Nature of Biological Variation

• what are the two types of evolution?

  macroevolution and microevolution
• what is macroevolution?

  large-scale, non directional, evolutionary changes that occur over long periods of time.
• give two examples of macroevolution?

  the origin of new taxonomic groups and mass extinctions
• what is microevolution?

  when a population progressively adapts to its environment - this change is much more rapid and within species
• what is an example of microevolution?

  natural selection
• what makes natural selection possible?

  genetic inheritance
• what is genetic inheritance the interaction between?

  environment, phenotype and genotype
• what are chromosomes?

  gene carrying structures found in the nucleus of every cell in the body
• how many pairs of chromosomes do humans have?

  23
• are the X and Y chromosomes homologous?

  no
• what are the five ways in which asexual reproduction can occur by?

  Binary fission, budding, mitosis, parthenogenesis, and vegetative propagation.
• when does parthenogenesis occur?

  when there are no males around
• two examples of animals which use parthenogenesis?

  frogs and spiders
• what process does sexual reproduction occur by?

  meiosis
• which type of reproduction results in the most genetic variation?

  sexual
• which type of reproduction results in the least genetic variation?

  asexual
• what is the driving factor in variation?

  meiosis
• name three ways in which variation can occur during meiosis?

  independent assortment, crossing over and random fertilisation
• what are the four types of mutuations?

  deletion, duplication, inversion and reciprocal translocation
• what is an inversion mutation?

  when a section of DNA is translated backwards
• what is a duplication mutation?

  when a nucleotide is added twice
• what is a deletion mutation?

  when a nucleotide is missing
• what is a reciprocal translocation mutation?

  two pieces of DNA are replicated at the same time too close together so they end up going into eachothers DNA polymerase chain, meaning sections of DNA are copied into the other chain
• what level does mutation occur at?

  DNA
• what level does mutation expression occur at?

  chromosome or allele
• what is polyploidy?

  containing more than two complete sets of chromosomes
• what does polyploidy result in?

  reproductive isolation