Learn 80 questions from K-TET III -December 2025 - Part III (Natural Science)

K-TET III -December 2025 - Part III (Natural Science) Questions

• Bt cotton is resistant to insects.

Bt cotton is genetically modified by inserting genes from Bacillus thuringiensis (Bt), which produce proteins toxic to specific insect pests like lepidopteran larvae (bollworm, tobacco budworm).

This modification targets chewing insects but does not provide resistance against bacteria, fungi, or nematodes.

• Thomas Henry Huxley, often known as "Darwin's Bulldog," coined this phrase in the 19th century to highlight the deep evolutionary connection between birds and reptiles.

Huxley was one of the first scientists to propose that birds evolved from small carnivorous dinosaurs. From a biological standpoint, he argued that birds are essentially a highly specialized, "glorified" branch of the reptilian family tree.

• In the immune system, lymphoid organs are classified based on their function. Primary (central) lymphoid organs are the sites where lymphocytes (white blood cells) are generated and matured.

Bone Marrow: This is the site where all blood cells are produced (haematopoiesis). It is specifically where B-lymphocytes (B-cells) mature.

Thymus: This is a gland located behind the breastbone. Progenitor cells migrate from the bone marrow to the thymus to develop into T-lymphocytes (T-cells).

Annual rings (also known as growth rings) are the result of secondary growth in woody plants, specifically trees. This process is driven by the activity of the vascular cambium, a layer of meristematic tissue.

 Secondary growth increases the girth (thickness) of the stem. Each year, the vascular cambium produces new layers of secondary xylem (wood) towards the inside and secondary phloem towards the outside.

•  The thyroid gland consists of two lobes connected by an isthmus. Each lobe is made up of thyroid follicles (which produce $T_3$ and $T_4$) and stromal (connective) tissues.
•Humans typically have four parathyroid glands (two pairs), located on the posterior surface of the lobes of the thyroid gland.
• The Pineal gland secretes Melatonin (which regulates the sleep-wake cycle). Thymosin is actually secreted by the Thymus gland.
• Cortisol is a Steroid hormone (derived from cholesterol), not a protein hormone. Protein hormones include things like Insulin or Growth Hormone.

The number of parathyroid glands in humans is three.

The thyroid gland is composed of follicles and stromal tissues.

In a collateral vascular bundle, the xylem and phloem are positioned on the same radius. In the specific case of dicot stems, these bundles are typically "open," meaning they possess a layer of meristematic tissue called cambium that allows for secondary growth (thickening of the stem).

Phloem: Located toward the outside (periphery) of the stem.

Xylem: Located toward the center (pith) of the stem.

Cambium: A thin strip of cells sandwiched between the two, acting as a "growth engine."

Xylem and phloem arranged on alternate radii

Xylem internal and phloem external with cambium in between

• This breakthrough, published in the journal Nature in 1964 and 1966, was a landmark event in plant biotechnology. It was the first time scientists successfully produced haploid embryos (and subsequently seedlings) from pollen grains through the culture of excised anthers.

• In the anatomy of the kidney, the renal pelvis acts as a funnel-like dilated part of the ureter. The "projections" or cup-like extensions within this area are known as calyces (singular: calyx).

• Acid rain is formed when sulfur dioxide (SO2) and nitrogen oxides (NOx) react with water molecules in the atmosphere. When it falls, it pollutes the soil by leaching nutrients. Therefore, it is a source of pollution, not a result of contaminated soil.

• Penicillium is a classic example of a fungus that reproduces asexually via conidia.

• Interkinesis (also known as interphase II) is a short-lived metabolic stage that occurs between the two main divisions of meiosis: Meiosis I and Meiosis II.

• Sickle cell anaemia results from a specific point mutation (substitution of adenine for thymine in the beta-globin gene on chromosome 11), causing glutamic acid to be replaced by valine at position 6 of the beta-globin chain. This is inherited in an autosomal recessive pattern, where both alleles must carry the mutation for the disease to manifest.

Male Ascaris has a single, long, coiled testis that extends through much of the posterior pseudocoel, producing sperm that travels via vas deferens to the cloaca. Females possess two ovaries, each leading to an oviduct and uterus, forming a didelphic (double) reproductive system.

