variation

Differences shown by organisms within the same species

Types of variations

• Continuous

  • Results in different categories hence different phenotypes

  • Can be represented in the form of a histogram

• Discontinuous

  • Determined by only genes

    • Physical factors have no role

  • Few categories are possible

    • No intermediates

  • Represented with bar graph

    • Fewer variables

• The differences are caused by the environment/physical factors and genes

  • e.g. height of students in a school

  • Body mass/ arm span width

Variation can lead to the origin or formation of a new species

Variation can lead to the evolution of a new organism or species

Mutations can also lead to the origin of a new organism

Mutations are sudden or spontaneous changes happening to the genetic makeup of an organisms

Causes of mutation

• Radiation exposure

• Chemical exposure

• Viruses

• Errors in DNA replication

• Environmental factors

Types of mutation

• Genetic mutation

• Chromosomal mutation

• Haemoglobin

  • Red colour  pigment

• 4 polypeptide chains

• Change occurs on one polypeptide

  • CTT --> CAT

  • GAA - GUA

Meiosis

Random fertilisation

Random mating

Adaptive features

• An inherited feature that helps you to survive and reproduce

• Plants

  • Think of the stomata and the different conditions it works with

    • Xerophytes

      • Adapted to live in very dry conditions

      • They close their stomata

      • Decrease the number of stomata

      • Roots go deeper or wider in the land to find water

      • Smaller leaves

      • Waxy cuticle

        • Hydrophobic

        • Reduce transpiration

      • Hairy leaves

        • Trap any water that leaves the plant to not lose too much

      • Sunken stomata

        • Longer distance, less transpiration

    • Hydrophytes

      • Stomata on top surface

      • Air sacks

Natural selection

• Process by which organisms better adapted to their environment tend to survive and produce more offspring

• Plat B dies when temperature rises

Variation

Overproduction

Best adaptive individuals are more likely to survive and reproduce

Alleles that are more advantageous get passed on

Selection [survival of the fittest]

• Natural

  • Genetic variation within a population

    • Continuing the way of meiosis and random mating

  • The more variety, the better

  • Produces many offspring

  • Brings about the struggle of existence including competition for resources

  • A greater chance of reproduction by individuals who are better adapted to the environment

    • i.e. those with suitable alleles

  • These individuals will pass the suitable alleles to offspring

  • Antibiotic resistance

    • Antibiotics are drugs that destroy bacteria

    • At times the bacteria can become resistance

      • They do not positively react to antibiotics

• Artificial  [selective breeding]

  • In SB the farmer chooses the advantageous alleles and causes them to breed together, in order for the offspring to exhibit/have the advantageous characteristics

  • In crops, e.g. of good traits are

    • Drought resistance

    • Pest resistance

    • Traits that encourage good growth

      • Many chloroplasts

      • Large, juicy fruits

    • Better, good aesthetics

  • In animals e.g. good traits are:

    • High yield of milk

    • Quality of good meat

    • Chickens laying eggs

  • Mechanisms/steps included

    • Choose parents with desired characteristics

    • Breed the gametes of the parents

      • Gametes carry the good alleles

    • Breed the offspring now carrying the desired traits

    • Continue this process over many generations

      • Same as natural selection

        • For the desired trait it must happen over and over again

Selection pressures

• Predation

• Disease

• Food

• Habitat includes all the above

Gene pool

• Sum of all alleles present in an ecosystem or community or niche