Biological Evolution Questions in English

(B) Reproductive isolation is a mechanism that prevents two different species from interbreeding and producing fertile offspring. Therefore,two species are considered reproductively isolated if they are not interfertile,meaning they cannot successfully mate and produce viable,fertile offspring.

(D) Organic evolution is the process by which living organisms have changed and diversified over long periods of time.
Ecology is the study of the interactions between organisms and their environment.
Embryology is the study of the development of an embryo from the fertilization of the ovum to the fetus stage.
Spontaneous generation is an obsolete theory suggesting that living organisms can arise from non-living matter.

(A) Lamarck's theory is known as the Theory of Inheritance of Acquired Characters. Lamarckism includes four main factors:
$(i)$ Internal Vital Force: All living things and their component parts are continually increased due to an internal vital force.
$(ii)$ Effect of Environment and New Needs: The environment influences all types of organisms. Any change in the environment brings about changes in organisms,which gives rise to new needs.
$(iii)$ Use and Disuse of Organs: If an organ is constantly used,it becomes better developed,whereas the disuse of an organ results in its degeneration.
$(iv)$ Inheritance of Acquired Characters: Whatever characters an individual acquires during its lifetime due to internal vital forces,environmental effects,new needs,and the use or disuse of organs,are inherited (transmitted) to the next generations. After several generations,these variations accumulate to such an extent that they give rise to new species.
Objections to Lamarck's Theory:
$(i)$ Piercing of the pinna (external ear) and nose in women is never inherited by the next generation.
$(ii)$ $A$ wrestler's powerful muscles are not transmitted to their offspring.
$(iii)$ European ladies wore tight waist garments to keep their waists slender,but their offspring at the time of birth always had normal waists.
$(iv)$ Chinese women used to wear iron shoes to have small feet,but their children at the time of birth always had normal feet.

(A) The gradual accumulation of adaptations in response to a changing environment is the fundamental process of speciation. This concept forms the core of the 'Theory of Natural Selection' proposed by Charles Darwin, which explains how populations evolve over time to become better suited to their environment, eventually leading to the formation of new species.

(C) Organic evolution is the process by which living organisms have developed and diversified from earlier forms during the history of the Earth.
It involves the gradual change in the inherited characteristics of biological populations over successive generations.
Key processes include:
$1$. Anagenesis: The alteration of genetic properties within a single lineage over time.
$2$. Cladogenesis: The branching process where a single lineage splits into two or more distinct lineages.
Therefore,the concept describing the change of species over a long period is defined as Organic evolution.

(A) According to Darwin's theory of natural selection,new species evolve from ancestral forms through the gradual accumulation of favorable adaptations that allow organisms to survive and reproduce in a changing environment. This process occurs over long periods of time.

(C) It is difficult to find any two individuals that are exactly alike. Even the progeny of the same parents are not identical in all respects. These differences are known as variations.
Without variations,changes cannot occur,and there would be no possibility for evolution to take place.
Certain variations,once they appear in the parent generation,continue to be inherited by the progeny generation after generation,eventually leading to evolutionary change.

(D) Gradualism is the theory that evolutionary change occurs slowly and continuously over long periods of time.
In contrast,Punctuated equilibrium suggests that species remain stable for long periods,interrupted by brief periods of rapid evolutionary change.
Both theories are supported by evidence from the fossil record.

(B) Evolution is defined as the process of gradual change in organisms over time.
Progressive evolution refers to the development of organisms from simple,less specialized forms to more complex,highly specialized,and efficient forms.
This process involves the accumulation of adaptations that enhance the survival and complexity of the species.
Therefore,the transition from simple to complex organisms is termed as progressive evolution.

(B) Evolution is defined as the change in the allele frequencies of a population over time. While natural selection acts on individuals,the individual itself does not evolve. Evolution occurs at the level of the population,making the population the basic unit of evolution.

(A) During industrialization,the tree trunks became dark due to soot and smoke deposits.
Dark-winged (melanised) moths were able to camouflage themselves against the dark background,making them less visible to predators like birds.
In contrast,light-winged moths became conspicuous against the dark background and were easily preyed upon by birds.
Therefore,the dark-winged moths had a higher survival rate and became more abundant.
Both the Assertion and the Reason are correct,and the Reason provides the correct explanation for the Assertion.

(A) Sympatry is the condition where selection may produce ecotypes living in adjacent habitats within the same geographic area. This process leads to sympatric speciation,which is the formation of new species from a single population due to reproductive isolation,occurring without any geographical barriers.

(A) The case of $Biston$ $betularia$ (peppered moth) is a classic example of natural selection.
Before industrialization,the tree trunks were covered with white-colored lichens.
White-winged moths were better camouflaged against the white lichens and thus survived,while dark-colored moths were easily preyed upon by birds.
Therefore,before industrialization,there was a natural selection of white-winged moths.
After industrialization,the soot and smoke from factories killed the lichens and darkened the tree trunks.
This made the dark-winged moths better camouflaged,leading to their selection.
Option $A$ is incorrect because,before industrialization,the white-winged moths were favored,not the dark ones.

(C) The selection of resistant bacteria (due to the use of antibiotics) and industrial melanism (observed in the peppered moth, $Biston$ \text{ } $betularia$) are classic examples of natural selection.
In both cases, environmental pressures (antibiotics or industrial pollution) favor the survival and reproduction of individuals with advantageous traits (resistance or dark coloration), leading to a change in the population over time.
Therefore, these phenomena demonstrate how nature selects organisms that are better adapted to their environment.

(B) Industrial melanism is a classic example of $natural \text{ } selection$. Before the industrial revolution in England, light-colored moths were more abundant because they were camouflaged against light-colored lichens on tree trunks. After industrialization, soot covered the trees, making dark-colored moths better adapted to their environment as they were less visible to predators. This change in the environment led to the survival and reproduction of the dark-colored variant, demonstrating the process of $natural \text{ } selection$.

(D) divergent evolution.
Divergent evolution is the process by which two or more species evolve from a common ancestral species due to different environmental adaptations.
This process highlights the presence of common ancestry among the resulting species.