Section 14.1 Habitat and Niche

KEY CONCEPT

Every organism has a habitat and a niche.

A habitat differs from a niche.

• A habitat is all aspects of the area in which an organism

lives.

– biotic factors

– abiotic factors

• An ecological niche

includes all of the

factors that a

species needs to

survive, stay healthy,

and reproduce.

– food

– abiotic conditions

– behavior

Resource availability gives structure to a community.

• Species can share habitats and resources.

• Competition occurs when two species use resources in the

same way.

• Competitive exclusion keeps two species from occupying

the same niche.

• Competitive exclusion has different outcomes.

– One species is better suited to the niche and the other

will either be pushed out or become extinct.

– The niche will be divided.

– The two species will further diverge.

Resource availability gives structure to a community.

• Ecological equivalents are species that occupy similar

niches but live in different geographical regions.

Madagascar

South America

Resource availability gives structure to a community.

• An organism’s range of tolerance is the entire set of

conditions, such as air temperature or soil moisture, under

which an organism is potentially able to survive.

Resource availability gives structure to a community.

Section 14.2 Community Interactions

KEY CONCEPT

Organisms interact as individuals and as populations.

Competition and predation are two important ways in

which organisms interact.

• Competition occurs when two organisms fight for the

same limited resource.

– Intraspecific competition – same species

– Interspecific competition – different species

• Predation occurs when one organism captures and eats

another.

Competition and predation are two important ways in

which organisms interact.

• There are three major types of symbiotic relationships.

– Mutualism: both organisms benefit

Competition and predation are two important ways in

which organisms interact.

– Commensalism: one organism benefits, the other is

unharmed

Human Our eyelashes

are home to tiny mites

that feast on oil

secretions and dead

skin. Without harming

us, up to 20 mites may

be living in one eyelash

follicle.

Demodicids Eyelash

mites find all they need to

survive in the tiny follicles

of eyelashes. Magnified

here 225 times, these

creatures measure 0.4

mm in length and can be

seen only with a

microscope.

+

Organism benefits +

Ø

Ø Organism is not affected

Commensalism

• There are three major types of symbiotic relationships.

Competition and predation are two important ways in

which organisms interact.

– Parasitism: one organism benefits, the other is harmed

• There are three major types of symbiotic relationships.

Organism benefits 0

_

Organism is not affected

Hornworm

caterpillar

The host hornworm

will eventually die as

its organs are

consumed

by wasp larvae.

Braconid

wasp

Braconid larvae

feed on their

host and

release

themselves

shortly before

reaching

the pupae

stage of

development.

_

Parasitism

+

0

Competition and predation are two important ways in

which organisms interact.

• There are three major types of symbiotic relationships.

– Parasitism meet their needs as ectoparasites (such

as leeches) and endopaasites (such as hookworms)

Competition and predation are two important ways in

which organisms interact.

Section 14.3 Population Density and Distribution

KEY CONCEPT

Each population has a density, a dispersion, and a

reproductive strategy.

Population density is the number of individuals that live

in a defined area.

• Population density is a measurement of the number of

individuals living in a defined space.

• Scientists can calculate population density.

• Population dispersion refers

to how a population is spread in

an area.

Geographic dispersion of a population shows how

individuals in a population are spaced.

Clumped

dispersion

Uniform

dispersion

Random

dispersion

• There are three types of dispersion.

– clumped

Geographic dispersion of a population shows how

individuals in a population are spaced.

• There are three types of dispersion.

– uniform

Geographic dispersion of a population shows how

individuals in a population are spaced.

• There are three types of dispersion.

– random

Geographic dispersion of a population shows how

individuals in a population are spaced.

Survivorship curves help to describe the reproductive

strategy of a species.

• A survivorship curve is a diagram showing the number of

surviving members over time from a measured set of births.

• Survivorship curves can be type I, II or III.

• Type I: low level of infant mortality and an older

population

– common to large mammals and humans

• Type II: survivorship rate is equal at all stages of life

– common to birds

and reptiles

• Type III: very

high birth rate,

very high infant

mortality

– common to

invertebrates

and plants

Survivorship curves help to describe the reproductive

strategy of a species.

Section 14.4 Population and Growth Patterns

KEY CONCEPT

Populations grow in predictable patterns.

Changes in a population’s size are determined by

immigration, births, emigration, and deaths.

• The size of a population

is always changing.

• Four factors affect the

size of a population.

– immigration

– births

– emigration

– deaths

Population growth is based on available resources.

• Exponential growth is a rapid population increase due to

an abundance of resources.

• Linear growth continues to increase at the same rate.

Population growth is based on available resources.

Ecological factors limit population growth.

• A limiting factor is something that keeps the size of a

population down.

• Density-dependent limiting factors are affected by the

number of individuals in a given area.

• Density-dependent limiting factors are affected by the

number of individuals in a given area.

– parasitism

and disease

– predation

– competition

Ecological factors limit population growth.

• Density-independent limiting factors limit a population’s

growth regardless of the density.

– unusual weather

– natural disasters

– human activities

Ecological factors limit population growth.

Section 14.5 Ecological Succession

KEY CONCEPT

Ecological succession is a process of change in the

species that make up a community.

Succession occurs following a disturbance in an

ecosystem.

• Succession regenerates or creates a community after a

disturbance.

– a sequence of biotic changes

– damaged communities are regenerated

– new communities arise in previously uninhabited areas

• There are two types of succession.

– primary succession — started by pioneer species

Succession occurs following a disturbance in an

ecosystem.

• There are two types of succession.

– secondary succession — started by remaining species

Succession occurs following a disturbance in an

ecosystem.