Answer:
'Gametes are formed through a process of cell division called meiosis. This two-step division process produces four haploid daughter cells. Haploid cells contain only one set of chromosomes. When the haploid male and female gametes unite in a process called fertilization, they form what is called a zygote.'
Explanation:
The variety of traits a species has best defines genetic diversity.
Ans.
Sickle-cell disorder shows defected red blood cells, due to mutation in gene that code for hemoglobin. The mutated genes for sickle-cell disease are found in higher percentage of sub-Saharan African population as it provides protection against malaria as compared to population of United States.
Malaria is common in sub-Saharan Africa region and there, natural selection favored gene for sickle cells, because it might be beneficial to people having sickle cell disease that makes them able to survive in such condition and transmit their genes to offspring.
On the other hand, in those Africans, who moved to United States, where malaria is uncommon or absent, natural selection favored normal, wild type genes, resulting in fewer people with defected sickle cell.
Thus, the evolutionary process behind this is 'natural selection.'
Excessive calorie intake during pregnancy can result in a fetus that has high birth weight. Pregnant women have indeed higher energy requirements but only by 300 calories daily. Eating an excessive amount of calories daily during pregnancy can lead to an increased weight gain that can result in an increased birth weight. Excessive weight gain during pregnancy can also endanger the progression of the pregnancy and the delivery of the baby.