CBSE Class 10 Science is considered to be a high-scoring subject. However, in order to perform well in the Class 10 CBSE Science, your concepts must be adequately clear. This is where the phase of revision, in the lead-up to the final Board exams, can play a crucial role.
During the revision phase, make sure that you choose the topics on the basis of the weightage of marks that they carry. It helps to break up the revision into phases, based on the topics included in Class 10 CBSE Science syllabus. Superprof is here to assist you with just that. In this article, we discuss Class 10 Biology: Reproduction.
What is Reproduction?
Definition: Reproduction is the biological process of producing a new individual or an offspring identical to the parents.
The process of reproduction is vital to ensure an increase in the number of individuals of a species under favourable conditions. It is a fundamental characteristic of all livings things and is an essential life process.
Types of Reproduction
There are 2 types of reproduction – asexual and sexual.
Asexual reproduction involves only 1 parent. The new offspring produced is genetically similar to the parent. Asexual reproduction can be further divided into the following categories:
This type of asexual reproduction is seen in bacteria, protozoa like amoeba and paramecium. In this process, first, the pseudopodia, withdrawn (karyokinesis) from the nucleus of the parent cell, divides and, then, the cytoplasm divides (cytokinesis), which results in the formation of 2 daughter cells.
This type of asexual reproduction is seen in plasmodium, (a malarial parasite). In this process, under unfavourable conditions, the parent cell develops a thick resistant wall around itself forming a cyst. Within the wall, the cytoplasm divides many times to form many plasmodia. When conditions turn favourable, the cyst wall breaks, and the plasmodia are released.
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This type of asexual reproduction is seen in yeast (a fungus). In this process, the parent yeast cell develops a protrusion or an outgrowth at its upper end. The nucleus of the parent cell divides and one of them moves into the outgrowth which grows bigger and, finally, separates from the parent cell to lead an independent existence. Very often, if the conditions are highly favourable, a chain of buds is formed.
This type of asexual reproduction is seen in multicellular organisms with relatively simple body organization, such as spirogyra. A spirogyra has a filamentous body. Each fragment has the capacity to form a new individual. However, all multicellular organisms cannot show cell-by-cell division as cells from tissues that, in turn, form organs. These organs are placed at definite positions in the body. Hence, they need to use more complex methods of reproduction.
An organism's ability to develop its lost parts is called regeneration. Some organisms show a high regenerative capacity. Regeneration is also a means of reproduction, such as in planaria. Regeneration is carried out by specialized cells that redivide to form a mass of cells from which different cells undergo changes to become different cell types and tissues. These changes occur in an organized sequence known as development.
This type of asexual reproduction is seen in rhizopus (a fungus). The body of a rhizopus is made up of thread-like structures called hyphae. The erect hyphae bear sporangia inside which reproductive structures called spores are formed.
Spores are asexually reproducing bodies having a thick protective wall. They are produced under unfavourable conditions and help to tide over these unfavourable conditions. When the spores fall on a suitable medium, each one forms a new individual.
The method by which plants reproduce by their vegetative parts such as roots, stems, and leaves, is collectively known as vegetative propagation. Vegetative propagation is of 2 types.
- Natural vegetative propagation
- Artificial vegetative propagation or tissue culture
Examples: Mint reproduces naturally by roots; sugarcane, jasmine by stems; bryophyllum by leaves. In bryophyllum, buds are produced in the notches along the leaf margins and when they fall on the soil, they develop into new plants.
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This is a complex process of reproduction that involves the formation and transfer of gametes, followed by fertilization, the formation of the zygote, and embryogenesis. Sexual reproduction in plants involves 2 processes:
The process of transfer of pollen grains from an anther to the stigma of the flower is known as pollination. The 2 types of pollination are:
- Self-pollination: The transfer of pollen grains from the anther to the stigma of the same flower or another flower of the same plant.
