Chapter 16: Ecosystems

1. Chapter 16: Ecosystems Ecology Unit

2. What is ecology? • Ecology is the study of interactions- these interactions can be among organisms or between organisms and their environment. • A community is a collection of populations living in the same habitat. Communities are comprised of multiple species. • An ecosystem is a combination of the community and the environment around it.- the organisms comprise the community (biotic factors)- the soil, water, climate, etc. comprise the environment (abiotic factors)

3. Biodiversity • Because the world has such an array of not only organisms, but many ways in which they congregate and where they live, it is said to be very biodiverse • We as humans experience diversity just among our own populations in many ways: ecologically, culturally, etc.

4. Ecosystems contain a variety of life • When we look at ecosystems, we can’t just look at the “large” inhabitants (such as top predators) • Believe it or not, the largest population in an ecosystem might be a bacterial population!

5. Change is always occurring • As we discussed in evolution, change is always occurring. • Over time, some land is being lost, but there is also land being made due to forces such as volcanism. • New land forming causes species to inhabit it.- pioneer species are small, fast growing plants that form on new land in the presence of soil.

6. Change is always occurring • Along with inhabiting new land, there is a cycling process among the species that live on previously inhabited lands • This cycling, or “species replacement” is called succession • There are two types of succession- primary succession is replacement that happens where life has not existed before- secondary succession is replacement that happens in areas that have experienced growth before (the growth may have been cut down, caught fire, etc.)

7. succession

8. How does energy flow? • Energy flows up in an ecosystem • The primary source of energy is the sun • The sun provides this energy for plants (as well as algae and some bacteria), which are called primary producers.-primary producers are important because they create organic material through photosynthesis • Those that consume plants (herbivores), make up the first level of consumers called primary consumers-a consumer eats plants, animals, or both to get the energy necessary for them to live. The levels of consumers can go from primary to tertiary

9. How does energy flow? • The levels just mentioned (primary producer, primary consumer, etc.) are called trophic levels. • The trophic level an organism belongs to determines where they get their energy from • So, if we were looking at a food chain, or the path the energy takes up the trophic levels, this is how the energy would move. Sungrassgazellelion The primary energy comes from the sun, which is absorbed by the grass that the gazelle eats. That gazelle gets eaten by the lion.

10. Energy movement • When going up a food chain, the amount of energy that each subsequent level receives is about 10% of the previous level’s. • This is shown in an energy pyramid-going up each level, there is less energy moving up-each level also has fewer organisms in it

11. Questions • If only 10% of energy flows up the trophic levels, what happens to the other 90%?

12. Food chains show energy flow

13. Food chains show energy flow • A food chain shows the path of energy through the trophic levels of an ecosystem • The first level is the producers (plants, algae, photosynthetic bacteria) • The second level is the first level of consumers, which are herbivores (those that eat the producers) • The third level begins the chain of animals eating other animals-in these levels, the animals can be carnivores (meat eaters) or omnivores (meat and plant eaters)

14. Food chains show energy flow • Fungi and non-photosynthetic bacteria are not left out of the equation, even though their presence may not be written out in a food web or a food chain • Fungi and bacteria are decomposers, which means they cause material to decay- bacteria and fungi get their energy from this dead material or organic wastes that are produced at all trophic levels- they are in a group of consumers called detritovores- they are very helpful in recycling nutrients back to the Earth for reuse.

15. What is a top predator? • If a food chain were to go up to higher levels, such as tertiary or quaternary consumers, then those would be carnivores eating other carnivores • These higher level carnivores are said to be apex, or top predators- these predators generally don’t have any natural predators • Examples of top predators: owls, hawks, sharks

16. Top predators

17. Question • Does all energy flow in one straight line, as shown by looking at a food chain?

18. Energy doesn’t just flow in one straight line • No, energy does not flow just how one food chain suggests • We have to combine many food chains together in order to see a more accurate energy flow- this is because many organisms may be located in different trophic levels depending on which food chain we are looking at. • This combination of food chains is called a food web

19. Food web

20. Question • Why is there a limit on how many trophic levels there can be?

21. Only so much energy is available • There can only be so many trophic levels because there is only so much energy available • Because so little energy gets transferred from one level to the next, it doesn’t take long for there to be too little energy left to sustain life • Also, different organisms are different sizes and/or need different amounts of energy to survive compared to others, so it’s hard to see just how much energy there is to go around at any one level-finding the biomass (the dry weight of tissue and other organic matter in a specific ecosystem) is a way we can see just how much energy is available in the ecosystem

22. Self Check Quiz • 1. Why aren’t plants examples of abiotic factors? • 2. When finding the biomass of an ecosystem, what must we eliminate? • 3. Why doesn’t energy flow down the trophic levels? • 4. Why can we only have so many trophic levels? • 5. What happens to the 90% of energy that doesn’t get absorbed and used in an ecosystem? • 6. Draw the pyramid of ecology

23. Biogeochemical cycles • Water, carbon, phosphorous, and nitrogen cycles • In a biogeochemical cycle, a pathway forms when a substance enters living organisms, stays in that organism for some time, and then returns to the non-living environment

24. Water cycle

25. Carbon cycle

26. Phosphorous and Nitrogen cycles • Complex process with four steps1. assimilation-the absorption and incorporation of nitrogen into organic compounds by plants2. ammonification-the production of ammonia by bacteria during the decay of organic matter 3. Nitrification- the production of nitrate from ammonia4. denitrification- the conversion of nitrate to nitrogen gasKNOW- Phosphorous and Nitrogen are both essential in protein/nucleic acid building in organisms

27. Phosphorous and Nitrogen cycles

28. Animations • http://www.epa.gov/ogwdw000/kids/flash/flash_watercycle.html for water cycle • http://www.teachersdomain.org/resource/lsps07.sci.life.eco.nitrogen/ for nitrogen cycle