The predominant hypothesis for why the animals needed some 3 billion years to evolve after the life first appeared on the planet is that the conditions were not right for them to appear.
The life on Earth has appeared much earlier that what we normally assume, and also it has not been evolving very quickly, but instead it has been a very slow and gradual process. The reason for that is that the living conditions on the Earth were much different than what are they now, or anytime from the Cambrian period until the present.
The surface was still pretty hot, and there was intense volcanic activity. The composition of the atmosphere was not suitable for animals to appear at all, and in fact it would have been toxic for them. The water too had chemicals in it that were not providing the right conditions for animals to evolve. It was only after the plants started to appear and managed to make lot of changes in the water, atmosphere, and land, than the animals were able to evolve and develop.
At the end of meiosis, there are FOUR cells with HALF the amount of DNA.
Meiosis is a kind of cell division that produces genetically different daughter cells. Unlike mitosis, which produces genetically identical cells, meiosis goes through 2 divisions that leads to 4 daughter cells.
In meiosis, the parent cell first duplicates all its genetic material, just like what they do in mitosis. Then it divides, leading 2 genetically identical daughter cells. Mitosis ends here, but in meiosis, the 2 cells divides themselves again, but without duplicating their DNA. This leads to the 4 daughter cells with only half of the number of chromosomes.
We call these cells haploid. They're usually common in gametes. For example, a normal body cell in human has 46 chromosome, but in the cells after meiosis, they only have 23.
Kinetic energy is the energy of motion :)
Potential energy is when the object is at rest, I believe
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 preferable word for the fill in the blanks will be - Acid rain.
Explanation:
<u>Acid rain</u> is produced by the interaction of water with sulfur dioxide and nitrogen dioxide; damages forests reduces crop yields and corrodes surfaces of buildings and statues; turns water in lakes and rivers acidic, harming fish and other aquatic species.
- Acid rain is mainly caused by air pollution such as the burning of industrial coal and other fossil fuels, etc.