Ecosystem MCQ Quiz - Objective Question with Answer for Ecosystem - Download Free PDF

Key Points

• In many aquatic ecosystems, the biomass pyramid is inverted due to the high turnover rate of primary producers.
• Phytoplankton, the primary producers in aquatic ecosystems, reproduce rapidly and have a short lifespan, creating a small biomass.
• Zooplankton and other primary consumers can have a larger biomass than the phytoplankton they consume, resulting in an inverted pyramid.
• This inversion is typical in aquatic environments where the energy flow is high but the standing biomass of primary producers is low.

Additional Information

• Biomass Pyramid
  • A biomass pyramid is a graphical representation that shows the relative amounts of biomass at different trophic levels in an ecosystem.
  • Biomass is the total mass of living matter in a given area or volume.
  • In most terrestrial ecosystems, the biomass pyramid is upright, with a large biomass of primary producers supporting smaller biomasses of higher trophic levels.
• Phytoplankton
  • Phytoplankton are microscopic marine algae that are the primary producers in many aquatic ecosystems.
  • They undergo rapid reproduction cycles and are consumed quickly by primary consumers like zooplankton.
• Zooplankton
  • Zooplankton are small, often microscopic animals that drift in water columns and consume phytoplankton.
  • They form the second trophic level in aquatic food chains and can have a larger biomass than phytoplankton due to their longer lifespans and slower reproduction rates.
• Energy Flow in Ecosystems
  • Energy flow in ecosystems follows a unidirectional path from primary producers to various levels of consumers.
  • While energy decreases at each trophic level due to metabolic processes, the biomass at each level can vary, leading to different pyramid shapes.

The correct answer is An ecosystem.

Key Points

• ​Here is a brief explanation about an ecosystem:
• Interaction of Life and Non-Life:
  • ​An ecosystem is a community of living organisms (plants, animals, microbes) interacting amongst themselves and with their non-living surroundings (atmosphere, earth, sun, soil, climate).
• Energy Flow:
  • ​The ecosystem is characterized by the flow of energy and matter through food chains and food webs.
  • It starts with the energy from the sun being captured by plants in the process of photosynthesis.
• Nutrient Cycling:
  • ​In an ecosystem, nutrients are cycled through various living and non-living components.
  • This involves processes like decomposition and nutrient absorption by plants.
• Different Types:
  • ​Ecosystems can vary widely in size and characteristics, from a small pond to a large forest or even an entire biome such as a desert or tundra.
• Balance:
  • ​Ecosystems inherently maintain a balance between different species and resources.
  • However, human intervention or natural disasters can disrupt this balance, affecting the entire ecosystem's functionality.
• Here is a simple illustrating the structure of an ecosystem:

The correct answer is Mixture of grain and husk.

Concept:
Separation of substances

• Substances are separated from the mixture in process of removing impurities or obtaining useful substances out of the mixture. 
• Some common examples of separations include the separation of salt from seawater, butter from milk, grain from stalks, etc.
• Different methods of separations are handpicking, threshing, winnowing, and sieving.

Explanation:
Winnowing:

• Winnowing is used to separate heavier and lighter components of a mixture by wind or by blowing air.
• This method is commonly used by farmers to separate lighter husk particles from heavier seeds of grain. 
• The husk particles from the grain are carried away by the wind or by blowing air. 
• The seeds of grain get separated and form a heap near the platform for winnowing. 
• The separated husk is used for many purposes such as fodder for cattles.

Additional Information

Handpicking:

• The method of handpicking is used to separate undesirable substances such as small pieces of stones from wheat, and rice.
• The quantity of such impurities is usually not very large.
• In such situations, we find that handpicking is a convenient method of separating substances.
• Some common examples are the Separation of pebbles from grain, and the Separation of pebbles from wet sand, etc.

Threshing:

• The process that is used to separate the grain from stalks etc. is threshing. 
• In this process, the stalks are beaten to free the grain seeds.
• Sometimes, threshing is done with the help of bullocks. 
• Machines are also used to thresh large quantities of grain.

