Answer: 1. Adaptions. 2. extinct, traits. 3. genetic variation, environment.
Explanation:
<span>Having a pessimistic attitude shows having
low levels of SEROTONIN. Being pessimistic shows that a person always thinks of
the worst or always thinking negative. Some study states that low levels of
serotonin will give a person a tendency to be depressed and to feel down.</span>
I believe the answer is: 4. They require a large sample size.
The data required in a longintudinal study is taken by examining the sample population for a long period of time, as they develop over the years. The amount of population in such studies is usually really small, but the amount of time needed for start to finish is the one that become the main problem among researchers
