Q.A dicotyledonous plant bears flowers but never produces fruits and seeds. The most probable cause for the above situation is:
🔒You're viewing a preview — the full solution, concept, methods & PYQ mapping are locked.
🔒 Start your 14-day free trial to unlock the full solution →Concept understanding — Male And Female Gametophyte
Let’s start with something you already know. Think of a plant like a mango tree. It produces flowers, and those flowers eventually turn into mangoes. How does that happen? The flower is the plant’s reproductive organ, and inside it, two tiny but crucial structures are made: the male gametophyte and the female gametophyte. These are not the “male” and “female” parts of the flower themselves (like the stamen and pistil) — they are the microscopic, single-generation cells that actually carry the genetic material to form the next plant.
The everyday intuition
Imagine you are baking a cake. The male gametophyte is like the packet of dry yeast — it’s small, mobile, and needs to be added to the mixture. The female gametophyte is like the bowl of flour, eggs, and sugar — it’s larger, stationary, and provides the environment where the yeast works. Without the yeast reaching the bowl, no cake rises. Without the bowl, the yeast has nothing to act on. In a flower, the male gametophyte (pollen grain) must travel to the female gametophyte (embryo sac) for fertilisation to happen.
The precise meaning
In NCERT biology, the male gametophyte is the pollen grain. It develops inside the anther (the top part of the stamen). A mature pollen grain contains two cells: a tube cell and a generative cell. The tube cell will grow a long tube down the style of the pistil, and the generative cell will divide to form two sperm cells. So the male gametophyte is not the whole stamen — it’s the tiny, single-celled (or two-celled) structure that carries the male genetic material.
The female gametophyte is the embryo sac. It develops inside the ovule, which is located in the ovary of the pistil. The embryo sac is a seven-celled, eight-nucleate structure (though you don’t need to memorise numbers for a prose subject — just know it’s a small, organised sac). It contains the egg cell (the female gamete) and other cells that help in fertilisation and nourishment. The female gametophyte is not the whole pistil — it’s the microscopic sac inside the ovule.
The male gametophyte (pollen grain) is haploid — it has only one set of chromosomes. The female gametophyte (embryo sac) is also haploid. When they fuse during fertilisation, they form a diploid zygote, which grows into the seed. This is why both are called “gametophytes” — they produce gametes (sperm and egg).
Why it matters …
The question is about a dicot plant that flowers but never sets fruit or seed. That means pollination and fertilisation are not happening, or the female reproductive structures are absent.
If the plant is dioecious, male and female flowers are on separate plants. A plant that bears only staminate (male) flowers will never produce fruits or seeds because it has no pistil to receive pollen and no ovules to fertilise. A plant with only pistillate flowers could still produce fruit if pollen reaches it from another plant, so that is not the most probable cause of never producing fruit. Monoecious plants have both flower types on the same plant, so they can self-pollinate or cross-pollinate and usually do set seed.
- Dioecious means male and female flowers on separate plants. …
A dicotyledonous plant that flowers but never sets fruits or seeds is most likely dioecious and bears only staminate (male) flowers — so it can never produce the female gametophyte needed for seed formation.
To understand why this happens, we need to step back and look at how flowering plants reproduce. In angiosperms, the flower is the reproductive structure. The male part (stamen) produces pollen grains, each containing a male gametophyte. The female part (pistil) contains the ovule, where the female gametophyte (embryo sac) develops. For a fruit and seed to form, pollination must occur — pollen must reach the stigma, germinate, and fertilise the egg cell inside the ovule.
Now, not all plants have both male and female organs in the same flower or on the same plant. This is where the terms monoecious and dioecious become important.
A monoecious plant has separate male and female flowers on the same individual. Think of maize or cucumber — one plant can produce both pollen and ovules, so it can potentially self-pollinate or cross-pollinate and still set fruit. So if our dicot were monoecious, it could produce fruits and seeds, provided pollination occurs. That rules out option (C).
