/polar bears)

reduced hybrid viability

hybrids have development issues, won’t survive long enough to reproduce

ex. salamanders

hybrid

offspring of two distinct species

reduced hybrid fertility

hybrids are viable, but infertile

ex. mules

ring species

species which forms a “ring” due to geographic isolation, species separates into two reproductively incompatible species then rejoins and is able to reproduce

ex. west coast salamanders around the central valley

hybrid breakdown

F1 generation is viable AND fertile, F2 generation is not viable and/or not fertile

ex. most commercially sold vegetables, tomatoes

morphological species concept

species are defined by physical similarity

objections to morphological species concept

subjective, genetic data can conflict with physical observations (ex. dogs), phenotypic plasticity

ecological species concept

species defined by ecological niche, theory that if two species occupy same niche they will compete, species is adapted to its enviroment

ecological niche

role a species serves in environment (habitat, what it does, what it eats)

speciation event

where a species splits

allopatric speciation

geographic/physical isolation leads to speciation

ex. snapping shrimp split on either side of panama when isthmus formed

peripatric speciation

a type of allopatric speciation associated with a bottleneck event

sympatric speciation

speciation without a physical barrier

polyploidy

cells contain more than 2 complete sets of chromosomes, happens from mistake in cell division

ex. most plants species are derived from this, more common in plants because of self-fertilization

allopolyploidy

polyploidy where chromosomes are from multiple species, first requires two distinct species to fertilize, then chromosomes must somehow be doubled

hybrid zones

when separate species with common ancestry are reintroduced

reinforcement

possible result of hybrid zone: morphology of the two species becomes more distinct over time, hybrids are less viable

fusion

possible result of hybrid zone: two species reform into single species

ex. fish in lake victoria bc pollution is changing visibility of color in the water

stability

possible result of hybrid zone: some gene flow/hybrids may happen but species generally remain separate, most common result

gradualism

model that speciation happens slowly through small changes over time

punctuated equilibrium

model that indicates infrequent & abrupt speciation, supported by the fossil record

theories on origin of life

atmosphere, meteors, hydrothermal vents

phylogenetic tree

diagram that shows branching of species & evolutionary relationships between taxa

phylogeny

evolutionary history of a species or a group of related species

systematics

study of & classification of organisms/evolutionary relationships

Carl Linnaeus

creator of binomial nomenclature and taxon classification system

binomial nomenclature

two part name of species: genus + specific epithet

taxon (plural: taxa)

group of species ordered from most general to most specific

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

branch points

where species diverge from common ancestor

sister taxa

groups which share an immediate common ancestor not shared by any other group

rooted tree

phylogenetic tree which contains most recent common ancestor of all included taxa

basal taxon

taxon that diverges early in history, only distantly related to other included taxa

homology

phenotypic/genetic similarity as a result of common ancestry

analogy

similarities without common ancestry, result of convergent evolution

convergent evolution

unrelated lineages produce similar characteristics because of similar selective pressures

homoplasy

a characteristic that is a result of convergent evolution

cladistics

a method of grouping organisms based on common ancestry

clade/monophyletic group

a group with 1 common ancestor and ALL of its descendants

paraphyletic group

a group with 1 common ancestor and some but not all of its descendants

polyphyletic group

a group of related species without their most recent common ancestor

shared ancestral character

shared character within a group that originated from a common ancestor

ex. backbones among all vertebrates

shared derived character

shared character unique to a particular clade

ex. hair is shared only by mammals within the larger category of vertebrates

ingroup

group of species being studied

outgroup

species closely related to ingroup

distance analysis

method of estimating amount of time/amount of genetic changes since divergence, counts # of differences/similarities between 2 points in DNA sequences

maximum parsimony

method of estimating amount of time/amount of genetic changes since divergence that assumes fewest possible number of evolutionary events

orthologous genes

genes in different species which evolved from a common ancestor, usually performs similar functions, split originated from speciation event (type of homologous gene)

paralogous gene

genes in same genome/species which evolved from common ancestor, usually performs different functions, split originated from gene duplication (type of homologous gene)

molecular clock

estimation of constant rate of evolution

neutral theory

evolutionary theory that suggests most mutations provide no advantage or disadvantage & are therefore not influenced by natural selection

objections to molecular clock/neutral theory

evolution does not happen at constant rate, natural selection exists, can’t estimate divergences older than the fossil record

geologic time scale/geologic record

a timeline of earths history split into eons, eras, periods, and epochs

the anthropocene

the period since the industrial revolution in which humans have been the driving force rapidly changing the earth (1750-)

stromatolites

oldest known fossils, layers of bacteria & sediment

oxygenic photosynthesis

photosynthesis which produces oxygen, began about 3 bya

the oxygen revolution

when free oxygen first filled the earth’s atmosphere and oceans

endosymbiont

a cell that lives within a host cell

endosymbiosis

the process by which endosymbionts form

serial endosymbiosis theory

a theory that mitochondria evolved through endosymbiosis

karyogenic hypothesis

hypothesis that the nucleus formed slowly through internal segregation

endokaryotic hypothesis

hypothesis that the nucleus formed through endosymbiosis

mass extinction

large # of species goes extinct at once

Permian mass extinction

96% of marine animals went extinct, volcanic activity in Siberia put CO₂ into atmosphere—> caused global warming & ocean acidification

Cretaceous mass extinction

asteroid impact wiped out the dinosaurs, dinosaurs were already in decline

adaptive radiation

rapid evolution of a single ancestral species into many new species filling ecological niches

autopolyploidy

polyploidy where chromosomes are from a single species

RNA world hypothesis

self-replicating RNA molecules were the primary precursors to all life on Earth (not DNA)

evidence for RNA world hypothesis

RNA can store genetic information and some RNA molecules (ribozyme) can catalyze

reactions

ribozyme

An RNA molecule that can catalyze reactions much like a protein enzyme

3 domains of life

Bacteria, archaea, eukarya,

horizontal gene transfer

movement of genes from one genome to another

cell wall

outer structural layer that maintains cell shape

peptidoglycan

makes up bacteria cell walls (not in archaea or eukaryotes)

gram stain

method of identifying bacteria via staining peptidoglycan in cell wall

gram-stain positive

simple cell walls, lots of peptidoglycan, antibiotics are more effective

gram-stain negative

complex cell walls, less peptidoglycan, more likely to be pathogenic and antibiotic resistant

glycocalox

sticky polysaccharide/protein layer coating gram-negative bacteria, allows bacteria to adhere to surfaces

prokaryotic domains

bacteria & archaea

cocci

bacilli

spirochete

antibiotics affect on gram-positive bacteria

inhibit synthesis of links in peptidoglycan