Chapter 7: Evolution

Ans: Louis Pasteur used a sterile flask and another one that was open to the air. New yeast organisms were developed in a flask that was open to air, but in the sterilized flask yeast did not produce new organisms. This experiment contributed to the rejection of the spontaneous generation theory. Miller’s later experiment, on the other hand, demonstrated that organic molecules may evolve from inorganic molecules, leading to the origin of life. Therefore, we can correct the statement that the first form of life could have arisen from pre-existing non-living organic molecules. 

Ans: Natural disasters such as earthquakes can result in the extinction of species. A majority of scientists believe that a meteor struck the earth, causing widespread destruction and the extinction of dinosaurs.

Ans: Nascent oxygen is highly reactive. It can react easily and cause a reaction with a variety of compounds, including DNA and proteins found in cells of aerobic life forms. This may result in Mutations and unfavorable metabolic changes.

Ans: Variation continues to appear in each generation. However, because nature may not support such variations, most of them are not retained by the organism. When a new recombinant passes the test of natural selection, then only it is inherited in species through generation to generation. As a result, creation and the presence of variation can be considered to be directionless, but natural selection and adaptation are directional.

Ans: In England before industrialization, the white-winged moths were able to thrive because whitish lichens and moss flourished on tree trunks. White-winged moths blended very well and therefore had better chances of survival against the whitish background. But when the industrial revolution started the tree trunks turned dark, Lichens and mosses did not survive. As a result, the population of white-winged moths decreased and the population of white-winged moths increased. Thus, the evolution of white-winged moth reversed due to industrialization. 

Ans: It is controversial whether evolution and natural selection are processes in and of themselves, or if they are the end result or consequence of other processes. When we talk about the success of life on Earth, we consider evolution and natural selection to be processed. However, when discussing how life arose from primitive beginnings, evolution and natural selection appear to be the outcomes of other processes. This is still a debatable topic in the scientific community. 

Ans: The allele frequency in population can be affected by the following factors:

1. Mutation: Mutation is a sudden inheritable change in the DNA, it leads to the formation of new species and therefore changes in allelic frequency.

2. Natural Selection: Natural selection theory that states, Nature only selects the fittest organisms which survive in changed environmental conditions.

3. Genetic Recombination: The new organism or traits produced that differ from parents is called genetic recombination.

Ans:  Yes, I agree. Gene flow occurs across generations. The project known as  Human Genome Project has used specific genes/chromosomes and mitochondrial DNA to trace the evolutionary history and migratory patterns of humans. Therefore with the help of HGP by studying specific allele frequencies, we can predict the human migratory patterns in prehistory and history. 

Ans: Race: Race is a group of people that share similar and distinct physical characteristics. Members of different races of the same species can interbreed.

Breed: Breed is a group of animals that are similar in physical appearance.

Cultivars: Cultivar is a selected group of plants that can be propagated through vegetative parts.

Variety: Variety is a taxonomic category that ranks below species level in the plant kingdom.

Ans: The “survival of the fittest” means the organisms with suitable and useful adaptations survive and reproduce in the varied environmental conditions that are known to be fit.