Studied by 285 people
Covers Lectures 18-25
Biological Species Concept (B.S.C)
A species is sa group of actually or potentially interbreeding natural populations that are reproductively isolated from other groups.
Pros and Cons of B.S.C.
Pros: Simple to Understand, Based on H-W concepts
Cons: Doesn’t apply to some organisms, do not always have mating data, complexity of mating systems
Phylogenetic Lineage Species
A species is a group of organisms that shares a common ancestor and can be distinguished from other organisms by particular traits
Morphological Species Concept
A species is a group of organisms that have similar physical traits
Pros and cons of Linkage Species Concept (Phylogenetic)
Pros: includes historical/evolutionary context & applies to all organisms for which genetic data is still available
Cons: requires modern genetic & computational tools
Pros and cons of Morphological Species Concept
Pros: good for groups where other data are limited
Cons: similarity and differences in appearances can be misleading
The Two Kinds of Reproductive Barriers?
Prezygotic and postzygotic barriers
Prezygotic Barriers
Prevent mating or prevent fertilization if mating occurs
Postzygotic Barriers:
Prevents a hybrid zygote from developing into a viable, dertile adult
What are the 5 prezygotic barriers?
habitat isolation, temporal isolation, behavioral isolation, mechanical isolation, gametic isolation
Habitat Isolation (geological or ecological
Species occupy different geological habitats, never come into contact, or use different parts of a habitat.
Temporal Isolation
breeding at different times
Behavioral Isolation
Individuals do not recognize each other as potential mates
Mechanical Isolation
Physical differences between the organisms prevent successful mating
Gametic Isolation
Sperm is not able to fertilize the egg
What are the three postzygotic barriers?
reduced hybrid viability, reduced hybrid fertility, hybrid breakdown
reduced hybrid viability
Hybrid offspring do not complete development or have low survivorship
Reduced Hybrid Fertility
Hybrid offspring are viable, but incapable of reproduction
Hybrid Breakdown
Hybrid offspring are viable and fertile, but subsequent offspring are not viable or sterile
Phylogenetic Trees
A graphical depiction of the history of relationships among a group of organisms
Branch Point (p trees)
Where lineages diverse, can tell about time
speciation (p trees)
Creates new branches, new lineages
extinction (p trees)
removes branches, loss of lineages
monophyletic clade
A group that includes ALL of the taxa descended from a specific common ancestor
How does reproductive Isolation evolve and what are the possible outcomes?
Population is mating, there is a barrier to mating, the isolated population diverges.
If they do come back into contact, the outcomes are:
Reinforcement (stay separate species from reprod. barrier), fusion (turns back into one evenly mixed population), or stability
What are the 4 modes of speciation?
Allopatric (vicariance), Allopatric (founder effect), Parapatric, Sympatric
Vicariance
The geographic separation of a species into separate populations through some form of physical barrier.
(Think: Tectonic Plate Movement or Oxbow Lake Formation)
Allopatry (Vicariance)
Physical geographic barriers separate the population into roughly halves.
Allopatry (Founder Effect)
A small subset of the population colonizes a new area, geographically separate from larger background pop.
Parapatry Speciation
One “edge” of the population experiences different conditions than the broader population, not geographically distinct but not fully intermixed, partially overlapping/ adjacent.)
(Think ZINC tolerance flowers).
Sympatry Speciation
Some genetic change arises in one or a few individuals that are distributed across a fully intermixed population.
(Think: apple and hawthorn bugs).
Speciation
When populations evolve to become distinct species, produces two or more populations that cannot interbreed.
What allows for better speciation?
Specialist organisms (produces behavioral or geographic isolation),
Pollination by biotic factors
Dimorphism
Lower Dispersal Ability (better dispersers will be less likely to experience allopatric speciation than poor dispersers.)
What are the two rapid, adaptive speciations?
Evolutionary radiation & Adaptive radiation
Evolutionary Radiation
Speciation produces many new species within a given group rapidly.
Adaptive Radiation
the new species are specifically adapted to particular niches within the ecosystem.
(Think: Hawaiian honeycreeper birds; 55 species from one common ancestor adapted to different food sources).
Can speciation occur in a single generation?
Yes but rare
Polyploidy
having more than 2 sets of chromosomes
Allopolyploidy
The polyploid carries the combined genes of two separate species
Autopolyploidy
The polyploid carries duplicated genome of single species
Are polyploids reproductively isolated from their diploids relatives?
Yes, their offspring will have an odd number of chromosomes which cannot be easily divided during meiosis, so they will be sterile. They can breed with other polyploid but are considered different species from their diploid relatives.
Symbiosis
An interaction between two species living in close association with each other (doesn’t have to be a positive interaction).
What falls under +/- species interaction?
Predation, parasitism
Predation
One species benefits, one is harmed
competition
when individuals require the same shared, limiting resource, everyone loses (-,-)
mutualism (
amensalism
One species injured but the interaction, the other is unaffected by the other species. (-,0)
Predation/Parasitism/herbivory
One species benefits at the cost of another. (+,-)
commensalism
One species benefits and the other is unaffected. (+,0)
-Often refers to mobile associates.
facilitaion
One species benefits and the other is unaffected. (+,0)
-Often refers to sessile associates
Lotka-Volterra Model (prey, victim)
dV/dt = rV - pVP
where:
r = prey growth rate
V = # of victims
p = predation rate
P = # of predators
c = conversion rate of prey to predators
d_p = predator death rate
dN/dt read as “change in pop size through time.”
