Bio 204 Unit 3

abiotic conditions

include temperature, precipitation, light availability, salinity, soil composition, and flooding frequency

biotic conditions

interactions between organisms in an ecosystem: includes competition, predation, parasitism, mutualism, dispersal ability, etc.

ecological niche

combination of factors that make up the space a species occupies: categorized into fundamental and realized

fundamental niche

the potential range of a species based on abiotic factors they can tolerate

realized niche

the actual habitat range of the species based on abiotic and biotic factors combined, can be the same or different from the fundamental niche

biogeography

how species are distributed the way they are and why, based on the history of the planet

endemism

when a species only exists in one place (i.e. lemurs are only in Madagascar)

impacts of plate collision on species

dispersal and interchange becomes possible between once-isolated species

impacts of plate separation on species

gene flow is eliminated and populations become isolated, causing speciation

Beringia land bridge

connected Asia and North America, allowed mammoths, bison, maybe humans, etc. to disperse from Eurasia to North America, disappeared when glaciers melt and sea level rose

Great American Biotic Interchange

Panama land bridge appeared 3 million years ago, mammals incl. marsupials (armadillo, opossum, porcupine) in South America and placental mammals (pigs, bears, horses) in North America dispersed into the other areas, placental mammals outcompete marsupials so they became predominant

impact of mountain formation on species

populations become isolated and speciation occurs

impact of land bridge formation on species

increases gene flow and allows for greater dispersal between species

Pangea (250 mye) significance

there were oceanic barriers between species, it was physically possible for species to move anywhere (lots of shared lineages) and

breakup of Pangea (180 mye)

two subcontinents: Laurasia (north) and Gondwana (south), gene flow was suddenly restricted and massive vicariance events occurred, lots of speciation and divergence

breakup of Gondwana (100 mye)

Madagascar breaks off, more ocean barriers formed, isolation increased, independent evolutionary trajectories occurred

ratite birds and Gondwana

all types of ratites (across S. America, Australia, New Zealand, Africa, and Madagascar) are flightless except one, it was initially assumed the one flying species evolved flying but molecular evidence revealed that the Gondwanan common ancestor could fly and all the species but one independently evolved flightlessness after being seperated

wiens and donoghue

the geographic distribution of a given clade (multiple species with common ancestor) are determined by ancestral ecological niche, geographic starting point, limitations to dispersal, opportunities for niche evolution, and the amount of time since origin

ancestral ecological niche (wiens)

what niche did the common ancestor have, what niches do the descendant species (clade members) occupy

geographic starting point (wiens)

where and when the clade originated, where they’re capable of dispersing into

limitations to dispersal (wiens)

what limitations to expansion were imposed by abiotic conditions and other species

opportunities for niche evolution (wiens)

what niches did an individual species have the opportunity to fill based on current geographic location

time passed since origin (wiens)

how long a clade had for niche evolution and dispersal to occur

clade

a group consisting of all the known descendants of a certain common ancestor

population density

the number of individuals per unit area

random dispersal pattern

individuals are positioned independently in the environment, i.e. random dispersal (like seeds by wind)

clumped pattern

individuals aggregate in clumps/groups, causes social behaviors and patchy resources (most of the environment doesn’t support the population so they cluster around areas with the resources they need)

uniform distribution

occurs when organisms distance themselves from each other due to extreme competition, territorialism, etc.

metapopulation

a population composed of connected or close small populations, populations might have gene flow but they don’t have to

Quadrat counting method

used for nonmoving or slow moving organisms, count the individuals in a certain defined quadrat area and then extrapolate this count to estimate the total population size

line transect counting

used for nonmoving or slow moving organisms, follow a pre-determined line and count how many organisms you see as you follow that line, extrapolate to estimate the total population size

mark-recapture counting

capture and mark individuals in a species, release them, later recapture a number of the individuals and count how many are marked vs unmarked and use to estimate population size

assumptions of mark-recapture counting

assumes that the number of marked individuals reflects the total population size, no immigration or emigration, no trap avoidance or attraction, marking doesn’t affect survival

BIDE principals of demography

Birth, Immigration, Death, and Emigration

survivorship (lx)

proportion of a cohort that survives to a certain age class

age-specific fecundity (mx)

average number of female offspring produced per original female in the population at that age class

net reproductive rate, Ro

average number of female births per year per female at a certain age class

Ro > 1

increasing population

Ro < 1

decreasing population

Ro = 1

stable population (each female replaces herself)

type 1 survivorship

high survivorship through most of the life until reaching a certain age of very low survivorship (i.e. humans, survivorship plummets about 80 or 90)

type 2 survivorship

steady survivorship, consistent decline in amount of individuals that make it to adulthood, constant mortality rate

type 3 survivorship

low initial survivorship/high juvenile mortality, but the individuals that make it to adulthood tend to live a long time (i.e. sea turtles, lots of babies and most don’t survive, but ones that become adults live a long time)

age-specific fecundity

average number of female offspring produced at each age: age-specific fecundity often increases with age, you can have different levels of fecundity depending on the age and lifestyle of the organism

survivorship of low fecundity

high survivorship: more energy is put into making fewer, stronger offspring

survivorship of high fecundity

low survivorship: less energy is put into making more, weaker offspring

net reproductive rate

Ro (number of offspring per female)

overshooting carrying capacity

population can suddenly crash, if the population overexploited resources, the carrying capacity can decrease significantly due to environmental degradation

changes in carrying capacity

can decrease due to overexploitation of resources and environmental degradation, or increase if a new resource is introduced (i.e. new plant species that an animal can eat)

bottom-up population cycle

Resources at the bottom of the food web constrain the populations of the organisms that eat those resources

hare/lynx bottom up example

hare populations are limited by how much food they have, lynx decline when the hares starve because now they don’t have food either

top-down population cycle

High predator density causes crashes in the population of prey, low predator density causes prey population to increase

hare/lynx top down example

Lynx predation controls the size of the hare population, when there are more lynx, there are less hare

interaction hypothesis population cycle

both food limitation and predation act together to create population cycles, the combined effect is stronger than either one alone.