Sieving:

• Sieving allows the fine flour particles to pass through the holes of the sieve while the bigger impurities remain on the sieve.
• In a flour mill, impurities like husk and stones are removed from wheat before grinding it.
• Usually, a bagful of wheat is poured into a slanting sieve.
• The sieving removes pieces of stones, stalk, and husk that may still remain with wheat after threshing and winnowing.

The correct answer is Very low.

Key Points

• The biomass in higher trophic levels (e.g., carnivores) is less than in lower trophic levels (e.g., plants).
• This phenomenon is due to energy loss at each trophic level as energy is transferred.
• Only about 10% of the energy is transferred from one trophic level to the next; the rest is lost primarily through metabolic processes.
• The pyramid of biomass typically shows a decreasing trend from primary producers to apex predators.
• This decrease in biomass is a direct result of the second law of thermodynamics which states that energy transformations are not 100% efficient.

Additional Information

• Trophic Levels:
  • Each step in a food chain or food web is called a trophic level.
  • Primary producers (e.g., plants) occupy the first trophic level.
  • Herbivores, which eat plants, occupy the second trophic level.
  • Carnivores that eat herbivores occupy the third trophic level, and so on.
• Energy Transfer Efficiency:
  • Energy transfer between trophic levels is typically around 10%, known as the 10% law.
  • 90% of the energy is lost to the environment as heat, movement, or undigested food.
• Pyramid of Biomass:
  • It is a graphical representation showing the relative biomass at each trophic level.
  • The pyramid typically narrows at higher trophic levels.
  • The biomass of primary producers is the highest, followed by primary consumers, secondary consumers, and so forth.
• Second Law of Thermodynamics:
  • This law states that energy transformations are not 100% efficient.
  • In an ecosystem, this inefficiency is observed as energy is lost as heat at each trophic level transfer.

The correct answer is 1-C, 2-A, 3-B.

Key Points

• Pioneer Communities: First organisms to colonize an area, primarily lichens and mosses.
• Climax Communities: Stable and final stage of ecological succession, typically a forest.
• Seral Communities: Intermediate stages in succession, including shrubs and herbaceous plants.

Additional Information

• Pioneer Species: Species that colonize barren or disturbed ecosystems, initiating ecological succession.
• Ecological Succession: The process by which ecosystems develop and change over time, divided into primary (starting from bare rock) and secondary (after disturbance) succession.
• Climax Ecosystem: A stable, mature ecosystem where species composition remains relatively unchanged over time unless disrupted by environmental factors.
• Seral Stages: Transitional stages between the pioneer and climax communities, which may involve different plant and animal species.
• Types of Succession: Primary succession occurs on previously uninhabited surfaces, while secondary succession happens after disturbances such as fire or deforestation.

The correct answer is "Herbivores".

Key Points

• In a food chain, secondary producers are herbivores.
• Herbivores are those organisms that feed on trees, plants, and fruits.
• It is food for a predator.
• Secondary producers are also consumers.
• Most herbivores have wide flat teeth that help them to grind grass, tree parts, etc.

 Additional Information

• Food chain - It is an order of events occurring in the ecosystem, it shows one living organism eating another.
• The food chain consists of :
  • Producers
  • Primary consumers
  • Secondary consumers
  • Tertiary consumers
• The producers
  • are the ones that produce food. 
  • these include all the autotrophs, like phytoplankton, green plants, etc.
• Consumers
  • these are dependent on other organisms or plants for food.
  • includes herbivores, carnivores, etc.
• Omnivores - Organisms that eat both plants and animals.
• Carnivores - Organisms that eat animals.
• Decomposers - These feed on dead and decaying things.

The correct answer is zooplankton.

Key Points

• Although there may be some fish that consume phytoplanktons, the main consumers in a lake environment are zooplanktons. Zooplankton is thus the dominant second trophic level in a lake environment.
• The majority of zooplankton species are tiny, microscopic organisms. a single-celled protist that primarily consumes bacteria, for instance. Nonetheless, some zooplankton species can grow fairly large such as jellyfish, arrow worms, etc.
• They are the main consumers because they consume producers like phytoplankton, which are then consumed by small fish (secondary consumers).

Additional Information

•  Food Chain
  • A food chain demonstrates the relationship of feeding between several creatures in a specific habitat or ecosystem.
  • The energy flow from the sun to producers, from producers to consumers, and from consumers to decomposers like fungi is demonstrated by a food chain.
  • They also demonstrate how animals rely on other living things for nourishment.

