1. Human Ecology Lecture 1

2. Ecosystems

3. What is an Ecosystem?

4. An ecosystem has both biotic (living) and abiotic (non-living) components.

5. A community is made up of: populations of organisms interacting and inhabiting the same area at the same time. Ecosystem is a community plus it’s physical environment

6. Ecological Niches: roles filled by each member in an ecosystem.

7. Producers: organisms that carry out photosynthesis.

8. Consumers: heterotrophs that consume food already formed.

9. primary consumers : herbivores, plant-eating organisms

10. Secondary consumers: carnivores which eat primary consumers.

11. Omnivores: organisms that eat both plants and animals.

12. Decomposers: organisms which consume dead or decaying matter.

13. Movement of energy in an ecosystem
Energy cannot be created or destroyed, it is lost as heat when energy is transformed from one form to another form.
food chains and Food webs show who eats whom
Grazing food chain- producer > primary consumer > etc. In a community.
Detritus food chain - this is based on decomposers

15. Decreasing energy available at each trophic level; 90% of the energy consumed at each level is lost as heat leaving only 10% of it to be incorporated by the next trophic level.

16. Energy from sunlight provides energy needed in an ecosystem.
Producers capture energy
Energy flows in one direction

17. food webs- all the interconnecting food chains in an ecosystem

18. Ecosystems continue because they cycle nutrients, use resources, and keep their populations stable.

19. Cycles in the Ecosystem

20. Nutrients cycle through communities.

21. Water cycle

22. Carbon cycle

23. Phosphorus cycle

24. Nitrogen cycle

25. Succession The sequential change in a dominant species
in an area until a climax community is reached.

26. Primary Succession Occurs when there has never been soil and lichens and mosses contribute to soil formation.

27. Secondary succession Occurs in areas with soil, such as, abandoned agricultural fields, it begins with herbaceous plants >shrubs>trees>until the climax community is reached.

28. As succession proceeds, the variety of species increases, the community becomes more able to recycle nutrients and use energy efficiently

29. Climax communities have difficulty recovering from disturbance
Climax communities have difficulty recovering from disturbance. The more diverse the community, the more fragile and sensitive it becomes.

30. Humans harm ecosystems by:
Destruction of habitat- agricultural practice
Pollution
Over hunting
Introducing alien species

31. Changes in the ecosystem
Population fluctuations caused by:
Limiting factors: competition, predation etc.
Disturbances in the food chain- over hunting, pesticide use, biomagnification.

32. Humans impact on Ecosystems Mature natural ecosystems are stable over time. Human activities alter these ecosystems.

33. Pollution Fertilizers Pesticides Herbicides Over irrigating Excessive fuel consumption

34. Problems with cities Dependence on farms for food resources Taking up more land Challenges of cities for housing Not conserving and reusing resources generation of huge amounts of pollution Population increases

35. Biological Magnification (Biomagnification)

36. Ecological Relationships
Predation – Predator/ Prey +/-
Parasitism – Parasite/ Host +/-
Mutualism – benefits both +/+
Commensalism - one benefits other unaffected +/0
Competition -/-