Test: Class 7 General Science NCERT Based - 1(UPSC Level) - UPSC MCQ

1. Autotrophic Nutrition: Correctly matched. Plants indeed prepare their own food using sunlight, carbon dioxide, and water, a process known as photosynthesis. This is the defining characteristic of autotrophs, which are the producers in the ecosystem.

2. Herbivores: Incorrectly matched. Herbivores derive energy directly from plants, not animals. They are organisms that feed on plants or plant products.

3. Carnivores: Correctly matched. Carnivores derive energy by eating herbivores or other animals. They are secondary consumers in the food chain.

4. Decomposers: Correctly matched. Decomposers, such as certain bacteria and fungi, break down dead organic material to obtain nutrients. They play a crucial role in recycling nutrients in ecosystems.

In conclusion, pairs 1, 3, and 4 are correctly matched, while pair 2 is not. Hence, the correct answer is Option C

Chemical changes involve the formation of new substances. During a chemical change, the chemical composition of the substance changes, resulting in the formation of one or more new substances. This distinguishes chemical changes from physical changes, where the composition remains the same despite alterations in properties like shape, size, or state. Chemical changes are often accompanied by observable signs such as the release of heat or light, color changes, or the formation of precipitates.

1. Sandy soil → High water holding capacity: Incorrect. Sandy soil has the least water holding capacity due to its larger particle size and higher permeability.

2. Clayey soil → Used for making pots: Correct. Clayey soil is used for making toys, pots, and statues due to its fine particles and plasticity when wet.

3. Loamy soil → Best for plant growth: Correct. Loamy soil, being a mixture of sand, silt, and clay, is ideal for plant growth due to its balanced texture, nutrient content, and water retention.

4. Sandy-loam soil → Used mainly for paddy cultivation: Incorrect. Paddy is usually grown in clayey soil as it can retain water well, which is essential for rice cultivation.

Pairs 2 and 3 are correctly matched.

Statement-I correctly describes the characteristics and benefits of loamy soil, emphasizing its suitability for plant growth due to its composition and water holding capacity. On the other hand, Statement-II incorrectly associates clayey soil with being the most appropriate for paddy cultivation. While clayey soil does hold water well, it is not the best choice for paddy cultivation, as paddy typically thrives in flooded conditions, which are better provided by other types of soil.

1. Loamy soil is considered the best for plant growth because it has a balanced mixture of sand, clay, and silt, providing optimal water retention and aeration.

This statement is correct. Loamy soil is known for its ideal properties for plant growth. It contains a balanced mix of different soil particles, which allows it to hold water well while also providing good drainage and aeration.

2. The percolation rate of water is highest in clayey soil due to its tightly packed particles.

This statement is incorrect. The percolation rate of water is actually highest in sandy soil, not clayey soil. Sandy soil has larger particles with more space between them, which allows water to drain quickly. Clayey soil, on the other hand, has small, tightly packed particles that hold water, resulting in a slower percolation rate.

3. Humus, an important component of soil, is primarily made up of minerals and weathered rock particles.

This statement is incorrect. Humus is primarily composed of decomposed organic matter, not minerals and weathered rock particles. It is a crucial component of soil that enriches it with nutrients necessary for plant growth.

Therefore, only statement 1 is correct, making Option A: 1 Only the right choice.

- Statement 1 is correct. Protein digestion indeed begins in the stomach where the enzyme pepsin breaks down proteins into smaller peptides, known as polypeptides. The stomach provides an acidic environment, which is essential for pepsin activity.

- Statement 2 is incorrect. While the liver secretes bile juice, the role of bile is to emulsify fats, not to break down proteins. It aids in the digestion and absorption of fats by increasing the surface area for the action of lipases. Proteins are broken down into amino acids through the action of enzymes such as peptidases, not bile.

