Introduction In the chapter ‘How do organisms reproduce’ of biology from class 10 we are going to learn how reproduction takes place in plants and animals both sexual and asexual. We are also going to discuss reproductive health in which we will discuss sexually transfer diseases. We will also learn about childbearing and women's health. In this chapter of class 10, we will learn and understand every basic and important detail about the topic of reproduction. This chapter is very helpful for students of class 10 and in exams, this topic will help you to get high grades. So let us start with what is reproduction?
Reproduction is a biological process in which an organism gives birth to a new organism that looks like the organism. The process of reproduction takes place in different living organisms, whether it is a plant or an animal. Every organism reproduces differently in order to maintain its species. This is a very important process that protects the organism from being eliminated from the world. After that, we get information about why reproduction is so vital. The process of reproduction is important because every living being is going to die one day and to maintain the species in the world, reproduction takes place. Among single-celled organisms, such as bacteria and amoebas, we cannot determine whether they are reproducing or dividing. It is a complex process. Every species in the world plays a critical role, and for that to happen, reproduction is essential. Plants play an imperative role in providing oxygen to animals and animals provide carbon dioxide to plants and with this, there are many significant roles for every organism.
For reproducing similar organisms, organisms have to provide information about the species and information about organisms present in their cell’s nucleus. We are eukaryotic organisms and we have a nucleus that is bounded by the membrane. In that nucleus, there are fiber-like structures that are made up of DNA and protein. DNA is the blueprint of our body and has all the information which is required for reproducing an organism. The full form of DNA is Deoxyribo Nucleic Acid. Every cell has our information inside it, like how we look, how we walk and how to make our organs, everything. When we copy these things we can get an organism that looks similar to us. Without DNA or the blueprint of any organism, the process of reproduction can’t take place.
The process of copying DNA is the biochemical mechanism. It has chemistry in it because DNA is made up of carbon, oxygen, nitrogen, and many things that are part of chemistry. It is important to understand that in any organism the biochemical process does not take place with 100% accuracy whether it is bacteria, animal, or plant. When we copy something, a few things change and, as a result, the organism does not look exactly like another. Our bodies and organs are similar but that does not mean that our faces and physique look the same. The changes we see in DNA are called variations and as a result, they can be similar but not identical. It is impossible to get a 100% accurate copy of any organism. The changes we get in our cells can sometimes be so drastic they affect the bodies of other organisms. The process of transferring information from the parent to the offspring is known as inheritance. DNA is necessary for the synthesis of protein, and if something in DNA changes, the protein will change as well. The basic process of reproduction is the replication of DNA. As a result of chemical reactions, cells make DNA and they separate themselves by making two DNAs. For copying DNA you also need a cell to put that DNA in that cell. For that, our body is required to replicate all the things that are present in a cell. You can’t push out DNA after copying it, you need a cell that has a place for DNA. If you do this process effectively then you will get two cells. Some newborn cells will die if they undergo such drastic changes, but if the changes are not drastic, the cells will survive. The process that converts an organism to another organism that changes with time is called evolution.
Organisms present in groups at a place in the ecosystem and they perform a role at that place. If the process of DNA copying is working properly then your body will function properly and your body design will be good. The organism will use those cells to survive in the ecosystem. The process of reproduction is imperative for the stability of the population. It can be a problem if an ecosystem gets altered because of an ecological issue that changes the living process. It is possible for an organism to be rare enough to survive in such a situation. This can help in the stability of that organism and can also prevent it from becoming extinct. If a population lives in a particular ecosystem then the whole population can get wiped out if some drastic change in the ecosystem occurs but we know that organisms are getting variations whenever new cells get created. Therefore, due to variation few organisms from that population are able to survive and maintain the population.
Asexual- As the name implies, it is an asexual process in which no gametes are fused. In this process, there is no increment in the number of chromosomes. It requires a single parent to reproduce
Sexual- In sexual reproduction, you can see that some special cells get created and you can also see gametes formation. These special cells are known as sex cells and germ cells. For this reproduction, two organisms are required.
The mode of reproduction in which a single organism can reproduce a new organism is known as asexual reproduction.
Asexual organisms are known as unicellular organisms. There are two types of fission in single-cellular organisms. In unicellular organisms, the division of cells is the process of reproduction. This organism creates a new organism by diving into two or more. There are different patterns of fission or division. The process of dividing the nucleus is known as karyokinesis and after that, the division of the cell is known as cytokinesis. The process of karyokinesis takes place before cytokinesis. Let us discuss the types of fission.
