Terrestrial and Aquatic Ecosystems MCQ Quiz - Objective Question with Answer for Terrestrial and Aquatic Ecosystems - Download Free PDF

The correct answer is 1, 2, and 3 only.

Key Points

Brackish water

• It is water that has more salinity than fresh water, but not as much as seawater.
• It may result from the mixing of seawater with fresh water, as in estuaries, or it may occur in brackish fossil aquifers.
• The word comes from the Middle Dutch root “brak”, meaning “salted” or “salty”.
• Certain human activities can produce brackish water, in particular certain civil engineering projects such as dikes and the flooding of coastal marshland to produce brackish water pools for freshwater prawn farming.
• It is also the primary waste product of the salinity gradient power process. Because brackish water is hostile to the growth of most terrestrial plant species, without appropriate management it is damaging to the environment.
• These water bodies have salt content between 5 to 35 ppt. e.g. estuaries, salt marshes, mangrove swamps and forests. Hence, Option 3 is correct.
• It is characteristic of many brackish surface waters that their salinity can vary considerably over space and/or time.
• Water on land that is continuously cycling and has low salt content (always less than 5 ppt) is known as freshwater.

The Correct Answer is one organism to another.
Key Points

• A food chain describes the way different organisms depend on one another for food.
• There are basically four levels to the food chain viz. producers, primary consumers, secondary consumers, and tertiary consumers.
• Autotrophs produce all of the available food.
• They make up the first trophic (feeding) level.
• They possess the highest biomass (the total weight of all the organisms in an area) and the greatest numbers.
• This is evident from the fact that plants make up around 99 percent of the earth’s total biomass.
• Primary consumers are organisms that directly feed on producers.
• The next level consists of organisms that feed on primary consumers.
• They are the secondary consumers, and they make up the third trophic level.
• They are called carnivores and omnivores.

The correct answer is Zooplankton.

Key Points

• A lake ecosystem is an aquatic food chain. It consists of different trophic levels.
  • The first trophic level is phytoplankton.
  • They produce their own food.
• Zooplankton is the primary consumer in aquatic food chains.
  • They feed upon phytoplankton. They are present in the second trophic level.
  • Hence, the second most important trophic level in a lake is zooplankton.
  • Small fishes feed upon zooplankton.
  • They are present in the third trophic level. Similarly, big fishes and other bigger aquatic animals are present in the fourth trophic level which feed upon small fishes.
• Thus, the correct answer is 'Zooplankton. 

The correct answer is Ecotone.

Key Points

• The area that acts as a boundary or a transition zone between two ecosystems is known as Ecotone.
• It may be narrow or wide, and it may be local (the zone between a field and forest) or regional (the transition between forest and grassland ecosystems).
•  An ecotone may appear on the ground as a gradual blending of the two communities across a broad area, or it may manifest itself as a sharp boundary line.
• The word ecotone was coined by Alfred Russel Wallace, who first observed the abrupt boundary between two biomes in 1859.

The correct answer is 2 only.

In News

• The National Conference on Promotion of Seaweed Cultivation was recently held at Koteshwar, Kutch, Gujarat. It aimed to expand seaweed farming across India to diversify marine production and enhance coastal livelihoods.

Key Points

• Statement 1: Incorrect. Seaweeds are not harmful. Instead, they are known for their medical, nutritional, and ecological benefits and are termed the "Medical Food of the 21st Century." Hence, Statement 1 is incorrect.
• Statement 2: Correct. Seaweeds serve as bio-indicators, absorbing excess nutrients like nitrates and phosphates and helping detect marine pollution caused by agricultural and industrial runoff. They also aid in restoring marine ecosystem balance. Hence, Statement 2 is correct.

Additional Information

• Seaweed farming supports women and small-scale fishers with minimal investment and quick returns.
• Key Indian species include Gelidiella acerosa, Gracilaria spp., Sargassum spp., etc.
• Commercial uses include food, pharmaceuticals, cosmetics, bioplastics, and carbon capture.
• The Seaweed Mission and Multi-Purpose Seaweed Park in Tamil Nadu are key initiatives promoting this sector.