A dioecious plant, on the other hand, has male and female flowers on separate individuals. Some plants are strictly male (staminate flowers only), some strictly female (pistillate flowers only). This is like papaya or date palm — you need a male plant and a female plant growing nearby for fruit to form.
Now look at the options:
-
Option (A): Plant is dioecious and bears only pistillate flowers. That means it has only female flowers. Such a plant can produce ovules (female gametophytes) but no pollen. If there is no male plant nearby to supply pollen, fertilisation cannot happen, and no fruits or seeds will form. So this could be a cause — but the question says "never produces fruits and seeds." A pistillate plant can produce fruits if it receives pollen from a male plant. So the absence of fruit here depends on the absence of a pollen source, not on the plant itself.
-
Option (B): Plant is dioecious and bears both pistillate and staminate flowers. This is contradictory — a dioecious plant by definition does not have both flower types on the same individual. So this option is biologically impossible. Discard it. …
Showing the 12 most recent of 28 on this concept.
- TG EAPCET 2026Set ap-2026-05-04-FN1 markMCQQ.Match the followingThe correct answer is (A) I – C – Q, II – D – P, III – B – R, IV – A – S (B) I – D – P, II – C – Q, III – B – R, IV – A – S (C) I – D – P, II – C – Q, III – A – S, IV – B – R (D) I – D – P, II – A – S, III – C – Q, IV – B – R
Plant name Ovary position Placentation I Mustard A Superior P Parietal II Ray florets of sunflower B Half inferior (or) Half superior Q Basal III Pea C Inferior R Marginal IV China rose D Superior S Axial ›Reveal solutionSolution
This question tests your knowledge of floral morphology — specifically ovary position and placentation type in four common plants. The correct match is I – D – P, II – C – Q, III – B – R, IV – A – S, which corresponds to option (B).
The key to solving this is recalling the flower structure and fruit/seed arrangement for each plant. Ovary position tells you whether the flower is hypogynous (superior ovary), perigynous (half-inferior), or epigynous (inferior). Placentation describes how ovules are arranged inside the ovary. Let’s go plant by plant.
-
Mustard (I) — Mustard belongs to the family Brassicaceae. Its flowers are hypogynous, meaning the ovary is superior (D). The placentation is parietal (P) — ovules are attached to the ovary wall along the fused margins of the carpels. So I → D, P.
-
Ray florets of sunflower (II) — Sunflower is a member of Asteraceae. The ray florets are the outer, strap-shaped flowers. In Asteraceae, the ovary is inferior (C) — the floral parts arise above the ovary. Placentation is basal (Q) — a single ovule sits at the base of the ovary. So II → C, Q.
-
Pea (III) — Pea (Fabaceae) has a perigynous flower — the ovary is half-inferior / half-superior (B). Its placentation is marginal (R) — ovules are arranged along the fused ventral suture of the single carpel. So III → B, R. …
-
- TG EAPCET 2026Set ap-2026-05-04-FN1 markMCQQ.Consider the following statements Statement I: Evolution of species in a single lineage is called anagenesis Statement II: If speciation takes place due to geographical isolation, it is called allopatric speciation (A) Both statement I and statement II are true (B) Both statement I and statement II are false (C) Statement I is true, but statement II is false (D) Statement I is false, but statement II is true
›Reveal solutionSolution
Both statements accurately describe modes of evolution and speciation. Anagenesis is indeed evolution within a single lineage, and allopatric speciation occurs due to geographical isolation. The correct option is (A).
Concept and Intuition
Speciation is the evolutionary process by which new biological species arise. It is a fundamental process in evolution, leading to the diversity of life on Earth. There are different ways to classify speciation, often based on whether a lineage splits or not, and whether geographical barriers are involved.
When we talk about the pattern of evolution, we distinguish between:
- Anagenesis: This describes evolutionary change within a single lineage. Imagine a species gradually changing over a long period, eventually becoming so different from its ancestors that it's considered a new species, but without any branching. It's a linear transformation.
