Biology

1. (d) Although often attributed to Charles Darwin, the phrase “survival of the fittest” was actually coined by the philosopher Herbert Spencer in his work “Principles of Biology” (1864).

2.(a) Gregor Johann Mendel, an Austrian monk, conducted experiments on pea plants in the mid-19th century. He discovered the fundamental principles of inheritance, now known as Mendel’s Laws of Inheritance, which laid the foundation for the science of genetics. He is often referred to as the “Father of Genetics.”

3. (b) Cancer is a disease characterized by uncontrolled cell division and growth. When normal regulatory mechanisms that control cell division malfunction, cells can proliferate uncontrollably, forming tumors and interfering with the normal functioning of tissues and organs. Fever and inflammation are not direct consequences of uncontrolled cell division.

4. (b) A mutation is a sudden and permanent change in the DNA sequence of a gene or chromosome. Mutations can occur spontaneously due to errors in DNA replication, exposure to mutagens (such as radiation or certain chemicals), or through genetic recombination. Mutations can lead to variations in traits within a population and are a primary source of genetic diversity, which is essential for evolution to occur.

5. (a) Bacteria belong to the kingdom Monera, which includes unicellular prokaryotic organisms. Monera is one of the five kingdoms of life classification system, and it encompasses bacteria, archaea, and some other microorganisms. Bacteria are diverse and ubiquitous, inhabiting various environments and playing important roles in ecological processes, nutrient cycling, and human health.

6. (c) In binomial nomenclature, the system used for naming species in biology, the scientific name of an organism consists of two parts: the genus name (which is capitalized) and the species name (which is written in lowercase). For example, in Homo sapiens (the scientific name for humans), “Homo” is the genus name, and “sapiens” is the species name.

7. (b) Genetics is the branch of biology that deals with the study of genes, heredity, and genetic variation in organisms. By examining similarities and differences in traits among family members, such as facial features or physical characteristics, one can infer patterns of inheritance and genetic relationships. Therefore, genetics can explain why certain traits resemble those of specific family members.

8. (b) One of the key distinguishing features between plant and animal cells is the presence of a cell wall in plant cells and its absence in animal cells. Plant cells have a rigid cell wall composed primarily of cellulose, which provides structural support and protection to the cell. In contrast, animal cells lack a cell wall and instead have a flexible plasma membrane that surrounds the cell’s cytoplasm and organelles. Additionally, both plant and animal cells have nuclei, although the size and shape of the nucleus may vary between cell types. Vacuoles, which are membrane- bound organelles involved in storage and waste management, are typically larger and more prominent in plant cells compared to animal cells.

9. (b) Gregor Mendel is considered the father of modern genetics. His experiments with pea plants in the 19th century led to the discovery of the basic principles of heredity and inheritance.

10. (a) The kiwi is a flightless bird and a vertebrate, meaning it has a backbone. Sponges, starfish, and threadworms are invertebrates and lack a backbone,

11. (a) The electron microscope was invented by Ernst Ruska and Max Knoll in 1931. They were awarded the Nobel Prize in Physics in 1986 for their work.

12. (b) The centromere is the point where chromatids are attached in a chromosome, facilitating spindle fiber attachment and sister chromatid separation during cell division.

Nucleosomes are units of DNA packaging consisting of DNA wrapped around histone proteins.

Centrosomes are organelles in animal cells responsible for organizing microtubules during cell division.

Genes are units of heredity containing înstructions for specific traits.

13. (d) The group of the cell of similar origin, function, and structure is called tissue.

The plant tissue is of four types: Epidermal tissue, Vascular tissue, Ground tissue, and Meristematic tissue.

Human Body is made up of four types of tissue: Nervous, Muscle, Epithelial and Connective tissue.

14. (d)

15. (c) Turtle – Reptiles

Crocodile – Reptiles

Toad – Amphibia

Snake – Reptiles

16. (c) A fungal cell wall is made up of a tough and complex sugar called ‘Chitin’. Fungi are non-green, eukaryotic, hetero- trophic organisms. Most of them are saprotrophs. They feed upon decaying organic matter.

