1. Population Ecology 4
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 4.1 Studying Ecology
Ernst Haeckel defined ecology in 1866 as “the body of knowledge concerning the economy of nature—the total relations of the animal to both its inorganic and organic environment.”

3. Objectives
Describe the different levels of organization studied by ecologists
Explain the difference between biotic and abiotic factors
Discuss how an organism’s habitat relates to its survival

4. Levels of Ecological Organization
Lesson 4.1 Studying Ecology
Levels of Ecological Organization
Everything on Earth is connected, so how do ecologists study anything?
Ecology is the study of how organisms interact with each other and with their environments
Scientists study ecology at various levels of organization.

6. Levels of Ecological Organization
Individual
Ecology involves describing relationships between individual organisms and their environment.
Populations
Individual organisms are classified into species
Species is a group of individuals that interbreed and produce fertile offspring
Species have similar genetics
Members of a species that live in the same area at the same time make up a population.
Ecology involves how individuals within a population interact with one another.

7. Levels of Ecological Organization
Communities
All of the populations in a particular area.
Ecology involves interactions among species.
Ecosystems
Include all the livings things and their physical environments within a particular area
Living and nonliving things.
Ecology involves studying the living and nonliving components of a system together.

8. Levels of Ecological Organization
Biosphere
Includes all parts of Earth that host life, with all of its organisms and environments.
Ecology involves how matter and energy cycle through the biosphere and influence organisms worldwide.

9. Checkpoint
What is the difference between a species and a population? Between a population and a community?

10. Biotic and Abiotic Factors
Lesson 4.1 Studying Ecology
Biotic and Abiotic Factors
Biotic factors: Parts of an ecosystem that are living or used to be living
Ex: living tree, dead tree
Abiotic factors: Parts of an ecosystem that have never been living
Ex: oxygen, sunlight
Did You Know? Decaying organisms are biotic factors as long as their structure remains cellular.

11. Habitat The specific environment in which an organism lives
Lesson 4.1 Studying Ecology
Habitat
The specific environment in which an organism lives
Habitats consist of biotic and abiotic elements.
Habitats provide an organism with resources—anything an organism needs to survive and reproduce, including food, shelter, and mates.
The difference between habitat and ecosystem is that a habitat’s boundaries are defined by the population that lives there.
Habitats may be a subset of an ecosystem OR habitats may be a combination of ecosystems

12. Objectives Revisited
Describe the different levels of organization studied by ecologists
Explain the difference between biotic and abiotic factors
Discuss how an organism’s habitat relates to its survival

13. Lesson 4.2 Describing Populations
From 1900 to 2000, the white-tailed deer population of New York state grew from about 20,000 to more than 1 million. Densities of more than 100 deer per sq mi occur in some metropolitan areas.

14. Objectives Explain the usefulness of tracking population size.
Define population density.
Describe the three ways populations can be distributed.
Explain what age structure diagrams tell you about a population.

15. Lesson 4.2 Describing Populations
Population Size
The number of individuals in a population at a given time
Sudden and dramatic decreases in population size can indicate an unhealthy population headed toward extinction.
When population size increases or remains steady, it is often a sign of a healthy population.
Did You Know? The passenger pigeon was once North America’s most abundant bird. Hunting drove them to extinction in less than 100 years.

16. Determining Population Size
It is nearly impossible to count each individual in a population
Population is estimated using sampling techniques.
Count individuals in small sample area
Use that to estimate number of individuals in large overall area
Counting Laysan Albatross Nests

17. Checkpoint
When is sampling necessary?

18. Population Density Measure of how crowded a population is
Lesson 4.2 Describing Populations
Population Density
Measure of how crowded a population is
Larger organisms generally have lower population densities.
Low population density: More space, resources; finding mates can be difficult
High population density: Finding mates is easier; tends to be more competition; more infectious disease; more vulnerability to predators
Northern pintail ducks

19. Population Distribution
Lesson 4.2 Describing Populations
Population Distribution
How organisms are arranged within an area:
Random distribution: Organisms arranged in no particular pattern, resource are spread out
Uniform distribution: Organisms evenly spaced; individuals hold territories/compete for space
Clumped distribution: Organisms grouped near resources; most common distribution in nature

20. Population Distribution

21. Checkpoint
What is the difference between population density and distribution?

22. 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

23. 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.

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

25. 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.

26. Objectives Revisited
Explain the usefulness of tracking population size.
Define population density.
Describe the three ways populations can be distributed.
Explain what age structure diagrams tell you about a population.

27. Lesson 4.3 Population Growth
From 1800 to today, the human population has grown from about 1 billion to more than 6.8 billion—an exponential rate of increase.

28. Objectives
Describe the factors that influence a population’s growth rate.
Explain exponential growth and logistic growth.
Explain how limiting factors and biotic potential affect population growth.

29. 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.

30. 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

31. Checkpoint
Which type of survivorship curve describes populations whose mortality is highest at young ages?

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

33. 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.

34. 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
Did You Know? Immigration contributes more than 1 million people to the U.S. population per year.

35. 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

36. 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

37. Logistic Growth and Carrying Capacity

38. 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

39. Checkpoint
Why is severe weather considered a density-independent factor?

40. 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.

41. Objectives
Describe the factors that influence a population’s growth rate.
Explain exponential growth and logistic growth.
Explain how limiting factors and biotic potential affect population growth.