Populations Flashcards
Describe the population growth curve
1- there is slow growth
Birth > Death
2- there is rapid growth, population is growing exponentially as there are no factors limiting growth Birth»_space; Death
3- Stationary phase
Stable population size with fluctuations, due to limiting factors
Birth= Death
What are the limiting factors acting on the stationary phase?
Biotic- predation, competition and disease
Abiotic- temperature, light intensity, pH, availability of O2 and H2O
What is carrying capacity?
The maximum stable population size that an environment can carry
What is migration
Immigration- organisms moving into an environment
Emigration- organisms moving away from an environment
What are density independent factors?
Factors that can affect a population regardless of its size
Eg. earthquakes, volcanoes
What is the difference between inter and intraspecific competition?
Inter- competition between different species
Intra- competition between members of the same species
What is the competitive exclusion principle?
When two species of different organism are competing for the same resource, but one is better adapted
The less better adapted individual is outcompeted and will decline in number, which may lead to extinction or emigration
Describe the predator- prey relationship
1) Increase in prey population- more food for predators- predator population size increases as more survive and reproduce
2) Increase in predator population- more prey are eaten- decline in prey population
3) Reduced prey population- can no longer support the predator population- predator population decreases
4) Less prey being eaten- more prey survive and reproduce- increase in prey population
What is the difference between conservation and preservation ?
Conservation- the maintenance of biodiversity through human action
Preservation- protection of an area by restricting human access so that the ecosystem is kept in its original state
Why is conservation important?
Economic- bringing tourists, creating jobs, eg medicinal
Social- humans enjoy biodiversity
Ethical- all organisms have a right to exist, we have a responsibility to conserve environments for future generations
What is meant by a sustainable resource?
A renewable resource that will not run out
Important to preserve the environment, ensure that there are resources for future generations
Also, to enable less economically developed countries to develop and for there to be a balance
Describe coppicing
When a tree trunk is cut close to the ground
Shoots rapidly regrow
Rational coppicing can also occur, doing bits of the forest at a time
This maintains biodiversity as trees do not grow tall enough to block sunlight
What is the benefit of pollarding over coppicing ?
In pollarding, the trunk is cut higher up
This prevents herbivores from eating the shoots
How are the problems with large scale timber production (felling) overcome?
Only cutting the largest trees- selective cutting
Replace trees through replanting
Plant trees an optimal distance apart to reduce competition
Manage pests and pathogens
What are the problems with felling?
Habitats destroyed
Soil erosion
Soil minerals reduced
