AP Syllabus focus:
‘Some organisms are domesticated or managed for economic returns (for example, honeybee colonies and livestock), which can negatively affect the biodiversity of those organisms.’
Domestication and intensive management make certain species highly productive for humans, but they often narrow genetic variation. Reduced biodiversity within these organisms can increase disease vulnerability, lower resilience, and raise long-term sustainability risks.
What domestication and management mean in APES
Domestication and managed populations describe human control over breeding, survival, and movement to increase economic return (for example, honeybee colonies and livestock).
Domestication: The long-term process of breeding and keeping organisms under human control to favor traits useful to people (e.g., docility, high yield).
In domesticated systems, humans act as a strong selective pressure, favouring a few desired traits (rapid growth, uniform size, high milk production, gentle temperament), often at the expense of overall variation.
Managed population: A population whose reproduction and survival are deliberately controlled by humans (e.g., through selective breeding, culling, captive breeding, or controlled mating).
How biodiversity can decline within domesticated/managed organisms
Within-species biodiversity is mainly genetic diversity (variety of alleles). It matters because it supports adaptation to new threats like disease, parasites, and climate stress.
Mechanisms that reduce genetic diversity
Selective breeding (artificial selection): repeatedly breeding individuals with preferred traits increases uniformity.
Small breeding pools: reliance on few sires/queens or popular bloodlines reduces the number of breeding individuals.
Genetic bottlenecks: founding a herd/line from a small number of individuals limits starting variation.
Concept diagram of the bottleneck effect: a large, genetically diverse population is suddenly reduced (e.g., by a disaster), and the surviving population carries only a subset of the original alleles. The image visually reinforces why post-bottleneck populations often have lower genetic diversity and therefore reduced capacity to respond to new stressors. Source
Inbreeding: mating among relatives becomes more likely in closed or isolated breeding programmes.
Inbreeding depression: Reduced fitness (e.g., survival or reproduction) that can occur when closely related individuals breed, increasing harmful recessive traits.
A key idea is trade-off: high short-term productivity can come with low long-term resilience.
Outcomes for biodiversity and ecosystem stability
Higher disease and parasite susceptibility: genetic uniformity can allow a single pathogen/parasite strain to spread rapidly through the population.
Lower adaptive capacity: fewer alleles can mean less ability to cope with temperature stress, new diets, or emerging diseases.
Loss of locally adapted strains: traditional landraces or heritage breeds may be replaced by a few high-yield lines, shrinking the species’ total genetic “toolkit.”
Honeybee colonies as a managed population example
Honeybees are managed for pollination services and honey production.
Labeled honey bee anatomy and caste-comparison diagrams (worker vs. queen vs. drone). These visuals help distinguish colony castes and highlight that beekeeping management often centers on controlling queen reproduction, which can indirectly shape genetic diversity in managed colonies. Source
Management can reduce bee biodiversity when:
Beekeepers favour certain queen lineages (docile, high honey yield), reducing variation.
Colonies are moved and replaced frequently, promoting uniform stock.
Disease/parasite pressures (and responses to them) select narrowly for a few survivable lines, potentially shrinking overall diversity.
Lower genetic diversity in bees can increase vulnerability to novel pathogens and reduce colony resilience under stress (temperature extremes, poor forage).
Livestock as a managed population example
Livestock are managed for meat, milk, fibre, or labour. Biodiversity can decline when:
Production focuses on a small number of commercial breeds worldwide.
High-intensity breeding uses a few males for many offspring (amplifying narrow genetics).
Traits are selected that inadvertently correlate with health issues (e.g., reduced fertility or weaker immune responses in some lines).
These patterns can increase the chance that a single disease or environmental change causes major losses across large, genetically similar herds.
What APES students should be ready to explain
How economic returns drive domestication/management decisions.
How narrowing the breeding pool reduces genetic diversity within the domesticated organism.
Why reduced biodiversity can increase risk (disease outbreaks, reduced resilience), even when productivity is high.
FAQ
Studbooks can prevent random mating and track lineage, but “closed” programmes limit new genes entering the population.
This can increase relatedness over time unless managers deliberately balance breeding pairs and maintain multiple lines.
Effective population size is the number of individuals actually contributing genes to the next generation.
If many animals exist but only a few males breed, effective size is small, accelerating loss of genetic variation.
Crossbreeding can increase heterozygosity and reduce inbreeding problems.
However, heavy crossbreeding can also erase rare heritage breeds if not managed carefully.
Storing semen/eggs/embryos can preserve alleles from rare or older lines.
It allows reintroduction of genetic material later, even if a line declines in living populations.
Genes affecting a target trait can be linked to other traits (pleiotropy or genetic linkage).
Selecting strongly for yield or appearance can inadvertently increase health problems or reduce fertility and immune performance.
Practice Questions
State what is meant by domestication and give one way it can reduce biodiversity in the domesticated organism. (2 marks)
1 mark: correct meaning of domestication (human-controlled breeding over time to favour useful traits).
1 mark: one valid biodiversity impact (e.g., reduced genetic diversity via selective breeding/small breeding pool/inbreeding).
Explain how managing honeybee colonies OR livestock for economic returns can negatively affect the biodiversity of that organism and increase vulnerability to environmental change. (6 marks)
1 mark: identifies management for economic return (e.g., selecting queens/sires; intensive breeding).
1 mark: explains selective breeding increases uniformity/reduces genetic diversity.
1 mark: explains small breeding pool or popular lineages reduce allelic variation.
1 mark: links reduced diversity to higher disease/parasite outbreak risk.
1 mark: links reduced diversity to lower adaptive capacity to stress (e.g., temperature/novel pathogens).
1 mark: applies to the chosen organism with a relevant detail (bees: queen lineages/colony replacement; livestock: commercial breeds/few sires).