• Chlorosis, or yellowing of leaves due to chlorophyll loss, commonly results from deficiencies in magnesium (key component of chlorophyll molecule), iron (essential for chlorophyll synthesis), and nitrogen (needed for chlorophyll production).

Transpiration pull serves as the main mechanism driving sap ascent in tall trees, overcoming gravity through the cohesive tension in xylem. This process creates negative pressure (tension) in the leaf xylem as water evaporates from mesophyll cells during transpiration, pulling a continuous water column upward from roots.

Both (A) and (R) are true and (R) correctly explains (A).

Both (A) and (R) are true but (R) does not explain (A).

• The Sundarbans, spanning India and Bangladesh, is the world's largest mangrove ecosystem and primary habitat for the Royal Bengal Tiger, supporting around 114 tigers in the Indian portion alone.

• Primary succession begins on completely barren, lifeless areas lacking soil, such as bare rock surfaces newly exposed by glacial retreat or volcanic activity, where pioneer species like lichens must first create soil.

• Photolysis of water, where H₂O splits into oxygen, protons, and electrons, happens specifically at Photosystem II (PS II) during non-cyclic photophosphorylation, providing electrons to replenish those excited in PS II.

Cyclic photophosphorylation produces both ATP and NADPH.

Non-cyclic photophosphorylation involves only PS I.

ATP synthesis occurs in the thylakoid lumen.

The radula is a chitinous, file-like structure with teeth found in molluscs (e.g., snails, squids), used for scraping food, rasping algae, or tearing prey

Balanoglossus belongs to the phylum Annelida

• Bryophytes (mosses, liverworts, hornworts) exhibit a dominant haploid gametophyte phase that is photosynthetic and independent, while lacking vascular tissue (xylem/phloem). The sporophyte remains attached to and nutritionally dependent on the gametophyte throughout its life.

• The Red Data Book, maintained by the IUCN, records endangered plants and endangered animals (along with fungi and certain local subspecies) to assess extinction risk and guide conservation efforts.

• Pteridophytes (ferns, horsetails, clubmosses) represent the first vascular plants in evolutionary history, appearing in the Silurian period (~430 million years ago) with true xylem and phloem for water and nutrient transport

• Monocot stems lack the vascular cambium (lateral meristem) present between primary xylem and phloem in dicots, preventing secondary growth that produces annual rings and girth increase.

No cambium layer between xylem and phloem

• Nerium (oleander or kaner) exhibits whorled phyllotaxy, where three or more leaves emerge from each node in a circular arrangement around the stem.

• Abscisic acid (ABA) mediates stomatal closure primarily by triggering the efflux of potassium ions (K⁺) from guard cells through activation of anion channels and outward-rectifying K⁺ channels. This ion loss reduces osmotic potential, causing water efflux and decreased turgor pressure that collapses the guard cells.

• Cyclic photophosphorylation involves only Photosystem I, where excited electrons cycle back through an electron transport chain to generate ATP via chemiosmosis, without producing NADPH or splitting water.

• Malpighian bodies (also called renal corpuscles) are the filtration units in nephrons, consisting of the glomerulus (capillary tuft) enclosed by Bowman's capsule, located in the kidney cortex.

• Ctenophores (comb jellies) do not exhibit polyp and medusa body forms; these are characteristic of the phylum Cnidaria (jellyfish, corals, sea anemones). Ctenophores have a distinct biradial symmetry and biradial body plan.

Exhibit two basic bodyforms called polyp and medusa

• Auxin, primarily produced in shoot apical meristems, promotes apical dominance by inhibiting lateral bud growth through polar transport down the stem, ensuring dominant main stem elongation.

• Blood group O is defined by the complete absence of both A and B antigens on the surface of red blood cells (RBCs), making it the "null" type in the ABO system.

• Amphibians first appeared during the Devonian period (approximately 375-359 million years ago), evolving from lobe-finned fish ancestors like Ichthyostega and Elginerpeton that developed limbs capable of terrestrial movement.

• The light reactions of photosynthesis, including photophosphorylation and photosystems I and II, occur specifically in the thylakoid membranes of chloroplasts where chlorophyll is embedded.