Examples: yeast, Aspergillus, Penicillium, Mushrooms.

17. (a) Metaphase: Chromosomes align at the equatorial plate, spindle fibers attach to the centromeres of each chromosome.

18. (b) Sclerenchyma is the permanent tissue  that makes a plant hard and stiff.

Collenchyma cells are those which have irregularly thick cell walls which provide support and structure.

Parenchyma are thin-walled tissues which are involved in food storage, photosynthesis, and other activities of plant life.

Aerenchyma are spongy tissues which form air channels in the leaves, stem, and roots of some plants.

19. (a) Only meristem is capable of cell division.

Meristem: This is the primary growth tissue in plants, found in the tips of roots and shoots, and responsible for increasing the plant’s length and girth. Meristematic cells are undifferentiated and have the ability to continuously divide, giving rise to other specialized tissues.

20. (a) Oparin’s theory proposes that life arose from simpler organic molecules in a “primordial soup” through a series of chemical reactions. This concept falls under the umbrella of chemical evolution, which explores how life emerged from non-living matter.

21. (b) The group of animals that are exclusively free-living marine animals is Echinodermata. Echinoderms include animals such as starfish, sea urchins, and sea cucumbers, which are found exclusively in marine environments.

22. (a) Agaricus: This is a genus of mushrooms, which are classified as fungi. Fungi are eukaryotic organisms that are typically multicellular.

23. (b) Arthropoda is the largest group of animals. An Arthropoda is an invertebrate animal that forms the phylum Arthropoda, which includes insects, arachnids, myriapods, and crustaceans. Over two-thirds of all named species on Earth are Arthropoda.

24. (c) Sclerenchyma is characterized by thick, lignified cell walls that provide strength and rigidity to plant structures like seeds, nutshells, and woody stems. The cells in sclerenchyma are dead at maturity, as the thickened cell walls prevent further growth and metabolic activity.

25. (c) A cell is the smallest unit capable of independent existence and reproduction. All living organisms, except viruses, are composed of cells.

26. (b) Stomata are tiny pores located on the underside of a leaf’s surface. They regulate the exchange of gases, including carbon dioxide (CO₂) and oxygen (O2), between the leaf and the atmosphere during photosynthesis and respiration. Carbon dioxide enters the leaf through the stomata, where it is used in photosynthesis to produce sugars and oxygen

27. (d) Pea plants, like other legumes, have a symbiotic relationship with nitrogen-fixing bacteria called rhizobia. These bacteria live in nodules on the roots of leguminous plants like peas and convert atmospheric nitrogen (N₂) into a form that the plants can use, such as ammonia (NH₂) or nitrate (NO₂). This process, known as nitrogen fixation, enriches the soil with nitrogen and makes it available to other plants in the ecosystem. Therefore, growing peas or other legumes can improve soil fertility and reduce the need for synthetic nitrogen fertilizers.

28. (a) Xylem is the plant tissue responsible for transporting water and minerals from the roots to the leaves and other parts of the plant. It consists of specialized cells called tracheids and vessel elements, which form interconnected tubes that facilitate the upward movement of water through capillary action and transpiration. This water transport system enables the leaves to receive the water necessary for photosynthesis and other metabolic processes.

29. (c) Photosynthesis requires solar radiation to convert solar energy into chemical energy, which is stored in glucose. Although a pigment (such as chlorophyll) and an atmospheric gas (carbon dioxide) are essential components, these terms are broader and include multiple elements. Hence, the most appropriate option is solar radiation.

30. (c) Crop rotation is an agricultural practice in which different crops are grown in the same area in sequential seasons or years. It helps to improve soil fertility and structure by returning nutrients to the soil and preventing the depletion of specific nutrients. Different crops have varying nutrient requirements and root structures, so rotating crops can help balance soil nutrient levels, reduce pest and disease pressure, and improve overall soil health and productivity.

