Answer:
The daughter cells need a copy of every chromosome in order to replicate and separate.
Explanation:
Cells have to replicate their genetic material to make a whole other cell. Before mitosis the cells need this step for mitosis.
Answer:
New allele combinations are acted upon by natural selection.
Explanation:
Recombination may be defined as the process of the exchange of the genetic material between the homologous chromosomes of the non sister chromatid. The combined trait will be visible in the upcoming generation.
The recombination allows the generation of the new genes in the population. These new genes if beneficial for the population will be pass to the next generations. The new allele will be favored by the natural selection and increases the chance of survival of the population.
Thus, the correct answer is new allele combinations are acted upon by natural selection.
The Precambrian era envelopes the major bulk of the history of the Earth, beginning from the creation of the planet approx 4.5 billion years ago and terminating with the origination of composite, multicelled forms of life approximately 4 billion years after.
The Precambrian refers to the earliest of the geologic ages that are signified by the distinct layers of sedimentary rock. The Earth was about more than six hundred million years old when life started. The planet had cooled down from its native molten state, creating a solid crust and oceans formed by water vapor in the atmosphere.
At about three billion years ago, the atmosphere of the Earth was virtually devoid of oxygen. At approximately 2.4 billion years ago, oxygen was discharged from the seas as a waste product of photosynthesis by cyanobacteria. The levels of the gas slowly raised, attaining about 1 percent around two billion years ago.
Approximately 800 million years ago, the levels of oxygen attained about 21 percent and started to breathe life into more composite species. The oxygen-rich ozone layer was also created, protecting the surface of the Earth from the harmful solar radiation.
