Every Banana of a Variety Is Genetically the Same Plant
Learn the modes of asexual reproduction with their examples, how vegetative propagation works from roots, stems and leaves, why the offspring are clones, and what that costs a species.
Why is every banana of one variety genetically identical?
Because banana plants are grown from pieces of other banana plants, never from seed.
A commercial banana variety has lost the ability to make viable seeds, so growers propagate it by planting a sucker — a shoot from the base of an existing plant. That sucker is part of the parent, and it grows into a plant with exactly the parent's DNA.
Repeat that for generations and every plant of the variety is a copy of one original. They are clones, in the strict sense: genetically identical individuals.
That uniformity is the great advantage of asexual reproduction — a good variety is preserved perfectly. It is also the great risk, because a disease that can attack one plant can attack every plant of the variety, everywhere.
That trade-off between speed and uniformity on one side and variation on the other is the theme of this page. It covers the first part of the CBSE Class 9 Science chapter on reproduction.
A commercial banana variety has lost the ability to make viable seeds, so growers propagate it by planting a sucker — a shoot from the base of an existing plant. That sucker is part of the parent, and it grows into a plant with exactly the parent's DNA.
Repeat that for generations and every plant of the variety is a copy of one original. They are clones, in the strict sense: genetically identical individuals.
That uniformity is the great advantage of asexual reproduction — a good variety is preserved perfectly. It is also the great risk, because a disease that can attack one plant can attack every plant of the variety, everywhere.
That trade-off between speed and uniformity on one side and variation on the other is the theme of this page. It covers the first part of the CBSE Class 9 Science chapter on reproduction.
What are the modes of asexual reproduction?
Reproduction from a single parent, without gametes, and it takes several forms.
Binary fission. The parent cell divides into two equal daughter cells, and the parent effectively ceases to exist as a separate individual.
- Examples: Amoeba, Paramecium, and bacteria
- In Amoeba the division can occur in any plane, because the cell has no fixed shape
- In Leishmania, which has a whip-like flagellum at one end, fission occurs in a definite orientation relative to that structure
Multiple fission. The parent divides into many daughter cells at once. Example: Plasmodium.
Budding. A small outgrowth — a bud — appears on the parent's body, grows while still attached, and then detaches as a new individual.
- Examples: yeast and Hydra
- In yeast, a chain of buds can sometimes be seen still joined together
Fragmentation. The body of a simple multicellular organism breaks into fragments, and each fragment grows into a complete organism. Example: Spirogyra, a filamentous alga found in ponds.
Regeneration. A cut piece of an organism regrows the whole body. Examples: Planaria and Hydra. Cut a Planaria into several pieces and each piece can become a complete flatworm.
Spore formation. Specialised cells called spores are produced inside a sporangium, released into the air, and each germinates into a new organism when it lands somewhere favourable. Example: Rhizopus, the common bread mould.
Everyday evidence. Bread left in a humid place grows a cottony white mould dotted with tiny black knobs. Those knobs are the sporangia, each packed with spores, and they are black because the spores inside are. Yeast used in baking multiplies by budding while the dough rises.
Fragmentation and regeneration are not the same thing. In fragmentation the organism breaks up as part of its normal reproduction. In regeneration an organism damaged by accident rebuilds the missing part, and a whole new individual results only if the piece happens to be large enough. Regeneration is a repair ability that can produce reproduction; fragmentation is reproduction by design.
Binary fission. The parent cell divides into two equal daughter cells, and the parent effectively ceases to exist as a separate individual.
- Examples: Amoeba, Paramecium, and bacteria
- In Amoeba the division can occur in any plane, because the cell has no fixed shape
- In Leishmania, which has a whip-like flagellum at one end, fission occurs in a definite orientation relative to that structure
Multiple fission. The parent divides into many daughter cells at once. Example: Plasmodium.
Budding. A small outgrowth — a bud — appears on the parent's body, grows while still attached, and then detaches as a new individual.
