Assertion (A): Evolutionary biology supports the idea of common
ancestry for all living organisms.
Reason (R): Evidence from comparative anatomy, embryology, and
molecular biology shows similarities among different species.
Answer: (A) Both A and R are true, and R is the correct
explanation of A.
Explanation: The common ancestry concept is supported by
evidence from comparative anatomy (e.g., homologous structures), embryology, and
molecular biology (e.g., genetic similarities).
Assertion (A): Darwin's theory of evolution is based on natural
selection.
Reason (R): Organisms with beneficial traits survive and
reproduce more successfully than those without.
Answer: (A) Both A and R are true, and R is the correct
explanation of A.
Explanation: Natural selection, as proposed by Darwin, explains
that advantageous traits increase an organism's chances of survival and
reproduction.
Assertion (A): The modern synthetic theory of evolution
combines Mendelian genetics with Darwinian natural selection.
Reason (R): This theory integrates the mechanisms of gene
inheritance with the process of natural selection.
Answer: (A) Both A and R are true, and R is the correct
explanation of A.
Explanation: The modern synthetic theory incorporates genetics
into Darwin’s natural selection, explaining how genetic variation drives
evolution.
Assertion (A): The concept of "survival of the fittest" is
central to Darwin’s theory.
Reason (R): Fitness refers to the ability to survive and
reproduce in a particular environment.
Answer: (A) Both A and R are true, and R is the correct
explanation of A.
Explanation: "Survival of the fittest" means that organisms
best adapted to their environment are more likely to survive and reproduce.
Assertion (A): Evolution can occur at both the genetic and
phenotypic levels.
Reason (R): Genetic changes result in phenotypic variations,
which can be acted upon by natural selection.
Answer: (A) Both A and R are true, and R is the correct
explanation of A.
Explanation: Evolution involves genetic changes (mutations,
genetic drift) that lead to phenotypic changes, which can affect an organism’s
survival.
Assertion (A): Lamarck proposed the theory of inheritance of
acquired characteristics.
Reason (R): Lamarck believed that characteristics acquired
during an organism’s lifetime could be passed on to offspring.
Answer: (A) Both A and R are true, and R is the correct
explanation of A.
Explanation: Lamarck’s theory suggested that traits acquired by
an organism in its lifetime (e.g., a giraffe stretching its neck) could be
inherited by its offspring.
Assertion (A): Darwin’s finches on the Galapagos Islands are an
example of adaptive radiation.
Reason (R): Adaptive radiation occurs when species rapidly
evolve to occupy different ecological niches.
Answer: (A) Both A and R are true, and R is the correct
explanation of A.
Explanation: The finches evolved distinct beak shapes to
exploit different food sources, illustrating adaptive radiation.
Assertion (A): Artificial selection involves human intervention
in the breeding of organisms.
Reason (R): In artificial selection, humans select individuals
with desirable traits to reproduce, influencing evolutionary changes.
Answer: (A) Both A and R are true, and R is the correct
explanation of A.
Explanation: Artificial selection, such as breeding dogs for
specific traits, results in genetic changes influenced by human choices.
Assertion (A): The fossil record provides evidence for
evolution.
Reason (R): Fossils show transitional forms that link different
species and indicate changes over time.
Answer: (A) Both A and R are true, and R is the correct
explanation of A.
Explanation: Fossils provide a historical record of life on
Earth, showing how species have evolved over time.
Assertion (A): Homologous structures provide evidence for
common ancestry.
Reason (R): Homologous structures have similar origin but may
have different functions in different species.
Answer: (A) Both A and R are true, and R is the correct
explanation of A.
Explanation: Homologous structures, such as the forelimbs of
humans, bats, and whales, suggest common ancestry despite differing functions.
Assertion (A): Analogous structures are the result of
convergent evolution.
Reason (R): Analogous structures have different origins but
serve similar functions due to similar environmental pressures.
Answer: (A) Both A and R are true, and R is the correct
explanation of A.
Explanation: Convergent evolution leads to similar traits in
unrelated species due to similar ecological demands.
Assertion (A): The Hardy-Weinberg equilibrium assumes no
mutation in a population.
Reason (R): Mutations introduce new genetic variation,
disrupting the equilibrium.
Answer: (A) Both A and R are true, and R is the correct
explanation of A.
Explanation: Mutations alter allele frequencies, violating the
assumption of no mutation in the Hardy-Weinberg model.
