Understanding Populations Ch.8

What is a population? All the members of a species living in the same place at the same time Organisms usually breed with members of the same population Python

Properties Size-How many organisms make it up Density-number of individuals per unit area or volume Dispersion- how the individuals are arranged within a given space Even, clumped, random

How does a population grow? Growth rate- change in a populations' size over time Positive growth rate = More births than deaths Negative growth rate = more deaths than births Zero growth rate = average # of births is equal to average # of deaths Change in population size Births Deaths =

DO NOW Hand- in Homework Describe the curve and explain how it shows exponential growth? What would the line look like if it showed linear growth? How does exponential growth relate to reproductive potential?

Factors that control how fast a population grows 1. Reproductive potential: Maximum # of offspring each member in a population can produce Reproductive potential increases when more offspring are produced, more often & earlier Generation time- time it takes for offspring to be able to reproduce *Darwin calculated 750yrs to produce 19 million elephants / Bacteria 19million in a few days

More factors 2. Exponential Growth- A population grows faster & faster Large # of individuals are added to the population in each succeeding time period FACTORS: Food, space, competition Exponential growth= J curve

Factors that limit population growth 1. Carrying capacity: The maximum number of a particular species that the ecosystem can support Hard to predict because ecosystems change- can be estimated

Carrying Capacity

Continued… 2. Resource limits: Organisms consume the same resource at the same rate as the resource is replaced (limiting resource) This determined carrying capacity 3. Competition w/ a population: Members of a population use the same resources, so they end up competing with each other as the resource becomes limited Ex- food, social dominance, territory Carrying capacity video clip

Competition

2 types of population regulations Density dependent: Deaths occur more quickly in crowded population than in sparse Density Independent: Part of a population dies regardless of its density Natural disasters, severe weather

Density Independent Density dependent

Exit Quiz Which of the following is one of the main properties used to describe a population? a. number of individuals c. number of species b. color of individuals d. kind of adaptations 2. Exponential growth occurs when a population a. exceeds the habitat’s carrying capacity. b. is competing with another species. c. grows increasingly faster. d. breeds with another species. 3. Which of the following limits a population’s growth? a. carrying capacity of its habitat c. severe weather b. natural disasters d. all of the above