Class 10th How Do Organisms Reproduce Notes: Science Ch. 7

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Class 10th How Do Organisms Reproduce Notes: All living beings have the ability to multiply or reproduce, giving rise to offspring of a similar nature. Reproduction is a fundamental process crucial for the survival of a species and the perpetuation of life.

In this chapter, we will delve into the fascinating world of reproduction, exploring the diverse methods employed by both unicellular and multicellular organisms. These include bacteria, algae, plants, animals, and humans. We shall explore the various reproductive structures they possess and the different modes of reproduction they engage in, such as cell division, vegetative reproduction, asexual reproduction, and sexual reproduction.

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Class 10th How Do Organisms Reproduce Notes

Reproduction

Reproduction is the natural mechanism through which every organism proliferates and enhances its population size

Asexual Reproduction

Asexual reproduction is a mode of reproduction wherein a single organism is solely responsible for generating two or more offspring. This process is observed in unicellular organisms, some multicellular organisms, and certain plant species.

Fission

Fission is a prevalent form of asexual reproduction observed in many unicellular organisms. Depending on the outcome, it can be classified into two types:

Binary fission: This type of fission results in the formation of two daughter cells. An example of an organism undergoing binary fission is paramecium.
Multiple fission: In this case, fission leads to the production of multiple daughter cells. An example of an organism undergoing multiple fission is Plasmodium.

It’s important to note that the planes of fission may vary among different organisms.

Budding

Budding is a form of asexual reproduction characterized by the development of a small cyst-like structure on the parent’s body, from which a new individual emerges.

The bud may either remain attached to the parent’s body, as observed in yeast, or it may eventually separate and become an independent new individual, as seen in hydra.

Regeneration and Fragmentation

Regeneration is the remarkable process through which an organism, such as a lizard, can grow back a lost organ or body part.

On the other hand, fragmentation is a process in which an organism breaks into smaller pieces, and each fragment has the ability to develop into a complete new organism. Examples of organisms capable of fragmentation and subsequent regeneration include Planaria and Hydra.

Spore Formation

Certain organisms, like fungi, employ spores as a means of reproduction. These spores have the potential to develop into entirely new individuals once they are released from their fruiting bodies.

The sporangia are responsible for producing these spores, which are encased in a resilient outer layer, providing protection during challenging conditions.

Under favorable environmental circumstances, spores germinate, initiating their growth and development into new organisms.

Vegetative Propagation

Vegetative propagation is a form of asexual reproduction commonly observed in plants. In this process, various vegetative parts of the plant, such as leaves, stems, and roots, have the ability to give rise to new individual plants.

Natural vegetative propagation occurs through different means, including:

1. Leaves, as seen in plants like bryophyllum.
2. Stems, as observed in plants like turmeric and ginger.
3. Runners or stolons, as found in grass runners and strawberry plants.
4. Bulbs, exemplified by plants like onion and lily.

In addition to natural methods, artificial techniques of vegetative propagation are also practiced, including cutting, grafting, layering, and plant tissue culture. These methods allow for the controlled and efficient propagation of desired plant varieties.

Class 10th Sexual Reproduction Notes

The reproductive mode entails the involvement of two individuals – one male and one female – who produce specialized sex cells or gametes. These gametes then fuse together to give rise to a new organism.

Types of Cell Division

Eukaryotic organisms exhibit two distinct types of cell division:

1. Mitosis:
– Occurs in somatic cells (non-reproductive cells).
– Maintains the original chromosome number.
– Yields two diploid daughter cells (with the same number of chromosomes as the parent cell).
– Essential for asexual reproduction, development, growth, cell replacement, and regeneration.

2. Meiosis:
– Occurs in sex cells (reproductive cells).
– Reduces the number of chromosomes by half through two consecutive divisions.
– Produces four haploid daughter cells (with half the number of chromosomes as the parent cell).
– Crucial for sexual reproduction, specifically in the formation of gametes (sperm and egg cells).

The Reproductive System

Humans exhibit a significant contrast between the male and female reproductive systems. In males, the testes serve as the primary reproductive structure responsible for producing sperm, which are the male gametes.

On the other hand, the ovary is the key reproductive organ in females, where the production of ova (female gametes) takes place. Now, let us delve into a comprehensive exploration of the male and female reproductive systems in humans.

