Factors That Regulate Natural Populations Section 11.3 Factors That Regulate Natural Populations

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

Density-Dependent Factors ________________________________________________________________________________________________ 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. 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

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