There are two main reasons why cells divide rather than continuing to grow larger and larger: ... more demands the cell places on its DNA. If the cell grows too large, it will have trouble moving enough nutrients and wastes across the cell membrane.
They cause climate change by trapping heat, and they also contribute to respiratory disease from smog and air pollution. Extreme weather, food supply disruptions, and increased wildfires are other effects of climate change caused by greenhouse gases.
If two parents have dark hair, the child will most likely have dark hair.
If one has light and the other dark, the child has a 75% chance of having dark hair or a dark-dominated mix because the gene for dark hair is dominant.
If two parents have light hair, the child will most likely have light hair.
Of course, it gets a lot more complicated than this, the genes of the child's grandparents and great grandparents could be carried by the parents as well. So if the parents have dark hair but they each have a parent with light hair, the light hair gene will be carried by them and could be passed on to the child. That's how it is with genetic disorders, such as Systic Fibrosis or Sickle Cell Anemia.
Answer:
When populations are separated by a barrier forming a new species