31. (a) Differentiation is the process of taking up a permanent shape, size, and function to form a permanent tissue. During the process of differentiation, cells combine to form a specific tissue. The tissue acquired a specialized function as a result. The process of differentiation usually takes place during the stage of embryonic development.

32. (a) Meristematic tissue comprises undifferentiated cells and is found in plant regions where growth occurs. There are three types of meristem in plants: apical, lateral, and intercalary. Apical meristem is responsible for new cell growth at the tips of roots and shoots, forming buds in young seedlings. Lateral meristem divides to increase the stem or root girth in plants. Intercalary meristem, located at the internode base, facilitates cell division, leading to rapid growth in monocots.

33. (d) Cuscuta derives nutrition from plants as a parasite. The organism that lives on or inside other living organisms, to derive their food are called parasites. All parasitic plants have modified roots, called haustoria. Parasites may cause harm to the host. Examples of parasites: Cascuta, Loranthus, Balanophora, Sandalwood tree.

34. (b) Gibberellic acid (GA): This is a plant hormone that plays a crucial role in promoting stem elongation and overcoming genetic dwarfism in plants. When applied to dwarf plants, gibberellic acid stimulates cell division and elongation, leading to increased plant height and normal growth patterns.

35. (a) Phytohormones, also known as plant hormones, are chemical messengers produced within plants. They are synthesized by plants themselves, unlike substances used for photosynthesis or peeling, which are often external factors. Phytohormones have a profound influence on various physiological processes in plants, regulating aspects like growth, development, and response to stress.

36. (c) Vitamin K is essential for the coagulation (clotting) of blood. It plays a crucial role in the synthesis of clotting factors in the liver, which are necessary for the formation of blood clots to prevent excessive bleeding. Without an adequate supply of vitamin K, the blood’s ability to clot properly is impaired, leading to an increased risk of bleeding disorders and excessive bleeding.

37. (c) The Rhesus factor is a protein found on the surface of red blood cells and is unrelated to cholesterol. LDL and HDL are types of cholesterol, while “packaged protein coat” can be associated with lipoproteins.

38. (a) The energy obtained from food is measured in calories, which quantify the amount of energy released when food is metabolized by the body.

39. (a) Retinol is a form of vitamin A, which is essential for vision, immune function, and skin health.

40. (c) Homogenization is the process of breaking down fat globules in milk so they remain evenly distributed and do not separate.

41. (c) Zymase is an enzyme complex that catalyzes the fermentation of glucose into ethanol (ethyl alcohol) and carbon dioxide during the process of alcoholic fermentation.

42. (c) The normal range for blood sugar levels in a fasting state is typically considered to be between 70 to 100 milligrams per deciliter (mg/dL). This range may vary slightly depending on individual factors and the specific guidelines used.

43. (b) Vitamin B1 is also known as thiamin. It is an essential nutrient required for carbohydrate metabolism and proper functioning of the nervous system.

44. (b) Rancidity occurs when fats undergo oxidation due to a biochemical reaction with oxygen. This process alters the taste and smell of the food, resulting in what is commonly referred to as rancidity.

45. (d) Vitamin K plays a crucial role in blood clotting and the prevention of excessive bleeding. It activates proteins and calcium necessary for blood clotting. Vitamin K exists in three forms: K1 (Phylloquinone), K2 (Menaquinone), and K3 (Menadione).

46. (a) The arrangement for the given food chain will be:

C. Rice Plant – It produces food using solar energy.

E. Locust – Locust are primary consumers, They eat plants.

A. Frog – Frogs are secondary consumers, They eat Locust.

D. Snake – Snakes are tertiary consumers, They eat frogs.

B. Eagle – Eagles are Quaternary consumers, They eat snakes. So, the correct food chain is: ‘C – E – A – D – B’.

47. (a) To detect the presence of starch in food, an iodine solution is used. When iodine solution is added to a sample containing starch, it changes color from brown to blue-black, indicating the presence of starch.

