10C: Relationships, keystone species

Question 1

What is a keystone species?

Answer 1

Organism that helps define an entire ecosystem (without them, ecosystem would be drastically different or cease to exist)

Question 2

What are common roles keystone species fulfill?

Answer 2

Apex predator: top of food chain, no natural predators
Ecosystem engineers: organism that creates, significantly alters structure of environment

Question 3

Why are elephants ecosystem engineers?

Answer 3

• Habitat modification
• Water hole creation
• Seed dispersal
• Fire regulation

Question 4

Levels of ecosystem organisation:

Answer 4

Cell, organism, population, community, ecosystem

Question 5

Formula to determine population change:

Answer 5

Future population size (Ni+1 = N + births - deaths + immigration - emigration

(Ni+1) = future population size
(N) = initial population size

Question 6

What is population distribution?

Answer 6

Geographical spread across different area (limited by ideal habitat + ability to tolerate environments)
- Uniform
- Random
- Clumped

Question 7

What are density-independent factors?

Answer 7

Properties of environment unaffected as density changes
- climate
- natural disasters (cyclone)
- Functionally unlimited resources (O2)

Question 8

What are density-dependent factors?

Answer 8

Properties of environment that change with density of species
- Disease
- Predation
- Competition
- Resource availability
- Waste accumulation

Question 9

What occurs at low/high population densities?

Answer 9

At low densities, population growth can be exponential (density-dependent factors will have no impact)
As density increases, density-dependent factors have more impact, and growth rate will slow until population size remains constant

Question 10

What is symbiosis?

Answer 10

Interaction between 2 organisms of different species living close

Question 11

Name the different types of interactions between species

Answer 11

Mutualism (+/+)
Commensalism (+/0)
Predation (+/-)
Parasitism (+/-)
Amensalism (0/-)
Competition (-/-)

Question 12

Explain mutualism

Answer 12

Interactions where both organisms benefit (sea anemone and clownfish)

Question 13

Explain commensalism

Answer 13

Interactions where one organism benefits and the other is not affected (duck on dog’s back across a river)

Question 14

Explain predation

Answer 14

Involves one organism hunting and killing the other for food (bird eating worms, lions eating zebras)

Question 15

Explain parasitism

Answer 15

Interactions where an organism obtains nutrients at the expense of a host (ticks, leeches, mozzies)

Question 16

Explain amensalism

Answer 16

Interactions where one organism experiences some negative effect while other is unaffected (cattle trample on grass)

Question 17

Explain competition

Answer 17

Interactions between two organisms (different or same species) competing for same pool of resources (two species of birds hunting worms - may experience reduced access to food)

Question 18

What are the two types of competition?

Answer 18

Interspecific competition: two different species
Intraspecific competition: two individuals of same species