Unit 2 Ecology Review

metapopulation

metapopulation

a set of spatially isolated populations linked by dispersal of individuals or gametes

metapopulations are characterized by repeated _______ and _______ of the small individual populations

extinctions, colonizations

source

the number of individuals that disperse to other populations is greater than the number of migrants they receive (place where population is doing well)

emigration > migration

sink

receive more migrants than the number of individuals that disperse to other populations (where organism goes to die pretty much)

migration > migration

metapopulation dynamics (high migration)

causes the metapopulation to behave as a single, large population

metapopulation dynamics (intermediate migration)

colonization of patches left open by subpopulation extinction, mosaic of occupied and unoccupied patches

metapopulation dynamics (no migration)

each subpopulation becomes isolated and at risk of extinction

dp/dt = cp(1-p) - ep

extinction and colonization of patches

p = proportion of habitat patches occupied at time t

c = patch colonization rate

e = patch extinction rate

c > e for metapopulation to persist

isolation by distance

when patches are too far apart

effect of patch size

small patches may be hard to find and have high extinction rates

rescue effect

High rates of immigration that protect a population from extinction

extinction can be caused by what two reasons for metapopulations?

1. Patchiness in habitat makes dispersal from other populations difficult

2. Environmental conditions changing rapidly + in unpredictable manner

T/F All populations form metapopulations

False

What happens if e/c > 1 what will happen in metapopulation?

metapopulation will go extinct

Habitat Fragmentation example

Spotted owls became Northern spotted owl, Mexican spotted owl, and California spotted owl because of isolated patches

Isolation by distance + effect of patch size example

Skipper butterflies- cows stopped grazing leading to loss of grass land leading to smaller + isolated patches making them less likely to be colonized by more butterflies to persist

effect of patch size example (unaffected by isolation)

Shrews- live on islands in lakes, island occupancy is strongly affected by island size, but unaffected by isolation because they are such strong swimmers

habitat fragmentation

Breakup of a habitat into smaller pieces, usually as a result of human activities, turns populations into metapopulations and into isolated populations no longer linked by dispersal

life history characteristics

-age and size at sexual maturity

-amount and timing of reproduction

-survival and mortality rates

overall pattern of life history:

growth, reproduction survival

What do differences in life history come from?

genetic and environmental variation

optimal life histories maximize _________

fitness

fitness

Ability of an organism to survive and reproduce in its environment

metamorphosis

abrupt transition in form between larval and juvenile stages

-different body forms, habitats, and food

ex: caterpillar to butterfly, tadpole to frog

phenotypic plasticity

our genotype produces different phenotypes under different environmental conditions

phenotypic plasticity example

trees in the desert grow shorter and with smaller leaves than in cool, moist climates

Polymorphism

The existence of more than one form of a genetic trait.

example of morphs

tadpoles

omnivore morph- grow slowly, metamorphose later w/ higher chance of survival, permanent ponds

carnivore morph- grow faster, metamorphosize earlier, temporary ponds

asexual reproduction

cell division (binary fission) done by all prokaryotes and most protists

sexual reproduction

most plants, animals and many fungi + protists

3 disadvantages of sexual reproduction

-an individual transmits only half of its genome to the next generation

-population growth rate is only half that of asexually reproducing species

-recombination and chromosome assortment during meiosis can break up favorable gene combinations

advantage of sexual reproduction

recombination promotes genetic variation and increased ability of populations to respond to environmental challenges

the cost of males meaning

asexual reproduction produces twice as many offspring as sex

semelparous

species that reproduce only once

iteroparous

species can reproduce multiple times

r

intrinsic rate of increase of a population

K

carrying capacity of a population

r-selection

selection for high population growth rates; an advantage in newly disturbed habitats and uncrowded condition

-short life spans

-rapid development

-early maturation

-low parental investment

-high reproductive rates

K-selection

selection for lower growth rates in populations that are at or near K; an advantage in crowded conditions; efficient reproduction is favored

-long life spans

-develop slowly

-late maturation

-high parental investment

-low reproductive rates

gradient between r and K species

oysters ---> frogs ---> gorillas

life history trade-offs

large investment in offspring but few offspring

lots of offspring but little parental investment and lower survival

large offspring but few offspring

small offspring but many offspring

if there is a trade-off between reproduction and growth rate, then:

the more offspring you produce, the shorter your lifespan

trade-off between reproduction and survival

higher fecundity = lower survival

population abundance

number of individuals

population density

Number of individuals per unit area

on a 20-hectare island, there 2500 lizards. What is the population density?

125 hectare^-1

isolated patches can be linked by ________

dispersal / gene flow

clones are formed by

budding, apomixis (unfertilized eggs), horizontal spread (likes trees, offspring produced as organism grows)

abiotic factors that limit distribution

water, temperature, pH, sunlight, nutrients, etc.

biotic factors that limit distribution

predation, parasitism, competition, disease

dispersal limitation

A situation in which a species' limited capacity for dispersal prevents it from reaching other areas

population

group of individuals of the same species that live in the same area

geographic range

the entire geographic area over which a species is found including all of its life stages (migration)

Nearly Regular Distribution

due to competition for resources

Random distribution

due to short dispersal distances or targeted resource availability

Clumped distribution

due to short dispersal distances or targeted resource availability

-ex: trees clumped around water source

absolute population size

the actual number of individuals in a population

relative population size

number of individuals in one time period or place relative to the number in another

area-based counts

individuals in a given area or volume are counted and averaged to estimate population size

-usually quadrats

-for immobile organisms (ex: coral)

40, 10, 70, 80, and 50 cinch bugs are counted in five 10 cm x 10 cm (0.01 m2) quadrats. What is the population density per m^2?

5000 m^2

(40 + 10 + 70 + 80 + 50) / 5 = 50 / 0.01 m^2 = 5000 m^-2

distance methods

distances of individuals from a line or point are converted into estimates of abundance

-used for large area

line transects

Observer travels along line and counts individuals and their distance from the line

mark-recapture studies

A subset of individuals is captured and marked or tagged, then released.

At a later date, individuals are captured again, and the ratio of marked to unmarked individuals is used to estimate population size.

-used for mobile organisms (ex: fish)

-more organisms recaptured is an indicator of small population size