Important Points

• An ecosystem is an interaction of biological community organisms between each other and their physical environment.
• The lithosphere is the outer part of the Earth it is made up of the crust and the top part of the upper mantle. 
• A biome is a large community of vegetation and wildlife which are adapted to a specific climate.
• The five major types of the biome are:
  • aquatic 
  • grassland 
  • forest 
  • desert
  • tundra

• The biosphere is the single largest ecosystem of the earth.
•  The biosphere is known as the sum of all ecosystems also known as the ecosystem also the zone of life on earth. 
• Biosphere is the sum of all and hence is regarded as the largest ecosystem of the earth.

The correct answer is Ecotone.

Key Points

• The area that acts as a boundary or a transition zone between two ecosystems is known as Ecotone.
• It may be narrow or wide, and it may be local (the zone between a field and forest) or regional (the transition between forest and grassland ecosystems).
•  An ecotone may appear on the ground as a gradual blending of the two communities across a broad area, or it may manifest itself as a sharp boundary line.
• The word ecotone was coined by Alfred Russel Wallace, who first observed the abrupt boundary between two biomes in 1859.

The correct answer is option 3 i.e., Forest

Key Points

• The ecosystem is completely dependent on solar radiation.
  • For eg. forests, oceans, grasslands, lakes, rivers, and deserts. 
  • This type of ecosystem is known as the Natural ecosystem.
• Man-made ecosystems are those ecosystems that are dependent on solar energy.
• For eg. agricultural fields and aquaculture ponds.
• Such ecosystems are also dependent on fossil fuels.
• For eg. urban and industrial ecosystems.
• An ecosystem is a community of living organisms in conjunction with the non-living components of their environment, interacting as a system.
• These biotic and abiotic components are linked together through nutrient cycles and energy flows.
• A forest ecosystem is a functional unit or a system that comprises soil, trees, insects, animals, birds, and man as its interacting units.

The correct answer is Zooplankton.

Key Points

• A lake ecosystem is an aquatic food chain. It consists of different trophic levels.
  • The first trophic level is phytoplankton.
  • They produce their own food.
• Zooplankton is the primary consumer in aquatic food chains.
  • They feed upon phytoplankton. They are present in the second trophic level.
  • Hence, the second most important trophic level in a lake is zooplankton.
  • Small fishes feed upon zooplankton.
  • They are present in the third trophic level. Similarly, big fishes and other bigger aquatic animals are present in the fourth trophic level which feed upon small fishes.
• Thus, the correct answer is 'Zooplankton. 

The correct answer is Always upright.

Key Points

• In most ecosystems, all the pyramids, of the number, of energy, and biomass are upright, i.e. producers are more in number and biomass than the herbivores, and herbivores are more in number and biomass than the carnivores.
  • Also, energy at a lower trophic level is always more than at a higher level.
  • However, there are exceptions to this generalization
    • The pyramid of biomass in the sea is generally inverted because the biomass of fishes far exceeds that of phytoplankton.

• A pyramid of energy is always upright, can never be inverted, because when energy flows from a particular trophic level to the next trophic level, some energy is always lost as heat at each step.
  • Each bar in the energy pyramid indicates the amount of energy present at each trophic level in a given time or annually per unit area.

The correct option is Photosynthesis.

Explanation:

Water cycle: The water from the ocean and surface of the earth goes into the air as vapour returns as rain, hail or snow and finally goes back to the oceans. The circulation of water in this manner is known as the water cycle.

• Evaporation, Transpiration, Condensation and Precipitation are the major process of the water cycle.

• The sun is the driving force behind the water cycle.

The precipitation comes down to the earth in liquid form is rainwater.

Additional Information

Photosynthesis: The leaves have a green pigment called chlorophyll. It helps leaves to capture the energy of the sunlight. This energy is used to synthesise (prepare) food from carbon dioxide and water. Since the synthesis of food occurs in the presence of sunlight, it is called photosynthesis.

