Genetic diversity, adaptations and biodiversity

• Genetic diversity is the number of different alleles in a population of species.
• Allele frequency is the number of times an allele occurs within the gene pool.
• Variation is the existence of variety and differences within and between species.

  On the surface organisms may look identical but on closer inspection it shows that a great deal of variation in their genetics, behaviour and lifestyles.
• Increasing genetic diversity:

  The more alleles in a population, the greater the genetic diversity. This is increased by mutations and migrations into a population.

  Genetic diversity is the basis of natural selection.
• Two ways too decrease genetic diversity:

  Population bottlenecks

  Founder effect
• Population bottlenecks:

  Ecological events may reduce population sizes dramatically e.g earthquakes, floods, fires.

  Disasters that are unselective

  Small surviving populations are unlikely to be representative of the original population.

  By chance alleles may be overrepresented among survivors and some may be eliminated completely.

  E.G. north elephant seals, cheetahs.
• Founder effect:

  Occasionally a small group of individuals may migrate away or become isolated from a population.

  The 'founding' population is only made up of a small number of individuals, inbreeding may be a problem if individuals are closely related.

  It may have a non representing sample of alleles from the parent population.

  The colonizing population may evolve quite differently from the original population, especially if the environment is different.

  Certain alleles may go missing all together as a consequence, resulting in a loss of genetic diversity. E.G the Amish people and the fugates.
• Similarities between founder and bottlenecks:

  Usually a small population which causes a decrease in gene diversity.

  Both are not representative of original group

  Both can cause genes to be eliminated completely.

  Both can cause mutations.

  Genes can be over represented.
• Differences in founder and bottlenecks:

  Bottlenecks are caused by natural disasters.

  Founder effects happen more in humans than animals, vice versa.

  Founder effect has a colonizing group.

  In bottlenecks individuals are ecologically separated.
• Natural selection:

  1. Within a population, a characteristics has more than one phenotype. These phenotypes result from genetic variation in the genotypes controlling this characteristic.
  2. There is different reproductive success between different phenotypes.
  3. Organisms with a greater reproductive success leave more offspring than those with less reproductive success.
  4. Organisms with greater reproductive success will pass their favourable alleles to their offspring. As a result, the frequency of this allele will increase in the population, i.e natural selection has occured.
• Selections the process by which organisms that are better adapted to their environment survive and reproduce.

  Depending on which characteristics are favored selection can produce different results.
• Directional selection:

  Usually a change in environmental conditions.

  Individuals with an extreme type of characteristic are more likely to survive and reproduce.

  Parent population is exposed to condition which can change the allele.

  Allele is reproduced and inherited to child. Directional selection acts against one of the extremes in a range of phenotypes. As a result one phenotype becomes rare and an alternative becomes common.
• Natural selection has caused a genetic change in a population favouring organisms with a characteristic towards the upper range of the frequency distribution.
• Stabilizing selection acts against both extremes in a range of phenotypes. As a result the variation about the mode is reduced

  After selection the mode is in the same place. This is the most advantageous phenotype. Stabilizing selection has reduced variation about this model value.
• The effects of natural selection:

  Results in better adapted species:

  Anatomical- physical changes in body e.g. height

  Physiological- changes in how their body works e.g metabolic rate change

  Behavioural- changes in behavior and actions e.g migration
• The need to classify:

  Sorting living things into groups is called taxonomy

  2 types of classification:

  Artificial and natural
• Classification is the organisation of living things into groups according to their similarities.
• Artificial- based on a few easily observed features e.g all animals that fly in one group
• Natural- based on natural relationships. These days they reflect phylogenetic relationships (historical revolutionary relationships) so animals in there groups might not looks at this alone but something in their underlying anatomy/DNA will be similar.
• Hierarchal system-

  Organises living things into larger groups then smaller ones.
• Carl Linnaeus created the classification system we use today; he organises all living things into 7 groups called a taxa:

  1. Domain
  2. Kingdom
  3. Phylom
  4. Class
  5. Order
  6. Family
  7. Genus
  8. Species
• Binomial system:

  Universal system of naming things, gives each organism 2 names. Genus name and species name.

