Life 320 Exam 2

Ecological envelops and niche modeling

A method for predicting species distributions based on environmental data and samples of species occurrence

endemic species

A species that is found in its originating location and is generally restricted to that geographic area.

Clustered Distribution

A pattern of distribution where several clusters of objects are spread out over an area with space between the clusters

even distribution

Occurs when a set pattern or even spacing is seen between individuals.

random distribution

distribution in which the location of members in a population is totally random, location of each individual is determined by chance

dispersal

Movement of individuals away from centers of high population density or their area of origin.

population census

survey covering an entire population

must be describing something using numbers

population survey

A survey designed to provide a description of the members of a population by sampling a representative portion of that population. If researchers make use of random sampling, they can typically provide accurate estimates of the characteristics of a very large population based on a relatively small number of people.

mark-recapture method (Lincoln-peter index)

A sampling technique used to estimate the size of animal populations. individuals are captured, counted, and marked then released back into the wild. later more individuals of the population will be captured and marked and the number of marked individuals recaptured helps determine the population size

habitat corridors

natural strips of land that allow the migration of organisms from one habitat patch to another

density dependence

factors where the effects on the size or growth of a population vary with the density of the population itself

negative density dependence

population growth decreases as density increases which could be due to limited food resources

positive density dependence

when the rate of population growth increases as population density increases (allee affect). ex larger populations make it easier to find a mate

delayed density dependence

when density dependence occurs based on a population density at some time in the past

density independence

factors in environment that cause mortality or influence reproduction, but their effect is independent of population density (for example, a harsh drought).

delayed density dependence equation

dN/dt \= rN (1-N1-T/K)

cycling depends on r and T

.37 < rT -\> the population approaches K

.37 < rT < 1.57 -\> cycling is dampended and there is a decline in cycling over time

rt < 1.57 -\> stable population cycling

logistic growth model

describes a population whose growth is initially exponential, but slows as the population approaches the carrying capacity of the environment. the curve is S-shaped and the point of inflection is when the population is growing the fastest

logistic growth model equation

dN/dt \= rN(1-N/K)

age structure diagrams

diagrams that show population size and sex distribution

broad base \= rapid growth

narrow base \= negative growth

uniform shape \= zero growth

survivorship curve

Graph showing the number of survivors in different age groups for a particular species.

Type 1 survivorship curve

a pattern of survival over time in which there is high survival throughout most of the life span, but then individuals start to die in large numbers as they approach old age

type 2 survivorship curve

a pattern of survival over time in which there is a relatively constant decline in survivorship throughout most of the life span

type 3 survivorship curve

a pattern of survival over time in which there is low survivorship early in life with few individuals reaching adulthood who survive for a long time

life tables

track survivorship, the chance of an individual in a given population surviving to various ages

static life table

a life table that quantifies the survival and fecundity of all individuals in a population during a single time interval

cohort life table

a life table that follows a group of individuals born at the same time from birth to the death of the last individual (less frequent because this form is very intense but provides good data)

population fluctuations

The most common pattern of population growth, in which population size rises and falls over time. all population fluctiations are due to resources, predation, competition, disease, parasites, and climate

population cycles

A pattern of population fluctuations in which alternating periods of high and low abundance occur after nearly constant intervals of time.

population overshoot

Occurs when the population of a species exceeds the carrying capacity. As a result, resources run out faster and the population plummets, also decreasing the carrying capacity.

population die-off

a substantial decline in density that typically goes well below the carrying capacity (often after an overshoot)

demographic stochasticity

Random variations in birth and death rates that occur in a population from year to year

environmental stochasticity

Random variations in the environment that directly affect birth and death rates

small patch

smaller habitat patches are at a greater risk of extinction because demographic and environmental stochasticity remain the same for large and small populations but with small populations they are less likely to have a large enough number of individuals to recover

metapopulation model

A model of spatial population structure that describes a set of subpopulations occupying habitat patches between which individuals move infrequently, and in which the intervening habitat matrix is considered only as a barrier to the movement of individuals.