• A calyx is persistent when its sepals remain attached to the fruit after flowering, providing protection as seen in tomatoes and eggplants.
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Why (R) is False
Persistent calyces occur across various flower types, including hypogynous (tomato, Solanaceae) and perigynous flowers, not exclusively or characteristically in epigynous flowers where the ovary is inferior. The persistence depends on genetic programming rather than gynoecium position.
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• Ozone depletion in the stratosphere, primarily caused by CFCs, reduces the protective ozone layer, allowing more harmful UV-B radiation to reach Earth's surface and increasing risks like skin cancer and ecosystem damage. Meanwhile, global warming results from greenhouse gases (CO₂, methane, etc.) trapping outgoing infrared radiation in the troposphere, creating the enhanced greenhouse effect.

Ozone depletion is mainly due to CO₂ emissions, while global warming is caused by CFCs.

Ozone depletion increases UV-B reaching Earth, while greenhouse X gases trap infrared radiation causing global warming.

Both are primarily caused by methane from agriculture.

Global warming reduces the greenhouse effect, ozone depletion increases it.

• According to the cohesion-tension theory, transpiration pull serves as the primary driving force for sap ascent, creating tension through water evaporation from leaf mesophyll cells that pulls a continuous water column upward via xylem cohesion and adhesion to vessel walls.

• Selection (vi): Choosing a healthy, high-yielding, or disease-resistant mother plant to ensure the clones have the best possible traits.

Surface Sterilization (i): Treating the explant (the small piece of plant tissue) with chemicals like sodium hypochlorite to kill any bacteria or fungi before it enters the sterile culture.

Callus Initiation (ii): Placing the explant on a medium high in auxins. This triggers the cells to divide into a callus—an unorganized mass of undifferentiated cells.

Shoot Differentiation (iii): Moving the tissue to a medium with a high cytokinin-to-auxin ratio. This hormonal shift signals the callus to start developing visible shoots.

Root Induction (iv): Once shoots are established, they are treated with auxins again (at specific concentrations) to encourage the growth of a functional root system.

Hardening and Acclimatization (v): The most delicate stage. The plantlets are moved from the controlled "lab life" to a greenhouse. This gradually toughens them up to handle natural humidity and temperature fluctuations before they hit the field.

• Meiosis involves two divisions: meiosis I reduces the diploid (2n) chromosome number to haploid (n) in two cells, and meiosis II divides those into four haploid cells.

•  Statin: These are blood-cholesterol-lowering agents. They are commercially produced by the yeast Monascus purpureus. Statins work by competitively inhibiting the enzyme responsible for the synthesis of cholesterol.

• Biochemical Oxygen Demand is a critical measure used in environmental biology and wastewater treatment to determine the pollution level of a water body. It represents the amount of dissolved oxygen (O2) required by aerobic microorganisms to break down (oxidize) the organic matter present in a given sample of water at a certain temperature over a specific period.

• Bioreactors are not limited to plant tissue culture. They are large-scale vessels (often 100–1000 liters) used for the mass production of various biological products, including:

Pharmaceuticals: Production of insulin, vaccines, and recombinant proteins.

Microbial Cultures: Growing bacteria or fungi to extract enzymes (like proteases) or organic acids.

Animal Cell Culture: Used in the development of monoclonal antibodies.

Waste Treatment: Large-scale aerobic and anaerobic digestion.

Restriction enzymes cut DNA at specific sites

Bt toxin gene is used for insect resistance

Bioreactors are used only for plant tissue culture

• Alkaline phosphatase removes 5' phosphate groups from linearized vector ends, preventing DNA ligase from joining them (self-ligation). The insert retains phosphates for successful ligation.

Digestion of vector and insert with the same restriction enzyme

Dephosphorylation of vector DNA using alkaline phosphatase

• NADP (Nicotinamide Adenine Dinucleotide Phosphate) contains nicotinamide, a form of niacin (vitamin B3), as its key functional component in redox reactions.

• Glycolysis consumes 2 ATP in the preparatory phase (steps 1, 3) but produces 4 ATP via substrate-level phosphorylation in the payoff phase (steps 7, 10—twice per glucose).

• Flooded anaerobic conditions in rice paddies promote methanogenic archaea that decompose organic matter, releasing CH₄ as the dominant GHG (about 10-48% of agricultural methane)

• Domestic sewage contains high organic matter (food waste, feces, detergents) that microorganisms rapidly decompose, creating maximum oxygen demand—typically 200-600 mg/L

• Inulin consists primarily of fructose units linked by β(2→1) glycosidic bonds, typically with a terminal glucose residue, forming a fructan storage polysaccharide found in plants like chicory.

