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Describe the mechanisms that cause variation within a species - NSC Life Sciences - Question 4 - 2017 - Paper 2
Question 4
Describe the mechanisms that cause variation within a species. NOTE: NO marks will be awarded for answers in the form of flow charts, tables or diagrams.
Worked Solution & Example Answer:Describe the mechanisms that cause variation within a species - NSC Life Sciences - Question 4 - 2017 - Paper 2
Step 1
Meiosis as a Source of Genetic Variation
Answer
One of the primary mechanisms that lead to variation within a species is meiosis. During meiosis, gametes are produced through two rounds of cell division, resulting in genetic diversity. This occurs primarily due to:
- Crossing Over: During prophase I of meiosis, homologous chromosomes exchange genetic material. This recombination creates new combinations of alleles.
- Random Arrangement of Chromosomes: During metaphase I, chromosomes line up randomly at the cell's equator, leading to a multitude of possible combinations in the gametes.
Step 2
Random Mating
Answer
Random mating also contributes to genetic variation. In many species, individuals choose mates randomly, as opposed to selecting partners with particular traits. This random pairing introduces a variety of genetic combinations in the offspring, further promoting diversity within the population.
Step 3
Chance Fertilization of Egg Cells by Sperm Cells
Answer
The fertilization process itself is a significant source of variation. Typically, more than one egg and sperm cell are generated during reproduction. As a result, multiple sperm cells can fuse with various egg cells, each combination contributing to different genetic outcomes in the offspring. This enhances the overall genetic diversity within the species.
Step 4
Mutations
Answer
Mutations are another source of variation. They are sudden, random changes in the genetic code and can occur for various reasons, such as errors during DNA replication or environmental factors.
- Point Mutations: These involve changes in a single nucleotide, which can alter amino acids in proteins.
- Chromosomal Mutations: These can change the structure or number of chromosomes, leading to new traits.
- Inheritance of Mutations: If mutations occur in germ cells, they can be passed on to future generations, resulting in new characteristics within a population.