- Cladogenesis: This describes evolutionary change that involves the splitting of a single lineage into two or more distinct lineages. This is the more common way new species arise, leading to an increase in the number of species.
When we talk about the mechanism of speciation, particularly concerning geographical factors, we distinguish between:
- Allopatric Speciation: This occurs when populations of a species are separated by a geographical barrier (like a mountain range, a river, or an ocean). This isolation prevents gene flow between the populations, allowing them to diverge genetically due to different selective pressures, mutations, and genetic drift. Over time, they become reproductively isolated, forming new species.
- Sympatric Speciation: This occurs when new species arise within the same geographical area as the parent species, without any physical barrier. This can happen due to factors like polyploidy (common in plants), habitat differentiation, or sexual selection.
Step-by-step Evaluation
- Analyze Statement I: Evolution of species in a single lineage is called anagenesis. …
- TG EAPCET 2025Set ap-2025-04-30-FN1 markMCQQ.Floral formula of mustard flower (A) Br \quad Brl \quad \oplus \quad \text{\female} \quad K_4 \quad C_4 \quad A_{2+4} \quad \underline{G}2 (B) Br \quad ebrl \quad % \quad K_4 \quad C{2+2} \quad A_{2+4} \quad \underline{G}{(2)} (C) Ebr \quad Ebrl \quad \oplus \quad \text{\female} \quad K{2+2} \quad C_4 \quad A_{2+4} \quad \underline{G}{(2)} (D) Ebr \quad Ebrl \quad \oplus \quad \text{\female} \quad K{2+2} \quad C_4 \quad A_{4+2} \quad \underline{G}_2
›Reveal solutionSolution
The floral formula of mustard (family Brassicaceae) is Ebr Ebrl ⊕ ♀ K₂₊₂ C₄ A₂₊₄ G(₂), which corresponds to option (C).
The question tests your ability to recall the standard floral formula for mustard (Brassica), a member of the Brassicaceae (Cruciferae) family. A floral formula is a shorthand that encodes symmetry, sex, and the number and arrangement of floral parts. For mustard, the key features are: actinomorphic (radially symmetric) flowers, bisexual, with a calyx of 4 sepals in two whorls of 2, a corolla of 4 petals in a cross-like arrangement, 6 stamens (2 short + 4 long), and a superior ovary of 2 fused carpels.
Let’s decode each symbol in the options step by step.
-
Bracteate or ebracteate? Mustard flowers are ebracteate (no bract) and ebracteolate (no bracteoles). The symbol
Ebrmeans ebracteate, andEbrlmeans ebracteolate. Options (A) and (B) useBr(bracteate) orebrl(incorrect), so they are wrong. Only (C) and (D) start withEbr Ebrl. -
Floral symmetry. Mustard flowers are actinomorphic (radially symmetric), denoted by
⊕. Option (B) uses%(zygomorphic), so it is incorrect. (A), (C), and (D) all have⊕. -
Sex. Mustard flowers are bisexual (hermaphrodite), shown by
♀. All options except (B) have this symbol. -
Calyx (K). The calyx has 4 sepals arranged in two whorls of 2 each (i.e.,
K₂₊₂). Options (A) and (B) showK₄(4 sepals in one whorl), which is not accurate for Brassicaceae. Only (C) and (D) haveK₂₊₂. -
Corolla (C). The corolla has 4 petals in a cruciform (cross-like) arrangement, written as
C₄. Both (C) and (D) have this. Option (A) also hasC₄, but (B) hasC₂₊₂(incorrect). …
-
- TG EAPCET 2025Set ap-2025-04-30-FN1 markMCQQ.Capsule is found in (A) Capsicum (B) Lycopersicon (C) Solanum (D) Nicotiana
›Reveal solutionSolution
The fruit type "capsule" is a dry, dehiscent fruit that splits open at maturity. Among the given options, it is found in Nicotiana (tobacco), making the correct answer (D).
