ecology part one answers

2. Students’ answers may vary but could include water availability, temperature, space for home, or inclement weather.

6. Three types of symbiosis include: commensalism, where one organism benefits from another’s actions and the second organism neither benefits nor is harmed, such as a bird building a nest on a tree; mutualism, where both organisms benefit from interacting with one another, such as leaf-cutter ants and fungus; parasitism, where one organism benefits at the expense of another, such as ticks living on mammals.

12. Students’ answers may vary but could include crop rotation, use of manure, or addition of fertilizers.

20. Energy and nutrients would be trapped in the tissues of all the organisms that ever existed in the ecosystem. There would likely be a shortage of nutrients and energy available for the environment.

22. (a) Pyramid A best represents a sustainable ecosystem.

(b) Pyramid B does not follow the 10 percent rule as you move up the feeding levels. Not enough energy is available to support the top two feeding levels. Pyramid C does not make sense, as the bottom level has to have the most energy.

23. (a) From 1990 to 1997, the mink population is growing the fastest.

(b) Students’ answers may vary but should be close to 8000.

(c) Limiting factors would prevent the mink population from going higher than the ecosystem could support.

(d) Students’ answers may vary but could include human intervention. Humans may have enacted conservation measures, stopped hunting, or controlled the level of mink predation.

33. (a) The purpose of A and C is to act as experimental controls.

(b) A, B, and C will all be yellow. D will turn red.

(c) The plant in D will undergo photosynthesis in the sunny location. The plant will remove carbon dioxide from the water and the pH level will go higher. Phenol red turns yellow only under acidic conditions.

(d) Aquarium water has higher levels of carbon dioxide than tap water due to the animals respiring in the water. The tap water will initially turn red, and it will be impossible to tell which plants in the test tubes have undergone photosynthesis.

35.(a) Assuming the 10 percent rule, the producers contain 520 000 kJ/m2.

(b) 520 kJ/m2.

37. The caribou had a seemingly unlimited supply of food for many generations. Eventually, the food supply was no longer able to support the population of caribou and their population crashed.

38. There were not enough caribou to support the original population of wolves, and they began to die off until the ecosystem reached a carrying capacity able to support a specific population of wolves.

41. (c) Energy originates from the Sun and the algae convert it into a form that can be used by other organisms in the ecosystem. The energy flows one way through the food chain. At each feeding level, only about 10 percent of the energy is transferred. Matter cycles through the organisms of the ecosystem, moving from the algae through the consumers, and eventually from the consumers back to the producers. Movement of matter is cyclical.

(d) Students’ answers may vary but could include an increase in the numbers of trout since the trout have a greater food supply. Or, the algae eaters may increase too much and decrease the overall amount of algae, which in turn will cause the numbers of algae eaters to decrease.


Pg. 48


1. habitat, ecosystem, biome, biosphere

2. (a) Many different types of species are present including ducks and trees.

(b) Students’ answers may vary but could include: a population of ducks; a population of a particular species of tree.

(c) Students’ answers may vary but could include a description of the community that includes the populations of trees, ducks, and other organisms in and on the water.

(d) It is the interaction of the community and the local abiotic factors that makes up this ecosystem. The ecosystem includes the ducks swimming in the water of the wetland, plants in the water, and trees on the bank, shading the ground below them and providing a habitat for other organisms.

3. (a) Photosynthesis converts carbon dioxide into sugars.

(b) Cellular respiration transforms sugars into carbon dioxide.

5. Carbon, hydrogen, oxygen, and nitrogen are elements found in most organisms.

7. (a) Nitrifying bacteria convert ammonia into nitrates, which plants absorb through their roots and use to grow.

(b) Denitrifying bacteria convert nitrates back into nitrogen gas, which returns to the atmosphere.

17. Photosynthesis is the process where plants convert light energy into chemical energy. Other organisms that cannot produce their  own energy can then use this chemical energy to grow new tissue, reproduce, and run cellular processes. Without photosynthesis, no new energy would be able to enter the ecosystem.

20. Predators often catch the least healthy prey, which makes the prey population healthier as a whole.  Predators also control the population of the prey, which prevents overpopulation and starvation.

21. Abiotic and biotic limiting factors limit the population of bacteria. The bacteria may run out of space or food.