How Do Organisms Reproduce? - Class 10 Science (Compulsory Test 2) - Class 10 MCQ

The primary reason for increase in human population is:
1. The increase in agricultural production:
- With advancements in agricultural technology, farmers are able to produce more food to sustain a growing population.
- Introduction of high-yield crop varieties, irrigation systems, fertilizers, and mechanization have led to increased crop productivity and food availability.
- Enhanced agricultural practices have reduced the prevalence of hunger and malnutrition, promoting population growth.
2. The increase in birth rate and decrease in death rate:
- Improved healthcare facilities, access to safe drinking water, sanitation, and hygiene practices have significantly reduced mortality rates.
- Medical advancements, such as vaccines, antibiotics, and disease control measures, have increased life expectancy.
- Lower infant mortality rates and higher survival rates contribute to population growth.
- Social and cultural factors, such as desired family size, societal norms, and religious beliefs, also influence the birth rate.
3. The improvement in medical technology:
- Medical advancements have played a crucial role in population growth.
- Access to better healthcare services, including prenatal care, maternal care, and treatment of diseases, has increased the chances of survival for both infants and adults.
- Medical technology has also enabled assisted reproductive techniques, allowing couples facing fertility issues to conceive.
4. All of the above:
- The increase in human population is a result of a combination of factors, including agricultural production, birth rate, and medical technology.
- These factors are interrelated and contribute to the overall population growth.
In conclusion, the primary reason for the increase in human population is a combination of factors, including increased agricultural production, higher birth rates, decreased death rates, and advancements in medical technology. These factors have collectively led to improved food availability, reduced mortality rates, and enhanced healthcare, resulting in population growth.

Female sex hormones are:

• Progesterone: Progesterone is a hormone that plays a crucial role in preparing the uterus for pregnancy and maintaining pregnancy. It helps regulate the menstrual cycle and is primarily produced in the ovaries.


• Estrogen: Estrogen is a group of hormones that are responsible for the development and maintenance of female reproductive structures and secondary sexual characteristics. It plays a significant role in regulating the menstrual cycle, bone health, and maintaining the health of the vaginal lining. Estrogen is primarily produced in the ovaries.

Therefore, the correct answer is D: A & B Both as both progesterone and estrogen are female sex hormones.

The span of menstrual cycles is about 28 days.

Answer:
The organs that secrete seminal fluid are the prostate gland, Cowper's gland, and the seminal vesicle. Let's break down each of these glands and their functions:
1. Prostate gland:
- The prostate gland is a walnut-sized gland located below the bladder and in front of the rectum in males.
- It is responsible for producing and secreting a milky fluid that makes up a significant portion of semen.
- The fluid produced by the prostate gland helps to nourish and protect sperm, enhancing their survival and mobility.
2. Cowper's gland (Bulbourethral gland):
- Cowper's gland is a pair of small glands located below the prostate gland and near the base of the penis.
- These glands produce a clear, slippery fluid that is released during sexual arousal and acts as a lubricant for the urethra.
- The fluid from Cowper's gland also helps neutralize any acidic urine residue in the urethra, creating a more favorable environment for sperm.
3. Seminal vesicle:
- The seminal vesicles are a pair of glands located behind the bladder and above the prostate gland.
- These glands produce a thick, sticky fluid that makes up the majority of semen volume.
- The fluid from the seminal vesicles contains fructose, prostaglandins, and other substances that provide energy for sperm and help with their motility.
Therefore, all of these glands – the prostate gland, Cowper's gland, and the seminal vesicle – secrete seminal fluid, contributing to the composition and function of semen.

Gametes are the haploid cells which are formed in the reproductive organs. The primary reproductive organs are known as gonads.

The organs namely: testes in male and ovaries in females.

The male gamete is called sperm and is formed in testes.

The female gamete is called ovum and is formed in ovaries.

Both male and female gametes are formed by the process called gametogenesis.

Gametes are not diploid. Gametes formed by gametogenesis are the haploid cells.

They do not give rise to gonads. They are formed from the gonads.

They do not produce hormones. They fuse together to form zygotes which develop into an embryo.

Final Answer

They are formed from gonads which are true of gametes.