- Cross-pollination: The transfer of pollen grains from the anther to the stigma of another flower or another flower of a different plant of the same species. It generally takes place with the help of some agents like insects, birds, wind, and water.
The process by which the fusion of male and female gametes takes place to form a zygote during sexual reproduction is known as fertilization. Pollination is followed by fertilization in plants.
The sexual mode of reproduction takes place in all multicellular organisms including humans, animals, and higher plants. The asexual mode reproduction occurs only in lower invertebrates and other simpler living organisms such as amoeba, bacteria, and hydra.
The sexual mode of reproduction is a fundamental human characteristic. In this process, 2 parents are involved in producing a new individual. Offsprings are produced by the fusion of gametes (sex cells) from each parent. Hence, the newly-formed individual is different than the parents, both genetically and physically.
Human reproduction is an example of sexual reproduction.
In human beings, males and females have different reproductive systems. Hence, they are known to exhibit sexual dimorphism. Males have testes, also called testicles, while females have a pair of ovaries.
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The Human Reproductive System
The male reproductive system is different from the female reproductive system, both in its structure and function.
Male Reproductive System
The male gametes or sperms are produced within the male reproductive system. Sperms are small unicellular structures with a head, middle piece, and tail. The constituent elements of the male reproductive system are:
- Testicles (testes): They are a pair of oval-shaped organs masked in a pouch called the scrotum. They are responsible for the production of sperms and the male hormone testosterone.
- Scrotum: It is a sac-like organ that hangs below the penis and behind it. It houses the testicles, or testes, and maintains a temperature that is required for the production of sperm.
- Vas deferens: The sperms produced in testes are stored in a tube called the epididymis. Here, the sperms mature and pass to the urethra through the muscular tube called vas deferens.
- Accessory glands: These are 3 glands, namely seminal vesicles, prostate gland, and Cowper’s gland. The secretions from the 3 glands mix to form a fluid called semen. Semen nourishes the sperm, increases its volume, and helps in lubrication.
- Penis: The penis is a cylindrical tube that serves both as a reproductive organ and an excretory organ. It delivers sperms into the vagina during sexual intercourse.
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Female Reproductive System
The female reproductive system is active before, during, and after fertilization. It consists of:
- Ovaries: A pair of ovaries produces and stores ovum in them. They also produce the female hormone called estrogen.
- Fallopian tubes (Oviducts): They are the site of fertilization, connecting the ovaries with the uterus.
- Uterus: It is the site of the development of the embryo.
- Vagina: It is the part that connects the cervix to the external body parts of the female. It is the route for the penis during sexual intercourse as well as a fetus during delivery.
The female reproductive system has 2 primary functions, viz.:
- Production of the female gamete called ovum/egg.
- Providing nutrition and protecting the developing embryo.
During puberty, eggs in the ovaries start to mature. One of the ovaries releases the matured ovum every 28 to 30 days, a period referred to as ovulation.
Reproduction Process in Human Beings
The process by which the male sperm fuses with the female egg (ovum) to produce a zygote is called fertilization. Fertilization is a crucial stage of reproduction in human beings. The fertilized egg is called the zygote. The zygote starts to divide into many cells and develops into an embryo.
The embryo moves into the uterus and gets attached to its walls. This process is referred to as implantation, and the implanted embryo eventually develops into a fetus.
In case the zygote is not formed, the inner wall of the uterus breaks, causing bleeding through the vagina. This process is called menstruation and it occurs at a regular interval of 28 days.
The embryo is nourished by the mother’s blood with the help of a special tissue called the placenta. The placenta provides a large surface area for glucose and oxygen to pass from the mother to the embryo. Similarly, waste from the developing embryo is removed through the placenta.
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The child is born as a result of the rhythmic contractions of the muscles in the uterus after 9 months (36 weeks) of development inside the mother’s womb. This period of development is called the gestation period.
The sexual cycle in a woman continues up to the age of 45 to 50 years, after which the ovaries stop releasing eggs. This stage is called menopause and it marks the end of menstruation in women.