Life Processes

Correct answer: A. Nephron

The governing concept is the microscopic organization of the excretory system. A nephron is the structural and functional unit of a kidney; each nephron filters blood, reabsorbs useful substances and water, and helps form urine. Thus option A is correct. Alveoli belong to the lungs, villi increase absorption in the small intestine, and stomata are pores in plant leaves.

Correct answer: A. Filtration of blood

Urine formation is a part of excretion, a life process that removes metabolic wastes from the body. Blood enters the kidneys, where nephrons filter it and selectively reabsorb useful substances and some water. The remaining wastes, excess salts and water form urine. Therefore, option A is correct; chewing, air entry and light capture belong to digestion, respiration and photosynthesis, not urine formation.

Correct answer: A. Ureter

The urinary system has a definite sequence: kidneys form urine, ureters carry it to the urinary bladder, and the urethra carries it from the bladder to the outside. Thus, the tube connecting a kidney with the bladder is the ureter, making option A correct. The urethra has a different direction and function, while the trachea and oesophagus belong to the respiratory and digestive systems.

Correct answer: A. Temporarily storing urine

The kidneys continuously produce urine as they remove wastes from the blood. The urinary bladder is a muscular storage sac that holds urine temporarily until it is released through the urethra during urination. Therefore, option A correctly states its main function. Pumping blood is performed by the heart, digestion occurs in the digestive tract, and oxygen is not produced by the urinary bladder.

Correct answer: A. In substances like gums and resins

Plants do not have specialised excretory organs like animal kidneys, so they use several methods to handle wastes. Some wastes are stored in forms such as gums and resins, especially in older tissues, and may later be removed when leaves or bark are shed. Therefore, option A is correct. Haemoglobin, muscles and the heart are animal structures and are not normal plant storage forms.

Correct answer: A. Water

Photosynthesis requires water and carbon dioxide as raw materials, along with light energy and chlorophyll. Roots absorb water from the soil, and xylem transports it upward to the leaves, where photosynthesis occurs. Thus, option A is correct. Carbon dioxide usually enters through leaf stomata, while starch is a product of photosynthesis and protein is not the raw material identified here.

Correct answer: A. Through stomata

Carbon dioxide is a gaseous raw material needed to make glucose during photosynthesis. Tiny pores called stomata, found mainly on leaf surfaces, open and close to regulate gas exchange; carbon dioxide diffuses through them into the leaf tissues. Therefore, option A is correct. Roots absorb water, while petals and seed coats are not the main pathways for photosynthetic gas exchange.

Correct answer: A. Absorption

Digestion breaks complex food into soluble, simple substances such as glucose, amino acids and fatty acids. These products pass through the wall of the small intestine into the blood or lymph; this movement is called absorption. Hence option A is correct. Swallowing only moves food into the alimentary canal, excretion removes wastes, and respiration releases energy rather than transferring digested nutrients into blood.

Correct answer: A. Blood

After digestion and absorption, nutrients such as glucose and amino acids enter the bloodstream from the small intestine. The circulatory system then transports these dissolved nutrients to tissues and body cells, where they are used for energy, growth and repair. Therefore, option A is correct. Hair, teeth and nails do not form a transport system for digested food; teeth only help mechanical digestion.

Correct answer: A. Glucose

Cellular respiration is the controlled oxidation of food inside cells. In the usual school-level description, glucose is broken down in the presence of oxygen to release usable energy, with carbon dioxide and water as products; without oxygen, partial breakdown can occur. Thus option A is correct. Sand, iron and glass are not cellular respiratory fuels and cannot replace glucose in this process.

Correct answer: A. Nose

During normal breathing, air first enters through the nose and then moves through the nasal cavity, pharynx, larynx and trachea toward the lungs. Nasal hairs and mucus help trap dust, while the moist lining warms and humidifies incoming air. Therefore, option A is correct. The stomach and small intestine belong to digestion, and the kidney belongs to excretion, so none of them begins the respiratory pathway.

Correct answer: A. Organisms maintain life through nutrition, respiration, transportation, and excretion

The governing concept is the coordinated set of life processes. Nutrition supplies materials, respiration releases usable energy, transportation distributes substances, and excretion removes metabolic wastes. These functions support survival in both plants and animals. Thus option A gives the complete conclusion, whereas B omits respiration, C is scientifically false, and D wrongly excludes animals.

