Topic 6 Life On Earth – Past, Present and Future

• How evolution of a species occurs

  1. Random DNA mutation occurs

  2. Advantageous mutations result in increased reproductive success

  3. Advantageous allele is inherited by next generation

  4. Frequency of advantageous allele increases over generations

  5. New gene mutates, process continues
• Selective breeding


  Process of breeding plants and animals to display desirable characteristics
• Species


  Group of similar organisms which can breed together to produce fertile offspring
• Speciation


  1. Population becomes so evolved they can no longer mate with ancestors

  2. More likely to occur if population is isolated
• Evidence for evolution


  • Fossils
  • Selective breeding
  • Differences in isolated populations
  • Similar anatomy
• Modern examples of evolution

  • Antibiotic resistance
  • DNA comparison
• Some people do not accept the theory of evolution due to conflicting religious beliefs or lack of understanding of the evidence
• Asexual reproduction


  Process which results in genetically identical offspring (clones)
• Advantages of asexual reproduction

  • Only one parent required
  • Can reproduce quickly
  • Takes less energy
• Disadvantages of asexual reproduction

  • Lack of diversity
  • Prone to extinction
  • Cannot adapt
  • Overpopulation
• Sexual reproduction


  Requires two parents, each offspring is genetically unique
• Advantages of sexual reproduction

  • Wide diversity
  • Promotes survival
  • Organisms can adapt
• Disadvantages of sexual reproduction

  • Two parents required
  • Fewer offspring produced
• Taxonomy


  Classification of organisms into similar categories
• Organisms were originally classified based on physical or behavioural similarities, which was flawed as many genetically different organisms appeared similar
• Genome sequencing has improved classification by showing evolutionary relationships and when speciation occurred
• Human activities that threaten biodiversity

  • Use of chemicals
  • Urbanisation and industrialisation
  • Introduction of invasive species
• Biodiversity conservation


  Efforts to maintain biodiversity locally and globally, e.g. nature reserves, sustainable farming
• Factors that threaten food security

  • Increasing population
  • Changing diets
  • New pests and pathogens
  • Environmental change
• Sustainable farming practices


  Important to maintain soil fertility and biodiversity
• Methods to increase farming yield

  • Genetic modification
  • Selective breeding
  • Optimum growing conditions
• Allele


  A version of a gene (also known as variant). Each chromosome in a pair carries the same genes, but may have different alleles.
• Antibiotic


  A type of medication that helps cure bacterial disease by killing infective bacteria inside the body.
• Antibiotic resistance


  The ability of a bacteria to become resistant to the treatment that is being used to kill it, i.e. antibiotics. This provides evidence for evolution.
• Asexual reproduction


  • A form of reproduction that only involves a single parent and creates genetically identical offspring.
• Biodiversity


  The combination of the diversity of living organisms, the diversity of genes these organisms have, and the diversity of ecosystems.
• Classification


  The organisation of organisms into groups based on their characteristics and structure.
• Community


  All of the populations of different species that are living in a habitat together.
• Competition


  When different organisms compete for the same resources (e.g. food, shelter and mates) in an ecosystem. It limits population size.
• Ecosystem


  The community of living (biotic) and non-living (abiotic) components of an area and their interactions.
• Eutrophication


  When an aquatic ecosystem (e.g. river) becomes enriched with nutrients, stimulating excessive algae growth.
• Evolution


  A change in the inherited characteristics of a population over time, through the process of natural selection, which may result in the formation of new species.
• Extinction


  The death of all members of a species.
• Fertilisation


  The fusion of male and female gametes to restore the full chromosome number.
• Fossil fuel


  The burning of fossils for energy, which releases carbon dioxide into the air.
• Fossil record


  The remains or impressions of dead organisms found in rocks that are millions of years old. They provide evidence for evolution.
• Gamete


  Sex cells (sperm and egg cells) with half the usual number of chromosomes. They are involved in reproduction.
• Gene


  A section of DNA that codes for a specific amino acid sequence which is polymerised to make a specific protein.
• Genetic modification


  • The alteration of the genetic information of an organism.
• Genetic variation


  The variation in the genes of a species.