How Do Organisms Reproduce Class 10 Notes CBSE Science Chapter 8

How Do Organisms Reproduce Class 10 Notes

The course and curriculum of Class 10 need consistent practice and revision to perform better in exams. Amongst several chapters, one of the important chapters in Class 10 Science is Chapter 8 – How do Organisms Reproduce which covers several sub-topics. To simplify the entire learning process, Extramarks has provided revision notes on its official website. Students can visit the website and access CBSE Class 10 Science Revision Notes Chapter 8 – ‘How do Organisms Reproduce’ in detail. 

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Access CBSE Class 10 Science Chapter 8 How Do Organisms Reproduce Notes

Class 10 Science Ch 8 Notes

The Class 10 Science Chapter 8 Notes deals with the study of the reproductive system. The topics discussed here talk about the reproductive system of living organisms and their types. In addition, students learn what distinguishes between the sexual and asexual systems of reproduction. 

The Class 10 Chapter 8 Science Notes provide information about the male and female reproductive systems. Extramarks recommends that students should read the NCERT books properly to score good marks in the board examinations. The website provides detailed CBSE revision notes for candidates of Class 10. In addition, the website provides CBSE sample papers, CBSE previous year question papers, CBSE extra questions etc., for students preparing for the board examinations. 

Introduction 

It goes without saying that because organisms reproduce, they are noticed. It is unlikely that we would have known about the existence of a given species if there was only one non-reproducing member. They come to our attention because there are numerous organisms that belong to a certain species. 

How can we know that two unique organisms from the same species are related? We typically say this because of how similar they appear to be. As a result, organisms that reproduce, produce offspring that closely resemble the original.

Do organisms create exact copies of themselves? 

• The nucleus of a cell consists of chromosomes that carry information from parents to offspring.
• The DNA present in the nucleus is the source of information required for making proteins.
• Copying the DNA is the basic event involved in reproduction.
• Once the copying of DNA is done successfully, there is formation of daughter cells. Each cell has its own nucleus and DNA.
• There can be variations in the process of DNA copying.

Importance of variation: 

• Under certain specific conditions, variations in the DNA are required to make the organism survive. Hence, the drastic change in the genetic material of an organism to adapt according to environmental conditions is known as variation. 
• The major importance of variation lies in the survival of a particular species over a time period. 

Modes of reproduction 

The procedure involving the production of offspring by an individual or individuals to propagate their species is known as reproduction. The various modes of reproduction are as follows: 

Asexual mode of reproduction 

This is the process in which a single individual produces offspring. Generally, unicellular organisms are involved in the asexual mode of reproduction. 

Sexual mode of reproduction

When two individuals interact with each other for the creation of a new generation of species, it is known as the sexual mode of reproduction. 

Types of the asexual mode of reproduction

Fission: 

When the nucleus of a cell divides into two individual parts under favourable conditions, it is known as fission. It can be of two types: 

• Binary fission: It leads to the formation of two new individuals and can be divided into irregular type, transverse type, and longitudinal type of binary fission. 
• Multiple fission: The division of a single cell into many daughter cells is known as multiple fission. Example: plasmodium

Fragmentation: 

When the organism breaks into several small pieces on maturation is known as fragmentation. For example: Spirogyra

Regeneration: 

When a fully grown organism can break down into several pieces where each of them has the ability to grow into new individuals is known as regeneration. Example: Hydra 

Budding: 

The process in which a perturbed-like outgrowth appears on the body of an organism. It is known as budding. Example: Hydra 

Vegetative propagation: 

The various types of vegetative propagation are as follows: 

• Stem cutting: In stem cutting, the stem is cut into various pieces containing the inner nodes and axillary buds. The stems are then planted into the soil for propagation. 
• Layering: This is the process in which the young stem of a plant is first bent and then buried into the soil. 
• Grafting: In grafting, the stems of two different plants are cut and joined together to grow new plants. 

Sexual reproduction: 

The process in which new living organisms are produced by combining genetic information from two individuals of different types (sexes). Sexual reproduction involves the combination of two different DNA from two different sexes to form a unique organism.

Sexual reproduction in flowering plants: 

• In plants, the fusion of gametes to produce offspring is known as sexual reproduction. The reproductive parts are located in the angiosperms. 
• The stamen contains the male parts and the pistil contains the female reproductive parts. 
• Based on the presence of stamen and pistil, the flowers can be classified into sexual and bisexual types. 

Pollination: 

The process in which the transfer of pollen grains from another stamen to the stigma of the pistil is known as pollination. It can be of two types: self-pollination and cross-pollination. 

Fertilisation: 

• Once the pollen grains are deposited, the next step is that they should reach the female germ cells. 
• A tube grows out of the pollen grains and reaches the ovule. 
• In the ovule, the male germ cells are present that fuse with female cells to form a zygote. This process is known as fertilisation. 
• The zygote forms divide repeatedly to form an embryo. It will then develop into seeds, whereas the ovary develops into a fruit. 

Germination: 

The seed contains an embryo that can develop into a seedling under suitable conditions. This process is known as germination. 

Reproduction in human beings: 

Human beings reproduce by sexual mode of reproduction. It is divided into male and female reproductive systems. Let us discuss them in detail. 

Male reproductive system: 

• The male gamete is a sperm that contains genetic material and has a long tail. The motility of the long tail helps the sperm reach the female germ cell. 
• Various organs are associated with the male respiratory system:
  • Testes: Testes are the part of the system responsible for the production of male germ cells or sperms. They also produce testosterone. 
  • Vas deferens: The tube that transports the sperm to the urethra is known as vas deferens. 
  • Prostate glands and seminal vesicle: These glands are located along the area of the vas deferens. They secrete semen that nourishes the sperm. 

Female reproductive system: 

• The system produces the female gamete and provides the site for fertilisation. 
• The development of embryos takes place in the female body. 
• It produces hormones such as estrogen and progesterone. 
• Various organs associated with the system are: 
  • Ovaries: They are the pair of glands located on either side of the uterus and protect the female gametes. In addition, they make the cells ready for fertilisation. 
  • Fallopian tubes: These connect ovaries to the uterus. When the eggs are released, they are transported through the fallopian tubes. 
  • Uterus: It is a structure where the eggs are fertilised, implanted, and developed into a fetus. It is made up of inner, middle, and outer layers known as endometrium, myometrium, and perimetrium. 
  • Cervix: The site where the uterus opens into the vagina is known as the cervix. It is a passage through which sperms enter the uterus.

Fertilisation and development: 

• It starts when the sperm enters the female body after sexual intercourse. From the vagina, they move upwards. 
• The eggs in the fallopian tube area are fertilised by the sperm. 
• The zygote formed gets divided repeatedly and travels down the fallopian tube into the uterus. 
• The embryo now gets implanted into the uterus and continues to grow into a fetus. 
• In nine months the complete development of the fetus occurs in the body of the mother. 
• A child is born due to rhythmic contractions of the muscles. 

What happens when eggs are not fertilised? 

If eggs are not fertilised, the lining of the uterus is shed, resulting in the passing of blood and mucus through the vagina. This process is known as menstruation and the cycle occurs every month and lasts for 2-8 days.

Reproductive health: 

• Engaging in safe sex practices can prevent conditions such as STDs, and infections such as gonorrhoea and syphilis. Some viral infections such as warts and HIV can also happen if condoms are not used.
• Not using barriers or contraceptives may lead to pregnancy. Thus, it is essential to either use condoms or contraceptive devices such as Copper T which are implanted in the uterus to have safe sex.
• Various surgical procedures such as vasectomy in males and tubal ligation in women can also be undertaken, although they can lead to many complications.