Answer:
This indicates that the expression of genes depends partly on environment.
Explanation:
The case shown in the question is showing a situation where there was a genetic interaction with the environment, resulting that gene expression depends in part on the environment.
Gene and environmental interactions are revealed by penetrance and expressiveness. Penetrance is the percentage of individuals with a given gene that have a phenotype linked to this gene, such as children and parents who have the same height. In cases of penetrance, a genotype may not express the expected phenotype due to gene influences and environmental effects, as happened to the couples' children shown in the question.
Answer:
Food source and space.
Explanation:
With more animals, more food and space is required. With a sudden growth there may not be enough sufficient.
The food source could quickly run out, and same with space.
They could go for a hike or a walk. Hikes in a nearby forest are a great way to see nature on a daily basis and free of cost. If in an non rural area, such as a city, walking around town is a great way to get more physical activity! Another great way is to visit a zoo; most zoo have walking distance between the different animals. You can get both the active and nature in that as well.
(And I can't think of another one sorry)