Did you remind<span> the </span>predicted phenotype ratio<span> and </span>children<span> of </span>dihybrid parents<span> that are </span>both right-handed<span> and </span>posses free ear lobes<span> - 2159873.</span>
Natural changed to the ecosystem relate to environmental shock that occur naturally. Natural changes include floods, volcanic activity, hurricanes, etc. They can be destructive, but they also have advantages. Floods have the contribution of nutrients to the soil which was lacking. It can also relocate fishes and organisms living in bodies of water which improves the ecosystem.
Yes, crossing over does not occur during mitosis. As mitosis is simply the duplication of cells, there is no gene variation that comes from crossing-over.