Topic 7

• Genotype: the genetic constitution of an organism
• Phenotype:

  • the expression of the genetic constitution
  • and its interaction with the environment
• Homozygous: two copies of the same allele for a gene
• Heterozygous: two different alleles for the same gene
• Recessive allele: an allele that is only expressed if there are no dominant alleles present
• Dominant allele: an allele that is always expressed in the phenotype
• Codominance:

  • two alleles that are both dominant
  • both are expressed in the phenotype
• Multiple alleles: more than two alleles for a gene
• Sex-linkage:

  • a gene located on the X chromosome
  • in the non-homologous region
• Autosomal linkage: genes located on the same chromosome (not the X or Y chromosome)

  
• Epistasis: when one gene masks or modifies with the expression of another gene
• Monohybrid: the inheritance of one gene
• Dihybrid: inheritance of two genes
• Natural selection:

  • the process that leads to evolution in populations
  • results in species becoming better adapted to their environment
• Selection pressure:

  • factors that affect the survival of an organism
  • the driving force of natural selection
• Differential reproductive success:

  • not all individuals are equally likely to produce
  • results in changes in allele frequencies within gene pool
• Reproductively isolated:

  • two populations of the same species but they cannot breed together
  • there is no gene flow
• Speciation: the process that results in the creation of new species
• Allopatric speciation:

  • two populations become reproductively isolated due to being geographically isolated
  • results in the formation of two new species

  
• Sympatric speciation:

  • two populations become reproductively isolated whilst in the same location
  • e.g. due to changes in behaviour
  • results in the formation of two new species
• Genetic drift:

  • the change in the allele frequency within a population between generations
  • occurs from one generation to the next
  • substantial genetic drift results in evolution

  
• Population: all individuals of one species in the same area at the same time
• Habitat: the range of physical, biological and environmental factors in which a species can live
• Community: all the species in a particular area at a particular time
• Ecosystem:

  • a community and the non-living components of an area
  • they can range from very small to very large in size
• Niche:

  • an organism's role within an ecosystem
  • their position in the food web
  • and their habitat
• Carrying capacity: the maximum population size an ecosystem can support
• Abiotic factors: non-living conditions of an ecosystem
• Biotic factors: impact and interactions between organisms
• Interspecific competition: competition between members of different species
• Intraspecific competition: competition between members of the same species
• Predator-prey relationship: the interaction between predator and prey and how this affects their population sizes

  
• When would you use random sampling:

  • When there is a uniform distribution of the plant species
  • to avoid bias
• Quadrat

  • a frame
  • gridded or open
  • used to sample non-motile organisms
• What must you do to ensure your samples are representative?

  • Take a large sample (at least 30)
  • randomly sample
• When would you use a line transect?

  • When sampling a non-uniform area
  • e.g. a rocky shore
• Belt transect:

  • one tape measure is placed through an ecosystem that is not uniform
  • the quadrat is placed at every position along a tape measure

  
• Interrupted belt transect:

  
  

  one tape measure is placed through an ecosystem that is not uniform

  the quadrat is placed at set intervals along the tape measure

  
• The 3 measurements you can take when counting plants in a quadrat?

  • density
  • percentage cover
  • frequency
• Density measurement: when you count the individuals present