Lotka-Volterra model assumptions

Assumes prey grow exponentially without predators, predators rely on a single prey species, environment doesn’t change, no resource limitation for the prey

Lotka-Volterra model

population size of the predator + (growth rate)number of predators(number of prey)) - (death rate of predator(number of predator)

community

All populations of different species that interact in a particular area, focusing on how they interact

density dependent factors

competition, predation, disease

Lotka-Volterra model prey

population size of the prey+ (growth rate)number of prey)) - (death rate of prey(number of prey(number of predators))

density independent factors

climate conditions (temperature, precipitation, etc), natural disasters, habitat destruction

metapopulation

a large population made of smaller fragmented populations, they can have gene flow but they function as independent populations. helpful because if a population goes extinct, it can be recolonized by individuals from another patch.

what interactions do

affect distribution and abundance, act as agents of natural selection, and are dynamic and context dependent

4 types of species interactions

commensalism, mutualism, consumption, competition

commensalism

one organism benefits, the other has a neutral effect

mutualism

both organisms benefit from the interaction

consumption

one organism benefits, the other is harmed (types: predation, herbivory, and parasitism)

competition

harms both organisms because they must spend more energy competing for limited resources

caveat to commensalism: example

Epiphytic orchids get more access to sunlight by growing on trees and it’s mostly completely harmless to the trees. HOWEVER, with high densities of orchid populations, the effect turns negative: add weight to branches and increase breakage risk, shade leaves and prevent photosynthesis, etc.

benefits of metapopulations

populations in different segments of the metapopulation can recolonize areas where the original population goes extinct

factors increasing population survival

larger size (less impact of genetic drift), larger habitat patches, proximity to other populations (more gene flow), higher genetic diversity (better adapt to environmental change)

high fecundity

larger birth rate, more offspring being born, associated with lower survivorship of offspring

low fecundity

smaller birth rate, less offspring being born, associated with higher survivorship of offspring

population momentum

continued growth of a population after fertility declines, a large number of young individuals reach reproductive age

intraspecific competition

competition between members of the SAME species

interspecific competition

competition between members of DIFFERENT species

direct competition

Physical interference between species (i.e. a lion and a hyena chasing the same prey)

indirect competition

Depletion of shared resources (i.e. elk eat the same plants as beaver)

competitive exclusion

If you have two species with the same niche, one of them will eventually outcompete the other and make it go extinct (although almost no species has the exact same niches)

niche differentiation and character displacement

Evolution favors individuals that compete less, so natural selection selects for individuals with a non-overlapping niche [disruptive selection], overlap has lower fitness due to competition, this phenomenon increases trait divergence

coevolutionary arms race

Prey evolves better defenses against predators, predators evolve to better catch prey.

coevolutionary arms race example

Gazelles increase in endurance so they can escape cheetahs, cheetahs get faster so they can get food, cycle continues

constitutive defenses

defenses against predators that are always present, like thorns on a plant

inductible defenses

defenses triggered in response to a threat, i.e. plants that produce toxic chemicals when something starts eating them (they spend less resources than if they made it all the time)

4 attributes of community structure

number of spaces, relative abundance, network of interactions, physical structure of the environment

species richness

counting the number of species present

species diversity

the balance of species richness and evenness to determine overall diversity

species evenness

relative abundance of species to each other, more even proportions means better species diversity

trophic levels

organizing organisms based on where they fit into food webs: producers, primary consumers (herbivores), secondary consumers (eat the primary & lower), tertiary consumers, and quaternary consumers. Producers are VERY important in maintaining and supporting biodiversity 

keystone species

species with disproportionately large effects on communities, i.e. starfish (if it’s present, biodiversity is maintained, but without it, community diversity plummets because they keep mussel population in check)

bottom-up community structure effect

Resource availability controls community structure, nutrients flows to the producers and then to the consumers (primary, then secondary, then tertiary, etc.)

top-down community structure effect

consumers regulate prey populations, i.e. wolves are present in an ecosystem and they maintain the population of elk so the vegetation populations can stay stable

ecosystem engineers

species that create physical structures, like corals, beavers, etc.

trophic cascade

indirect effects of consumers that reverberate throughout the food web

trophic cascade example

Wolves in Yellowstone made a trophic cascade: They ate more elk, plant populations recovered, so now the beavers had more food, so the beaver population increased 

3 geographic patterns in species richness

area effect, islands, latitudinal diversity gradient

area effect

larger areas support more species

islands species richness

larger and closer islands have more species richness, as they get farther apart, extinction becomes more likely (less individuals, more genetic drift, extinction rates higher because of limited genetic diversity, less immigration due to distance)

measuring island species richness

biogeography is measured with rates of immigration vs. rates of extinction, equilibrium number is where these two meet, making a stable population

biodiversity (3 levels)

genetic diversity, species diversity, and ecosystem diversity

genetic diversity

total genetic information, represents adaptive capacity (higher genetic diversity means more for natural selection to act on)