The correct answer is i - b, ii - c, iii - d, iv - a.

Key Points

The trophic levels represent the hierarchical levels in an ecological food chain, indicating the position of organisms based on their feeding relationships. Here's the explanation for the correct match:

• First trophic level - phytoplankton:
  • The first trophic level typically consists of primary producers that convert sunlight into energy through photosynthesis.
  • Phytoplankton are microscopic plants that form the base of aquatic food chains.
• Second trophic level - zooplankton:
  • The second trophic level comprises primary consumers that feed on the primary producers.
  • Zooplankton, which includes tiny animals, consume phytoplankton, placing them at the second trophic level.
• Third trophic level - fishes:
  • The third trophic level involves secondary consumers that feed on primary consumers.
  • In aquatic ecosystems, fishes are often positioned at the third trophic level as they consume zooplankton or other smaller organisms.
• Fourth trophic level - human:
  • The fourth trophic level represents tertiary consumers, which are higher-order predators.
  • Humans, being omnivores or carnivores, are often placed at the fourth trophic level in food chains when they consume animals from lower trophic levels.​ 

Explanation:

The correct option is Energy.

An ecological pyramid is a pictorial representation of the relationship between different organisms in an ecosystem.

Pyramid of numbers:

• It depicts the numbers of individual organisms at different trophic levels of the food chain.
• It is helpful to calculate the changes observed in the number of organisms in each trophic level.
• We can identify which level is in the endangered zone and need to be saved. But its limitation is we cannot count a number of all organisms accurately.

Pyramid of Biomass:

• Biomass is the dry weight of the organism.
• Pyramid of biomass indicates a decrease of biomass in each tropical level from base to apex.
• With higher tropical level biomass decreases for ecosystem on land and its inverse for an aquatic ecosystem where biomass increases with higher trophic level.

Pyramid of Energy:

An energy pyramid shows how much energy is needed as it flows upwards to support the next trophic level. Here the pyramid is always upward.

Hence, Pyramid of energy is the correct option.

Key Points

• Food chain - is a linear sequence of flow of energy takes place between different organisms that are related to each other by the food they consume.

• Food web - is an interconnection of different food chains in an ecosystem.

• Both food chains and food webs outline who eats whom in an ecosystem.
• The organisms are classified into different categories according to their feeding order.
  • Producers - synthesize food from solar energy. This covers all photosynthesizing plants and algae.
  • Primary consumers - come immediately after producers and comprise herbivores that feed on the producers directly.
  • Secondary consumers - feed on primary consumers and hence comprise of carnivores.
  • Decomposers - break down dead, decaying organisms into simpler inorganic substances. E.g. - Fungi.

Important Points

• Scavengers - are carnivorous organisms that feed on the dead and decaying flesh of an animal.
• They differ from other carnivores because they do not hunt.
• Examples - Vultures, Hyenas, Jackals, Crows.

Additional Information

• There are two main types of food chains:
  • Grazing - These food chains start with the producers and are the major system of energy flow in aquatic ecosystems.
  • Detritus - The starting point is dead organic matter from other food chains and is the major energy flow system in terrestrial ecosystems.

The correct answer is Flagellates.Key Points

• Flagellates are found in the bottom of a pond.
  • They are an example of Protozoa.
  • Protozoa are found in soil, freshwater, and seawater.
  • Some are found in the body of other organisms and are pathogenic. These are unicellular organisms with eukaryotic cells.
  • There is great variation in cell structure, organs of locomotion and modes of nutrition among protozoa.
  • These organisms reproduce by simple cell division.

Additional Information

• Zooplankton is present on the second trophic level in a food chain in the aquatic ecosystem.
• They are primary consumers as they eat phytoplankton (producers) and are themselves in turn eaten by small fishes (secondary consumers).
• Jellyfish and sea jellies are the informal common names given to the medusa-phase of certain gelatinous members of the subphylum Medusozoa, a major part of the phylum Cnidaria. 

The correct option is Humus.

