1. Understanding Populations
Ch.8

2. 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

4. 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

6. 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 =

7. 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?

8. 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

9. 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

10. 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

11. Carrying Capacity

12. 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

13. Competition

15. 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

16. Density Independent Density dependent

17. 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