Grade by Grade
C. Evolution · Evolution

Weighing Artificial Selection and Biotechnology: Economic and Environmental Costs and Benefits

C1.1 C2.2 C3.4 A1.9 A2.1About 75 minutes
Learning goals
  • I can analyse the economic and environmental advantages and disadvantages of an artificial selection technology, using research.
  • I can explain how artificial selection and biotechnology can reduce genetic diversity and why that matters.
  • I can tell selective breeding apart from genetic engineering and gene editing.
  • I can evaluate sources for bias and reliability on a controversial topic.
  • I can describe careers connected to evolution and breeding.

Words to know

monoculture
Growing a single crop variety over a large area.
genetic erosion
The loss of genetic variety in a crop or breed, for example when many local varieties are replaced by a few modern ones.
biotechnology
Using living things or their parts, including their DNA, to make products or solve problems.
genetically modified organism (GMO)
An organism whose DNA has been changed in a laboratory, often by adding a gene from another species.
gene editing
Making precise changes to an organism's own DNA (for example, with CRISPR).
clone
An organism that is genetically identical to another.
gene bank (seed bank)
A collection that stores seeds or other genetic material to preserve genetic diversity.
stakeholder
A person or group affected by a decision (farmers, consumers, Indigenous communities, companies, governments, ecosystems).

Is it worth it?

Almost every food in your kitchen has been shaped by artificial selection. Breeding has fed billions more people than would otherwise be possible. But it has costs too: uniform crops that a single disease can wipe out, animals with health problems, lost traditional varieties, and heavy reliance on fertilizers and pesticides.

C1.1 asks you to analyse, using research, the economic and environmental advantages and disadvantages of an artificial selection technology. This lesson gives you the background and a method for doing that analysis well.

Advantages

Economic:

  • Higher yields of crops, milk, meat and eggs mean more food and income from the same land, animals and labour.
  • New products and markets. Canola, developed in Canada, became one of the country's most valuable crops and a major export.
  • Lower costs when varieties resist diseases or pests (less spending on pesticides) or mature faster (earlier harvests).

Environmental:

  • Higher yields mean less land needs to be cleared for farming to produce the same amount of food, leaving more room for forests and wetlands.
  • Disease- and pest-resistant varieties can reduce pesticide use.
  • Drought- or cold-tolerant varieties can be grown with less irrigation or in shorter seasons.

Disadvantages

Loss of genetic diversity. Breeders use only a few top individuals as parents. Farmers then replace many local varieties with a few high-yielding ones, a process called genetic erosion. A crop that is genetically uniform has no variation for natural or artificial selection to work with when conditions change.

Monoculture risk. If a large area is planted with one variety, a single new disease or pest can spread through it all. In the 1840s, much of Ireland's population, especially the rural poor, depended on potatoes for food, and a large share of the crop was a single variety (the Lumper), grown from pieces of tubers, so the plants were genetically alike. When a new plant disease (late blight, caused by the water mould Phytophthora infestans) arrived, harvests failed across the country, contributing to a devastating famine. Today, the Cavendish banana, grown from genetically identical cuttings, is threatened by a fungal disease.

Other costs:

  • Animal health and welfare: some breeds have inherited health problems (e.g., breathing problems in flat-faced dog breeds; leg and heart problems in very fast-growing chickens).
  • Reliance on inputs: many high-yield varieties need lots of fertilizer, water and pesticides, which can pollute water and harm wildlife.
  • Economic costs for farmers: hybrid seed does not breed true, so farmers must buy new seed every year; patented varieties can increase costs and reduce farmers' control.
  • Antibiotic use in intensive animal farming can select for resistant bacteria (see the lesson on resistance).
Uniform crop (one variety)Mixed varietiesa new disease infects every plantonly one variety is infected
Why genetic diversity matters. In a uniform crop, a disease that can infect one plant can infect all of them. In a field of mixed varieties, some are likely to resist.

From selective breeding to biotechnology

C3.4 includes biotechnology among the mechanisms that affect evolution. Modern biotechnology goes beyond choosing parents:

  • Genetic engineering (GMOs): scientists insert a specific gene, sometimes from another species, into an organism's DNA. Most canola grown in Canada is genetically engineered to tolerate certain herbicides, so farmers can spray weeds without harming the crop.
  • Gene editing (for example CRISPR): precise changes to an organism's own genes, such as switching off one gene.
  • Cloning: producing genetically identical copies of valuable animals or plants (many fruit trees and potatoes are clones grown from cuttings or tubers).

