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 Growth Rate 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 capacity the 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 factors any condition of the environment that limits the size of a population regulates population growth!

Humans & Carrying Capacity How humans increase our carrying capacity? Agriculture (Green Revolution) Industry/technology-improved sanitation systems 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

Predation All consumers are predators! Inverse relationships with prey & predators Greatest effect on large populations

Competition Occurs when organisms try to make use of the same resources Compete for food, water, mates, space Can be between same or different species

Parasitism Relationship 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 models J-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

Communities group 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