Reproduction – Class 10 Science Notes, Study notes of Biology

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CLASS 10 NOTESCLASS 10 NOTES

PRASHANT KIRAD

SCIENCE

Reproduction

REPRODUCTION The term for creating new life from existing life is Reproduction. Its significance lies in:

- Replacing deceased organisms. - Ensuring the continuity of life on Earth. There are mainly two forms of reproduction: asexual and sexual.

DNA (Deoxyribonucleic Acid):

The resemblance among individuals in reproduction arises from the shared DNA with their parents, resulting in a similarity between the offspring and their progenitors. Significance of DNA Replication: → Preserves body structure. → Facilitates the inheritance of traits. → Introduces diversity during the DNA replication process. Significance of variation: → Essential for evolutionary processes. → Enables adaptation to changing environments. → Contributes to the resilience and survival of populations. Asexual Reproduction: Offspring produced by a single parent, with or without the involvement of gamete formation, represent a reproductive process wherein a lone parent gives rise to progeny. This mode of reproduction may or may not include the formation of specialized reproductive cells called gametes.

Budding:

In the process of budding, small outgrowths called "buds" emerge from the body of the parent organism. These buds eventually detach and give rise to new organisms. Examples include Hydra and yeast.

# Hydra:

● Hydra, a simple multicellular organism, reproduces asexually through budding utilizing regenerative cells. ● Initiation involves a small bud forming on one side through simple mitotic division. ● The bud matures, developing a mouth and tentacles. ● Ultimately, the new Hydra detaches from the parent's body to live independently as a singular organism.

Vegetative Propagation:

Vegetative propagation involves obtaining new plants from portions of an old plant without the involvement of reproductive structures. Typically, this process centers on the growth and development of a single bud on an existing plant part to give rise to a new plant. Examples include potato buds, onion bulbs, leaf buds of Bougainvillea, and Dahlia roots. This method is a form of natural propagation.

# Artificial propagation involves growing multiple plants from a single plant using man-made methods.

- Common methods include: 1. Cutting: Removal of a small plant part using a sharp knife, e.g., sugarcane, bananas, cactus.

2. Layering: Bending a part, typically a branch, toward the ground, allowing the tip to remain exposed while the rest is covered by soil, e.g., Jasmine, or lemon. 3. Grafting: Joining the stems of two plants (one with roots and the other without) to grow as a single plant, e.g., apple, or pear. - These techniques are employed for efficient and controlled plant reproduction. Advantages of Artificial Plant Propagation: ● Ensures that new plants inherit precisely the desired characteristics of the parent. ● Requires less attention for the growth of plants propagated through this process. ● Allows the generation of multiple plants from the same parent, increasing efficiency and productivity.

Tissue Culture:

Tissue culture generates new plants from a small piece of plant tissue or cells taken from a growing plant. This tissue is then cultivated under suitable conditions. Advantages: ● Rapid plant growth characterizes tissue culture, making it a quick technique. ● Plants produced through tissue culture are free from diseases. ● It results in many plants in a short period, typically weeks, and requires minimal space for growth.

Regeneration:

Regeneration is the reconstruction of a complete organism from a specific body part. Challenges in Complex Multicellular Organisms: ● Regeneration is viable in organisms with simpler body structures than cellular organization.

Sexual Reproduction:

Sexual reproduction involves the union of two specialized reproductive cells known as "sex cells," alternatively referred to as "gametes" or "germ cells." There are two types: male gametes (sperm) and female gametes (egg). The fusion of a male gamete with a female gamete results in the formation of a "zygote" cell, which subsequently develops into a new organism.

The union of a male gamete and a female gamete leads to the formation of a "zygote" cell, which subsequently develops into a new organism.

Sexual Reproduction in flowering plant:

Angiosperms, or flowering plants, are characterized by sex organs in their flowers, with seeds enclosed within fruits. These plants exhibit a variety of reproductive structures. Bisexual flowers contain both male and female reproductive organs within the same flower. In contrast, unisexual flowers have either male or female reproductive parts within a single flower.

● Stamen: The stamen is the male part of the flower responsible for reproduction. A single flower can have several stamens. ● Anther: The anther is a two-lobed structure located at the tip of the stamen. It contains two pollen sacs, producing yellowish pollen grains.

● Carpel: The carpel is the female reproductive part located at the center of the flower. It consists mainly of three parts: ➔ ➔ Stigma: The stigma is the terminal part of the carpel and may be sticky. It plays a role in receiving pollen grains during pollination. ➔ Style: The style is the elongated middle part of the carpel. It aids in connecting the stigma to the ovary. ➔ Ovary: The ovary is the swollen bottom part of the carpel. It contains ovules that house the egg cell, the female gamete. ● ● Pollination: Pollination is the transfer of pollen grains from the anther of the stamen to the stigma of a flower.

➔ Self-pollination: In self-pollination, pollen from the stamen of a flower is transferred to the stigma of the same flower. ➔ Cross-pollination: Cross-pollination involves the transfer of pollen from the stamen of one flower to the stigma of a different flower.

