In order for plants to grow and thrive on Earth, they need to have the ability to reproduce. Plants are different from vertebrate animals because they have the ability to reproduce two ways.
Asexual reproduction uses mitosis, where cells copy their genetic material and then split into two identical cells. Plants reproduced using asexual reproduction are genetically identical and have the exact same DNA. As mitosis begins, the duplicated chromosomes become attached at a point called the centromere and form pairs. Once attached, the chromosomes line up in the middle of the cell. A special protein splits the pairs in half and the chromosomes are pulled to opposite sides of the cell. Eventually, the cell itself divides into two identical cells, which are called the daughter cells of mitosis.
Sexual reproduction, in both plants and animals, involves the creation of sex cells through meiosis. Meiosis is a process in which one parent cell with the normal number of chromosomes splits into four cells, called sex cells. Each sex cell has half the number of chromosomes needed for a complete organism. When a male and a female sex cell combine, they create new organism that has the required number of chromosomes to grow and develop.
During the first phase of meiosis, pairs of duplicated chromosomes attach at the centromere. Then, each chromosome pair attaches with another to form clusters of four chromosomes. The formation of these clusters allows chromosomes to form connections called crossovers. Portions of the chromosomes become swapped when these crossovers occur.
During the first cell division in meiosis, the clusters of four separate and the cell splits. Each daughter cell contains paired chromosomes. These daughter cells then split again, as part of a process called meiosis II. This time, the chromosome pairs are separated. The final division creates four new daughter cells.