- Examples: yeast and Hydra
- In yeast, a chain of buds can sometimes be seen still joined together
Fragmentation. The body of a simple multicellular organism breaks into fragments, and each fragment grows into a complete organism. Example: Spirogyra, a filamentous alga found in ponds.
Regeneration. A cut piece of an organism regrows the whole body. Examples: Planaria and Hydra. Cut a Planaria into several pieces and each piece can become a complete flatworm.
Spore formation. Specialised cells called spores are produced inside a sporangium, released into the air, and each germinates into a new organism when it lands somewhere favourable. Example: Rhizopus, the common bread mould.
Everyday evidence. Bread left in a humid place grows a cottony white mould dotted with tiny black knobs. Those knobs are the sporangia, each packed with spores, and they are black because the spores inside are. Yeast used in baking multiplies by budding while the dough rises.
Fragmentation and regeneration are not the same thing. In fragmentation the organism breaks up as part of its normal reproduction. In regeneration an organism damaged by accident rebuilds the missing part, and a whole new individual results only if the piece happens to be large enough. Regeneration is a repair ability that can produce reproduction; fragmentation is reproduction by design.
How does vegetative propagation work in plants?
A new plant grows from a vegetative part — a root, a stem or a leaf — with no seed involved.
It is asexual reproduction, and it happens naturally in many plants as well as being done deliberately by growers.
By the plant part involved:
- Roots: sweet potato, dahlia, carrot
- Stems: potato, where buds sit in the eyes of the tuber; ginger and turmeric, from underground stems; sugarcane, from the nodes of a cut piece; onion, from a bulb
- Leaves: Bryophyllum, where buds grow from notches in the leaf margin and fall off to root in the soil
The artificial methods growers use:
- Cutting — a piece of stem is planted and grows roots. Rose, sugarcane, Bougainvillea
- Layering — a branch is bent down and part of it buried, so it roots while still attached to the parent, and is then cut away. Jasmine, lemon
- Grafting — a shoot of a desirable variety, the scion, is joined to the rooted stem of a hardy plant, the stock, and the two grow together. Mango, apple, rose
- Tissue culture — a few cells are grown in a nutrient medium in the laboratory into many complete plantlets, allowing thousands of identical plants from a tiny amount of parent tissue
Why growers prefer it.
- Plants that no longer make viable seeds — banana, orange, jasmine, rose — can still be multiplied
- The new plants are genetically identical, so a desirable variety is preserved exactly, with the same fruit size, taste and colour
- They flower and fruit earlier than seed-grown plants, because the cutting is already at a mature stage
Everyday evidence. A potato left in a kitchen basket sprouts from its eyes. A piece of ginger buried in a pot produces new shoots. A Bryophyllum leaf lying on damp soil grows tiny plantlets all along its edges.
Vegetative propagation is a plant's version of the whole page's trade-off. It is fast, needs one parent, and guarantees the variety — and it produces no variation whatever. So an orchard grown this way is uniform and valuable, and uniformly vulnerable, which is the point the last section of this page develops.
It is asexual reproduction, and it happens naturally in many plants as well as being done deliberately by growers.
By the plant part involved:
- Roots: sweet potato, dahlia, carrot
- Stems: potato, where buds sit in the eyes of the tuber; ginger and turmeric, from underground stems; sugarcane, from the nodes of a cut piece; onion, from a bulb
- Leaves: Bryophyllum, where buds grow from notches in the leaf margin and fall off to root in the soil
The artificial methods growers use:
- Cutting — a piece of stem is planted and grows roots. Rose, sugarcane, Bougainvillea
- Layering — a branch is bent down and part of it buried, so it roots while still attached to the parent, and is then cut away. Jasmine, lemon
- Grafting — a shoot of a desirable variety, the scion, is joined to the rooted stem of a hardy plant, the stock, and the two grow together. Mango, apple, rose
- Tissue culture — a few cells are grown in a nutrient medium in the laboratory into many complete plantlets, allowing thousands of identical plants from a tiny amount of parent tissue
Why growers prefer it.
