The kind of variation that must exist in a population that has a wide range of phenotypes is GENETIC VARIATION.
Genetic variation is started in a population's gene pools which contains all alleles. It is <span>is measured with allele frequency which are calculated by # of specific allele divided by total # of alleles.</span>
Answer:
Reinforcement favoring reproductive isolation is required for both parapatric and sympatric speciation.
Explanation:
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water at 273 K will absorb less environmental heat energy than ice at 273 K. Therefore, ice at 273 K is more effective in cooling than water at the same temperature.
Answer:
At low Ts= Hopanoids increase membrane fluidity
At higher Ts= Hopanoids reduce the membrane fluidity
Explanation:
Bacterial membranes lack cholesterol but have hopanoids. Hopanoids are synthesized from the same precursor as the steroid. The hopanoids also have five fused ring structures like that of cholesterol. The amphipathic nature of hopanoids allows them to maintain the membrane fluidity under low and higher temperature conditions.
When the temperatures are higher, the hopanoids serve to reduce the membrane fluidity by their ability to interact with polar heads and non-polar tails of the membrane phospholipids. At lower temperatures, hopanoids insert themselves between the non-polar tails of phospholipids to increase the membrane fluidity.
Answer:
H. prophase I → genetic recombination events take place
C. metaphase I → aligning of bivalents in the center of a spindle
B. anaphase I → separation of homologous chromosomes
F. telophase I → one haploid set of replicated chromosomes at each spindle pole
D. prophase II → shortest stage
G. metaphase II → aligning of monovalents in the center of a spindle
E. anaphase II → separation of sister chromatids
A. telophase II → one haploid set of unreplicated chromosomes at each spindle pole
Explanation:
Through the process of Meiosis, a diploid germ cell (2n) divides and originates four daughter cells with a haploid chromosome number (n). Each daughter cell has half of the chromosomes of the original one. Meiosis is completed in two phases. During the first phase, and after replication, occurs the chromosome´s reduction division. During the second phase, the cell suffers a new, not reductive division.
1. In the first phase, Meiosis I:
- Prophase I: Chromosomes condensate and became visible. Occurs crossing-over between homologous chromosomes. Crossin-over makes the daughter cells to be genetically different from the original one.
- Metaphase I: The pairs of homologous chromosomes randomly align in the equatorial plane.
- Anaphase I: occurs the independent separation of homologous chromosomes that migrate to opposite poles of the cell. This separation generates different chromosomal combinations in the daughter cells.
- Telophase I: Each of the homologous pairs chromosomes is already in the corresponding poles, and the nuclear membrane forms again in each pole.
2. In the second phase, Meiosis II:
- Prophase II: Chromosomes condensate again and become visible.
- Metaphase II: Chromosomes join the spindle apparatus and migrate to the equatorial plane, where they randomly line up. Sister chromatids are holden together until they reach the Anaphase.
- Anaphase II: Centromeres divide, chromatids get separated, and each of them goes forward an opposite cellular pole.
- Telophase II: Once in the poles, the chromosomes became lax again, and cytokinesis occurs.