The question asks you to match a fruit type — a capsule — with the plant genus that produces it. This is a classic botany identification problem from the Solanaceae family (the nightshade family). The key is to know the fruit types of common genera within this family: Capsicum (chili pepper), Lycopersicon (tomato), Solanum (potato, brinjal), and Nicotiana (tobacco).
A capsule is a dry fruit that, when ripe, splits open (dehisces) along defined lines or pores to release seeds. This contrasts with a berry, which is a fleshy fruit that does not split open. In the Solanaceae family, most genera produce berries, but Nicotiana is a notable exception — it produces a capsule.
Let’s go through each option step by step.
-
Option (A): Capsicum
Capsicum (chili, bell pepper) produces a berry — a fleshy fruit with many seeds embedded in a juicy interior. The fruit does not split open at maturity; it remains intact. So, not a capsule.
-
Option (B): Lycopersicon
Lycopersicon (tomato) also produces a berry. The tomato fruit is fleshy, with seeds in a gelatinous pulp, and it does not dehisce. Hence, not a capsule.
-
Option (C): Solanum
Solanum (potato, brinjal/eggplant) again yields a berry. For example, the brinjal fruit is a large, fleshy berry. Even the potato plant produces small, tomato-like berries (though the edible part is a tuber, not the fruit). So, not a capsule.
-
Option (D): Nicotiana …
-
- TG EAPCET 2025Set ap-2025-04-30-FN1 markMCQQ.If speciation takes place due to geographical isolation, it is called (A) Allopatric speciation (B) Sympatric speciation (C) Anagenesis (D) Cladogenesis
›Reveal solutionSolution
When speciation is driven by geographical isolation — a physical barrier splitting a population — the correct term is allopatric speciation.
The core idea here is simple: speciation is the process by which one species splits into two or more distinct species. The key factor that determines the type of speciation is how the populations become reproductively isolated from each other. Geographical isolation is the most straightforward and historically recognized mechanism.
Let’s break down the options to see why only one fits.
-
Allopatric speciation — The prefix allo- means “other” or “different,” and -patric means “place” or “homeland.” So allopatric speciation literally means “speciation in a different place.” This happens when a physical barrier (a mountain range, a river, an ocean, a desert) arises and splits a single population into two or more groups. Separated by geography, these groups can no longer interbreed. Over many generations, different mutations, natural selection, and genetic drift act on each isolated group, eventually making them so different that even if the barrier disappears, they can no longer produce fertile offspring. This is exactly what the question describes.
-
Sympatric speciation — Sym- means “same.” This is speciation that occurs without geographical isolation. The populations live in the same area but become reproductively isolated due to other factors, such as polyploidy (common in plants), habitat differentiation, or sexual selection. This is not the answer because the question explicitly mentions geographical isolation.
-
Anagenesis — This is not a type of speciation at all. Anagenesis (also called phyletic evolution) refers to the gradual, linear change of a single species over time, without any branching. One species slowly transforms into another. There is no splitting into multiple species, so it doesn’t fit the definition of speciation in the sense of creating new, distinct lineages. …
-
- TG EAPCET 2024Set ap-2024-05-08-FN1 markMCQQ.Assertion (A): Endosperm is haploid in Gymnosperms Reason (R): Female gametophytic tissue acts as endosperm in Gymnosperms The correct answer is (A) (A) and (R) are correct. (R) is the correct explanation of (A) (B) (A) and (R) are correct, but (R) is not the correct explanation of (A) (C) (A) is correct but (R) is not correct (D) (A) is not correct but (R) is correct
›Reveal solutionSolution
The gymnosperm "endosperm" is nothing but the haploid female gametophyte, formed before fertilisation. So the Assertion is true, the Reason is true, and the Reason is the correct explanation — option (A).
The concept first: where does the food-storing tissue of a seed come from?