Lotka-Volterra Model (predator)
dP/dt = cpVP - d_pP
where:
r = prey growth rate
V = # of victims
p = predation rate
P = # of predators
c = conversion rate of prey to predators
d_p = predator death rate
dN/dt read as “change in pop size through time.”
what drives oscilation? (predator and prey)
reciprocal density dependence —> consumption rate per predator is high when prey density is high, with fewer prey available, predator population declines
why is there a lag in oscilation?
Because of how long it takes to for reproduction.
when calculating lusing okta-volterrra models, what does the sign ( positive & negative) mean?
Positive means it’s increasing pop sizes, negative means it decreasing.
Does this oscillation always occur in nature? (prey and predator)
Sometimes.
intraspecific competition
competition for resources between members of the same species
interspecific competition
competiton for resources between members of different species
results of competition
limited growth, reprodution, and/or survivial for both competitors.
how to determine if a species is a better competitor (specific example) (?)
look at the slope in terms of ending density, more density = less mortality.
competitive exclusion principle
two species competing for the same limiting resource cannot coexist, eventually the stronger competitor will drive the weaker competitor extinct.
how can an example still be considered competitive exclusion when both species still occur in the habitat? (semibalus and chthamalus)
it is exlusion bc a species is excluded to the portion of the habitat that the better competitor cannot occupy.
where semibalous can occur, chthamalus doesn’t, FULL STOP. we only see chthamalous where semibalous is not.
competitive exlsuion or coexistance? (niche overlap)
the more two species’ niches overlap, the more likely it is that competitive exclusion will occur, while less overlap (variation) allows for natural selection to seperate the niches —> coexistance.
resource partitioning
species share limiting resources by using them in different ways, allowing them to coexist. (think bacteria species utilizing top and bottom of vial).
What are two ways resources can be partitioned?
Using different physical areas of the habitat (vial example).
using different parts of the resource (light is everywhere, but different plants absorb different particular subsets of the visible spectrum)
facultative mutualism
they can survive w/o said interaction
obligate mutualism
the partner is obligated ot participate in it, they cannot survive or reproduce without each other.
explain the conditional interactions between mycorrhizae and plant
for plants, a positive net interaction occurs under low nutrient/water availability, but turns negative under high nutrient/water availability, bc the fungus receives free sugar without reciprocating benefits, which is constant regardless of nutrient availability
why woyld mutualistic interactions be more common at higher elevations?
In easier ecostystems, it is negative to be closer, but when the ecosystem is harsher (high elevation) it is more beneficial to be closer together. (think: easy class vs hard class
conditional interactions
species interactions where the benefit/cost to either party is dependent on environmental conditions.
Primary Succession
succession that begins on bare ground with no soil profile. Think: glacier retreat, dune accretion, lava flows.
primary succession is when species colonize an area of land for the first time on bare rock (no soil) think: lichens, mosses, etc that break down rock into soil for the first time,then grasses, flowers.
Secondary Succession
When an area of land experiences disturbances and is trying to recover from that disturbance. succession that has a developed soil foundation (even if everything
above ground has been destroyed, though in some cases, some above-ground organisms can
survive).
Intermediate Disturbance Hypothesis Explain:
Species diversity is highest at intermediate levels of disturbance because competition reduces diversity at low levels of disturbance and mortality reduces diversity at high levels of disturbance.
Refutations of IDE (
Intermediate Disturbance Hypothesis predicts…
… that intermeditate levels of both frequency and intensity have the greatest diversity
Earth’s biomes are determined by…
annual precipitation and temperature, also impacted by seasonality and disturbance
Tropical Rainforest
found at equator, no variation/seasonality and high in temperature and high precipitation
hot and wet
driven by hadley cell
Desert
30 degrees North and south of equator, and some edges. low precipitation, high temp
How to determine whether northern, southern, or at the equator? (biome)
temperature and month
hot in June —> northern
cold in june —> southern
Temperate Deciduous Forest
high precipitaiton, seasonality in temperature
north of equator
boreal forest
low precipitation, low temperatures, seasonality in temperature, but still low. (boreal forests in south, but it is ocean, vast majority in north).
artic tundra
low precipitation, low temp, seasonality in temp.
The difference between arctic and boreal is that much of the year is below freezing. artic has ¾ months above freezing.
how do plants access nutrients in the arctic tundra?
in the active layer
What is the issue with permafrost?
temperate grasslands
seasonality in temp, seasonality in precipitation
wet season is same as warm season
mediterranean (california)
similar to grasslands, seasonality in temp and precipitation, warm season is dry season (why fire prone)
located west-edges of continents
Aquatic Biomes are defined by..
salt content, flow and movement, and depth
why are wetlands important?
they clean the the water, habitats for species, and acts as physical defense agianst floods, high tides and surges.
california’s wetlands are..
breeding gorunds, and a migrating route
why are wetlands in decline?
conversion of land to agriculture and housing
What two types of fires happen in california biomes?
ground/surface fire, and crown fire (entire tree is engulfed)
What are the two kinds of Pine Fire Syndromes
fire tolerators, fire embracers
fire tolerators
Tall with no branches near ground ,thick, bark, long needles
fire embracers
short, thin bark, flammable needles, keep low branches, closed cones
what are the two Chaparral Shrub Syndromes
fire recruiters and fire resisters
fire recruiters
seeds are dormant until fire, germinate immediately after fire event, (good time to germinate)
fire resisters
can resprout from below-ground tissue, no seed formancy and no adaptations for survivng fire events.
Prairie Fire
fire is what keeps it a grassland and not a shrubland of trees… stimulates lush regrowth and prevents tree encroachment
which tree is more susceptible to fire?
tree that has been grazed, not close to grass at all
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