Chapter 8 Understanding Populations Bellringer: You have just been offered a job that will last one month. You have two salary options: Receive $10 per week with a $5 per week raise every week. Receive one penny for your 1st day on the job and then double the previous day’s pay for each of the remaining 30 days.

I. What is a Population? __________ members of a species living in the same place at the same time Population Populations are also reproductive groups A group of loblolly pines in central Alabama cannot reproduce with a group of loblolly pines in eastern South Carolina Population also can refer to the size of a group…the human population

II. Properties of a Population Three factors describe a population: Size - the number of organisms in the population Density – Number of individuals per unit area or volume Dispersion – Distribution or arrangement of the individuals within the population

There are three types of dispersion: Even Clumped Random

Change in Population Size III. How Does a Population Grow ___________ change in size of a population over a given period of time Growth Rate Change in Population Size Births Deaths Population Increase Births Deaths Population Decrease Births Deaths

IV. How Fast Can a Population Grow? _____________ fastest rate at which a population can grow Biotic potential Biotic potential is limited by __________________ which is the maximum number of offspring a population can produce reproductive potential Reproductive potential varies by species Increases when organisms have many offspring at once Decreases when organisms have few offspring at once

Exponential Growth – populations that grow extremely FAST Example: 2 → 4 → 8 → 16 → 32 → 64 → 128, etc… Only occurs when there is: plenty of food plenty of space no competition no predators

V. What Limits Population Growth? _______________, the maximum number of organisms that can be supported Carrying Capacity

Carrying capacities are reached when: Species consume a natural resource at the same rate at which the ecosystem can produce the resource Competition occurs between members of a population for a specific resource

densely populated environments VI. Two Types of Population Regulation Density dependent – death within a population occur in… Crowed conditions Areas with limited resources Predation Disease densely populated environments Density independent – death within a population occurs regardless of resources available or population density