Answer:
Introduction:
Egg-producing animals, specifically birds, are referred to by a specific term that describes their reproductive method. In this case, the correct term is "oviparous." Let's explore this term and its meaning in more detail.
Explanation:
Egg-producing animals, such as birds, are called oviparous. This means that they reproduce by laying eggs. Here are some key points to understand about oviparous animals:
1. Oviparous Definition: Oviparous animals are those that lay eggs to reproduce. The eggs are fertilized internally and then laid outside the body, where they develop and hatch.
2. Common Examples: Birds are the most well-known example of oviparous animals. Other examples include reptiles, such as snakes, lizards, and turtles, as well as some insects, fish, and amphibians.
3. Egg Development: Oviparous animals have internal fertilization, meaning that the male's sperm fertilizes the female's eggs inside her body. After fertilization, the eggs develop and are protected by a shell that provides nutrients and a suitable environment for the growing embryo.
4. Environmental Factors: The development of the eggs and the hatching process depend on various environmental factors, such as temperature and humidity. These factors can influence the time it takes for the eggs to hatch and the survival of the offspring.
5. Advantages of Oviparity: Oviparous reproduction offers several advantages. It allows animals to reproduce in diverse habitats without the need for a constant water supply, as seen in ovoviviparous or viviparous animals. It also enables the production of a larger number of offspring at once, increasing the chances of survival.
Conclusion:
Egg-producing animals, including birds, are referred to as oviparous. This term describes their reproductive method of laying eggs, which are fertilized internally and then develop and hatch outside the body. Understanding this term helps us categorize and better understand the reproductive strategies of different animal species.

Vegetative propagation in Bryophyllum takes place by leaf.
Vegetative propagation is a form of asexual reproduction in plants, where new individuals are produced from vegetative parts of the parent plant. In the case of Bryophyllum, vegetative propagation primarily occurs through the leaves.
Process of vegetative propagation in Bryophyllum:
- Bryophyllum plants have specialized structures called plantlets or bulbils that develop on the margins of their leaves.
- These plantlets are small, bud-like structures that contain all the necessary structures to develop into a new plant.
- When the plantlets mature, they detach from the parent leaf and fall to the ground.
- Upon landing on suitable soil, the plantlets root and start growing into new Bryophyllum plants.
Advantages of vegetative propagation in Bryophyllum:
- The production of plantlets allows Bryophyllum to reproduce quickly and efficiently.
- It enables the plant to colonize new areas and expand its population.
- The plantlets are genetically identical to the parent plant, ensuring the preservation of desirable traits.
Summary:
In Bryophyllum, vegetative propagation occurs through the production of plantlets on the margins of the leaves. This method allows the plant to reproduce asexually, quickly colonize new areas, and maintain genetic uniformity.

The group of petals is called corolla.
The corolla is made up of all the petals of a flower. It is one of the main parts of the flower's structure, along with the calyx, which is made up of all the sepals. The corolla and calyx together make up the perianth of a flower.
Explanation:
- The corolla is the innermost part of the perianth, which is the non-reproductive part of the flower. It is usually colorful and attractive, serving to attract pollinators such as bees, butterflies, and birds.
- The corolla is composed of individual petals, which are often symmetrical and delicate in appearance. The number, shape, and arrangement of the petals can vary greatly between different species of flowers.
- The corolla protects the reproductive organs of the flower, including the stamens (male reproductive organs) and pistil (female reproductive organ).
- The corolla plays a crucial role in the process of pollination, as it provides a landing platform for pollinators and guides them towards the reproductive organs.
- In some flowers, the petals are fused together to form a tube or a trumpet-like structure, while in others, they are separate and distinct.
- The corolla is typically the most visually striking part of the flower and is often the reason why flowers are admired for their beauty.
In summary, the group of petals in a flower is called the corolla. It is an essential part of the flower's structure and plays a vital role in attracting pollinators and facilitating pollination.

