Page

**3**

In animals, parental care of smaller broods may facilitate survival of offspring.

Some plants, like the dandelion, produce a large number of small seeds, ensuring that at least some of them will grow and eventually reproduce.

Other types of plants, like the coconut tree, produce a moderate number of large seeds that provide a large store of energy that will help seedlings become established.

Slide 16

Variation in the size of seed crops in plants

(a) Dandelion

(b) Coconut palm

Slide 17

It is useful to study population growth in an idealized situation.

Idealized situations help us understand the capacity of species to increase and the conditions that may facilitate this growth.

Slide 18

Zero population growth occurs when the birth rate equals the death rate.

Most ecologists use differential calculus to express population growth as growth rate at a particular instant in time:

where N = population size, t = time, and r = per capita rate of increase = birth – death

Slide 19

Exponential population growth is population increase under idealized conditions.

Under these conditions, the rate of reproduction is at its maximum, called the intrinsic rate of increase.

Exponential population growth results in a J-shaped curve

Exponential Growth is not sustainable.

Slide 20

Exponential Growth Model

Number of generations

0

5

10

15

0

500

1,000

1,500

2,000

1.0N

=

dN

dt

0.5N

=

dN

dt

Population size (N)

Slide 21

The J-shaped curve of exponential growth characterizes some rebounding populations

8,000

6,000

4,000

2,000

0

1920

1940

1960

1980

Year

Elephant population

1900

Slide 22

Exponential growth cannot be sustained for long in any population. A more realistic population model limits growth by incorporating carrying capacity.

Carrying capacity (K) is the maximum population size the environment can support.

In the logistic population growth model, the rate of increase declines as carrying capacity is reached.

- Population ecology
- Dynamic biological processes influence population density, dispersion, and demographics
- Demographics
- Life history traits are products of natural selection
- Evolution and Life History Diversity
- “Trade-offs” and Life Histories
- The exponential model describes population growth in an idealized, unlimited environment
- Exponential Growth
- The logistic model describes how a population grows more slowly as it nears its carrying capacity
- The Logistic Model and Real Populations
- The Logistic Model and Life Histories
- Many factors that regulate population growth are density dependent
- Population Change and Population Density
- Density-Dependent Population Regulation
- Population Dynamics
- The human population is no longer growing exponentially but is still increasing rapidly

- Static and Kinetic Friction
- Sensory and Motor Mechanisms
- Newton's laws of motion
- Simulation at NASA for the Space Radiation Effort
- Health Physics
- Radiation
- Solar Thermal Energy

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