Male Reproductive System: Class 10th How Do Organisms Reproduce Notes

In males, the primary reproductive organs consist of a pair of testes. These testes play a crucial role in producing male sex cells known as sperm, as well as secreting the male sex hormone, testosterone.

Male Primary Reproductive Organ

In males, the primary reproductive organs are a pair of testes, situated within scrotal sacs outside the body. These testes consist of seminiferous tubules, which serve as the structural and functional units responsible for the production of male sex cells, sperms. The maturation of these sperms occurs in the epididymis.

Furthermore, the spaces between the seminiferous tubules contain Leydig cells or interstitial cells, which play a vital role in secreting the hormone testosterone.

Male Accessory Reproductive Organs

The reproductive process is supported by various accessory organs.

Within the reproductive system, the prostate gland and seminal vesicles function as glands responsible for producing semen and providing nourishment to the sperm.

Moreover, the penis, which accommodates the urethra, serves as a copulatory organ facilitating the passage of semen during sexual intercourse.

Male Ducts

Within males, the primary ducts involved in the reproductive process are the vas deferens and the urethra.

Each testis is connected to a single vas deferens, which serves as a conduit for transporting sperm from the testis to the urethra.

The urethra functions as a shared passageway for both semen and urine, facilitating the expulsion of semen during ejaculation and the elimination of urine from the body.

Female Reproductive System: Class 10th How Do Organisms Reproduce Notes

The female reproductive system in humans comprises a set of paired organs, including ovaries and fallopian tubes (oviducts), alongside accessory organs such as the uterus and vagina.

Female Primary Reproductive Organ

In females, the primary reproductive organs are a pair of ovaries. These ovaries play a pivotal role in producing female sex cells known as eggs or ova. Additionally, the ovaries are responsible for producing the female sex hormones, estrogen and progesterone.

Female Accessory Reproductive Organ

In human females, the uterus, oviducts, and vagina function as essential accessory reproductive organs.

The uterus serves as the site for fetal development during pregnancy, while the vagina receives sperm from the male during sexual intercourse.

Furthermore, a pair of oviducts are responsible for carrying the ovum from the ovaries to the uterus, facilitating fertilization and potential pregnancy.

Menstrual Cycle

Menstruation

Menstruation is a cyclical process where the ovum is released from the ovary and expelled from the body if fertilization does not occur.

During menstruation, the blood-rich endometrium lining of the uterus also breaks down and is shed along with the unfertilized ovum.

Various hormones play crucial roles in this process, including two pituitary hormones, LH and FSH, as well as two ovarian hormones, estrogen and progesterone.

In humans, this menstrual cycle typically repeats approximately every 28 days.

Fertilization

Human Reproduction

Humans reproduce sexually. The male produces sperms and the female produces eggs. When the sperm fuses with the egg, it forms a zygote that gives rise to a new progeny.

Contraceptive Methods

Reproductive Health

Reproductive health encompasses efforts aimed at preventing sexually transmitted diseases (STDs) and unwanted pregnancies. Moreover, fostering awareness and understanding of the reproductive system is an integral aspect of promoting reproductive health.

Contraceptives

Contraceptives are tools designed to prevent unwanted pregnancies and aid in the prevention of STDs.

These contraceptives come in various types, including mechanical barriers, hormonal/chemical methods, surgical methods, and more.

Their diverse range provides individuals with options to make informed choices regarding their reproductive health and family planning.

Coitus Interruptus

This method of contraception is highly unreliable and involves interrupting sexual intercourse before the male ejaculates inside the female reproductive tract.

Rhythm Method

Another unreliable method of contraception involves avoiding sexual intercourse when the female is fertile, and the chances of fertilization are significantly elevated.

Condoms:

Among the most effective contraception methods, condoms act as mechanical barriers, preventing semen from entering the female reproductive tract and thus avoiding pregnancy. Additionally, they provide protection against the transmission of STDs.

Diaphragms:

Diaphragms are barriers placed inside the female reproductive tract, effectively blocking semen entry and preventing pregnancy.

Contraceptive Pills:

These are chemical methods of contraception that modify hormone levels in the body, hindering the release of the ovum from the ovaries.

Emergency Pill:

Emergency pills can be taken after sexual intercourse to prevent pregnancy. They swiftly alter hormone levels, hindering successful implantation, even if fertilization has occurred.