A seed must feed the young embryo, but different plant groups solve this in different ways, and the ploidy of the nutritive tissue tells you which route was taken.
- Gymnosperms. Inside the ovule, the functional megaspore divides mitotically to build a multicellular female gametophyte (the "prothallus"). Since it is produced from a megaspore by mitosis, every cell is haploid (n). Archegonia form at its micropylar end, each with an egg. This gametophytic tissue accumulates food reserves before fertilisation ever happens, and after fertilisation it simply surrounds and nourishes the embryo. Botanists still call it "endosperm" out of convention, but it is really female-gametophytic tissue — hence haploid.
- Angiosperms. Here the nutritive tissue is made only after fertilisation, by triple fusion: one male gamete fuses with the two polar nuclei of the central cell, giving a triploid (3n) primary endosperm nucleus. This is the second fusion event of double fertilisation.
A neat memory hook: gymnosperm endosperm is pre-fertilisation and haploid; angiosperm endosperm is post-fertilisation and triploid.
Step-by-step evaluation …
- TG EAPCET 2024Set ap-2024-05-08-FN1 markMCQQ.‘Pepo’ fruit develops from the following type of ovary (A) Tricarpellary, Syncarpous, Unilocular, Parietal placentation (B) Tricarpellary, Syncarpous, Trilocular, Parietal placentation (C) Tricarpellary, Syncarpous, Unilocular, Axile placentation (D) Tricarpellary, Syncarpous, Trilocular, Axile placentation
›Reveal solutionSolution
Pepo fruits, like cucumber and pumpkin, develop from an ovary that is tricarpellary, syncarpous, unilocular, and exhibits parietal placentation. The correct option is (A).
Concept and Intuition
A Pepo is a specialized type of berry characteristic of the Cucurbitaceae family (gourds, pumpkins, cucumbers, melons). Understanding the structure of the ovary from which such a fruit develops requires knowledge of its key features: the number of carpels, whether they are fused, the number of chambers (locules), and how the ovules are arranged within the ovary (placentation).
In plants of the Cucurbitaceae family, the flower typically has an inferior ovary. This ovary is formed from multiple carpels that are fused together. The arrangement of ovules on the inner wall of this ovary, along with the number of chambers, defines the specific type of placentation and locule structure.
Step-by-step Derivation
-
Carpel Number: Pepo fruits, being characteristic of the Cucurbitaceae family, typically develop from an ovary formed by three carpels. Therefore, the ovary is tricarpellary.
-
Fusion of Carpels: In the Cucurbitaceae family, the carpels are always fused together to form a single pistil. This condition is known as syncarpous.
-
Locule Number and Placentation Type: This is the most distinctive feature for Pepo.
- The ovary is fundamentally unilocular (single-chambered).
- The ovules develop on the inner wall of the ovary. This arrangement is termed parietal placentation.
- A characteristic feature in Pepo development is that the placentae (the regions bearing ovules) often grow inwards from the ovary wall and may even meet in the center, giving a superficial appearance of multiple chambers. However, true septa (partitions) are absent or incomplete, maintaining the unilocular nature of the ovary.
Watch outDo not confuse the inward growth of parietal placentae with true septa that divide an ovary into multiple locules. In parietal placentation, even with inward projections, the ovary is considered unilocular if complete septa are absent.
-
Evaluating the Options: …
-
- TG EAPCET 2024Set ap-2024-05-08-FN1 markMCQQ.Intine of pollengrain is made up of (A) Sporopollenin (B) Cellulose and Lignin (C) Chitin and Lignin (D) Cellulose and Pectin
›Reveal solutionSolution
The intine of a pollen grain is the inner wall layer, composed of cellulose and pectin — making option (D) the correct answer.
