Unit 5 Lecture 27

Question 1

Explain the study with the Piaster (starfish)

Answer 1

• Starfish predation on barnacles increase species richness
• In one group with starfish present, the number of species in a population increased
• In another group without starfish, the number of mussel increase and number of other species present decreases

Keeping a dominant species prevent competition exclusion form occurring

Question 2

What does keystone species mean?

Answer 2

Species that have an effect on disproportionately large for their abundance
- Large effect on community composition relative to biomass
- Often top predators
- Loss of such species has consequences

Question 3

Whats the difference between keystone species and dominant species?

Answer 3

Keystone: have large effects on their communities in spite of their low abundance and biomass

Dominant: (corals) have large effects on their communities by virtue of their high abundance and biomass

Question 4

What happens if starfish were taken away

Answer 4

Starfish has a negative impact on barnacles and mussels, and barnacles and mussels have a negative impact on each other
- since mussels are a bigger competitor, they will dominate and the number of barnacles decreases

Question 5

Difference between interference comp and exploitative comp?

Answer 5

Interference: When one organism physically restricts another organism’s access to resources

Exploitative: when individuals interact indirectly as they compete for common resources, like territory, prey or food. (shading by neighboring plant)

Question 5

Difference between interference comp and exploitative comp?

Answer 5

Interference: When one organism physically restricts another organism’s access to resources

Exploitative: when individuals interact indirectly as they compete for common resources, like territory, prey or food. (shading by neighboring plant)

Question 6

How are beavers keystone species?

Answer 6

More beavers = more wetlands
More wetlands = more wetland organism

Beavers are ecosystem engineers that act as keystone species

Question 7

What are ecosystem engineers?

Answer 7

Species that modify the habitat (beavers build damn, stabilize rivers)

Question 8

How are prairie dogs keystone species

Answer 8

burrow and make holes in fields to bring nutrition closer to the surface for spring. From this snakes go in these holes, rabbits, ferrets etc.

Prairie dogs making ecospace for other species

Question 9

What are the 2 effects prairie dogs have on the ecosystem

Answer 9

1. Through consumption and being consumed
2. through burrow contraction

Question 10

What are elephants?

Answer 10

Large keystone herbivore converts woodlands into savanas
- This effect totally change species compositions (plants and animals)

Question 11

Name some roles that elephants have

Answer 11

1. Browsing changes planet structure and composition
2. Soil compaction influences water table
3. Movement of phosphates across the landscape
4. Microbial fermentation of plant materials leads to release of methane

Question 12

Are bison a keystone species or dominant

Answer 12

Keystone because they have a high impact
- Make holes in the ground that slowly evolve into ponds