Community InteractionsCommunity Interactions

M4 EnvironmentM4 Environment

Community InteractionsCommunity Interactions

There are 3 basic types of interactions:There are 3 basic types of interactions:

• CompetitionCompetition• PredationPredation• SymbiosisSymbiosis

CompetitionCompetition

CompetitionCompetition

Organisms will compete for a number Organisms will compete for a number of things:of things:

Land territoriesLand territories FoodFood Sexual partnersSexual partners Being closer to needed resources (ex. Sun)Being closer to needed resources (ex. Sun)

When shared resources are in short When shared resources are in short demand, organisms competedemand, organisms compete

Types of competitionTypes of competition

There are 2 type of competition:There are 2 type of competition:

• Intraspecific competitionIntraspecific competition

(competition between members of the (competition between members of the same species)same species)

• Interspecific competitionInterspecific competition

(different species competing)(different species competing)

Competitive ExclusionCompetitive Exclusion

Also known as Also known as GauseGause’’ s principle s principle No two species can occupy the same No two species can occupy the same

niche indefinitely when resources are niche indefinitely when resources are limited. If this occurs one species limited. If this occurs one species will always out compete the other, will always out compete the other, and the and the extinctionextinction may occur if may occur if natural selection (evolution) does not natural selection (evolution) does not reduce the competition between reduce the competition between them.them.

Character DisplacementCharacter Displacement To reduce overlapping To reduce overlapping

niches, natural niches, natural selection may change selection may change the species so that the species so that they can subdivide the they can subdivide the niche and live together niche and live together without direct without direct competition.competition.

Figure: Darwin’s finches underwent character displacement to avoid competition. They now have different niches (because of different beak size) when they are living together on the same island

Social Dominance Social Dominance (Intraspecific competition)(Intraspecific competition)

Some organisms have a highly developed Some organisms have a highly developed organization which dictates which member organization which dictates which member of the same species gets the best resources. of the same species gets the best resources.

• Dominant individuals Dominant individuals will exclude sub-will exclude sub-dominant individuals dominant individuals from resourcesfrom resources

Example- Territorialism is a Example- Territorialism is a form of competition where form of competition where dominant individuals get the dominant individuals get the best areas to livebest areas to live

Dominance hierarchy (“pecking order”)

Social DominanceSocial Dominance

PredationPredation

Predation Predation

Predation is a very important concept Predation is a very important concept in Ecology. All organisms need food in Ecology. All organisms need food to live. to live.

A predator is an organism that feeds A predator is an organism that feeds directly upon another organism directly upon another organism (prey), (prey), whether or not it kills the prey whether or not it kills the prey to do so.to do so.

Predation and PreyPredation and Prey

Predation shapes Predation shapes the natural the natural communities and communities and influences the influences the distribution and distribution and abundance of prey.abundance of prey.

Rabbit population without preyRabbit population without prey

Rabbit Pop. with PredationRabbit Pop. with Predation

ParasitismParasitism

Parasites are organisms that live on Parasites are organisms that live on or in other organisms ( the host), or in other organisms ( the host), taking nutrients from the host taking nutrients from the host without killing themwithout killing them (at least not (at least not right away)right away)

Parasite are often smaller than their Parasite are often smaller than their hostshosts

““Predator from within”Predator from within”

ParasiteParasite

Tapeworms are parasitic worms that infest the intestinal lining of vertebrates. They do not have

mouths but absorb already digested food

SaprophylismSaprophylism

Saprophyte is any organism that cannot make its food by photosynthesis, and instead gets its nutriment from decaying organic matter. Mushrooms, molds, and other types of fungi are the most abundant saprophytes. Certain types of bacteria are saprophytes, as are some types of orchids

SaprophytaSaprophyta

SymbiosisSymbiosis

SymbiosisSymbiosis

SymSym- together- together BiosisBiosis- life- life

Symbiosis means 2 or more species Symbiosis means 2 or more species forming a close relationshipforming a close relationship

CommensalismsCommensalisms Commensalisms is a common Commensalisms is a common

form of symbiosisform of symbiosis One member of the association One member of the association

benefits while the other is benefits while the other is neither harmed nor helpedneither harmed nor helped

Ex. Some orchids living on trees. Ex. Some orchids living on trees. The orchid gets a place to live and The orchid gets a place to live and the run off of nutrients down the the run off of nutrients down the tree trunk. The tree is neither tree trunk. The tree is neither harmed nor benefits from the harmed nor benefits from the orchidorchid

MutualismMutualism

Another form of symbiosisAnother form of symbiosis Mutualism is when both partners Mutualism is when both partners

benefit from the symbiotic relationship.benefit from the symbiotic relationship.ExamplesExamples

-Human intestinal bacteria -Human intestinal bacteria E. coli E. coli within the colon within the colon produce produce vitamin K, vitamin K, which the human body requires which the human body requires

for the process of blood clotting for the process of blood clotting-Birds eating insects off the backs of Rhinos-Birds eating insects off the backs of Rhinos-Relationship between clown fish and sea anemones-Relationship between clown fish and sea anemones

MutualismMutualism

The clown fish has developed a special relationship with the seaanemone. The clown fish keeps away the anemone’s predators

and the sea anemone protects the fish with its tentacles armed with stinging cells.

MutualismMutualism

T he relationship between the fungus and the alga in lichen is an example of mutualism. This relationship enables each to tolerate harsh conditions

where neither could survive alone. In this partnership, the fungus furnishes the alga with water and provides simple mineral nutrients, while the photosy

nthesizing alga supplies food to the fungus.

MutualismMutualism

Mycorrhizal Fungi (Fri Mycorrhizal Fungi (Fri endly Fungi) endly Fungi)

Fungus and rootsFungus and roots The fungus absorbs The fungus absorbs

minerals and minerals and supplies them to supplies them to the plantthe plant

The plant provides The plant provides nutrients produced nutrients produced by the plant to the by the plant to the fungusfungus

CoevolutionCoevolution

2 species have a close ecological 2 species have a close ecological relationship.relationship.

Co-evolution may occur in any symbiotic Co-evolution may occur in any symbiotic relationship or other relationships. relationship or other relationships.

Ex. host species that has a long history of Ex. host species that has a long history of association with a particular parasite may association with a particular parasite may evolve a greater resistance to it. evolve a greater resistance to it.

They evolve togetherThey evolve together

CoevolutionCoevolution

These hummingbirds have coevolved with certain flowering plants,So the long slender beaks of the bird will fix into the flower to receive nectar. The plant will also deposit its pollen on the bird and the bird will transport the pollen to another plant