Fertilization:

● Following pollination, fertilization occurs in plants, involving the fusion of male germ cells with female gametes, forming a zygote. ● Upon landing on a suitable stigma, pollen reaches the female germ cells in the ovary through a pollen tube, growing from the pollen grains, traveling through the style, and reaching the ovary. ● After fertilization, the zygote undergoes multiple divisions, forming an embryo within the ovule. The ovule develops a sturdy coat and transforms into a seed.

➔ Sperm are small entities comprising a lengthy tail, facilitating their movement toward the female germ cell.

Vas Deferens: The vas deferens transports the formed sperm, which combines with a tube originating from the urinary bladder.

Urethra: The urethra is a duct that conveys urine from the bladder and serves as a passage for semen in males.

Prostate Gland and seminal Vesicle: Secretes fluid to make transport easier for the sperm. This fluid also provides nutrition.

Scrotum: The scrotum is a small pouch housing the testes, located outside the abdominal cavity. Because sperm formation occurs here, a lower temperature than the body's norm is necessary for this process.

Penis: The penis is the external male reproductive organ that transfers sperm into the female vagina during copulation.

Female Reproductive System:

Ovaries: Paired, oval-shaped organs are located in the abdominal cavity near the kidney. It produces thousands of Ora or egg cells. and secrete female sex hormones like estrogen and progesterone.

Oviduct ( fallopian tube): The oviduct, also known as the fallopian tube, transports eggs from the ovary to the uterus. It serves as the site for fertilization and features a funnel-shaped opening near the ovary, with additional openings connecting to the uterus on both sides. Uterus (womb): A Hollow, pear-shaped bag-like structure where the growth and development of the fetus take place. Vagina: It relieves stems from the male partner, and serves as a birth canal. Cervix: lower and the narrower portion of the uterus which opens into the vagina

Fertilization or Sexual Reproduction in Animals:

1. Sperm and Ovum Production: ● Male parent produces sperm. ● Female parent produces ovum.

1. Fertilization Process: ● During copulation, sperm enters the ovum. ● Fertilization occurs, resulting in the formation of the first cell, known as a zygote.
2. Embryo Formation: ● The zygote undergoes various divisions to form an embryo.
3. Implantation: ● The embryo embeds itself into the soft and thick lining of the uterus. ● This process is known as implantation.
4. Placenta Development: ● During pregnancy, the placenta grows into a disc between the uterine wall and the embryo.

Chemical Methods:

● Oral pills alter the hormonal balance, inhibiting the release of

eggs and preventing fertilization.

● However, they may cause side effects.

Intrauterine Devices:

● Loops or Copper T devices placed in the uterus help prevent

pregnancy.

● They may cause side effects due to irritation.

Surgical Methods:

● Blocking the vas deferens in males prevents sperm transfer

while blocking the fallopian tube in females prevents egg

movement.

● Surgical methods are more permanent and involve creating

blocks.

Sexually Transmitted Diseases (STDs):

● Diseases transmitted through sexual contact are known as

sexually transmitted diseases (STDs).

● Examples include AIDS (Acquired Immuno Deficiency

Syndrome) and genital warts, often caused by infections like

gonorrhea.

Importance of Safe Practices:

● Raising awareness about safe practices and preventive

measures is crucial for safeguarding sexual health.

# Top Seven Question:

1) What is the main difference between sperm and eggs of humans?

Solution: Sperms are motile, and produced in large numbers by males. Eggs are non-motile, produced one at a time by females. Sperms travel to the egg for fertilization, forming a zygote. The zygote develops into a fetus and eventually a baby, protected inside the female's body.

2) List any two differences between pollination and fertilization.

Solution:

3) Define reproduction. How does it help in providing stability to the

population of species? [CBSE 2015 C] Solution: a. Reproduction is the vital process ensuring the continuity of a species by generating individuals of its own kind. b. The sustained stability of a population necessitates the replacement of members lost to factors like old age, disease, and accidents, ensuring a balanced and functioning community. c. Through reproduction, genetic variation is introduced, facilitating better adaptation and the evolutionary progression of species, ultimately leading to the emergence of new ones. d. While individual survival may not hinge on reproduction, it is indispensable for the survival and perpetuation of a species.

4) What is vegetative propagation? List two advantages and two

disadvantages of vegetative propagation. Solution: Vegetative propagation is a method of generating new plants from vegetative parts such as roots, stems, and leaves.

Advantages: a. Plants produced through vegetative propagation exhibit earlier flowering and fruiting compared to sexually propagated ones. b. In cases where plants have lost the ability to produce seeds, vegetative propagation becomes essential for their reproduction.

7) What is placenta? Explain its function in human females.

Solution: Placenta is a specialized tissue embedded in the uterine wall. It contains villi on the embryo’s side and blood spaces on the mother’s side. Function: a. Helps in passing of nutrients from mother to fetus. b. Exchange of oxygen and carbon dioxide gases. c. Passing of waste materials from the embryo to the mother.

