ASEXUAL REPRODUCTION
Before looking at sexual reproduction, where two organisms mix their genetic material to make a third, let's take a look at asexual reproduction, which results basically in a clone!
K’iidK’iyaas
To get started with the different cloning mechanisms found in nature, let's take a look at a very special tree.
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For 300 years, it stood. The lone 50 m Sitka spruce glowed golden in all its genetically mutated glory, alone in the middle of emerald-coloured trees on the banks of Haida Gwaii’s Yakoun River. Sacred among the Haida, who know it as K’iid K’iyaas (Ancient Tree), it was also called more popularly the Golden Spruce.
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Today, the tree is gone. Let's check out how, in 1997, one dude pooped on everyone's cornflakes out of a spite so pure, it knocked his mind right off its hinges.
You may be asking yourself, how is this story relevant to asexual reproduction?
Well, as it turns out, in 1977 -- exactly 20 years before the great Golden Spruce was cut down -- a group of botanists from UBC visited Haida Gwaii to take cuttings of K’iid K’iyaas.
These cuttings were grafted onto ordinary Sitka spruce, resulting in two golden saplings. The trees were grown in the UBC Botanical Garden and Centre for Plant Research. Upon hearing of the tree's destruction in 1997, the arboretum offered one of the two young trees to replace Kiidk'yaas. However, the sapling died in storage before it could be transported to Haida Gwaii. The second sapling survives at UBC.
After Kiidk'yaas' felling, attempts were made to propagate a further 100 cuttings (with the permission of the Haida people) in order to increase the chances of a successful offspring surviving. From these, around 60 cuttings still survive.
Currently, the biggest and oldest surviving cutting is the original one from 1977, which can be seen at UBC, and it is more of a shrub than a tree. When a cutting is made, the material used as a scion (grafted material) is a branch, which is then grafted onto a strong rootstock (the existing green spruce, in this case.) But the branch does not know that it should be a trunk, and it takes time to train itself into develping a "leader" (a single strong trunk which reaches to the sky).
We will see more about grafting later on!
All of the little cuttings from the Golden Spruce are clones of the original; these are examples of man-assisted asexual reproduction.
What do you think of when you hear the word "clone"?
In our bodies, what cells do you think reproduce asexually? Why would this be?
Well, as it turns out, in 1977 -- exactly 20 years before the great Golden Spruce was cut down -- a group of botanists from UBC visited Haida Gwaii to take cuttings of K’iid K’iyaas.
These cuttings were grafted onto ordinary Sitka spruce, resulting in two golden saplings. The trees were grown in the UBC Botanical Garden and Centre for Plant Research. Upon hearing of the tree's destruction in 1997, the arboretum offered one of the two young trees to replace Kiidk'yaas. However, the sapling died in storage before it could be transported to Haida Gwaii. The second sapling survives at UBC.
After Kiidk'yaas' felling, attempts were made to propagate a further 100 cuttings (with the permission of the Haida people) in order to increase the chances of a successful offspring surviving. From these, around 60 cuttings still survive.
Currently, the biggest and oldest surviving cutting is the original one from 1977, which can be seen at UBC, and it is more of a shrub than a tree. When a cutting is made, the material used as a scion (grafted material) is a branch, which is then grafted onto a strong rootstock (the existing green spruce, in this case.) But the branch does not know that it should be a trunk, and it takes time to train itself into develping a "leader" (a single strong trunk which reaches to the sky).
We will see more about grafting later on!
All of the little cuttings from the Golden Spruce are clones of the original; these are examples of man-assisted asexual reproduction.
What do you think of when you hear the word "clone"?
In our bodies, what cells do you think reproduce asexually? Why would this be?
Big Topics For This Page!
Our topics for this page are:
Let's get started!!!
- Binary Fission
- Budding
- Spores
- Vegetative propagation
Let's get started!!!
Fun in your Gut
Ahhh, bacteria! Our tiny little passengers, occupying every single surface of our bodies, both inside and out. From the surface of your desk, to the inside of our bodies, to extreme environments of the planet, bacteria are all around us.
Bacteria are micro-organisms that exist as single prokaryotic cells (that means they don't have a nucleus envelope!).
Bacteria are micro-organisms that exist as single prokaryotic cells (that means they don't have a nucleus envelope!).
Even though you cannot keep an individual bacterium as a pet, it behaves just like any other living thing. To survive, it must be able to make more of its own kind. It must be able to reproduce. Bacteria reproduce asexually by a process called binary fission.
