Environmental Studies AS - Life processes in the biosphere (Diversity and…
Environmental Studies AS - Life processes in the biosphere
Diversity and ecological stability
Estimates of the total number of species that exist.
Reasons why many species remain undiscovered include:
Ecosystems not been thoroughly researched because they are too inaccessible.
Some species have such similar appearances, structures and behaviours making it difficult to identify.
The males and females look very different and live solitary lives making it difficult to tell if they're the same species.
Many plants only identified when they produce flowers.
The ability to assess species diversity is important in monitoring environmental change, habitat damage and the success of conservation efforts.
Higher diversity in less abiotically extreme environments results in more stable ecosystems in which populations are dominated by biotic factors.
Homeostatic regulation of population size
The maximum population size that can be supported indefinitely without damaging or over-exploiting the environment.
Artificial population control:
Culling of a population may be necessary to conserve species or habitats where natural control mechanisms no long exist.
Predator: prey population relationships:
Self-regulation of population shown by the predator: prey population relationships found in habitats.
Factors affecting morality rates:
Controlled by environmental factors that prevent some individuals born from surviving.
Range of environmental factors affect the likelihood of an organism dying.
density independent factors
density dependent factors
Factors affecting birth rates:
Controlled by natural reproductive potential of the species.
Must be a surplus of young to ensure the survival of the population in bad years.
The higher chances are of death, species will produce more young.
Changes in ecosystems
Temporal changes: ecological succession
If the human activities that destroyed the climax community continue, then a new community of species will develop calling a
If the human activity that produced the
will eventually re-establish the climax community.
In the early stages, a
are very different because of the different conditions.
The final communities that develop are very similar and are mainly controlled by the climate of the region.
A succession that begins in water.
Involves the development of the community on bare rock created by events (such as a volcanic eruption, a cliff fall or glacier retreat).
Refers to the changes that occur in an area that has already reached the climax state.
Natural events or human activities interrupt the sequence of events in succession and can remove the climax community.
Succession will then start again but will occur more rapidly.
Involves the sequence of changes in community composition in an area, starting when it is colonised for the first time.
Sequence of changing communities is called a
. and continues until the climax community develops.
The species that colonise the area change the abiotic factors and lead to more favourable conditions, which allow new species to colonise and out-compete the previous ones.
Grouping organisms and environments
A large geographical region with particular climatic features, in which a characteristic, unique community of species lives.
The niche of a species is the role is plays in its habitat.
The biosphere is that part of the planet that is inhabited by living organisms: land surface, soil, water and atmosphere.
The place where an organism, species or population lives.
The community of organisms living in an area, and their inter-relationships and interactions with their abiotic environment.
Refers to the populations of all the species of plants and animals living in a particular area.
Refers to all the individuals of a species living in a particular area.
A group of organisms that
resemble each other closely
and form a
reproductively isolated group
Very closely related species may be
but do not in the wild either because they live in
The study of organisms to assess how they may be grouped or classified according to how closely related they are.
Adaptation to the environment
Species interdependence and control of abiotic factors
Turbulence and physical damage