MCQs on Ecology & Ecosystem (Environment)

• Planktons, Fish, Whale are found in the Aquatic ecosystem.

• A food chain in a grassland ecosystem may consist of grasses and other plants, grasshoppers, frogs, snakes, and hawks.

• There are two types of food chains: the grazing food chain and detrital food chain
  • The grazing food chain begins with autotrophs.
    • In a grazing food chain, energy and nutrients move from plants to the herbivores consuming them, and to the carnivores or omnivores preying upon the herbivores.
  • The detrital food chain begins with dead organic matter.
    • In a detrital food chain, dead organic matter of plants and animals is broken down by decomposers, e.g., bacteria and fungi, and moves to detritivores and then carnivores.

• 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 series or organisms taking part at various biotic levels form a food chain.
• Each step or level of the food chain forms a trophic level.
• The flow of energy in a food chain is unidirectional.
• The energy that is captured by the autotrophs does not revert back to the solar input, the energy which passes to the herbivores does not come back to autotrophs and so on.
• As it moves progressively through the various trophic levels it is no longer available to the previous level.

• An ecosystem consists of a community of organisms together with their physical environment consists of two components Biotic and Abiotic.
  • Abiotic consists of non-living organisms(air, water, soil, minerals, sunlight.
  • Biotic consists of living organisms (Producers, Consumers, Decomposers).

• The Food Chain is a linear sequence of organisms where nutrients and energy are transferred from one organism to another.
  • Producers make their own food. Example- Green plants.
  • Primary Consumers depend on the producers. Example- Grasshooper
  • Secondary consumers depend on the primary consumer for energy. Example- Frog
  • Tertiary consumerdepends on the secondary consumers for the food. Example- Snake
  • Decomposers are microorganisms that decompose the dead and decaying material into humus which enriches the soil. Example- Bacteria, Fungus.

• Elephants, Bears and Rhinos are examples of Mammals.
• Mammals are a group of vertebrate animals of the class Mammalia, characterised by the presence of mammary glands which in females, provide milk for feeding their young, brain region, fur or hair, and three middle ear bones.
• The most common orders are rats, bats and eulipotyphs (hedgehogs, moles, shrews, and others).
• The next three are the Primates (ape-like humans, chimpanzees, among others), the Artiodactyla (cetaceans and even-toed ungulates) and the Carnivora (cats, dogs, seals, and others).
• The basic body shape is quadrupled, and most animals use their four extremities for terrestrial locomotion; but in others, the extremities are modified for life at sea, in the clouds, in forests, underwater, or on two legs. Mammals range in size from 30–40 mm (1.2–1.6 in) bumblebee bat to 30 m (98 ft) blue whale-possibly the largest mammal known to have existed.
• Maximum lifespan ranges from two years in the shrew to 211 years in the bowhead whale.

• Biodilution is known as bloom dilution, the process of biodilution is the decrease in the concentration of a substance (especially pollutants, like heavy metals) with an increase in trophic level in the food chain.
  • This phenomenon is observed mostly in eutrophic (nutrient-rich and highly productive) water environments.
  • For example, during algal blooms, an increase of algae reduces the concentration of pollutants a consequence of their larger biomass refers to a decrement in the concentration or quantity of a pollutant when that particular pollutant gains a higher trophic level through consumption.
  • Studies of bioaccumulation have led to researchers discovering the importance of biodilution.
• ​Hence the option 1 is correct.

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• A large percentage of studies conducted have almost invariably concluded that there is a relationship between biodilution and bioaccumulation.
  • Zooplankton that lives in places that have higher amounts of nutrients and productivity has been shown to contain lesser amounts of mercury compared to those that do not.
• If creatures in the lower trophic levels multiply exponentially during a bloom, then the heavy metals absorbed by them will, in turn, reduce since there are more absorbers.
  • Consequently, when these primary producers are eaten by those organisms occupying higher levels, they transfer fewer amounts of heavy metals.
  • This process creates a ripple effect that goes all the way to the top consumers, such as humans.
  • The overall effect is known as biodilution.
  • Some of the organisms that will experience a reduction in pollutants after the algal bloom include the likes of daphnia and zooplankton.

• The benthic zone is the ecological region at the lowest level of a body of water.
• It starts at the shoreline and continues down until it reaches the floor, encompassing the sediment surface and subsurface layers.
• Although this zone may appear barren, it plays a vital role in the health of aquatic ecosystems.
• Tiny, microscopic benthic organisms live in this zone and act as a source of food for bottom-feeding animals.
• Benthic organisms are very important as they are good indicators of water quality.

• Ecosystem Functions:
  • Despite being out of sight, the benthic zone is a highly important contributor to lake ecosystems.
  • This area alone offers spawning, foraging, and shelter opportunities for various aquatic species.
  • The benthic zones in the shallow shoreline waters provide ideal conditions for fish and amphibian spawning.
  • Aquatic vegetation provides cover while the substrate provides materials to hold the eggs to the ground along with some extra insulation to keep eggs warm.
  • However, changes in water temperatures and levels from the use of dams and industrial operations can impact shallow water spawning grounds, larvae, and mature benthic dwellers.
  • The benthos living in this zone act as a food source for other aquatic species, as well as humans.
• Benthos are also critical for the breakdown of organic matter.
  • Species use organic matter as their food source making them a key player in the nutrient cycling process.
  • Also, the filter feeders that live in this zone, such as mussels, are responsible for removing pollutants and sediments suspended in the water.
  • By contributing to nutrient cycling and pollutant and sediment removal, benthos is directly responsible for maintaining healthy water quality.