Binary Fission
In this process, a parent cell produces two individual, identical cells. The identical cells that form from the parent cell are called daughter cells, and they contain the same DNA, or genetic material.
Seeing Double
After each cycle of binary fission, the number of cells doubles. The time for many bacteria to double (called doubling time) is 20 to 30 min, so a small population can grow quickly to millions under the right conditions.
What conditions do you think affect bacterial growth, and how do they affect it?
What conditions do you think affect bacterial growth, and how do they affect it?
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Click on thumbnail for answer, and reveal below!
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Now it's your turn -- work on the bacteria reflection sheet (because why not?) and return it to Mrs J for her to see how is your knowledge of our tiny friends!
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Budding
No, I don't mean making friends. Budding is a method of asexual reproduction in which a small bud forms on the side of an organism, like a lump, and this lump detaches and grows into a new organism.
Let's take a look at yeast, which is a part of the fungi kingdom!
Although yeast is too small to see without a microscope, you are probably familiar with them from the products that these micro-organisms are used to make. These include dough for pizza and bread, pretzels, soy sauce, cheese, and vinegar.
Let's take a look at yeast, which is a part of the fungi kingdom!
Although yeast is too small to see without a microscope, you are probably familiar with them from the products that these micro-organisms are used to make. These include dough for pizza and bread, pretzels, soy sauce, cheese, and vinegar.
Mrs J loves baking bread. She has a yeast culture that is 5 years old! The name of the culture is Gertrude (Gerdie for short.)
To see budding in action, let's feed a small sample of Gerdie and see what happens!
Something weird is going on - what is happening inside??
To see budding in action, let's feed a small sample of Gerdie and see what happens!
Something weird is going on - what is happening inside??
The Gerdie Lab
- With a partner, place the tablespoon of gerdie in a beaker with about 20 mL of warm water.
- Add about 5 g of sugar and mix by gently swirling the flask.
- Place a balloon around the neck of the flask and watch for 10 min.
How can you explain what you observe? Develop one or more questions about what is happening that could be investigated.
- What do you think will happen?
- How can you explain what you observe?
- Develop one or more questions about what is happening that could be investigated.
What is happening?
Yeast releases carbon dioxide gas as a waste product of alcoholic fermentation, a process where yeast digests sugars and starches for energy to grow and reproduce. The consumption of sugars from flour and other sources provides the yeast with the fuel it needs, and the carbon dioxide (CO₂) is expelled, creating the bubbles and lift in leavened dough. It also expels alcohol as a byproduct, and creates the ethanol in alcoholic beverages!
Like bacteria, yeasts are unicellular organisms. Unlike bacteria, yeasts are eukaryotes. This means their DNA is organized inside a nuclear envelope! The most common way that yeast cells reproduce is by a type of asexual reproduction called budding. Since yeast cells are eukaryotic, their reproduction involves mitosis. However, a yeast cell will grow a bud that pinches off to become a separate cell. This new cell is smaller than the original cell at first. It eventually grows to the same size as other yeast cells. Cute, right?
On the diagram above, we can see budding in effect.
There is something in it that indicate to us that this is an eukariotic cell! What do you think it is?
Budding is a neat process that can happen in unicellular individuals but also in multicellular ones. A good example of a multicellular organism that uses budding ( and can be seen with the naked eye) is a hydra!
Hydra is a tiny fresh water creature, just a half centimetre long. Budding in hydra involves a small bud which is developed from the momma hydra through the repeated mitotic division of its cells. The small bud keeps getting nutrients from the mother, and grows healthy.
There is something in it that indicate to us that this is an eukariotic cell! What do you think it is?
Budding is a neat process that can happen in unicellular individuals but also in multicellular ones. A good example of a multicellular organism that uses budding ( and can be seen with the naked eye) is a hydra!
Hydra is a tiny fresh water creature, just a half centimetre long. Budding in hydra involves a small bud which is developed from the momma hydra through the repeated mitotic division of its cells. The small bud keeps getting nutrients from the mother, and grows healthy.
Finally, the baby hydra develops small tentacles and a tiny mouth. The newly produced hydra gets kicked off ("you got a mouth, buddy, use it!") and becomes an independent organism. Eventually, it gets as big as its parent cell, and the cycle continues!
- In what ways the reproduction of a bacteria is similar to the reproduction of a yeast cell?
- In what ways is it different?
Spores
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Perhaps you have experienced a situation like this. One day at school, you don’t have time to finish your sandwich at lunch. You decide to save the rest of it for later. After wrapping it in plastic wrap, you put it in your locker—but forget about it.
