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Mutation creates new genetic variants; sexual reproduction reshuffles alleles. If an inherited variant improves survival or reproduction in particular conditions, its carriers may leave more offspring and the allele becomes more frequent. The environment selects among variants rather than deliberately producing the mutation an organism needs. Antibiotic resistance illustrates selection in a changing environment. Evolution concerns populations over generations, not one individual choosing to adapt.
Video by Cognito. The video’s own board label is retained; follow the specification reference and scope notes on this lesson for assessed content.
Viewing focus: Explain natural selection and speciation
After watching, attempt these questions before opening the answers. You can also use the written lesson below.
After watching 1: Where do new alleles ultimately originate?
Mutation. Mutations are not directed toward a future requirement.
After watching 2: What is a risk of repeated inbreeding?
Reduced genetic diversity. Harmful recessive combinations may become more common.
What you'll be able to do
Mutation creates new genetic variants; sexual reproduction reshuffles alleles. If an inherited variant improves survival or reproduction in particular conditions, its carriers may leave more offspring and the allele becomes more frequent. The environment selects among variants rather than deliberately producing the mutation an organism needs. Antibiotic resistance illustrates selection in a changing environment. Evolution concerns populations over generations, not one individual choosing to adapt.
Selective breeding chooses parents with desired traits over generations, but can reduce genetic diversity and increase inherited problems through inbreeding. Genetic engineering transfers or modifies selected genetic information; a bacterial plasmid can carry a useful gene into a host. These methods are not identical. Cloning can produce genetically matching individuals, which may have agricultural benefits but limited genetic diversity. Evaluate a particular use using evidence, costs and possible environmental effects.
Classification groups organisms by shared features and evolutionary relationships. DNA and protein comparisons provide evidence alongside anatomy and fossils. A species is commonly described using successful interbreeding to produce fertile offspring, though this definition has limitations for fossils and asexual organisms. Isolation and selection can lead populations to become reproductively separated. New evidence can change classification, so revising a model is part of scientific work rather than evidence that all grouping is arbitrary.
Attempt these problems on paper before opening the worked reasoning. Explain your steps as well as giving a final answer.
Common mistakes to avoid
Key takeaways
Question 1: Give one benefit and one limitation of selective breeding for high milk yield.
Evaluate both productivity and population resilience.
Check the assessed scope and practical or mathematical requirements.
An external explanation or interactive activity to use alongside the lesson. It may include extension material.
Close the notes and answer from memory. Revisit any explanation you cannot yet reconstruct.
Test yourself
Answer a few questions, then review anything you missed.
Start with the quiz above to check the key ideas. You can also choose another topic from the practice library.