The correct options are as follows:
1. D.
<span>A clade refers to a group of organisms that are made up of evolutionary descendants that originated from a common ancestor. A clade that will survive a series of catastrophic events must be one that is made up of distantly related and diverse species. This is because, those species will have different type of adaptability capacity and will be able to adapt in different ways to the catastrophic events. Due to the differences in their ability to adapt, some of the specie will survive the catastrophic events even if others are wipe out.
2. B.
The mass extinction of one specie usually creates space for another new specie to survive. The new specie that survive the old one may possess the ability to adapt to the event that wipe out the former set of living organisms and thus, the new specie will be able to occupy and reproduce in their new space. Mass extinction is said to occur when the whole population of living organism living in an ecosystem are wipe out as a result of unfavorable conditions.
3. B.
Convergent evolution refers to the independent evolution of similar features in species that arise from different lineages. The species involved usually evolve these traits as a result of having to adapt to similar environments. Convergent evolution usually result in evolution of analogous structures, that is, structures that have similar forms or functions but which are not present in the last common ancestors of the species.
4. C.
In evolution, gradualism refers to theory that states that evolution occurs slowly and gradually, thus, large changes in evolution are actually product of small changes that occur over a long period of time. The theory of gradualism was originally proposed by James Hutton in 1795.
5. C.
Mass extinction refers to the wiping out of a a large number of species within a very short time. Mass extinction can occur as a result of severe unfavorable conditions that all the species in an ecosystem can not adapt to. An instance of this is a drastic decrease in global temperature after several massive volcanic eruptions.</span>
Both parents are normal. But, some of the kids have the disease. This indicates that the parents are heterozygous for the disease (let's use Dd). They are phenotypically fine because D is normal. But we know they must both carry the diseased d allele because their kids have the disease.
If you cross Dd x Dd you get DD, Dd, Dd and dd as the possible outcomes. But because each time they have a child they roll the dice as to which of the 4 above happens, they were unlucky as 3 of those times they got dd for their child...so 3 of them have the disease (and are dd). One is phenotypically normal but could still be Dd or DD.
