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Biodiversity - Species and taxonomy.
Terms in this set (28)
Members of a single species are capable of breeding to produce living, fertile offspring.
Organisms are identified by two names and hence the system is called the binomial system. What are the features of the binomial system?
- The first name, called the generic name, denotes the genus to which the organism belongs. This is the equivalent to the surname used to identify people and shared by their close relatives.
- The second name, called the specific name, denotes the species to which the organism belongs. This is the equivalent to the first name used to identify people. However, unlike in humans, it is never shared by other species within the genus.
What is courtship behaviour?
Members of the same species have similar, or have the same genes and therefore resemble one another physically and biochemically. This helps them distinguish members of their own species from those of other species. The behaviour of members of the same species is more alike than that of members of different species. Individuals can therefore recognise members of their own species by the way they act.
- Like the physical and biochemical features of a species, the ability to display a behaviour is genetically determined. It too has evolved and influenced the chances of survival.
- When it comes to the survival of the species, courtship and mating are essential.
It is important to ensure that mating is successful and that the offspring have the maximum chance of survival. How does courtship behaviour help to achieve this?
It enables individuals to ...
1) Recognise members of their own species to ensure mating only takes place between members of the same species because only members of the same species can produce fertile offspring.
2) Identify a mate that is capable of breeding because both partners need to be sexually mature, fertile and receptive to mating.
3) Form a pair bond that will lead to successful mating and raising of offspring.
4) Synchronise mating so that it takes place when there is the maximum probability of the sperm and egg meeting.
5) Become able to breed by bringing a member of the opposite sex into a physiological state that allows breeding to occur.
What is Phylogenetic classification?
- Is based upon the evolutionary relationships between organisms and their ancestors.
- Classifies species into groups using shared features derived from their ancestors.
- Arranges the groups into a hierarchy, in which the groups are contained within larger composite groups with no overlap.
What are the ranks of classification?
Domain, kingdom, phylum, class, order, family, genus and species.
What is Phylogeny?
The hierarchical order of taxonomic ranks is based upon the supposed evolutionary line of decent of the group members. This evolutionary relationship is known as the phylogeny.
What do phylogenetic trees show?
The closer the branches, the closer the evolutionary relationships.
Define species diversity.
Species diversity refers to the number of different species and the number of individuals of each species within any one community.
Define genetic diversity.
Genetic diversity refers to the variety of genes possessed by the individuals that make up a population of a species.
Define ecosystem diversity.
Ecosystem diversity refers to the range of different habitats, from a small local habitat to the whole of the Earth.
One measure of species diversity is ...
Define species richness.
This is the number of different species in a particular area at a given time (community).
- Two communities may have the same number of species but the proportionals of the community made up of each species may differ.
One way of measuring species diversity is to use ...
An index of diversity.
In our efforts to provide enough food for the human population at a low cost, mankind has had a considerable impact on the natural world. What has this impact resulted in?
This impact has led to a reduction in biodiversity. Agriculture reduces species diversity and therefore there needs to be a balance between conservation and farming.
What is the impact of agriculture?
- As natural ecosystems develop over time, they become complex communities with many individuals of a large number of different species. These communities have a high index of diversity.
- Agricultural ecosystems are controlled by humans and are different. Farmers often select species for particular qualities that make them more productive. As a result the number of species, and the genetic variety of alleles they possess, is reduced to the few that exhibit the desired features.
Why are pesticides used?
Pesticides are used to exclude other species that compete for the light, mineral ions, water and food required by the famed species. The overall effect is a reduction in species diversity. The index of species diversity is therefore low in agricultural ecosystems.
Investigating diversity. How are evolutionary relationships determined by scientists?
- Classification systems were originally based on features that could easily be observed. As science has developed it has become possible to use a wider range of evidence to determine the evolutionary relationships between organisms.
- When organisms evolve it is not only their visible internal and external features that change, but also the molecules of which they are made.
- DNA determines the proteins of an organism, including enzymes and proteins determine the features of an organism.
Comparing the genetic diversity within, and between, species helps scientists to determine the evolutionary relationships between them. What are the different way that these comparisons can be made?
1) Comparison of observable characteristics.
2) Comparison of DNA base sequences.
3) Comparison of the base sequence of mRNA.
4) Comparison of amino acid sequence in proteins.
Describe how observing characteristics can be used.
Genetic diversity was measured by observing the characteristics of organisms. This method is based on the fact that each observable characteristic is determined by a gene or genes with environmental influences. The variety within a characteristic depends on the number and variety of alleles of that gene.
What are the limitations of using observable characteristics?
- A large number of observable characteristics are coded for by more than one gene. They are polygenic.
- They are not discrete from one another.
- It is often difficult to distinguish one from another.
- Characteristics can also be modified by the environment. Differences may therefore be the result of different environmental conditions rather than different alleles.
- Inferring DNA differences from observable characteristics has been replaced by directly observing DNA sequences themselves through gene technology.
Describe how DNA base sequences can be compared.
The exact order of nucleotides on DNA can be determined.
When one species gives rise to another species during evolution, the DNA of the new species will initially be very similar to that of the species that gave rise to it.
Due to mutations, the sequences of nucleotide bases in the DNA of the new species will change.
Over time, the new species will accumulate more and more differences in its DNA.
- We would expect species that are more closely related to show more similarity in their DNA base sequences than species that are more distantly related.
Describe how the base sequence of mRNA can be compared.
mRNA is coded for by DNA. The base sequences on mRNA are complementary to those on the strand of DNA from which they are made.
We can measure DNA diversity, and therefore genetic diversity, by comparing the base sequence of mRNA.
Describe how amino acid sequences in proteins can be compared.
The sequence of amino acids in proteins is determined by mRNA which is determined by DNA.
Genetic diversity within and between species can therefore be measured by comparing the amino acid sequences of their proteins.
- The degree of similarity in the amino acid sequence of the same protein in two species will also reflect how closely related the two species are.
- Once the amino acid sequence for a chosen protein has been determined for two species, the two sequences are compared.
- This can be done by counting either the number of similarities or the number of differences in each sequence.
How can variation be investigated?
Sampling involves taking measurements of individuals, selected from the population of organisms which is being investigated.
In theory, if these individuals are representative of the population as a whole, then the measurements can be relied upon.
Why could the measurements not be representative?
- Sampling bias.
The selection process may be biased.
Even if sampling bias is avoided, the individuals chosen may, by pure chance, not be representative.
The best way to prevent sampling bias is to eliminate, as far as possible, any human involvement in choosing the samples. This can be achieved by carrying out random sampling. One method is ...
1) Divide the study area into a grid of numbered lines, for example by stretching two long tape measures at right angles to each other.
2) Using random numbers, from a table or generated by a computer, obtain a series of coordinates.
3) Take samples at the intersection of each pair of coordinates.
We cannot completely remove chance from the sampling process but we can minimise its effect by ...
1) Using a large sample size.
The more individuals that are selected the smaller the probability that chance will influence the result and the less influence anomalies will have. The greater the sample size the more reliable the data will be.
2) Analysis of the data collected.
Accepting that chance will play a part, the data collected can be analysed using statistical tests to determine the extent to which chance may have influenced the data.
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