Assertion (A): Gene flow can introduce new alleles into a
population.
Reason (R): Gene flow occurs when individuals from different
populations interbreed, transferring genetic material.
Answer: (A) Both A and R are true, and R is the correct
explanation of A.
Explanation: Gene flow leads to the mixing of genetic material
between populations, thereby increasing genetic diversity.
Assertion (A): Genetic drift is more pronounced in small
populations.
Reason (R): In small populations, chance events can
significantly affect allele frequencies.
Answer: (A) Both A and R are true, and R is the correct
explanation of A.
Explanation: In small populations, random changes can lead to
the loss or fixation of alleles more easily than in larger populations.
Assertion (A): Natural selection leads to the survival of the
fittest.
Reason (R): "Fitness" refers to the ability to survive and
reproduce successfully in a specific environment.
Answer: (A) Both A and R are true, and R is the correct
explanation of A.
Explanation: Natural selection favors individuals with traits
that enhance survival and reproduction, thus increasing their fitness.
Assertion (A): Speciation can occur through geographical
isolation.
Reason (R): When populations become geographically isolated,
they can evolve independently and eventually become separate species.
Answer: (A) Both A and R are true, and R is the correct
explanation of A.
Explanation: Geographic isolation prevents gene flow between
populations, leading to divergent evolution and speciation.
Assertion (A): Sympatric speciation occurs without geographical
barriers.
Reason (R): Reproductive isolation within a population leads to
speciation in the same geographical area.
Answer: (A) Both A and R are true, and R is the correct
explanation of A.
Explanation: Sympatric speciation can occur due to factors like
behavioral isolation or ecological differences within the same geographical
location.
Assertion (A): Coevolution occurs when two species exert
selective pressures on each other.
Reason (R): Coevolution can lead to reciprocal adaptations
between interacting species.
Answer: (A) Both A and R are true, and R is the correct
explanation of A.
Explanation: Coevolution involves mutual evolutionary changes
between interacting species, such as plants and their pollinators.
Assertion (A): Punctuated equilibrium suggests that evolution
occurs in rapid bursts followed by periods of stability.
Reason (R): This pattern contrasts with the gradual evolution
proposed by Darwin.
Answer: (A) Both A and R are true, and R is the correct
explanation of A.
Explanation: Punctuated equilibrium suggests that species
experience rapid changes during brief periods of evolutionary change, followed
by long periods of stasis.
Assertion (A): Fossils of transitional forms provide evidence
for the gradual nature of evolution.
Reason (R): Transitional fossils show intermediate traits
between ancestral and descendant species.
Answer: (A) Both A and R are true, and R is the correct
explanation of A.
Explanation: Transitional fossils, like Archaeopteryx, provide
clear evidence of gradual evolutionary changes.
Assertion (A): Natural selection does not work on individual
organisms.
Reason (R): Evolutionary changes occur at the population level,
not within a single individual.
Answer: (A) Both A and R are true, and R is the correct
explanation of A.
Explanation: Natural selection works on genetic variation
within a population, not on the traits of an individual.
Assertion (A): The bottleneck effect is a form of genetic
drift.
Reason (R): A population that is reduced in size by a
catastrophic event may lose genetic diversity.
Answer: (A) Both A and R are true, and R is the correct
explanation of A.
Explanation: The bottleneck effect reduces the size of a
population, and the surviving individuals may have limited genetic variation,
impacting the gene pool.
Assertion (A): Evolutionary adaptations are the result of
natural selection acting on genetic variation.
Reason (R): Organisms with advantageous traits have a better
chance of surviving and reproducing.
Answer: (A) Both A and R are true, and R is the correct
explanation of A.
Explanation: Natural selection favors beneficial genetic
variations, leading to evolutionary adaptations in a population.
Assertion (A): Artificial selection involves human control over
the breeding of organisms.
Reason (R): Humans select specific traits to be passed on to
future generations, such as in crops and livestock.
Answer: (A) Both A and R are true, and R is the correct
explanation of A.
Explanation: In artificial selection, humans deliberately
choose individuals with desired traits to reproduce, influencing the traits in
future generations.
Assertion (A): Genetic mutations introduce new genetic
variations into a population.
Reason (R): Mutations can produce new alleles, some of which
may be beneficial for survival.
Answer: (A) Both A and R are true, and R is the correct
explanation of A.
Explanation: Mutations are random changes in the genetic
material, introducing new alleles that may affect an organism's survival and
reproduction.
