Bell Ringer 12.4

1. What impact does CO2 have on the environment?(List at least one positive and one negative)2.

What causes global warming?3.

What causes global cooling?4.

What would happen to the nitrogen cycle without decomposers?

Populations

Populations are dynamic (always changing)

•Change in size and composition

•Birth rate•Death rate•Migration

Growth of a population is affected by migration

•Immigration – into an area•Emigration – exiting an area

How is the size of a population measured?

Census count of ALL organisms in a population

This is not always easy to do, especially if the organisms are microscopic or move too quickly to count.

1. Quadrant method divides area into grids, counts the number in a grid, multiply by the number of grids in area

* good for organisms that move very little or not at all.

Sampling estimating population size using samples

2. Mark-recapture captures a sample, marks the organisms caught, later captures another sample, uses the number of previously marked to estimate population size.

* Good for organisms that move around a lot

Behaviors

•Behaviors that occur within a population•Usually referred to as social behaviors

and involve some form of communication.

•Communication among members of the same species can be by…

1. Sound

2. Scent (uses chemicals called pheromones)

3. Dances (for direction or courtship)

Bee Waggle DanceCourtship dance of Wolf Spider

Courtship of Flamingos

Another social behavior is territorial defense

Ex: fighting fish, lions, green turtles, wolves, etc.

Green Turtles & Territorial Defense

Population Pyramids•Show the characteristics of a population

in the form of a double bar graph.•Shows age and sex distribution of a

population•LEFT shows a county with RAPID growth;

RIGHT shows a county with STABLE growth.

1. Which city has an upside down population pyramid? (meaning: there are more elderly people than young people).

2. Look at the population pyramid of Honolulu, HI (bottom). Would you say that its population is growing quickly, slowly, or not at all?

Population Growth

1. Unlimited known as Exponential Growth

▫Produces J shaped curves

2. Limited when growth reaches carrying capacity.

▫CARRYING CAPACITY = maximum number of organisms an environment can support.

▫Produces S shaped curves

Growth of a population can be limited by limiting factors•Food•Water•Shelter•Harsh weather•mates

Which of the following graphs represents a population that has reached a state of equilibrium?A. B.

C. D.

Which statement best describes the growth pattern of a population of organisms in nature?

A. It is limited by environmental factors.

B. It continues to grow indefinitely.

C. It is genetically determined.

D. It never changes.

Which of the following global concerns is indirectly responsible for all the others?

A. Waste disposal

B. Resource depletion

C. Overpopulation

D. Poor sanitation