- Plants that no longer make viable seeds — banana, orange, jasmine, rose — can still be multiplied
- The new plants are genetically identical, so a desirable variety is preserved exactly, with the same fruit size, taste and colour
- They flower and fruit earlier than seed-grown plants, because the cutting is already at a mature stage
Everyday evidence. A potato left in a kitchen basket sprouts from its eyes. A piece of ginger buried in a pot produces new shoots. A Bryophyllum leaf lying on damp soil grows tiny plantlets all along its edges.
Vegetative propagation is a plant's version of the whole page's trade-off. It is fast, needs one parent, and guarantees the variety — and it produces no variation whatever. So an orchard grown this way is uniform and valuable, and uniformly vulnerable, which is the point the last section of this page develops.
Why are asexual offspring genetically identical to the parent?
Because only one parent is involved and only mitosis takes place.
The reasoning is short and worth holding in exactly this order:
- Asexual reproduction uses one parent, so there is no second set of DNA to combine with
- The cells divide by mitosis, which produces daughter cells with exactly the same DNA as the parent cell
- No gametes are formed, so there is no meiosis and no shuffling of chromosomes
- No fertilisation occurs, so no new combination of two parents' DNA is created
The result is a clone — an individual genetically identical to its parent and to every other offspring of that parent.
Everyday consequence. All the plants grown from cuttings of one rose bush bear the same colour of flower, with the same scent, in the same season. A gardener relies on that certainty, and it is why a named variety can be sold with a guarantee of what it will produce.
Where the tiny amount of variation comes from. DNA replication before mitosis is extremely accurate but not perfect, and occasional copying errors occur. Those rare changes are the only source of variation in a purely asexual population, which is why such populations remain nearly uniform over many generations.
This is exactly the point mitosis was described for. As the cell chapter of this course established, mitosis conserves the chromosome number and the genetic content, while meiosis halves the number and shuffles the chromosomes. Asexual reproduction uses only the first of those two processes, and every consequence on this page follows from that single fact.
Identical does not mean indistinguishable. Two cuttings from one plant grown in different soil, light and water will differ in height, leaf size and yield. Those differences are environmental, not genetic, and they are not inherited. So genetically identical is a precise claim about DNA and not a claim that the plants will look the same — a distinction worth making carefully, because questions test it.
The reasoning is short and worth holding in exactly this order:
- Asexual reproduction uses one parent, so there is no second set of DNA to combine with
- The cells divide by mitosis, which produces daughter cells with exactly the same DNA as the parent cell
- No gametes are formed, so there is no meiosis and no shuffling of chromosomes
- No fertilisation occurs, so no new combination of two parents' DNA is created
The result is a clone — an individual genetically identical to its parent and to every other offspring of that parent.
Everyday consequence. All the plants grown from cuttings of one rose bush bear the same colour of flower, with the same scent, in the same season. A gardener relies on that certainty, and it is why a named variety can be sold with a guarantee of what it will produce.
Where the tiny amount of variation comes from. DNA replication before mitosis is extremely accurate but not perfect, and occasional copying errors occur. Those rare changes are the only source of variation in a purely asexual population, which is why such populations remain nearly uniform over many generations.
This is exactly the point mitosis was described for. As the cell chapter of this course established, mitosis conserves the chromosome number and the genetic content, while meiosis halves the number and shuffles the chromosomes. Asexual reproduction uses only the first of those two processes, and every consequence on this page follows from that single fact.
Identical does not mean indistinguishable. Two cuttings from one plant grown in different soil, light and water will differ in height, leaf size and yield. Those differences are environmental, not genetic, and they are not inherited. So genetically identical is a precise claim about DNA and not a claim that the plants will look the same — a distinction worth making carefully, because questions test it.
What does a species gain and lose by reproducing asexually?
It gains speed and certainty, and loses the variation that lets it survive change.
