Ecology Review Answers

1. Ecology Review Answers

2. 1. What are the different levels of organization of the biosphere –starting with the individual organism. Add between the words what gets added to make each new level. • (1 pt for order; 1 pt ea for what gets added = 6 pts) • organism + more organisms of the same species = population • population + all the organisms in an area that interact = community • community + abiotic factors = ecosystem • ecosystem + similar ecosystems with same climate and landscape = biome • biome + all organisms on earth and their interactions with the environment = biosphere

3. 2. Give examples of several biotic and abiotic factors in the ecosystem • (1 pt for 3 correct answers on each = 2 pts) • biotic – parasites, predators, prey, disease, competition, availability of producers • abiotic – elevation, condition of soil, amount of precipitation, amount of sunshine…

4. 3. How does useable energy first get into the biosphere? • 1 pt • sun supplies most of the energy to the earth

5. 4. Describe and give examples of mutualism, commensalism and parasitism • 2 pts ea (1 for correct def, 1 for correct ex. = 6 pts) • mutualism: symbiosis in which both species benefit. ex: sunfish and smaller fish that eat the parasites off them • commensalism – symbiosis in which one species benefits and the other is neither harmed nor helped. ex: bird nests in tree; cameleon is camouflaged in bush • parasitism – symbiosis in which one organism benefits (parasite) and the other, usually a larger orgaism (host) is harmed. ex: tick (parasite) sucks blood from a mammal (host)

6. Why is each level in an energy pyramid smaller than the one below? • 2 pts • The energy is taken by the organism that gets it and used for life functions.

7. 6. In an energy pyramid, what percentage of energy is passed from one trophic level to the one above it? • 1 pt • 10%

8. How much energy does an organism at the fourth trophic level get if the bottom trophic level has 5,000 calories? Show your math. • 2 pts: 1 for correct method, 1 for correct answer • 5000 x .1 = 500 x .1 = 50 x .1 = 5 cal

9. What do the arrows in food chains and food webs represent? If a snake eats a mouse, does the arrow point to the snake or mouse? • The arrows represent transfer of energy from one organism to the next. (1 pt) • If a snake eats a mouse, the arrow should go from the mouse to the snake, since the mouse passes its energy to the snake. (1 pt)

10. What is the difference between a food chain and a food web? • 2 pts for a well constructed answer • A food web is a bunch of interconnected food chains. A food chain shows just one pathway for energy to be transferred, while a food web shows the many pathways for energy transfer in a community.

11. What is the effect on a food web if an organism is removed from the top? • 2 pts for a well constructed answer • If a top predator is removed from an ecosystem, the effect can be devastating to the entire balance of the ecosystem. The large herbivores population will boom, and they in turn will eat up the producers, which will affect the smaller herbivores that rely on the producers. Ultimately, all the organisms in the food web will be affected and the populations will shift dramatically. The lack of a top predator leads to an unhealthy ecosystem.

12. What does an ecosystem have to have to sustain many trophic levels? Why? • 2 pts for a well constructed answer • An ecosystem must have a broad and varied producer base to support many trophic levels above it. The smaller the amout of energy available at the producer level, the lower the amount of trophic levels the ecosystem can support above it. This is why deserts, even though they get plenty of sunshine, have so few animals – because the conditions are too dry to support many plants.

13. In what form does energy leave a food chain? • 1 pt • Energy leaves a food chain as heat. Even decomposers produce heat – this is why compost piles and landfills produce steam.

14. What types of organisms fill each trophic level of an energy pyramid (starting at the bottom)? • 5 pts • first producers; then herbivores, followed by omnivores, and finally, carnivores. Of course decomposers can eat at any level.

15. What is the difference between a niche and a habitat? • 2 pts for a well constructed answer • A habitat is where an organism lives, that provides the needs for the organism. The niche is the special role the organism plays, the food it eats, the resources it uses for shelter, the organisms that feed on it, etc., within its habitat.

16. What would happen if two species find themselves in the same niche? • 2 pts for a well constructed answer • This is competition. In a severely competitive situation, one species will die off. Species tend to avoid competitive situations over time. ex: hawk hunts by day and owl hunts same type of prey by night. ex: different species of birds nest in different specific levels of the same type of tree.

17. How does carbon get into the food chain? • Plants absorb carbon in the form of CO2 and use to produce glucose, an energy rich compound. (photosynthesis)

18. How does extra carbon dioxide get put into the atmosphere by humans? • 2 pts • Combustion of fossil fuels, wood, peat and other carbon compounds. • Deforestation reduces the number of plants that can absorb carbon dioxide from the atmosphere.

19. What is the biological process that releases energy from carbon compounds and creates carbon dioxide as waste? • cellular respiration (1 pt)

20. What is the main way nitrogen gets fixed into useable nitrates? • 2 pts for a well constructed answer • There are special nitrogen fixing bacteria that live in nodules (little bumps) on plant (legumes) roots. These bacteria and the plants have a mutualistic relationship. The bacteria get a place to live and also absorb some of the nutrients produced by the plants’ leaves and sent to the roots. The plants get the nitrogen fixed. Legumes include clovers, beans, & soy.

21. What is nitrogen used for in organisms (hint: “to live” is too broad) • 1 pt • Nitrogen is an element in all 20 amino acids. So nitrogen is used to make amino acids which are used to make proteins. • Also, nitrogen is an element in the nitrogen bases, the steps of the DNA ladder.

22. How do carbon, water and nitrogen get returned to the ecosystem from plants and animals after they die? • Carbon is combusted by decomposers and returned as CO2 gas through cellular respiration, or the carbon compounds sink into the earth and remain there for long periods. 2 pts for a well constructed answer • Nitrogen compounds cycle back through the soil and are taken back up through plants, or they are returned to their gas form by special archaea in a process called denitrification. 2 pts for a well constructed answer • Water is also a waste product of cellular respiration. 1 pt

23. In a predator – prey relationship do the predators control the numbers of prey or do the prey control the numbers of predators? • Both (1 pt)

24. What is ecological succession? • 2 pts for a well constructed answer • The process of establishing new life in an area where the ecosystem has to “start over” due to a natural (forest fire, lava flow, etc) or unnatural (agriculture, deforestation, etc) event.

25. What is the difference between primary succession and secondary succession? • Primary succession has to start by building up soil, as after a lava flow from a volcano. (1 pt) • Secondary succession already has soil to begin, as after an area that has been used for crops is allowed to go back to nature. (1 pt)

26. What is the order of succession, from the first organisms to the climax community? • 5 pts • lichen, • moss and other nonvascular low plants, • ferns and other small plants, • small bushes and shrubs, • small trees, and finally • the larger trees of the climax community that are well adapted to the area.

27. Why can there never really technically be climax communities? • 2 pts for a well constructed answer • The environment is changing all the time. Communities are in a constant state of flux. The only permanent thing is change.