Bio exam 4

the founder effect

a small group of individuals separate from a population and start a new population elsewhere

the founder effect example

The amish

• community in PA founded by a small group of german immigrants in 

  • keep marrying w/in their community and social isolation causing genetic mutations like dwarfism 

Bottleneck effect

A large population is suddenly reduced to a smaller group because of a natural disaster/event

bottleneck effect example

• a wildfire kills most of a deer population keeping one gene dominant, speccific coat color, for the next few generations due to reduced genetic diversity in new population

genetic drift

• change in allele frequency between generations due to RANDOM CHANCE

• lowers variation/heterozygosity → large impact on smaller populations

genetic drift example

a severe storm could kill most of the brown-eyed individuals in a small population, leaving a smaller group with a higher frequency of blue eyes, even if brown eyes were previously dominant

Gene flow - migration

opposes speciation

• movement of alleles between populations

• increases variation and heterozygosity

• decreases genetic differences between populations

gene flow example

• a deer from one herd/population mating with a deer from another herd/population

  • offspring now becomes part of new herd’s gene pool

Non-random mating

• individuals with certain traits that are heritable are more likely to mate over others

• sexually selected traits can, but not always, reduce fitness. It makes certain heritable traits more exaggerated if they increase mating likelihood

  • Intrasexual selection: direct competition among one sex for mates (male-male combat)

  • Intersexual selection: “mate-choice” one sex is choosy on who they mate with

• inbreeding

non random mating example

• sexual selection

  • female peacocks choosing males with larger tails

assortative mating

mating wtih similar phenotypes

dissortative mating

mating with different phenotypes

speciation 

the process by which one species splits into two or more 

• through the accumulation of microevolutionary changes leading to macroevolution 

Biological speciation

two populations are the same species if they can interbreed in nature and produce fertile, viable offspring

• emphasis on gene flow to maintain species viability

biological species concept example

• western and eastern meadowlark look nearly identical in appearance but have distinct calls and behaviors that keep them from interbreeding

  • reproductive isolation trait is the key that defines them as separate species

Morphological speciation

two populations that have distinguishable phenotypic characteristics are classified as different species

Morphological speciation example

• difference between sharks and dolphins

  • appears similar due to the environment but are distinctly different species based on their evolutionary history and physical structures

Phylogentic speciation 

species are groups of indivduals that share a unique common ancestor

• emphasis on evolutionary time; good for fossils, not real time

phylogentic speciation

the african elephant split into two species

• african forest elephant and african savanna elephant based on genetic and morphological evidence

ecological speciation

species is a group of organisms who share a commone lineage and fill a similar niche

• emphasis on disruptive selection

Ecological speciation example

distinction between human roundworm and pig roundworm

• appear very similar morphologically

• different species because they occupy different ecological niches and infect different hosts

another example is polar bear and grizzly bear

speciation process

1. Geographic barrier or disruptive selection creates reproductive isolation

2. Reproductive isolation allows for the accumulation of unique gentice differences in a population

3. Genetic Differences enhance reproductive isolation

allopatric speciation

physical geographic barrier reproductively isolating a population

allopatric speciation example

two isolated ponds with different environment conditions

• pond with predators- fish faced a high risk of being eaten by predators → natural selection favored individuals with a body shape that allowed them to escape quickly

• pond w/o predator- main selective pressures were different, related to long-duration of swimming → selection favored a body shape that thrived for long swimming periods

  • outcome: overtime populations in each pond diverged significantly in their morphology and when brough together, females of one fish preferred to mate w/ male fish w/ similar body type

sympatric speciation 

no physical barrier 

sympatric speciation causes

• disruptive selection

• sexual selection

• polyploidy

disruptive selection

reproductive barriers arrive due to microhabitat adaptations, typically temporal barrier

disruptve selection example

maggot flies start laying eggs on new introduced apple trees instead of their original tree. the two trees ripen at different times, so natural selection favored flies that emerged early for the apple and late for the other tree→ causing a split into two host groups

sexual selection

reproductive barriers areise due to mate choice

sexual selection example

male birds of paradise perform dances and display wild feathers to attract females. females pick the males with the most impressive displays. over generations this strong female choice pushed males to evolve even more dramatic 

polyploidy selection

reproductive barriers arise due to chromosomal mismatch

polyploidy selection example

meiosis errors

• chromosomes are duplicated and recombinded incorrectly

  • extra sets of chromosomes

• more common in plants

habitat isolation

prezygotic

• disruptive or the creation of a barrier

  • different phenotypes of a plant species do better in dry or wet habitats and reproduce with only these closest to them

temporal isolation

prezygotic

• different flowering times/breeding seasons

behaviroral isolation

• assortative mating

• songs varying in bird species allow for own species recognition

mechanical isolation

prezygotic

• two species could try to mate with each other but one may be signigcantly larger / their genitals do not mathc

gamate isoaltion 

prezygotic

• successful interspecies mating attempt but the egg will not be fertilized by a sperm from another species 

reduced hybrid viability

postzygotic

• hybrid offspring will not survive

reduced hybrid fertility

postzygotic

• generally healthy hybrid offsprin but it cannot makes its own offspring

hybrid breakdown

postzygotic

• inital hybrid are fertile but as they mate with each other they create unviable offspring

ecosystem services

benefits to humans provided by natural systems and species because they can 

• support life systems on the planet

• provide material resources

• regulate and reduce extreme natural events like diasters

• have a culutral benefit like imporved mental health

ecological organizations

smalles to largest - temporal/spatial

1. individual

2. population 

3. community 

4. ecosystem

5. landscape

6. global

individual

organismal level, traits/anatomy and physiology?

population 

groups of organisms of the same species in the same place 

how is population growth  (abundance) influneced by the evironment

community

group of populations of different species, pred/prey interactions

ecosystem

the interactions between biotic and abiotic systems

landscape

the combination of multiple ecosystems

global

the biosphere

how air circulation affect the climate of different latitudes, etc…

sunlight effect

unequal heating of the earth leading to different heating of air masses

• more concentrated at equator due to the 23.2 degree tilt

• unequal heating creates changes in preceiptation

• unequal heating causes wind patterns

  • unequal heating and wind drive water currents

preciptation

• hadley cells 0-30 (low pressure zones)- warm air rises & gets dense, rains out at equator, air dries and becomes denser (high-pressure zones) and creates deserts

• ferrel cells (30-60) - temperate zones

• polar cells (60-90) 0 dry, cold 

wind patterns 

• coriolois effect- equator spinning faster than the poles causes shifts in wind direction 

  • northern hem → wind deflected right of og direction

  • southern hem → wind deflected lef of og direction

• easterly trade wins → east to west

• westerlies → west to east

anabatic winds

during day, sun heats up the mountain sid, air becomes lighter and travels up the mountain from the valley

katabatic winds

at night the mountain cools down and the air becomes denser and travels down the mountain to the valley

inversion layer

cool air is denser than warm air

wam air on top ov valleu traps the cold air