The portion of plant that is grafted is called the scion.
- Grafting is a horticultural technique in which a part of one plant is attached to another plant in order to combine their desirable characteristics.
- The portion of the plant that is grafted is known as the scion.
- The scion is the upper part of the graft that contains the desired traits, such as specific fruit varieties or flower colors.
- The scion is usually selected for its desirable characteristics and is taken from a healthy and vigorous plant.
- It is important to choose a scion that is compatible with the stock, which is the lower part of the graft.
- The stock provides the root system and supports the scion.
- The stock is often chosen for its strong root system and disease resistance.
- When grafting, the scion is carefully attached to the stock using techniques such as whip-and-tongue or cleft grafting.
- The scion and stock are secured together and allowed to grow, forming a successful graft union.
- Grafting is commonly used in fruit tree production, where different varieties are grafted onto a single rootstock to improve yield, disease resistance, or fruit quality.

Introduction:
When it comes to producing new plants in roses, there are several methods that can be used. However, the most commonly used method is cutting.
Explanation:
Here is a detailed explanation of each method and why cutting is the preferred choice:
1. Tissue culture:
- Tissue culture is a method used for the propagation of plants in a laboratory under controlled conditions.
- It involves taking a small piece of plant tissue and placing it in a nutrient-rich medium to encourage the growth of new plants.
- While tissue culture is a widely used technique in plant propagation, it is not commonly used for roses due to the complexity and cost involved.
2. Cutting:
- Cutting is the most commonly used method for propagating roses.
- It involves taking a stem or branch from a mature rose plant and planting it in a suitable growing medium.
- The cutting develops its own roots and eventually grows into a new rose plant.
- This method is preferred because it is relatively simple, cost-effective, and produces genetically identical plants to the parent plant.
3. Layering:
- Layering is another method that can be used to propagate roses.
- It involves bending a flexible stem of a rose plant and burying a portion of it in the soil.
- The buried portion of the stem develops its own roots and eventually grows into a new plant.
- While layering can be successful in some cases, it is not as commonly used as cutting in rose propagation.
4. None of these:
- This option is incorrect as cutting is indeed the most commonly used method for producing new plants in roses.
Conclusion:
In conclusion, when it comes to producing new plants in roses, cutting is the most commonly used method. It is simple, cost-effective, and produces genetically identical plants to the parent plant. Tissue culture and layering are also options, but they are not as commonly used as cutting in rose propagation.

Development of an organism from an unfertilised ovum is called parthenogenesis.
Parthenogenesis is a form of reproduction in which an organism develops from an unfertilised egg. It is a type of asexual reproduction that occurs in certain animals, plants, and even invertebrates. Here are the key points explaining parthenogenesis:
- Definition: Parthenogenesis is the development of an organism from an unfertilised egg, without the involvement of sperm or fertilisation.
- Mechanism: In parthenogenesis, the unfertilised egg undergoes cell division and development to form an embryo, which then grows into a complete organism.
- Advantages: Parthenogenesis can be advantageous for organisms in certain situations, as it allows for reproduction without the need for a mate, thereby saving time and energy.
- Types: Parthenogenesis can be classified into different types based on the mechanism and the involvement of chromosomes. Some common types include haplodiploid parthenogenesis, thelytokous parthenogenesis, and automixis.
- Examples: Parthenogenesis is observed in various organisms. For example, some reptiles, such as certain species of lizards and snakes, reproduce through parthenogenesis. In plants, parthenogenesis can be seen in species like dandelions and strawberries.
- Implications: Parthenogenesis has both biological and evolutionary implications. It can contribute to genetic diversity and adaptation in certain populations. It can also be used as a reproductive strategy in the absence of mates or in isolated environments.
In conclusion, parthenogenesis is the development of an organism from an unfertilised egg, and it is a form of asexual reproduction observed in various organisms.

Reproduction through Regeneration:

Regeneration is the ability of an organism to replace or regrow lost or damaged body parts.

Organisms that can reproduce through regeneration:

• Hydra: Hydra is a small aquatic invertebrate that belongs to the phylum Cnidaria. It has the ability to regenerate its entire body from a small fragment or even a single cell.


• Planaria: Planaria is a type of flatworm that is known for its remarkable regenerative abilities. It can regenerate a complete organism from just a small piece of its body.

Organisms that cannot reproduce through regeneration:

• Wall lizard: Wall lizards, like most reptiles, do not have the ability to regenerate lost body parts. Once a body part is lost, it cannot be regrown.

