Question 81:
Which of the following pollutants causes “eutrophication” in water bodies?
(A) Pesticides
(B) Nitrates and phosphates
(C) Sulfur dioxide
(D) Carbon monoxide
Answer: (B) Nitrates and phosphates
Explanation:
Eutrophication is caused by the excessive input of nutrients like nitrates and phosphates into water bodies, leading to algal blooms. This depletes oxygen in the water, harming aquatic life.
Question 82:
Which of the following statements is true regarding the ozone layer?
(A) It absorbs harmful infrared radiation from the sun
(B) It is found in the troposphere
(C) It protects the Earth from harmful ultraviolet (UV) radiation
(D) It is being depleted by carbon dioxide emissions
Answer: (C) It protects the Earth from harmful ultraviolet (UV) radiation
Explanation:
The ozone layer, located in the stratosphere, absorbs most of the sun’s harmful ultraviolet (UV) radiation, protecting living organisms on Earth from its damaging effects. The ozone layer is primarily being depleted by chlorofluorocarbons (CFCs), not CO₂ emissions.
Question 83:
In an aquatic ecosystem, the base of the food web consists of:
(A) Zooplankton
(B) Small fish
(C) Phytoplankton
(D) Crustaceans
Answer: (C) Phytoplankton
Explanation:
Phytoplankton are the primary producers in aquatic ecosystems, forming the base of the food web. They produce energy through photosynthesis and support the higher trophic levels, including zooplankton, fish, and other aquatic organisms.
Question 84:
Which of the following organisms would most likely occupy the highest trophic level in a food chain?
(A) Grass
(B) Insects
(C) Deer
(D) Lion
Answer: (D) Lion
Explanation:
Lions are apex predators, occupying the highest trophic level in a food chain. They are tertiary consumers that feed on primary and secondary consumers, such as herbivores like deer.
Question 85:
Which of the following pollutants is primarily responsible for acid rain?
(A) Carbon dioxide
(B) Nitrogen oxides and sulfur dioxide
(C) Methane
(D) Ozone
Answer: (B) Nitrogen oxides and sulfur dioxide
Explanation:
Acid rain is caused by the release of nitrogen oxides (NOx) and sulfur dioxide (SO₂) into the atmosphere. These gases react with water vapor to form nitric acid and sulfuric acid, which then fall as acid rain, damaging ecosystems.
Question 86:
In the process of biomagnification, which of the following substances is most likely to accumulate in the highest concentration at the top of the food chain?
(A) Water
(B) Oxygen
(C) Pesticides like DDT
(D) Carbon dioxide
Answer: (C) Pesticides like DDT
Explanation:
Biomagnification is the process where toxic substances like pesticides (e.g., DDT) accumulate in increasing concentrations at each trophic level of a food chain. Top predators accumulate the highest concentrations of these harmful substances.
Question 87:
Which of the following ecosystems has the lowest net primary productivity (NPP)?
(A) Desert
(B) Tropical rainforest
(C) Coral reef
(D) Grassland
Answer: (A) Desert
Explanation:
Deserts have the lowest net primary productivity due to the scarcity of water and limited vegetation. Tropical rainforests and coral reefs have high NPP due to abundant resources and favorable environmental conditions.
Question 88:
Which of the following organisms is an example of a primary producer?
(A) Grass
(B) Rabbit
(C) Fox
(D) Earthworm
Answer: (A) Grass
Explanation:
Primary producers, like grass, use photosynthesis to convert sunlight into energy, forming the base of the food chain. Rabbits are primary consumers, foxes are secondary consumers, and earthworms are decomposers.
Question 89:
Which of the following is an example of a renewable resource?
(A) Natural gas
(B) Coal
(C) Wind energy
(D) Petroleum
Answer: (C) Wind energy
Explanation:
Wind energy is a renewable resource because it is continuously replenished by natural processes. In contrast, natural gas, coal, and petroleum are non-renewable resources, as they take millions of years to form and are depleted faster than they can be replaced.
Question 90:
The term “ecological footprint” refers to:
(A) The impact of human activity on ecosystems
(B) The area of land needed to support a population’s resource use and waste generation
(C) The total amount of energy consumed by a community
(D) The biological productivity of an ecosystem
Answer: (B) The area of land needed to support a population’s resource use and waste generation
Explanation:
An ecological footprint measures the amount of land and water required to support a person or population’s consumption of resources and absorption of waste. It helps assess the sustainability of resource use.
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