OCR Module 6 Populations and Sustainability Flashcards
What is a population?
Group of organisms that belong to the same species, live in the same habitat and are part of the same community and ecosystem.
What is a population growth curve?
Growth of a new population over time.
- Phase 1 - Period of slow growth: Small numbers of individuals initially present reproduce to increase total population. BR>DR
- Phase 2 - Period of rapid growth: Total population multiplies exponentially, no constraints act to limit population explosion.
- Phase 2 - A stable state: Further growth prevented by external constraints, size fluctuates, BR=DR.
a. Reached carrying capacity - maximum pop size the environment can support.
What are limiting factors?
• Factors that prevent further growth of a population, and may cause it to decline.
- Abiotic factors - Non living factors such as temperature, light, pH, water/O2 availability.
- Biotic factors - Living factors such as predators, disease and competition.
How does migration affect population size?
- Immigration - Movement of individual organisms into a particular area which increases population size.
- Emigration - Movement of individual organisms away from a particular area which decreases population size.
What are density independent factors?
• Factors that have an effect on the whole population regardless of its size.
- Dramatically change population size.
- Earthquakes, volcanic eruptions and storms.
- Able to remove whole populations of a species from a region.
What are the types of competition?
• Interspecific competition - 2 or more different species compete for the same resource.
1. Better adapted species outcompetes the other.
2. Outcompeted species will have fewer resources and therefore less chance of survival and reproduction.
3. Its’ population size likely to decrease or eliminate.
• Intraspecific competition - Members of same species compete for same resource.
1. Higher availability of the resource allows reduced competition and greater population size which rises above carrying capacity.
2. When resources are limited, organisms re-compete so size falls.
3. Less competition due to smaller population means more organisms survive and reproduce, resulting in increased population size.
What is predation?
• An organism kills and eats another to sustain life.
1. A type of interspecific competition.
Predator-prey relationships
- Population sizes of predators and preys are interlinked and cause fluctuations of both populations.
- Stage One - Increase in prey population provides more food for predators, allowing predators to survive and reproduce, increasing their population.
- Stage Two - Increased predators eat more prey, causing a decline in the prey population as the BR < DR
- Stage Three - Reduced prey population can no longer support large predator population. Intraspecific competition arises, resulting in decrease of predator population.
- Stage Four - Low predator size allows prey to survive and reproduce, increasing prey population.
What is conservation?
• Maintenance of biodiversity through human action.
- Management of ecosystems so natural resources can be used without running out, known as sustainable development.
- Includes reclamation - Process of restoring ecosystems that have been damaged or destroyed
- Conservation is dynamic and needs to adapt to constant change.
Why is conservation important?
• Economic - Non sustainable removal of resources such as hardwood will eventually lead to collapse of that industry.
1. Rainforest species may be chemically or medically useful.
• Ethical - All organisms have right to exist and play an important role within their ecosystem.
1. Moral responsibility for future generations to conserve wide variety of existing natural ecosystems.
• Social - Presence of different plant and animals enrich our lives.
1. Patients recover more quickly when supported by plants and relatively natural environment.
What is preservation?
• Protection of an area by restricting or banning human interference, so the ecosystem is kept in its original state.
1. Used to conserve ecologically, archaeologically or palaeontologically sensitive resources that can easily be damaged or destroyed by disturbances.
What are the aims of sustainability?
A sustainable resource is a renewable resource that is being economically exploited in such a way that it will not diminish.
• Aims of sustainability:
1. Preserve environment
2. Ensure resources are available for future generations
3. Enable LEDCs to develop
4. Create balance in consumption of resources between MEDCs and LEDCs.
How is sustainable timber production carried out on a small scale?
- Coppicing: Tree trunk is cut close to ground, new shoots form from the cut surface and mature.
- Shoots eventually cut and more produced again.
- Maintains biodiversity as trees never grow enough to block sunlight and so more species can survive.
How is sustainable timber production carried out on a large scale?
- Carried out by felling large areas of forest which are destroyed and will not grow.
- Carried out sustainably by:
a. Practising selective cutting where only the largest trees are removed.
b. Replacing trees by replanting rather than waiting for natural regeneration. Ensures biodiversity, mineral and water cycles are maintained.
c. Plant trees optimal distances apart to reduce competition and maximise yield.
What are the disadvantages of large scale timber production
- Habitats destroyed
- Minerals in soil reduced
- Bare soil which is left is susceptible to erosion
