Answer:
The correct option is <u><em>A. they evolved from land mammals.</em></u>
Explanation:
The process of evolution explains how closely one organism is to another based on their common ancestors. Scientists believe that those organisms which show many similarities in their structures or functions might have evolved from a common ancestor in the past.
As in the above-mentioned question, scientists have observed that cetaceans lack gills and breath air, this is a property of land mammals. The cetaceans have fin bones which are similar to the limb bones. As limb bones are present in land mammals, hence they cetaceans and land mammals might have common ancestors in the past.
Answer:
Let the "barred" allele be caller B and the "non-white" allele b. Since chickens use chromosomes 
and 
to determine sex, hens would have chromosomes 
, and roosters would have chromosomes 
. A Z-linked gene is represented as a superscript on the chromosome, 
for the dominant allele and 
for the ressesive allele.
A barred hen would have a copy of B on its Z chromosome, a non-barred rooster would have both copies of b on both Z chromosomes. Using Punnet squares to represent the crosses we get the following cases:
That is a ratio of two barred heterozygote roosters to two non-barred hens. Crossing them we get:
That is a ratio of one barred heterozygote rooster to one barred hen to one non-barred rooster to one non barred hen.
Simple organic molecules can be organized into much longer, more complex molecules.
The correct answer is option D
The energy in the form of heat is absorbed by the water to convert itself into vapour during the process of evaporation. This energy is then released in the atmosphere when the water vapor gets converted into clouds during the process of condensation. From the start of the water cycle , the heat energy of the sun gets converted into the kinetic energy to raise the water vapour to certain height. After reaching heights Kinetic energy is converted into potential energy and then it is finally released to atmosphere after condensation. In the entire process the total energy remains constant it is just being converted from one form to another.
It is called mechanical weathering or physical weathering.
