Factors that Affect Populations• By Mr. Guardiola• Chapter 5• TEKS 12d,

5-1 How populations grow.1. What are the 4 characteristics of populations?

A. Geographic distribution—also known as the “range,” describes the area where the organisms live

B. Population Density—is the number of individuals per unit area

1. Formula Population Density= Individuals/Area

C. Growth RateD. Population’s Age Structure

2. What three factors affect population growth?

A. Number of BirthsB. Number of DeathsC. Emigration/Immigration

3. What two forms of growth can there be?A. Exponential Growth—occurs when the individuals in a

population reproduce at a constant rate.1. There must be an unlimited amount of resources such as

food, water, and living space.

B. Logistic Growth—occurs when a population’s growth slows or stops following a period of exponential growth.

1. Can occur when resources will become less available, death rates increase, or when birth rates decrease.

Comparison of GrowthsLogistic Growth Curve

Exponential Growth Curve

5-2 Limits to Growth

1. What is a limiting factor? Something that causes population growth to

decrease There are two main kinds of limiting factors

2. What are 4 examples of density-dependent limiting factors?

A. Competition among organisms for food, water, living space, sunlight, etc.

B. Predation—Predator-Prey Relationships– When prey populations increase, so will predator

populations. This will then cause prey populations to decrease, which will also cause predators to decrease.

3. What are examples of density-independent limiting factors?

• Natural disasters—Drought, hurricanes• Human Activities—building dams,

deforestation

• This kind of limiting factors affects every population.

What is a biosphere?

• It’s the part of the planet that contains all life.– Includes land,

water and air.

What are the parts of a biosphere?

• There are six parts (simplest to complex)1. Species—a group of organisms that can

interbreed with one another (i.e. wolf)2. Population—Groups of individuals that

belong to the same species and live in the same area (pack of wolves)

3. Communities—a group of different populations that live together in a defined area (pack of wolves, deer, bobcats)

What are the parts of a biosphere?

4. Ecosystem—collection of all the organisms that live in a particular place (pack of wolves, deer, grass, rivers, plains)

• This includes nonliving material

5. Biome—Group of ecosystems that have the same climate and dominant communities (deserts, tropical rainforests, tropical dry forests, etc.)

6. Biosphere—