Variation: inherited information and environment
| English | 中文 | Pinyin |
|---|---|---|
| variation/ˌveərɪˈeɪʃn/ | 变异 | biàn yì |
| mutation/mjuːˈteɪʃn/ | 突变 | tū biàn |
What would explain this observation?
- Genetically identical plants can grow to different heights in different light. Different heights alone do not establish that the plants have different alleles.
- Start with a prediction. State the quantities or features you would compare, then decide what evidence could distinguish two explanations.
Build the model
- Variation 变异 means differences in characteristics among individuals in a population. Some differences result from inherited genes, some from conditions during development and many from an interaction between genes and environment. There is usually extensive genetic variation within a population of a species. Sexual reproduction reshuffles inherited information; new genetic variants originate through mutation 突变.
- variation: Differences in characteristics among individuals in a population; mutation: A change in genetic material that can produce a new variant.
What can explain different heights among genetically identical plants?
Mutations occur continuously. Most do not affect the phenotype, some influence it and very few determine a new phenotype in the specification’s account. A variant that gives an advantage after an environmental change can become more common through selection. The environment does not intentionally produce exactly the mutation an organism needs.
Match each technical term to its precise meaning.
Use the definitions to distinguish related quantities and processes.
Choose evidence that can test it
- Mutations occur continuously. Most do not affect the phenotype, some influence it and very few determine a new phenotype in the specification’s account. A variant that gives an advantage after an environmental change can become more common through selection. The environment does not intentionally produce exactly the mutation an organism needs.
- Compare supplied plant records with genotype and growing conditions stated. Hold one factor constant when testing another. For height data, calculate a mean and range, label units and inspect the distribution. Use fictional or plant measurements instead of sensitive personal characteristics; a visible association needs further evidence before attributing cause.
Which two habits make the investigation or model in this case more defensible?
Compare supplied plant records with genotype and growing conditions stated. Hold one factor constant when testing another. For height data, calculate a mean and range, label units and inspect the distribution. Use fictional or plant measurements instead of sensitive personal characteristics; a visible association needs further evidence before attributing cause.
Work from known quantities
- State the known values and their units. Choose the relation because its assumptions fit this case, then rearrange before substitution.
- Known: four cloned plants in one condition have heights 12, 14, 15 and 15 cm. Mean = 56/4 = 14 cm; range = 15−12 = 3 cm. A different mean in another condition is compatible with an environmental effect, but conclusions require matched age, soil, water and measurement methods.
Clone heights are 16, 18, 19 and 19 cm. Calculate mean height. Use the same sequence: known quantities → model → relation → substitution → unit and interpretation.
Clone heights are 16, 18, 19 and 19 cm. Calculate mean height.
The result is 18 cm. Known: four cloned plants in one condition have heights 12, 14, 15 and 15 cm. Mean = 56/4 = 14 cm; range = 15−12 = 3 cm. A different mean in another condition is compatible with an environmental effect, but conclusions require matched age, soil, water and measurement methods.
Check the conclusion and its limits
- Variation is not limited to genetic differences. The same genotype can produce different phenotypes in different environments. A mutation can have no measured effect under one set of conditions, so a phenotype observation does not reveal every DNA difference.
- Return to the original observation. Explain what the result supports, which conditions it assumes, and one way to test a competing explanation.
An organism produces a useful mutation because it needs one. This claim is false: Variation is not limited to genetic differences. The same genotype can produce different phenotypes in different environments. A mutation can have no measured effect under one set of conditions, so a phenotype observation does not reveal every DNA difference.
Variation: inherited information and environment: Mutations occur continuously. Most do not affect the phenotype, some influence it and very few determine a new phenotype in the specification’s account. A variant that gives an advantage after an environmental change can become more common through selection. The environment does not intentionally produce exactly the mutation an organism needs.
An organism produces a useful mutation because it needs one.
Variation is not limited to genetic differences. The same genotype can produce different phenotypes in different environments. A mutation can have no measured effect under one set of conditions, so a phenotype observation does not reveal every DNA difference.
Differences in characteristics among individuals in a population: write the technical term.
variation means Differences in characteristics among individuals in a population.