General Q&A for Class 12 · Page 68
5,215 free answers in General for Class 12 students, across CBSE, ICSE and State boards.
Question & Answer
Questions
- GeneralClass 12All
What are the main male and female hormones?
The primary male hormone is testosterone, produced mainly in the testes, which is responsible for developing male reproductive organs, secondary sexual characteristics (facial hair, deep voice, muscle development), and maintaining sperm production. The main female hormones are estrogen and progesterone, produced primarily in the ovaries. Estrogen triggers the development of female secondary sexual characteris
- GeneralClass 12All
How is the sex of a baby determined?
The sex of a baby is determined at conception by the combination of sex chromosomes from the parents. Every human cell contains 23 pairs of chromosomes, including one pair of sex chromosomes. Females have two X chromosomes (XX), while males have one X and one Y chromosome (XY). The mother's egg always contributes an X chromosome, while the father's sperm can carry either an X or a Y chromosome. If a sperm carrying an X chromosome fertilizes the egg, the baby will be female (X
- GeneralClass 12All
Which hormone causes metamorphosis in silk moths?
The hormone that brings about metamorphosis in silk moths, transforming the caterpillar (larva) into an adult silk moth, is called ecdysone (also known as the molting hormone). This hormone regulates the complex process of metamorphosis, during which the caterpillar undergoes dramatic physical changes inside its cocoon, breaking down larval tissues and reorganizing them into adult structures including wings, reproductive organs, and antennae. This process demonstrates how hor
- GeneralClass 12All
What is the function of adrenaline hormone?
Adrenaline (also called epinephrine) is a hormone secreted by the adrenal glands located above the kidneys. It functions as the body's "emergency hormone" or "fight-or-flight" hormone. When you face a stressful or dangerous situation, adrenaline is rapidly released into the bloodstream, causing immediate physiological changes: increased heart rate and blood pressure, faster breathing, dilation of pupils, increased blood flow to muscles, enhanced alertness, and quick release o
- GeneralClass 12All
Which comes earlier in a woman's life: menarche or menopause?
Menarche comes earlier in a woman's life. Menarche refers to the first menstrual period, which typically occurs between ages 10-15, marking the beginning of reproductive capability. Menopause, on the other hand, occurs much later, usually between ages 45-55, and signifies the end of menstrual cycles and reproductive years. The average gap between menarche and menopause is about 35-40 years, during which a woman experiences regular menstrual cycles (unless interrupted by pregn
- GeneralClass 12All
In what situations (other than menopause) do ovulation and menstruation stop in women?
Ovulation and menstruation can stop in several situations besides menopause. The most common is pregnancy, when the body stops ovulating to protect the developing fetus. During breastfeeding (lactation), hormones often suppress ovulation temporarily. Extreme stress, excessive exercise (common in athletes), or significant weight loss can disrupt the hormonal balance needed for menstruation. Medical conditions like polycystic ovary syndrome (PC
- GeneralClass 12All
Which structure is the controlling center of the cell and why?
The nucleus serves as the controlling center of the cell for several critical reasons: Genetic storage: It houses DNA (chromosomes) containing all genetic information and hereditary material Gene regulation: Controls which genes are expressed and when, thereby directing all cellular activities Cell division: Coordinates and regulates cell reproduction Protein synthesis cont
- GeneralClass 12All
On which structure are genes present and why are genes considered the most important part of any living cell?
Genes are present on chromosomes, which are thread-like structures made of DNA and proteins found in the nucleus of eukaryotic cells. Genes are considered the most important part of any living cell because they: Control heredity: Carry genetic information from one generation to the next Direct protein synthesis: Provide instructions for making proteins that perform virtually all cellular functions <s
- GeneralClass 12All
What is the difference between chromatin and chromosomes? Chromatin and chromosomes are different forms of the same genetic material:
Chromatin: Loosely coiled, thread-like network of DNA and proteins Present during the cell's resting phase (interphase) Appears as a tangled mass under the microscope Allows DNA to be accessible for transcription and replication Less condensed structure Chromosomes: Highly condensed, tightly coiled structures Visible during cell division (mitosis or meiosis)
- GeneralClass 12All
What is cytoplasm and what is its function?
Cytoplasm is the jelly-like, semi-fluid substance that fills the cell between the plasma membrane and the nucleus. It consists of water, salts, proteins, and various organic molecules. Functions of cytoplasm: Provides shape: Gives the cell its form and maintains structural integrity Holds organelles: Suspends and supports all cell organelles in their proper positions Site of
- GeneralClass 12All
Which of the following are prokaryotic and which are eukaryotic cells: Amoeba, Bacterium, Human cheek cell, Blue-green algae, Onion peel cell?
