Question

Despite being universally accepted within the scientific community for over 150 years, the theory of evolution remains poorly understood by the public in some cases. Imagine that you are conversing with a friend who has some misconceptions about evolution.

describe how you would explain evolution in brief, simple terms to a non-scientist. What does “evolution” mean? How does it work? What is one concrete example that you feel provides strong empirical evidence of evolution.

Answer 1

Ans.

• In the simplest terms, evolution can be defined as the changes in the species over time i.e. 'descent with modification'.
• It can be defined as a modifictaion in the genetic makeup of a population over a period of time.
• In the biology, evolution is the key unifying and one of the most basic principle.
• Based on the scales, there are two types of evolution, as described by biologists ;

1. Macroevolution - large scale changes taking place over an extended period of times eg. formation of a new species.
2. Microevolution - short scale changes happening over a short period of times eg. changes affecting only a few genes.

Both of the above processes, in reality, are a part but not type of evolution, just differing only in terms of time scale.

How evolution works ?

There are many ways through which evolution can show it's effects.

Major mechanisms through which evolution shows it's effects are;

1). Mutation -

• It is defined as the alteration in genetic code resulting from the errors occuring during the process of DNA replication.
• Mutation may either be beneficial for an organism or may kill them.
• Some organisms may gain a beneficial characteristic helping them in survival or may impair their development and cause death.
• An example of a mutation is the ability of human to drink milk as the enzyme necessary for digestion of milk disappear from human bodies after some times when they stop breastfeeding.

2). Gene flow -

• It is an other important mechanism of evolution.
• This phenomenon occur upon movement or migration of individuals to the other habitats and spreading of their genetic materials in new places.
• For example, suppose there are two populations which have organisms with characteristics opposite to each other.
• If the resources in the habitat of one population became scarce so, they started to migrate in the habitat of the other population.
• These two different groups may began to reproduce, eventually and may result in the formation of new species over some times.

3). Genetic drift -

• It is defined as the way by which gene pool is distributed within a particular organism's community.
• Offsprings of some orgaisms may be more likely to survive then the others.
• It is a common phenomenon of each population.
• The offsprings with better survival skills will transfer their genetic material more likely to the upcoming generations and may change the gene pool.
• Sometimes, genetic drift may result in the extinction of a population if no new genes are added to the gene pool and only a particular gene is surviving.

4). Natural selection -

• It is a classic mechanism of evolution, the one about which Charles Darwin wrote in his theory.
• This process results in the selection of the characteristics of an organism that are most suitable and favorible in the given current environment.
• For example, if in the population of different colors organism, a predator is attracted more toward one color prey then the others, so the organisms with less attractive colors are more likely to survive and transfer their genes to the offsprings.

Evidence of evolution -

Fossils record -

• Fossils can be defined as preserved remains of the organisms which lived previously or their traces which dates ways back to the past.
• The fossils collected by the humans provide unique insights into the process of evolution over a long periods of time.
• Strata are the rock layers which contained the fossils.
• This layer of rocks indicates towards something like a timeline with top layers being newer and layers towards the bottom being older.
• Fossils present at the same site in different layer of strata can be numbered according to their positions, and reference strata having unique characteristics can be used for comparing the fossils age across the locations.
• Radiometric dating may also be used to date fossils which measures the radioactive decay of several components.
• Existence of new-extinct species can be documented by the fossils as a prove of different organisms living on Earth during different time periods of the history of planet.
• Evolutionary histories of many of the present day species can also be construct with the help of fossils.
• For example, scientists were able to recreate a large branching 'family tree' for horses and their relatives which have now being extinct, by studying the fossils of the horse lineage.