Q.Comment upon homology.
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Homologous and Analogous Organs
Comparative anatomy provides evidence for evolution through two contrasting kinds of structures.
Homologous organs have the same fundamental structure and developmental origin but may perform different functions. They arise by divergent evolution from a common ancestor (adaptive radiation). Examples: the forelimbs of humans, whales, bats and cheetahs; and, in plants, the thorn of Bougainvillea and the tendril of Cucurbita — both modified axillary buds with a common origin but different functions.
Analogous organs have different structure and origin but perform the same function; they result from convergent evolution in unrelated lineages facing similar environments. Examples: the wings of insects and birds; the eyes of octopus and mammals; the flippers of penguins and dolphins. …
Homology is the fundamental similarity of structure (same basic plan/origin) in organs of different animals that may perform different functions — e.g. the forelimbs of man, whale, bat and cheetah. It indicates divergent evolution from a common ancestor. …
Homologous organs share a common structural plan and ancestry but may differ in function, evidencing divergent evolution.
Concept. Homology refers to the similarity in the basic structure and embryonic origin of organs in different organisms, even though the organs may perform different functions. Such organs are called homologous organs. Homology arises because the organisms inherited the organ from a common ancestor and then adapted it to different uses — this is divergent evolution (adaptive radiation).
Examples.
- The forelimbs of humans (grasping), whales (swimming), bats (flying) and cheetahs (running) all have the same bone arrangement — humerus, radius-ulna, carpals, metacarpals, phalanges — despite different functions.
- Thorns and tendrils of Bougainvillea and Cucurbita are homologous. …
Showing the 12 most recent of 26 on this concept.
- CBSE 2026Set 57/2/11 markMCQQ.What conclusion can be drawn if the forelimbs of an aquatic animal and a terrestrial animal have similar anatomical structure ? (A) Live in same habitat (B) Share common ancestors (C) Forelimbs perform same functions (D) Forelimbs are analogous
›Reveal solutionSolution
Similar anatomical structures in the forelimbs of different animals, despite varied functions and habitats, indicate that they share a common ancestor.
When we observe the natural world, one of the most fascinating aspects is the diversity of life, yet beneath this diversity, there are often striking similarities. The question of why different animals, living in vastly different environments and performing different tasks, might possess forelimbs with a fundamentally similar anatomical structure is central to understanding evolutionary biology. This observation provides powerful evidence for how life on Earth has changed over millions of years.
Consider the forelimb of a whale, an aquatic mammal, and the forelimb of a human, a terrestrial mammal. Superficially, they look very different: a whale's flipper is adapted for swimming, while a human's arm is adapted for grasping, manipulating, and walking (in our distant ancestors). However, if we examine their internal bone structure, we find a remarkable resemblance. Both possess a humerus (upper arm bone), radius and ulna (forearm bones), carpals (wrist bones), metacarpals (palm bones), and phalanges (finger bones), arranged in a very similar pattern.
ImportantStructures that have the same basic structural plan but perform different functions are called homologous structures. They are a key piece of evidence for evolution.
This similarity in basic anatomical structure, despite differences in function and habitat, is not a coincidence. It suggests that these animals inherited this fundamental limb design from a common ancestor. Over vast periods, as different groups of descendants adapted to various environments and lifestyles—some returning to water, others remaining on land—their forelimbs underwent modifications. These modifications allowed them to perform specialized functions like swimming, flying, running, or grasping, but the underlying blueprint remained. This process, where structures diverge from a common form to serve different functions, is known as divergent evolution.
Let's evaluate the given options based on this understanding:
- ** (A) Live in same habitat:** This is incorrect. The premise of the question explicitly states an aquatic animal and a terrestrial animal, meaning they live in different habitats.
- ** (C) Forelimbs perform same functions:** This is also incorrect. A whale's flipper is for swimming, while a human's arm is for grasping and manipulating. Their functions are distinct, even if both involve movement. …
- CBSE 2026Set A1 markMCQQ.Which of the following are examples of homologous organs in animals?(a) Eyes of octopus and human(b) Sweet potato and potato(c) Flippers of penguins and dolphins(d) Heart of reptiles and mammals
›Reveal solutionSolution
Homologous organs share a common ancestral structure though they may do different jobs; penguin and dolphin flippers fit this.
Homology reflects common ancestry: the forelimbs of vertebrates (penguin flipper, dolphin flipper, human arm, etc.) share the same underlying bone pattern (humerus, radius, ulna, carpals) inherited from a common ancestor — divergent evolution. Octopus and human eyes, and flippers of a marlin vs. a whale used only for the same function, are ana …
- CBSE 2026Set ZOOLOGY1 markMCQQ.The wings of butterflies and the wings of birds are the examples of which of the following?(a) Homologous organs(b) Analogous organs(c) Vestigial organs(d) Asymmetric organs
›Reveal solutionSolution
Butterfly wings and bird wings are analogous organs: same function, different evolutionary origin (convergent evolution).
