Two organisms occupying a particular geographical area (say desert) show similar adaptive strategies. Taking examples, describe the phenomenon.
This phenomenon indicated in the question is convergent evolution where by organisms, not closely related, evolve similar traits independently as a result of adaptation to similar environment. e.g.,
(i) Streamlined shape of sharks and dolphins. The former is a fish, while dolphin is a mammal, but both of them depend on swift movement through the water, so a streamlined shape is essential. Thus, it is the similar habitat that resulted in selection of similar adaptive features in different groups of organisms, but toward the same function.
(ii) Spines (modified leaves) and thorns (modified stems), both look similar and provide protection to the plant, but the plants to which they belong are distantly related.
We are told that evolution is a continuing phenomenon for all living things. Are humans also evolving? Justify your answer.
New research suggests that despite modern technology and industrialisation, 'humans continue to evolve'. In the last 10,000 years or so, the pace of our evolution has speeded up 100 times creating more mutations in our genes and hence, greater natural selection.
Some clues that show humans are evolving are
(i) Lactose Tolerance Historically the gene that regulated human's ability to digest lactose was shut down as infants are weaned off of their mother's breast milk. However, adult human in regions of Africa and Northern Europe developed the ability to tolerate lactose in their diets as recent as 5,000 or 6,000 years ago due to mutations.
(ii) Wisdom Teeth Our ancestors had much bigger jaws than we do to lactose their eating habits. Today our jaws are much smaller and wisdom teeth are often impacted estimates say that they will disappear in the coming population.
Yes, had Darwin been aware of Mendel's work, he would have been able to explain the origin of variations. Darwins observation of different forms of an individual in a population could be related to the presence of different forms of alleles of a gene.
The gene express as the most adaptive traits are selected naturally and become more abundant than those that are expressed as less adaptive traits.
Over the time, the accumulation of these traits might change the species to an extent that it develops into a new one and adapted to the specific environment.