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A week later, you find it in the back of your locker. But it is now covered with black or green fuzzy-looking material. How did this happen?
The fuzzy material that grew on the sandwich is a type of mould, another member of the Fungi Kingdom. It is composed of many eukaryotic cells. This type of mould has a fuzzy or hairy appearance because of how the long thread-like cells weave together.
Mould can break down food to use as nutrients. It also has structures that help to anchor it to the food. But what did the mould grow from?
Mould can break down food to use as nutrients. It also has structures that help to anchor it to the food. But what did the mould grow from?
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The most common way that moulds reproduce is by the formation of spores that are genetically identical to the mould cells they come from. The spores are released into the air from a structure called a sporangium.
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When a spore lands in a favourable environment—such as a piece of bread in a warm, moist environment—it begins to grow and divide by mitosis and cytokinesis and eventually produces more mould.
Moulds are used to make food products, but they can also be found growing in dark, damp places in schools and homes. Their spores can cause sickness.
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Mould goes rogue
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Mould Vs. Bacteria Showdown
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Moulds reproduce using spores that grow into a new mould by mitosis. Why is this a type of asexual reproduction?
Vegetative Propagation
(Veggies are alive too)
Plants can reproduce both sexually and asexually.
Asexual reproduction in plants is called vegetative propagation. New plants grow from a portion of the roots, stems, or leaves of an existing plant. Because the new plants are formed by asexual reproduction, they are copies, or clones, of the parent plant. Let's take a look at some of the ways plants naturally reproduce asexually without interference:
Asexual reproduction in plants is called vegetative propagation. New plants grow from a portion of the roots, stems, or leaves of an existing plant. Because the new plants are formed by asexual reproduction, they are copies, or clones, of the parent plant. Let's take a look at some of the ways plants naturally reproduce asexually without interference:
Runners
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Strawberry plants use a cool system called runners. One strawberry plant throws a long stem that grows horizontally.
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When it is far enough away, a small little plant will start growing from it. Once the plant attaches to the ground and is able to feed itself, the runner detaches and dies off.
Bulbs
Some plants, like onions, tulips and garlic, reproduce by sprouting bulbs. At the bottom of these plants, they each have a bulb, which holds nutrients in layers. To reproduce, the parent bulb produces smaller bulbs that appear between its external layers. When the parent plant dies, the new bulbs stay, and they come back the following season.
Tubers
There are two kinds of tubers: stem tubers and root tubers. Stem tubers happen when parts of the stem swell up underground, while root tubers happen when parts of the root swell up underground.
You can tell the difference between these in the supermarket right away; stem tubers have eyes, like potatoes. They use the eyes to grow new shoots, from where a whole new plant can develop. If you leave a potato alone for a while, it will grow a tiny shoot. You can grow a whole new plant just from that shoot alone.
Root tubers don't have eyes -- they may have some weird roots coming from it, particularly from the end which is furthest away from the plant.
Both tuber formations serve to store nutrients and water, just like the tail on a leopard gecko!
A family of fat potatoes.
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A single fat potato.
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The three methods described above are all asexual methods of reproduction, and can happen naturally without human interference. In order to produce food for the masses, humans feel the need to get involved, as growing the right flavour, aroma and appearance often takes more than just luck.
Let's look at...
Let's look at...
Artificial vegetative Propagation
Farmers, gardeners, and people who work in plant nurseries use artificial vegetative propagation to produce plants with specific characteristics. This method uses a plant’s natural ability to asexually reproduce. This type of propagation is used to produce a large number of plants, consistently and quickly, to meet specific needs. Let's take a look at some of the most common types of artificial vegetative propagation.
Grafting
Grafting involves joining a piece of a desired plant, the scion, onto the strong root system of another plant, the rootstock. The scion, containing vegetative buds, ensures the desired fruit, flower, or foliage will grow; the rootstock provides a healthy, compatible foundation. For the tree to survive, it is important to match the vascular layers together, so that the new attached piece can get the proper nutrients.
Grafting Sequence
- Preparation: Gather scion wood and the rootstock.
- Making Cuts: Make matching cuts on both the scion and the rootstock to create a fit.
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- Alignment: Place the scion onto the rootstock, ensuring the vascular layers make contact.
- Securing: tie the two parts together with tape to hold them in place, seal the graft, and prevent moisture loss.
- Healing: The tree's natural wound-healing response will cause the layers to grow together, forming a permanent graft union.
Grafting is a super useful technique used in horticulture to create clones of specific plants, such as apple and pear trees, nut trees such as walnut and almonds, and grapevines!