- Statement 3 is correct. Villi are small, finger-like projections in the lining of the small intestine. They increase the surface area for absorption, allowing for more efficient uptake of nutrients, including carbohydrates, proteins, and fats, from the digested food into the bloodstream.

Thus, the correct statements are 1 and 3, making Option C: 1 and 3 Only the correct answer.

1. Burning of Magnesium Ribbon: This is a chemical change. When magnesium burns, it reacts with oxygen to form magnesium oxide, a new substance. The pair is incorrectly matched.

2. Dissolving magnesium ash in water: This is a chemical change. Magnesium oxide reacts with water to form magnesium hydroxide, a new substance. The pair is correctly matched.

3. Rusting of Iron: This is a chemical change. Rusting involves iron reacting with oxygen and water to form iron oxide, a new substance. The pair is correctly matched.

4. Melting of Ice: This is a physical change. When ice melts, it changes state from solid to liquid without changing its chemical composition. The pair is incorrectly matched.

The correctly matched pairs are 2 and 3. Therefore, only two pairs are correctly matched.

Teeth play a crucial role in the process of nutrition by aiding in the mechanical breakdown of food. Specifically, molars and premolars are responsible for chewing and grinding food into smaller particles, making it easier for further digestion. Canines are used for piercing and tearing food while incisors are for cutting and biting. This initial breakdown of food by teeth is essential for the subsequent stages of digestion and absorption in the body.

Statement-I suggests that dark surfaces absorb more heat and are preferred in winter. This is an incorrect statement. Dark surfaces absorb more heat, hence wearing dark colored clothes in summer would make one feel hotter, not comfortable in winter. Statement-II correctly explains that light-colored clothes reflect heat, making them more suitable for summer. Light colors are indeed preferred in summer to stay cool. Thus, Statement-II is correct, while Statement-I is incorrect, making option (d) the correct answer.

- Statement 1: Incorrect. Burning magnesium ribbon is a chemical change, not a physical one. It reacts with oxygen to form magnesium oxide, a new substance.
- Statement 2: Correct. Rusting of iron involves forming iron oxide, which is a chemical change as it results in new substances.
- Statement 3: Incorrect. Dissolving magnesium oxide in water forms magnesium hydroxide, which is not easily reversible as it involves a chemical reaction.

Thus, only statement 2 is correct. The correct answer is B: 2 Only.

1. Statement 1: Linear motion is a type of motion where an object travels along a straight path.
This statement is correct. Linear motion, also known as straight-line motion, involves movement along a straight path. Examples include an object sliding down a slope or a car moving on a straight road.

2. Statement 2: A pendulum's motion is categorized under curvilinear motion.
This statement is incorrect. A pendulum exhibits oscillatory motion, not curvilinear motion. Oscillatory motion is to-and-fro motion about a mean position, such as the swinging of a pendulum. Curvilinear motion refers to motion along a curved path but not specifically to repetitive to-and-fro motion.

3. Statement 3: The time taken by a pendulum to complete one oscillation is known as its speed.
This statement is incorrect. The time taken by a pendulum to complete one oscillation is termed its "time period," not speed. Speed refers to how fast an object is moving, calculated as distance covered per unit time, whereas the time period is the duration for one complete cycle of motion.

Therefore, the only correct statement is 1, and the correct answer is Option A: 1 Only.

The basic unit of speed is meter per second (m/sec). Speed is defined as the distance traveled by an object in a unit of time. It helps us determine which object is moving faster than the other. When calculating speed, it is typically represented as distance traveled divided by the time taken. In the context of motion and time, understanding the basic unit of speed, which is meter per second, is crucial for various calculations and measurements related to motion.

Both Statement-I and Statement-II are factually correct. Statement-I defines motion as the change in position of an object with time, which is a fundamental concept in physics. Statement-II correctly describes the concept of speed as the distance traveled by an object in a unit of time. However, Statement-II does not explain Statement-I. While speed is related to motion, it does not directly explain the definition of motion provided in Statement-I. Speed is a measurement associated with motion but does not encompass the entirety of what motion entails. Thus, Option B is the most appropriate answer as both statements are correct but are not interdependent in terms of explanation.