48. (c) Lipase enzymes are used in the stabilization of rice bran oil. Rice bran oil, known for its nutritional properties, is extracted from the outer layer of rice. Lipase helps in inactivating natural lipases that could otherwise hydrolyze the oil, leading to a rancid taste and smell.

49. (a) Waterborne diseases are caused by pathogenic microorganisms that are transmitted through contaminated water. Disinfection of water involves the killing or inactivation of these microorganisms using methods such as chlorination, ultraviolet (UV) irradiation, or filtration, thereby making the water safe for consumption.

50. (b) Viruses are microscopic infectious agents that are composed of genetic material (either DNA or RNA) surrounded by a protein coat called a capsid. Some viruses also have an outer lipid envelope derived from the host cell’s membrane. The genetic material of the virus (either DNA or RNA) carries the instructions for viral replication and infection, while the protein coat protects the genetic material and helps the virus infect host cells.

51. (c) Thalassemia is a genetic disorder characterized by abnormal hemoglobin production, leading to anemia. Individuals with thalassemia have mutations in the genes responsible for producing hemoglobin proteins, which results in reduced or abnormal hemoglobin production. This genetic condition is inherited from one or both parents who carry thalassemia gene mutations. Thalassemia is not caused by lifestyle factors, infectious agents, or metabolic abnormalities but rather by genetic inheritance.

52. (b) HIV (Human Immunodeficiency Virus) is a retrovirus that infects cells of the human immune system, specifically targeting CD4+ T cells. HIV gradually weakens the immune system over time, leading to acquired immunodeficiency syndrome (AIDS), a condition characterized by the progressive failure of the immune system and increased susceptibility to opportunistic infections and certain cancers.

53. (b) Leprosy, also known as Hansen’s disease, is caused by the bacterium Mycobacterium leprae. It primarily affects the skin, peripheral nerves, upper respiratory tract, and eyes. The disease is named after Dr. Gerhard Henrik Armauer Hansen, who identified the causative bacterium in 1873.

54. (d) Louis Pasteur developed the first successful rabies vaccine in 1885. His work in microbiology and vaccination was ground breaking and saved many lives.

55. (c) The Western blot test is a laboratory method used to detect specific proteins in a sample and is commonly used to confirm the presence of HIV antibodies.

56. (b) Cirrhosis is a chronic liver disease characterized by scarring (fibrosis) and impaired liver function.

57. (d) Hepatitis B is primarily transmitted through blood and bodily fluids, not airborne transmission.

58. (d) Allergy screening tests such as RAST, ELISA, and IgE specifically measure the immune response to allergens. Hemoglobin is a measure of blood’s oxygen-carrying capacity and is not related to allergies.

59. (c) Silicosis is a lung disease caused by inhaling silica dust, typically in occupational settings like mining, construction, and manufacturing.

60. (a) Color blindness is typically a genetic condition, meaning it’s inherited and present from birth. It results from abnormalities in the genes responsible for the perception of color.

61. (a) Yellow fever is primarily transmitted to humans through the bite of infected female mosquitoes, particularly those of the Aedes aegypti species. These mosquitoes can carry the yellow fever virus and transmit it to humans when they feed on blood.

62. (d) Dehydration occurs when there is a loss of water from the body, either through inadequate intake, excessive sweating, vomiting, or diarrhea. It disrupts normal bodily functions and can lead to sérious health complications if left untreated.

63. (b) Typhoid fever is caused by the bacterium Salmonella typhi. It is transmitted through contaminated food and water and affects the gastrointestinal tract, leading to symptoms such as fever, abdominal pain, and diarrhea.

64. (a) Poliomyelitis, commonly known as polio, is caused by the poliovirus, which primarily affects the nervous system, leading to paralysis. It is transmitted through contaminated food and water.

65. (c) Chloroquine is a medication used to prevent and treat malaria, a mosquito-borne infectious disease caused by parasites of the Plasmodium species.

