Unit 3 (KA7-8) Flashcards
Biodiversity (biological diversity)
The total variation that exists among all living things on Earth.
Refers to the number of species, genetic variation within species and variability of ecosystems.
There are around 2 million known species, there could be 5-20 million in unexplored and inaccessible ecosystems.
Biodiversity databases
There are several biodiversity databases, but ideally one central global one is needed.
This would require international co-operation and a huge level of funding.
Every new species would have to be checked and verified by experts, to avoid incorrect classification.
Reasons for conserving biodiversity
The world’s biodiversity is a natural store of different genes.
Many species have not been tested for potential uses and may become extinct before their value is discovered.
Essential to preserve the wonder and beauty of our planet.
To prevent extinction of species by giving them time to adapt to change.
To maintain a rich variety of resources for the future.
Why measure biodiversity?
Needed to provide conservationists with information so biodiversity can be preserved.
Identifies species and ecosystems in need of protection.
Used to measure environmental change and pollution.
Genetic diversity
Results from variation in the number and frequency of all the alleles of all the genes in a population.
Species diversity
There are 2 aspects :
species richness
abundance of different species
Species richness
Number of different species present in an ecosystem.
Relative abundance
The proportion of each species in an ecosystem.
Communities with one dominant species…
..such as wheat, may have the same number of species (species richness) but are less diverse than an area with a more even balance of species.
Ecosystem diversity
The number of distinct ecosystems present in a defined area.
Scotland is a small country with a high ecosystem diversity.
Island biogeography
The study of factors affecting the distribution and diversity of species on islands.
Species richness is related to island size and distance from the mainland.
Fewer species colonise an island a large distance away from the mainland.
Large islands have higher immigration rates and lower extinction rates (as they have more food and other resources).
Island
True islands are surrounded by water.
Habitat islands are surrounded by dissimilar habitat.
Overexploitation
Overexploit = remove individuals faster than they can be replaced by reproduction. eg. overfishing.
Overexploitation is not sustainable.
Exploitation
To make the best use of a natural resource
Causes of overfishing
Rapid decline in fish stocks as a result of uncontrolled fishing using large nets and sonar to locate shoals.
Preventing overfishing
Fishing quotas, fewer boats, restricted time at sea and restricted fishing areas.
Monitoring harvest species
Harvested species can be monitored using PCR and gel electrophoresis to identify them.
Over exploitation - whaling
Commercial whaling with modern harpoons and boats caused a dramatic decline in global whale populations.
Whaling moratorium
1986 - International Whaling Commission imposed a moratorium (ban) on commercial whaling, allowing limited numbers to be caught for research only.
This has reversed the decline in whale numbers
Bottleneck effect
Causes a reduction in the genetic diversity of a species.
Occurs when a large proportion of a population is wiped out at random by a natural disaster or by hunting.
Rarer alleles may be lost, and even if populations recover their numbers, there is less genetic variation in the surviving population.
Loss of genetic diversity can lead to inbreeding and may reduce the ability of a population to adapt to change.
Fragmentation
Natural ecosystems are broken up by roads, or are cleared for agriculture.
The total surface area of the combined fragments is less than the original habitat.
Degradation of fragment edges leads to further habitat loss, and an increase in the ratio of edge : interior.
This favours edge species over interior species, which need undisturbed habitats.
Small fragments support smaller populations with a lower genetic diversity.
Habitat corridors
Used to link isolated fragments with a corridor or ‘stepping stones’ of quality habitat.
Allows species to move between isolated fragments to feed, mate and recolonise after a local extinction.
Problems with habitat corridors
They do not solve the problem of loss of interior habitat.
They may spread disease or invasive species between fragments.
Introduced species
Foreign species are accidentally or intentionally introduced to an area which they did not previously inhabit.
Occurs as a result of plant collecting, the pet trade, commercial shipping, tourism or biological control.
Naturalised species
Establish themselves in the wild community and live and breed within it without affecting it too much.
Invasive species
Spread rapidly in the wild community and eliminate native species.
They prey on or outcompete native species, and may hybridise with them.
They have no natural predators, pathogens or parasites to control their numbers in their new environment.
Characteristics of invasive species
Characteristics include rapid growth and reproduction rates, high dispersal rates, tolerance and adaptability.
Invasive species - effects on the economy
Japanese knotweed was introduced as an ornamental plant.
It has no natural parasites, pathogens or grazers in the UK.
It can grow rapidly through the foundations of buildings, regenerates from tiny fragments and is becoming herbicide resistant.
Millions of pounds are spent every year trying to remove it.
Invasive species - effects on health
Giant hogweed was introduced as a garden plant but has become invasive.
It has poisonous sap which causes burns and blisters.
Invasive species - effects on biodiversity
Invasive species affect biodiversity by :
- outcompeting native species and spreading disease (grey/red squirrels)
- preying on native species (mink/water voles)
- hybridising with native species (domestic cat/Scottish wildcat)
