biology : class11 Genetic Relationships : Importance of Classification, Basis of Classification, Advantages of Classification : Need for Classification MCQ Questions and Answers
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Genetic Relationships
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MCQ Questions
1. Two organisms are placed in the same genus but in different families. Which inference about their genetic relationship is most appropriate?
A.
They share a more recent common ancestor with each other than organisms belonging to the same family
B.
They share a common ancestor, but their divergence is generally older than that of organisms within the same family
C.
They cannot possess any homologous structures because they belong to different families
D.
They must have evolved independently from unrelated ancestral groups
Correct Answer:
They share a common ancestor, but their divergence is generally older than that of organisms within the same family
Explanation:
Taxonomic ranks reflect degrees of genetic relatedness. Organisms in the same genus generally share a more recent common ancestor than organisms grouped only within the same family, although both groups retain common ancestry.
2. Which observation provides the strongest evidence that two species are genetically related, even when their adult body forms are markedly different?
A.
They occupy the same geographical region
B.
They have similar ecological roles
C.
They show extensive similarity in DNA sequences for several conserved genes
D.
They possess the same mode of nutrition
Correct Answer:
They show extensive similarity in DNA sequences for several conserved genes
Explanation:
Similarity in DNA sequences, particularly across multiple conserved genes, directly indicates shared genetic ancestry and is therefore stronger evidence of genetic relationship than similarities caused by habitat or function.
3. The presence of wings in birds and insects does not by itself establish close genetic relationship because the wings are primarily an example of which condition?
A.
Homology produced by inheritance from a recent common ancestor
B.
Analogy produced by convergent evolution
C.
Atavism produced by the reappearance of an ancestral trait
D.
Vestigiality produced by loss of ancestral function
Correct Answer:
Analogy produced by convergent evolution
Explanation:
Bird and insect wings perform similar functions but have different structural origins. Such analogous structures arise independently through convergent evolution and therefore do not reliably indicate close genetic relationship.
4. A classification system groups whales with mammals rather than with fishes mainly because whales possess several inherited features that reveal common ancestry with mammals. This illustrates classification based on
A.
Only the habitat occupied by the organisms
B.
Overall body size and external resemblance
C.
Evolutionary and genetic relationships
D.
Similarity in the method of locomotion alone
Correct Answer:
Evolutionary and genetic relationships
Explanation:
Whales share mammalian characters such as mammary glands and lungs despite living in water. Classification based on inherited characteristics reflects their evolutionary and genetic relationship rather than superficial habitat or locomotor similarities.
5. If species X and Y have a smaller genetic distance than species X and Z, the most defensible conclusion is that
A.
X and Y necessarily occupy the same habitat
B.
X and Y are likely to have diverged more recently from a common ancestor than X and Z
C.
Y and Z must belong to the same genus
D.
X and Y must be identical in all morphological features
Correct Answer:
X and Y are likely to have diverged more recently from a common ancestor than X and Z
Explanation:
A smaller genetic distance generally indicates fewer accumulated differences and a more recent divergence from a common ancestor. It does not necessarily imply identical morphology or the same habitat.
6. Which taxonomic arrangement most plausibly represents increasing genetic relatedness among the groups listed?
A.
Kingdom, phylum, class, order, family, genus, species
B.
Species, genus, family, order, class, phylum, kingdom
C.
Phylum, kingdom, species, class, genus, family, order
D.
Kingdom, class, phylum, family, order, species, genus
Explanation:
Genetic relatedness generally increases from broader taxonomic categories toward narrower ones. Species members are usually more closely related than members grouped only in the same genus, family, or higher category.
7. The forelimbs of humans, bats, and whales perform different functions but contain corresponding skeletal elements. Their similarity is most useful as evidence of
A.
Common ancestry and divergent evolution
B.
Independent origin through convergent evolution
C.
Identical adaptation to the same environment
D.
Absence of genetic change after species formation
Correct Answer:
Common ancestry and divergent evolution
Explanation:
Corresponding skeletal structures with different functions are homologous. Their presence indicates inheritance from a common ancestor followed by divergent modification in different evolutionary lineages.
8. A phylogenetic classification differs from an artificial classification because it primarily attempts to group organisms according to
A.
The number of visible similarities, regardless of ancestry
B.
Their evolutionary history and inferred genetic relationships
C.
Their economic usefulness to humans
D.
The environments in which they are currently found
Correct Answer:
Their evolutionary history and inferred genetic relationships
Explanation:
Phylogenetic classification reflects common ancestry and evolutionary divergence. Artificial classification may rely on selected superficial traits and therefore may place genetically unrelated organisms together.
9. When molecular evidence contradicts a classification based only on external morphology, the molecular evidence may be preferred because it
A.
Directly assesses inherited similarities less affected by environmental modification
B.
Proves that morphology has no role in taxonomy
C.
Shows that organisms with similar DNA always have identical body forms
D.
Eliminates the need to consider fossils and structural homology
Correct Answer:
Directly assesses inherited similarities less affected by environmental modification
Explanation:
DNA and protein comparisons can reveal inherited relationships that superficial morphology may obscure through convergent evolution or environmental adaptation. Molecular data therefore strengthen inferences about genetic relationships.
10. Two organisms share a recent common ancestor, but one lineage has accumulated numerous changes in body form because of a different environment. Which conclusion is most consistent with evolutionary classification?
A.
Their genetic relationship is disproved by their morphological difference
B.
They may still be classified closely if inherited and molecular evidence supports common ancestry
C.
They must belong to different kingdoms because environmental adaptation changes ancestry
D.
Their resemblance in genes is irrelevant to their taxonomic placement
Correct Answer:
They may still be classified closely if inherited and molecular evidence supports common ancestry
Explanation:
Descendant lineages can diverge greatly in appearance while retaining evidence of recent common ancestry. Evolutionary classification uses multiple inherited characters, including molecular evidence, rather than relying only on adult morphology.
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