66. (d) Antacids are used to neutralise acidity.

67. (d) Vitamins are essential organic non- protein substances required for normal metabolic function, but they cannot be synthesized in sufficient quantities by organisms. They are classified into two categories: fat- soluble and water-soluble. Fat-soluble vitamins (A, D, E, K) are stored in the body when not in use, unlike water- soluble vitamins. Water-soluble vitamins (B, C) are easily excreted by the body if consumed in excess.

68. (a)

• Hepatitis A is caused by the Hepatitis A virus (HAV).
• It spreads through the ingestion of contaminated food or water and close contact with an infected person but does not lead to chronic liver disease.

69. (b)

• The housefly belongs to the order Diptera and genus Musca, with the scientific name Musca domestica.
• Houseflies are often considered nuisances and health hazards, but their larvae can be useful for feeding livestock and biodegradation.

70. (b) Alexander Fleming discovered penicillin. This discovery led to the introduction of antibiotics that greatly reduced the number of deaths from infection. Penicillin prevents the bacteria from synthesizing peptidoglycan, a molecule in the cell wall that provides the wall with the strength it needs to survive in the human body.

71. (b)

• It is the well-known natural-source cancer(Breast, lung, and ovarian) drug in the USA and is one of the best plant- based treatments available.
• Taxol is obtained from the bark of the Yew tree.
• The process was invented by Robert Holton of Florida State University was licensed and developed to produce taxol by Bristol Myer.

72. (a)

• The female Anopheles mosquito transmits malaria, an acute febrile illness caused by the Plasmodium parasite.
• When the mosquito bites a person, it injects the parasite into the bloodstream. Malaria is prevalent in tropical and subtropical regions around the equator.

73. (c)

• The Aedes mosquito is a carrier of the dengue virus, which causes dengue fever. Symptoms include high fever, headache, vomiting, muscle and joint pains, and a . characteristic skin rash.
• The disease typically manifests three to fourteen days after infection and lasts for about two to seven days.

74. (c) UVA causes your skin to wrinkle, tan and/or burn. Too much exposure leads to skin cancer. UVB can damage the outermost layers of your skin. It can cause sun spots, tanning, sunburns and blistering, which can lead to skin cancer.

75. (c) Warts are caused by the human papillomavirus (HPV). This virus infects the top layer of the skin, causing an excess production of keratin, which results in the formation of the rough, hard texture characteristic of warts.

76. (c) The average gestation period for a human fetus, from conception to birth, is approximately 280 days or 40 weeks. However, it can vary slightly from individual to individual.

77. (c) Endosperm serves as nutritive tissue for groutting embryo. Endosperm is a tissue found around the embryo in angiosperm seeds, supplying it with nutrients like starch and protein.

• The ovary, a part of the female reproductive system, generates female gametes and transforms into fruit post-fertilization. Ovules, located within the ovary, mature into female reproductive cells and evolve into seeds upon fertilization.
• When sperm fertilizes an egg, the resulting entity is known as a zygote.

78. (c) The urethra is a tube that carries urine from the Urinary bladder. In females, urethra contains only urine, while in males, it contains both urine and sperms.

79. (b) The testis serves as the primary male sex organ. Situated in the scrotum, the testis houses seminiferous tubules where sperm production occurs. Sertoli cells within the seminiferous tubules nourish male germ cells. Leydig cells in the testis produce male hormones, including androgens.

80. (a) The egg is carried from the ovary to the womb through the oviduct, also known as the fallopian tube.

81. (c) Motile: means capable of movement.

Germ cell: is a reproductive cell that carries half the genetic information and fuses with another germ cell during fertilization to create a new organism.

Isogamete: is a gamete that is similar in size, shape, and behavior to the gamete with which it fuses. They are not motile in most cases.

Female gamete: is called an ovum or egg cell and is not motile.

Male gamete: is called a sperm or spermatozoon and is the motile germ cell responsible for reaching and fertilizing the egg.

