Population Ecology. Population Essential Questions What factors influence populations in ecosystems?...

Population Ecology

Population Essential Questions

What factors influence populations in ecosystems? How do human population dynamics affect the world we live in?

What is a population?A group of the same species living in a

geographic area

Important Note: So a population is made up of individuals. But, multiple populations make up a community.

Quantifying Population

• Three key features:– Population size– Population density– Population distribution

Population Size

• Number of individuals in an region

Population Density• Number of individuals within a population per

unit area

Population Distribution• The spatial arrangement of organisms within

an area

clumped

uniform

random

Population Distribution

Unregulated populations increase by exponential growth

Quick Think: In this model, a population will get bigger and bigger forever! Do you think that is really possible?

Logistic Growth Model

Carrying Capacity (K)

Quick Think: What are some things that may cause population growth to slow down?

Limiting factors prevent endless population growth

• Limiting factors: physical, chemical, and biological characteristics of the environment that restrain population growth

• Limiting factors are also referred to as “environmental resistance”

• Carrying capacity: maximum population size that the environment can sustain

Quick Think: Is the carrying capacity the same for all populations? Why or why not?

Examples of limiting factors

• Space• Sunlight• Availability of:– Food– Water– Mates and breeding sites– Shelter

• Temperature• Nutrients• Pollutants

The influence of some factors depends on population density

Density-dependent factors

DiseaseCompetitionFinding matesParasites

Density-independent factors

TemperatureStormsHabitat DestructionDrought

Reproductive strategies• Biotic potential – ability to produce offspring