Define limiting factor
factor which limits the rate of a process
What are the phases of a population growth curve?
Phase 1: slow growth as small number initially present reproducePhase 2: rapid growth as number of breeding individuals increases allowing population to multiply exponentially (no constraints act to limit)Phase 3: stable state as further growth is prevented by external constraints, population fluctuates but remains relatively stable, birth rate = death rate (approx)
What is carrying capacity?
the maximum population size that an environment can support
Define immigration
The movement of individual organisms into a particular area
Define emigration
The movement of individual organisms away from an area
What are density independent factors?
Factors that have an effect on the whole population regardless of its size - are capable of dramatically changing population size and even removing a population from a region entirely
Examples of density independent factors
Earthquakes, volcanic eruptions, fires, storms
What is interspecific competition?
competition between different species
What is intraspecific competition?
competition between members of the same species
What results from interspecific competition?
Smaller populations than if only one species was present due to a reduction in the recourse they compete over being available for each species - or in some cases one species will be outcompeted and the less well adapted species will decline in number
What is the competitive exclusion principle?
No two species can occupy the same niche in the same habitat at the same time - the one that uses the resources more effectively will eliminate the other
What is an example of interspecific competition in the uk?
Red and grey squirrels - grey squirrel from Native America introduced, and as able to eat a wider range of food and able to store more fat, they were better adapted, however this reduced food supply available to red squirrels leading to a decline in their population
What are the stages of intraspecific competition?
Stage 1: Resource is plentiful so pop increases as enough for survival and reproductionStage 2: Increased pop leads to resources becoming limited so no longer enough for all organisms so pop decreasesStage 3: Smaller pop means less competition exists so more survive and reproduce so population growsThis then repeats
Define predation
the capturing of prey in order to sustain life
What is predation an example of?
Interspecific competition
What are the stages on predator-prey relationships
Stage 1: increase in prey pop provides more food for predators so they survive and reproduce and pop increasesStage 2: Increased amount of predators causes a decline in prey population, its death rate being higher than birth rateStage 3: Reduced prey population no longer supports large predator pop and intraspecific competition increases resulting in less predatorsStage 4: Reduced predator number allows a greater number of prey to survive and cycle repeats
Define conservation
the maintenance of biodiversity through human action or management
What is sustainable development?
Management of ecosystems in a way that natural resources within them may be used without running out
What is reclamation?
the process of restoring ecosystems that have been damaged or destroyed
Why might controlled burning of forest be carried out?
In order to halt succession and increase biodiversity
Define preservation
The protection of an area by restricting or banning human interference
Why are some people against preservation of natural environments?
They argue there is no point in having a resource that cannot be used
What are the main 3 categories for the benefits of conservation?
Economic, Social and ethical
Define sustainable resource
A renewable resource that is being economically exploited in such a way that it will diminish or run out
Outline the aims of sustainability (5)
- Preserve the environment- Ensure resources remain available for future generations- Allow humans in all societies to live comfortably- Enable less economically developed countries to develop through exploiting their natural resources- Create a more even balance in the consumption of these resources between more and less economically developed countries
What technique is used for small scale sustainable timber production?
Coppicing - tree trunk is cut close to the ground, new shoots form from the cut surface and mature and eventually cut and in there place more are produced, rotational method used
How does rotational coppicing maintain biodiversity?
The trees never grow enough to block sunlight so succession cannot occur and more species may survive
What technique is used for large scale sustainable timber production?
Felling - felled trees are destroyed and will not regrow, it is made sustainable by: selective cutting (removing only largest), replanting, planting at optimal distances to prevent competition, managing pests and ensuring areas of forest remain for indigenous people
Disadvantages of large scale timber production
Habitat is destroyed, soil minerals are reduced and the soil left is susceptible to erosion as trees help with the binding of soil, removal of water and maintenance of nutrient levels
What is being done to combat overfishing?
- International agreements on the number of fish that can be caught (of specific species within an area)- Use of nets with certain sized meshes so only mature fish are caught- Only allowing commercial fishing at certain times of the year, protecting breeding season- Introduction of fish farming to prevent loss of wild species