Population Ecology 5.01 Investigate and analyze the interrelationships among organisms, populations, communities, and ecosystems

What is a population?

What causes changes in population size?   Three factors can affect population size: the number of births, the number of deaths, and the number of individuals that enter or leave the population. Simply put, a population will increase or decrease in size depending on how many individuals are added to it or removed from it.

Collecting data about population size More often than not, the size of a population has to be estimated

Techniques of field ecology Random sampling and quadrant analysis are used to estimate the changes occurring in populations over time.

Population density

Carrying capacity The maximum number of individuals in a population that the environment can support (has resources for) This is determined by both biotic and abiotic factors

Abiotic and Biotic factors Abiotic: weather, natural disasters, available O2, pH, temperature, minerals, moisture Biotic: food, predators, mates, parasites

Population growth graphs J- curves show exponential growth (explosive) 101 = 10; 102 = 100; 103 = 1000

Population growth graphs An s-shaped curve shows a stable population

Limiting factors Density independent and Density dependent limiting factors control carrying capacity

Human Populations Humans are still in the exponential growth phase The big question is when will our species meet it’s carrying capacity.

Why are we interested in the rate of population growth?

Resources Does a population exist independently?

If the population of rabbits declined, what might happen to the others?