Class 10 – Science Extra Questions – Ch. 13 – Our Environment

Ans: C

Explanation: A natural ecosystem is a community of living organisms interacting with their physical environment, which has developed and functions without significant human intervention. An aquarium is a man-made environment for aquatic life. A garden is a cultivated area of land, typically for growing plants. A zoo is a place where animals are kept for public exhibition. An ocean, however, is a vast, self-regulating body of water with diverse life forms and chemical and physical processes that have evolved naturally over millions of years.
Correct Option: C

Ans: C

Explanation: Primary consumers are herbivores, meaning they feed on producers. In a grassland ecosystem, grass is a producer. A rabbit is a herbivore that feeds on grass, making it a primary consumer. A lion is a carnivore that feeds on other animals, making it a secondary or tertiary consumer. A snake is typically a carnivore or insectivore, making it a secondary consumer. Therefore, the rabbit is the primary consumer.
Correct Option: C

Ans: D

Explanation: Abiotic factors are the non-living physical and chemical elements of an environment that affect the survival, distribution, and evolution of living organisms. Examples in a forest ecosystem include sunlight, temperature, water, soil composition, and air. Biotic factors, on the other hand, are the living or once-living components of an ecosystem, such as plants, animals, fungi, and bacteria. Biomass refers to the total mass of organisms in a given area or volume. Biodiversity is the variety of life in a particular habitat or ecosystem. Therefore, the non-living components are abiotic factors.
Correct Option: D

Ans: C

Explanation: In an ecosystem, energy originates primarily from the sun. Producers, such as plants and algae, capture this solar energy through photosynthesis and convert it into chemical energy in the form of organic compounds. Consumers then obtain energy by eating producers or other consumers. Decomposers break down dead organic matter from producers and consumers, releasing nutrients back into the ecosystem, but they do not form the primary flow of energy from their trophic level. Therefore, the fundamental flow of energy is from producers to consumers.
Correct Option: C

Ans: C

Explanation: The question describes the study of materials at the nanoscale (1-100 nanometers) and the emergence of unique properties at this scale. This is the defining characteristic of nanotechnology. Astronomy studies celestial objects, biology studies living organisms, and geology studies the Earth’s physical structure and substance.
Correct Option: C

Ans: C

Explanation: Biomass and available energy decrease at each successive trophic level. Producers form the base of the food web and convert solar energy into chemical energy through photosynthesis, thus containing the largest amount of biomass and energy. Primary consumers feed on producers, secondary consumers feed on primary consumers, and tertiary consumers feed on secondary consumers. Each level loses a significant portion of energy as heat during metabolic processes.
Correct Option: C

Ans: D

Explanation: In an ecosystem, producers are organisms that create their own food (like plants). Organisms that eat producers are called primary consumers (herbivores). Secondary consumers eat primary consumers, and tertiary consumers eat secondary consumers. Decomposers break down dead organic matter. Therefore, organisms that consume producers are primary consumers.
Correct Option: D

Ans: C

Explanation: Producers form the base of every food chain. They convert light energy into chemical energy through photosynthesis. All other organisms in an ecosystem, directly or indirectly, depend on producers for energy. If producers are eliminated, the primary consumers (herbivores) will lose their food source. This will lead to starvation and a rapid decline in their populations, not an increase. Decomposers rely on dead organic matter from all trophic levels, so their activity will eventually decrease, but this is not the *most immediate* consequence and would follow the decline of consumers. While the entire ecosystem will eventually collapse, the immediate and most significant impact will be on the primary consumers who directly rely on producers. Option D describes a temporary surge, which is unlikely; the immediate effect would be a loss of food, leading to a decline. Therefore, the elimination of producers causes a cascading effect, and the most immediate and significant consequence is the impact on the organisms that directly consume them.

Correct Option: C

Ans: D

Explanation: In a food chain, organisms are interconnected. Deer are herbivores and eat grass. Tigers are carnivores and eat deer. If deer are removed, there will be less food for the tigers, causing their population to decrease. With fewer deer, the grass population will have less predation and is likely to increase. Therefore, the population of tigers decreases and the population of grass increases.
Correct Option: D

Ans: A

Explanation: Nanoparticles have a significantly larger surface area relative to their volume compared to bulk materials. This increased surface area means that a greater proportion of atoms are on the surface, leading to more surface-dependent interactions and thus altered chemical, physical, and optical properties. For example, catalytic activity is often enhanced because the reaction occurs on the surface. Increased density is not a general characteristic of nanoparticles. Reduced reactivity with common solvents is also not a universal property; often, nanoparticles are *more* reactive due to their surface area. Their interaction with electromagnetic radiation is also significantly altered, not absent.
Correct Option: A