deer population dynamics

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Why doesn’t the population ever go

above 18?

What is happening to this population?

The number of organisms of one

species that an environment can support

indefinitely.

Carrying Capacity

18 is the Carrying Capacity for our population.

deer population dynamics

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Why does population increase?

Population Growth

Unlimited resources and reproduction lead to population growth (G)

Growth = Births – Deaths

(G = B – D)

• An increase in the number of individuals in a population

When births exceed deaths you see population growth.

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J-Shaped Curve

Population Growth

Exponential Growth

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J-Shaped Curve

• Exponential growth means that as a population gets larger, it also grows at a faster rate.

Reproduction Patterns:Rapid life-history patterns

• Rapid life-history patterns are common among organisms from changeable or unpredictable environments.

20 MINUTES!

• Large species that live in more stable environments usually have slow life-history patterns.

Reproduction Patterns: Slow life-history patterns

• Reproduce and mature slowly, and are long-lived.

• Maintain population sizes at or near carrying capacity.

22 MONTHS!

Growth Limitations

• Resources

• Disease

• Organism interaction

• Habitat Size/Crowding

• Weather

When a population overshoots the

carrying capacity, then limiting

factors may come into effect.

population growth over 20 years

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Deaths begin to exceed births and the population falls below carrying capacity

S - Curve

Density-dependent

and

Density-independent

Two types of limiting factors:

Population density describes the number of individuals in a given area.

Population Density

• Let’s say our classroom is 600 sq. ft.

In 3rd hour and fifth hour, there are 25 students in the class.

The population density for 3rd and 5fth hour is 25 students/600 ft² or .04 students/ft².

In 6th hour, there are only 19 students in the class. Is the population density higher or lower?

Density - Dependent

• Density-dependent factors include disease, competition, predators, parasites, and food.

• Disease, for example, can spread more quickly in a population with members that live close together.

Its flu season, and lots of sick students are coming to school. They are coughing, sneezing, and touching

everything. Ten percent of Ms. Sonleitner’s students have the flu, but are so dedicated they come to class anyway. If Ms. Sonleitner wipes down every table

before every class, which class will be most affected by the flu?

3rd and 5th hours, because they have the greatest population density. A larger number of students will be infected and have opportunity to infect a larger number of healthy students.

Density - Independent

• Density-independent factors can affect all populations, regardless of their density.

• Most density-independent factors are abiotic factors, such as temperature, storms, floods, drought, and major habitat disruption

Six new students were added to sixth hour. The population densities of all the classes is

now the same.The school is sponsoring an event that allows students to miss 3rd, 5th, and 6th hours. Which

classes will be most effected?

• All equally effected! The event will disrupt class regardless of size – everyone will have the opportunity to go.

Organism Interactions

• Population sizes are controlled by various interactions among organisms that share a community.

• Predation and competition are two interactions that control populations.

PredationPopulations of predators and their prey experience cycles or changes in their

numbers over periods of time.

Lynx and Hare pelts sold to the Hudson’s Bay Company

Competition

• When only a few individuals compete for resources, no problem arises.

• When a population increases to the point at which demand for resources exceeds the supply, the population size decreases.

• Is Density - Dependent

Crowding• As populations increase in size in environments

that cannot support increased numbers, individual animals can exhibit a variety of stress symptoms.

• These include aggression, decrease in parental care, decreased fertility, and decreased resistance to disease.

• They become limiting factors for growth and keep populations below carrying capacity.

Population of New Orleans, La 1970-2006

-50000

50000

150000

250000

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650000

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1. What are the independent and dependent variables?

2. What is the population trend?

3. Why did this happen? Is this density-dependent or independent?

Global population 1900 - 2046

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recorded population

projected population

4. What type of growth is this?

5. When does growth increase? What might have happened to cause this?