Populations and sustainability

Population growth % =

Population change during the period / population at the start of the period x 100

Biodiversity

A measure of how many different species live in an ecosystem

Species

A group of similar organisms that breed to produce fertile offspring

Habitat

The area in which an organism lives

Limiting factors

Temperature, light, pH, predators, disease, competition

Immigration

Movement into a particular area increasing population size

Emigration

Movement awat from a particular area decreasing population size

Density dependent/independent factors

Affect the whole population regardless of size and might include earthquakes, fires, volcanic eruption or storms

Carrying capacity

The maximum population size that an environment can sustain

Interspecific competition

Between different species

• compete for same resources

• Results in a reduction of the resource

• Results in smaller populations

• However if one is better adapted it will out compete the other species - competitive exclusion principle

Intraspecific competition

Between members of the same species

• Availability of resource determines population size - results in fluctuations in the no. of organisms present in a population

Stage 1: When a resource is plentiful in a habitat, all organisms have enough of the resource to survive, pop increases

Stage 2: As a result of increase pop, there are more individuals than food or space. Resources are limited so pop decreases

Stage 3: Less competition so more organisms survive and reproduce so increase population

Conservation

The maintenance of biodiversity through human action

Economic pros

To provide resources that humans need to survive and to provide an income. E.g. rainforest species provide medicinal drugs, clothes and food, timber.

Social pros

Many people enjoy the natural beauty of wild ecosystems as well as using them for activities which are beneficial to health by providing a means of relaxation and exersize

Ethical pros

All organisms have a right to exist, and most play an important role within their ecosystem. Many people believe that we should not have the right to decide which organisms can survive.

Sustainable timber production

Small scale timber production

• Coppicing is used - trunk cut close to the ground and new shoots form for the cut

• Rotational coppicing - woodland divided into sections and only certain trees are coppiced - doesn’t block light

• Pollarding - tree cut higher so animals can’t each shoots

Large scale timber production

• Selective cutting - only remove largest trees

• Replant trees to replace them

• Plant trees an optimal distance apart to reduce competition

Commercial fishing

Government control

• quotas

• catch inspection

• reduction of bycatch

• fishing in permitted waters only

Midwater trawling results in less bycatch and habitat damage

Minimum mesh size to allow juvenile fish to escape

Ways to protect ecosystems

National parks and reserves, green belt land, world heritage sites, marine protected areas