These tools can make changes faster and more precisely than breeding. They raise some of the same concerns (lower genetic diversity, monocultures) and some new ones, such as gene flow from engineered crops to wild relatives and the evolution of herbicide-resistant weeds when the same herbicide is used year after year. You will learn how recombinant DNA and cloning work in the Genetic Processes unit.

Protecting genetic diversity

  • Gene banks store seeds and other genetic material. Plant Gene Resources of Canada, based in Saskatoon, keeps a national collection of crop seeds; the Svalbard Global Seed Vault in Norway stores backup copies from around the world.
  • Heritage and local varieties are kept alive by seed-saving groups and farmers, including Indigenous seed-keepers who grow and share traditional varieties of corn, beans and squash.
  • Rare livestock breeds are conserved because they carry alleles for hardiness and disease resistance that may be needed in the future.
Advantageshigher yields, less landincome and exportsdisease-resistant varietiesbetter nutrition or qualityDisadvantagesloss of genetic diversitymonoculture riskanimal health and welfarecosts to small farmersEvaluate both, for each stakeholder, using evidence
A good analysis weighs economic and environmental advantages and disadvantages, considers each stakeholder, and uses evidence from reliable sources.
Worked example

Example 1: Let's analyse an artificial selection technology

Analyse the economic and environmental advantages and disadvantages of breeding dairy cows for very high milk production.

  1. Identify the technology: selective breeding of dairy cattle (aided by artificial insemination, which lets one top bull father many thousands of calves).
  2. Economic advantages: more milk per cow means more income per animal and lower cost per litre; fewer cows needed for the same milk.
  3. Environmental advantages: fewer cows for the same milk can mean less feed, land, water and greenhouse gas per litre of milk.
  4. Economic disadvantages: high-producing cows may need more expensive feed and veterinary care; health problems can shorten their productive lives.
  5. Environmental/biological disadvantages: heavy use of a small number of bulls reduces genetic diversity within the breed, increasing the risk from inbreeding and disease; very high production can strain cows' health (welfare concern).
  6. Conclusion (with stakeholders): farmers and consumers benefit economically, and some environmental impacts per litre fall, but breeders need to monitor genetic diversity and select for health and longevity, not only for milk. Much current dairy breeding does include health traits.

High-milk breeding brings clear economic and some environmental benefits, but risks lower genetic diversity and animal health problems; balanced breeding goals reduce the risks.

Worked example

Example 2: Let's evaluate sources on a controversial topic

You are researching genetically engineered crops. Rate each source and explain: (a) a news release from a seed company that sells engineered seed; (b) a blog post by an anonymous author titled "GMOs: the hidden poison"; (c) a report by a national academy of sciences that reviewed hundreds of studies; (d) a peer-reviewed article in a scientific journal.

  1. Ask: Who wrote it? Do they have expertise? Do they have something to gain? Is it based on evidence? Is it balanced and recent?
  2. (a) Company release: useful for facts about its own product, but it has a financial interest, so expect only positive points. Check claims elsewhere.
  3. (b) Anonymous blog: low reliability: no author or expertise, emotional title, likely no evidence. Do not use as evidence.
  4. (c) National academy report: high reliability: experts reviewing many studies; still check its date and any conflicts of interest.
  5. (d) Peer-reviewed article: high reliability for its specific question; reviewed by experts, but one study is only one piece of evidence.
  6. Good practice: use (c) and (d) as main sources, use (a) for product details with caution, and compare at least two sources for every major claim.

Most reliable: the academy report and peer-reviewed article. The company release is biased but can supply facts; the anonymous blog should not be used as evidence.

Careers in evolution and breeding

The ideas in this unit are used every day by:

  • plant breeders and agronomists (developing crop varieties; university degree in plant science or agriculture, often a graduate degree),
  • animal geneticists and livestock breeders,
  • conservation biologists and wildlife geneticists (managing endangered populations, gene flow and genetic diversity),
  • palaeontologists and museum scientists,
  • microbiologists and epidemiologists (tracking how bacteria and viruses evolve, including resistance),
  • science communicators and policy advisers (helping governments and the public understand evidence).

Most of these careers start with a university degree in biology or a related science.