# Competency-Based Question:

1) The reproductive parts of angiosperms are located in the flower. You

have already studied the different parts of a flower – sepals, petals,

stamens, and pistils. The stamens and pistil are the reproductive parts of

a flower which contain the germ cells. The flower may be unisexual

(papaya, watermelon) when it contains either stamens or pistil or bisexual

(Hibiscus, mustard) when it contains both stamens and pistil.

1. Where are the reproductive parts of angiosperms located?

2. What are the two main reproductive parts of a flower mentioned in

the passage?

3. How does the flower's sexuality differ between unisexual and

bisexual flowers?

4. Name two examples of unisexual flowers provided in the passage.

Solution:

1. The reproductive parts of angiosperms are located in the flower.

2. The two main reproductive parts of a flower are the stamens and

pistil.

3. A flower is considered unisexual when it contains either stamens or

pistils. In contrast, it is termed bisexual when it contains both stamens

and pistils.

4. Examples of unisexual flowers mentioned in the passage are papaya

and watermelon.

1. In an experiment, a scientist removed some cells from the growing point of a plant and placed it a suitable medium containing nutrients and plant hormones leading to the formation of shapeless lump or mass called X. X is then transferred to another medium which lead to development of roots. X with developed roots is then transferred into another medium that induced the development of shoots. X in this way differentiated into tiny plantlets which were transplanted into pots where they grew into mature plants.

(a) It helps in production of disease free plants.

(i) What is X in the given paragraph? (a) Plantlet (b) Callus (c) Embryoid (d) Tissue

(ii) Which technique has the scientist used for the propagation of plant? (a) Layering (b) Grafting (c) Tissue culture (d) Cutting

(iii) What is the advantage of the technique mentioned in the paragraph?

(b) It is a very fast technique as thousand of plantlets can be produced in a few weeks time.

(d) Tissue culture is artificial method of vegetative propagation.

(c) It is also known as micropropagation due to extremely small amount of plant material used for propagation. (d) All of these

(iv) Select the incorrect statement regarding the propagation technique mentioned in the paragraph. (a) It is used in the production of ornamental plants like orchids, carnation, Chrysanthemum, etc. (b) It is a modern method of artificial propagation of plants. (c) Plants produced by this methods are genetically different from the parent plant. (d) Very little space is needed for developing new plants by this technique.

(v) Which of the following statements is incorrect? (a) Virus free plants cannot be produced by tissue culture technique. b) Tissue culture technique is useful in obtaining homozygous diploid. (c) Tissue culture is useful in quick propagation of Gladiolus.

2) Chromosomes in the nucleus of a cell contain information for the

inheritance of features from parents to the next generation in the form of DNA (Deoxyribose Nucleic Acid) molecules. The DNA in the cell nucleus is the information source for making proteins. If the information is changed, different proteins will be made. Different proteins will eventually lead to altered body designs. Therefore, a basic event in reproduction is the creation of a DNA copy. Cells use chemical reactions to build copies of their DNA.

1. Where is the information for the inheritance of features stored in a cell?
2. In what form is the information for inheritance encoded in the chromosomes?
3. What is the role of DNA in the cell nucleus, according to the passage?
4. How does the alteration of information in DNA impact the body's design and features?

Solution:

1. The information for the inheritance of features is stored in the chromosomes within the nucleus of a cell.
2. The information for inheritance is encoded in the form of DNA (Deoxyribo Nucleic Acid) molecules.
3. DNA in the cell nucleus serves as the information source for the synthesis of proteins.
4. Changing the information in DNA leads to the production of different proteins, ultimately resulting in altered body designs and features.

does not need a pollinating agent whereas pollinating agent is required in case of Q.

(i) Select the option that correctly identifies plant P and Q. (a) P Papaya, Q - Marigold (b) P-Pea, Q - Cucurbit (c) P-Sunflower, Q - Orchids (d) P-Tulip, Q - Daffodil

(ii) Select the correct option regarding plants P and Q. (a) Seed setting is assured in plant P even if all its flowers are emasculated. (b) Male flowers of plant Q always open only after the female flowers of the plant are pollinated. (c) Female flowers of plant Q can reproduce by cross pollens or self pollens depending upon the genus to which plant Q belongs to. (d) P is a cross pollinated plant whereas Q is a self pollinated plant.

(iii) How can self pollination be avoided in plant P? (a) By removing all the flowers of plant P (b) By removing all the anthers of all the flowers (c) By removing all the carpels of all the flowers (d) None of these

(iv) Which of the following holds true for plant Q? (a) Plant Q bears complete flowers. (b) Plant Q bears either male flowers or female flowers but never both. (c) Sexual reproduction in plant Q may or may not give rise to genetic variations.

1. P and Q are two monoecious plants. P bears bisexual flowers whereas Q bears unisexual flowers. P

(d) All of these