82. (d) Genes: These are the fundamental units of heredity, located on chromosomes in the nucleus of a cell. They are composed of DNA (deoxyribonucleic acid) and contain the instructions that determine an organism’s traits and characteristics.

83. (a) Reproduction allows species to continue existing by creating new generations. Without it, populations would dwindle and eventually disappear. Circulation, digestion, and respiration are all important bodily functions, but they don’t directly contribute to maintaining a species’ population size.

84. (a) The part of the human reproductive system that helps the embryo get its nutrition from the mother’s blood is the placenta. The placenta is a temporary organ that forms inside the uterus during pregnancy. It connects the developing baby (fetus) to the mother’s uterine wall and serves several important functions.

85. (c) The embryo develops in the uterus. The utreus, fallopian tubes, and cervix are all part of the female reproductive system, but they play different roles in reproduction.

86. (d) Testes are located in the scrotum, outside the abdominal cavity, to maintain a lower temperature necessary for spermatogenesis. The scrotum ensures a temperature about 2-2.5°C lower than the normal internal body temperature.

87. (c) The cornea is the part of the human eye that acts as a protective barrier and helps focus light.

88. (b) The iris works with the rest of your eye to help you see. Specifically, it controls how much light enters your eye. Muscles in your iris adjust your pupil automatically based on changes in lighting.

89. (b) The iris, the colored part of the eye, controls the size of the pupil and the amount of light that enters the eye. In bright light, the iris contracts to make the pupil smaller and reduce the amount of light that enters the eye. This is called the pupillary light response.

90. (b) The vestibular system detects head movements and sends information to the brain to help maintain balance, while the part of the inner ear responsible for hearing is the cochlea.

91. (c) Photoreceptor cells are specialized cells that convert light into signals that the brain can use to create a visual image. The retina is a layer of cells in the eye that contains photoreceptors and glial cells.

92. (a) The optic nerve is comprised of millions of nerve fibers that send visual messages to your brain to help you see. You have an optic nerve at the back of each eye that connects directly to your brain.

93. (c) The pinna is the visible part of the outer ear, made of cartilage covered by skin. It acts like a reverse megaphone to funnel sound waves into the ear canal.

94. (a) The eardrum is a thin, semi-transparent, oval-shaped membrane that’s about 1 cm in diameter. When sound waves hit the eardrum, it vibrates, and these vibrations are then passed on to the tiny bones in the middle ear. These bones are called the ossicles, and are commonly referred to as the “hammer” (malleus), “anvil” (incus), and “stirrup” (stapes).

95. (a) The cochlea is filled with a fluid that moves in response to the vibrations from the oval window. As the fluid moves, 25,000 nerve endings are set into motion. These nerve endings transform the vibrations into electrical impulses that then travel along the eighth cranial nerve (auditory nerve) to the brain.

96. (d) The receptors responsible for transduction of odor molecules are found in the olfactory mucosa. This portion of nasal mucosa is 1 to 2 cm² in size and is located in the roof of the nasal cavity on the inferior surface of the cribriform plate and along the nasal septum and medial wall of the superior turbinate.

97. (d) Cones are photoreceptor cells in the retina of the eye that are responsible for color vision. Cones are sensitive to different wavelengths of light and allow the brain to perceive colors. Rods, on the other hand, are responsible for vision in low-light conditions but do not perceive color.

98. (d) Receptors are specialized structures composed of protein, which respond to light, heat or external stimulus and transmit the signal to the sensory nerve. 

Gustatory receptors are the receptors for detecting taste.

99. (c) The sensation of sound persists in the human brain for about 0.1 sec. This is also known as the persistence of hearing.

100. (d) Warm-blooded animals, such as birds and mammals, maintain a constant body temperature regardless of the environmental temperature.

101. (c) The ability of the eye to focus on both near and distant objects by adjusting its focal length is known as accommodation. This is achieved by the eye muscles adjusting the lens to change its shape and focal length.