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