1. Changes in Ecosystems: Ecological Succession

2. What is Ecological Succession?
Natural, gradual changes in the types of species that live in an area
Can be primary or secondary
The gradual replacement of one plant community by another through natural processes over time

4. Primary Succession Begins in a place without any soil:
Sides of volcanoes
Landslides
Flooding
First, lichens that do not need soil to survive grow on rocks
Next, mosses grow to hold newly made soil
Known as PIONEER SPECIES

5. Pioneer Species Species that colonize barren habitats
Lichens, small plants with brief life cycles
Improve conditions for other species who then replace them

6. Pioneer Species
Low, growing moss plants trap moisture and prevent soil erosion
Lichens break down rock to form soil.

7. Primary Succession
Soil starts to form as lichens and the forces of weather and erosion help break down rocks into smaller pieces
When lichens die, they decompose, adding small amounts of organic matter to the rock to make soil

9. Primary Succession
Simple plants like mosses and ferns can grow in the new soil

10. Primary Succession
The simple plants die, adding more organic material (nutrients to the soil)
The soil layer thickens, and grasses, wildflowers, and other plants begin to take over

11. Primary Succession
These plants die, and they add more nutrients to the soil
Shrubs and trees can survive now

12. Primary Succession
Insects, small birds, and mammals have begun to move into the area
What was once bare rock, now supports a variety of life

13. Secondary Succession
Begins in a place that already has soil and was once the home of living organisms
Occurs faster and has different pioneer species than primary succession
Example: after forest fires

17. Climax Community
A stable group of plants and animals that is the end result of the succession process
Succession does not always move predictably toward a specific climax community; other stable communities may persist
Does not always mean big trees
Grasses in prairies
Cacti in deserts

18. Population Biology - Warmup
What is a population?
What are factors that affect the growth of a population?

19. Population Size Factors that affect: Natality (birth rate)
Mortality/Fatality
Immigration
Emigration

20. Population Growth Curves
Explain what is happening to the populations below:

21. Carrying Capacity
Carrying capacity - the number of people, other living organisms, or crops that a region can support without environmental degradation.
Represented by the variable k = carrying capacity

22. Population Growth Curves
Explain what is happening to the populations below:

23. Biotic Potential = Reproductive Potential
Rate at which a population could grow if it had unlimited resources
If a population reached its biotic potential it would have exponential growth

25. The “J” Curve

26. The “S” Curve
This graph shows a typical population growth curve. Under ideal conditions a population would have a growth with a slow start, then a very fast rate of increase and finally the growth slows down and stops.

27. Logistic Growth or “S” curve
Carrying capacity or “steady state” Not a perfectly straight line
Carrying capacity
Exponential – rapid growth
Availability of food and space limit growth
Use example of number of students in this classroom
Initial slow growth

28. Environmental Limits on populations
Density-dependent factors
% of population affected increases as density increases
Examples:
Disease
Food
Parasitism
Predation
Competition
Density-independent factors
Effect does not change with population size density
Temperature
Storms
Floods
Drought
Habitat Disruption
Results in “Boom or Bust” Growth curve

29. Boom or Bust Growth Curve
Population
July December July December
Fluctuates around “line K”
Density independent or dependent?

30. Density Dependent
Here is a dramatic example of how competition among members of one species for a finite resource — in this case, food — caused a sharp drop in population.
The graph shows a population crash; in this case of reindeer on two islands in the Bering Sea.

31. Density Independent
This graph shows the decline in the population of one of Darwin's finches on Daphne Major, a tiny (100-acre) member of the Galapagos Islands. The decline (from 1400 to 200 individuals) occurred because of a severe drought that reduced the quantity of seeds on which this species feeds. The drought ended in 1978, but even with ample food once again available the finch population recovered only slowly.

32. Organism Interactions Limit Populations
Predation
Competition
Both types
Parasitism
Crowding/stress

33. Predator - Prey Growth Curve
Fluctuates around “line K” (carrying capacity)

34. The Human Population

35. Demography Vocabulary
Age Structure
Immigration
Emigration
Birth/Death Rate

36. Age Structure Pyramids
These population pyramids show the baby-boom generation in 1970 and again in 1985 (green ovals).
Profound changes (e.g. enrollments in schools and colleges) have occurred — and continue to occur — in U.S. society as this bulge passes into ever-older age brackets.

37. Biodiversity & Conservation
Importance to nature
Importance to people
Oxygen
Diet
Medicines

38. Loss of Diversity Threatened Species Endangered Species
Extinction of Species

39. Threats to Biodiversity
Habitat Loss
Habitat Fragmentation
Biotic Issues
Abiotic Issues
Habitat Degradation
Air Pollution
Water Pollution
Land Pollution

40. Exotic Species Example: Page 124
Non-native organisms that “move-in” to a particular area
There can be a lack of competitors = exponential growth
Can take over the niches of native species

41. Conservation Sustainable use:
Use what you need, but don’t damage the ecosystem
Is this a good example of sustainable use?

42. Conservation
Habitat Corridors

43. Conservation Reintroduction Programs Captivity Breeding Example:
The Ginkgo Tree would probably be extinct if it were not for Chinese monks keeping it in captivity around temples

44. Biological Controls
A living organism used to control the population of another undesirable organism

45. Biological Controls – Examples
Advantages
Not toxic to environment
Pests won’t become immune
Won’t get out of control
Disadvantages
Doesn’t completely control pest population
Takes longer