Assertion (A): Homologous structures indicate common ancestry.
Reason (R): Homologous structures are derived from a common
evolutionary origin, even if they perform different functions.
Answer: (A) Both A and R are true, and R is the correct
explanation of A.
Explanation: Homologous structures, like the forelimbs of
vertebrates, share a common anatomical origin but may serve different functions,
indicating common ancestry.
Assertion (A): The founder effect is a form of genetic drift.
Reason (R): A small group of individuals starting a new
population may carry a limited genetic pool, leading to reduced genetic
diversity.
Answer: (A) Both A and R are true, and R is the correct
explanation of A.
Explanation: The founder effect occurs when a small group of
individuals from a population starts a new population with limited genetic
variation.
Assertion (A): Genetic drift has a greater effect in small
populations.
Reason (R): In small populations, random fluctuations in allele
frequencies can have a more significant impact.
Answer: (A) Both A and R are true, and R is the correct
explanation of A.
Explanation: In smaller populations, chance events can lead to
the loss or fixation of alleles more rapidly, which is the essence of genetic
drift.
Assertion (A): Evolution can be studied through the analysis of
molecular data.
Reason (R): Molecular biology provides evidence for
evolutionary relationships by comparing DNA, RNA, and protein sequences.
Answer: (A) Both A and R are true, and R is the correct
explanation of A.
Explanation: Molecular evidence, such as genetic similarities,
provides clear insights into the evolutionary relationships between species.
Assertion (A): Evolutionary changes are irreversible.
Reason (R): Once an evolutionary trait has emerged, it cannot
be undone.
Answer: (B) A is true, but R is false.
Explanation: Evolutionary changes can be reversed, as seen in
some cases of convergent evolution or loss of traits in species.
Assertion (A): Adaptive radiation can lead to the rapid
formation of new species.
Reason (R): When organisms occupy different ecological niches,
they may evolve into distinct species in a short period.
Answer: (A) Both A and R are true, and R is the correct
explanation of A.
Explanation: Adaptive radiation occurs when species rapidly
diversify to exploit different environmental resources, leading to the formation
of new species.
Assertion (A): The Theory of Evolution suggests that organisms
evolve over time in response to environmental pressures.
Reason (R): Organisms with favorable traits are more likely to
survive and reproduce, passing those traits to the next generation.
Answer: (A) Both A and R are true, and R is the correct
explanation of A.
Explanation: Natural selection, a central mechanism in
evolution, ensures that favorable traits increase in frequency in a population
over time.
Assertion (A): Variation in a population is necessary for
natural selection to occur.
Reason (R): Without genetic variation, all individuals in a
population would be equally suited to the environment, and no selection would
occur.
Answer: (A) Both A and R are true, and R is the correct
explanation of A.
Explanation: Genetic variation provides the raw material for
natural selection to act upon, allowing advantageous traits to spread in the
population.
Assertion (A): Coevolution can occur between species that
interact closely with each other.
Reason (R): In coevolution, two species influence each other's
evolutionary development through reciprocal selective pressures.
Answer: (A) Both A and R are true, and R is the correct
explanation of A.
Explanation: Coevolution leads to reciprocal adaptations
between interacting species, like the relationship between predators and prey,
or pollinators and flowers.
Assertion (A): Evolution can be observed directly in
populations over short periods.
Reason (R): Some populations, like bacteria, evolve rapidly due
to short generation times.
Answer: (A) Both A and R are true, and R is the correct
explanation of A.
Explanation: Rapid reproduction in organisms like bacteria
allows for observable evolutionary changes in relatively short timeframes.
Assertion (A): Speciation can be driven by changes in habitat
or behavior.
Reason (R): Changes in ecological niches or mating behaviors
can lead to reproductive isolation, a key factor in speciation.
Answer: (A) Both A and R are true, and R is the correct
explanation of A.
Explanation: Habitat or behavioral changes can cause
reproductive isolation, leading to the emergence of new species.
Assertion (A): Evolution occurs at the population level, not at
the individual level.
Reason (R): Individuals do not evolve; rather, genetic changes
accumulate in populations over time.
Answer: (A) Both A and R are true, and R is the correct
explanation of A.
Explanation: Evolution occurs through genetic changes in
populations, not in individuals.
Assertion (A): Evolutionary processes are random.
Reason (R): Mutations occur randomly and do not predictably
lead to beneficial traits.
