Organic Evolution Questions and Answers

Q: A geographically variable species often divided into many subspecies is referred to as ......................

Such a species is a polytypic species.A polytypic species is one with geographically distinct populations that differ enough to be recognised as subspecies, as in many widespread birds and mammals.A monotypic species has no subspecies. Sister species are each other's closest relatives, sharing an immediate common ancestor. Sibling species are reproductively isolated species that look almost identical, the opposite of a single variable species.

Q: Why sexual selection can lead to extreme phenotypes ?

Sexual selection can produce extreme phenotypes because a positive feedback exists between the gene favouring the trait and the gene coding for it.This is Fisher's runaway process. If females prefer a trait such as a longer tail, males with longer tails leave more offspring, and the sons inherit the trait while the daughters inherit the preference. Genes for the trait and genes for the preference become correlated, each selection step strengthens the next, and the trait can be driven far beyond its survival optimum.Extreme ornaments usually carry higher costs, as the handicap principle stresses, so the first option is wrong. Learned preference for novelty does not build up a heritable extreme, and negative feedback from predation limits the trait rather than exaggerating it.

Q: Sarich and Wilson (1967) demonstrated that human, Gorilla and Chimpanzee were genetically equidistant and distinct for Orangutan and the divergence time is approximately :

Sarich and Wilson estimated the divergence at about 5 million years ago.Using immunological distances between serum albumins, calibrated against a molecular clock, Sarich and Wilson found humans, chimpanzees and gorillas almost equidistant from one another, with the orangutan more distant. They placed the human-ape split at around 5 million years, far more recent than the 15 to 30 million years then favoured from fossils such as Ramapithecus.Thirty and ten million years were the older palaeontological estimates their work challenged, and 100 million years is close to the age of the earliest placental mammals.

Q: Adaptive radiation produced numerous lineages from reptiles during chordates evolution, one of the following gave rise to mammals :

Mammals arose from the therapsids.Therapsids were the 'mammal-like reptiles' of the Permian and Triassic, a group of synapsids. Within them the cynodonts acquired mammalian features step by step (a secondary palate, differentiated teeth, a single lower jaw bone taking over the jaw joint), and one cynodont line gave rise to the first mammals in the Late Triassic.Plesiosaurs and ichthyosaurs were marine reptiles and pterosaurs were flying reptiles. All three were branches of the reptilian radiation that died out without leaving mammalian descendants.

Q: In the majority of plants photosynthesis is carried out in leaves but in cachi inhabiting desert, photosynthesis is carried out by stem. This type of evolutionary change in the position is referred to as ...........................

A change in the position of a developmental feature is heterotopy.Heterotopy is an evolutionary change in where a structure or process develops in the body. In cacti (printed 'cachi') the leaves are reduced to spines and photosynthesis shifts to the green, fleshy stem, a change in location.Heterochrony is a change in the timing or rate of developmental events. Heteroplasmy is the presence of more than one type of mitochondrial DNA in a cell. Heterotropy is not the standard term for a change in position.

Q: Which of the following islands visited by Darwin inspired him to propose theory of evolution ?

Darwin was inspired by the Galapagos islands.Darwin visited the Galapagos in 1835 during the voyage of HMS Beagle. The differences between the finches, mockingbirds and giant tortoises of different islands suggested to him that species are not fixed but change and diverge, ideas he later developed into the theory of evolution by natural selection.Guatemala is a country on the Central American mainland, not an island group. The Faroe and Solomon islands (printed Soloman) were not on the Beagle's route and played no part in his theory.

Q: Insects, ammonoids and amphibians have originated in which of the following periods of Paleozoic era ?

Insects, ammonoids and amphibians originated in the Devonian period.The Devonian (about 419 to 359 million years ago) has the earliest known insect fossils, the first ammonoids, which evolved from straight-shelled nautiloids early in the period, and the first four-limbed vertebrates, the earliest amphibians such as Ichthyostega and Acanthostega, near its end.The Cambrian saw the radiation of most animal phyla, the Ordovician the spread of marine invertebrates and early vertebrates, and the Silurian the first jawed fishes and early land plants, all before these three groups appeared.

31.

A geographically variable species often divided into many subspecies is referred to as ......................

A.Monotypic species
B.Sister species
C.Sibling species
D.Polytypic species

Exam Year(s)

MH SET - 2024, SET Exam - 2024,

Answer: D

Such a species is a polytypic species.

A polytypic species is one with geographically distinct populations that differ enough to be recognised as subspecies, as in many widespread birds and mammals.

A monotypic species has no subspecies. Sister species are each other's closest relatives, sharing an immediate common ancestor. Sibling species are reproductively isolated species that look almost identical, the opposite of a single variable species.

Discuss in Forum

32.

Why sexual selection can lead to extreme phenotypes ?