• In the presence of sunlight Carbon dioxide + water → Carbohydrate + oxygen.
• Some plants, green algae, and cyanobacteria can perform photosynthesis.
• The process of photosynthesis is commonly written as

• 6CO2 + 6H2O + Sun-Light → C6H12O6 + 6O2

The correct answer is Phosphorus.

Phosphorus is most likely to limit primary production in freshwater lakes.

Key Points

• Primary production is the process of conversion of light energy to chemical energy by green plants. For the aquatic ecosystem, usually, phytoplankton does this work.
• In an ecosystem, the primary production sets the balance of the energy budget.
• The amount of light and nutrients limits primary production.
• A limiting nutrient is an element that must be added for production to increase in a particular area.
• In this case, two important nutrients are Nitrogen and Phosphorus that limit primary production.
• Nitrogen act as an agent for algae blooms in the sea/ocean water.
• In the case of freshwater, the major source of pollutants is derived through domestic sewage and agricultural fields.
• Phosphate content present in soap, phosphate fertilizers, concentrated animal feeding operations, etc causes extra addition of phosphorus in the freshwater.
• It predominantly causes Eutrophication.
• Eutrophication means  is characterized by dense algal and plant growth in the water that causes threats to the survival of aquatic life  
• Phosphorus is the nutrient that limited cyanobacteria growth.

The correct answer is Tropical rain forest.

Key Points

• Tropical rainforests are rainforests that occur in areas of tropical rainforest climate in which there is no dry season – all months have an average precipitation of at least 60 mm – and may also be referred to as lowland equatorial evergreen rainforest.
• A mangrove is a shrub or small tree that grows in coastal saline or brackish water.
  • The term is also used for tropical coastal vegetation consisting of such species.
  • Mangroves occur worldwide in the tropics and subtropics, mainly between latitudes 25° N and 25° S.
• Tropical Rainforests has the maximum bio-diversity among the given options.

Hint

• If one of the options was Corals, the answer would have been corals. 

Explanation:

Food Chain is a diagram that shows how food energy moves from one organism to another in a given environment. In other words, it is the chronological order of who eats whom in a biological community.

Aquatic food chain:

• Primary consumers are herbivores, they eat plants.
• In our aquatic ecosystem example, zooplankton feeding on phytoplankton occupy the primary consumer trophic level.

Phytoplankton →Zooplankton  → Small Fish → Large Fish → Whale

Phytoplankton: A mix of algae, the primary producer

Zooplankton: Small floating elements consuming the phytoplankton, the primary consumer

Hence the correct option is Zooplankton

The correct answer is Azolla.

Key Points Azolla:

• Azolla is considered a biofertilizer due to its ability to fix atmospheric nitrogen.
• The plant forms a symbiotic relationship with the nitrogen-fixing cyanobacterium Anabaena azollae, which is housed in specialized structures called "hairs" on the Azolla plant.
• During the growth of Azolla, the cyanobacteria fix atmospheric nitrogen and convert it into a usable form for plants.
• This nitrogen fixation process allows Azolla to accumulate a significant amount of nitrogen within its tissues.
• When Azolla is incorporated into the soil or water of rice fields, it releases the fixed nitrogen, making it available to the rice plants.
• This helps in reducing the dependence on synthetic nitrogen fertilizers for rice cultivation.
• In addition to nitrogen fixation, Azolla also contributes to the improvement of soil health.
• It acts as a green manure, enriching the soil with organic matter when it decomposes.
• Azolla's dense growth also shades the water surface, preventing weed growth and reducing water evaporation from the rice fields.

Additional Information

• Wolffia: Wolffia is a genus of tiny aquatic plants commonly known as "duckweeds" that float on the surface of still or slow-moving water bodies. They have the smallest flowering plants in the world.
• Lemna: Lemna is a genus of floating aquatic plants, also known as "duckweeds," that are found in freshwater environments. They reproduce rapidly and are known for their ability to cover the surface of water bodies.
• Trapa: Trapa is a genus of aquatic plants commonly known as "water chestnuts" or "water caltrops." They have floating leaves and produce edible fruits that resemble chestnuts.