Populations

Rates That Affect Population Size Natality- the birth rate; the number of births over time Mortality- the death rate; the number of deaths over time

Rates That Affect Population Size Immigration- the rate of individuals entering the population from a different population; the number of individuals entering over time Emigration- the rate of individuals leaving a populations to go to a different population; the number of individuals leaving a population

Population Growth Two Types of Growth: – Exponential – Logistic

Exponential Growth Occurs when the individuals in a population reproduce at a constant rate Under ideal conditions with unlimited resources, a population will grow exponentially

Exponential Growth J-Curve

Logistic Growth Occurs when a population's growth slows or stops following a period of exponential growth

Logistic Growth S-Curve

Carrying Capacity- the maximum population size that environment can sustain. – Usually determined by a limiting factor As resources become less available the growth of a population slows or stops.

New or early populations show exponential growth Old, stable populations show no growth, but stay near the carrying capacity of the environment

What happens if a population exceeds its carrying capacity?

If a population exceeds the carrying capacity of its environment, the carrying capacity decreases

Human Population Is the human population growing exponentially or logistically?

Niches and Communities Niche - range of physical and biological conditions in which a species lives and the way the species obtains what it needs to survive and reproduce. Different Factors: – Tolerance – ability to survive and reproduce under a range on environmental circumstances.

Tolerance Graph

Niche cont. Resources – food, water, nutrients, etc Physical – abiotic factors Biological – biotic factors Competition – exactly what you would think Competitive Exclusion Principle – no two species can occupy exactly the same niche in exactly the same habitat at exactly the same time.

Predator-Prey Relationships Predation – interaction in which one animal (predator) eats another animal (prey) – Predators affect the size of prey populations within a community and determine the places where the prey can live. Herbivory – Same concept at predation just with plants

Predator-Prey Graph

Symbioses Two creatures living in harmony and helping each other survive. Mutualism – both benefit (Clown fish – Anemone) Parasitism – one organisms lives inside or on another organisms and harms it (Tapeworms) Commensalism – one organism benefits and the other is neither harmed nor helped. (Barnacles and Whales)