Brain loses 5 to 10% of its weight between the
ages of 20 and 90. One study found that the volume of the brain was 15% less in
older adults than in younger adults. On average, the brain loses 5% to 10% of
its weight between the ages of 20 and 90 years; brain volume also decreases.
positive feedback could be contractions(as painful as it may seem, its true) in child birth and the ripening of fruit.
negative feedback include the regulation of blood glucose levels and osmoregulation
Answer:
Genetic drift is simply a change in the frequency of alleles in a population.
Like shown in the comic A, there are different genes present on chromosomes. All of these genes are made up of a pair of alleles. These alleles determine the genotype and the resulting phenotype of an organism.
If none of the alleles is favored by the environment, then a population will have equal no.of all the variant forms of a trait. Like shown in the comic B, both the green and the grey animals are favored equally.
But if natural selection occurs and one form of the allele variant is favored, then a genetic drift will occur. Most of the organisms will have the alleles which are favored by the environment. Like shown in Comic C, where the grey alleles are favored more than the green alleles.
C) To gather info about the natural world, to explain natural phenomena, and allow reasonable predictions of future events