Therefore, the correct answer is option D: Both Hydra and Planaria can reproduce through regeneration.

Binary Fission: A Form of Asexual Reproduction

Binary fission is a form of asexual reproduction commonly found in prokaryotes, such as bacteria and archaea. It involves the division of a single parent organism into two genetically identical daughter cells.

In binary fission, the parent cell undergoes a series of steps to produce two daughter cells:

• The parent cell duplicates its DNA, ensuring that each daughter cell receives a complete copy of the genetic material.


• The cell elongates and the duplicated DNA is separated into two regions of the cell.


• A new cell wall forms between the two DNA regions, dividing the parent cell into two daughter cells.


• Each daughter cell then grows and develops into a fully functional organism.

Advantages of Binary Fission:

• Efficiency: Binary fission allows for rapid reproduction, as each parent cell can give rise to two daughter cells.


• Genetic Stability: Since the daughter cells are genetically identical to the parent cell, binary fission helps maintain genetic stability within a population.


• Adaptability: The high rate of binary fission allows for quick adaptation to changing environmental conditions.

Differences from Sexual Reproduction:

• Binary fission is a form of asexual reproduction, while sexual reproduction involves the fusion of gametes from two parent organisms.


• Binary fission does not involve the exchange of genetic material between two individuals, unlike sexual reproduction.


• Binary fission produces genetically identical offspring, while sexual reproduction leads to genetic variation.

Conclusion:

Binary fission is a form of asexual reproduction where a single parent cell divides into two genetically identical daughter cells. It is a common mode of reproduction in prokaryotes and offers advantages such as efficiency, genetic stability, and adaptability. It should be noted that binary fission is distinct from sexual reproduction in terms of the process, genetic exchange, and offspring characteristics.

Explanation:
How sperms move:
- Sperms primarily move through the action of their tail, also known as the flagellum.
- The tail of the sperm is responsible for propelling it forward in order to reach the egg.
- The tail moves in a whip-like motion, creating a wave-like movement that allows the sperm to swim through the female reproductive tract.
The structure of a sperm:
- A sperm is composed of several parts, including the head, acrosome, middle piece, and tail.
- The head of the sperm contains the genetic material and is responsible for fertilizing the egg.
- The acrosome is a specialized structure located at the tip of the sperm's head. It contains enzymes that help the sperm penetrate the protective layers surrounding the egg.
- The middle piece of the sperm contains mitochondria, which provide energy for the sperm's movement.
- The tail, or flagellum, is a long, whip-like structure that propels the sperm forward.
Role of each part in movement:
- The head of the sperm contains the genetic material necessary for fertilization, but it does not play a direct role in movement.
- The acrosome, although important for fertilization, is not directly involved in the physical movement of the sperm.
- The middle piece of the sperm, specifically the mitochondria, provides the energy needed for the tail to move.
- The tail, or flagellum, is the main structure responsible for the movement of the sperm.
Conclusion:
In summary, sperms move primarily by the action of their tail, which propels them forward through a whip-like motion. The head, acrosome, and middle piece of the sperm play other important roles in fertilization and providing energy, but they do not directly contribute to the physical movement of the sperm.

Male Hormone is Testosterone:
- Testosterone is the primary male sex hormone.
- It is produced in the testicles in men and in smaller amounts in the ovaries and adrenal glands in women.
- Testosterone plays a crucial role in the development and maintenance of male reproductive tissues and secondary sexual characteristics, such as muscle mass, bone density, facial hair growth, and deepening of the voice.
- It also stimulates the production of sperm and regulates sex drive (libido).
- Testosterone levels naturally decline with age, but low levels of testosterone can lead to various symptoms and health issues, including decreased libido, fatigue, depression, reduced muscle mass, and erectile dysfunction.
- Testosterone replacement therapy may be used to treat low testosterone levels in men, but it should be done under the supervision of a healthcare professional.
In conclusion, the male hormone is testosterone, which is responsible for the development and maintenance of male reproductive tissues and secondary sexual characteristics.

Organism that shows budding:

• Spirogyra: Spirogyra reproduces through a process called conjugation, where two filaments join and exchange genetic material. It does not reproduce through budding.