source patches

reproduction exceeds mortality and provides a surplus of individuals that are able to colonize and disperse to other patches

sink patches

mortality exceeds reproduction rate so that the local population will go extinct if not regularly dispersed and rescued by new immigrants

bottleneck

A change in allele frequency following a dramatic reduction in the size of a population

inbreeding depression

when individuals with similar genotypes - typically relatives - breed with each other and produce offspring that have an impaired ability to survive and reproduce. F represents the inbredding coefficient (scale of 0-1 and a higher F results in reduced fitness)

genetic drift

A change in the allele frequency of a population as a result of chance events rather than natural selection. More common in small populations

population viability analysis

is a species-specific method of risk assessment frequently used in conservation biology. It is traditionally defined as the process that determines the probability that a population will go extinct within a given number of years.

vegitative reproduction

The process by which one part of a plant can form new roots and develop into a complete plant

clones

Genetically identical cells or individuals produced by asexual reproduction

sexual reproduction benefits

Ensures genetic variability maintained in population, coping with environmental variation, coping with parasites and pathogens

mating strategies

asexual, sexual

asexual reproduction

single parent

vegatative reproduction (nonsexual tissues)

clones (genetically identical)

binary fission (bacteria divides into 2)

parthenogensis ( embryo developes without fertilization)

sexual reproduction

requires two parents

perfect flower (plants have a flower with male and female parts)

simultaneous hermaphrodite (organisms have both male and female reproductive parts)

sequential hermaphrodite (organisms are born one sex and can change to the other if necessary)

monecious flower (male and female flower of the same plant)

dioecious flower (plants only have male or female flowers)

sexual mating systems

polygamy- individuals form long-term bonds with more than one individual of the opposite sex

polygyny- males have more than one female

polyandry- femals have more than one male

monogamy- single male and female partners persist, uncommon unless the male can help raise offspring

sexual dimorphism

distinct difference in size or appearance between the sexes of an animal in addition to difference between the sexual organs themselves.

primary sex characteristics

the body structures and organs that make sexual reproduction possible

secondary sex characteristics

nonreproductive sexual characteristics in species with sexual dimorphism

competative ability and herbivory trade-offs

species can either focus more energy and resources into competing better or self protection against herbivory

forms of competition

exploitative- indirect competition, 1 species consumes the resource before the other can

interferance- direct competition, don't imediately consume resource but defend it from the other species

apparent- indirect competition, 3rd party makes it seem that two species are competing (such as a pathogen affecting only 1)

allelopath- direct competition, plants produce toxins that harm other plants

competition

the struggle between organisms to survive in a habitat with limited resources, often share a niche

commensalism

A relationship between two organisms in which one organism benefits and the other is unaffected

mutualism

A relationship between two species in which both species benefit

predation/parasitism

one species benefits and the other is harmed or affected

seeds, fruits, and dispersal pathways

fruits are eaten by other organisms and dispersed by those species after excretion

seeds can be dispersed multiple ways, like by wind, pollination, water, fire, animals, and more

ecotones

a boundary between two types of ecological communities

effects of resources on abundance

patterns can be

U-shaped (populations are largest at low and high densities of resources)

negative (populations decline with increased resources)

none (populations are not affected by resources)

positive (populations increase with resources)

hump-shaped (populations are highest at mid levels of resources, most common. medium productivity yields the highest richness)

top-down control

when the abundance of trophic groups is determined by the existence of predators at the top of the food web

bottom-up control

when the abundances of trophic groups are determined by the amount of energy available from producers

species-area relationship

the relationship between area surveyed and number of species encountered; the more area sampled yields more species found

species-area curve

S \= cA^2

or represented as log:

logS \= logC + zlogA

species diversity metrics

species richness- \# number of species present

species diversity- metrics reflecting species diversity and eveness

species diversity measurements

alpha diversity (local)- \# species in a relatively small area of homogenous habitat

gamma diversity (regional)- \# species present in all habitats comprised of a large geographic area

beta diversity- \# species difference between two habitats