1. Human Intervention in Evolution

2. Answering exam questions
For each intervention ask yourself:
How does it effect natural selection (are alleles being passed on that normally wouldn’t be? Are new alleles appearing in the population?)?
How does it effect genetic variation (does it increase and therefore increase the chances of survival of a species with new selection pressures, or does it decrease)?

3. Selective Breeding Also called artificial selection
Choosing which organisms breed together based on desirable traits
Decreases genetic diversity (alleles for desired traits increase in frequency and alleles for non-chosen trait decrease in frequency in successive generations)
Shortens time for development of desirable traits within organisms/species
Maintains alleles (traits) in a gene pool that might not usually be retained (don’t contribute to survival or reproduction)

4. Examples of features maintained only by artificial selection can be seen in domesticated animals, such as:
Jacobin pigeons, whose distinctive arrangement of neck feathers forms a ruff that masks their faces, except from immediately in front
hairless cats and dogs
English bulldogs, whose greatly shortened muzzles result in breathing problems

7. May lead to new species….

9. Artificial Insemination
Artificially introducing gametes from a male with desired traits, into a female with desired traits
Semen collected from male and injected into female reproductive tract
Inserting sperm into a cow

10. Multiple Ovulation
Administering hormones to mammals so they release multiple, mature ovaries instead of only 1 each cycle
These eggs can be removed and fertilized, then the embryos inserted into surrogate mothers
Increases the number of individuals with desired traits over a short period of time (compared with natural selection)
Decreases frequency of undesired alleles

13. Artificial Pollination
Humans pollinate plants with desired traits together
Increase frequency of desired alleles
Can also create new species by breeding together plants that would normally remain reproductively isolated

14. Cloning Asexual production of genetically identical organisms
Decreases genetic diversity
Cloned organisms are all equally as vulnerable to new selection pressures (therefore more susceptible to possible extinction)

16. Gene Transfer Between Species
Introducing foreign genes into a species (transgenic organisms)
Increase genetic diversity within a species
May increase some organism’s chances of survival with particular selection pressures (therefore they survive to pass their alleles to successive generations, whereas normally they would not have)

18. Gene Therapy, Stem Cell Therapy
Gene therapy introduces non-faulty genes into cells that have faulty copies of that gene
Stem Cell therapy – replaces faulty cells with functional cells
Both therapies increase the chances of the organism’s survival and therefore their ability to pass on alleles that may not have normally been passed onto future generations (e.g. the allele coding for the faulty gene in gene therapy patients will now continue in the population)

19. Genetic Screening
Testing for genetic disorders in potential parents or in a pregnant woman before birth, by extracting DNA from the embryo (or the fluid surrounding the embryo)
May result in decision not to have a child that would otherwise be born
May result in decision not to reproduce
Alleles not passed onto successive generations that might have been passed on otherwise
(contraceptives have the same effect)

20. Collection of amniotic fluid with cells of embryo (and therefore it’s DNA)

21. Overcoming Infertility in Humans
There are many different ways in which infertility can be overcome, in order to allow couples to conceive.
Some examples are:
Donor insemination(donor sperm used)
IVF (multiple eggs fertilised and implanted)
Donation of eggs (if woman can’t produce viable eggs of her own…uses partner’s sperm)
Surrogacy (use surrogate mother’s uterus)
Gamete intrafallopian transfer (increase chance of successful fertilisation)

22. Effects on evolution:
All of these techniques result in pregnancies that may not normally occur
This results in alleles being passed onto successive generations which may not have normally been passed on
Some of these methods also result in allele combinations that might not normally have occurred