M1 Flashcards
prezygotic barriers
prevent mating or fertilization if mating occurs
postzygotic barriers
prevent hybrid zygote from developing into fertile adult or their offspring from reproducing
genetic incompatibilities maintain species boundaries
* some proportion of offspring are less fit
types of prezygotic barriers
- temporal isolation
- behavioral isolation
- mechanical isolation
- gametic isolation
- habitat isolation
- geographic
- ecological
reproductive barriers
- prezygotic barriers
- postzygotic barriers
habitat isolation
prezygotic barrier: occupying different habitats ➞ never come into contact
1. geographic: lions & tigers
2. ecological: diff levels of same habitat
* fish who live at diff levels of same lake
temporal isolation
prezygotic barrier: breeding at diff times
- ex: corals gametes dont come into contact b/c 1 hr diff in spawing
behavioral isolation
prezygotic barrier: do not recognize each other as potential mates
- mating calls or dances
- ex: fireflies’ light patterns
mechanical isolation
prezygotic barrier: physiological diff preventing copulation
- ex: dragonfliy genetalia or snail’s shell
gametic isolation
prezygotic barrier: sperm cannot fertilize egg
- species-specific protein recognition
- ex: purple & red urchin habe jelly coat surrounds egg w/ compounds that recognize specific proteins ➞ sperm needs specific proteins to enter coat & diff ones to enter egg
types of postzygotic barriers
- reduced hybrid viability
- reduced hybrid fertility
- hybrid breakdown
reduced hybrid viability
offspring don’t complete development or have low survivorship
- ex: yellow-belly & fire-belly toads’ hybrid offspring have low embryonic development & malformed jaws ➞ don’t eat ➞ cannot survive
reduced hybrid fertility
can make viable offspring but infertile
- ex: horse + donkey ➞ mule b/c diff # of chrom
hybrid breakdown
offspring are viable & fertile but their offspring are inviable or sterile
- ex: toad hybrid ➞ 75% survive backcross ➞ very few live to adulthood
- hybrid cross ➞ hatchlings but no tadpoles or adults
microevolution
w/in species ➞ changes in freq of gene variant across gen
- small-scale changes
- short time-frame
macroevolution
speciation ➞ accumulation of many microevolutionary changes resulting in new groups
* long-scale changes
* LONG time-frame (geographic time-scales)
taxa (taxon)
group of org on a phylogenic tree
sister taxa
most closely related on a phylogenic tree
* don’t assume that taxa close together are most closely related
branch point
where 2 diff taxa diverge on a phylogenic tree
clades
monophyletic clade
groups of taxa
a group that includes all taxa descended from a specific common ancestor
* can make 1 cut ➞ cut off 1 branch
speciation vs extinction
speciation: creating new lineages
* barrier to gene flow ➞ genetic divergence ➞ reproductive isolation
extinction: removing branches, loss of lineages
modes of speciation
- allopatric - vicariance
- allopatric - founder effect
- parapatric
- sympatric
allopatric speciation - vicariance
geographic separation into separate pop through physiological barrier means species cannot physically come into contact and no gene flow gives rise to new species
- ex: tectonic plates & penguins
- ex: oxbow lakes formations
allopatric speciation - founder effect
small group of indiv separate from original pop & become geographically separate ➞ pop diverge & become reproductively isolated
* ex: european starlings (geographical isolation)
* ex: snails on diff islands have opposite habddeness so cannot mate (mechanical isolation)
parapatric speciation
part of pop moves into new pop still connected to original pop
envir gradient
* envir gradient
* extension of range
* ex: zinc mine grass (habitat & temporal isolation)
* bird ring species can recognize neighbors mating call but not others’ (behavioral)
sympatric speciation
species diverge in same geographic location ➞ species ranges overlap
* new niche forms w/in pop & indiv in new niche diverge
* ecological habitat isolation ➞ ex: limnetic fish at diff levels of the lake
* insects on adjacent host plants
ex: hawthorn insect vs apple insects ➞ ecological isolation but also temporal isolation because diff fruiting time
fastest speciation occurs with
- rapid reproductive isolation
- shorter lifespan = faster generation time = faster speciation
- specialist pollinators
- sexual dimorphism
- low dispersal ability
- terrestrial org
- polyploidy
specialist vs generalist pollinators
specialists only pollinate one specific type of flower ➞ barrier to gene flow ➞ faster speciation
* specific pollinator shape (niche) ➞ rapid reproductive isolation ➞ speciation
* insect herbivores must develop specific adaptations for plant materials & toxins ➞ once developed for 1 plant hard to develop for others
sexual dimorphism
groups with higher sexual dimorphism have faster speciation & more species
* species w/ sexual dimorphism have choosy mates
* some indiv has novel characteristic that is more attractive ➞ makes a new species
* species that are more dimorphic have more non-random mating
without ➞ less likely to have choosy mates based on secondary sexual characteristics
dispersal ability
groups with small wings have higher speciation rates ➞ can only go so far ➞ less gene flow
aquatic vs terrestrial
higher speciation in terrestrial systems
➞ ocean has fewer physical barriers for gene flow
evolutionary radiation
when rapid speciation results in a burst of new species from a single lineage
adaptive radiation
burst of speciation occurs b/c a group of species adapts to new ecological niches
- form of evolutionary radiation
- ex: island introduction & european finch ➞ adapted to specific diets
- variation in envir & narrow specialist abiotic range ➞ able to diversity into many species
