The Answer is C~ More nitrogen gas became present in the atmosphere
Answer:
Alleles are recombined when gametes from different parents join together.
Explanation:
Genetic variation is increased by sexual reproduction in 3 main ways
1. Random mating - individual organisms reproduce with each other at random, meaning new combinations of DNA come together when fertilization occurs
2. Crossing over - during meiosis, when homologous chromosomes align, they can exchange genetic material by a process called crossing over, or homologous recombination. This means the alleles on each homologous chromosome are reshuffled, creating new combinations.
3. Independent assortment - When gametes are formed, a diploid cell duplicates its DNA and forms 4 haploid cells. Each of the homologous pair of chromosomes in the diploid align in the centre of the cell to be split into the gametes at each division. The orientation at which they line up is random, so every gamete gets a different selection of chromosomes (which themselves have been shuffled bt crossing over).
Only the 1st option (Alleles are recombined when gametes from different parents join together.) is correct. This represents the process of random mating, where new combinations of alleles are formed during fertilization between two individuals.
They evolved from cyanobacteria
Answer:
A diploid cell undergoes meiosis to produce one egg and 3 polar bodies with 23 chromosomes each.
Explanation:
During egg formation in the ovary, Primary oocyte (diploid) having 46 chromosomes undergoes meiosis I to form one secondary oocyte and one first polar body. Both the secondary oocyte and one polar body are haploid having 23 chromosomes. Both daughter cells then undergo meiosis II, the first polar body divides to give two polar bodies and the secondary oocyte divides by meiosis II to form one ovum. Therefore, during egg formation in the reproductive system, a diploid cell (a primary oocyte) undergoes meiosis to produce one egg and 3 polar bodies with 23 chromosomes each.
