AP BIO CH 53 VOCAB

Population Ecology

The study of populations in relation to their environment. It includes exploring how biotic and abiotic factors influence the density

Population

Individuals of the same species living in the same area. The boundaries of the area are usually defined early on in an ecological study.

Population density

The number of individuals per unit area (or per unit volume)

Population Dispersion

The pattern of spacing among individuals within a population

Population Dynamics

This refers to the way a population changes due to birth

Immigration

The influx of individuals from outside the the area in which a population lives.

Emigration

The movement of individuals out of the area in which a population lives.

Clumped dispersion

When individuals gather together in groups. This can occur due to attractions between individuals and/or when individuals all come to the same favorable area.

Uniform dispersion

When individuals tend to be evenly spaced. This can occur where competition between individuals for limited resources results in territoriality.

Territoriality

The defense of a bounded space against any individual of the same species that encroaches on it.

Random dispersion

When the position of each individual in a population is not related to that of other individuals. This occurs when there are no major attractions or repulsions between individuals.

Dandelions

A species of plant

Demography

The study of the characteristics of a population (especially human populations)

Life Tables

A representation of the survivorship of individuals in a population at each age.

These were initially developed by life insurance companies as a way of estimating how long an individual was likely to live.

Survivorship curve

A graphical representation of some of the information from a life table.

Type 1 Survivorship

Characterized by low death rates for young individuals and high death rates for old individuals. It is typical of humans and other large mammals that produce few offspring but that care closely for the offspring.

Type II Survivorship

Death rates are relatively constant over the lifespan of the cohort. This was observed for the ground squirrels.

Type III Survivorship

Involves high death rates for young individuals and low death rather for old individuals. It is characteristic of species that produce large numbers of offspring but where parents do not protect the offspring

Reproductive table

A representation of the reproduction of individuals in a population at each age.

Reproductive rate

The average lifetime number of offspring produced by an individual over a lifespan.
(usually focused on females)

Population growth is mostly determined by

Reproduction and Survivorship (Births and Deaths)

Exponential population growth model

Also called the geometric population growth model.

The rate of change of the population is equal to a constant times the population. dN/dt = rN

Uppercase Greek letter "Delta"

Change

t

time

N

The number of individuals in a population.

Also called the size of the population.

d

instantaneous change

dN/dt

The rate of change of population at a moment in time.

∆N/∆t

The change in the size of a population over a defined time span.

r

The per capita rate of increase.

The average increase in population per unit of time per individual

= b - m

b

The per captia birth rate.

The average number of offspring born per unit of time per individual

m

The per capita death rate ( or mortality rate)

The average number of deaths per unit of time per individual

J shaped curve

The shape of an exponential growth curve: it starts to grow slowly and then increases faster and faster. The proportional rate of increase is constant

Exponential population growth model can be accurate when

There are no limits to growth imposed by lack of food

If the constant r is smaller

then

If the population (N) is bigger

The rate of population growth (dN/Dt ) is bigger

Logistical population growth model

A mathematical representation of a population that grows exponentially for small populations

Carrying capacity

The maximum population in the logistical model

K

The letter used to represent carrying capacity: the maximum population value in the logistical growth model.

S -shaped curve

The shape of a logistical growth curve. the growth rate reaches a maximum in the middle of the curve.

life history traits

For a particular species this refers to when reproduction begins

Semelparity

Also called big bang reproduction: it refers to species that have a single reproductive episode resulting in many offspring before death..

Iteroparity

This refers to species that have several reproductive episodes over the course of a lifetime.

Semelparity is favorable

In highly variable and unpredicatable environments where survivorship is generally low

Iteroparity is favorable

In environments that are stable and where survivorship is high

Kestrel

A bird of prey focused on in a study that found that survivorship of parents was reduced after caring for a larger brood of young. this illustrates a trade off between reproduction and survival.

r-selection

Evolutionary pressure that drives reproductive strategies based on maximizing the reproductive rate: i.e. producing lots of young.

Also called density independent selection

K-selection

Evolutionary pressure that drives reproductive strategies based on maximizing the offspring's ability to compete for limited resources. i.e. producing few young and supporting them.

Also called denisty dependent selection