1. Factors That Regulate Natural Populations
Section 11.3
Factors That Regulate Natural Populations

2. Density-Independent Factors
________________________________________________________________________________________________
Ex. Floods, droughts, etc…
Abiotic

3. Density-Dependent Factors
________________________________________________________________________________________________
Competition, predation
Biotic

4. What is a Community? A biological community
All _____________________ in a given ecosystem at
a given time.

5. Ecological Niche The ecological niche
Is the total of an organism’s use of the _______________ and _____________ resources in its environment
Habitat = organism’s “address”
Niche = organism’s “_________________”

6. Fundamental Niche
The biological characteristics of the organism and the set of resources individuals in the population are __________________________ capable of using under ______________ conditions.

7. Realized Niche
The biological characteristics of the organism and the resources individuals in a population ____________________use under the prevailing conditions

9. Interactions Between Species
3 Main Types
1. Competition
2. Predation
3. Symbiosis
_________________________________

10. Intraspecific Competition
A situation in which members of the _____________ population complete for resources
Ex. Wood bison competing for food

11. Interspecific Competition
Occurs when ___________________species compete for a particular resource that is in short supply
Two Types:
Interference competition - aggression between individuals fighting over the same resource(s)
Exploitative competition - consumption of resource by one species may limit resource availability to other species

12. Results of Competition:
Population of weaker species __________________________
One species changes behaviour to use _____________________ resources
__________________ to another habitat where resources are more plentiful

13. Interspecific Competition
Driving force for populations of species to evolve _______________________ to allow them to use alternate resources for continued survival.

14. Resource Partitioning
Resource partitioning is the differentiation of niches
That enables similar species to _____________ in a community
Ex. Several species of Anolis lizard use different parts of the tree habitats by occupying different perching sites

15. A. insolitus usually perches on shady branches.
Example:
A. insolitus usually perches on shady branches.
A. distichus perches on fence posts and other sunny surfaces.
A. distichus
A. ricordii
A. insolitus
A. christophei
A. cybotes
A. etheridgei
A. alinigar

16. Character Displacement
There is a tendency for characteristics to be more divergent in populations of two species that occupy the same geographical range than in populations of the same two species that are geographically isolated.
Example: Experiments with barnacle species

17. Predation Predation refers to an interaction
Where one species, the predator, kills and eats the other, the prey
Some predator-prey relationships display a __________________ pattern
Predator patterns ____________ behind the prey patterns
Ex. Lynx-Hare

18. Adaptation of Predators/Prey
Feeding adaptations of predators include
Claws, teeth, fangs, stingers, and poison
Animals also display
A great variety of defensive adaptations

19. Defence Mechanisms Cryptic/Protective colouration, or camouflage
Makes prey difficult to spot

20. Aposematic coloration
Warns predators to stay away from prey

21. Mimicry
In some cases, one prey species may gain significant protection by mimicking the appearance of another
Two types:
Batesian mimicry
Mullerian mimicry

22. In Batesian mimcry A palatable or harmless species
mimics an unpalatable
or harmful
model
(a) Hawkmoth larva
(b) Green parrot snake

23. In Müllerian mimicry
Two or more unpalatable species resemble each other
(a) Cuckoo bee
(b) Yellow jacket

24. Symbiosis Means “________________________”
Individuals of two different species live in close (usually physical) contact
At least one species ______________ from the relationship
3 types:
mutualism, commensalism and parasitism

25. Mutualism Mutualistic symbiosis, or mutualism
Is an interspecific interaction that benefits _______________ species
Ex. Bacteria that live in the gut of cows, deer and sheep
Bacteria secrete enzymes to break down cellulose for herbivores
Bacteria gain nutrients for themselves
Called: obligatory mutualism
Neither can grow or reproduce without the other

26. Commensalism In commensalism
One species _______________ and the other is not __________________
Ex. Caribou and artic foxes
Artic fox follow caribou tracks, which uncover small mammals
Ex. Remora (small fish) and sharks
Remora attach themselves to sharks – do not expend energy swimming, receive protection and feed on small pieces of the lemon shark’s prey

27. Parasitism
A symbiotic relationship in which one organism (the parasite) ______________ at the ___________________ of another organisms (host)
Host is often harmed, but not usually killed
Examples: tapeworms, ticks

28. Types of Parasites
Endoparasites: parasites that live and feed within the host’s body (ex. tapeworms that live inside digestive tracts)
Ectoparasites: parasites that live and feed on the outside surface of the host, such as lice, ticks and parasitic mites
Social parasites: parasites that complete their life cycle by manipulating the social behaviour of their hosts (ex. cowbirds that lay eggs in smaller birds nests)

29. Disruption of Community Equilibrium
A natural disaster
Can break down intrinsic interactions among communities organisms
Introduction of exotic (non-indigenous) species
Displace indigenous species from community
Often have few predators
Out compete indigenous species for food and habitat
Prey on indigenous species

30. Introduction of Exotic Species
Example: Introduction of European rabbit in Australia (1859)
Breed rapidly - within decades there were tens of millions of rabbits
Devastated grasslands, deprived indigenous species of food, water and shelter
Introduced virus that selectively targeted rabbits and managed to bring them under control

31. Other Examples of Exotic Species
Purple Loosestrife
African Killer Bees
West Nile Virus
Zebra Mussels