3.4.5-7

• Species

  A group of organisms that can interbreed to produce fertile offspring
• Suggest why two different species are unable to produce fertile offspring

  ● Different species have different chromosome numbers → offspring may have odd chromosome number

  ● So homologous pairs cannot form → meiosis cannot occur to produce gametes
• classification

  the way in which living organism are divided into groups
• Taxonomy

  Grouping organisms based on shared characteristics
• Plural of taxonomy and singular

  Taxa and taxon
• Hierarchical

  Smaller groups placed within larger ones with no overlap
• Phylogenetic

  Based on evolutionary history it shows evolutionary relationships with organism
• The eight taxonomic ranks

  1. Domain
  2. Kingdom
  3. Phylum (phyla)
  4. Class
  5. Order
  6. Family
  7. Genus (genera )
  8. Species
• Binomial naming system

  Genus and species
• Phylogenetic system

  Species are arranged into groups called taxa based on evolutionary origin and relationships using hierarchy which is smaller groups in larger one with no overlap
• Advantage of binomial naming system

  Universal so no confusion as many organisms have more than one common name.
• How can phylogenetic trees be interpreted

  Branch point = common ancestor

  ● Branch = evolutionary path

  ● If two species have a more recent common

  ancestor, they are more closely related (eg. C & D)
• Courtship behaviour

  Innate so is genetically determined as members of the same species are genetically programmed to show the same courtship behaviour
• Exp why courtship behaviour is necessary to succeed mating

  1. Species recognition - identify if organism from same species as you
  2. Stimulates release of gametes
  3. Indicates sexual maturity and fertility
  4. Allows recognition of the opposite sex
  5. Establishes a pair bond to raise young increasing survival chance
• Describe two advances that have helped to clarify evolutionary

  relationships between organism

  1. Genome sequencing ( comparing dna and mrna base sequence )
  2. Immunology
• Why is comparing mRNA not as good

  It doesn’t have introns so less nucleotides to compare
• Why is comparing amino acid sequence not good enough

  Genetic codes degenerate several triplets code for the same amino acid
• What does more different base sequence suggest

  More distantly related / earlier common ancestor as mutations build up overtime
• Best phrase

  More recent common ancestor

  More distant / less recent common ancestor
• What does immunology mean

  Antibody extracted from one species and complimentary protein from another organism added if a higher amount of antibody’s bind it means species are more closely related indicating similar amino acid sequence
• biodiversity

  The variety of living organisms in a community. It can relate to a range of habitats from a small local habitat to the Earth.
• Population

  All the organisms of a particular species in an area community habitat
• Habitat

  Place where organisms live
• Community

  All the populations of different species in a habitat
• Interspecific variation

  Differences between members of different species
• Intraspecific variation

  Differences between members of the same species
• Species richness

  Measure of different species in a community habitat ecosystem
• Species diversity

  The number of different species and the number of individuals of each species within the community
• Species diversity index

  N(N-1) / sum of n(n-1)

  N is the total number of organism across all species

  n total number of organism of a particular species
• Little n is

  Little little steps many processes
• high biodiversity

  higher number of different species (greater species richness ) and a higher number of individuals within each species
• What does an index of diversity do?

  Describes the relationship between:

  1. The number of species in a community (species richness)The
  2. number of individuals in each species (population size)
• Suggest why index of diversity is more useful than species richness

  ● Also takes into account number of individuals in each species

  ● So takes into account that some species may be present in small or high numbers
• Describe how index of diversity values can be interpreted

  ● High → many species present (high species richness) and species evenly represented

  ● Low → habitat dominated by one / a few species
• Low value of diversity indicates

  Unfavourable harsh environ ment

  • Few species present and often populations are small
  • generally abiotic factors determining which species are present
  • Unstable ecosystems
  • Few species are adapted to survive in the harsh condtions
• High value index diversity

  1. Favourable environment
  2. Many species are present and populations are usually large
  3. if there’s a high diversity of plants and trees there’ll be a high diversity of insects, animals and birds as there’s more habitats and food sources
  4. This is because there’s more variety of plants and trees so herbivores will colonise the area and carnivores will follow
• Explain how some farming techniques reduce biodiversity

  • Removal of woodlands and hedgerows
  • Draining marshy land
  • Monoculture (1plant)
  • Use of herbicides to kill weeds
  • Pesticides to kill pests reducing diversity of insects 


  ● Reduces variety of plants

  ● So fewer habitats and niches

  ● And less variety of food sources
• Explain the balance between conservation and farming

  ● Conservation required to increase biodiversity

  ● But when implemented on farms, yields can be reduced, reducing profit / income for farmers

  ○ Eg. by reducing land area for crop growth, increasing competition, increasing pest population

  ● To offset loss, financial incentives / grants are offered
• How can genetic diversity within or between species be measured?

  ● Comparing frequency of measurable or observable characteristics

  ● Comparing base sequence of DNA

  ● Comparing base sequence of mRNA

  ● Comparing amino acid sequence of a specific protein encoded by DNA and mRNA
• Explain how comparing DNA, mRNA and amino acid sequences can indicate

  relationships between organisms within a species and between species

  ● More differences in sequences → more distantly related / earlier common ancestor

  ● As mutations (change in DNA base sequences) build up over time

  ● More mutations cause more changes in amino acid sequences