Answer: (B) A is false, but R is true.
Explanation: While mutations are random, natural selection is a
non-random process that favors beneficial mutations, leading to evolution.
Assertion (A): Mutations are the ultimate source of genetic
variation.
Reason (R): Mutations introduce new genetic material that can
create new traits in a population.
Answer: (A) Both A and R are true, and R is the correct
explanation of A.
Explanation: Mutations create new alleles, providing the
genetic diversity on which natural selection can act.
Assertion (A): Evolution is a slow and gradual process.
Reason (R): Most evolutionary changes occur over millions of
years.
Answer: (A) Both A and R are true, and R is the correct
explanation of A.
Explanation: Evolution typically occurs over long timescales,
with gradual changes accumulating within populations.
Assertion (A): Evidence from molecular biology supports the
theory of evolution.
Reason (R): Similarities in DNA and protein sequences across
species indicate common ancestry.
Answer: (A) Both A and R are true, and R is the correct
explanation of A.
Explanation: Molecular similarities, such as DNA and protein
sequence homology, provide strong evidence for shared evolutionary origins.
Assertion (A): Evolution leads to the formation of new species
over time.
Reason (R): As populations evolve and adapt to different
environments, they can become reproductively isolated and form new species.
Answer: (A) Both A and R are true, and R is the correct
explanation of A.
Explanation: Speciation often results from accumulated changes
in populations that lead to reproductive isolation and the emergence of new
species.
Assertion (A): Convergent evolution leads to the development of
similar traits in unrelated species.
Reason (R): When species from different evolutionary
backgrounds face similar environmental pressures, they evolve similar
adaptations.
Answer: (A) Both A and R are true, and R is the correct
explanation of A.
Explanation: Convergent evolution occurs when unrelated species
develop similar traits due to similar environmental pressures, such as the wings
of birds and bats.
Assertion (A): Evolution is a progressive process.
Reason (R): Evolution leads to the development of more complex
and advanced organisms over time.
Answer: (B) A is false, but R is true.
Explanation: Evolution is not necessarily progressive; it
involves changes that may be neutral, beneficial, or detrimental, depending on
the environment, rather than always leading to more complex organisms.
Assertion (A): Darwin’s theory of evolution focuses on survival
of the fittest.
Reason (R): According to Darwin, organisms with advantageous
traits are more likely to survive and reproduce.
Answer: (A) Both A and R are true, and R is the correct
explanation of A.
Explanation: Darwin’s theory emphasizes that natural selection
favors organisms that are best suited to their environment, increasing their
chances of survival and reproduction.
Assertion (A): The Theory of Lamarck proposed that acquired
traits are inherited.
Reason (R): Lamarck believed that traits acquired during an
organism’s lifetime could be passed on to offspring.
Answer: (A) Both A and R are true, and R is the correct
explanation of A.
Explanation: Lamarck’s theory of evolution involved the
inheritance of acquired characteristics, such as a giraffe’s neck becoming
longer by stretching to reach food, which was incorrectly believed to be passed
on to offspring.
Assertion (A): Fossils provide evidence for the theory of
evolution.
Reason (R): Fossils show the remains of organisms that lived in
different periods, revealing a sequence of life forms and changes over time.
Answer: (A) Both A and R are true, and R is the correct
explanation of A.
Explanation: Fossils provide a record of organisms from
different geological periods, showing how life has changed and evolved over
time.
Assertion (A): Evolution results in the adaptation of species
to their environment.
Reason (R): Natural selection favors traits that improve an
organism's ability to survive and reproduce in its environment.
Answer: (A) Both A and R are true, and R is the correct
explanation of A.
Explanation: Evolution by natural selection leads to
adaptations that enhance an organism's chances of survival and reproduction in a
given environment.
Assertion (A): Speciation is the process by which new species
arise.
Reason (R): Speciation occurs when populations of a species
become reproductively isolated and diverge genetically over time.
Answer: (A) Both A and R are true, and R is the correct
explanation of A.
Explanation: Speciation occurs when populations become
reproductively isolated, leading to genetic divergence and the formation of new
species.
Assertion (A): Evolution is supported by evidence from
embryology.
Reason (R): Similarities in the early stages of development in
different organisms suggest common ancestry.
Answer: (A) Both A and R are true, and R is the correct
explanation of A.
Explanation: Embryological similarities among different species
provide evidence of a shared evolutionary origin, as organisms with common
ancestors often show similar developmental stages.