Variation and selection Flashcards iGCSE Biology

[q] What is the Process of adaptation?

[a] The process, resulting from natural selection, by which populations become more suited to their environment over many generations is called the Process of adaptation.

[q] What is Adaptive feature?

[a] The inherited functional features of an organism, resulting from natural selection, that increase its fitness, chance of survival and reproducing is called Adaptive feature.

[q] Adaptive Features of Xerophytes?

[a] Adaptive Features of Xerophytes are:

• Sunken stomata;
• Hairs;
• Small surface area;
• Fleshy leaves;
• Few leaves;
• Reflective surfaces;

[q] What is Gene mutation?

[a] A change in the base sequence of DNA is called Gene Mutation.

[q] How do we carry out Selective Breeding?

[a] Selective Breeding is carried out by

1. Human selects individuals with desirable features
2. These individuals are cross-bred to produce the next generation
3. Offspring with most desirable features are chosen to continue the breeding programme.
4. Process repeated over a number of generations.
5. cross / breed, (parent) plants with desired feature;
6. (grow seeds and) chose offspring for (desired) feature(s);
7. cross (offspring) plants showing features with, original
   variety / self / each other;
8. keep / many generations of, crossing and selecting;
9. any detail; e.g. bagging flowers / transfer of pollen (with
   paintbrush) / detail of seed collection.

[q] Describe Natural selection?

[a] Natural selection is described as:

1. Individual in a species show a range of variation caused by differences in genes.
2. When organisms reproduce, they produce more offspring than the environment is able to support.
3. This leads to a competition for food and other resources which results in a struggle for survival.
4. Individuals with characteristics most suited to the environment have a higher chance of survival and more chance to reproduce.
5. Therefore, alleles resulting in these characteristics are passed to their offspring at a higher rate than those with characteristics less suited to survival.
6. In the next generation, there will be great number of individuals with the better-adapted variations in characteristics.

[q] What is a Variation?

[a] Differences between individuals of the same species is called Variation.

[q] What are the adaptive features of hydrophytes?

[a] Adaptive features of hydrophytes are:

• Large air spaces in leaves.
  
• Large and flat leaves
  
• Stomata positioned on upper epidermis
  
• No waxy cuticle
  
• Small root system
  

[q] What are the adaptive features of Xerophytes?

[a] Adaptive features of Xerophytes are

• Thick waxy cuticle
  
• Few, sunken stomata
  
• Small, rolled leaves/Spine
  
• Deep, extensive roots

[a]

[a] The features of continuous variation:

• Quantitative / measurable feature
  
• Range of phenotypes between two extremes.
  
  
  • Many intermediate phenotypes
    
• Not in distinct groups
  
• Influenced by environment and genotype

[q] What are the features of discontinuous variation? (e.g: Blood type, Tounge rolling)

[a] The features of discontinuous variation are:

• Qualitative feature
  
• Few, distinct phenotypes
  
• Influenced by genotype only