Population GrowthPopulation Growth

How do communities change over time?

How do communities change over time?

Characteristics of PopulationsCharacteristics of Populations• Geographic distribution- describes the

area inhabited by a population• Distribution density- the number of

individuals per unit area• Growth rate- increase/decrease per unit

time• Age Structure-how many people of

different ages make up a given population

• Geographic distribution- describes the area inhabited by a population

• Distribution density- the number of individuals per unit area

• Growth rate- increase/decrease per unit time

• Age Structure-how many people of different ages make up a given population

Population GrowthPopulation Growth• Number of births (birth rate)• Number of deaths (death rate)• Movement into a population (immigration) and

movement out of a population (emigration)Examples:

• Number of births (birth rate)• Number of deaths (death rate)• Movement into a population (immigration) and

movement out of a population (emigration)Examples:

• ↑ birth rate + ↓ death rate= ↑ pop. growth• ↑ birth rate + ↑ death rate = ↔ pop. Growth• ↑ immigration = ↑ pop. Growth• ↑ emigration = ↓ pop. Growth• Immigration = emigration = ↔ pop. growth

• ↑ birth rate + ↓ death rate= ↑ pop. growth• ↑ birth rate + ↑ death rate = ↔ pop. Growth• ↑ immigration = ↑ pop. Growth• ↑ emigration = ↓ pop. Growth• Immigration = emigration = ↔ pop. growth

Population growthPopulation growth

• Populations will grow until they reach their biotic potential, unless they are limited by factors in the environment

• This type of growth is known as a J-curve

• Populations will grow until they reach their biotic potential, unless they are limited by factors in the environment

• This type of growth is known as a J-curve

Exponential GrowthExponential Growth

• Occurs when the individuals in a population reproduce at a constant rate– Under ideal conditions with

unlimited resources

• Occurs when the individuals in a population reproduce at a constant rate– Under ideal conditions with

unlimited resources

Fill It In …Fill It In …

Define “exponential growth”:Define “exponential growth”:

Population growthPopulation growth

• Limiting factors, such as availability of food, water, and space establish a carrying capacity for populations

• This type of growth is known as a S-curve.

• Limiting factors, such as availability of food, water, and space establish a carrying capacity for populations

• This type of growth is known as a S-curve.

Logistic GrowthLogistic Growth

• Occurs when a population’s growth slows or stops following a period of exponential growth

• Occurs when a population’s growth slows or stops following a period of exponential growth

•As resources become less available, the growth of a population slows or stops

Fill It In …Fill It In …

List limiting factors for a population of dandelions:

List limiting factors for a population of dandelions:

Population growthPopulation growth

• Carrying capacity is defined as the number of individuals an environment can support.

• Carrying capacity is defined as the number of individuals an environment can support.

Population growthPopulation growth

• Limiting factors in the environment help to maintain ecosystem stability by allowing populations to fluctuate around the carrying capacity.

• This is called dynamic equilibrium.

• Limiting factors in the environment help to maintain ecosystem stability by allowing populations to fluctuate around the carrying capacity.

• This is called dynamic equilibrium.

Population growthPopulation growth• Density dependent

factors have a greater effect on a population when there is a higher population density (the number of individuals in a given space).

• For example, competition, predation, and the spread of infectious diseases are density-dependent factors.

• Density dependent factors have a greater effect on a population when there is a higher population density (the number of individuals in a given space).

• For example, competition, predation, and the spread of infectious diseases are density-dependent factors.

Population growthPopulation growth• Density independent

factors influence the size of a population regardless of its density.

• For example, natural disasters such as forest fires are density independent factors.

• Density independent factors influence the size of a population regardless of its density.

• For example, natural disasters such as forest fires are density independent factors.

Age StructureAge Structure

Check Yourself!Check Yourself!

1. What kind of curve illustrates exponential growth?

2. What determines the carrying capacity of the environment?

3. List 3 examples of limiting factors.

1. What kind of curve illustrates exponential growth?

2. What determines the carrying capacity of the environment?

3. List 3 examples of limiting factors.

Population growthPopulation growth• Succession is the

idea that communities will replace other communities in a predictable, orderly way; this happens because every community alters the physical factors of the environment.

• Ex. As trees grow, they produce shade.

• Succession is the idea that communities will replace other communities in a predictable, orderly way; this happens because every community alters the physical factors of the environment.

• Ex. As trees grow, they produce shade.

Check Yourself!Check Yourself!

1. What kind of curve illustrates exponential growth? J-CURVE

2. What determines the carrying capacity of the environment?

3. List 3 examples of limiting factors.

1. What kind of curve illustrates exponential growth? J-CURVE

2. What determines the carrying capacity of the environment?

3. List 3 examples of limiting factors.

Check Yourself!Check Yourself!

1. What kind of curve illustrates exponential growth? J-CURVE

2. What determines the carrying capacity of the environment? LIMITING FACTORS

3. List 3 examples of limiting factors.

1. What kind of curve illustrates exponential growth? J-CURVE

2. What determines the carrying capacity of the environment? LIMITING FACTORS

3. List 3 examples of limiting factors.

Check Yourself!Check Yourself!

1. What kind of curve illustrates exponential growth? J-CURVE

2. What determines the carrying capacity of the environment? LIMITING FACTORS

3. List 3 examples of limiting factors. FOOD, WATER, AND SPACE

1. What kind of curve illustrates exponential growth? J-CURVE

2. What determines the carrying capacity of the environment? LIMITING FACTORS

3. List 3 examples of limiting factors. FOOD, WATER, AND SPACE