Key Points

• Humus is an amorphous dark-coloured and colloidal substance which is highly resistant to microbial action.
• It undergoes decomposition at an extremely slow rate.
• It can also act as a bank for nutrients.
• The process that leads to the formation of humus is known as humification.
• Humus is further degraded by some microbes and the release of inorganic nutrients occurs through the process known as mineralisation.

Additional Information

• Chitin
  • Chitin is the most abundant amino polysaccharide polymer occurring in nature and is the building material that gives strength to the exoskeletons of crustaceans, insects, and the cell walls of fungi.
• Carotenoids
  • They are pigments in plants, algae, and photosynthetic bacteria. These pigments produce bright yellow, red, and orange colours in plants, vegetables, and fruits.
  • Carotenoids act as a type of antioxidant for humans.
• Colloids
  • A colloid is one of the three primary types of mixtures, with the other two being a solution and suspension. A colloid is a mixture that has particles ranging between 1 and 1000 nanometers in diameter, yet are still able to remain evenly distributed throughout the solution.

The correct answer is Water is a cyclic resource.Key Points

• Water is a cyclic resource, as it is present in different states and abundant supplies around the globe.
• A cyclic resource is what can be formed, again and again, Similarly water is a cyclic resource.
• The water from the sea, river, ocean, etc. evaporates and condenses to form clouds.
• When the rain occurs water from these clouds comes onto earth and flows down into water resources.

Important Points

• The hydrological cycle is also known as the water cycle; it is the normal water recycling system on Earth. 
• It is the total of all processes in which water moves from the land and ocean surface to the atmosphere and back in form of precipitation.
• Though water is an abiotic component of the environment, it is not described as one since water carries many biotic components in it which are often crucial for the sustenance of life on earth.

Additional Information

• Water is, indeed a renewable resource.
• Water has three states.
• Water or Fresh Water is a renewable Natural Resource.
• However, it should be noted that freshwater is a non-renewable energy resource.
• Water is used as a power generation tool by using turbines and steam boilers.
• Water also acts as one of the five elements which enable humans to live on this planet.
• Water is a cyclic resource as it is used and reused.
• About 71% of the planetary water is found in the oceans.
• The remaining is held as freshwater in glaciers and ice caps, groundwater sources, lakes, soil moisture, atmosphere, streams, and within life.
• About 59% of the water on the land surface evaporates and returns to the atmosphere.
• The remaining run-off on the surface penetrates the ground or a part of it becomes glaciers.

The correct answer is Net primary productivity and gross primary productivity.

Key Points

• Primary production is defined as the amount of biomass or organic matter produced per unit area over a time period by plants during photosynthesis.
• It is expressed in terms of gm^–2 yr ^–1 or (kcal m^–2 ) yr ^–1 to compare the productivity of different ecosystems
• It can be divided into gross primary productivity (GPP) and net primary productivity (NPP).
• The gross primary productivity of an ecosystem is the rate of production of organic matter during photosynthesis
• Net primary productivity, or NPP, is gross primary productivity excluding the rate of energy loss to metabolism and maintenance.
• Net primary productivity is the rate at which energy is stored as biomass by plants or other primary producers and made available to consumers.
• GPP – R = NPP ( R represents the Respiration losses)

Additional Information

• Primary productivity depends on the plant species inhabiting a particular area.
• Secondary productivity is defined as the rate of formation of new organic matter by consumers.
• The annual net primary productivity of the whole biosphere is approximately 170 billion tons (dry weight) of organic matter.
• Despite occupying about 70 per cent of the surface, the productivity of the oceans is only 55 billion tons.

The correct answer is As biomass.

Key Points

• Each trophic level has a certain mass of living material at a particular time called the standing crop, this standing crop is measured as the biomass of living organisms, as the number in a unit area.
• An ecological pyramid is a pictorial representation of the relationship between different organisms in an ecosystem.
• It is of three types: Pyramid of the number, Pyramid of biomass, and Pyramid of energy.

Additional Information

• The pyramid of energy represents the total amount of energy consumed by each trophic level in a given food chain.
• According to the 10% law of energy transfer, only 10% of the total energy is transferred from one trophic level to another.
• Therefore the total amount of energy available for utilization in the layers above is less than the energy available in the lower levels, so the pyramid is always upright.