Module 8

1. Module 8

1.19. Page 3

Lesson 4

Module 8—Populations, Individuals, and Gene Pools

Lesson Summary

This lesson focused on the following question:

What are the intended and unintended consequences of human activities and scientific and technological developments on gene pools?

Technologies developed to meet human needs often have consequences for the gene pools of natural populations—some intended and some not intended.

Intended Consequences

Effective technologies (e.g., medical, pharmaceutical, surgical) increase survival of people with genetic diseases.
Transfer of desirable genes into crops and livestock using recombinant DNA techniques improves yields and profitability.
Crops and livestock are cloned to create a uniform and economically profitable food or drug product.
Monoculture produces vast quantities of food efficiently.
Cloning of endangered or possibly extinct organisms is done to preserve rare alleles from extinction.
Creation of wildlife corridors across highways or through industrial and urban development increases gene flow and maintains diversity in populations.
Creation of wildlife preserves allows threatened species and their alleles to avoid extinction.
Introduction of foreign species can be used as a biological method of killing pests.

Unintended Consequences

Use of antibiotics selects for resistant alleles. Bacterial populations become immune to antibiotics.
Agriculture, dam construction, road building, urban sprawl, logging, and industrialization result in habitat destruction and fragmentation, leading to rapid selection of one form, reducing genetic diversity.
Technologies (e.g., medical, scientific) that increase survival of people with genetic diseases increase the frequency of disease alleles in the population.
Monoculture of very few varieties means that alleles for many varieties are lost from the gene pool—the species becomes less adaptable in the face of disease, pests, or environmental change. Monocultured crops use huge quantities of petrochemicals, fertilizers, pesticides, herbicides, and fungicides with human health costs.
Over-hunting and poaching can threaten extinction and reduce diversity by removing “desirable” alleles from the gene pool; e.g., the biggest and strongest animals are valued most by hunters. Weakened gene pools result.
Creation of wildlife preserves can lead to genetic drift if either the founder or the bottleneck effect is in play. Wildlife preserves lead to inbreeding, which can also result in genetic drift reducing diversity and causing the population to be less adaptable if the environment changes.
Genes introduced into crops and livestock by biotechnology can “jump” to wild species, changing the gene pool substantially. For example, the gene for herbicide resistance could jump from corn to weed species.
When a foreign species is introduced, it often out-competes native species in its trophic level, which disrupts food chains and ecosystems.

Lesson Glossary

Consult the glossary in the textbook for other definitions that you may need to complete your work.

antibiotic resistance: the ineffectiveness of an antibiotic that results if a bacterial cell has alleles that make it resistant to being destroyed by antibiotics

Each dose of antibiotics will allow these bacteria to survive and pass on their resistant traits to the next generation—more of each generation are resistant until the resistant allele is the most common; at this point, the antibiotic is no longer effective.

biotechnology: manipulation of genes or traits

invasive species: species that are introduced to an area and that out-compete the indigenous species in its trophic level for nutrients and/or prey; are less affected by limiting density-dependent and density-independent factors

monoculture: the cultivation of a single crop

transgenic organism: an organism that has genes from more than one species

wildlife corridor: a route used by wildlife to move from one territory to another

Wildlife corridors are often part of a migratory pattern.