1. Population Ecology- Continued4
CHAPTER
Placeholder opening page, but maybe we can duplicate the look of the SE chapter opener page by using the same fonts and colors (and maybe that Ch 14 icon?)

2. Lesson 4.2 Describing Populations
Age Structure
Age structure describe the relative number of organisms of each age group within population
Can be used to predict future population growth of a population
Individuals capable of having offspring make up the reproductive group
Young individuals who have not yet reached the age where they can reproduce are called pre-reproductive
Older individuals past the age of having offspring are called post-reproductive

3. Age Structure
Population with even age distribution will likely remain stable (births = deaths).
Population made up of mostly post-reproductive individuals will likely decline over time.
Population made up of mostly pre-reproductive individuals will likely increase over time.

4. Age Structure Diagram
Age 
How will each population change over time?

5. Sex Ratios Proportion of males to females
Lesson 4.2 Describing Populations
Sex Ratios
Proportion of males to females
Age structure diagrams give information about sex ratios.
For a monogamous species, the ideal sex ratio is 50:50.

6. Lesson 4.3 Population Growth
Birth and Death Rates
A population’s relative birth and death rates (natality and mortality) affect how it grows.
When birthrate is greater than death rate, population size increases.
When death rate is greater than birth rate, population size decreases.
Survivorship curves show how the likelihood of death varies with age.

7. Birth and Death Rates Survivorship curves:
Graphs that show how the likelihood of death varies with age
Type I curve has higher mortality at older ages
Type II curve has equal mortality rates at all ages
Type III curve has higher mortality rate at younger ages

8. Survivorship Curves

9. Birth and Death Rates Age Structure and Population Growth:
For a population following a type I survivorship curve (higher mortality at older ages):
If population is made up of more young people, there is likely to be more births than deaths
If population is made up of more old people, there is likely to be more deaths than births.

10. Immigration and Emigration
Lesson 4.3 Population Growth
Immigration and Emigration
In addition to births and deaths, population growth is affected by immigration and emigration—individuals moving into and out of a population.
Migration, seasonal movement into and out of an area, can temporarily affect population size.

11. Calculating Population Growth
Lesson 4.3 Population Growth
Calculating Population Growth
Determined by the following equation: (birthrate + immigration rate) – (death rate + emigration rate)
Growing populations have a positive growth rate; shrinking populations have a negative growth rate.
Usually expressed in terms of individuals per 1000

12. Lesson 4.3 Population Growth
Exponential Growth
Population increases by a fixed percentage every year.
Normally occurs only when small populations are introduced to an area with ideal environmental conditions
Rarely lasts long
Ex: Mold growing on bread

13. Logistic Growth and Limiting Factors
Lesson 4.3 Population Growth
Logistic Growth and Limiting Factors
Growth almost always slows and stops due to limiting factors.
Limiting factors: Environmental characteristics slow population growth and determine carrying capacity (largest population size a given environment can support).
Density-dependent: Influence changes with population density; examples are competition for resources, predation, disease
Density-independent: Influence does not change with population density; Examples are floods, fires, landslides

14. Logistic Growth and Carrying Capacity

15. Population Growth In Nature
Fluctuating:
Cycle indefinitely above and below carrying capacity
Rise and Crash
Rise very quickly, overshoot the carrying capacity, and then crash

16. Lesson 4.3 Population Growth
Biotic Potential
An organism’s maximum ability to produce offspring in ideal conditions
Many factors influence biotic potential, including gestation time (time to “be born”) and generation time (span from time of organism’s birth until time it has its own offspring).
Organisms with high biotic potential can recover more quickly from population declines than organisms with low biotic potential.