Interactions in Populations

Chapter 14

Habitat and Niche Habitat

All the biotic and abiotic factors in an area where an organism lives

Niche All the physical,

chemical, and biological factors needed to survive

Habitat and Niche• Competitive Exclusion Principle

Two species competing for the same resources

One will be better suited than the other One species will be pushed into another niche

Habitat and NicheSecondary Outcomes of

Competitive Exclusion Niche Partitioning

• Dividing the niche so two species can share

Evolutionary Response• Divergent evolution could take place

to allow two species to survive

Habitat and NicheEcological

Equivalants Similar species

with similar niches in different geographical regions

Sign of convergent evolution

Emerald Tree Boa – South America

Green Tree Python - Australia

Community Interactions Competition – when organisms try to

use the same ecological resources• Resources – any necessity of life• Interspecific Competition• Intraspecific Competition

Community Interactions

Predation – one organism captures and feeds on another• Predator• Prey

Community Interactions Symbiosis – any relationship where two

species live closely together

Community Interactions• Mutualism – both species benefit

Community Interactions• Commensalism – one species

benefits the other is unharmed

Community Interactions

• Parasitism – one species benefits and the other is harmed

Population Density and Distribution

Characteristics of Populations Geographic

distribution – the area inhabited by a population

Population density – the number of individuals per unit area

Population Density and Distribution

Population DispersionThe amount populations are

spread out in relation to one another•Clumped•Uniform•Random

Population Density and Distribution

Survivorship Curves Number of

individuals surviving over time• Type I• Type II• Type III

Population Density and Distribution

Type I Common

among large mammals

Low infant mortality

Generally long life

Population Density and Distribution

Type II Birds, small

mammals, some reptiles

Constant threat of death

Population Density and Distribution

Type III Invertebrates,

fish, amphibians, plants

High infant mortality rate

Population Growth PatternsPopulation Growth

– birth rate, death rate, or migration Immigration – the

movement into an area

Emigration - the movement out of a area

Population Growth Patterns

Exponential Growth – individuals reproduce at a constant rate

Under ideal conditions, a population will grow exponentially.

Population Growth PatternsLogistic Growth –

populations growth slows or stops following a period of exponential growth Carrying capacity –

the largest number of individuals that the environment can support• Population Crash

Population Growth PatternsLimiting Factors – something that

causes population growth to decrease

Population Growth PatternsPatterns of

Population Growth Demography – the

scientific study of human populations

Population Growth Patterns Demographic

Transition – a dramatic change in the birth and death rates• U.S., Europe, and

Japan• China and India

Population Growth Patterns Age Structure

• What does it mean if there are lots of older people?

• What does it mean if there are lots of younger people?

Population Growth Patterns Future Population

Growth Is the human

population increasing? Will the human

population continue to increase forever?

What factors will cause the human population to slow?

Population Growth PatternsDensity-dependent factors – limiting

factor that depends on population size

Population Growth PatternsDensity-independent

factors – factors that affect all populations regardless of size Weather Natural disaster Seasons Human activities

Ecological Succession

Ecological Succession

Ecological Succession Primary Succession – new species

grow where no soil exists

Ecological Succession Secondary Succession – a

disturbance changes the existing community without removing the soil