Community Interactions M4 Environment

Community Interactions There are 3 basic types of interactions: Competition Predation Symbiosis

Competition

Competition Organisms will compete for a number of things: Land territories Food Sexual partners Being closer to needed resources (ex. Sun) When shared resources are in short demand, organisms compete

Types of competition There are 2 type of competition: Intraspecific competition (competition between members of the same species) Interspecific competition (different species competing)

Competitive Exclusion Also known as Gause’s principle No two species can occupy the same niche indefinitely when resources are limited. If this occurs one species will always out compete the other, and the extinction may occur if natural selection (evolution) does not reduce the competition between them.

Character Displacement To reduce overlapping niches, natural selection may change the species so that they can subdivide the niche and live together without direct 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 (Intraspecific competition) Some organisms have a highly developed organization which dictates which member of the same species gets the best resources. Dominant individuals will exclude sub-dominant individuals from resources Example- Territorialism is a form of competition where dominant individuals get the best areas to live Dominance hierarchy (“pecking order”)

Social Dominance

Predation

Predation Predation is a very important concept in Ecology. All organisms need food to live. A predator is an organism that feeds directly upon another organism (prey), whether or not it kills the prey to do so.

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

Rabbit population without prey

Rabbit Pop. with Predation

Parasitism Parasites are organisms that live on or in other organisms ( the host), taking nutrients from the host without killing them (at least not right away) Parasite are often smaller than their hosts “Predator from within”

Parasite Tapeworms are parasitic worms that infest the intestinal lining of vertebrates. They do not have mouths but absorb already digested food

Saprophylism 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

Saprophyta

Symbiosis

Symbiosis Sym- together Biosis- life Symbiosis means 2 or more species forming a close relationship

Commensalisms Commensalisms is a common form of symbiosis One member of the association benefits while the other is neither harmed nor helped Ex. Some orchids living on trees. The orchid gets a place to live and the run off of nutrients down the tree trunk. The tree is neither harmed nor benefits from the orchid

Mutualism Another form of symbiosis Mutualism is when both partners benefit from the symbiotic relationship. Examples -Human intestinal bacteria E. coli within the colon produce vitamin K, which the human body requires for the process of blood clotting -Birds eating insects off the backs of Rhinos -Relationship between clown fish and sea anemones

Mutualism The clown fish has developed a special relationship with the sea anemone. The clown fish keeps away the anemone’s predators and the sea anemone protects the fish with its tentacles armed with stinging cells.

Mutualism The 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 photosynthesizing alga supplies food to the fungus.

Mycorrhizal Fungi (Friendly Fungi) Mutualism Mycorrhizal Fungi (Friendly Fungi) Fungus and roots The fungus absorbs minerals and supplies them to the plant The plant provides nutrients produced by the plant to the fungus

Coevolution 2 species have a close ecological relationship. Co-evolution may occur in any symbiotic relationship or other relationships. Ex. host species that has a long history of association with a particular parasite may evolve a greater resistance to it. They evolve together

Coevolution 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