Section 11.3 Factors That Regulate Natural Populations.
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Transcript of Section 11.3 Factors That Regulate Natural Populations.
Section 11.3
Factors That Regulate Natural Populations
Density-Independent Factors
________________________________
________________________________
________________________________
Ex. Floods, droughts, etc…
Abiotic
Density-Dependent Factors
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________________________________
________________________________
Competition, predation
Biotic
What is a Community? A biological community
All _____________________ in a given ecosystem at
a given time.
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 “_________________”
Fundamental Niche
The biological characteristics of the organism
and the set of resources individuals in the
population are
__________________________ capable of
using under ______________ conditions.
Realized Niche
The biological characteristics of the
organism and the resources individuals in
a population ____________________use
under the prevailing conditions
Interactions Between Species 3 Main Types
1. Competition 2. Predation 3. Symbiosis
_________________________________
_________________________________
_________________________________
Intraspecific Competition A situation in which members of the
_____________ population complete for resources
Ex. Wood bison competing for food
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
Results of Competition: Population of weaker species
__________________________ One species changes behaviour to use
_____________________ resources __________________ to another
habitat where resources are more plentiful
Interspecific Competition Driving force for populations of species to
evolve _______________________ to allow them to use alternate resources for continued survival.
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
A. insolitususually 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
Example:
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
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
Adaptation of Predators/Prey Feeding adaptations of predators
include Claws, teeth, fangs, stingers, and poison
Animals also display A great variety of defensive adaptations
Defence Mechanisms Cryptic/Protective colouration, or
camouflage Makes prey difficult to spot
Aposematic coloration Warns predators to
stay away from prey
Mimicry In some cases, one prey species may
gain significant protection by mimicking the appearance of another
Two types: Batesian mimicry Mullerian mimicry
In Batesian mimcry
A palatable
or harmless
species
mimics an unpalatable
or harmful
model
(a) Hawkmoth larva
(b) Green parrot snake
In Müllerian mimicry
Two or more unpalatable species resemble each other
(a) Cuckoo bee
(b) Yellow jacket
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
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
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
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
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)
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
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
Other Examples of Exotic Species Purple Loosestrife African Killer Bees West Nile Virus Zebra Mussels