ESS chap3. Biodiversity

Biodiversity

amount of biological or living diversity which includes:

the species diversity: richness (nbr of species) + abundance (nbr of individuals per species)

the genetic diversity (range of genetic material - diversity of alleles)

the habitat diversity (range of different habitats in an ecosystem) : vegetative diversity (nbr of species of vegetation)

Speciation

gradual change of a species on the long term as a product of isolation

Simpson’s diversity index

• measures the probability that 2 individuals randomly selected from a sample will belong to the same species (measure the richness)

• the bigger the value (between 0 and 1), the lower the diversity

• N = total nbr of organisms

• n = nbr of organisms per species

biological evolution

Biological process where species change over time through genetic variation, natural selection, and adaptation to their environment.

Evolution

gradual change in the genetic characteristics of successive generations of a species, ultimately giving rise to species different from the common ancestor - changes in the genetic composition of a population over time

natural selection

the individuals with the characteristics that are most adapted for the survival in a certain environment are considered fit and have an advantage to survive and reproduce

Isolation

process by which 2 populations become separated, can be

• geographical : plate activity or formation of mountains, lakes…

• reproductive, behavioural, genetic

• leads to speciation

Plate tectonics

movement of the 8 major rigid plates of the litosphere in relation to each other and to the partially mobile astenosphere below

• constructive : plates move apart and a new land is formed

• destructive : slide against each other, one is subducted beneath the other

• collision : plates collide and form a new range of mountains

  these movements lead to isolation of species (geographical isolation) - adaption

Mass extinction

when 75% of the species on Earth disappear whithin a geologically short time period (few 100 to few 1000 years)

caused by natural (abiotic factors)

example: Creatceous-Tertiary, 65 millions of years ago, because of asteroid impact or volcanic activity, 76% of all species disappered

nowadays: sixth mass extinction, biotic factors (human activity)

How many species on Earth ?

1.8 million classified species

estimated total of species can vary from 5 to 100 million species

why such a gap ?

habitats difficult to reach + lack of finance in researches + difficulties with classification

Factors leading to loss of diversity

• Natural events : volcanic activity, meteor impacts, drought/floods

• Human activities : A HIPPO : Agriculture, Habitat loss, Invasive species, Pollution, Population, Overhunting

Factors making species prone to extinction

• small population size : reduced gene pool

• habitat under threat

• human pressure (hunt, trade)

• high degree of specialisation in dietary needs (panda/bamboo)

IUCN red list

assess the conservation status of species on a global scale to promote conservation

Tropical biomes

occur in less economically developed countries

balance between conservation and using the land to grow the local economy

Role of NGOs and IGOs

NGOs

• rapid response

• unaffected by political considerations

• use public opinion

IGOs

• slow response

• many constraints

• direct access to governments

• international treaties or state laws (Agenda 21 and Rio declaration, 1992)

World Conservation Strategy

• 1980

• IUCN

• to use species and ecosystem in a sustainable way + preserve genetic diversity + maintain life-support systems

protected areas - in situ conservation

aim to preserve the greatest amount of natural habitat within an ecosystem and the ecological interactions that maintain the biodiversity (usually islands)

should be

• large to support a great range of habitats

• high population number of each species

• great productivity

strengths

• resarch and education

• conserve whole ecosystems (not only 1 species)

• preserve many habitats and species

limitations

• expensive

• hard to manage

buffer zones

an area of land that separates two other areas and that is designed to prevent fighting or harm coming to something

keystone species

species that has a disproportionately large impact on its environment relative to its abundance. They play a crucial role in maintaining the structure and function of an ecosystem (bees - pollination)

flagship species

species selected to act as an ambassador, icon or symbol for a defined habitat, issue, campaign or environmental cause. (panda, whales)

CITES

Convention on the International Trade in Endangered Species

to reduce demand for trade and contribute to species conservation

Strengths

• protect many species

• signed by many countries

• works across borders

limitations

• difficult to enforce

• implementation varies between the countries

Captive breeding and zoos - ex situ conservation

species-based approach

a small population is obtained + their natural habitat is reproduced

strengths

• control of predators/ diseases

• abundant food and reduced competition

• can build up quickly

• education purpose

limitations

• small gene pools

• when released they become easy targets

• charistmatic (flagship) species > less-popular and aestheticaly pleasant animals

Lincoln index

• estimation of the size of an animal population

• capture, mark, release, recapture method

• n1 is the number caught in the first sample

• n2 is the number caught in the second sample