Just for fun

Seedless watermelons are grown from seeds. Breeders cross a normal watermelon with one that has double the usual number of chromosome sets. The offspring have three sets (remember polyploidy from the speciation lesson), so they are sterile and their fruits have only tiny, soft, undeveloped seeds.

Hands-on activity

Mini research analysis (C1.1)

You need: a computer or library access, paper and a pencil.

  1. Choose one artificial selection technology: for example, breeding broiler chickens for fast growth, hybrid corn seed, herbicide-tolerant canola, breeding dogs for a particular look, or using artificial insemination in cattle.
  2. Find at least three reliable sources (government agriculture or health agency, university extension pages, peer-reviewed summaries, a national academy report). Record author, title, date and web address for each.
  3. Make a four-part table: economic advantages, economic disadvantages, environmental advantages, environmental disadvantages. Put at least two points in each, with the source number.
  4. Identify three stakeholders and how each is affected.
  5. Write a one-paragraph conclusion: on balance, do the advantages outweigh the disadvantages? Under what conditions? What would reduce the disadvantages?

What to look for: a balanced table with evidence from credible, cited sources; at least one point about genetic diversity; stakeholders such as farmers, consumers, Indigenous communities, companies and ecosystems; a conclusion that takes a position and supports it, and recognizes trade-offs.

Your turn

1

Give two economic advantages of artificial selection.

2

Give two environmental advantages.

3

What is genetic erosion?

4

Why is a monoculture of a single variety risky?

5

How is genetic engineering different from selective breeding?

6

Name one way genetic diversity of crops is protected.

7

Why must farmers who grow hybrid corn buy new seed each year?

More practice: warm-up

1

What is a monoculture?

2

What is a clone?

3

Name one tool of biotechnology.

4

Name one career that uses ideas about evolution.

5

What is a stakeholder?

More practice: on your own

1

Explain how artificial insemination can increase milk yields but also reduce genetic diversity.

2

Using evolutionary ideas, explain why growing herbicide-tolerant crops and spraying the same herbicide every year can lead to herbicide-resistant weeds.

3

A company claims its new apple variety is "100% natural and the best ever." What questions would you ask before trusting this claim?

4

Why might heritage livestock breeds be valuable even if they produce less than modern breeds?

5

Identify three stakeholders in a decision to plant a large area with one high-yielding crop variety, and one concern each might have.

Challenge

1

Explain how the history of the Irish potato famine and the current threat to Cavendish bananas illustrate the same evolutionary principle.

2

Write a balanced conclusion (4 to 5 sentences) on whether breeding broiler chickens for fast growth is, overall, an advantage. Include economic, environmental and welfare points.

3

Compare the effects on genetic diversity of (a) traditional mass selection by many independent farmers saving their own seed, and (b) a few companies supplying a single genetically engineered variety to an entire region.

Check your understanding

Quiz

1.

Which is an environmental advantage of high-yielding crop varieties?

2.

Why was the Irish potato crop of the 1840s so vulnerable to late blight?

3.

Which source is most reliable on the safety of genetically engineered crops?

4.

Genetic engineering differs from selective breeding because it:

5.

Which practice helps preserve crop genetic diversity?

6.

Spraying the same herbicide for many years can produce resistant weeds because:

For parents and teachers

Big idea (C1.1, C3.4): students analyse, using research, the economic and environmental advantages and disadvantages of artificial selection technologies, including newer biotechnologies, and evaluate their sources (A1.9). A recurring theme is genetic diversity: the more uniform a crop or breed, the less able it is to cope with new diseases or changing conditions. Careers are discussed for A2.1.

How to help: Discuss a food your family buys often: How was it bred? Who benefits? What are the costs? Help your teen find balanced sources (government agriculture sites, university extension pages) and spot biased ones.

Common difficulties:

  • One-sided answers. C1.1 requires both advantages and disadvantages, both economic and environmental.
  • Mixing up selective breeding and genetic engineering.
  • Treating every source as equal. Ask who wrote it and what they gain.

Sensitivity: the Irish famine was a human tragedy with complex causes, including political and economic ones; the lesson mentions only its biological side, briefly and respectfully.

Sources: canola history and herbicide-tolerant canola, Plant Gene Resources of Canada (Saskatoon), Svalbard Global Seed Vault, late blight and the Irish famine, Cavendish banana disease threat, and seedless watermelon breeding are documented by agriculture agencies and scientific sources.