IBDP Biology: Genetic Diversity

• When it comes to IBDP Biology, genetic diversity refers to the total number of genetic characteristics in the genetic makeup of a species.
• It refers to any variation in the nucleotides, genes, chromosomes, or whole genomes of organisms.
• It is caused by differences in the sequences of nucleotides that form the DNA.
• This sequence of nucleotides that provides the genetic code within a gene.
• Within a species, there may be different nucleotide sequences for the same gene.
• Different versions of a gene are alleles.
• Most organisms are diploid, having two sets of chromosomes, and therefore two alleles of each gene.
• These differences occur through mutation during DNA replication.
• Within any single organism, there may be variation between the two different alleles for each gene.
• During sexual reproduction, offspring inherit alleles from both parents and these alleles might be slightly different.
• Each allele codes for the production of amino acids that string together to form proteins.
• Thus differences in the nucleotide sequences of alleles result in the production of slightly different forms of the proteins.
• These proteins code for the development of the anatomical, physiological and behavioural characteristics of the organism.
• Therefore, species show variation, partly as a consequence of genetic diversity.

• When it comes to IBDP Biology, genetic diversity plays a huge role in the survival and adaptability of a species.
• When a species’ environment changes, slight gene variations are necessary for it to adapt and survive.
• Some alleles can confer a selective advantage on the host organism, such that it is more likely to survive than if it did not have the particular alleles.
• A species that has a large degree of genetic diversity among its individuals will have more variations from which to choose the most fitting allele.
• Large populations will usually have a greater diversity of alleles compared to small populations.
• Species that have very little genetic variation are at a great risk, healthy reproduction becomes increasingly difficult, and inbreeding may occur.

• Artificial selection is the intentional breeding for certain traits, or combinations of traits, over others.
• Selective breeding in domesticated animals results in the development of a cultivated breed over time.
• Selective breeding involves:
  • Isolation
    • There must be a period in which the members of the group are fixed, so that no new genetic material comes in.
  • Artificial selection
    • Breeders must prevent random mating from coming about.
    • They limit mating to those individuals who exhibit desired characteristics.
  • Inbreeding
    • Mating closely related individuals to facilitate the elimination of undesired characteristics and the fixation of desired traits.

• When it comes to IBDP Biology, selective reduces genetic diversity.
• This makes the population susceptible to widespread disease.
• Bacteria and viruses mutate frequently.
• When a disease causing bacteria changes to attack a specific genetic variation, it can easily wipe out vast quantities of the species.
• Example: Potato Famine in Ireland
  • Since new potato plants are reproduced asexually no genetic diversity is developed.
  • The entire crop is essentially a clone of one potato.
  • In the 1840s, they planted a variety of potato that was susceptible to a rot-causing mold.
  • This mold destroyed the vast majority of the potato crop, and left thousands of people to starve to death.

• Fertilization is not always guaranteed.
• It may be difficult to get individuals to breed.
• Artificial insemination is often used.
• Animals often have a lower standard of living to enable selective breeding to become more efficient.
• Inbreeding can lead to an increased frequency of undesired, recessive alleles.
• They can give rise to unwanted abnormalities.
• Certain alleles may become less frequent, or even become lost from the population.
• These cannot be recreated, and they may be essential for a species to survive a future change in their environment.
• Certain desirable traits may affect other traits.
• A species has a certain number of genes.
• These genes are often used in the development of many different characteristics.
• In certain gene combinations, an allele may cause anatomical or physiological problems.

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