Analogous organs are structures that perform the same function in different organisms but have a different basic structure and developmental origin, arising through convergent evolution in response to similar environmental/functional demands. The wings of a butterfly (a membranous extension of the exoskeleton, an insect structure) and the wings of a bird (a modified forelimb built on a vertebrate pentadactyl bone framework) both serve the function of flight, but they are structurally and developmentally comp …
- CBSE 2026Set ANNUAL1 markMCQQ.Wings of bat and wings of insects have similar functions, so they are examples of(a) Homologous organs(b) Analogous organs(c) Vestigeal organs(d) Connecting links
›Reveal solutionSolution
Organs that look/function alike but arose independently from different structures are analogous organs — evidence of convergent evolution.
Homologous organs share the same basic structure and developmental origin even though their functions may differ (e.g., the forelimbs of a human, cat, whale and bat all share the same bone plan). Analogous organs, in contrast, perform the same function but have different structural origin and evolve independently in unrelated groups facing similar environmental pressures — this is convergent evolution.
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- CBSE 2026Set ANNUAL1 markQ.Mention the type of evolution that has brought the similarity as seen in potato tuber and sweet potato.
›Reveal solutionSolution
Potato tuber (a modified underground STEM) and sweet potato (a modified ADVENTITIOUS ROOT) look and function alike (as storage organs) despite arising from different plant parts — this is convergent evolution, producing analogous structures.
When two organisms/structures resemble each other closely due to adaptation to a similar function or environment, even though their developmental/evolutionary origin is different, it is called convergent evolution and the resulting structures are termed analogous. The potato tuber develops from underground stem tissue (it bears nodes, internodes, and axillary buds/'eyes'), while the sweet potato is a modified adventitious root. Both evolved a swollen, starch-sto …
- CBSE 2026Set SEM31 markMCQQ.Match Column-I with Column-II and select the correct option : Column-I : i) Phylloclade of Opuntia, stem tendril of Passiflora ii) Archaeopteryx iii) Sphenodon, Limulus iv) Bat wings, insect wings v) Ornithorhynchus ; Column-II : a) Connecting link between reptiles and mammals b) Living fossils c) Analogous organs d) Missing link between reptiles and birds e) Homologous organs.(a) i-e, ii-c, iii-d, iv-b, v-a(b) i-b, ii-c, iii-a, iv-e, v-d(c) i-e, ii-b, iii-d, iv-c, v-a(d) i-b, ii-e, iii-a, iv-c, v-d
›Reveal solutionSolution
Correct evolutionary matches: stem modifications (Opuntia phylloclade, Passiflora tendril) = homologous organs; Archaeopteryx = missing link between reptiles and birds; Sphenodon & Limulus = living fossils; bat wing & insect wing = analogous organs; Ornithorhynchus (platypus) = connecting link between reptiles and mammals. Among the options, (c) is anchored on these definitive pairings.
The biology of each item:
- i) Phylloclade of Opuntia & stem tendril of Passiflora → (e) Homologous organs: both are modifications of the stem — same origin, different functions → homologous.
- ii) Archaeopteryx → (d) Missing link between reptiles and birds: it had reptilian teeth/tail and bird-like feathers.
- iii) Sphenodon, Limulus → (b) Living fossils: ancient forms surviving almost unchanged.
- iv) Bat wings & insect wings → (c) Analogous organs: different origins, same function (flight) → analogous.
- v) Ornithorhynchus (duck-billed platypus) → (a) Connecting link between reptiles and mammals: an egg-laying mammal. …
- CBSE 2025Set 57/5/11 markMCQQ.Which of the following combinations is a correct example of convergent evolution in Australian marsupials and Placental mammals ? [Australian Marsupials / Placental Mammals] (A) Lemur / Spotted cuscus (B) Tasmanian tiger cat / Anteater (C) Bobcat / Lemur (D) Numbat / Anteater
›Reveal solutionSolution
Convergent evolution produces similar adaptations in unrelated lineages facing similar ecological pressures. Numbat and Anteater both evolved specialized ant/termite-eating features independently, making (D) correct.
Convergent evolution occurs when distantly related organisms independently evolve similar traits because they occupy similar ecological niches or face similar environmental challenges. The classic textbook example compares Australian marsupials (which evolved in isolation on the Australian continent) with placental mammals from other continents that filled analogous roles.
