1. Population Dynamics
Chapter 4 Section 1

2. Main Idea
Populations of species are described density, spatial distribution, and growth rate.

3. How does carrying capacity affect reproductive rates?
Thinking Questions
What are the characteristics of populations and how they are distributed?
What are the differences between density- independent and density-dependent limiting factors?
What are the similarities between the different models used to quantify the growth of a population?
How does carrying capacity affect reproductive rates?

4. Populations are groups of the same species in the same area.
Population Characteristics
Populations are groups of the same species in the same area.
Characteristics of populations that are used to classify them include density, distribution, and growth rate

5. Population Characteristics
Population density
The number of organisms per unit area is the population density.

6. Spatial distribution
Dispersion is the spacing pattern of a population.
Can be uniform, clumped groups, or random
Uniform- bears, bald eagles, corn
Clumped- bison, lions
Random- deer, dandelions
Pattern primarily driven by resources such as food
Population Characteristics

7. Population ranges No population occupies all habitats in the biosphere
Population Characteristics
Population ranges
No population occupies all habitats in the biosphere
A species’ range is its distribution across the environment.
Hawaiian Honeycreeper has limited population range while the Peregrine Falcon has vast population range
A species might not be able to expand its population range because it cannot survive the abiotic conditions found in the expanded region.

8. Limiting factors are either density-independent or density-dependent.
Population- Limiting Factors
Limiting factors are biotic or abiotic forces that keep populations from increasing indefinitely.
Limiting factors are either density-independent or density-dependent.

9. Density-independent factors
Population- Limiting Factors
Density-independent factors
Any factor in the environment that does not depend on the number of members in a population per unit area is a density-independent factor.
Usually abiotic, and include:
Weather events
Fire
Human alterations of the landscape-land development, dams, fishing practices
Air, land, and water pollution

10. Density-dependent factors
Population- Limiting Factors
Density-dependent factors
Any factor in the environment that depends on the number of members in a population per unit area is a density-dependent factor.
Often biotic, and include:
Predation
Disease ~When population density is high, diseases can spread more quickly
Competition ~Increases as density increases
Parasites

11. Population growth rate
Population- Limiting Factors
Population growth rate
The population growth rate (PGR) explains how fast a given population grows.
Natality: birthrate of a population in a given year (number of individuals born)
Mortality: the number of individuals who die in a given year
Emigration: number of individuals moving away from a population
Immigration: number of individuals moving into a population

12. Population growth rate
Population- Limiting Factors
Population growth rate
Exponential growth model: J-shaped growth curve
Occurs when growth rate is proportional to population size
Begins with a lag phase, or slow growth rate phase
All populations grow exponentially until they encounter a limiting factor.

13. Population growth rate
Population- Limiting Factors
Population growth rate
Logistic growth model: S-shaped growth curve
Occurs when a population’s growth slows or stops following exponential growth, at the population’s carrying capacity
A population stops increasing when the number of births < number of deaths, or when emigration > immigration.

14. Population growth rate
Population- Limiting Factors
Population growth rate
Carrying capacity
Carrying capacity is the maximum number of individuals in a species that an environment can support.

15. Reproductive patterns
Population- Limiting Factors
Reproductive patterns
Species vary in the number of births per reproduction cycle, age that reproduction begins, and in the life span.
Plants and animals are placed into groups based on their reproductive factors.
r-strategists or k-strategist

16. Reproductive patterns
Population- Limiting Factors
Reproductive patterns
r-strategy
k-strategy
Rate strategy
Carrying-capacity strategy
Adapted for fluctuating environment
Adapted to stable environment
Generally small
Generally large
Short life span
Long life span
Many offspring
Few offspring
Expend little energy to raise young
Invest more energy into nurturing young

17. How does carrying capacity affect reproductive rates?
Thinking Questions
What are the characteristics of populations and how they are distributed?
What are the differences between density- independent and density-dependent limiting factors?
What are the similarities between the different models used to quantify the growth of a population?
How does carrying capacity affect reproductive rates?