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Mitosis is simply described as having four stages—prophase, metaphase, anaphase, and telophase; the steps follow one another without interruption. The entire four-stage division process averages about one hour in duration, and the period between cell divisions, called interphase or interkinesis, varies greatly but is considerably longer.
During interphase the chromosomes are dispersed in the nucleus and appear as a network of long, thin threads or filaments, called the chromatin. At some point before prophase begins, the chromosomes replicate themselves to form pairs of identical sister chromosomes, or chromatids; the deoxyribose nucleic acid (DNA) of the chromosomes is synthesized only during interphase, not while mitosis is in process.
During prophase the two chromatids remain attached to one another at a region called the centromere, but each contracts into a compact tightly coiled body; the nucleolus and, in most cases, the nuclear envelope break down and disappear. Also during prophase the spindle begins to form. In animal cells the centrioles separate and move apart, and radiating bundles of fibers, called asters, appear around them. Some sets of fiber run from one centriole to the other; these are the spindle fibers. In plant cells the spindle forms without centrioles.
During metaphase the chromosomes congregate at a plane midway between the two ends to which the spindle tapers. This is called the equatorial plane and marks the point where the whole cell will divide when nuclear division is completed; the ends of the spindle are the poles to which the chromatids will migrate. The chromatids are attached to the spindle fibers at the centromeres.
During anaphase the two chromatids of each chromosome separate and move to opposite poles, as if pulled along the spindle fibers by the centromeres. During telophase new nuclear envelopes form around the two groups of daughter chromosomes (as they are now called), the new nucleoli begin to appear, and eventually, as the formation of the two daughter nuclei is completed, the spindle fibers disappear. The chromosomes uncoil to assume their dispersed distribution within the interphased nucleus. Cytokinesis, which may begin before or after mitosis is completed, finally separates the daughter nuclei into two new individual daughter cells.
A considerable variance in the degree and timing of these stages exists across species, and cells can be classified by their mitotic characteristics. Despite the relative ease of observation of the physical stages of mitosis under the microscope (primarily because the chromosomes stain readily when in their coiled state), the exact chemical and kinetic nature of mitosis is not yet fully understood. For instance, the spindle has been determined to consist largely of thin, elongate tubules called microtubules, but their functions have yet to be understood.
Answer:
The 2 types of behavioral adaptation are migration, and hibernation.
Explanation:
Adaptation of animal is the fitness towards its environment. If an animal can't adapt, it will perish with time. Adaptation may be genetic or acquired. But basically, adaptation is 2 types - physical adaptation, and behavioral adaptation.
Physical adaptation includes the coloring of the body, camouflage activity of an organism. The behavioral adaptation is the respond of the organisms to their habitat. This includes hibernation, estivation, migration, etc.
Some animals are affected by the temperature difference of the environment. Therefore, they adopt some methods to survive in extreme temperatures.
The cold-blooded like amphibians hibernate during winter. They undergo a long sleep during cold weather and become active in summer. Similarly some animals like desert lizard active in the morning. When the temperature increase they burrow themselves under the ground. This is called estivation.
Birds migrate during the adverse season i.e. in winter. They temporarily go to a different place to spend the cold month and return during the advent of summer. This is one type of behavioral adaptation. They also migrate for better breeding ground and food.
Some fishes also migrate for breeding and food.
A. The populations evolved separately because they were temporally isolated.
B. The populations evolved separately because they were behaviorally isolated.
C. The populations evolved separately because they were geographically isolated.
D. The populations evolved separately because they were reproductively isolated.
Answer: Option C
Explanation:
Geographical isolation is a term that refers to a population of plants or animals that are separated from mating with the other organisms of the same species.
This is due to the separation of the organism because they are geographically isolated from one another. Here some members of the same species are isolated from the other members of the same species.
The eastern and western salamanders are isolated by each other because of geographical isolation.