1. Ecology

2. Population Characteristics
Population Ecology: Population Characteristics
Population Characteristics
Population Density:
The number of organisms per unit area
Spatial Distribution:
Dispersion: The pattern of spacing a population within an area
3 main types of dispersion
Clumped
Uniform
Random
The primary cause of dispersion is resource availability

3. Population Limiting Factors
Population Ecology: Population Characteristics
Population Limiting Factors
Population growth rate
How fast a given population grows
Factors that influence this are:
Natality (birth rate)
Mortality (death rate)
Emigration (the number of individuals moving away from a population)
Immigration (the number of individuals moving into a population)

4. Population Limiting Factors
Population Ecology: Density-independent factors
Population Limiting Factors
Density-independent factors
Factors that limit population size, regardless of population density.
These are usually abiotic factors
They include natural phenomena, such as weather events
Drought, flooding, extreme heat or cold, tornadoes, hurricanes, fires, etc

5. Population Limiting Factors
Population Ecology: 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
Usually biotic factors
These include
Predation
Disease
Parasites
Competition

6. Understanding Exponentials
Population Ecology: Population Growth Rate
Understanding Exponentials
Put your pens down for a minute & think about this:
An employer offers you two equal jobs for one hour each day for fourteen days.
The first pays $10 an hour.
The second pays only 1 cent a day, but the rate doubles each day.
Which job will you accept? 6

7. Understanding Exponentials
Population Ecology: Population Growth Rate
Understanding Exponentials
Now, how much would your employer owe you if you stayed at this job for another 2 weeks?
Job 2 lags for a long time before exponential growth kicks in!
What would happen if this type of growth took place within a population?

8. Population Limiting Factor
Population Ecology: Population Growth Rate
Population Limiting Factor
Population growth models
Exponential growth model
Also called geometric growth or J-shaped growth.
First growth phase is slow and called the lag phase
Second growth phase is rapid and called the exponential growth phase
Bacteria can grow at this rate, so why aren’t we up to our ears in bacterial cells?

9. Population Limiting Factors
Population Ecology: Population Growth Rate
Population Limiting Factors
Population growth models
Limits to exponential growth
Population Density (the number of individuals per unit of land area or water volume) increases as well
Competition follows as nutrients and resources are used up
The limit to population size that a particular environment can support is called carrying capacity (k)

10. What population do you think this is?
Population Ecology: Population Growth Rate
What population do you think this is?

11. So, what do you think is going to happen to the human population?
We will probably reach our carrying capacity.
Our growth rate will start to look like most organisms, which is the Logistic Growth Model
Carrying Capacity (k)
What letter does this curve kind of look like?

12. Population Limiting Factors
Population Ecology: Population Growth Models
Population Limiting Factors
Population growth models
Logistic Growth Model
Often called the S-shaped growth curve
Occurs when a population’s growth slows or stops following exponential growth.
Growth stops at the population’s carrying capacity
Populations stop increasing when:
Birth rate is less than death rate (Birth rate < Death rate)
Emigration exceeds Immigration (Emigration > Immigration)

13. Population Limiting Factors
Population Ecology: Population Growth Models
Population Limiting Factors
Population growth models
Logistic Growth Model
The S-curve is not as pretty as the image looks
Carrying capacity can be raised or lowered. How?
Example 1: Artificial fertilizers have raised k
Example 2: Decreased habitat can lower k
Populations don’t reach k as smoothly as in the logistic graph.
Boom-and-Bust Cycles
Predator-Prey Cycles

14. Community Ecology: Communities
Review:
A community is a group of interacting populations that occupy the same area at the same time.

15. Communities Limiting Factors
Community Ecology: Communities
Communities
Limiting Factors
Any abiotic or biotic factor that restricts the numbers, reproduction, or distribution of organisms.

16. Communities Range of Tolerance
Community Ecology: Communities
Communities
Range of Tolerance
The limits within which an organism can exist.

