4.2.1 Biodiversity Flashcards
what is a species?
a group of similar organisms capable of interbreeding to produce fertile offspring
what is a population?
all the members of one particular species living in a given area at one time
what is a Community?
all the members of all the species living in a given area at one time
what is a Habitat?
the place where a species lives
what is a Ecosystem?
a dynamic system consisting of living organisms, the physical environment and the interactions between all of these
what is a Niche?
the role of an organism in its ecosystem (including what it requires from the ecosystem and what it contributes to the ecosystem
what is Biodiversity?
the variety and complexity of life in a given area; this includes the variety of habitats, the number of different species present, how even their population sizes are and the genetic diversity (both within and between species). When biodiversity is quantified, it has two components: species richness and species evenness
what is Species richness?
the number of different species present in an area, quoted as a single number; the higher the species richness, the higher the biodiversity is likely to be
what is Species evenness?
the extent of similarity (evenness) in the population sizes of each species in an area, or the relative abundance of each species; high species evenness is a component of high biodiversity, as it means that all population sizes are similar (such that the ecosystem is balanced); low species evenness generally corresponds to lower biodiversity, as it suggests that one or two species may be dominant, having much greater population sizes than other species (such that the ecosystem is unbalanced).
what is a Keystone species?
a species which has a significant effect on the habitat, despite its own relatively low abundance or total biomass; many other species depend upon the keystone species, which in many cases is the top carnivore in a food chain (e.g. grey wolf) or a species which modifies the habitat substantially (e.g. beaver).
what are the three types of biodiversity?
Habitat biodiversity
Species biodiversity
Genetic biodiversity
what is Habitat biodiversity?
the variety of habitats within an ecosystem (e.g. the presence of sand dunes, woodland, meadows and streams)
what is Species biodiversity?
species richness (how many different species are present in the area) and species evenness (how similar their population sizes are)
what is Genetic biodiversity?
within and between species (e.g. the occurrence of genetically distinct different breeds/varieties within a species and the size the gene pool, which relates to the number of different alleles of genes present).
what is simpsons index, and what does each letter represent?
read this and understand how simpsons index works
what does a high simpsons index value show?
High biodiversity - high species richness and everness
ecosystem is well-balanced and stable
resilient to minor environmental changes or loss of species
what does a low simpsons index value mean?
low biodiversity - low species richness and everness
ecosystem is unbalanced and unstable
it may not be resilient to minor changes in the environment or loss of species - further species loss may occur
what are the three main factors affecting biodiversity?
Human population growth
Agriculture
Climate change
how does Human population growth affect biodiversity?
the human population has risen exponentially since the Industrial Revolution in the nineteen century; humans increasing require land for the building of homes, industrial sites, roads, airports, mines etc. Most of this land obtained for such purposes was previously a natural habitat; species which thrived in that habitat are unlikely to survive in an urban environment.
how does agriculture affect biodiversity?
as the human population grows, we need to use an increasing area of land for food production; typically, the biodiversity of the agricultural land will be hugely reduced compared to the natural habitat that is replaced. An extreme example is monoculture, where one specific genetic variety of one crop species is grown over a large area of land.
how does climate chagne affect biodiversity?
not all climate change is due to human activities, but increased emissions of carbon dioxide and other greenhouse gases are likely to be causing an increase in global temperatures; such changes are likely to cause the modification of the conditions in many habitats and loss of biodiversity is expected.
what are the main three reasons for maintaining biodiversity?
Ecological reasons
Economic reasons
Aesthetic reasons
what are the ecological reasons for maintaining biodiversity?
Given the interdependence of organisms in a food web, the keystone species (whose presence significantly affects all others in the ecosystem, e.g. via its role as top predator or via the modification of the habitat) should be identified and conserved as a priority.
what are the economic reasons for maintaining biodiversity?
Maintaining high biodiversity in agriculture can avoid problems relating to soil mineral depletion (which is associated with continuous monoculture)
It is important to avoid large‐scale deforestation as this leads to soil loss via erosion by wind/water; soil is an important resource in the context of large scale food production and its sustainability into the future
Ecosystems with high biodiversity are appealing to tourists and many countries derive significant economic benefits from ecotourism; also, conservation projects may themselves provide employment
It is desirable to maintain a genetic resource for future selective breeding or genetic engineering projects that may improve domestic animals and crop plants (particularly important in the context of a change climate and the evolution of new pathogens)
Organisms that have not yet been discovered or studied may provide us with important resources in the future, e.g. new materials for manufacturing or new medicines.
what are the aesthetic reasons for maintaining biodiversity?