• Hydra: Hydra is a freshwater organism that reproduces asexually through budding. A small outgrowth or bud develops on the body of the parent Hydra and eventually detaches to become a new individual.


• Amoeba: Amoeba reproduces through binary fission, where it divides into two identical daughter cells. It does not reproduce through budding.


• Paramecium: Paramecium reproduces through a process called binary fission, where it divides into two identical daughter cells. It does not reproduce through budding.

Therefore, the organism that shows budding is Hydra.

During pollination, pollen grains get carried to which part of the carpel?
The pollen grains get carried to the stigma of the carpel during pollination.
- Pollination is the transfer of pollen from the male reproductive organ (anther) to the female reproductive organ (carpel) in plants.
- The carpel is the female reproductive structure of a flower and consists of three main parts: the stigma, style, and ovary.
- The stigma is the sticky, receptive surface located at the top of the carpel.
- The pollen grains, which contain the male gametes, are carried by various agents such as wind, insects, or animals.
- When a pollen grain lands on the stigma, it attaches to the sticky surface.
- From the stigma, the pollen grain then germinates and grows a pollen tube.
- The pollen tube travels down through the style, which is a long tube connecting the stigma to the ovary.
- Finally, the pollen tube reaches the ovary and delivers the male gametes to the ovule, which is the female gametophyte.
- Fertilization occurs when the male gametes fuse with the female gametes in the ovule, leading to the development of seeds.
To summarize, during pollination, pollen grains get carried to the stigma of the carpel, where they germinate and grow pollen tubes to reach the ovary and deliver the male gametes to the ovule for fertilization.

Stem cutting is commonly used for propagation in:
- Mango: Stem cuttings can be used to propagate certain varieties of mangoes. The cuttings are taken from healthy, mature stems and planted in a suitable growing medium. With proper care and favorable conditions, the cuttings can develop roots and grow into new mango trees.
- Jasmine: Stem cuttings are widely used to propagate jasmine plants. The cuttings are taken from healthy, young stems and rooted in a well-draining medium. Once rooted, the cuttings can be transplanted into pots or directly into the ground to establish new jasmine plants.
- Cotton: Stem cuttings can also be used for propagating cotton plants. The cuttings are taken from the main stem of the plant and planted in a suitable medium. With proper care and favorable conditions, the cuttings can develop roots and grow into new cotton plants.
- Sugarcane: Stem cuttings are commonly used for propagating sugarcane. The cuttings, known as setts, are sections of the stem that contain buds. These setts are planted in the soil or in a suitable growing medium, and they develop roots and shoots to form new sugarcane plants.
In conclusion, stem cuttings are commonly used for propagation in mango, jasmine, cotton, and sugarcane. By taking healthy cuttings and providing them with suitable conditions, new plants can be grown from these cuttings.

Vegetative reproduction in plants like citrus, jasmine, and grapevine is done by the process of stem layering.
Stem layering is a method of vegetative propagation in which a stem is bent and partially buried in the soil while still attached to the parent plant. This allows the stem to develop roots and form a new individual plant. Here is a detailed explanation of the process:
1. Select a healthy and mature stem: Choose a stem that is flexible and not too woody. It should have several nodes (points where leaves or branches emerge) along its length.
2. Prepare the stem: Remove any leaves or branches from the lower portion of the stem that will be buried in the soil. Make a small wound or scratch on the stem to encourage root formation.
3. Bury the stem: Dig a small trench beside the parent plant and gently bend the stem into the trench. Make sure that at least one or two nodes are covered with soil. Secure the stem in place using a stake or wire if necessary.
4. Encourage root development: Keep the soil around the buried stem moist but not waterlogged. Roots will start to develop from the buried nodes, and the stem will continue to grow above the soil.
5. Sever the new plant: After a few months or when the new plant has developed a strong root system, it can be separated from the parent plant by cutting the stem below the rooted nodes.
By following these steps, plants like citrus, jasmine, and grapevine can be propagated through stem layering. It is a reliable and effective method that allows gardeners to create new plants with the same desirable characteristics as the parent plant.