The advantages:
- Fast. No mate has to be found, no gametes made, no fertilisation to wait for. A bacterium can divide in a matter of minutes
- Only one parent needed, so a single individual arriving in a new place can establish a whole population
- Less energy spent, since nothing is invested in flowers, nectar, pollen, courtship or gametes
- Well-adapted offspring in a stable environment, because a parent that is suited to its surroundings produces offspring exactly as suited
The limitations:
- No variation, so the population cannot adapt if the conditions change
- A single threat can destroy everything. A disease or a pest that can attack one individual can attack them all, because every one has the same defences and the same weaknesses
- Crowding. Offspring appear in the same place as the parent and compete with it and each other for the same light, water and nutrients
Everyday evidence for the central risk. A field planted with a single clonal variety of a crop can be lost entirely to one disease, while a field of mixed traditional varieties usually contains some plants that resist it and survive. The uniformity that makes the clonal crop valuable is the same uniformity that makes it vulnerable.
Variation is a form of insurance, and asexual reproduction does not buy it. In unchanging conditions the premium is wasted and asexual reproduction wins on every count — speed, cost and certainty. The moment conditions change, the insurance is what matters, and a population with no variation has none.
That is why sexual reproduction persists despite being worse on paper. It is slower, needs two parents, costs far more energy and produces fewer offspring. It survives because it generates variation, and variation is worth all of that — which is precisely what the next parts of this chapter set out to show, first in plants and then in animals.
The advantages:
- Fast. No mate has to be found, no gametes made, no fertilisation to wait for. A bacterium can divide in a matter of minutes
- Only one parent needed, so a single individual arriving in a new place can establish a whole population
- Less energy spent, since nothing is invested in flowers, nectar, pollen, courtship or gametes
- Well-adapted offspring in a stable environment, because a parent that is suited to its surroundings produces offspring exactly as suited
The limitations:
- No variation, so the population cannot adapt if the conditions change
- A single threat can destroy everything. A disease or a pest that can attack one individual can attack them all, because every one has the same defences and the same weaknesses
- Crowding. Offspring appear in the same place as the parent and compete with it and each other for the same light, water and nutrients
Everyday evidence for the central risk. A field planted with a single clonal variety of a crop can be lost entirely to one disease, while a field of mixed traditional varieties usually contains some plants that resist it and survive. The uniformity that makes the clonal crop valuable is the same uniformity that makes it vulnerable.
Variation is a form of insurance, and asexual reproduction does not buy it. In unchanging conditions the premium is wasted and asexual reproduction wins on every count — speed, cost and certainty. The moment conditions change, the insurance is what matters, and a population with no variation has none.
That is why sexual reproduction persists despite being worse on paper. It is slower, needs two parents, costs far more energy and produces fewer offspring. It survives because it generates variation, and variation is worth all of that — which is precisely what the next parts of this chapter set out to show, first in plants and then in animals.
Exam tip
Exam tip: give the mode with its example and the part involved
Always pair a mode with its organism: binary fission — Amoeba; multiple fission — Plasmodium; budding — yeast and Hydra; fragmentation — Spirogyra; regeneration — Planaria; spore formation — Rhizopus.
Note that fission in Leishmania has a definite orientation relative to its flagellum — a detail asked about specifically.
Fragmentation is normal reproduction; regeneration is repair that can produce a new individual.
For vegetative propagation, name the plant part: roots in sweet potato and dahlia, stems in potato (eyes), ginger, sugarcane (nodes) and onion, leaves in Bryophyllum (notches).
Name the artificial methods with an example: cutting (rose), layering (jasmine), grafting (mango, with scion and stock), tissue culture.
Give three reasons growers use it: seedless varieties can be multiplied, the variety is preserved exactly, and plants fruit earlier.
For why are offspring identical, answer with the chain: one parent, mitosis only, no gametes, no meiosis, no fertilisation — therefore clones.
Genetically identical is not physically identical — soil, light and water still make plants differ, and those differences are not inherited.
Give advantages and limitations as a balanced pair when asked, and name lack of variation as the central limitation.
And write organism names in italics where you can, as the syllabus does.
Note that fission in Leishmania has a definite orientation relative to its flagellum — a detail asked about specifically.
Fragmentation is normal reproduction; regeneration is repair that can produce a new individual.
For vegetative propagation, name the plant part: roots in sweet potato and dahlia, stems in potato (eyes), ginger, sugarcane (nodes) and onion, leaves in Bryophyllum (notches).
