Homologous chromosomes pair up and exchange segments of DNA.
Option A
<h3><u>Explanation:</u></h3>
Crossing over is an event of Prophase 1 of meiosis 1. It occurs in the zygotene phase of prophase 1. Here the homologous chromosome pairs get very close together and gets packed within protein coat. The enzymes randomly cut the DNA segments from both chromosomes at same loci and exchange them with each other. This results in the exchange of genes between the two chromosomes. This is how the variation comes to place between offsprings of the same individuals. The crossing over results to form X shaped intersections between homologous pair of chromosomes which is called as chaismata. This phase occurs in pachytene phase and is visible in diplotene phase when the protein coat dissolves.
Answer:
The amount of CO2 found in the atmosphere varies over the course of a year. Much of this variation happens because of the role of plants in the carbon cycle. Respiration happens all the time, but dominates during the colder months of the year, resulting in higher CO2 levels in the atmosphere during those months.
Explanation:
Phylum is a principal taxonomic category that is ranked below the kingdom and above the class. If two organisms are in the same phylum, this means that they are also in the same kingdom. Each phylum is composed of one or more classes.
The deep sea vent organisms or benthic organisms normally live in dark conditions because of no penetration of sunlight. These organisms in order to colonize ocean surface must develop photo sensory receptors and should adapt to the light conditions along with variation in temperatures and pressure in ocean currents.
