Answer:
The DNA molecule is a polymer of nucleotides. Each nucleotide is composed of a nitrogenous base, a five-carbon sugar (deoxyribose), and a phosphate group. There are four nitrogenous bases in DNA, two purines (adenine and guanine) and two pyrimidines (cytosine and thymine). A DNA molecule is composed of two strands.
Insect populations can develop resistance to insecticides over time. The evolution of resistance is associated with an increase in the frequency of adaptive genes in the population.
- In the case above described it is expected that a few mosquitoes in the population were resistant to DDT before it was ever used (Option a is correct).
- Dichlorodiphenyltrichloroethane (DDT) is a pesticide used in agriculture.
- After exposure to DDT, those individuals in the mosquito population that didn't carry gene variants (i.e., alleles) associated with the resistance to this pesticide died.
- Subsequently, insects having adaptive alleles associated with DDT resistance survived and reproduced, thereby increasing the frequency of adaptive genes/alleles in the population.
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Answer;
This is because most likely some time a ago there use to be Ammonites living there and as they died there, they got fossilized.
Explanation;
-Fossils of a marine animal called Ammonite are found in large numbers in the Kali Gandaki river in Nepal. Ammonites were sea animals having shells - either straight or coiled. When the Tethys sea disappeared, they were caught in the shale layers of clay and transformed into fossils. This is one of the proofs that the Himalayas were indeed once under water.
Cells are of two types: eukaryotic, which contain a nucleus, and prokaryotic, which do not. Prokaryotes are single-celled organisms, while eukaryotes can be either single-celled or multicellular.
