Variation: inherited information and environment
הוצג| English | משמעות |
|---|---|
| variation/ˌveərɪˈeɪʃn/ | משתנה |
| mutation/mjuːˈteɪʃn/ | מוטציה |
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.
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?
רמת קושי 1/5 · 100 מטבעות + בונוס קטן בהשלמה הראשונה היום
Genetically identical plants share all alleles, so height differences among them must come from the environment - light, water, soil. Variation does not require genetic differences.
Match each technical term to its precise meaning.
רמת קושי 2/5 · 140 מטבעות + בונוס קטן בהשלמה הראשונה היום
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.
In the lab: 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?
רמת קושי 2/5 · 140 מטבעות + בונוס קטן בהשלמה הראשונה היום
Stating the conditions and assumptions lets others repeat the work exactly, and recording the supporting evidence lets them check the conclusion. Hiding disagreeing results removes the evidence that could challenge a wrong conclusion, and one measurement can never establish a wider claim.
Work from known quantities
- 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.
Your turn: Clone heights are 16, 18, 19 and 19 cm. Calculate mean height.
Clone heights are 16, 18, 19 and 19 cm. Calculate mean height.
רמת קושי 2/5 · 140 מטבעות + בונוס קטן בהשלמה הראשונה היום
The result is 18 cm. Known: heights 16, 18, 19 and 19 cm. Use mean = sum / count. Sum = 72. Mean = 72/4 = 18 cm. Comparing conditions needs matched age, soil and measurement.
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.
Not true: An organism produces a useful mutation because it needs one. Mutations arise at random, with no reference to what the organism needs. Selection later favours useful ones, but the mutation itself is never produced on demand.
- Variation means differences in characteristics among individuals in a population.
- Mutations occur continuously.
- Watch for: variation is not limited to genetic differences.
Mutations arise at random, with no reference to what the organism needs.
רמת קושי 1/5 · 100 מטבעות + בונוס קטן בהשלמה הראשונה היום
True. Mutations arise at random, with no reference to what the organism needs. Selection later favours useful ones, but the mutation itself is never produced on demand.
Differences in characteristics among individuals in a population: write the technical term.
רמת קושי 1/5 · 100 מטבעות + בונוס קטן בהשלמה הראשונה היום
variation means Differences in characteristics among individuals in a population.