The key is to identify pairs where the Australian marsupial and the placental mammal share a similar lifestyle and corresponding adaptations, despite their evolutionary distance.
Let me examine each option:
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Option (A): Lemur / Spotted cuscus
This pairing is backwards. Lemurs are placental mammals (primates from Madagascar), while spotted cuscuses are Australian marsupials. Both are arboreal and somewhat similar in lifestyle, but the question asks for [Australian Marsupial / Placental Mammal] in that order. The order is reversed here.
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Option (B): Tasmanian tiger cat / Anteater
The Tasmanian tiger cat (actually called the spotted-tailed quoll) is a carnivorous marsupial that hunts small vertebrates. Anteaters are highly specialized placental mammals with elongated snouts, long sticky tongues, and powerful claws for breaking into ant and termite nests. These occupy very different ecological niches—one is a generalist carnivore, the other an insectivore specialist. Not a good match.
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Option (C): Bobcat / Lemur
Bobcats are placental mammals (wild cats from North America), and lemurs are also placental mammals (primates). This pairing doesn't even include an Australian marsupial, so it cannot demonstrate marsupial-placental convergence.
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Option (D): Numbat / Anteater …
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- CBSE 2025Set F1 markMCQQ.Which of the following is an example of analogous organs?(a) Wings of birds and butterfly(b) Tail of dog and cat(c) Wing of bat and hand of man(d) All of these
›Reveal solutionSolution
Wings of a bird and a butterfly are analogous — same function, different origin (convergent evolution).
Analogous organs have a similar FUNCTION but a different structural origin (developmental/anatomical basis); they illustrate convergent evolution. The wing of a bird (a modified forelimb with feathers and bones) and the wing of a butterfly (a thin cuticular outgrowth of the exoskeleton) both serve flight yet arise from entirely different structures — hence analogous. In contrast, the wing of …
- CBSE 2025Set F1 markMCQQ.Convergent evolution is demonstrated by which of the following?(a) Bacteria and protozoa(b) Rat and dog(c) Starfish and cuttle fish(d) Dogfish and whale
›Reveal solutionSolution
Dogfish and whale show convergent evolution (analogous streamlined bodies).
Convergent evolution occurs when unrelated organisms independently evolve similar features because they live in similar environments; such similar structures are analogous. A dogfish is a cartilaginous fish while a whale is an aquatic mammal, yet both have evolved a streamlined, fusiform body with fin-like appendages fo …
- CBSE 2025Set A1 markQ.Fill in the blank with the correct answer: Placental wolf and Tasmania wolf similar to a corresponding ______.
›Reveal solutionSolution
Similar body forms arising independently in unrelated lineages, due to adaptation to similar habitats, is convergent evolution.
The placental wolf (Canis, found in North America) and the Tasmanian wolf/thylacine (a marsupial, found in Australia) belong to very different mammalian lineages — one placental, one marsupial — that have been separated for tens of millions of years. Yet both evolved a strikingly similar wolf-like body plan, skull shape, and predatory lifestyle because they occupied similar ecological niches in their respective, geographically isolated regions. This is a textbook example of convergent e …
- CBSE 2025Set ANNUAL1 markMCQQ.Which of the following are homologous organs?(a) Trunk of an elephant and forelimbs of a monkey(b) Wings of bird and wings of butterfly(c) Cat's paw and forelimbs of a horse(d) Wings of a bat and wings of a cockroach
›Reveal solutionSolution
Homologous organs share the same basic structural/developmental origin from a common ancestor but may perform different functions (divergent evolution); analogous organs perform the same function but arose independently from different origins (convergent evolution).
A cat's paw and a horse's forelimb are both built on the same pentadactyl limb skeletal plan (humerus-radius/ulna-carpals-digits) inherited from a common tetrapod ancestor, even though a cat's paw is used for walking/grasping and a horse's limb for running on a single toe (hoof) - this is the hallmark of homology.
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- CBSE 2025Set ANNUAL1 markQ.Would you consider the wings of a butterfly and a bat as homologous or analogous?
›Reveal solutionSolution
Homology depends on shared origin/structure, not shared function - so despite performing the same function (flight), butterfly wings and bat wings are analogous, not homologous, because their underlying structures and evolutionary origins are completely different.
Homologous organs have the same basic structural plan and arise from a common ancestral structure, even if they now serve different functions (e.g. divergent evolution, as in the pentadactyl forelimbs of different vertebrates). Analogous organs, by contrast, may look or function similarly but have entirely different developmental origins, having evolved independently to meet a similar environmental need (convergent evolution).
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