0610 · 16.1Asexual reproduction

Asexual reproduction and clones

0:00Imagine planting one strawberry plant and later finding several smaller plants spreading out around it. You did not plant seeds, yet there are new plants growing their own roots and leaves. Where did they come from? In this video, we will explain how one parent can produce genetically identical offspring, how to recognise examples of this process, and why it can be both useful and risky. First, you need one idea about inheritance.

0:24Organisms contain genetic information, which provides instructions that influence their characteristics. Offspring inherit genetic information from their parent or parents. If offspring receive copies of the genetic information from just one parent, rather than a mixture from two parents, they can be genetically identical to that parent. Asexual reproduction is a process resulting in the production of genetically identical offspring from one parent. Every part of that definition matters. Reproduction produces new organisms, not just extra body parts.

0:53One parent supplies the genetic information, and genetically identical means that the offspring have the same genetic information as that parent. Genetically identical organisms are called clones. Think of copying a set of instructions rather than combining two different sets. Asexual reproduction does not involve the fusion of sex cells, so genetic information from two parents is not combined. The details of cell division come later in the video on inheritance.

1:17Here, we need to understand how whole new organisms are produced.

Examples of asexual reproduction

1:21One clear example is binary fission in bacteria. A bacterial cell copies its genetic material and then divides into two cells. Each new cell receives a copy of the genetic information, so the offspring are genetically identical. This is reproduction because one organism has become two organisms, rather than simply becoming a larger bacterial cell. Another example is budding in yeast, which is a single-celled fungus. A small outgrowth, called a bud, forms on the parent cell and grows.

1:48A copy of the parent’s genetic information passes into the bud, which can eventually separate as a new yeast cell. In a diagram, look for a smaller cell growing from the side of a larger one. Plants can also reproduce asexually, using structures such as stems or storage organs. In strawberries, a runner is a horizontal stem that grows away from the parent along the ground. A new plant develops along the runner and forms its own roots and leaves.

2:12Because it develops from the parent without the fusion of sex cells, it is genetically identical to the parent. Potatoes provide another example. A potato tuber is a swollen underground stem containing stored food, and its eyes are buds that can grow into shoots. When a tuber is planted, these buds can develop into a new potato plant. The tuber is not a seed, and the new plant receives its genetic information from the plant that produced the tuber.

2:36Bulbs, such as those of onions, can produce daughter bulbs that develop into new plants. Spider plants produce small plantlets on stems extending from the parent, and these plantlets can develop roots and grow independently. These examples look different, but the underlying idea is the same. A new organism develops from one parent and inherits a copy of that parent’s genetic information.

Identifying asexual reproduction

2:57When identifying asexual reproduction from a photograph or description, do not rely only on recognising the species. Look for evidence of the process. Is a cell dividing, a bud forming, or a new plant developing from a runner, tuber, bulb or plantlet? Simply seeing a plant grow taller is not enough, because growth does not necessarily produce another organism. Let us work through an example. A diagram shows a large plant connected by a thin horizontal stem to a smaller plant, which has its own roots.

3:25First, identify the connecting structure as a runner. Next, notice that the smaller plant develops from the existing parent rather than from a seed. Therefore, this is asexual reproduction, and the smaller plant is genetically identical to the parent. Now consider what this means for a population in the wild. A population is a group of organisms of the same species living in the same area. Asexual reproduction can be an advantage because only one parent is needed.

3:49An isolated organism can reproduce without finding a mate, allowing it to establish a population when conditions are suitable. Asexual reproduction can also happen quickly, allowing population numbers to increase rapidly. When food, space and other resources are available, producing many offspring helps a species occupy the habitat. Successful genetic characteristics are passed on unchanged. If the parent is well suited to the existing conditions, its offspring inherit the same genetic characteristics that helped it survive.

4:18But rapid reproduction can create problems. Offspring may remain close to the parent, leading to overcrowding and competition for resources. In plants, this can mean competition for light, water, mineral ions and space. Producing many offspring is therefore not automatically beneficial, because the habitat must provide enough resources for those offspring to survive and grow. The major genetic disadvantage is a lack of genetic variation among the offspring. If they share the same susceptibility to a disease, that disease could kill the whole population.

4:48A change in the environment could also make the shared characteristics unsuitable. The problem is not that clones must be weak, but that they share similar genetic strengths and weaknesses.

Asexual reproduction in crops

4:57Now let us separate those wild population effects from crop production. A grower may choose a parent plant because it produces desirable fruit or grows well under local conditions. Asexual reproduction preserves that parent’s genetic characteristics in the offspring. This helps the grower produce a crop with consistent inherited characteristics, rather than risking a different genetic combination in each new plant. Growers can also produce many plants relatively quickly without needing the fusion of sex cells or seed formation.

5:26For example, strawberry runners can provide new plants from a selected parent. This is useful when the aim is to multiply an existing successful crop. However, copying a plant preserves its undesirable genetic characteristics as well as its desirable ones. The lack of genetic variation is also a serious disadvantage for crops. If all the plants are susceptible to the same disease, an outbreak could damage or destroy the whole crop.

5:49Similarly, an environmental change could affect all the plants in a similar way. Infected planting material can also carry some diseases into the new plants, so choosing healthy parent material matters. There are two misconceptions worth clearing up. Genetically identical does not mean organisms must look completely identical, because different growing conditions can affect their appearance. A clone grown with less water may be smaller than one grown with plenty of water.

6:14Also, a species that reproduces asexually may reproduce in another way too, so identify the process shown rather than making assumptions about the species. Let us connect this to an exam-style question. A grower uses runners from one strawberry plant to produce a field of new plants. The question asks you to describe asexual reproduction and discuss one advantage and one disadvantage to crop production. Start with the definition, then link each advantage or disadvantage to its consequence for the grower.

6:43Asexual reproduction is a process resulting in the production of genetically identical offspring from one parent. An advantage is that desirable genetic characteristics of the parent are retained in the offspring. A disadvantage is that the offspring lack genetic variation, so a disease to which they are all susceptible could destroy the whole crop. Each sentence makes a clear biological point, rather than just calling the method good or bad.

7:05Let us recap the central idea. Asexual reproduction produces genetically identical offspring from one parent, as seen in bacterial binary fission, yeast budding and several forms of plant reproduction. For wild populations, it can allow rapid reproduction without a mate, but can cause competition and shared vulnerability. For crop production, it preserves desirable genetic characteristics and allows rapid multiplication, but a lack of genetic variation creates risk. Making copies works well when the copied characteristics remain useful.