Photo AI
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
Meiosis is a crucial process in sexual reproduction that introduces genetic variation among offspring. This occurs through two primary mechanisms: crossing over and the random arrangement of chromosomes.
- Crossing Over: During prophase I of meiosis, homologous chromosomes pair up and exchange segments of genetic material. This recombination results in new combinations of genes, contributing to genetic diversity.
- Random Arrangement of Chromosomes: During metaphase I, the orientation of each pair of homologous chromosomes is random. This random assortment leads to a variety of combinations in the gametes produced.
Step 2
Random Mating as a Source of Variation
Answer
In many species, mating occurs randomly, which allows for the mixing of genetic material from different individuals. This process ensures that offspring inherit a unique combination of alleles, further increasing the genetic variability within a population.
Humans and some other mammals tend to choose partners based on particular traits, which can influence the genetic makeup of future generations.
Step 3
Chance Fertilization of Egg Cells by Sperm Cells
Answer
During reproduction, multiple sperm cells can fertilize multiple egg cells. Each sperm cell carries different genetic information due to the processes mentioned above. Consequently, the fusion of unique combinations of sperm and egg cells can lead to diverse offspring with varying traits.
The genetic variation in offspring can enhance adaptability, providing a survival advantage in changing environments.
Step 4
Mutations
Answer
Mutations represent another significant source of genetic variation. They are spontaneous changes in the DNA sequence that can occur due to various factors, such as environmental influences or errors during DNA replication.
- Types of Mutations: Mutations can be gene mutations, which affect a specific gene, or chromosomal mutations, which affect the structure or number of chromosomes.
- Impact of Mutations: While many mutations may be neutral, some can lead to new characteristics or the formation of different proteins, enhancing genetic variation within a species.