IUD (Intrauterine Device):

IUDs are devices inserted into the uterus to alter its shape, effectively preventing the successful implantation of the zygote. They offer long-term contraception for several years.

Sterilization:

Sterilization is a permanent surgical method to achieve infertility. In males, it is called vasectomy, and in females, it is known as tubal ligation.

Reproduction in Plants

Plants employ both asexual and sexual methods for reproduction. Asexual reproduction is achieved through vegetative propagation. Now, let’s explore the process of sexual reproduction in plants.

Sexual Reproduction in Flowering Plants:

Sexual reproduction in plants occurs through flowers. The androecium and gynoecium are essential whorls of the flower involved in this process.

Non-Essential Parts of Flowers:

Apart from the essential whorls, flowers also have non-essential whorls, including sepals and petals. These parts do not directly participate in reproduction. Sepals protect the inner delicate parts during bud formation and, if green, perform photosynthesis. Petals, when colored, attract insects for pollination.

Essential Whorls of Flowers:

The androecium and gynoecium are considered the essential or reproductive whorls of a flower. The androecium produces pollen grains containing male gametes, while the gynoecium produces ovules, which are female gametes. Flowers may be bisexual (containing both whorls) or unisexual (containing either one).

Pollination:

Pollination is the transfer of pollen grains from anthers to the stigma of a flower, a necessary step for fertilization. It can occur through self-pollination (within the same flower or another flower of the same plant) or cross-pollination (between different flowers). Various agents, such as water, wind, insects, birds, and bats, play roles in cross-pollination.

Fertilization:

Fertilization involves the fusion of male and female gametes. After pollination, pollen grains germinate on the stigma surface, producing two male nuclei. The ovule contains an egg cell and two polar nuclei.

One male nucleus fuses with the polar nuclei to form a triploid endosperm. The other male nucleus fuses with the egg cell to form the zygote, which develops into the embryo and the future plant. After fertilization, the ovary transforms into a fruit, and the ovules develop into seeds, while other flower parts wither away.

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Frequently Asked Questions – FAQs on Class 10th How Do Organisms Reproduce Notes

Q 1. What is an example of an organism reproduce?

One example of an organism that reproduces is the honeybee (Apis mellifera). Honeybees engage in sexual reproduction, where the male drone transfers sperm to the queen during mating.

The queen then stores the sperm in her spermatheca and uses it to fertilize eggs throughout her life. Honeybees also exhibit a unique form of asexual reproduction called parthenogenesis.

Unfertilized eggs laid by the queen develop into male drones, while fertilized eggs give rise to female worker bees or potential new queens. This diverse reproductive strategy ensures the continuation of the honeybee colony and enables them to adapt and thrive in various environments.

Q 2. Why do organisms reproduce?

Organisms reproduce to ensure the continuation of their species and the perpetuation of life. Reproduction is a fundamental biological process that allows organisms to pass on their genetic material to the next generation.

Through reproduction, organisms produce offspring with traits that enhance their survival and adaptation to changing environments. It also aids in maintaining biodiversity and ecological balance.

Reproduction is essential for the growth and development of populations, contributing to the stability and sustainability of ecosystems. It is a fundamental drive ingrained in the biological imperative of all living beings, ensuring the survival and success of their species over time.

Q 3. What are the 3 types of reproduction?

The three main types of reproduction are: a) Asexual reproduction: Involves a single parent, and offspring are genetically identical to the parent. b) Sexual reproduction: Involves two parents, and offspring inherit a combination of genetic traits from both parents. c) Parthenogenesis: A form of asexual reproduction where unfertilized eggs develop into offspring without involving males.

Q 4. According to Class 10th How Do Organisms Reproduce Notes why is reproduction important?

Reproduction is vital for the survival and continuity of life on Earth. It ensures the perpetuation of species, the maintenance of genetic diversity, and the adaptation to changing environments. Through reproduction, organisms pass on their genetic material to future generations, allowing them to adapt and evolve over time. It is essential for the growth of populations, the balance of ecosystems, and the functioning of biological communities.

Q 5. Is reproduction a life process?

Yes, reproduction is considered a life process. It is one of the fundamental characteristics of living organisms, distinguishing them from non-living entities. Reproduction is crucial for the continuation of life and is inherent in the biological imperative of all living beings. Without reproduction, species would cease to exist, and life as we know it would not be sustained.