1. Statement 1: Correct. Photosynthesis is the process by which green plants synthesize food using carbon dioxide and water in the presence of sunlight, facilitated by chlorophyll. Minerals are absorbed from the soil to assist in various physiological processes, but they are not directly required for the synthesis of carbohydrates during photosynthesis. However, the essential raw materials explicitly required are carbon dioxide, water, sunlight, and chlorophyll.

2. Statement 2: Correct. Stomata are small openings on the surface of leaves that allow for the exchange of gases, including the absorption of carbon dioxide necessary for photosynthesis.

3. Statement 3: Incorrect. While chlorophyll is indeed responsible for trapping solar energy, it is used to synthesize carbohydrates, not proteins, from carbon dioxide and water. The primary product of photosynthesis is glucose, a carbohydrate, and oxygen as a byproduct.

Therefore, the correct statements are 1 and 2. Hence, the answer is Option B: 1 and 2 Only.

Both Statement-I and Statement-II are correct. Statement-II explains Statement-I. Statement-I highlights the process of plants preparing their own food through photosynthesis using water, carbon dioxide, and minerals. Statement-II elaborates on the role of chlorophyll in trapping solar energy essential for converting CO2 and water into food. Chlorophyll absorbs sunlight, initiating the photosynthesis process, making the sun the primary energy source for this food production. Hence, both statements are accurate, with Statement-II providing a complementary explanation to Statement-I.

1. Molars - Piercing and tearing food: Incorrect. Molars are primarily used for chewing and grinding food, not for piercing and tearing. Canines are responsible for piercing and tearing food.

2. Bile Juice - Digestion of carbohydrates: Incorrect. Bile juice is primarily involved in the digestion of fats by emulsifying them; it does not directly digest carbohydrates.

3. Villi - Increase surface area for absorption: Correct. Villi are small, finger-like projections in the small intestine that increase the surface area for absorption of nutrients.

4. Pepsin - Breaks proteins into polypeptides: Correct. Pepsin is an enzyme that breaks down proteins into smaller units called polypeptides in the stomach.

Thus, only pairs 3 and 4 are correctly matched.

In a physical change, the chemical composition of a substance remains the same, indicating that Statement-I is correct. Additionally, most physical changes are reversible, which aligns with Statement-II. When a substance undergoes a physical change, such as melting or boiling, its molecules do not change; they simply rearrange or change their state. This explanation supports why both statements are correct and why Statement-II logically explains Statement-I.

The normal temperature of the human body is 37°C. This is the average temperature that is considered typical for a healthy human body. It's important to note that body temperature can vary slightly among individuals but generally falls within this range.

1. Linear Motion: Object moves in a curve - Incorrect. Linear motion refers to the movement of an object along a straight line, not a curve.

2. Oscillatory Motion: Motion of a pendulum to and fro - Correct. Oscillatory motion is accurately described as the to-and-fro movement of a pendulum.

3. Speedometer: Measures distance travelled by vehicle - Incorrect. A speedometer measures the speed of a vehicle, not the distance. The device that measures distance is called an odometer.

4. Pendulum Clock: Uses periodic motion to measure time - Correct. Pendulum clocks indeed use the periodic motion of a pendulum to keep time accurately.

Pairs 2 and 4 are correctly matched, making Option B the correct answer.

Plants utilize a process called photosynthesis to create their own food. During photosynthesis, plants use sunlight, water, and carbon dioxide to produce glucose (a form of sugar) and oxygen. This process mainly occurs in the chloroplasts of plant cells, specifically in the chlorophyll-containing cells of leaves. This vital process not only provides energy for the plant but also plays a crucial role in the Earth's ecosystem by producing oxygen as a byproduct, which is essential for many organisms' survival.