Module 8 Lesson 7 - 5
Completion requirements
Lesson 7 — Species Interactions and Symbiotic Relationships
Self-Check
- Identify the relationship illustrated by each example below:
a. mutualism
b. commensalism
c. parasitism
d. predator/prey
1. The bright rust-colored lichen you see on the surface of rocks is actually two separate species. The hyphae or filaments of the fungus attract water and soluble minerals for the algae (a plant) to use in photosynthesis. In return, the glucose produced by the algae is shared with the fungus.
2. The tiny mites that live on your eyebrows and eyelashes eat dead cells and secretions sloughed from your skin.
3. During wet summers, high numbers of mosquitoes can reduce moose population by sucking enough blood to substantially weaken the animal.
4. Dragonfly larvae feed on the larvae of mosquitoes in ponds. -
Look at this graph of predator-prey cycles:
© Oct 14, 2013 Miranda Dudzik. Textbook content produced by Miranda Dudzik is licensed under a Creative Commons Attribution License 3.0 license.
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If you were not shown the legend, how would you know which line represents predator and which represents prey?
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Which would always have the higher numbers? (Think about the food pyramid.)
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How long would it take for an excess of prey to translate to an excess of predator? (High food supply expresses itself as more babies born the following season.)
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Which would always have the higher numbers? (Think about the food pyramid.)
- What is the length of the lynx-hare cycle in years?
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If you were not shown the legend, how would you know which line represents predator and which represents prey?
I. 1. A
2. B
3. C
4. D
II. a. The prey species is always higher in number, and the predator is lower; therefore, the purple line must be the predators. The excess of prey translates to increased numbers of births the next breeding season - the offspring born the next year. Thus, high prey translates to high numbers of predators in the year or two after the prey spike. Therefore, the purple line must indicate the predators.
b. Count crest to crest or trough to trough. The cycle is approximately 10 years.
2. B
3. C
4. D
II. a. The prey species is always higher in number, and the predator is lower; therefore, the purple line must be the predators. The excess of prey translates to increased numbers of births the next breeding season - the offspring born the next year. Thus, high prey translates to high numbers of predators in the year or two after the prey spike. Therefore, the purple line must indicate the predators.
b. Count crest to crest or trough to trough. The cycle is approximately 10 years.
Reflect and Connect
Deer and moose hunters pride themselves on the size of the animal taken and the number of tines (prongs) on the antlers. (The number of tines increases with the age and size of the buck.) Both hunters and predators keep the prey population in check. However, hunters tend to have a negative effect on the prey gene pool whereas predators have a positive effect. What change in hunting regulations would correct this problem?