Spirogyra is a filamentous green algae that exhibits both sexual and asexual modes of reproduction. In asexual reproduction, spirogyra reproduces by fragmentation. Here's a detailed explanation:
Fragmentation in Spirogyra:
- Fragmentation is a common method of asexual reproduction in Spirogyra.
- It occurs when a filament of Spirogyra breaks into smaller fragments, each of which can grow into a new individual.
- The process of fragmentation in Spirogyra involves the following steps:
1. The filament of Spirogyra undergoes cell elongation and grows to a certain length.
2. The filament then undergoes constriction at specific points, leading to the formation of transverse walls.
3. The filament breaks apart at these constricted points, resulting in the formation of smaller fragments.
4. Each fragment contains several cells, and each cell is capable of developing into an independent filament.
5. The fragments are released into the surrounding environment and can grow into new individuals under suitable conditions.
Advantages of Fragmentation:
- Fragmentation allows for rapid and efficient reproduction in Spirogyra.
- It enables the algae to colonize new habitats quickly.
- Fragmentation also helps in the regeneration of damaged or broken filaments.
Comparison with Other Methods:
- Fission: Fission refers to the splitting of an organism into two equal parts. It is not the mode of asexual reproduction in Spirogyra.
- Budding: Budding is the formation of a new individual from an outgrowth or bud on the parent organism. It is not the mode of asexual reproduction in Spirogyra.
- Multiple Fission: Multiple fission involves the division of a single cell into multiple daughter cells. It is not the mode of asexual reproduction in Spirogyra.
In conclusion, asexual reproduction in Spirogyra occurs through fragmentation, where the filament breaks into smaller fragments that can grow into new individuals. This method allows for rapid reproduction and colonization of new habitats.

The common passage for sperms and urine in the male reproductive system is the Urethra.

Explanation:

The male reproductive system consists of several organs that work together to produce and deliver sperm. The urethra is a tube that serves as a common passageway for both urine and semen. Here is a detailed explanation of the male reproductive system and the role of the urethra:
1. Testes:
- The testes are the primary male reproductive organs located inside the scrotum.
- They produce sperm and testosterone, the male sex hormone.
2. Epididymis:
- The epididymis is a coiled tube located on the back of each testicle.
- It is responsible for storing and maturing sperm.
3. Vas deferens:
- The vas deferens, also known as the ductus deferens, is a muscular tube that connects the epididymis to the urethra.
- It transports mature sperm from the epididymis to the urethra during ejaculation.
4. Seminal vesicles, prostate gland, and bulbourethral glands:
- These accessory glands secrete fluids that mix with sperm to form semen.
- The seminal vesicles contribute the majority of the fluid volume, while the prostate gland and bulbourethral glands add additional components to the semen.
5. Urethra:
- The urethra is a tube that extends from the bladder to the tip of the penis.
- It serves as a common passageway for both urine and semen.
- During ejaculation, the muscles in the urethra contract to prevent the mixing of urine and semen.
Overall, the urethra plays a crucial role in the male reproductive system by allowing the passage of both urine and semen.

Explanation:
Asexual reproduction is a type of reproduction that does not involve the fusion of gametes. Instead, it involves the production of offspring that are genetically identical to the parent organism. In asexual reproduction, a single organism can give rise to multiple offspring without the need for a mate.
Among the given options, spores are the structures that are associated with asexual reproduction. Spores are single cells that are capable of developing into a new individual without the need for fertilization. They are produced by various organisms, including fungi, plants, and some protists.
Zygote is the result of the fusion of gametes (sperm and egg) and is associated with sexual reproduction.
Gametes are the specialized cells (sperm and egg) that fuse during sexual reproduction to form a zygote.
Gonads are the reproductive organs that produce gametes.
Therefore, the correct answer is B: Spores.

