Reproduction in Animals and Plants class-8th Notes

Reproduction

➨Reproduction is the process by which living beings produce young ones of their own kind.

➥ It helps in maintaining the species.

➥ It helps in the continuity of life.

➥ It helps in maintaining of population size.

1. Asexual Reproduction:
   ➥The production of a new organism from a single parent without the involvement of sex cells (or gametes) is called asexual reproduction
2. Sexual Reproduction:
   ➥The production of a new organism from two parents by making use of their Sex cells (or gametes) is called Sexual reproduction.

Ques. - Differentiate between Asexual Reproduction and Sexual Reproduction.

Asexual Reproduction

Types of Asexual Reproduction:

1. Binary Fission: A single organism divides into two equal parts, each developing into a new organism.

2. Fragmentation: The body of the parent breaks into fragments, each of which grows into a new organism.

3. Regeneration: The process of getting back a full organism from its body parts is called Regeneration.eg - Hydra and Planaria.

4. Budding: A new organism grows from a small bud on the parent and eventually detaches to live independently.

5. Spore Formation: Spores are produced by the parent, which can grow into a new organism under favorable conditions.

6. Vegetative Propagation: New plants grow from the vegetative parts of the parent plant, such as roots, stems, or leaves.

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Sexual Reproduction

⟹ Sexual Reproduction involves the fusion of gametes or sex cells resulting in the formation of zygote.

⟹ Due to the fusion of gametes, the chances of variations are very high during sexual reproduction.

Sexual reproduction in Flowering Palnts

➥The Sex Organs (or reproductive organs) of a plant are in its flowers.

(1). Stamen: It is the male reproductive part of the flower. It is composed of two parts:

• Anther: Produces pollen grains that are yellow in color.
• Filament: Supports the anther.

(2). Pistil: It is the female reproductive part of the flower. It is composed of three parts:

• Ovary: The swollen bottom part.
• Style: The middle elongated part.
• Stigma: The terminal sticky part.

(3). Sepals: The green, leaf-like parts of the flower. Their function is to protect the flower in its initial stages.

(4). Petals: The colorful parts of a flower. Their function is to attract insects for pollination and protect the reproductive organs.

➯ Types of Flower:

Unisexual Flowers: Contains either stamens or pistils.

• eg: Papaya, Watermelon.

Bisexual Flowers: Contains both stamens and pistils.

• eg: Hibiscus, Mustard.

Sexual reproduction in Flowering Palnts

➥The age at which sex hormones and gametes begin to be produced, and when boys and girls become sexually mature, is called Puberty.

In males: After puberty, the testes start producing sperms and the male sex hormone called testosterone.

In females: After puberty, the ovaries start producing ova (or eggs) and the female sex hormone, estrogen.

➯Both males and females also start developing secondary sexual characteristics.

Secondary Sexual Characteristics in Males:

• Hair grows in armpits, pubic regions, chest, and face.
• The body becomes more muscular.
• The voice deepens.
• The chest and shoulders broaden.

Secondary Sexual Characteristics in Females:

• Hair grows in armpits and pubic regions.
• Mammary glands develop and enlarge.
• Hips broaden.
• The fallopian tubes, uterus, and vagina enlarge.

Male Reproductive System

➥The male reproductive system consists of parts that perform two major functions:

• Produce sperms: Testes
• Deliver sperms to the site of fertilization: All the rest (Vas deferens, Seminal Vesicle, Prostate)

(1). Testes

➥ The testes are the primary reproductive organs in males.

➥ They are located outside the abdominal cavity in the scrotum because sperm formation requires a lower temperature than normal body temperature.

Functions of Testes:

• Formation of sperms.
• Secretion of testosterone.

(2). Vas Deferens

➥ The vas deferens delivers sperms from the testes to the urethra.

(3). Prostate and Seminal Vesicle

➥ The seminal vesicle and prostate gland add fluid secretions to the sperms, making their transport easier and providing nutrition.

(4). Urethra

➥ The urethra forms a common passage for both sperms and urine.

Female Reproductive System

1. Ovaries:

➥ The ovaries are the primary reproductive organs in females. They perform two major functions:

• Production of eggs (ova).
• Secretion of estrogen and progesterone.

➥One egg is produced every month by the ovaries.

2. Fallopian Tubes (Oviducts):

➥It is the primary reproductive organ in female.

➥It acts as the site of fertilization.

3. Uterus:

➥The oviducts unite into an elastic, bag-like structure known as the uterus.

➥ The uterus opens into the vagina through the cervix.

4. Vagina:

➥ The vagina receives sperms from the male partner and serves as a birth canal.

5. Cervix:

➥ The uterus is connected to the vagina through a narrow opening called the cervix.

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