In binary fission, a single-celled organism separates itself into two pieces. That is why we call it binary because binary means two. In this cells divide into many bacteria and protozoa. Amoeba is an example that tells us about binary fission. In amoeba, we can see that in the first step the nucleus gets split into two and then the cells get divided. The new cell which forms in the division is known as the daughter cell and the cell which produces it is known as the mother cell. In the amoeba division of cells, can take place in any plane which means it can be divided from any side because it does not have any particular shape. But there is an organism known as leishmania that has to divide from a particular plan. It can’t divide itself horizontally or diagonally, because of its whip-like structure it can only divide itself vertically.
Multiple fission means the division of a cell into multiple cells. We can see this with the example of plasmodium. Plasmodium is the causative organism of malaria. It reproduces through multiple fission. It is a single cell that will make multiple cells. In this type of fission, organisms divide the nucleus many times in a single cell and that cell is covered with a cyst wall. After making many nuclei the cyst cell will break and the nucleus will be divided into multiple cells.
Fragmentation is a process where you can see that an organism is dividing into several parts and those parts are also surviving. And those new parts can also give birth to a whole new individual. This process takes place in multi-cellular organisms that have simple body designs. These types of organisms get divided into small pieces upon maturation. Spirogyra is an example of this process. This process does not take place in every organism because they do not have the capability to form a new organism by dividing cells simply. This process is possible in organisms that do not have any kind of tissue. This process takes place in organisms that only have cells in their body. Multicellular organisms need complex ways of reproduction. They have different cell types in their bodies so there will be a different process of reproduction for every organism. There is a question book that, how is reproduction to be achieved from a single cell type if the organism is itself consists of many cells types? In answer to this question, a single cell should be able to divide itself, grow, and cover itself according to the situation.
This is a process where an organism can fully regrow from a small part that somehow gets cut from the organism. We can't say that it is a process of reproduction because any organism does not want to be cut. According to this book of class 10, regeneration is a type of reproduction, but in reality, regeneration is the process of regrowth and division of cells. Any organism doesn’t want to be dependent on something apart from its body parts with pain. Some organisms, such as starfish, hydra, and planaria, use this reproductive method. A few specialized cells in their bodies are able to regenerate lost parts by dividing. This process takes place if any part of an organism gets separated because of some accident. They also have different ways of reproduction which is an advantage for these organisms. Planaria is the most powerful organism that can regenerate from any cell. As a result of this process, a mass of cells makes tissues, and those tissues form organs that help rebuild an organism from the broken parts.
This process of reproduction in which we can see outgrowth. The process of budding takes place in organisms like yeast and hydra. One of the characteristics of yeast is that it is a unicellular organism that can split into many pieces. The newly formed cell in yeast stays attached till it becomes fully developed and mature. A mature organism gets all the essentials for reproduction when it is fully developed. The NCERT book of biology provides information about budding via the hydra. Hydra has specialized cells that help in regenerating. A new outgrowth will form in the hydra when cells divide. This outgrowth will be attached to the parent body and will detach after it is mature.
The vegetative propagation method utilizes a plant's asexual part to produce a new organism and does not use any sexual parts. The sexual part of a plant is the flower. Some plants can reproduce through their stems, like potatoes. There are some plants that reproduce through their leaves, and the part of the plant that helps with reproduction is known as vegetative propagation. This process of reproduction is not possible in animals. There are two methods of vegetative propagation which are layering and grafting. The process of mismatching any plant allows you to grow a new one. We can see this type of vegetation in roses, sugar cane, grapes, etc.
Plants grow through vegetative propagation, which helps in getting fruits and flowers early. Through this method, we can grow bananas, oranges, roses, and jasmine that do not have the capacity to have seeds. This method also keeps the quality of the parent plant in new plants and also adds all the characteristics because it is an Asexual reproduction.
In the process of tissue culture, you give a plant many nutrients so that it can develop. We can grow a whole plant with the help of tissue. It is a process in which you can grow a plant by separating tissues or separating growing cells from the tip of the plant. After that, the newly formed cells should be placed in an artificial medium so they can form a new group of cells or callus. The part should get all the needed materials there. Then we have to shift callus into a different medium in which plant hormones are present that helps in growth. Afterward, you get the plantlets, which you can put into the soil and grow a new plant. By using this we can grow many plants. Through this process, you can save a plant from diseases because the apical meristem of plants always stays disease-free. Now, what is apical meristem? It is the tip and root part of a plant.