The Most Fundamental Characteristics of Living Beings:
There are several fundamental characteristics that define living beings. These characteristics are essential for the survival and continuation of life. One of the most fundamental characteristics is reproduction, as it ensures the production of new individuals and the continuation of the species.
Reproduction:
- Reproduction is the process by which living organisms produce offspring of their own kind.
- It is a fundamental characteristic that allows for the continuation of life and the survival of a species.
- Reproduction can occur through sexual or asexual means, depending on the organism.
- Sexual reproduction involves the fusion of gametes (sperm and egg) from two parents, resulting in offspring with a combination of genetic traits from both parents.
- Asexual reproduction, on the other hand, involves the production of offspring without the involvement of gametes or the fusion of genetic material.
- Asexual reproduction methods include binary fission, budding, fragmentation, and regeneration.
Locomotion:
- Locomotion is the ability of an organism to move from one place to another.
- It allows organisms to find food, escape from predators, and explore new environments.
- Locomotion can be achieved through various means, such as walking, swimming, flying, crawling, or jumping.
- Different organisms have different adaptations for locomotion, such as legs, fins, wings, or specialized structures for movement.
Regeneration:
- Regeneration is the ability of an organism to replace or restore lost or damaged body parts.
- It is a characteristic commonly found in lower organisms, such as starfish, planarians, and certain reptiles.
- Regeneration allows organisms to repair and restore their tissues and organs, enhancing their survival and adaptability.
Fragmentation:
- Fragmentation is a type of asexual reproduction in which an organism breaks into fragments, each of which can grow into a new individual.
- This characteristic is observed in organisms like flatworms, sea anemones, and certain plants.
- Fragmentation enables organisms to reproduce quickly and colonize new areas.
In conclusion, while there are several characteristics that define living beings, reproduction is considered one of the most fundamental. Locomotion, regeneration, and fragmentation are also important characteristics that contribute to the survival and adaptability of different organisms.

Explanation:
The correct answer is B: two male nuclei.
When the pollen tube enters the ovule during fertilization, it contains two male nuclei. The male nuclei in the pollen tube are responsible for fertilizing the female egg cell and central cell in the ovule, leading to the formation of the zygote and endosperm.
Here is a detailed explanation of the process:
1. Pollination:
- Pollination is the transfer of pollen grains from the anther of a flower to the stigma of the same or another flower.
- The pollen grains contain male gametes, which are responsible for fertilization.
2. Pollen tube growth:
- After pollination, the pollen grain germinates on the stigma and produces a pollen tube.
- The pollen tube grows through the style and reaches the ovule.
3. Double fertilization:
- When the pollen tube reaches the ovule, it enters through the micropyle, a small opening in the ovule.
- Inside the ovule, the pollen tube releases two male nuclei.
4. Fertilization of the egg cell:
- One of the male nuclei fuses with the egg cell, forming a zygote.
- The zygote develops into an embryo, which eventually becomes a new plant.
5. Fertilization of the central cell:
- The other male nucleus fuses with the central cell, which contains two polar nuclei.
- This fusion results in the formation of the endosperm, which provides nutrients for the developing embryo.
In summary, when the pollen tube enters the ovule, it contains two male nuclei. One nucleus fertilizes the egg cell to form a zygote, while the other nucleus fertilizes the central cell to form the endosperm.

The transfer of pollen grains from anther to stigma is termed pollination.
Pollination is a crucial process in plant reproduction, where pollen grains are transferred from the male reproductive organ (anther) to the female reproductive organ (stigma) of a flower. This transfer enables fertilization and the production of seeds.
Pollination can occur through various mechanisms, including:
1. Wind Pollination: In this type of pollination, pollen grains are light and easily dispersed by the wind. Examples of wind-pollinated plants include grasses and many trees, such as oak and pine trees.
2. Insect Pollination: Many plants have co-evolved with insects to facilitate pollination. Insects, such as bees, butterflies, and beetles, are attracted to flowers by their bright colors and fragrances. As they land on the flower to collect nectar, pollen grains attach to their bodies and are transferred to other flowers of the same species.
3. Animal Pollination: Apart from insects, other animals like birds, bats, and even small mammals can act as pollinators. They are attracted to flowers and feed on nectar or fruits, inadvertently carrying pollen between flowers.
4. Self-Pollination: Some plants are capable of self-pollination, where pollen from the anther is transferred to the stigma of the same flower or a different flower on the same plant. This ensures fertilization even in the absence of external pollinators.
In conclusion, pollination is the transfer of pollen grains from the anther to the stigma, enabling the fertilization and reproduction of plants. Different mechanisms, such as wind, insects, animals, and self-pollination, facilitate this essential process.