unit 3

allopatric speciation

occurs when population becomes geographically separated to prevent gene flow - new species evolve to no longer interbreed

types: dispersal, vicariance, founder event

common for new animal species

allopatric - dispersal

barrier removed & part of original population migrates

allopatric - vicariance

occurs when barrier originates where there wasn’t before

allopatric - founder-event

jump dispersal

occurs when part of population gets separated because of disturbance

sexual selection

for mate & breeding

mate choice → difference in appearance between males & females - extreme phenotypes

requirements for sexual selection

high reproduction rate, variation in phenotype traits, traits are inherited, assortative mating based on traits

sympatric speciation

behavioral reproductive isolation(temporal difference in breeding)

sympatric - polypioidy

hybridization or mutation → individuals having different number of chromosomes from parents/others in population

common for new plant species

adaptive radiation

explosive pattern of species originates - new species diverge in ecological function & morphology/phenotype

occurs fast in geologic time

done through innovation or ecological opportunity

ecological opportunity example of adaptive radiation

mammals took on new traits after dinosaurs died - new roles & functions

innovation example of adaptive radiation

notothenioidei fishes develop antifreeze traits to survive & diverse

behavioral reproduction isolation

sexual selection, breeding at different times

extirpation

death of individuals of a population - local

extinction

death of all individuals of a species - all populations

mass extinction events

end-ordovician, end-devonian, end-permian, end-triassic, end-cretaceous

over go 40% extinct, eliminated pelagic animals & small animals

background extinction

restricted species go extinct

extinctions outside of events

kill mechanisms

process hypothesized to cause a mass extinction event

ex: asteroid killing dinosaurs → impact winter blocking sunlight → prevents photosynthesis → herbivores died → omnivores & carnivores died

helen tappan

one of first paleobiologists to hypothesize extinction causes

extinction selectivity

differential extinction of taxa based on traits & abilities

effects of modern extinction threat

eliminated larger bodies & able to move

extinction info

low reproduction → more vulnerability

higher rates in tropics

ordovician mass extinction

440 million years ago

severe drop in taxonomic diversity but not functional

little change in ecosystem structure

devonian mass extinction

370 million years ago

severe drop in taxonomic & functional diversity

reefs disappeared & took 200 million years to come back

georges cuvier

father of paleontology

argued fossil record was evidence of cyclical & abrupt revolution in animal evolution - catastrophes

charles lyell

father of geology

argued that the same geological processes shaped earth today

accepts extinction but rejects cuvier’s idea of catastrophe

charles darwin

proposed theory of evolution by natural selection

implied extinction happens but gradual process

norman newell

father of paleobiology

advances in geological time & fossil records argued extinction is gradual process

luis & walter alvarez

1980

asteroid impact hypothesis for end-cretaceous mass extinction

extinction can be random & unfair

conservation genetics

assisted migration to new areas where species will be more likely to survive future climate

speeds up genetic adaption using existing variation

goal: keep current species from extinction

de-extinction/resurrection biology

introduction to species back to original regions extirpated from

engineered genetic adaption by adding new genetic variation(needs reliable DNA, full genome)

goal: restore traits & functions lost with extinction(resemble extinct organisms that can survive in modern ecosystems)

aspects of species trying to resurrect

traits, genes(original DNA with information for goal traits), & behavior

de-extinction genetic techniques

back-breeding, cloning, & genetic engineering

back-breeding

concentrate ancestral traits that still exist in population into individual organism by selective breeding

only resurrects trait

example of back-breeding

aurochs - wild ancestor of domestic cattle

their genes & traits exist in different breeds of domestic cattle

used active breeding, passive breeding, then rewilding

goal: benefits open areas with grazing, protects small animals

cloning

makes genetically identical individuals of extinct species using nuclear DNA from somatic cells

fuse eggs with closely related living species that have also been recently extinct

disadvantages: declines population health & viability because of high risk of inbreeding & gene mutation

process - sheep(dolly) via surrogate

1977, 277 trieds

cells from genetic donor were multiplied

egg & DNA harvested from different breed of sheep

nucleus from genetic donor fused with empty cell of egg donor

recombined cell → embryo → implanted for pregnancy

failed cloning

pyrenean ibex - skin biopsy to preserve cells & DNA but clone died

cloning successes

not extinct

presewalski horse(surrogate), black-footed ferret(old cell samples)

genetic engineering

edit genes in living species to make similar to extinct relatives

CRISPR

precise gene editing tool

genetic engineering needs

preserved gene sequence from extinct species & close relatives(produce offspring with desired phenotypes)

genetic engineering goal

restore “core genes” true to live & species with disease resistance & climate adaptations to restore habitats

de-extinction: mammoths

why: preserve arctic grasslands to prevent permafrost melting

how: elephants & CRISPR - create hybrid embryo with asian elephant & use african elephant(large) for surrogate

de-extinction: dire wolf

2025 - 3 born

how: DNA from 13,000 year old tooth & 72,000 year old skull to edit grey wolf cells

theory of island biogeography

mathematical theory

used to understand biogeographical problems & apply for lang management decisions

theory: larger islands host more species than smaller ones(low extinction rates), islands close to mainland will be more diverse than distant ones(low extinction rates & large colonization rates)

species-area effect

large islands host more species because wider the area, the more species; larger geographical region, the more different ecoregions

explains: numbers of species on different carribbean & global ocean islands

metapopulations

isolated population that occupies habitat patches & individuals can move between

immigration rate

amount of individuals going from source to sink(core satellite dynamic)

source population

dense, big patch

patch of high reproduction to sustain & not go extinct

example: mainland

sink population

small patch

patch of insufficient reproduction rate to keep population from going extinct

sustains population from source

example: island

rescue effect

closer the island, easier for individuals to reach island & boost population to prevent extinction

ways to disperse to islands

swim, fly, float, raft on veg/logs/animal that flies or swims

island immigration rate vs species richness

many species on island → not many new species - higher if island is near

island extinction rate vs species richness

many species on island → high competition for resources(limited) - competitive exclusion → high local extinction - higher on small island

equilibrium species richness

average number of new species arrive each year equals average number of extinct

how to determine amount of species present - species richness

number of species originated

number of species extinct

number of species disperse into/out

latitudinal biodiversity gradient(LBG)

identifies patterns of more species near equator regions

geographical area hypothesis

tropics are largest biome → species have larger geographical range → more chances at allopatric species

higher speciation

energy availability

more direct solar energy → more available energy → more primary production → more individuals survive

low extinction

evolutionary speed hypothesis

higher average temperatures → faster growth & shorter generational times

high mutation → high speciation(fast)

tropics are a cradle

specialist species survive better in stable climates → more species coexist since niches are separate and minimize competition 

high speciation

tropics are a museum

fluctuating & harsh conditions → kill mechanisms(not at equator)

low extinction rates

out of the tropics

tropics are a cradle & museum → high speciation & species geographic range include equator & nearby areas

high speciation & low extinction

climate variability/stability

colder winters far from equation(species are adapted) & colder as you go up mountains(species can survive climate across mountains)

high speciation

patterns for high speciation rates near equator

geographical area, evolutionary speed, tropics are a cradle, out of tropics, climate variability

patterns for low extinction rates near equator

energy availability, tropics are a museum, out of tropics