Diversity & variation

• what is a gene mutation?

  a change in the base sequence of DNA occuring during DNA replication.
• whats is a mutagenic agent?

  A mutagenic agent is a substance or factor that causes genetic mutations.
• whats an example of a mutagenic agent?

  UV light, radiation, chemicals / carcinogens, smoking
• what is a chromosome mutation?

  changes in the number of chromosomes can arise randomly due to non-disjunction during meiosis.
• what is non-disjunction?

  when chromosomes or chromatids do not split equally during anaphase.
• what is polyploidy?

  changes in whole sets of chromosomes
• what is aneuploidy?

  changes in the number of individual chromosomes
• whats an example of polyploidy?

  when organisms have three or more sets of chromosomes rather than the usual two.
• human gametes are haploid
• human somatic cells are diploid
• whats an example of aneuploidy?

  individual homologous pairs of chromosomes fail to separate in meiosis, resulting in gametes with one more or less chromosomes.
• whats the definition of meiosis ?

  meiosis involved 2 nuclear divisions & produced 4 genetically different haploid daughter cells.
• what is independent segregation?

  when homologous pairs of chromosomes line up opposite each other at the equator of the cell.

  • the pairs are separated so one of each homologous paur end up in the daughter cell.
• what is crossing over?

  parts of chromatids twist around each other.

  • This causes tension & the parts of the chromatids break.
  • Broken parts of the chromatids recombine with another chromatid.
  • This creates new combinations of alleles.
• how many divisions occur in meiosis

  two
• what type of cells are made in meiosis?

  haploid (one set of chromosomes)
• what type of daughter cells does meiosis produce

  4 genetically different daughter cells
• how many divisions occur in mitosis?


  one
• what type of cells are produced by mitosis

  diploid (two sets of chromosomes)
• what type of daughter cells does mitosis produce?

  2 genetically identical daughter cells
• meiosis is when a diploid (2n) goes to haploid (n) cells
• genetic diversity definition?

  the number of different alleles of genes in a population
• whats the definition of evolution?

  the change in allele frequency over many generations in a population
• natural selection definition?

  is the process that leads to evolution in population
• what are the three types of adaptation?

  behavioural

  anatomical

  physiological
• describe the process of natural selection?

  -random mutations create new alleles for a gene.

  • if the new alleles increase chance of survival in that environment, they are more likely to survive & reproduce.
  • this passes on the advantageous allele to the offspring.
  • eventually the allele frequency increases within the population.
• what are the two types of selection?

  directional & stabilising
• what is directional selection?

  the advantageous allele is coding for an extreme trait.

  eg. antibiotic resistance in bacteria
• what is stabilising selection?

  the middle trait is chosen as advantageous
• when does directional selection occur?

  when there is a change in the environment
• when does stabilising selection occur?

  when no change occurs in the environment
• what is a species

  when two organisms can produce fertile offspring
• courtship behaviour is essential for successful mating & species recognition.
• what is courtship behaviour?

  a sequence of actions which is unique to each species.

  • it is how animals identify a member of their own species.
• what is the classification hierarchy?

  Domain

  Kingdom

  Phylum

  Class

  Order

  Family

  Genus

  Species
• what is species richness?

  The number of different species in a given area.
• whats the formula for the diversity index?

  $N(N-1)/n(n-1)$
• what does N stands for ?

  total number of organisms of all species
• whats does n stand for ?

  total number of organisms of a specific species