1. Carrying Capacity, Food Chains, Food Webs, and the Transfer of Energy
Ecology Notes
Carrying Capacity, Food Chains, Food Webs, and the Transfer of Energy

2. Limits to Population Growth
Carrying Capacity
Maximum population size existing in an ecosystem at a given time without damaging ecosystem

3. Carrying Capacity
Key Point: We can read a carrying capacity graph to predict changes in population size
Time
Population size
Graph line = Population size at a specific time
Dotted line = Carrying Capacity
A = x-axis = time
C = y-axis = population size
B = graph shows population size at any given time
D = carrying capacity

4. Carrying Capacity
Time
Population size
Remember from math class, exponential increase = constantly doubling. (Makes a curved line on a graph.)
Analogy: each person at the party invites a new friend. Each one of them invites another new friend. Etc.
When a population is BELOW its carrying capacity, it will INCREASE in size
Birth rate exceeds death rates

5. Carrying Capacity
Time
Population size
Analogy: We run out of food at the party, and people start to leave.
Remember over the last few days, when one population in a food web died, so another population that ate it decreased in size? That’s because the carrying capacity decreased!
But if it increases too much and rises ABOVE its carrying capacity, it will DECREASE in size
Death rate exceeds birth rate

6. Carrying Capacity
Time
Population size
Analogy: Once there’s enough food again, more people will come. But we’ll probably be a bit more cautious, and not invite people as quickly. So if we go over carrying capacity, it won’t be by as much.
This happens over and over… but the increases and decreases get smaller and smaller…

7.
Has Earth reached our carrying capacity?

8. Limits to Population Growth
Limiting factor
Anything preventing growth of a population
Examples:
Space
Food
Climate and Weather
Disease
Human Activity

9. Autotrophs
A group of organisms that can use the energy in sunlight to convert water and carbon dioxide into Glucose (food)
Without autotrophs, there would be no life on this planet
Ex. Plants and Algae

10. Heterotrophs Organisms that do not make their own food
Another term for Heterotroph is consumer
Ex. Rabbits, Deer, Mushrooms

11. Heterotrophs Consumers
1. Scavengers/Detritivores – feed on the tissue of dead organisms (both plants and animals)
Ex. – Vultures, Crows, and Shrimp

12. Heterotrophs Consumers 2. Herbivores – eat ONLY plants
Ex. – Cows, Elephants, Giraffes

13. Heterotrophs Consumers 3. Carnivores – eat ONLY meat
Ex. – Lions, Tigers, Sharks

14. Heterotrophs Consumers 4. Omnivores – eat BOTH plants and animals
Ex. – Bears and Humans

15. Heterotrophs Consumers
5. Decomposers – absorb any dead material and break it down into simple nutrients or fertilizers
Ex. – Bacteria and Mushrooms

16. Transfer of Energy
When a zebra eats the grass, it does not obtain all of the energy the grass has
When a lion eats a zebra, it does not get all of the energy from the zebra (much of it is lost as heat)

17. Transfer of Energy
The two (2) previous examples of energy transfer show that no organism EVER receives all of the energy from the organism they just ate
Only 10% of the energy from one trophic level is transferred to the next – this is called the 10% law

18. Trophic Levels
Energy moves from one organisms to another when it is eaten
Each step in this transfer of energy is know as a trophic level
The main trophic levels are producers, consumers, and decomposers

19. Food Chains
The energy flow from one trophic level to the other is know as a food chain
It involves one organism at each trophic level
Primary Consumers – eat autotrophs (producers)
Secondary Consumers – eat the primary consumers
Tertiary Consumers – eat the secondary consumers
Decomposers – bacteria and fungi that break down dead organisms and recycle the material back into the environment

20. Food Chain

21. Food Web Most organisms eat more than JUST one organism
When more organisms are involved it is known as a FOOD WEB
Food webs are more complex and involve lots of organisms

22. Food Web

23. Food Web
Notice that the direction the arrow points  in the direction of the energy transfer, NOT “what ate what”

24. Food Web

25. Biomass
The total mass of the organic matter at each trophic level is called biomass
Biomass is just another term for potential energy – energy that is to be eaten and used.
The transfer of energy from one level to another is very inefficient (10% Law)

26. Biomass

27. Ecological Pyramid
An ecological pyramid shows the relationship between consumers and producers at different trophic levels in an ecosystem
Shows the relative amounts of energy or matter contained at each trophic level
The Pyramid shows which level has the most energy and the highest number of organisms

28. Ecological Pyramid

29. Ecological Pyramid

30. Ecological Pyramid Which level has the most energy?
Which level has the most organisms?
Which level has the least organisms?
Which level has the least energy?

31. Ecological Succession
A change in the community in which new populations of organisms gradually replace existing ones
1. Primary Succession – occurs in an area where there is no existing communities and for some reason (s) a new community of organisms move into the area

32. Ecological Succession
A change in the community in which new populations of organisms gradually replace existing ones
2. Secondary Succession – occurs in an area where an existing community is partially damaged

33. Ecological Succession
A change in the community in which new populations of organisms gradually replace existing ones
3. Climax Community – a community that is stable and has a great diversity of organisms

34. Ecological Succession