Name the artificial methods with an example: cutting (rose), layering (jasmine), grafting (mango, with scion and stock), tissue culture.
Give three reasons growers use it: seedless varieties can be multiplied, the variety is preserved exactly, and plants fruit earlier.
For why are offspring identical, answer with the chain: one parent, mitosis only, no gametes, no meiosis, no fertilisation — therefore clones.
Genetically identical is not physically identical — soil, light and water still make plants differ, and those differences are not inherited.
Give advantages and limitations as a balanced pair when asked, and name lack of variation as the central limitation.
And write organism names in italics where you can, as the syllabus does.
Did you know
Why one flatworm can become many
Cut an earthworm in half and you get a damaged earthworm. Cut a Planaria flatworm in half and you get two flatworms.
The difference lies in how many cells in the body retain the ability to become any kind of cell. In Planaria, a large population of such unspecialised cells is distributed throughout the body, so almost any piece still contains the means to rebuild a head, a gut and a tail. In most animals those cells are scarce or gone by adulthood, and a severed part can only heal.
The ability shades gradually into ordinary repair. A Hydra cut into pieces regrows completely. A lizard regrows a lost tail but nothing more. A human heals a cut in the skin and regenerates part of the liver, but cannot regrow a finger. It is one ability present in different amounts, not a special power that some animals have and others lack.
And the reason it counts as reproduction in some cases and not others is arithmetic rather than biology: if the process ends with more individuals than it started with, it has reproduced. A Planaria cut into five pieces becomes five flatworms; a lizard with a new tail is still one lizard.
This also explains why regeneration tends to appear in structurally simple animals. Rebuilding a whole Planaria means arranging a few tissue types in the right order. Rebuilding a human arm would mean reconstructing bone, muscle, blood vessels, nerves and skin in exact relation to one another — an enormously harder problem, and one that a body with few unspecialised cells left has no means to attempt.
So the plants propagated from cuttings earlier on this page and the flatworm cut into pieces are doing the same thing. In both, a fragment of a parent contains enough unspecialised cells to build the whole organism again — and in both, the result is a clone.
The difference lies in how many cells in the body retain the ability to become any kind of cell. In Planaria, a large population of such unspecialised cells is distributed throughout the body, so almost any piece still contains the means to rebuild a head, a gut and a tail. In most animals those cells are scarce or gone by adulthood, and a severed part can only heal.
The ability shades gradually into ordinary repair. A Hydra cut into pieces regrows completely. A lizard regrows a lost tail but nothing more. A human heals a cut in the skin and regenerates part of the liver, but cannot regrow a finger. It is one ability present in different amounts, not a special power that some animals have and others lack.
And the reason it counts as reproduction in some cases and not others is arithmetic rather than biology: if the process ends with more individuals than it started with, it has reproduced. A Planaria cut into five pieces becomes five flatworms; a lizard with a new tail is still one lizard.
This also explains why regeneration tends to appear in structurally simple animals. Rebuilding a whole Planaria means arranging a few tissue types in the right order. Rebuilding a human arm would mean reconstructing bone, muscle, blood vessels, nerves and skin in exact relation to one another — an enormously harder problem, and one that a body with few unspecialised cells left has no means to attempt.
So the plants propagated from cuttings earlier on this page and the flatworm cut into pieces are doing the same thing. In both, a fragment of a parent contains enough unspecialised cells to build the whole organism again — and in both, the result is a clone.
Exam relevance
Why does NEET keep returning to modes of reproduction?
Because the mode-and-example pairings on this page are pure recall of exactly the kind NEET favours, and they are assumed by two whole Class 12 chapters.
This is the foundation for the Class 12 Biology chapter Reproduction in Organisms, a standing part of the NEET syllabus, which begins with the same list of asexual modes and the same organisms. That chapter adds conidia in Penicillium, gemmules in sponges, zoospores in some algae, and the special plant structures — runners, rhizomes, suckers, tubers, offsets and bulbils in Agave — each with its own example. Every one of those is learned in the same format used here, so the habit of pairing a mode with its organism is what makes the later list manageable.
