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1. Human impact on evolutionary processes
EL: To explore how humans impact on evolution
Selective breeding
• Humans select and modify the gene pool to meet a human need.
• Economic or aesthetic features may have been selected against in the wild
Reproductive technologies
• Examples include artificial pollination in plants and insemination in animals
• Can result in loss of genetic variation in a population – loss of alleles
Reproductive technologies
• Humans have choice of reproductive technologies that prevent or enhance fertility– Contraception– IVF– Donor sperm and
eggs
Genetically modified organisms
• Genotype may be modified by turning a gene on or off.
• Transgenic organisms have foreign DNA inserted into their cells – species barrier overcome
Cloning
• Applying asexual reproduction to sexually reproducing organisms
• Nucleus from mature cell placed into the egg cell with nucleus removed from a donor animal
Gene therapy• Replacing faulty genes with
‘normal’ genes
• Diseases resulting from mutant alleles can be eliminated
• New genes can be delivered to cell via direct delivery or viral delivery
• Currently being developed for somatic cells only
Genetic screening• Information can be used by
individual to make informed decisions about future, including having children
• Parents are able to make informed choice about continuing with pregnancy
• Implications affect individual and the gene pool – alleles
may be eliminated.
Your personal genome for all to see?
• Watch the clip from Hungry Beast:– http://hungrybeast.abc.net.au/stories/dna-testing-how-genetically-fla
wed-am-i• Scroll down and follow the links to Kurt’s detailed genetic results • Visit the “23 and me” and “Navigenics” websites and investigate
what they test for and what they don’t test for• Find out a bit about the BRCA genes:
http://www.cancervic.org.au/how-we-can-help/family-cancer/genetics-breast-cancer
• Group discussion on the following questions:– Should genetic testing be compulsory for everyone? Why? Why not?– Would you get a genetic test done? Why? Why not?– If there was a history of breast or prostate cancer in your family, do
you think you’d get tested for the BRCA gene?
Stem cells• Stem cells can be harvested
from both embryos and adults
• Scientists are investigating chemical signals required to make stem cells differentiate into different cell types and tissues.
• This may lead to repair of cellular damage (e.g. spinal cord injury)
Habitat destruction and cultural beliefs
• In 1900 ~100,000 wild tigers in Asia
• Today ~7,000 due to habitat loss, hunting and illegal trade in tiger parts
• Three tiger sub-species have become extinct since 1940. all others are threatened.
Population growth
More people were added to the Earth in the 20th century than any other time in human history.
Are there too may people for the Earth to sustain?
SummaryIntervention Outcome
Selective breeding We select out alleles that may not give advantage in the wild
Reproductive technologies Reduce genetic variation
GMOs Reversing species barriers
Cloning Reduce genetic variation
Gene therapy Individual may benefit, but allele still in gene pool
Genetic screening Remove unwanted alleles from the gene pool
Habitat destruction Extinction, loss of biodiversity
Human cultural beliefs Extinction of species
Overpopulation Depletion of natural resources
Technology Maintains alleles in gene pool that may otherwise not survive
Activity
• Class discussion – chapter review qu 12&13
• Chapter 16 quick check, biochallenge and chapter review qu 1-11
Reflection
• Do you think humans should be able to influence evolutionary processes? Why? Why not?