Correct answer: A. Life processes

The governing concept is the definition of life processes. An organism must obtain or prepare food, release usable energy, distribute materials, and remove wastes in order to remain alive. Nutrition, respiration, transportation, and excretion are therefore grouped under this term. Option A is correct; heredity concerns traits, natural selection concerns evolution, and a reflex is a rapid response.

Correct answer: A. Glucose

Photosynthesis is the process by which green plants use sunlight, carbon dioxide, and water to prepare food. The immediate main product is glucose, a simple carbohydrate that stores chemical energy. Some glucose is used in respiration, while some is converted into starch for storage. Urea, bile, and saliva are not products of photosynthesis, so option A is correct.

Correct answer: A. Heterotrophs

The governing concept is nutrition. Organisms that cannot prepare their own food from simple inorganic substances and obtain it from plants or other organisms are called heterotrophs. Humans, animals, and most fungi are examples. Autotrophs and producers generally make their own food, while green plants are typical autotrophs. Therefore, option A correctly identifies these dependent organisms.

Correct answer: A. Mouth

Human digestion begins in the mouth, where food is mechanically broken into smaller pieces by the teeth and mixed with saliva. Salivary amylase begins the chemical digestion of starch there. The stomach and small intestine continue digestion later, whereas the large intestine mainly absorbs water and forms faeces. Thus, option A is the only correct answer.

Correct answer: A. Starch

Saliva contains the enzyme salivary amylase, also called ptyalin. This enzyme acts on starch, which is a complex carbohydrate, and begins converting it into simpler sugars in the mouth. Fat and protein digestion mainly starts later with other enzymes, while vitamins do not require enzymatic digestion in this way. Hence option A is correct.

Correct answer: A. Hydrochloric acid

The stomach lining contains gastric glands that release hydrochloric acid, or HCl. It creates an acidic medium needed for the action of pepsin and also helps kill many harmful microbes entering with food. Sulphuric and nitric acids are not normal stomach secretions, and citric acid is associated with citrus fruits rather than gastric juice. Therefore option A is correct.

Correct answer: A. To protect the stomach wall

Mucus secreted by the stomach forms a protective coating over its inner lining. This barrier reduces direct contact between the stomach wall and hydrochloric acid or digestive enzymes, preventing self-digestion and irritation. The heart pumps blood, plants release oxygen during photosynthesis, and kidneys form urine; none of these is the function of gastric mucus. Thus option A is correct.

Correct answer: A. Liver

Bile juice is produced by the liver, the largest gland in the human body. It is stored and concentrated in the gallbladder, then released into the small intestine. Bile contains no digestive enzyme, but its salts emulsify fats into tiny droplets, increasing the surface area for lipase. The stomach, lungs, and kidneys do not produce bile, so option A is correct.

Correct answer: A. To break fat into small droplets

The main digestive role of bile is emulsification of fats. Bile salts divide large fat globules into many tiny droplets, increasing the available surface area so that lipase can digest the fat more efficiently. Bile does not directly convert starch into glucose, bind oxygen in blood, or filter urine. Therefore option A accurately describes its principal function.

Correct answer: A. Small intestine

Most absorption of digested nutrients occurs in the small intestine. Its inner lining has numerous villi and microvilli that greatly increase surface area, while thin walls and a rich blood supply allow glucose, amino acids, minerals, and water-soluble vitamins to enter the blood. The stomach has limited absorption, and the mouth and food pipe mainly transport food. Hence option A is correct.

Correct answer: A. Villi

The finger-like projections lining the small intestine are called villi; each projection contains a network of blood capillaries and a lacteal. Villi greatly increase the internal surface area and help absorb digested nutrients efficiently. Stomata are openings in leaves, the trachea carries air, and a nephron is the functional unit of a kidney. Therefore option A is correct.

Correct answer: A. To obtain energy from food

Respiration is a life process that releases usable energy from food. During respiration, complex food molecules such as glucose are broken down, usually with oxygen and sometimes without it, and the released energy supports movement, growth, repair, transport and other cellular activities. Therefore, obtaining energy from food is the correct purpose. Urine formation, blood filtration and chewing belong to excretion, kidney function and digestion, not respiration.

Correct answer: A. Mitochondria

Mitochondria are called the powerhouse of the cell because they are the main sites of aerobic respiration in most eukaryotic cells. They break down food molecules and capture much of the released energy in ATP, which powers cellular activities. The nucleus stores genetic material, ribosomes make proteins, and the cell wall provides support. Thus mitochondria, option A, are the correct structure.