• ZIFT is an assisted reproductive technique where zygotes (fertilized eggs from IVF) are transferred laparoscopically into the fallopian tubes, unlike standard IVF which places them in the uterus

• Glycolysis, the initial breakdown of glucose into pyruvate, takes place in the cytoplasm of all cells, producing a net 2 ATP regardless of oxygen presence

(i) The volume of air that will remain in the lungs after a normal expiration is called residual volume. (FALSE)
Correction: This is actually the Functional Residual Capacity (FRC).

FRC is the sum of Expiratory Reserve Volume (ERV) and Residual Volume (RV).

Residual Volume (RV) is specifically the volume of air remaining in the lungs even after a forced (maximum) expiration. You can never truly empty your lungs of this air.

(ii) Volume of air inspired or expired during a normal respiration is called tidal volume. (TRUE)
Tidal Volume (TV) is the amount of air that moves in or out of the lungs during a quiet, relaxed breath.

In a healthy adult, this is approximately 500 mL.

(iii) The maximum volume of air a person can breathe in after a forced expiration is called vital capacity. (TRUE)
Vital Capacity (VC) represents the maximum amount of air a person can expel from the lungs after a maximum inhalation, or conversely, the maximum they can inhale after a forced exhalation.

• A hypothesis is a proposed, testable explanation based on observations, distinguishing it from conclusions (final results), generalizations (broad patterns from data), and predictions (expected outcomes from testing).

Project-based learning emphasizes hands-on application of knowledge through real-world projects, problem-solving, and practical skills development, which directly matches "Learning to do" – acquiring competence and mastering tools for work and life.

• The "products" of science are the results or the body of knowledge that has been accumulated through investigation. These are the fixed pieces of information we find in textbooks. They include:

Concepts: Mental constructs or categories (e.g., "gravity" or "mammal").

Laws: Descriptions of observed phenomena (e.g., Newton's Laws of Motion).

Theories: Explanations of how the natural world works (e.g., The Theory of Evolution).

Principles and Facts: Verified observations and fundamental truths.

• The First Bell initiative was launched by the Government of Kerala (specifically through KITE) as a comprehensive virtual class program to ensure that students from Classes 1 to 12 could continue their education during the COVID-19 pandemic.

• Validity confirms that a test accurately assesses the intended construct, content, or skill, not unrelated factors.

• Explaining the principle behind Kerala's unusual cold climate—such as weakened polar vortex, high pressure systems, clear skies causing radiational cooling, or northerly dry winds—requires using scientific concepts like atmospheric processes and weather patterns to interpret a real-world phenomenon. This matches the Application domain ("using and applying"), which emphasizes observing science concepts in daily life, solving related problems, and evaluating environmental events.

• Scaffolding. This teaching strategy involves providing temporary support, then fading it to promote independence, aligning directly with the described process.

In science education, process skills are typically divided into two categories: Basic and Integrated.

1. Basic Process Skills
These are the foundational "building blocks" of science. they provide the initial data and organization required for deeper study.

Observing (D): Using the five senses to gather information.

Classifying (A): Grouping objects or events based on similarities or differences.

Measuring (C): Using standard or non-standard measures to describe dimensions.

Inferring: Making an "educated guess" based on observations.

Predicting: Stating the outcome of a future event.

Communicating: Using words, symbols, or graphics to describe an action or object.

2. Integrated Process Skills
These are more complex and require the combination (integration) of several basic skills. They are used to conduct complete scientific investigations.

Experimenting (B): This is the ultimate integrated skill. It involves identifying variables, formulating hypotheses, controlling variables, and collecting/interpreting data.

Identifying Variables: Determining factors that can affect an outcome.

Formulating Hypotheses: Stating an expected relationship between variables.

Defining Operationally: Stating how to measure a variable in an experiment.

Interpreting Data: Organizing data and drawing conclusions from it.

Piaget. His theory emphasizes children actively constructing knowledge through assimilation and accommodation, forming the core of cognitive constructivism in education.

• To monitor student learning and provide ongoing feedback. This low-stakes process helps teachers adjust teaching in real-time and supports student growth, unlike end-of-term evaluations.

To monitor student learning and provide ongoing feedback

• Creativity domain. This domain (also called "Imaging and Creating") involves generating original ideas, designing solutions, fantasizing, and producing innovative approaches to real-world problems like waste reduction.