The pollen grain wall is a two-layered structure, and each layer has a distinct composition that reflects its function. The outer layer, the exine, is tough and resistant — it’s made of sporopollenin, one of the most durable organic substances known. The inner layer, the intine, lies just beneath the exine and is in direct contact with the living cell inside. Its job is to be flexible and allow the pollen tube to emerge during germination. That’s why the intine is made of softer, more pliable materials: cellulose and pectin, which are common components of plant cell walls.
Let’s walk through the options to see why only one fits.
-
Option (A): Sporopollenin — This is the material of the exine, not the intine. Sporopollenin is highly resistant to decay, acids, and high temperatures, which protects the pollen grain during dispersal. But it’s too rigid and impermeable for the intine’s role.
-
Option (B): Cellulose and Lignin — Lignin adds strength and rigidity, typical of woody tissues. The intine needs to be soft and expandable, not rigid, so lignin is absent here. …
-
- TG EAPCET 2024Set ap-2024-05-08-FN1 markMCQQ.The following type of cell divisions occurs in microspore mother cells to increase their number in microsporangium (A) Meiosis (B) Mitosis (C) Amitosis (D) Endomitosis
›Reveal solutionSolution
Microspore mother cells (MMCs) are diploid cells that undergo meiosis to produce haploid microspores, not mitosis to increase their own number. However, the question asks about division to increase the number of MMCs themselves in the microsporangium, which occurs through mitosis before meiosis begins.
Understanding Cell Division in Microsporangium Development
The key to this question is distinguishing between two phases in pollen development:
- Proliferation phase: Building up the population of microspore mother cells
- Meiotic phase: Converting those mother cells into microspores
The Developmental Sequence
Let's trace what happens in the microsporangium (pollen sac):
-
Initial sporogenous tissue formation: The microsporangium begins with diploid sporogenous cells in the anther. These cells need to multiply to create a sufficient population of microspore mother cells (also called pollen mother cells or PMCs).
-
Mitotic divisions increase MMC number: The sporogenous cells undergo mitosis repeatedly. This is crucial because:
- Mitosis preserves the diploid chromosome number (2n → 2n)
- It produces genetically identical daughter cells
- It builds up a large population of microspore mother cells
-
MMCs prepare for meiosis: Once enough microspore mother cells have accumulated, each one becomes enclosed in a callose wall and prepares for meiosis.
-
Meiosis produces microspores: Each diploid MMC then undergoes meiosis (not to increase its number, but to produce four haploid microspores). …
- TG EAPCET 2024Set ap-2024-05-07-FN1 markMCQQ.Statement I : Absence of gene exchange between populations is called reproductive isolation Statement II : Natural selection is the driving force of evolution (A) Both statements I and II are true (B) Both statements I and II are false (C) Statement I is true. But II is false (D) Statement I is false. But II is true.
›Reveal solutionSolution
Reproductive isolation is indeed the absence of gene exchange between populations, and natural selection is a key driving force of evolution, so both statements are true. The correct option is (A).
Concept & Intuition
This question tests two foundational ideas in evolutionary biology. First, reproductive isolation is the biological barrier that prevents populations from interbreeding and exchanging genes—it’s what keeps species separate. Second, natural selection is one of the primary mechanisms (along with mutation, gene flow, and genetic drift) that drives evolutionary change by favoring traits that improve survival and reproduction. Both statements are standard textbook facts.
Step-by-step reasoning
-
Evaluate Statement I
- Reproductive isolation means that two populations cannot produce fertile, viable offspring or do not mate at all. This stops gene flow between them.
- Definition: “Absence of gene exchange between populations” is exactly how reproductive isolation is described in biology.
- Therefore, Statement I is true.
-
Evaluate Statement II
- Natural selection acts on heritable variation, causing differential reproductive success. Over generations, this changes allele frequencies in a population.
- It is widely accepted as a major driving force of adaptive evolution (though not the only one—genetic drift, for example, also plays a role).