It is important to protect natural landscapes and their biodiversity as these are considered beautiful and many people experience a better sense of wellbeing (e.g. reduced stress) by spending time in such places.
what does the genetic biodiversity of a population relate to?
how many different alleles of genes are present.
what is an allele?
Alleles are the different versions of a particular gene that arise via random mutation
what is a population with many alleles of their genes mean?
They are genetically biodiverse
They have a great deal of genetic variation
large gene pool
what are the advantages of a population with a large gene pool and biodiversity?
the large amount of genetic variation enables the population to evolve by natural selection should conditions change: the population will be able to adapt, e.g. to new diseases or climate change, rather than become extinct (die out)
what factors increase genetic biodiversity (increase in the
numbers of alleles of genes in the population’s gene pool)?
High rate of random mutation: environmental factors can influence this, e.g. UV light exposure.
Interbreeding between different population groups: this transfers alleles from one population’s gene pool into the other population’s gene pool, via the production of hybrid offspring; this is referred to as gene flow. Reproduction between genetically very different individuals is called outbreeding.
what factors can decrease genetic biodiversity (leads to a decrease in the
numbers of alleles of genes in the population’s gene pool)?
Asexual reproduction - either as a naturally occurring reproductive strategy or via artificial cloning techniques: all offspring produced are genetically identical, so have the same alleles of all genes; a population made up of such individuals has little/no genetic biodiversity.
Natural selection - particularly if selection pressures are strong: alleles corresponding to disadvantageous characteristics are not passed on to offspring and may eventually be lost from the population’s gene pool entirely.
Genetic drift: this is a random change to allele frequencies, that is particularly significant in small, isolated, inbred populations; genetic drift can result in the loss of some alleles from the gene pool, if the few individuals that possessed those alleles did not (by chance) reproduce to pass them on.
Genetic bottleneck: this occurs when a major catastrophe (e.g. a natural disaster,
extensive habitat loss or new disease) wipes out most of a population, leaving a small
number of individuals whose genetic diversity is inevitably much lower than the original
population (since a few individuals can only have a small number of different alleles of
genes in their much reduced gene pool). Even if the population size increases again, the
genetic diversity does not recover.
The founder effect: this occurs when a small number of individuals become separated from the main population, and go on to form a new population elsewhere; these individuals only contain a small selection of alleles from the main population, so the genetic diversity of this group and their future descendants is low.
Artificial selection and selective breeding: humans can direct the evolution of a plant/animal species that we use for food/pets etc, choosing certain individuals from a genetically varied population (based on specific desirable characteristics) and then only allowing these individuals to breed. Alleles that correspond to undesirable traits will not be passed on and may be lost from the gene pool entirely. This phenomenon is seen in pedigree animal breeds and in food crops.
Captive breeding programmes, e.g. in a zoo: only a small number of animals (possessing a limited variety of alleles) are available to breed; if these are closely related individuals and hence genetically similar to one another (i.e. if inbreeding occurs) the loss of genetic diversity may be considerable. A similar phenomenon occurs in rare breeds of domestic animal, where very few individuals remain and so inbreeding is inevitable.
how do we quantify genetic biodiversity?
by calculating the proportion of genes in the genome which occur as more than one variant (allele), i.e. the proportion of gene loci that are polymorphic
what is a locus?
the position of a specific gene on its chromosome
what is the formula for the proportion of polymorphic genes?
Describe capture-mark-recapture
This technique is useful because direct counting of each member of the population may be impossible, as animals move around so much and because it can be difficult to be certain that an individual is not counted twice (or not at all).
The technique involves catching as many individuals as possible (e.g. using pitfall traps), counting them, and then marking them (in such a way that does not affect their chance of survival). These marked individuals are released and left long enough to mix back into the population.
Another sample is then collected later, and the numbers of marked and of unmarked individuals are counted.
Dividing the number of marked individuals in the second sample by the total number in the second sample gives you the proportion of the population that you caught in the first sample; from this you can estimate how big the original population was
how does a point quadrat work?
these are metal/wooden strips with 10 pins, evenly spaced, which can be placed randomly in a uniform habitat or systematically along a transect that crosses a changing habitat.
Once a point quadrat has been placed, the species that each of the ten pins touches is identified, e.g. using a key. The relative abundance of each species is assessed bycalculating the proportion of pins that touch each species. For example, if 4 of the 10 pins touch dandelion leaves, this indicates 40% cover with dandelions.
Point quadrats are often quicker to use in sampling compared to frame quadrats, are regarded as giving more accurate percentage cover estimations, and make it less likely that inconspicuous species are entirely missed.
