bio 130 exam 2

directional selection

changes avg phenotype in pop in one direction
reduced genetic diversity since 1 phenotype is favored
purifying selection
shifting to one extreme

disruptive selection

intermediate phenotypes are selected against and extreme phenotypes are favored

increases amount of variation

has the opposite effect on stabilizing selection

stabilizing selection

reduces both extremes and favors the average

reduces the amount of variation

gets skinnier in the middle

balancing seelction

occurs when no singles allele has a distinct advantage

heterozygote advantage and frq dependent selection

heterozygote advantage

individuals have higher fitness than homozygous individuals

sickle cell

frq dependent selection

certain alleles are favored when rare

not common

life history describes

growth, development, reproduction, and survival

life states defined by

embryo, juvenile, and adult stages across tree of life

what environmental factors influence state length and reproductive output

fecundity

parity

parental investment

longevity/life expectancy

fecundity

the number of offspring per reproductive episode

parity

number of episodes of reproduction

parental investment

energy incurred by parent to raise offspring

longevity/life expectancy

lifespan of the organism

why do we see variation in life history

growth, maitenance, reproduction

growth

body size

maitenance

lifespan

reproduction

number of offspring within a reproductive bout and the frq of reproduction

principle of allocation

only a limited amount of energy that is distributed to the 3 pts (reproduction, maitenance, growth)

fast-slow continuum

reprsents 2 extremes of how tradeoffs manifest

often reflect variation in life form, habitat, or environmental condition

fast side

greater number of offspirng, shorter life span, faster growth, earlier reproduction, earlier sexual maturation, smaller parental investment

slow side

fewer offspring, longer lifespan, slower growth, delayed reproduction, later sexual maturation, greater parental investment

life history and pop growth

semeiparity

organisms that reproduce once

mayflies

interoparity

organisms that reproduce multiple times in their life

iterative

oak trees

costs and benefits of mice reproduction (6 pups every 3 wks)

costs: low prenatal care, increased number of offspring, decreased life span

benefits: increased gene pool with mating patterns, at least one will survive

cost and benefit of tortice reproduction (2-16 eggs per year)

costs: takes longer to reach sexual maturation, decreased number of offspring

benefits: increase prenatal care, longer lifespan

Offspring v. prenatal care: 1947 study

modified eggs in European magpie nest

manipulated total offspring without sacrificing parental services

7 eggs is the perfect amount bc most wil survive and it is the perfect amount to provide for

determinate growth

growth pattern in which an individual does not grow anymore once it initiates reproduction

inter-determinate growth

growth patterns in which an individual continues to growth after initiating reproduction

population

group of species that live in the same area and inter breed

darwins quote highlights how

there are many factors in place that pops are diverse and numbers are kept in check

Factors contributing or detracting from pop growth

births (+)

deaths (-)

immigration (+)
emigration (-)

exponential growth

consistent high amounts of growth

represents continuous growth, but not all organisms have a continously growing pop

exponential growth equation

r=intrinsic rate of rate

per-capita growth rate (births-deaths) under ideal conditions

rate of pop growth for exponential growth

r=net number of offspring individual time

geometric growth model

dots represent organisms that ahve 1 distinct breeding event per yr

compares pop numbers at set intervals

doesnt assume continuous births and deaths in a pop

geometric growth equation

lambda is the ratio for a population in 1 yr to the preceding yr

Populations with discrete reproductive periods increase by

geometric from

equation for reproductive periods from one time to the next

equation for repoductive periods over long time periods

how is lambda different from r in exponential growth

when discussing discrete growth patterns, lambda compares year with previous yrs

at different time pts we can solve for lambda

when more deaths than births, see

lambda decrease

when births and deaths are the same

flat line

when more births than deaths,

increasing lambda

lambda can also be calculated for

exponential growth we just need to know N at 2 pts in time

what factors limit pop growth

density dependent factors

negative density dependence

when pop growth decreases and pop density increases (from increased competiotion)

positive density dependence

when more indvidual present result in increased fitness of the pop, resulting in increased growth

often observed in really small pops

density independent facotrs

factors other than pop density determine pop size (abiotic factors)

temp and precipitation

negative density dependence

an ecological process where a population's growth rate or individual fitness increases as population density increases

Negative influences on pop

competition ,limited resources

positive influences on pop

increase surplus, increased interaction, start low pop #

Consequences of low pop density

difficulty in finding mates

poorer predator detection

lower genertic diversity, inbreeding

populations can experience

positive or negative density dependence at different times

logistic (sogmodial) growth model

what is the equation

assumes all individuals are the same

carrying capacity

amount of resources that can support a pop

represented by a pop number

can change over time

reindeer on st paul island

original carrying capcity reduced by overgrazing of lichens

reindeer switched to grass and grass roots

current carrying capacity: around 400 reindeer

facotrs for pop growth and density for barnicles

food, salinity, water, density/space

age structure is important to pop growth

populations with high proportions of younger individuals (of reproductive age) can have higher growth rates

metapopulation

composed of subpopulations that are connected to eachother

metapopulation models

black dots are occupied; open dots are not

Lines indicate migration; dashed lines outline indicate high migration

Levins model

patches are either occupied or unoccupied; otherwise equal quality of patches to support population growth

Mainland model

mainland patch is highly occupied because it is a higher quality area.

Contribute to other, low quality patches

patchy population model

different quality of patches, but see migration between; constant rates of high migration among all patches

Non-equilibrium model

migration between some patches, but not all

rescue effect

the phenominon of dispersers supplementing a declining subpopulation that is headed toward extinction

effects of patch size and patch isolation

The shrew was much less likely to occupy patches that were small or more isolated.

The skipper butterfly in Britain occupies the largest patches of grasslands and those that are the least isolated.

• The line indicates the combinations of patch area and patch isolation that correspond to 50 percent probability of patch occupancy.

Consumer resource interactions

interactions that account for organisms being a resource for another organism OR consuming another organism

Competition

A relationship where organisms fight for the same limited resources, such as food, water, space, or mates.

Predation

A relationship where one organism (the predator) hunts, kills, and eats another organism (the prey).

parasitism

A relationship where one organism (the parasite) benefits while the other organism (the host) is harmed, usually without being immediately killed.

herbivory

A relationship where an animal eats plants or algae.

herbivores

consume plant and plant materials

mesopredators

consume herbivores, often smaller

top predators

consume herbivores and mesopredators

parasitoids

specialized predators

live inside and consume their host during development

parasitoid wasps

large group of wasps that need to lay their eggs inside other insects to complete their lifestyle

useful in contorlling both niative pests and invasive species

do not sting or bite people

California redscale

atiny insect with a hard shell

feeds on the sap of citrus trees and other plants.

The parasitoid wasp lays its eggs under the hard shell of the scale insect. When the eggs hatch, the larvae slowly consume the scale insect.

After introducing large numbers of scale insects to trees the scale insect population grew rapidly. Soon after the addition of the scale insects, the number of juvenile and adult parasitoid wasps began to rapidly increase. This increase in parasitoid wasps caused a subsequent rapid decline in scale insects.

lotka-volterra model

a model of predator-pret interaction that incorporates oscillations in the abundances of predator and prey pops and shows predator number logging behind these of their prey

prey pop change lotka-volterra model

rn= growth rate x number of prey

cnp= capture efficieny, np-random encounter with predator