4.2

• Biodiversity is the variety of living organisms, over time the variety of life on Earth has become more extensive but now it is being threatened by human activity such as deforestation and agriculture as well as climate change.
• Species richness is the number of different species in a community and can be measured by simply counting the number of species present via methods such as random sampling.
• Systematic sampling is a type of sampling where a particular pattern is followed, for instance a sample is taken every few metres.
• Opportunistic sampling is a type of sampling where a sample is taken when a source is encountered therefore it is based on ease of access.
• Stratified sampling is a method of sampling where the population is subdivided into smaller groups known as strata based on common characteristics and subsequently a random sample is taken from each stratum of a size proportional to the proportion of that particular strata in the whole population.
• Species evenness is a comparison of abundance of different species in a habitat.
• Genetic diversity is a measure of the genetic variation found in a particular species, in other words it is the number of alleles in a gene pool.
• Biodiversity can also be measured using the index of diversity (D) which can be calculated as following: D = Diversity index N = total number of organisms n = total number of organisms of each species.
• Maintaining biodiversity is important for ecological, economic and aesthetic reasons such as protecting landscapes.
• There are various methods of conserving biodiversity including in situ methods such as marine conservation zones and wildlife reserves which serve to protect the wildlife.
• Ex situ conservation methods include zoos, seeds banks and botanic gardens.
• Zoos use various methods to conserve endangered species and their genetic diversity, some of the methods used include scientific research, captive breeding programmes, reintroduction programmes and education programmes.
• Seedbanks store a large number of seeds in order to conserve genetic diversity and prevent plant species from going extinct.
• Biodiversity conservation needs international co-operation, there are historic and current agreements, including the Convention on International Trade in Endangered Species ( CITES ), the Rio Convention on Biological Diversity (CBD) and the Countryside Stewardship Scheme (CSS).
• Classification is the process of naming and organising organisms into groups based on their characteristics.
• Organisms can be grouped into one of the five kingdoms: animals, plants, fungi, prokaryotes and protoctists.
• They can then be grouped further into phylum, class, order, family, genus and species.
• Natural selection is the process in which fitter individuals who are better adapted to the environment survive and pass on the advantageous genes to future generations.
• Over time (and many generations), the frequency of alleles in a population changes and this leads to evolution.
• Charles Darwin and many other scientists’ observations have provided evidence for the theory of evolution.
• Comparative anatomy – comparing the anatomy of different organisms by looking at homologous structures (do species share a similar physical structure?).
• Evolution is the process by which the frequency of alleles in a gene pool changes over time as a result of natural selection.
• The analysis of molecular differences in different organisms to determine the extent of their evolutionary relatedness is known as molecular phylogeny.
• Each population shows natural variation in characteristics.
• Discontinuous variation is where there are no intermediates (such as the shape of bacteria as they are spherical, rod shaped, spiral etc)
• The data obtained by molecular phylogeny (looking at DNA sequences, RNA sequences and protein structure) has been accepted by scientists and this gave rise to new taxonomic groupings – all organisms can be separated into one of the three domains: Bacteria, Archaea and Eukaryota.
• An environmental change occurs and as a result of that the selection pressure changes.
• The niche of a species is its role within the environment.
• Physiological adaptations are processes inside an organism’s body that increase its chance of survival e.g regulation of blood flow through the skin.
• Organisms are adapted to their environment in various ways: Anatomical adaptations are physical adaptations, either external or internal e.g presence of loops of Henlé which allow desert mammals to produce concentrated urine and minimise water loss.
• Fossils – looking at the remains of extinct organisms and comparing to those alive today.
• Evolution via natural selection: There’s a variety of phenotypes within a population.
• Molecular biology – looking at the similarities and differences between DNA sequences in different organisms.
• Alfred Wallace had very similar ideas to Darwin and they published their theory together.
• These characteristics tend to be controlled by more than one gene and are often influenced by environmental factors.
• If two populations become reproductively isolated, new species will be formed due to accumulation of different genetic information in populations over time due to different environments and selection pressures.
• Each species is named according to the binomial system, the first part of the name is the genus and the second part of the name is the species.
• Darwin concluded a bird born with a beak more suited to the food available would be more likely to survive than one whose beak was less well suited.
• Species which share the same niche compete with each other and a better adapted species survive.
• Darwin observed many different types of finch on the Galapagos Islands but he believed they must be related due to many similarities.