Vegetative propagation feeds into Class 12 Plant Breeding and Crop Improvement within Biotechnology and its Applications, where tissue culture and micropropagation are treated in detail, along with the production of disease-free clones. The Class 9 observation that a clonal crop is uniformly vulnerable is exactly the problem that chapter addresses.
The mitosis-therefore-clone argument connects backwards to the cell chapter of this course and forwards to Class 12 Principles of Inheritance and Variation, where the contrast between mitotic and meiotic products becomes the whole basis of genetics.
The advantages-and-limitations comparison is the entry point to Class 12 Evolution, where variation as the raw material of natural selection is developed formally.
What the questions look like. Match-the-column items pairing an organism with its mode of reproduction are the single commonest form in NEET on this material, and the pairs most often confused are Plasmodium (multiple fission) against Amoeba (binary fission), and Spirogyra (fragmentation) against Planaria (regeneration). Statement-count questions of the how many of the following reproduce by budding kind suit the topic because there are so many small pairings. Assertion-reason items favour the claim that asexual offspring are genetically identical, paired with a reason about mitosis.
How board and competitive emphasis differ. A board paper asks you to describe binary fission with a diagram, explain vegetative propagation with three examples, and give three advantages of asexual reproduction. A NEET item gives the organism and asks for the mode, or gives a plant part and asks which method uses it — so the examples carry far more weight than the descriptions, and a candidate who learned the processes without the organisms has prepared for only one paper.
The single trap that costs the most marks. Confusing fragmentation with regeneration. Fragmentation is a normal mode of reproduction in a simple multicellular organism such as Spirogyra; regeneration is the rebuilding of a damaged body, as in Planaria, and produces new individuals only incidentally. The examples are the giveaway, and learning them together settles it.
A second trap worth naming. Calling vegetative propagation a form of sexual reproduction because it happens in flowering plants. It involves one parent, no gametes and no fertilisation, so it is firmly asexual — and the presence of flowers on the plant is irrelevant to how that particular plant was produced.
This is the foundation for the Class 12 Biology chapter Reproduction in Organisms, a standing part of the NEET syllabus, which begins with the same list of asexual modes and the same organisms. That chapter adds conidia in Penicillium, gemmules in sponges, zoospores in some algae, and the special plant structures — runners, rhizomes, suckers, tubers, offsets and bulbils in Agave — each with its own example. Every one of those is learned in the same format used here, so the habit of pairing a mode with its organism is what makes the later list manageable.
Vegetative propagation feeds into Class 12 Plant Breeding and Crop Improvement within Biotechnology and its Applications, where tissue culture and micropropagation are treated in detail, along with the production of disease-free clones. The Class 9 observation that a clonal crop is uniformly vulnerable is exactly the problem that chapter addresses.
The mitosis-therefore-clone argument connects backwards to the cell chapter of this course and forwards to Class 12 Principles of Inheritance and Variation, where the contrast between mitotic and meiotic products becomes the whole basis of genetics.
The advantages-and-limitations comparison is the entry point to Class 12 Evolution, where variation as the raw material of natural selection is developed formally.
What the questions look like. Match-the-column items pairing an organism with its mode of reproduction are the single commonest form in NEET on this material, and the pairs most often confused are Plasmodium (multiple fission) against Amoeba (binary fission), and Spirogyra (fragmentation) against Planaria (regeneration). Statement-count questions of the how many of the following reproduce by budding kind suit the topic because there are so many small pairings. Assertion-reason items favour the claim that asexual offspring are genetically identical, paired with a reason about mitosis.
How board and competitive emphasis differ. A board paper asks you to describe binary fission with a diagram, explain vegetative propagation with three examples, and give three advantages of asexual reproduction. A NEET item gives the organism and asks for the mode, or gives a plant part and asks which method uses it — so the examples carry far more weight than the descriptions, and a candidate who learned the processes without the organisms has prepared for only one paper.