- The phrase “driving force” is accurate in the sense that natural selection is the primary process that leads to adaptation. …
-
- TG EAPCET 2023Set ap-2023-05-10-FN1 markMCQQ.Example for asymmetric flower (A) Gulmohar (B) Cassia (C) Canna (D) Pea
›Reveal solutionSolution
The key idea is that asymmetric flowers have only one plane of symmetry (zygomorphic) or none, and among the options, Canna is the classic example of an asymmetric flower because its floral parts are arranged in a spiral without any symmetry plane. The correct option is (C).
Concept & Intuition
Flowers are classified by symmetry:
- Actinomorphic (radial symmetry): multiple planes of symmetry (e.g., Gulmohar, Cassia, Pea).
- Zygomorphic (bilateral symmetry): one plane of symmetry (e.g., Pea).
- Asymmetric: no plane of symmetry at all.
The question asks for the asymmetric flower. Most common flowers are either actinomorphic or zygomorphic. True asymmetry is rare; Canna is a well-known example because its perianth parts are spirally arranged and unequal, lacking any mirror plane.
Step-by-step reasoning
-
Identify symmetry of each option
- (A) Gulmohar (Delonix regia): Flowers are showy, with 5 petals arranged radially → actinomorphic (multiple symmetry planes).
- (B) Cassia (genus Cassia): Flowers have 5 nearly equal petals, radial symmetry → actinomorphic.
- (C) Canna (genus Canna): Flowers have 3 sepals and 3 petals that are often unequal, spirally arranged, and the androecium is modified into petal-like staminodes; no plane of symmetry exists → asymmetric.
- (D) Pea (Pisum sativum): Flowers have a distinct banner, wings, and keel → zygomorphic (one symmetry plane).
-
Confirm the definition of asymmetry …
- TG EAPCET 2023Set ap-2023-05-10-AN1 markMCQQ.If speciation takes place due to geographical isolation, it is called (A) Anagenesis (B) Directional evolution (C) Phyletic evolution (D) Allopatric speciation
›Reveal solutionSolution
Speciation caused by geographical isolation is known as allopatric speciation, where populations become reproductively isolated due to physical barriers. The correct option is (D).
Speciation is the evolutionary process by which new biological species arise. It's a fundamental concept in biology, explaining the diversity of life on Earth. One of the most common and well-understood ways for new species to form involves populations becoming separated by physical barriers. This separation prevents gene flow between them, allowing them to evolve independently and eventually become distinct species.
Let's break down how this process works and identify the correct term.
-
Understanding Speciation:
Speciation occurs when populations of a species evolve to become reproductively isolated from each other. This means they can no longer interbreed and produce fertile offspring, even if they were to come into contact again. This reproductive isolation is the defining characteristic of separate species.
-
The Role of Geographical Isolation:
Geographical isolation refers to the physical separation of populations by barriers such as mountains, rivers, oceans, or even large distances. When a population is split by such a barrier, the two resulting groups can no longer interact or exchange genetic material.
-
Independent Evolution and Reproductive Isolation:
Once geographically isolated, the two populations are exposed to different environmental pressures, experience different mutations, and undergo different patterns of natural selection and genetic drift. Over long periods, these differences accumulate, leading to genetic divergence. Eventually, the genetic differences become so significant that even if the geographical barrier is removed, the two populations can no longer interbreed successfully. They have become two distinct species.
-
Defining Allopatric Speciation:
The term for speciation that occurs due to geographical isolation is allopatric speciation. The word "allopatric" comes from Greek: "allos" meaning "other" and "patra" meaning "homeland." So, it literally means "other homeland," referring to populations living in different geographical areas.
ImportantAllopatric speciation is the most common mode of speciation, driven by the interruption of gene flow between populations due to physical barriers.
-
Why Other Options Are Incorrect: …
-
🎓Unlock everything free for 14 days
- ✓Full step-by-step solutions
- ✓Concept-first explanations
- ✓Methods, shortcuts & mistakes
- ✓PYQ mapping + timed mock tests
Full access for 14 days. No credit card required.