<span>4. Species
</span><span>Allopatric speciation is were a single species has been separated so long they have both evolved slightly in different "directions" that prevent them from breeding after being reintroduced.</span>
Answer:
Stem cells are divided into 2 main forms. They are embryonic stem cells and adult stem cells. Embryonic stem cells.
Answer:
A lot of factors cause genetic variation in a population. The root of all genetic variation is mutations, which occur randomly.
A lot of genetic variation in fact results during meiosis, the process by which gametes (sex/reproductive cells) are formed. The 3 main ways are crossing over, independent assortment of chromosomes, and random fertilization. Crossing over occurs during Prophase I of meiosis, in which genetic material is exchanged between nonsister chromatids of homologous chromosomes. Independent assortment refers to the following: When cells divide during meiosis, homologous chromosomes are randomly distributed during anaphase I, separating and segregating independently of each other. Random fertilization is where any sperm can fertilize any egg cell. The many combinations of eggs and sperms mean variation.
Another source of genetic variation include gene flow. Gene flow is where populations have their members enter other populations (migration), influencing the gene pool of populations. This source is more controversial, however.
Random mating can also increase genetic variation.
Answer:
B) neurons have stable, relatively unchanging internal environments.
Explanation:
Rough endoplasmic reticulum (RER) is studded with ribosomes which in turn serve as the site for protein synthesis. A cell with an extensive network of rough endoplasmic reticulum has higher rates of protein synthesis. Mitochondria are the powerhouse of cells and serve as the site for aerobic cellular respiration. A large number of ATP molecules are produced in mitochondria. Therefore, a cell with relatively many mitochondria appears to have a higher demand for ATP and higher consumption of oxygen.
A cell with higher rates of consumption of ATP and protein synthesis should be functionally active. The charge across the membrane and the internal concentration of ions such as Na+, K+ of a neuron keep on changing during the conduction of nerve impulse. Therefore, the presence of many mitochondria and RER does not indicate that the neurons maintain relatively constant internal conditions.