A.Because the extreme phenotype incurs lower costs than the mean train in the population
B.Because the partner quickly learns and favours new images
C.Because a positive feedback exists between the gene favouring the trait and the gene coding for it
D.Because a negative feedback exists between the trait and the risk of predation

Exam Year(s)

MH SET - 2024, SET Exam - 2024,

Answer: C

Sexual selection can produce extreme phenotypes because a positive feedback exists between the gene favouring the trait and the gene coding for it.

This is Fisher's runaway process. If females prefer a trait such as a longer tail, males with longer tails leave more offspring, and the sons inherit the trait while the daughters inherit the preference. Genes for the trait and genes for the preference become correlated, each selection step strengthens the next, and the trait can be driven far beyond its survival optimum.

Extreme ornaments usually carry higher costs, as the handicap principle stresses, so the first option is wrong. Learned preference for novelty does not build up a heritable extreme, and negative feedback from predation limits the trait rather than exaggerating it.

Discuss in Forum

33.

Sarich and Wilson (1967) demonstrated that human, Gorilla and Chimpanzee were genetically equidistant and distinct for Orangutan and the divergence time is approximately :

A.30 mya
B.05 mya
C.10 mya
D.100 mya

Exam Year(s)

MH SET - 2024, SET Exam - 2024,

Answer: B

Sarich and Wilson estimated the divergence at about 5 million years ago.

Using immunological distances between serum albumins, calibrated against a molecular clock, Sarich and Wilson found humans, chimpanzees and gorillas almost equidistant from one another, with the orangutan more distant. They placed the human-ape split at around 5 million years, far more recent than the 15 to 30 million years then favoured from fossils such as Ramapithecus.

Thirty and ten million years were the older palaeontological estimates their work challenged, and 100 million years is close to the age of the earliest placental mammals.

Discuss in Forum

34.

Adaptive radiation produced numerous lineages from reptiles during chordates evolution, one of the following gave rise to mammals :

A.Plesiosaurus
B.Ichthyosaurus
C.Pterosaurus
D.Therapsids

Exam Year(s)

MH SET - 2025, SET Exam - 2025,

Answer: D

Mammals arose from the therapsids.

Therapsids were the 'mammal-like reptiles' of the Permian and Triassic, a group of synapsids. Within them the cynodonts acquired mammalian features step by step (a secondary palate, differentiated teeth, a single lower jaw bone taking over the jaw joint), and one cynodont line gave rise to the first mammals in the Late Triassic.

Plesiosaurs and ichthyosaurs were marine reptiles and pterosaurs were flying reptiles. All three were branches of the reptilian radiation that died out without leaving mammalian descendants.

Discuss in Forum

35.

In the majority of plants photosynthesis is carried out in leaves but in cachi inhabiting desert, photosynthesis is carried out by stem. This type of evolutionary change in the position is referred to as ...........................

A.Heterochrony
B.Heterotropy
C.Heterotopy
D.Heteroplasmy

Exam Year(s)

MH SET - 2025, SET Exam - 2025,

Answer: C

A change in the position of a developmental feature is heterotopy.

Heterotopy is an evolutionary change in where a structure or process develops in the body. In cacti (printed 'cachi') the leaves are reduced to spines and photosynthesis shifts to the green, fleshy stem, a change in location.

Heterochrony is a change in the timing or rate of developmental events. Heteroplasmy is the presence of more than one type of mitochondrial DNA in a cell. Heterotropy is not the standard term for a change in position.

Discuss in Forum

36.

Which of the following islands visited by Darwin inspired him to propose theory of evolution ?

A.Guatemala
B.Galapagos islands
C.Faroe islands
D.Soloman islands

Exam Year(s)

MH SET - 2025, SET Exam - 2025,

Answer: B

Darwin was inspired by the Galapagos islands.

Darwin visited the Galapagos in 1835 during the voyage of HMS Beagle. The differences between the finches, mockingbirds and giant tortoises of different islands suggested to him that species are not fixed but change and diverge, ideas he later developed into the theory of evolution by natural selection.

Guatemala is a country on the Central American mainland, not an island group. The Faroe and Solomon islands (printed Soloman) were not on the Beagle's route and played no part in his theory.

Discuss in Forum

37.

Insects, ammonoids and amphibians have originated in which of the following periods of Paleozoic era ?

A.Cambrian period
B.Ordovician period
C.Silurian period
D.Devonian period

Exam Year(s)

MH SET - 2025, SET Exam - 2025,

Answer: D

Insects, ammonoids and amphibians originated in the Devonian period.

The Devonian (about 419 to 359 million years ago) has the earliest known insect fossils, the first ammonoids, which evolved from straight-shelled nautiloids early in the period, and the first four-limbed vertebrates, the earliest amphibians such as Ichthyostega and Acanthostega, near its end.

The Cambrian saw the radiation of most animal phyla, the Ordovician the spread of marine invertebrates and early vertebrates, and the Silurian the first jawed fishes and early land plants, all before these three groups appeared.

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