Q.1 Which of the following is an abiotic component of an ecosystem?
Plants
Animals
Soil
Bacteria
Explanation - Abiotic components are non-living physical and chemical elements in the ecosystem, such as soil, water, air, and sunlight.
Correct answer is: Soil
Q.2 What term describes the maximum population size that an environment can sustain indefinitely?
Carrying capacity
Population density
Biotic potential
Ecological footprint
Explanation - Carrying capacity is the maximum number of individuals of a species that an environment can support sustainably.
Correct answer is: Carrying capacity
Q.3 Which process releases nitrogen from organic compounds back into the atmosphere?
Nitrification
Denitrification
Ammonification
Nitrogen fixation
Explanation - Denitrification is carried out by denitrifying bacteria, converting nitrates into nitrogen gas, releasing it back to the atmosphere.
Correct answer is: Denitrification
Q.4 Which of the following is a secondary consumer in a food chain?
Grasshopper
Rabbit
Frog
Grass
Explanation - Secondary consumers are organisms that feed on primary consumers; frogs eat insects, which are primary consumers.
Correct answer is: Frog
Q.5 The gradual replacement of one community by another in an ecosystem is called:
Succession
Competition
Predation
Symbiosis
Explanation - Ecological succession is the process in which the species structure of a community changes over time.
Correct answer is: Succession
Q.6 Which of the following gases is primarily responsible for the greenhouse effect?
Oxygen
Carbon dioxide
Nitrogen
Hydrogen
Explanation - Carbon dioxide traps heat in the atmosphere, contributing significantly to the greenhouse effect.
Correct answer is: Carbon dioxide
Q.7 Which biome is characterized by high rainfall and dense vegetation?
Desert
Grassland
Tropical rainforest
Tundra
Explanation - Tropical rainforests have high annual rainfall and support dense vegetation and high biodiversity.
Correct answer is: Tropical rainforest
Q.8 The role played by an organism in its ecosystem is called its:
Habitat
Niche
Population
Biome
Explanation - An ecological niche includes all the interactions and role of an organism within its ecosystem.
Correct answer is: Niche
Q.9 Which of the following is a density-independent factor affecting population?
Predation
Disease
Drought
Competition
Explanation - Density-independent factors affect populations regardless of their density; drought is an abiotic factor.
Correct answer is: Drought
Q.10 Biological magnification is the process by which:
Toxins increase in concentration up the food chain
Biodiversity increases
Water cycles through organisms
Energy decreases in food chains
Explanation - Pollutants like pesticides become more concentrated in higher trophic levels through biomagnification.
Correct answer is: Toxins increase in concentration up the food chain
Q.11 Which nutrient cycle does not have an atmospheric component?
Carbon cycle
Nitrogen cycle
Phosphorus cycle
Sulfur cycle
Explanation - The phosphorus cycle primarily occurs through rocks, soil, and water, with no significant atmospheric phase.
Correct answer is: Phosphorus cycle
Q.12 Which of the following organisms is a keystone species?
Lion in savanna
Grass in a meadow
Rabbit in forest
Algae in ocean
Explanation - Keystone species have a disproportionately large effect on their ecosystem relative to their abundance.
Correct answer is: Lion in savanna
Q.13 Which human activity contributes most to the increase of CO2 in the atmosphere?
Deforestation
Afforestation
Crop rotation
Organic farming
Explanation - Cutting down forests reduces CO2 absorption, increasing atmospheric carbon dioxide.
Correct answer is: Deforestation
Q.14 Which term describes organisms that can live in extreme environmental conditions?
Mesophiles
Extremophiles
Thermophiles
Halophiles
Explanation - Extremophiles are organisms adapted to extreme temperatures, salinity, acidity, or pressure.
Correct answer is: Extremophiles
Q.15 Which of the following is a primary producer in an ecosystem?
Fungi
Grass
Lion
Snake
Explanation - Primary producers, like plants, produce their own food through photosynthesis and form the base of the food chain.
Correct answer is: Grass
Q.16 Which gas is released during the process of photosynthesis?
Oxygen
Carbon dioxide
Nitrogen
Methane
Explanation - Photosynthesis converts carbon dioxide and water into glucose and oxygen using sunlight.
Correct answer is: Oxygen
Q.17 What is the main cause of eutrophication in water bodies?
Excess nitrogen and phosphorus
Excess oxygen
Decrease in sunlight
Increase in fish population
Explanation - Runoff of fertilizers leads to nutrient enrichment, causing excessive algal growth and oxygen depletion.
Correct answer is: Excess nitrogen and phosphorus
Q.18 The ozone layer is important because it:
Absorbs UV radiation
Produces oxygen
Reduces CO2 levels
Reflects visible light
Explanation - The ozone layer in the stratosphere protects life on Earth by absorbing harmful ultraviolet radiation from the sun.
Correct answer is: Absorbs UV radiation
Q.19 In a climax community, the ecosystem is:
Highly stable
In early succession
Under constant change
Always aquatic
Explanation - A climax community represents a mature, stable ecosystem with minimal changes over time.
Correct answer is: Highly stable
Q.20 Which type of interaction is shown when one species benefits and the other is neither helped nor harmed?
Mutualism
Commensalism
Parasitism
Competition
Explanation - Commensalism benefits one species without affecting the other, e.g., barnacles on whales.
Correct answer is: Commensalism
Q.21 Biomes are primarily classified based on:
Vegetation type and climate
Latitude only
Altitude only
Animal species only
Explanation - Biomes are large ecological areas classified by climate, soil, and predominant vegetation.
Correct answer is: Vegetation type and climate
Q.22 Which of the following is a consequence of acid rain?
Soil nutrient depletion
Increase in biodiversity
Increase in pH
Formation of ozone layer
Explanation - Acid rain lowers soil pH, depletes nutrients, and harms aquatic and terrestrial ecosystems.
Correct answer is: Soil nutrient depletion
Q.23 Which is the largest carbon reservoir in the carbon cycle?
Atmosphere
Oceans
Fossil fuels
Soil
Explanation - Oceans store the largest amount of carbon, both as dissolved CO2 and in marine organisms.
Correct answer is: Oceans
Q.24 Which type of succession occurs in an area devoid of soil?
Primary succession
Secondary succession
Climax succession
Allogenic succession
Explanation - Primary succession begins in lifeless areas where there is no soil, e.g., bare rocks after volcanic eruptions.
Correct answer is: Primary succession