Environmental Science

1. EnvironmentalScience Chapter 4

2. Section 1 • Objectives: • 1. Describe the different levels of organization studied by ecologists • 2. Explain the difference between biotic and abiotic factors. • 3. Discuss how an organism’s habitat relates to its survial.

3. Section 1 • The Central Case • How do changes in population size relate to environmental conditions?

4. Section 1 • Scientists study life at many levels, from individual organisms to the entire biosphere. • Lets begin by taking a look at those different levels……………

5. Section 1 • Ecology (figure 1) – • Ecologist

6. Section 1 • Levels of ecological organization • 1. Individuals What ecologists study: 2. Populations What ecologists study:

7. Section 1 • Species • 3. Communities What ecologists study:

8. Section 1 • 4. Ecosystems – What ecologists study • 5. The Biosphere

9. Section 1 • Ecosystems include both biotic and abioticfactors. • Biotic factors • Abiotic factors

10. Section 1 • The specific environment in which an organism lives is its ____________________. It consists of both ________________ and ____________________ factors. • Anything an organism needs, including nutrition, shelter, breeding sites, and mates is a _________________________.

11. Section 2 • Objectives: • 1. Explain the usefulness of tracking population size. • 2. Describe population density. • 3. Describe the 3 ways populations can be distributed. • 4. Explain what age structure diagrams tell you about a population.

12. Section 2 • The overall health of a population can often be monitored by tracking how its size changes, population density changes, and distribution changes. • The number of individual organisms present in a given population at a given time is called the _______________________.

13. Section 2 • If a population size increases or remains the same it is a sign of a _______________________________________. • If a population size decreases it can lead to __________________________________. • The Passenger Pigeon

14. Section 2 • Determining population size • Do you think Alexander Wilson actually counted 2 billion passenger pigeons??? • NO!!!! • He took a SAMPLE

15. Section 2 • They take a reasonable area, count the number of individuals, and estimate the number of individuals of a much larger area. • Scientists also look for EVIDENCE that the organisms exist. • Animal droppings or tracks

16. Section 2 • The number of individuals within a population per unit area describes the ____________________ ___________________. • High population densities Pros: Cons:

17. Section 2 • The number of individuals within a population per unit area describes the ____________________ ___________________. • High population densities Pros: Cons:

18. Section 2 • Low population densities • Pros: • Cons:

19. Section 2 • How the organisms are arranged within an area is called __________________ ___________________________. • Populations can be arranged ________________, ___________________, or in ____________________.

20. Section 2 • Random distribution: • Uniform distribution: • Clumped distribution:

21. Section 2 • Age structure and sex ratios • This describes the relative numbers of organisms of each age within a population: ___________ ________________. • ______ ____________________ ____________ are visual tools to show the age structure of populations.

22. Section 2 • Pre-reproductive organisms: • Post-reproductive organisms: • The proportion of males to females in a population describes _____________ __________.

23. Section 3 • Objectives: • 1. Describe the factors that influence a population’s growth rate. • 2. Explain exponential growth and logistic growth. • Explain how limiting factors and biotic potential affect population growth.

24. Section 3 • A population’s growth rate is determined by births, deaths, immigration, and emigration. • The rate at which individuals are born is called _________________________. • The rate at which individuals die is called ___________________________.

25. Section 3 • To show how the likelihood of death varies with age, population ecologists use graphs called _______________ ___________. • There are 3 types of survivorship curves: • I: • II: • III:

26. Section 3 • Population size can also be affected by people moving in or out of a population. • ____________ is the arrival of individuals from outside a given area. • _____________ is the departure of individuals from a given area. • _________________ is the seasonal movement into and out of an area.

27. Section 3 • Calculating Population Growth • (individuals added)-(individuals subtracted) = population growth Or (birthrate + immigration rate)-(death rate + emigration rate) = population growth Example:

28. Section 3 • How populations grow • Growth rates change depending on resources available to the organisms in the population • 2 ways for populations to grow: • 1. • 2. • 1. _______________________ occurs when a population increases by a fixed percentage each year • Produces a J-shaped curve on a graph

29. Section 3 • 1. _______________________ occurs when a population increases by a fixed percentage each year • Produces a J-shaped curve on a graph • Exponential growth occurs when: • 1. • 2. • Examples: • 1. Mold growing on bread • 2. bacteria growing on dead organisms

30. Section 3 • 2. ___________________ describes how a population’s initial exponential increase is slowed and finally stopped by limiting factors. • Produces an S-curve on a graph • ____________ are characteristics of the environment that limit population. • _____________ is the largest population size a given environment can sustainably support.

31. Section 3 • Limiting Factors and Biotic Potential • _______________________ is a limiting factor whose influence changes with population density • Ex: competition, predation, disease • __________________ is a limiting factor whose influence is not affected by population density • Ex: catastrophic events

32. Section 3 • _________________ is the growth rate of a population under ideal conditions • Factors that affect the biotic potential: • 1. • 2.