•  Learning to Be. This pillar focuses on holistic personal development, fostering self-awareness, judgment, autonomy, creativity, and reflection on personal values and potential.

• Biological sciences curriculum study. This refers to the influential 1950s U.S.-based project that revolutionized high school biology education through inquiry-based curricula (Blue, Green, Yellow versions), emphasizing themes like evolution and scientific processes.

• Achievement test. These summative assessments measure overall learning outcomes at the end of an instructional period to evaluate mastery and determine readiness for advancement or promotion.

• Utility principle. This principle ensures curriculum content is practical, relevant, and applicable to everyday life, social needs, and future challenges, maximizing its value for individuals and society

Analysing. This level involves deconstructing information to explore structures, relationships, and organizational principles, using verbs like differentiate, organize, and attribute.

Three language formula. This approach promotes mother tongue/regional language as the first, Hindi/English/other Indian language as the second (depending on region), and a third modern Indian or foreign language, fostering cognitive growth and national integration.

The NCF 2005 emphasizes that multilingualism is a resource and a strategy rather than a hurdle. The formula typically follows this structure:

First Language: The mother tongue or the regional language.

Second Language: In Hindi-speaking states, it could be English or another modern Indian language. In non-Hindi-speaking states, it is usually Hindi or English.

Third Language: In Hindi-speaking states, it is English or a modern Indian language not studied as the second language. In non-Hindi-speaking states, it is English or a modern Indian language not studied as the second language.

• It is tentative and subject to revision. Scientific knowledge evolves through empirical evidence, testing, and peer review; it is reliable yet open to modification, unlike fixed absolutes or authority-driven claims.

It is determined by the authority figures.

• (ii) Science is a process as well as product: Science involves ongoing inquiry (process) while producing reliable knowledge (product).
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(iv) Scientific knowledge is based on enquiry: Empirical observation, experimentation, and evidence drive scientific understanding.

 (ii) Science is a process as well as product. 

(iv) Scientific knowledge is based on enquiry.

• To prepare for holistic education. The pillars—Learning to Know, Do, Live Together, and Be—target complete human development, lifelong learning, creativity, values, and global citizenship beyond narrow academic or economic goals

To promote academic excellence and examination success

To Emphasize technological skills for economic growth

To Focusing on moral instruction and discipline training

• Analysis and Interpretation of Data. After collecting experimental results, this final step examines patterns, computes statistics, and determines if data supports, rejects, or modifies the hypothesis through comparison with predictions.

• Arranging content from easiest to difficult, considering cognitive readiness. This systematic organization follows Bloom's or Gagne's hierarchies, progressing from concrete/simple concepts (e.g., basic observation) to abstract/complex ones (e.g., hypothesis testing) to match learners' developmental stages.

Making students memorize content in particular order

Following the timetable strictly without flexibility

Arranging content from easiest to difficult, considering cognitive readiness

• Field trip. This hands-on method allows sensory engagement with authentic phenomena (e.g., observing ecosystems firsthand), surpassing indirect approaches like digital simulations or lectures.

• Helen Parkhurst. She created this progressive education model around 1919 in Dalton, Massachusetts, emphasizing student autonomy, individualized pacing, assignments, and laboratory-style learning over rigid class schedules.

• Ausubel. His meaningful learning theory (1960s) introduced advance organizers—introductory tools that link new content to prior knowledge, strengthening cognitive structures before main instruction.

• The National Council for Teacher Education (NCTE) is a statutory body established under the NCTE Act, 1993, specifically tasked with achieving planned and coordinated development of the teacher education system across India.

NCERT was established by the Government of India on 1 September 1961 as an autonomous organization to assist with policies for improving school education quality.

• The inductive teaching method involves students observing specific concrete examples, identifying patterns through close examination, and then forming general principles or rules.

• In educational testing and measurement, reliability refers to the degree to which an assessment tool produces stable and consistent results. If you were to give the same test to the same students under the same conditions, they should achieve similar scores.

• McCormack and Yager's taxonomy (1989) includes an attitudinal domain focused on developing positive feelings, values, interests, and dispositions toward science learning.

Remembering understanding and repeating information

Mastery of laboratory techniques and manipulative skills

Imagining designing and creative new constructs

Developing interest values and positive disposition towards science

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