Prokaryotic Cells: Bacterium cell Blue-green algae cell (cyanobacteria) Eukaryotic Cells: Amoeba cell Human cheek cell Onion peel cell The key distinguishing factor is that prokaryotic cells (bacteria and blue-green algae) lack a membrane-bound nucleus and other membrane-bound organelles, while eukaryotic cells (Amoeba, human cells, plant cells) possess these structure
- GeneralClass 12All
What is the shape of red blood cells in humans and what function do they perform?
Human red blood cells (RBCs) have a distinctive biconcave disc shape, meaning they are round and flat with depressed centers on both sides, resembling a doughnut without a hole. Functions of red blood cells: Oxygen transport: Carry oxygen from the lungs to all body tissues using hemoglobin, a red pigment protein Carbon dioxide removal: Transport carbon dioxide from tissues back to the lungs fo
- GeneralClass 12All
How does fertilization lead to zygote formation?
Zygote formation occurs when a male gamete (sperm) successfully fuses with a female gamete (egg/ovum) during fertilization. The sperm penetrates the outer layer of the egg, and their nuclei merge, combining genetic material from both parents. This fusion creates a single cell called a zygote, which contains a complete set of chromosomes (half from each parent). The zygote then undergoes repeated cell divisions through mitosis, developing into an embryo and ev
- GeneralClass 12All
What are the main parts of the male reproductive system in humans?
The male reproductive system consists of several interconnected organs: Testes (singular: testis): Paired organs that produce sperm and testosterone Vas deferens: Tubes that transport sperm from the testes Seminal vesicles and Prostate gland: Accessory glands that produce seminal fluid Urethra: Tube that carries sperm outside the body Penis: External orga
- GeneralClass 12All
What are hormones and which term is used for endocrine gland secretions?
Hormones are chemical messengers produced by endocrine glands in our body. The secretions of endocrine glands are specifically called hormones. These powerful substances travel through the bloodstream to reach different organs and tissues, where they regulate various bodily functions including growth, metabolism, reproduction, and mood. Unlike exocrine glands that release their secretions through ducts, endocrine glands are ductless and release hormones directly into the bloo
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Which gland secretes insulin and what does it do?
The pancreas is the gland responsible for secreting insulin hormone. This vital organ acts as both an endocrine and exocrine gland. Insulin plays a crucial role in regulating blood sugar (glucose) levels by helping cells absorb glucose from the bloodstream to use for energy. When insulin production is insufficient or the body cannot use it effectively, it leads to diabetes, a condition characterized by high blood sugar levels that can cause serious health complications if lef
- GeneralClass 12All
How do endocrine glands function in the body?
Endocrine glands function as a sophisticated communication system within the body. These ductless glands produce and release hormones directly into the bloodstream rather than through tubes or ducts. Once in the blood, hormones travel to specific target organs or tissues where they bind to receptors and trigger particular responses. The endocrine system works on a feedback mechanism—when hormone levels become too high, the gland reduces production, and when levels drop too low, producti
- GeneralClass 12All
Which animals undergo metamorphosis?
From the given list, the following animals undergo metamorphosis (dramatic physical transformation during development): Butterfly: Complete metamorphosis (egg → larva/caterpillar → pupa/chrysalis → adult) Silk moth: Complete metamorphosis (egg → larva/silkworm → pupa/cocoon → adult) Frog: Incomplete metamorphosis (egg → tadpole → adult frog)
- GeneralClass 12All
What type of fertilization occurs in frogs and what are its disadvantages?
Frogs undergo external fertilization, where the female releases eggs into water and the male simultaneously releases sperm to fertilize them. The disadvantages of this method include: High gamete wastage: Most eggs and sperm don't successfully unite Environmental dependency: Requires water bodies for reproduction Vulnerability to predators: Eggs and developing tadpoles are exposed to numerou
- GeneralClass 12All
What is the difference between an embryo and a fetus?
An embryo refers to the early developmental stage following fertilization, when major organs and body systems begin forming. In humans, the embryonic stage lasts approximately 8 weeks after conception, during which critical structures like the heart, brain, and limbs develop. A fetus is the developing organism from the end of the embryonic period until birth. During the fetal stage (week 9 until delivery), the organism grows larger, o