(ONLY L.A.'S) GEE L.4 Dugdale Ecology PART 1

Biodiversity, communities & conservation

Explain the difference between mutualism, competition and predation

• Mutualism: a positive interaction (+/+) where both species in the interaction benefit from it.

  • Commensalism (+/0) can become mutualistic

• Competition: All (- / -) interactions

  • Interspecific competition occurs when species compete for a resource that is in short supply, limiting the survival & reproduction of both individuals/species.

  • Competitive exclusion: Local elimination of a competing species as a result of strong competition. Principle: 2 species competing for the same limiting resource cannot coexist in the same place.

• Predation: An interaction in which an individual of one species (predator) kills and eats an individual from a different species (prey)

  • A form of exploitation: any + / - interaction in which individuals of 1 species benefit by feeding on individuals of another species.

What are the 2 components of species diversity and what do they entail

• Species richness: the total number of different species in the community

• Relative abundance: the proportion each species represents of the total individuals in the community

Define what an ecological niche is and explain the competitive exclusion principle in terms of the niche concept

• ecological niche: The total of a species’ use of biotic (living) and abiotic (non-living) resources

• The competitive exclusion principle: When two different species are ecologically similar, their niches will (likely) be similar. These species can only exist together if there are one or more significant differences in their niches. Due to this competition a species’ fundamental niche (theoretical, e.g. ideally living in trees) may differ from their realized niche (reality, e.g. to avoid competition by living in a tree the species will instead live in bushes nearer to the ground.

• Resource partitioning: Differentiation of ecological niches so similar species can coexist in a community

Distinguish between the fundamental and the realized niche

Fundamental niches: Are all the theoretical possibilities as to where an organism/species can live/survive.

Realized niches: Are the reality of where an organism/species lives.

You can distinguish the two as the Fundamental niches represent all the environmental conditions where a species is able to live and the realized niche is where the species is actually living in. so fundamental niches are larger or the same size as the realized niche

Explain the intermediate disturbance hypothesis

According to the intermediate disturbance hypothesis moderate levels of disturbance can foster greater diversity than either high or low levels of disturbance.

• Disturbance: An event that changes a community, removes organisms from it and alters resource availability. (e.g. fire)

• High levels of disturbance exclude many slow-growing species and select for quick colonisers that reach maturity quickly.

• Low levels of disturbance allow dominant species to exclude less competitive species.

Explain the species area curve

The species area curve quantifies the idea that if all other factors are equal, a larger geographic area will have more species

• Since larger areas have a greater diversity of habitats and microhabitats

• DUS EEN RECHTEVENREDIG VERBAND TUSSEN DE GROOTTE VAN DE HABITAT EN DE HOEVEELHEID SPECIES