  Genus name comes first and has capital letters, species name is second and starts with a lowercase letter written in italics or underlined.
• Comparative anatomy:

  Company visible structures

  Structures from different species have same underlying structures.

  These are called homologous structures e.g pentadactyl limb.

  It is argued that such similarities would not exist if these structures had arisen a new in each species.

  They are a variation on one structure that was present in their common ancestors.
• Comparing proteins:

  Specific base sequences in DNA code for specific proteins.

  Therefore if you look at specific proteins that are found all organisms, the degree of similarity between them can tell you how closely related the species are.

  2 such proteins: haemoglobin and cytochromes.
• Immunological comparison of proteins

  1. Comparing blood proteins of different species

  2. Isolating human blood serum (plasma with the clotting protein removed)

  3. Injecting human blood serum into a rabbit

  4. Rabbit producing anti human antibodies

  5. Adding a sample of the rabbit serum to a sample of human serum

  6. Precipitate forming due to antigen antibody complex

  7. Adding samples of rabbit serum to serum containing blood proteins from other mammals

  8. Comparing the degree of precipitation to that caused by human serum

  9. If degree of precipitation is similar to human serum, they are closely related
• Need for courtship:

  Reproduction to ensure survival of a species

  Identify members of the same species

  Former partnership that will result in the production of offspring

  Synchronise mating to increase the chances of gamit successfully fertilizing
• Courtship sequences are the patterns or behaviours of the species

  Used to communicate with other members of the species

  The males usually gives signal
• Courtship behaviors:

  Pheromones- releasing chemicals signals e.g male bumblebee

  Sound- e.g mildew Roars to attract female

  Visual displays- e.g male peacocks display tail feathers

  The longer the ritual the more likely meeting will take place

  Usually it's the males who give the signal and wait for the female to share interest
• Biodiversity is a measure of how varied an ecosystem, is it can be measured in terms of genes species or habitats
• Genetic diversity is a measure of how many variations there are in a genetic code between individuals of a particular species are between different species
• Species diversity is a measure of how many different species there are present in an area and how many individuals of these species there are
• Habitat diversity is a measure of how many different habitats are present in an area
• Species richness is the number of species in a habitat compared to the number of individuals of each species
• Biodiversity hotspots are regions of the world that have a particularly high level of biodiversity bar threatened with destruction
• Low biodiversity isn't a bad thing if it is naturally like that EG arctic and Antarctic

  What's more important is the loss of biodiversity, an ecosystem relies on the interdependence of organisms to maintain stability, and a loss of species can cause serious, unpredictable and possibly irreversible changes.

  Ecosystem distruption can ultimately have a significant impact on humans.
• Hedgerows are home to several habitats and support many different types of insects, birds, small mammals, plants and flowers.

  Destruction of hedgerows to increase the production of arable land can lead to a decline in these organisms.

  Without these, food chains can fall apart and diseases will spread faster crops can become more susceptible to pests.
• Selective breeding:

  Create crops with desirable characteristics and which are very similar

  Individual plants therefore have similar growth patterns leading to higher yields and less wastage

  However the lack of genetic diversity can make the crops as a whole highly susceptible to pests and diseases.

  Growing one species/selective breeding is called monoculture.
• We measured by diversity to enable comparisons to be made:

  Between different areas e g comparing one section of woodlands biodiversity with a similar type of woodland in another geographical area to see the difference.

  In the same area at different times
• Species eveness:

  This is a comparison of the size of the population of different species within a particular area.

  Second component of species diversity

  Species diversity within an area increases as both species richness and species eveness increases
• Haemoglobin: good for comparison because the human beta chain consists of 146 amino acids. This means you can see the similarity in base sequences between humans and animals which are closely related.