17. Ecological Succession
Community Ecology: Ecological Succession
Ecological Succession
Ecological Succession
The change in an ecosystem that happens when one community replaces another as a result of changing biotic and abiotic factors

18. Ecological Succession
Community Ecology: Ecological Succession
Ecological Succession
Ecological Succession
Consists of 2 types:
Primary Succession
Secondary Succession

19. Ecological Succession
Community Ecology: Ecological Succession
Ecological Succession
Ecological Succession: Primary
The establishment of a community in an area of exposed rock that does not have topsoil is called Primary Succession.
It occurs very slowly at first

20. Ecological Succession
Community Ecology: Ecological Succession
Ecological Succession
Ecological Succession: Primary
The first organisms to arrive are usually lichens or mosses, which are called pioneer species.
They secrete acids that can break down rock
Their dead, decaying organic materials, along with bits of sediment from the rock make up soil.

21. Ecological Succession
Community Ecology: Ecological Succession: Primary Succession
Ecological Succession
Ecological Succession: Primary
Small weedy plants and other organisms become established.
As these organisms die, additional soil is created

22. Ecological Succession
Community Ecology: Ecological Succession: Primary Succession
Ecological Succession
Ecological Succession: Primary
Seeds brought in by animals, water and wind begin to grow in the soil.
Eventually enough soil is present for shrubs and trees to grow.

23. Ecological Succession
Community Ecology: Ecological Succession: Primary Succession
Ecological Succession
Ecological Succession: Primary
The stable, mature community that eventually develops from bare rock is called a climax
community.

24. Ecological Succession
Community Ecology: Ecological Succession: Primary Succession
Ecological Succession
Ecological Succession: Secondary
Disturbances (fire, flood, windstorms) can disrupt a community.
After a disturbance, new species of plants and animals might occupy the habitat.

25. Ecological Succession
Community Ecology: Ecological Succession: Secondary Succession
Ecological Succession
Ecological Succession: Secondary
Pioneer species in secondary succession are usually plants that begin to grow in the disturbed area.
This is much faster than primary succession

26. Ecological Succession
Community Ecology: Ecological Succession
Ecological Succession
Ecological Succession: End point?
Cannot be predicted
Different rates of growth & human involvement make it impossible to know if a true climax community has been reached.

27. Biodiversity What is Biodiversity?
Biodiversity and Conservation: What is biodiversity?
Biodiversity
What is Biodiversity?
The variety of life in an area that is determined by the number of different species in that area.
There are 2 main types:
Genetic Diversity
Species Diversity

28. Biodiversity and Conservation: Why is biodiversity important?
Penicillin: Derived from bread mold
The teosinte plant contains genes that are resistant to several viral diseases that affect domesticated corn plants. These genes have been used to produce viral-resistant domestic corn varieties.
Teosinte: A distant relative of corn
Domestic corn plant
Madagascar Periwinkle: Used to treat childhood forms of leukemia

29. Biodiversity and Conservation: Extinctions
Extinction Rates
The gradual process of becoming extinct is known as background extinction.
Mass extinctions: When a large percentage of all living species become extinct in a relatively short period of time.
250 MYA: Over 90% of species died

30. Estimated number of Extinctions since 1600
Biodiversity and Conservation: Extinctions
Estimated number of Extinctions since 1600
Group
Main-land
Island
Ocean
Total
Approximate Number of Species
Percent of Group Extinct
Mammals 30 51 4 85
4000
2.1
Birds 21 92
113
9000
1.3
Reptiles 1 20
6300
0.3
Amphibians 2
4200
0.05
Fish 22 23
19,100
0.1
Invertebrates 49 48 98
1,000,000+
0.01
Flowering Plants
245
139
384
250,000
0.2
Since the mid-1970s there has been an alarming decrease of amphibian populations, and many are on the verge of extinction.

31. Five Most Recent Mass Extinctions
Biodiversity and Conservation: Extinctions
Five Most Recent Mass Extinctions
Cretaceous Period (65 MYA)
Triassic Period (200 MYA)
Permian Period (250 MYA)
Devonian Period (360 MYA)
Ordovician Period (444 MYA)