10C: Relationships, keystone species Flashcards
What is a keystone species?
Organism that helps define an entire ecosystem (without them, ecosystem would be drastically different or cease to exist)
What are common roles keystone species fulfill?
Apex predator: top of food chain, no natural predators
Ecosystem engineers: organism that creates, significantly alters structure of environment
Why are elephants ecosystem engineers?
- Habitat modification
- Water hole creation
- Seed dispersal
- Fire regulation
Levels of ecosystem organisation:
Cell, organism, population, community, ecosystem
Formula to determine population change:
Future population size (Ni+1 = N + births - deaths + immigration - emigration
(Ni+1) = future population size
(N) = initial population size
What is population distribution?
Geographical spread across different area (limited by ideal habitat + ability to tolerate environments)
- Uniform
- Random
- Clumped
What are density-independent factors?
Properties of environment unaffected as density changes
- climate
- natural disasters (cyclone)
- Functionally unlimited resources (O2)
What are density-dependent factors?
Properties of environment that change with density of species
- Disease
- Predation
- Competition
- Resource availability
- Waste accumulation
What occurs at low/high population densities?
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
What is symbiosis?
Interaction between 2 organisms of different species living close
Name the different types of interactions between species
Mutualism (+/+)
Commensalism (+/0)
Predation (+/-)
Parasitism (+/-)
Amensalism (0/-)
Competition (-/-)
Explain mutualism
Interactions where both organisms benefit (sea anemone and clownfish)
Explain commensalism
Interactions where one organism benefits and the other is not affected (duck on dog’s back across a river)
Explain predation
Involves one organism hunting and killing the other for food (bird eating worms, lions eating zebras)
Explain parasitism
Interactions where an organism obtains nutrients at the expense of a host (ticks, leeches, mozzies)
Explain amensalism
Interactions where one organism experiences some negative effect while other is unaffected (cattle trample on grass)
Explain competition
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)
What are the two types of competition?
Interspecific competition: two different species
Intraspecific competition: two individuals of same species
