organ system must be present
The correct answer is option A, that is, the year was good for growth.
In the regions where the length of the growing season is the restricting element, the thickness of the rings of the tree can suggest that when the growing time was lengthier (at the time of warmer times) and when the growing seasons were shorter (cooler times). The study of the development of the rings of the tree is called dendrochronology.
Answer:
Alleles.
Explanation:
Gene may be defined as the functional segment of DNA that codes for the particular protein. Genes are responsible for the phenotype and genotype of the organism. Each gene may exist in multiple forms.
The variants forms of the genes are known as alleles. Alleles are the alternative form of the same gene. A single gene may have atleast two alternative form. These alternative forms together contribute the functional aspect of the organism.
Thus, the correct answer is alleles.
Answer:
Positive natural selection.
Explanation:
The positive natural selection is a type of natural selection that increases the frequency of an allele or trait when it is advantageous for the population. What happened in the example is that the mouth with the slight change in morphology (trait) was more advantageous for the population in the south in relation to the ancestral morphology (still preserved in the population in the north), and therefore its frequency increased. This, in turn, is due to the fact that the food (prey) is not the same in the two habitats (north and south). The specific prey in the south, caused the new morphology to be selected, (increasing the frequency of individuals with the new mouth), becasue probably that trait allows the trouts in the south to hunt more effectively.
