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There was variation in neck length in a population of Galapagos tortoises - NSC Life Sciences - Question 4 - 2018 - Paper 2
Question 4
There was variation in neck length in a population of Galapagos tortoises. The original population from the mainland was separated onto two islands with different en... show full transcript
Worked Solution & Example Answer:There was variation in neck length in a population of Galapagos tortoises - NSC Life Sciences - Question 4 - 2018 - Paper 2
Step 1
Describe how mutations lead to variation within a population
Answer
Mutations are changes in the DNA sequence that can result in new traits or characteristics within a population. These changes can occur in several forms such as gene mutations, which alter the nucleotide sequences, or chromosomal mutations that change the number or size of chromosomes.
When mutations occur, they introduce new alleles into the gene pool, resulting in genetic diversity. For example, a mutation in the gene responsible for neck length in tortoises could lead to either shorter or longer necks, thus contributing to variation.
Step 2
Describe how meiosis leads to variation within a population
Answer
Meiosis is the process of cell division that produces gametes (sperm and egg cells) with half the number of chromosomes. During meiosis, several mechanisms contribute to genetic variation:
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Crossing Over: During prophase I, homologous chromosomes can exchange segments of genetic material, creating new combinations of genes.
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Random Assortment: In metaphase I, the arrangement of homologous chromosomes is random, leading to different combinations of alleles in the gametes.
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Independent Segregation: Each pair of chromosomes segregates independently of others, further increasing the genetic variation in the offspring.
These processes ensure that the offspring produced have a mix of genetic traits, which can lead to observable differences such as the variation in neck length among the tortoises.
Step 3
Describe the role of variation in the speciation of the tortoises
Answer
Variation within a population is crucial for speciation, which is the process through which new species arise. In the case of the Galapagos tortoises, the original population was separated into two groups by a body of water, leading to geographical isolation.
As these populations adapted to their different environments over many generations, natural selection favored traits that suited each island's conditions. This resulted in significant differences in neck length and other physical characteristics. Over time, the populations became genetically distinct, exhibiting variation in genotypic and phenotypic traits.
Eventually, the two populations may have become so different that they were unable to interbreed, even if they came into contact again, indicating the emergence of two new species adapted to their respective environments.