Interactions among species:
 
 

Name of interaction	Type of interaction	Cause of interaction	Impact(s) of interaction
Interspecific Competition	-,-
Predator/Prey	+,-
Parasite/Host	+,-
Herbivore/Plant	+,-
Brood Parasite/Host	+,-
Mutualism	+,+

Human impacts:

Human-caused extinction of some species impacts others

• loss of pollinators, seed dispersers
• loss of keystone predators.Ex: sea otter, sea urchin

• Example: opossum shrimp and kokanee salmon in Flathead Lake, Montana (See Spencer et al paper)

• human caused disturbances
• natural disturbances
• change in disturbance frequency by humans

Practice Questions:

1.  The name of the interaction between species in which both are negatively impacted is _________________.
2.  Give three examples of interactions in which one species is negatively impacted and the other is positively impacted.
3.  How do predation, herbivory, and parasitism differ with regard to:
 (a) the relative sizes of the positively and negatively impacted species
 (b) the seriousness of the negative effect on the negatively impacted species
4.  When a mouse eats a seed, the mouse benefits and the seed, which is an entire (very young) plant, is killed.  Is this interaction competition, predation, parasitism, herbivory, or mutualism? Explain why.
5.  When a bird eats a fruit, but does NOT kill the seed within the fruit, is this interaction most likely to be competition, predation, parasitism, herbivory, or mutualism?
6.  When a bee obtains nectar as food from flowers, is this interaction most likely to be competition, predation, parasitism, herbivory, or mutualism?
7.  For any of the previous questions (4-6) for which the interaction was mutualism, explain how each species benefits from the presence of the other species.
8. Use the example of extinction of some sea otter populations caused by humans to illustrate how the loss of a species as a result of human activity can affect other species in the community.
9.  How can the presence of a predator increase the diversity of species in a community?  A predator that does this is called a(n) ___________________________
10. What is meant by disturbance?  Give examples of disturbances that are natural and examples of disturbances that are caused by humans
 11. Without human disturbance, natural communities stay the same (keep the same species) over time:
 a. always
 b. sometimes
 c. never
12.  Humans affect the rate of disturbance in communities by:
 a. increasing the rate of disturbance
 b. decreasing the rate of disturbance
 c. both a and b
13.  The process through which the species composition (which species are present) of a community changes over time is called ________________________.  How is this process different from the process of evolution (why is this process NOT evolution)?
14. Categorize the following plant species as most likely to be early or late successional species:
 (a) A large tree with has large seeds that generally do not disperse far that is a very good competitor for light.
 (b) A small, non-woody plant with small, wind-dispersed seeds that can disperse very far that can tolerate low nutrient conditions, but is a poor competitor for light.
15. Give two reasons why late successional species tend NOT to be present in communities early in succession.
16.  How do each of the following typically change in the plant species present in a community as succession proceeds from initial stages to the final stage:
 (a) seed size
 (b) ability to compete for light
 (c) ability to tolerate low nutrient conditions
17.  Why do early successional species not remain in communities late in succession?
18.  A community which has undergone a successional sequence and within which there are no more major changes in species composition (which species are present) is called a _______________________.
19.  What is present in a community at the start of secondary succession but absent in a community at the start of primary succession?

HOMEWORK QUESTIONS FROM THE SPENCER ET AL. PAPER:

1.  The main interaction between kokanee salmon and opossum shrimp in Flathead Lake, Montana, is interspecific competition.  Define interspecific competition (based on lecture information) and explain specifically what causes it between kokanee salmon and opossum shrimp, based on their feeding habits and daily movement patterns.

2.  What was the effect of the introduction of opossum shrimp to Flathead Lake, Montana on the populations of grizzly bears and bald eagles that surrounded the lake?  Was this effect desired when the shrimp were introduced?  Clearly explain why introduction of opossum shrimp had this effect on grizzly bears and bald eagles.