Key physical features. All three species share similar physical characteristics - a relatively small body and a 'robust' or strongly built skull including large lower jaws with extremely large molar teeth.
Some mutations don't have any noticeable effect on the phenotype of an organism. This can happen in many situations: perhaps the mutation occurs in a stretch of DNA with no function, or perhaps the mutation occurs in a protein-coding region, but ends up not affecting the amino acid sequence of the protein.
Answer:
The environmental factor that could lead to a decrease in genetic variation in a tuna population is an increase in pollution (second option).
Explanation:
There is a correlation between genetic variability and environmental pollution, the latter being a factor that impacts negatively on the variability of a specific population.
The concept of pollution stress not only implies a low rate of reproduction, but it is also a factor that prevents genetic exchange with other populations, which is a factor that makes the genetic variability decrease in a population.
For these reasons an increase in pollution implies a decrease in genetic variability in a tuna population.
- <em>Other options, such as </em><u><em>an increase in food availability</em></u><em>, a</em><u><em> decrease in tuna fishing
</em></u><em> or </em><u><em>a decrease in tuna predators</em></u><em>, are environmental factors that contribute to increased genetic variability.</em>
