Classification and evolution

• What is a gene?

  Short sequence of DNA containing the information for the primary

  structure of a protein
• What is an allele?

  A version of a gene
• What causes large genetic diversity in a population?

  • The greater number of different alleles present in a population

  • The greater variety in DNA between members of the same

  population

  • Increases the chance of the population surviving sudden

  changes in the environment, i.e., disease, climate change etc.
• What 4 factors increase genetic diversity?

  Mutations – spontaneous changes in DNA base sequences

  creates new alleles. Some of these can be advantageous,

  others neutral and some may be harmful.

  
  

  Meiosis – creates different combinations of alleles in the

  gametes produced via crossing over and independent

  segregation of homologous chromosomes.

  
  

  Random fertilization of gametes – Any one gamete can be

  fertilized by another and this is governed by chance.

  
  

  Migration/gene flow - Different alleles being introduced into

  a population when individuals from different populations

  migrate and reproduce.
• Definition of natural selection:

  A change in the frequency of particular genotypes and

  phenotypes in a population, resulting in a change in the proportion of alleles.
• Describe the process of natural selection:

  There is competition within a population for food, light, mates etc

  There is variation within a population due to mutations

  Those individuals with alleles that are not advantageous with a given

  selection pressure will die.

  Those individuals with alleles that are advantageous with a given

  selection pressure, survive and reproduce.

  The advantageous alleles are passed onto the offspring.

  The frequency of the advantageous alleles increases in the population.
• What is a selection pressure?

  A selection pressure is a factor which causes selection within a population by exerting environmental resistance.

  Examples of selection pressure include:

   Intra and inter species competition for food, territory and a mate

   Predation

   Limited light , oxygen and water

   Variation in temperature

   Disease

   Human influence e.g. through the use of antibiotics and pesticides, e.g.

  warfarin
• What are anatomical adaptations?

  Structural features of an organism’s body that increases survival

  Example : Otters are streamlined- easier to glide through the

  water and catch food or escape predators.
• What are behavioural adaptations?

  How an organism acts to increase the chance of survival

  Example: Mating rituals increase chance of attracting a member of the same species- increases likelihood of successful mating
• What are physiological adaptations?

  Processes inside the body that increase chance of survival

  Example: Bacteria produce antibiotics- these kill other bacteria- less competition, they are more likely to survive.
• What is directional selection?

  If the environment changes, individuals at one extreme may have an advantage due to advantageous alleles. Over time, selection causes one extreme to be favoured for, causing a shift in the mean and range of values - increase in the frequency of advantageous alleles in the population

  
• What is stabilising selection?

  In a stable environment, selection operates against 2 extremes, to make the population more uniform - environmental stressors tend to weed out unsuitable phenotypes.

  E.g selection against very low birth weight, as they would be less likely to survive, and very high birth weight, as this makes it harder for the mother to deliver the baby

  
• What is disruptive selection?

  When both extremes are favoured for, causing 2 peaks in the distribution, and can lead to 2 new species. The intermediate peak is favoured against, causing it to be less common in the population.

  This can happen due to camouflage - Coloration that allows an organism to match its background and therefore become less vulnerable to predation or recognition by prey.

  e.g light and darkly coloured organisms are favoured for, while intermediate coloured organisms are favoured against.

  
• Definition of a species:

  A species is a group of similar organisms with that can interbreed to

  produce fertile offspring.
• Why are hybrid species infertile?

  Hybrids will inherit a different number of chromosomes from each parent so have an uneven number of chromosomes

  Which cannot form homologous pairs during meiosis;

  Gametes cannot be produced.
• The importance of courtship behaviour:

  Recognition of members of own species, as this produces fertile offspring

  Identify a mate that is capable of breeding - both members should be sexually mature, fertile and receptive to mating.

  Form a pair bond for successful mating, and raising offspring

  Synchronise mating so that it takes place when there is maximum probability of sperm and egg meeting

  Being able to breed, by stimulating release of gametes
• What is the courtship behaviour shown if the two organisms are distantly related?

  Very few elements of courtship behaviour in common

  Addition or deletion of elements of courtship

  Unable to recognise mate as members of different species

  No successful interbreeding

  Production of infertile offspring/hybrids
• What is the courtship behaviour of two closely related organisms?

  Many elements of courtship behaviour in common

  Recognition of mate of same species

  Successful/synchronised interbreeding

  Production of fertile offspring
• What is classification?

  Putting living organisms, into groups within groups which are non - overlapping.
• Why do we classify organisms?

  To catalogue all living things and give a complete picture of evolution as possible.
• What is taxonomy?

  Taxonomy is hierarchical, larger groups are divided into smaller non –

  overlapping groups of organisms with more particular features in

  common.
• What is the hierarchical order of taxonomy?

  A hierarchy is a layered system. There are 8 groups, the system moves from the general (domain) to the most specific (species).

  As you move down the hierarchy, there are more groups at each level but fewer organisms in each group.

  Taxonomic Rank:

  DOMAIN

  KINGDOM

  PHYLUM

  CLASS

  ORDER

  FAMILY

  GENUS

  SPECIES
• How do we name organisms?

  Using the binomial naming system - The first part is the GENUS to which the organism belongs, and the second part is the SPECIES to which it belongs
• What are the 5 kingdoms?

  Prokaryotae (bacteria)

  Protoctista (the unicellular eukaryotes)

  Fungi (eg. Yeats, mould and mushrooms)

  Plantae (the plants)

  Animalia (the animals)