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?