Populations!

definition= a group of organisms of the same species that live in a particular area*Evolve over generations when frequency of alleles change from one generation to the next

Population GrowthRate at which a population grows depends

on:

1. Birth rate

2. Death rate

3. Immigration (moving into a population)

4. Emigration (moving out of a population)

Carrying capacitythe number of organisms that can be

supported by the environmental resources in a given ecosystem

prevents populations from growing out of control!

controlled by limiting factorsany condition of the environment that

limits the size of a populationregulates population growth!

Humans & Carrying CapacityHow humans increase our carrying capacity?

1. Agriculture (Green Revolution)

2. Industry/technology-improved sanitation systems

3. Medicine (example: Penicillin, antibiotics)

Determined by:

Biotic (living) factors- any organism

Abiotic (non-living) factors- rocks, weather, temperature

Types of Limiting factors

1. Density-dependent factor

- limit population size when the population reaches a certain size

- usually biotic factors

Examples: predation, competition, parasitism, disease

PredationAll consumers are

predators!

Inverse relationships with prey & predators

Greatest effect on large populations

CompetitionOccurs when

organisms try to make use of the same resources

Compete for food, water, mates, space

Can be between same or different species

ParasitismRelationship where one organism feeds

on the tissues/body fluids of another organism

Member benefits: Parasite

Member harmed: Host

Types of Limiting factors cont.

2. Density-independent factor

- limit population size regardless of overall size

- usually abiotic factors

Examples: natural disasters, weather

- cause Boom-and-bust curves

= exponential growth followed by a sudden collapse

Growth modelsJ-shaped curve

= exponential growth

- high birth rate, low death rate

-ideal conditions

Example: Algae blooms

- indicate excess of fertilizers (lots of nutrients available)

Growth models cont.S-shaped curve

- birth rate = death rate

- occurs when density-dependent factors become limited

- carrying capacity is reached!

- usually observed in larger organisms

Communitiesgroup of interacting populations of

different species that occupy the same area at the same time

Example: your backyard (grass, trees, flowering plants, insects, rabbits, squirrels, etc.

Ecosystems

Includes both biotic & abiotic factors

Biodiversity!

terrestrial or aquatic

Biomes are more defined, based on temperature, precipitation differences, and specific plant and animal life