The single trap that costs the most marks. Confusing fragmentation with regeneration. Fragmentation is a normal mode of reproduction in a simple multicellular organism such as Spirogyra; regeneration is the rebuilding of a damaged body, as in Planaria, and produces new individuals only incidentally. The examples are the giveaway, and learning them together settles it.
A second trap worth naming. Calling vegetative propagation a form of sexual reproduction because it happens in flowering plants. It involves one parent, no gametes and no fertilisation, so it is firmly asexual — and the presence of flowers on the plant is irrelevant to how that particular plant was produced.
Key takeaways
Asexual reproduction and vegetative propagation: quick revision
- Asexual reproduction uses one parent and no gametes.
- Binary fission: the cell divides into two — Amoeba, Paramecium, bacteria. In Leishmania it has a definite orientation.
- Multiple fission: many daughters at once — Plasmodium.
- Budding: an outgrowth grows and detaches — yeast, Hydra.
- Fragmentation: the body breaks into pieces that each grow — Spirogyra.
- Regeneration: a cut piece rebuilds the whole organism — Planaria, Hydra. This is repair, not a normal mode.
- Spore formation: spores made in a sporangium germinate where they land — Rhizopus, the black knobs on bread mould.
- Vegetative propagation grows a new plant from a root, stem or leaf.
- Roots: sweet potato, dahlia. Stems: potato (eyes), ginger, turmeric, sugarcane (nodes), onion (bulb). Leaves: Bryophyllum (notches).
- Artificial methods: cutting (rose), layering (jasmine), grafting (mango — scion onto stock), tissue culture.
- Growers use it because seedless varieties such as banana, orange and jasmine can still be multiplied, the variety is preserved exactly, and plants fruit earlier.
- Offspring are clones because there is one parent, only mitosis, no gametes, no meiosis and no fertilisation.
- The only variation comes from rare copying errors during DNA replication.
- Genetically identical is not physically identical — soil, light and water still cause differences, and those are not inherited.
- Advantages: fast, one parent needed, less energy, and offspring as well adapted as the parent in a stable environment.
- Limitations: no variation, so no adaptation to change; one disease can destroy the whole population; and crowding around the parent.
- Variation is insurance, and asexual reproduction does not buy it — which is why sexual reproduction persists despite being slower and costlier.
List six organisms and name the mode each uses without looking — if all six pairings come straight out, this topic will never cost you a mark.
- Binary fission: the cell divides into two — Amoeba, Paramecium, bacteria. In Leishmania it has a definite orientation.
- Multiple fission: many daughters at once — Plasmodium.
- Budding: an outgrowth grows and detaches — yeast, Hydra.
- Fragmentation: the body breaks into pieces that each grow — Spirogyra.
- Regeneration: a cut piece rebuilds the whole organism — Planaria, Hydra. This is repair, not a normal mode.
- Spore formation: spores made in a sporangium germinate where they land — Rhizopus, the black knobs on bread mould.
- Vegetative propagation grows a new plant from a root, stem or leaf.
- Roots: sweet potato, dahlia. Stems: potato (eyes), ginger, turmeric, sugarcane (nodes), onion (bulb). Leaves: Bryophyllum (notches).
- Artificial methods: cutting (rose), layering (jasmine), grafting (mango — scion onto stock), tissue culture.
- Growers use it because seedless varieties such as banana, orange and jasmine can still be multiplied, the variety is preserved exactly, and plants fruit earlier.
- Offspring are clones because there is one parent, only mitosis, no gametes, no meiosis and no fertilisation.
- The only variation comes from rare copying errors during DNA replication.
- Genetically identical is not physically identical — soil, light and water still cause differences, and those are not inherited.
- Advantages: fast, one parent needed, less energy, and offspring as well adapted as the parent in a stable environment.
- Limitations: no variation, so no adaptation to change; one disease can destroy the whole population; and crowding around the parent.
- Variation is insurance, and asexual reproduction does not buy it — which is why sexual reproduction persists despite being slower and costlier.
List six organisms and name the mode each uses without looking — if all six pairings come straight out, this topic will never cost you a mark.