genetic diversity
characterised by the range and richness of of genetic characteristics within a species or population. It’s the variation the genetic composition that makes very individual unique (except identical twins)
what are several reasons as to why genetic diversity is important
- a rich genetic diversity means population can adapt to environmental changes
- enhances the survival rate of a species, ensuring changes in the environment of diseases will not be able to wipe out entire populations as there will always be individuals with the necessary traits to survive
- genetic variations within a population lead to the the development of new traits, driving the evolution ion species over time
mutations
sudden changes in the DNA sequence and the primary source of genetic diversity
what can mutations be caused by?
- DNA replication errors
- environmental factors such as exposure to radiation and chemicals that can cause changes in the DNA structure
habitat diversity
refers to the different range of habitats in an ecosystem or biome
biodiversity
broad concept encompassing total diversity which includes species diversity, habitat diversity and genetic diversity
species diversity in communities
a product of two variables, the number of species (richness) and their relative proportions (eveness)
advantages of a habitat with high biodiversity
- resilience and stability due to the range of plants present of which some will survive floods, droughts, insect attacks and diseases
- genetic diversity –> resistance to diseases
- some plants will have deep roots so can cycle nutrients and bring them to the surface making them available for other plants
why does high biodiversity not always equate to a healthy ecosystem
- diversity could be the result of fragmentation of a habitat or degradation when species richness is due to pioneer species invading bare areas quickly
- managing grazing can be difficult as plant species have different requirements and tolerances to grazing
- some stable and healthy communities have few plants species and therefore are an exception to the rule
how can humans alter genetic diversity
by artificially breeding or genetically engineering populations with reduced variations in their genotypes or even identical genotypes
what are the advantages/disadvantages of humans altering genetic diversity
- produces high yielding animal or crop
- disease could strike and the whole population could be susceptible
biodiversity hotspot
region with a high level biodiversity that is under threat from human activities
characteristics of the 30 biodiversity hotspots areas recognised
- include about 10 in tropical rainforests but also regions in most other biomes
- tend to be nearer the tropics because their are fewer limiting factors in lower latitudes
- they are all threatened areas where 70% of the habitat has already been lost
- the habitat contains more than 1500 species of plants which are endemic
- they only cover 2.3% of the land surface
- they tend to have large densities of human habitat nearby
where does biodiversity arise from
evolutionary processes
through what mechanisms does natural selection occur
- within a population of one species there is genetic diversity, this is called variation
- due to natural variations some individuals will be fitter than others
- inter individuals will have an advantage and reproduce more successfully
- the offspring of fitter individuals may inherit the genes that give the advantage
speciation
formation of new species when populations of a species become isolated and evolve differently
what can isolations of populations be caused by
- environmental changes forming barriers such as mountain building, changes in rivers, sea levels change, climatic change or plate movements
how has the surface of the earth led to populations being isolated
the surface of the earth is divided into crustal, tectonic plates which have moved throughout geological time, which has led to the creation of land bridges and physical barriers with evolutionary consequences
what have mass extinctions of the past been caused by
tectonic movements, super-volcanic eruption, climate changes, and meteor impact all of which resulted n new directions in evolution and therefore increased biodiversity
summary of the theory of evolution
- each individual is different (except identical twins with the same genotype) due to their particular set of inherited genes and due to mutations
- each will be slightly differently adapted to their environment
- resources are limited for any population and there will be competition for these resources
over time these changes show and the whole population gradually changes
natural selection
those more adapted to their environment have an advantage and flourish and reproduce and those but those less adapted do not survive long enough to reproduce
how may tectonic plates meet
- slide past each other
- diverge, causing physical separation of populations
- converge; these convergent plates may: - collide and be forced upwards, creating mountains and therefore separating populations
- collide and one heavier oceanic plate slides under a lighter continental plate. This is a subduction zone where deep oceanic trenches and volcanic island chains are formed, creating land bridges and myriad new niches
background extinction rate
is the natural extinction rate of all species, thought to about one species per million species a year ie. between 10 and 100 species per year (estimates from fossil records)
how do we recognise a mass extinction having occurred in the past
recognised from fossil record when suddenly fossils disappear from the rock strata and there is an abrupt increase in the rate of extinction
