CH BIO 37 Extended versson !

Ecology

The study of how organisms interact with each other and with their environment.

Population

Interbreeding organisms of one species occupying the same area.

Community

All species occupying the same area.

Ecosystem

The biotic community plus the abiotic (nonliving) environment.

Habitat

The physical location where members of a population live.

Processes determining population growth or shrinkage

Births, deaths, immigration, emigration.

Population size

The total number of individuals of a species.

Best sampling method for non-mobile population

Quadrat sampling.

Best sampling method for mobile population

Mark-and-recapture.

Mark-and-recapture equation

N = (M × C) / R; M = number marked initially, C = total captured later, R = number of marked recaptured.

Population density

The number of individuals per unit area.

Population distribution patterns

Clumped, uniform, random.

Distribution for territorial species

Uniform.

Distribution for species sharing a resource

Clumped.

Distribution in a homogeneous, noncompetitive environment

Random.

Factors affecting population growth rates

Birth rate, death rate, immigration, emigration.

Age structure

The distribution of age classes within a population.

Mostly young population

High potential for rapid growth.

Few young individuals

The population will decline.

Equal age distribution

The population is stable.

Survivorship curves

Show the proportion of surviving individuals at each age.

Life tables

Follow a group of individuals from birth to death.

Type I survivorship curve

High survival until old age; example: humans.

Type II survivorship curve

Constant death rate at all ages; example: birds.

Type III survivorship curve

High juvenile mortality; example: oysters or many fish.

Exponential growth formula

G = rN (or dN/dt = rN).

Shape of exponential growth curve

J-shaped.

Why exponential growth is unrealistic

Limited resources and environmental resistance prevent indefinite growth.

Logistic growth

Growth that slows as the population approaches carrying capacity; includes environmental limits.

Shape of logistic growth curve

S-shaped.

Environmental resistance increases due to

Limited resources, competition, predation, disease.

Carrying capacity (K)

The maximum population size the environment can sustain.

Logistic growth formula

G = rN (1 – N/K).

Difference between exponential and logistic growth

Logistic includes carrying capacity (K), limiting growth.

Density-dependent factors

Factors whose effects increase as population density increases.

Density-independent factors

Factors unrelated to population density.

Example of density-dependent factor

Competition or disease.

Example of density-independent factor

Natural disasters or weather.

Life history analysis focus

Adaptations that influence reproductive success.

r-selected species

Many offspring, little parental care; example: insects.

K-selected species

Few offspring, high parental care; example: elephants.

Reason for rapid human population growth in developing countries

High birth rates and low death rates.

Demographic transition

A shift from high birth/death rates to low birth/death rates as a country develops.

Stage 2 of demographic transition

High birth rate, declining death rate, rapid population growth.

Stage 3 of demographic transition

Declining birth rate, low death rate, slowing population growth.

Ecological footprint

The amount of land and resources needed to support an individual's lifestyle.

Challenges of overpopulation

Resource depletion, habitat loss, pollution, food shortages, increased disease spread.

Why exponential growth is rare

Environmental limits and resource shortages restrict long-term growth.

What constant population size indicates

Birth rates equal death rates.

Survivorship curve for species producing many offspring but few surviving

Type III.

Effect of changing carrying capacity on stability

Increased K allows larger stable populations; decreased K causes declines or instability.

How life history strategies help endangered species management

Identify survival and reproduction limits to guide conservation efforts.