Genetic diversity and adaptations

Genetic diversity and adaptations

1. Genetic diversity is the total number of different alleles in a population or species.

   • It can increased by mutations.
     • This is the random change in DNA's genome.
       • This leads to a variety of alleles, giving the organisms different phenotypes.
   • It can also be increased by the introduction of new species into a population e.g. by migration.
     • This will increase the number of different alleles and may influence interbreeding.
       • This further increases the combination of alleles.
   • It can be decreased by a genetic bottleneck, reducing the gene pool.
     • A genetic bottleneck is an event that wipes out a large number of organisms.
       • A gene pool is the complete set of alleles in a population.

2. The founder effect

   • This is when a small part of a population becomes separated and isolated...
     • ... Due to a genetic bottleneck.
   • An isolated population breed to increase population.
     • The genetic diversity is small in this population because there are fewer combinations of alleles.
   • For example, an Amish population is a small group...
     • ... and due to their small allele variation, they have a low genetic diversty.
       • They also seemingly have similar genetic disorders.

3. Types of adaptations

   • Behavioural adaptations
     • This is when it acts in a certain way to adapt to its environment.
       • For example, possums act dead whenever they are being threatened, to avoid becoming prey.
   • Physiological adaptations
     • This is when reactions alter in an organism's body, to make it adapt.
       • For example, bears hibernate during winter, reducing their metabolic rate, so that the lose less energy.
   • Anatomical adaptations
     • This is an organism's structural feature and how they look, to increase chance of survival
       • For example, fish have a very streamlined body with tiny fins which help them swim faster, away from predators.

4. Types of selection

   • Stabilizing selection
     • This is when organisms have characteristics in the middle of the range are more likely to survive
       • E.g. a baby's weight needs to be about average so that it can survive.
   • Directional selection
     • This is when an organism possesses single characteristic of an extreme type to help it survive.
       • E.g. Bacteria which have become resistant to antibiotics.
   • Disruptive selection
     • This is when an organism has characteristics of extreme types, which help it too survive
       • E.g. Birds with large beaks can eat large seeds and birds with small beaks can eat small seeds.
         • Birds with medium-sized beaks cannot eat small nor big...
           • ... So they are doomed!