6 Most VSAQ’s of Organic Evolution Chapter in Inter 2nd Year Zoology (TS/AP)

2 Marks

VSAQ-1 : What are Panspermia?

Panspermia is a scientific hypothesis proposing that life may have originated elsewhere in the universe and then spread to celestial bodies like Earth through spores or microorganisms. This theory suggests that life could exist in various parts of the cosmos, possibly transported by natural processes such as meteoroid impacts, radiation pressure, or interstellar dust clouds. While an intriguing idea, it remains a scientific hypothesis requiring additional research and evidence to substantiate its validity.

Connecting links are organisms that exhibit characteristics of two different groups, providing evidence for evolutionary relationships between those groups. Some examples of connecting links are:

  1. Eusthenopteron: This fish-like organism links fishes and amphibians, displaying transitional skeletal features.
  2. Seymouria: A fossil species serving as a link between amphibians and reptiles, with shared characteristics.
  3. Archaeopteryx: An ancient bird-like dinosaur acting as a link between reptiles and birds, showing features of both groups.
  4. Cynognathus: An extinct species serving as a connecting link between reptiles and mammals, bridging the gap with its unique features.

Studying these connecting links aids in understanding the gradual changes and adaptations that occurred during the evolution of different organisms and the development of various groups in the tree of life.

VSAQ-3 : Define Biogenetic law, giving an example.

Biogenetic law, also known as the Theory of Recapitulation, posits that the development of an organism during its embryonic and early stages mirrors the evolutionary history of its ancestors. In other words, an organism’s ontogeny (developmental history) reflects its phylogeny (evolutionary history).

Two examples of the Biogenetic law are

  1. Caterpillar of a butterfly: In its early development, a caterpillar displays similarities to an annelid (segmented worm) ancestor, reflecting the shared evolutionary history between butterflies and segmented worms.
  2. Tadpole larva of a frog: The tadpole larva exhibits characteristics akin to a fish with a tail, gills, and a two-chambered heart, mirroring the evolutionary history of amphibians and their common ancestry with fish.

VSAQ-4 : Define atavism with an example.

Atavism is the phenomenon where ancestral or primitive traits reappear in an organism, even though they are not commonly expressed in the species anymore.

Example: A human baby born with a tail is an instance of atavism. Tails were more prevalent in our distant ancestors, like some primates. The presence of a tail in a human baby is a rare occurrence but can be considered an atavistic trait, offering insight into our evolutionary history.

VSAQ-5 : Cite two examples to disprove Lamarck’s inheritance of acquired characters.

Lamarck’s theory of inheritance of acquired characters suggests that traits acquired by an organism during its lifetime can be passed on to its offspring. However, there are several examples that disprove this theory:

Example 1: Well-developed muscles of athletes are not inherited by their children. Despite the intense physical training and development of muscles in athletes, their offspring do not inherit these well-developed muscles automatically. Muscular development in offspring depends on their own genetic makeup and not on the acquired characteristics of their parents.

Example 2: In some cultures, it is a common practice to pierce the ear pinnae for ornamental purposes. However, this acquired characteristic of having pierced ears is not passed on to the children of individuals who have their ears pierced. The piercing of ears does not influence the genetic makeup of future generations, and children are not born with pierced ears as a heritable trait.

VSAQ-6 : What is meant by genetic load? Give an example.

Genetic load refers to the presence of harmful or deleterious genes within a population. These genes can cause various genetic disorders or health issues in individuals who inherit them.

Example: Sickle cell anaemia is an example of genetic load. It is a genetic disorder caused by a mutation in the gene responsible for producing hemoglobin, a protein found in red blood cells. People who inherit two copies of the defective gene (homozygous condition) suffer from sickle cell anaemia and may experience severe health problems, including anemia and pain.