Conversely, failure to maintain genetic diversity limits the capacity for a population to adapt, making it vulnerable to even small changes in the environment and increasing the likelihood of extinction. Species Diversity is simply the number and relative abundance of species found in a given biological organisation population, ecosystem, Earth. Species are the basic units of biological classification and hence, this is the measure most commonly associated with the term 'biodiversity'.
Worldwide, about 1. However, many environments and groups of organisms are not well studied and estimates of species numbers range from 3 to million. Diversity in species is important for economic, biological, social and cultural reasons. Major threats to species diversity are loss of habitat and fragmentation, over exploitations fishing, hunting, extraction , pollution, the introduction of invasive species e.
In order to conserve species diversity, natural resource management and habitat protection are vital. Ecosystem Diversity can be defined as the variety of different habitats, communities and ecological processes.
But in another form actually involves a larger-scale variation where you might have a stretch of DNA of hundreds, or even thousands, of base pairs that is different between people. Maybe I have three copies of that stretch and you have two. Or maybe it's a circumstance where I have the genes in the order ABC and you have them in the order of ACB because you have an inversion in that. Those don't have to be pathological.
In fact, most of them won't be, but it's a different kind of variation that in some instances may be playing a role in disease risk. Courtship behaviour as a necessary precursor to successful mating.
The role of courtship in species recognition. A phylogenetic classification system attempts to arrange species into groups based on their evolutionary origins and relationships. It uses a hierarchy in which smaller groups are placed within larger groups, with no overlap between groups. Each group is called a taxon plural taxa. One hierarchy comprises the taxa: domain, kingdom, phylum, class, order, family, genus and species.
Each species is universally identified by a binomial consisting of the name of its genus and species, eg, Homo sapiens.
Recall of different taxonomic systems, such as the three domain or five kingdom systems, will not be required. Students should be able to appreciate that advances in immunology and genome sequencing help to clarify evolutionary relationships between organisms. An index of diversity describes the relationship between the number of species in a community and the number of individuals in each species.
Calculation of an index of diversity from the formula. Students could be given data from which to calculate an index of diversity and interpret the significance of the calculated value of the index. Knowledge of gene technologies will not be tested. Quantitative investigations of variation within a species involve:. Students will not be required to calculate standard deviations in written papers. Students could use standard scientific calculators to calculate the mean values of data they have collected or have been given.
Students could calculate, and interpret the values of, the standard deviations of their mean values. AS and A-level Biology , Specification Planning resources Teaching resources Assessment resources Key dates. Subject content. Contents list. Changes for Introduction Specification at a glance Subject content 3. Previous 3. Next 3.
Students should be able to: relate the base sequence of nucleic acids to the amino acid sequence of polypeptides, when provided with suitable data about the genetic code interpret data from experimental work investigating the role of nucleic acids. Meiosis produces daughter cells that are genetically different from each other. The process of meiosis only in sufficient detail to show how: two nuclear divisions result usually in the formation of four haploid daughter cells from a single diploid parent cell genetically different daughter cells result from the independent segregation of homologous chromosomes crossing over between homologous chromosomes results in further genetic variation among daughter cells.
Students should be able to: complete diagrams showing the chromosome content of cells after the first and second meiotic division, when given the chromosome content of the parent cell explain the different outcome of mitosis and meiosis recognise where meiosis occurs when given information about an unfamiliar life cycle explain how random fertilisation of haploid gametes further increases genetic variation within a species.
0コメント