Nutrient Cycles, Niche, Succession & Human Impact Flashcards
What is a niche?
Ecosystems include populations of organisms that each fills a specific ecological niche.
The niche of an organism or population of organisms is the role that species plays in a community.
It includes its: Food sources, habitat, use of abiotic components, interactions with members of the same species, interactions with members of other species.
Eg. A garden spider is a predator that hunts for
prey among plants.
The amount of an ecological niche that is occupied by one species is dependant on what?
Competition from other species.
What is a fundamental niche?
The fundamental niche is the largest niche that the organism could occupy in the absence of competition from any other species. The role it could play in absence of competition.
What is a realised niche?
The realised niche is that portion of the fundamental niche that is occupied in the presence of competitors. The role the organisms actually plays in the community.
When does competition occur?
Competition occurs when members of two different species attempt to utilise the same resource such as food, water, shelter.
What are the two possible outcomes of competition?
One species becomes extinct OR the resource is shared between the competing species.
What happens when one species outcompetes another for a shared resource?
The niche of the more successful competitor increases and the niche of the less successful competitor decreases.
What is interspecific competition?
Interspecific competition (overlap) occurs when one species compete for the same resource. This is represented by a niche overlap graph.
There is little competition where the zone of overlap is small.
Two species are likely to coexist in a habitat if the zone of overlap is small.
Patterns of zone overlap in relation to niche:
The zone of overlap will be very high if two species have very similar, if not identical niches.
Competition is very high when the zone of overlap is large
One species usually migrate away from that niche or becomes extinct as a consequence of the intense competition.
What is succession?
Ecological succession involves changes in biotic and abiotic components. Ecosystems are dynamic. They are affected by short term and long term changes in biotic and abiotic factors.
The population of different animals and plant species changes with the seasons. Time scale ranges from decades to millions of years.
What are the 2 types of succession?
Primary Succession
Secondary Succession
What is Primary Succession?
A unidirectional process in which a lifeless ecosystem becomes colonised by progressively more stable communities of living species.
Occurs in lifeless areas where the nutrient-poor soil is incapable of sustaining life.
Eg. Newly formed sand dunes, bare rock which forms as lava cool after volcanic eruption, and exposed rock from a retreating glacier.
What is Secondary Succession?
Natural disasters disrupt the process of succession or the
continuation of a climax community.
The process of succession will occur again in the new environmental conditions of the ecosystem.
Example of Secondary Succession:
Eg. Fire destroys much vegetation and causes many species to die or be displaced from community.
Fire destroys the aboveground vegetation but there are many seeds and tubers in the soil.
The seeds of plants from the previous community will germinate and grow into mature plants.
Species diversity increases as new species move in, colonise the land, and establish a new community.
Secondary succession occurs over a shorter period as colonisation does not begin in a nutrient-poor environment.
The decay of organisms from previous communities provides nutrient-rich soil that allows for more rapid colonisation of the ecosystem by pioneer species.