This method can ensure a certain flavour, pest and winter resistance, and also help farmers develop new varieties.
This method can ensure a certain flavour, pest and winter resistance, and also help farmers develop new varieties.
No Way
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Apple trees, for instance, can't be commercially grown from seed, as the trees that come from seed are the product of sexual reproduction.
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As it turns out, apples are all one species, just like dogs are one species. This means each little flower may have been pollinated by any other kind of apple flower, including crab apples and other less desirable varieties.
That's the same as dogs, who can have all sorts of weird babies if we mix their breeds!
That's the same as dogs, who can have all sorts of weird babies if we mix their breeds!
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Twinsies!
So, the genetic material of the offspring is unpredictable; it can taste wrong, mature at the wrong time, or just be a complete lumpy mess. This is why farmers graft their trees -- in fact, every single specific type of apple comes from a clone of the same tree!
Splitting
With splitting, a plant is allowed to grow a bunch of babies, which stay all together and form a clump. Humans then section parts of the giant bundle and separate them, creating several plants instead of one. This is really useful for tulips and daffodils, for instance.
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The cuts are done from top to bottom, in a way that each plant gets roots and leaves, and so they can survive. This can be useful in gardening to trim down plants which have taken over a whole area, or to help older plants get their strength back so they can bloom again!
Cutting
Part of a leaf, stem, or root is cut from a plant and placed in water with nutrients or potting soil. Cells near the cut surface develop into roots or shoots. The new roots supply water and nutrients, and each shoot forms a new plant.
From a leaf
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From a stem
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You can use it to create new plants from herbs such as sage, oregano, basil, and thyme; trees such as pine, spruce, poplar, willow, and elm; grapevines; flowering bushes such as rose and lilac; chrysanthemums; carnations. This can be helpful when trying to produce large numbers of plants for consumers, and is also used by flower growers to start new plants in a greenhouse during winter.
Simple Layering
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In this type of reproduction, humans are helping just a little. A section of stem is bent to touch the ground. Then a cut is made in it to promote the growth of roots.
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The cut part of the stem is buried in the ground, and a hook stops it from rising up. Once a new root system develops, the stem is cut away from the parent plant. This is used to replicate climbing roses, grapevines, honeysuckle, junipers, willows, hydrangeas.
Air Layering
This is another way to reproduce apples! A strip of outer bark is removed from momma tree, and moss is packed around the stem. Plastic is wrapped around the moss to prevent water loss. Once a new root system appears, the stem is cut away from the parent plant and planted in soil.
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This is useful for tropical plants like rubber trees, magnolias, holly, lilac, and also fruit trees like apple, pear, orange and nut trees like pecan.
This technique works wonders to reproduce plants that might be hard to reproduce otherwise.
This technique works wonders to reproduce plants that might be hard to reproduce otherwise.
Tissue Culture
Finally, my favourite method! You know how every one of our cells has our DNA? What if we could grow a whole human in a little petri dish?
In tissue culture, an individual cell or a small piece of plant is placed in or on nutrients that promote shoot and root growth. Tiny plantlets develop and these are planted in soil!
In tissue culture, an individual cell or a small piece of plant is placed in or on nutrients that promote shoot and root growth. Tiny plantlets develop and these are planted in soil!
This is useful for reproducing a variety of ferns and ornamental plants, as well as a variety of trees. The tissue culture is used by nurseries to produce large quantities of plants; it allows new crops to be bred in the laboratory for desirable features, and then be made available to growers in massive amounts. This can also be used in forestry for the regeneration of tree plantations.
From Ferns to Planet Rescue
Tissue culture isn’t just for cloning potatoes or greenhouse flowers. Around the world, scientists use this method to protect endangered plants and restore ecosystems.
- Saving Native Plants in B.C.: Conservation groups are using propagation to re-establish native species such as camas and Garry oak ecosystems, which are vital food sources and cultural resources for First Peoples.
- Rescuing Rare Species: Globally, rare orchids, ferns, and even ancient trees like the Wollemi pine have been saved from extinction using tissue culture. By creating plant “clones” in the lab, scientists can grow thousands of new individuals to repopulate wild habitats.
- Climate Action in Action: Restoring native plants doesn’t just save species—it strengthens ecosystems, supports pollinators, prevents erosion, and helps fight climate change by storing carbon.
Think About It:
If you were a scientist, which endangered or native plant would you want to save with tissue culture, and why?
If you were a scientist, which endangered or native plant would you want to save with tissue culture, and why?
