Population dynamics Exponential Growth Exponential growth of a

Population dynamics

Exponential Growth Exponential growth of a population of organisms occurs when the # of organisms rises at an everincreasing rate.

Population Growth of Houseflies Population size 1 million 500, 000 100 One year

What are some things that prevent populations from growing exponentially?

Carrying Capacity The number of organisms that a particular environment can support over an indefinite period of time. – Births will exceed deaths until carrying capacity is reached

Number of Yeast Cells Carrying capacity Time (hours)

4 population growth graphs

Exponential vs. Logistic growth

Limiting factors 1. 2. 3. Density-dependent Density-independent Predation

Limiting factors 1. 2. 3. Density-dependent – Have an increasing effect as population increases – Ex. Disease, parasites, competition, crowding & stress Density-independent – Affects all populations, regardless of their density – Usually abiotic factors: ex. storms, floods, temp, fire Predation – keeps population size within limits (density-dependent)

Practice Classify each of the following as either densitydependent or density-independent. 1. Intense heat wave 2. Large population of caterpillars infected with wasp larvae parasites 3. Overpopulation of an organism 4. Clear cutting of a forest to build a shopping center.

Exotics Species living in an area to which they are not native Can be introduced accidentally or on purpose Ex. Sika from Asia brought to South TX

n How do you think introducing Sika into the population would affect the native population of deer?

Swamp Rats in California

https: //www. mysanantonio. com/bayarea/article/nutri a-should-we-eat-invasive-species-swamp-rats 12726054. php#photo-15020981