- ex: cali tarweed aparted to abiotic niches: elevation & precipitation
- ex: anolis lizards partitioned single habitat in hawaii
- allopatric speciation btwn islands
- sympatric speciation w/in 1 island ➞ artitioning habitat on same island
polyploid speciation
non-disjunction results in uneven # of chrom ➞ unable to perform meiosis ➞ infertile
competition
both species are harmed
(even better competitor)
amensalism
one species is harmed and the other is neither benefited nor harmed
* short-lived ➞ harmed species will just avoid
commensalism
facilitation
one species benefits and the other is neither benefited nor harmed
predation
parasitism
herbivory
one species benefits while the other is harmed
mutualism
both species benefit
symbiosis
an interaction btwn species living on/in one another
* can both negatively & positively affect a species’ realized niche
* positive symbiosis can raise K ➞ helping access resources more efficiently
* ex: mycorrhizae & N fixation
* negative symbiosis can lower K
* ex: parasite or disease reduces to density low enough that pathogen isn’t spread btwn indiv
+/− interactions influences on realized niche
- realized niche is reduced compared to fundamental niche ➞ predator could occur in more places but doesn’t given the species interactions
- realized niche is expanded compared to fundamental niche ➞ species help attain nutrients/water ➞ can now live in previously intolerable envir
+/− interactions influences pop regulation (growth dynamics)
negative interactions can lower K
- ex: dis or parasite reduces K to density low enough that pathogen isn’t spread btwn indiv
positive interactions can raise K
* ex: mycorrhizal partner helps plant access resources more efficiently
reciprocal density dependence
predictable changes in predation, survival, etc produce predictable oscillations in pred & pop sizes
lotka-volterra model
prey: change in victim pop size through time = prey growth rate - death of prey due to predator (predation rate × predator pop size)
* pVP = death ➞ primary way prey are affected by predator through death
predators:
* predator birth rate (cp) ➞ birth of predators is based on resources coming from prey
* cpVP = birth ➞ primary way predators are affected by prey is through increased reproductive output
* c = conversion of prey ➞ predators = how efficiently does predator turn increasing resources from prey into increased offspring
interspecific competition
better competitor = flatter line
* smaller diff in density from start to finish
worse competitor = faster rate of dying
* larger diff in density from start to finish
competitive exclusion principle
2 species competing for the same limiting resources cannot coexist ➞ eventually the stronger competitor will drive the weaker competitor extinct
resource partitioning
species share limited resources by using them in diff ways ➞ allows coexistence
1. diff phys areas of habitat
2. diff parts of resource
* pollinators ➞ based on colors & shapes
* photosynthesis ➞ using unused wavelengths
character displacement
species competing for same limiting resources diverge in morphology due to NS
* when resource partitioning is coupled w/ selection in a physical trait that relates to competitive interaction
* helps separate what plant species they are feeding on ➞ reduces competition
ex: galapagos finch
* when occur allopatrically: small diff in beak size (overlap in beak size)
* when occur sympatrically: large diff in beak size (no overlap)
facultative mutualism
not needed for either species to survive & reproduce
* optional interaction b/c can exist without
* ex: mycorrhizae ➞ plant & fungus can grow/reproduce, just better w/ interaction
obligate mutualism
symbiosis with other species is necessary for survival & reproduction
* 1 or both species cannot survive or reproduce without interaction
* not optional
* specific to species
* ex: Yucca plant & moth: plant only place where moth can lay eggs & moth only pollinator for plant
examples of obligate for parasite/herbivore but facultative for host/plant
- certain tapeworms & sharks
- pandas ➞ bamboo
- koala’s ➞ eucalyptus
conditional interactions
conditional to the envir: where/when
ex: plants & fungus:
* low water/nutrient availability: interaction = beneficial for both
* high water/nutrient availability: plant doesn’t need fungus to survive
* investing in relationship where it is not getting anything in return ➞ giving sugar away for free
- parasitic under ↑ nutrient availability
primary drivers of biomes
annual precipitation & temperature
tropical rainforest
high precipitation year round
high temperature year round
along equator b/c of hadley cell
desert
very low precipitation
seasonality in temp
* most at ~30°N & 30°S
* driven primarily by Hadley cell
* S: june/july = cold season
* N: june/july = hot season
temperate deciduous forest
- seasonal temp
- precipitation high year-round
boreal forest
- highly productive
- highly seasonal
- unevenly represented in the 2 hemispheres ➞ N only
- drives oscillations in CO2 levels
arctic tundra
very little precipitation
high seasonality in temp
only couple months above freezing
temperate grassland
high seasonality in temp
high seasonality in precipitation
warm season = wet season
temperate grassland
Mediterranean or chaparal
high seasonality in temp
high seasonality in precipitation
mediterranean or chaparral
how to define ecosystems
- salinity
- flow & movement
- depth
aquatic ecosystems & salinity
- freshwater ➞ low salt content
- brackish: where fresh & salt water meet/mix ➞ salt content between ocean & freshwater
- extra salty bodies ➞ evaporation, bedrock
aquatic ecosystems & flow & movement
flow & movement ➞ difference between fresh river & fresh lake
* stagnant vs flowing
* speed
* direction
* over terrain: waterfalls
