Natural selection is an idea that Charles Darwin came up with.
It attempts to describe how animals and plants evolved by using nature as the determiner of who survives. For example, if there is a fast cheetah population and a slow cheetah population in Africa, the slow cheetah population will eventually die out due to them not being able to catch prey to survive. The fast cheetah had the desirable traits necessary for survival in this location. Only the strong survive is helpful to remember when dealing with natural selection.
Answer:
B (Metaphase I)
Explanation:
Meiosis is one of the two types of cell divisions that results in 4 daughter cells (gametes) with each having half the number of chromosomes as the parent cell. During meiosis, cell division occurs twice because before the separation of two halves of a duplicated chromosome called sister chromatids, there still need to be separation of homologous pairs, which is a similar but non-identical pair of chromosome received from both parents. Hence, meiosis occurs in a two step division process; meiosis I and meiosis II.
During Prophase I, which is the first stage of meiosis I, homologous chromosomes pair up side by side to form a structure called TETRAD or BIVALENT and likely undergo crossing over( when segments of homologous chromosomes get broken and refixed interchangeably).
After crossing over, the spindle fibres (from the centrosomes) begin to attach to the centromeres of each chromosomes and move them towards the center of the cell called METAPHASE PLATE. Hence, they become aligned on the equator towards either side of the pole. Each chromosome attaches to microtubules from one pole of the spindle and the two homologues of a pair bind to microtubules from opposite poles. Hence, in Metaphase I, homologous pairs, not individual chromosomes, line up at the Metaphase plate/equator for separation.
The orientation of the line up of homologous chromosomes determines which chromosomes enter into the same cell i.e. the alignment of chromosomes towards the same pole determines which chromosomes enter into the same cell to form the genetic composition of gametes. In an organism with two sets of chromosomes (diploid), there are four possible combinations in which chromosomes are arranged in the metaphase plate, resulting in differences in chromosomal distribution in daughter cells/gametes, the process of independent assortment
No baby has been born without an X chromosome
