Population and Sustainability OCR A2 Biology

Keywords and quick revision of populations and sustainability, has pictures :)

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  • Created on: 24-05-12 19:43
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Biology F215 Revision
Populations and Sustainability
Key Words
Key Term Definition
The maximum population size that can be maintained over a period of time in a
Carrying capacity
particular habitat.
Clear felling Felling all the trees in an area at the same time.
A struggle between individuals for resources (like food or water) that are not present in
Competition amounts adequate to satisfy the needs of all the individuals who depend on those
The loss of one species from an ecosystem as a result of competition pressure exerted
Competitive exclusion
by another species.
Maintenance of biodiversity. Requires management of resources and may involve
Coppicing Cutting a tree trunk close to the ground to encourage new growth.
Competition for limited resources between organisms of the same species.
Intraspecific competition
Competition for limited resources between organisms of different species.
Interspecific competition
K strategist A species whose population size is determined by the carrying capacity.
Limiting factor Something within the environment that restricts the growth of a population.
Pollarding Cutting a tree trunk higher up above the ground to encourage new growth.
Protection of habitats at risk from human activity.
Reclamation Reversing the effects of human activity.

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What is population growth?
Point A on the graph to the left is called the lag
o In this phase few individuals of a species
are adjusting to the habitat
There is a slow rate of
Point B on the graph is called the log phase
o In this phase resources are plentiful
The rate of reproduction exceeds the death rate (mortality)
Point C on the graph is called the stationary phase
o In this phase the habitat can no longer sustain such…read more

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Which leaves less food for the predator so its population falls
With fewer predators, the prey population then increases
o With more prey, the predator population then increases
Predators may have more than one prey so they aren't as effected by one prey population decreasing
How does this relate to pest control?
Predators can be introduced to deal with pests in a habitat
What are the disadvantages of biological pest control as a control method?
This process is slow to work
o The pest is…read more

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What is intraspecific competition?
Intraspecific competition is competition for limited resources between organisms of the same species
o The individuals compete for exactly the same resources
Those best adapted will survive and reproduce
Making this a process of natural selection
Intraspecific competition slows down population growth
o This is because the population enters the stationary phase and remains relatively stable
If population size falls, competition reduces and the population increases again
If population size increases, competition increases and the population falls again
What is interspecific…read more

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This reduces the size of the less efficient species' realised niche
o Too much overlap may lead to the competitive exclusion of the less
efficient species from the ecosystem
Interspecific competition can limit species distribution as only one
organism can inhabit a
particular niche at a time
o In the example to the right
Chthamalus is better at resisting
desiccation (drying out) and therefore it
can live higher up the shore
Balanus is less adapted to cope with
desiccation and therefore it can only live…read more

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They are later harvested for use in fencing, firewood or furniture
The cycle then continues
What is rotational coppicing?
Rotational coppicing involves cutting sections of a wood each year
o The first section has grown and is ready for coppicing again, by the time return to it
They typically have a 6-20 year cycle but the length of rotation varies with
species/dimensions of wood required
This technique increases biodiversity
o Different areas of wood provide different habitats
Prevents formation of climax community (has fewer species…read more

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Move individuals to enlarge populations to maintain genetic diversity
Restrict migration by fencing
Control predators and poachers
Prevent pollution or disruption or to restrict succession
Raise carrying capacity by providing extra food
How does the increasing human population impact on conservation?
Overexploitation of wild populations
o For food e.g. North Sea cod
o For sport e.g. hunting tigers
o For commerce e.g.…read more

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Thedestruction and fragmentation of habitats to make way for buildings and agriculture
8…read more



A well presented and concisely written set of notes, with clear coloured diagrams and sets of key words and definitions. These would be useful for any A level Biology student needing to study populations, ecological niches, limiting factors and competition as part of their specification. The key words could be used to generate  a set of flashcards could be downloaded and used as a self test.

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