Spores are the Asexual units that have the capability of making a new organism. A single spore can create an organism. The spore is covered with a wall, like a cyst and when the condition gets favorable the wall opens and helps in reproduction. It is in this chapter that we find an example of rhizopus. These are the multi-cellular organisms in which specific reproductive parts can be identified. The thread-like structure which we can see on bread is the hyphae of the bread mold (rhizopus). They are not reproductive parts. There is some blob-on-a-stick structure that is present at the top of the hyphae. The blob contains cells that can develop into an individual. A thick wall covers the spores, and when they are found in damp environments, they get open. When it comes in contact with a moist place, it starts to grow. Spores can be found in the air and when they fall on moist surfaces they begin to grow.
In this mode of reproduction, two individuals of different sexes are required to produce a new generation. Let’s talk about what is the importance of sexual reproduction? And what are the advantages of sexual reproduction? We can see that in asexual reproduction, organisms are genetically the same and look the same. Because of the similarities, there are rare chances of variations. In the above paras, we have discussed the advantage of variation. It helps an organism to survive in unfavorable conditions. In sexual reproduction, you can see two different types of DNA and those two organisms also have got two different DNA. So you will get DNA from both families and because of the merging of DNA, you will have more variety. In sexual reproduction, we get more variations than in asexual reproduction. We can see asexual reproduction in simple organisms but in complex organisms, we can see sexual reproduction. As we have studied the creation of new cells requires copying of DNA. Because DNA coping mechanisms cannot be accurate, we can notice variations in the new organisms. Variation is not a thing that can be stopped, but it is necessary for the survival of an organism. This variation helps an organism to be protected from adverse conditions. In sexual reproduction, we can see huge variations and it also helps in carrying the DNA of so many people. Ensure that the variation is not too drastic. With every generation, the variation should be slower. Every generation, the variation in DNA increases and so the further generations will have a bunch of variations. When two individuals from the same generation participate in the process of reproduction then we will see various variations and patterns. It is very significant to ensure that those variations won’t have a negative effect on species, since they will pose problems for the survival of those species. Combining two or more individuals will give you different variations and every variation will be different. The sexual mode of reproduction is the process in which the DNA of two organisms is combined. Let's imagine what will happen if organisms transfer their chromosomes every generation, and they get added to the new organisms. Then there will be a collection of so many chromosomes. So, how can we maintain the count of chromosomes? If chromosomes get added to every new organism what will happen in the world? Do you know that a person should maintain his/her chromosome number? If there are fewer or more chromosomes in your body, then it can make you ill. Every organism needs to maintain its chromosome number if it wants to produce a similar organism. Then a question arises, how can we maintain chromosome numbers? So the answer is, there is a special type of cell division which is called meiosis. This is a process of cell division in which the number of chromosomes is reduced by half. If the chromosome number is 46 then after meiosis it will become 23. In both sexes, it is going to become half, and then it will be essential for reproduction. The new organism will get 46 chromosomes. The special cells that are involved in the reproductive process have half no. Of chromosomes. These cells are known as gametes. When they form in females they are known as female gametes and when they form in males they are known as male gametes. Both gametes must combine to produce new organisms with a sufficient number of chromosomes for survival. NCERT biology class 10th provides information on haploid and diploid numbers. Now let us learn what these terms mean. Haploid numbers refer to having a single set of chromosomes. Which means an organism has a single set of chromosomes that has every information about the organism in a single set. Haploid no. of humans is 23. The diploid number refers to a pair of chromosomes that contain all information about the organism. Whenever an organism obtains a chromosome from the father and a chromosome from the mother, it will be diploid, which will be 23+23=46. There are 46 chromosomes in the human body and the number of chromosomes gets halved when there is reproduction. We can understand the meiosis process by taking the example of humans. The meiotic cell division takes place in the male’s testis and ovary in females. In this organ, a special kind of meiotic process takes place which forms gametes. The male gamete is known as the sperm and the female gamete is known as the ovum. As an example, imagine the parent cell has two sets of chromosomes, and at the time of meiosis 1 the cell gets divided in half. And in meiosis 2 the cells copy themselves. If both gametes look similar, then they are known as Isogametes. It is easy to differentiate gametes in some complex organisms. This is because some have a lot of energy and food storage while others have a small size and less food storage. The big gamete can’t move much and the small gamete can move. It is observed that the non-motile gamete is a female gamete and the tiny one which can move is the male gamete. If we are able to differentiate the gametes they are known as heterogametes. Whenever you see an organism that can produce both gametes, that organism is said to be bisexual. The earth’s warm and hibiscus are examples of bisexual organisms. And if the gametes are forming differently in both sexes then those organisms are known as unisexual organisms.