One of the reasons why the fish population remains approximately the same from one generation to the next is because not all the eggs laid will survive to adulthood. There are several factors which bring about elimination of the the newly hatched eggs. Examples of these are predators and diseases which eliminate the young offsprings at different stages before they develop into adulthood.
Secondly, production of many eggs by the different fish species leads to competition for survival. Resources such as water, food, oxygen and shelter have to be fought for and its only the fittests that will be able to survive till the reproduction stage.
Keystone species, they kinda hold the food webs together
The two enzymes that are used during DNA replication is helicase
and polymerase. Each enzyme has distinct role that made it a vital part of the replication.
In the course of DNA replication, the initial stage is to unzip the double
helix structure of the DNA molecule by the enzyme helicase, which breaks the
hydrogen bonds that holds the complementary bases of DNA.
Moreover, the DNA polymerase has the ability to exactly copy a
DNA template. This enzyme binds to the leading strand and then adding a new
complementary nucleotide bases to the DNA strand. In addition, it catalyzes the joining of
deoxyribonucleoside 5′-triphosphates (dNTPs) to form the increasing DNA chain.
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Changing environments and competition for survival are the answer so D is the correct answer