• The sequence of eating and being eaten produces a transfer of food energy and it is known as the food chain.
• A sequence of organisms that feed on one another, form a food chain.
• The amount of energy decreases as it passes from one trophic level to another trophic level.
• As little as 10 percent of the energy at any trophic level is transferred to the next level and the rest is lost largely through the metabolic process as heat.

• Quinine is a medication used to treat parasite causing malaria disease.
  • It is extracted from the bark of the cinchona tree.
  • Quinine was first isolated in 1820.
  • Quinine is also used for the treatment of babesiosis.
  • Quinine is the ingredient in tonic water that gives it its bitter taste.
  • Quinine is on the world health organization's list of essential medicines.
  • Malaria is caused by plasmodium parasite.
• Drugs like vincristine and vinblastine extracted from vinca rosea are used for the treatment of blood cancer.
• Reserpine extracted from the plant serpentine is used for the treatment of systolic hypertension.

Explanation:

Ecosystem: All organisms such as plants, animals, microorganisms and human beings as well as the physical surroundings interact with each other and maintain a balance in nature. All the interacting organisms in an area together with the non-living constituents of the environment form an ecosystem.

Food chain: A food chain shows the feeding relationship between different organisms in a particular environment and/or habitat.

• A food chain shows how energy is passed from the sun to producers, from producers to consumers, and from consumers to decomposes such as fungi.
• They also show how animals depend on other organisms for food.

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Only 10% of energy is transferred to higher levels from the previous one. So, the demand for food is more in higher levels. So, the food chain does not go for more than 3-4 tropic levels. This leads to more complex food forms known as a food web.

Primary (100%) → First level/ Primary (10%) → Second-level/ Secondary (1%) → Third level / Tertiary (0.1%).

Food web is a network of food chains where all the chains are naturally interconnected.

The flow of energy in a food chain is unidirectional, once it reaches the next tropic level it does not come back again.

• Chemosynthesis
  • Chemosynthesis is the process by which food (glucose) is made by bacteria using chemicals as the energy source, rather than sunlight.
  • Chemosynthesis occurs around hydrothermal vents and methane seeps in the deep sea where sunlight is absent.
  • During chemosynthesis, bacteria living on the seafloor or within animals use energy stored in the chemical bonds of hydrogen sulfide and methane to make glucose from water and carbon dioxide (dissolved in seawater).
  • Pure sulfur and sulfur compounds are produced as by-products.

• Photosynthesis
  • ​Ituses water, sunlight, and carbon dioxide, and it makes glucose and oxygen.
• Cellular respiration
  • ​It uses glucose and oxygen, and it makes water and carbon dioxide, and energy.
• Carbon sequestration
  • ​It is the process involved in carbon capture and the long-term storage of atmospheric carbon dioxide or other forms of carbon to mitigate or defer global warming.

• 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.

• Hummingbirds are the only birds that can fly backward.
• These Birds are the world’s smallest migrating birds.
• The design of these bird wings differs from most other types of birds.
• They have a unique ball and socket joint at the shoulder that allows the bird to rotate its wings 180 degrees in all directions.
• The shape of these bird wings is long, narrow, and tapered, which allows them to move more rapidly and easily through the air. Additionally, their shoulder and elbow joints of the wing are very close to their tiny bodies, allowing their wings to tilt and pivot.
• These characteristics allow these bird to change flight directions in such a way that other birds cannot.

Concept:

Food chain: A food chain shows the feeding relationship between different organisms in a particular environment and/or habitat. A food chain shows how energy is passed from the sun to producers, from producers to consumers, and from consumers to decomposes such as fungi. They also show how animals depend on other organisms for food.

• Food chain is distributed between Autotrophs, Hetrotrops, and Decomposers i.e Producers, consumers and decomposers.
• Autotrophs produce their own food like plants, trees and some algae.
• Heterotrophs are consumers i.e. animals, man, insects etc.
• Decomposers are bacteria, fungi etc.

Explanation:

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Thus, the correct sequence is Grass → Grasshopper → Frog → Snake → Hawk.

From autotrophs, the energy goes to the heterotrophs and decomposers. When one form of energy is changed to another, some energy is lost to the environment in forms that cannot be used again.

The green plants in a terrestrial ecosystem capture only about 1% of the energy of sunlight that falls on their leaves and convert it into food energy.

When green plants are eaten by primary consumers, a great deal of energy is lost as heat to the environment, some amount goes into digestion and in doing work and the rest goes towards growth and reproduction. An average of 10% of the food eaten is turned into its own body and made available for the next level of consumers.

• Marine ecosystems are aquatic environments with high levels of dissolved salt.
• These include the open ocean, the deep-sea ocean, and coastal marine ecosystems, each of which has different physical and biological characteristics.
• Marine ecosystems are defined by their unique biotic (living) and abiotic (nonliving) factors.
• Biotic factors include plants, animals, and microbes.
• Important abiotic factors include the amount of sunlight in the ecosystem, the amount of oxygen and nutrients dissolved in the water, proximity to land, depth, and temperature.
• Coral reefs are a diverse form of the marine ecosystem, which in total may account for a quarter of all ocean species.
• The ratio of fish compared to elasmobranchs such as sharks, skates, and rays – has remained stable for periods of tens of millions of years, despite extreme environmental changes caused by climate shifts of the past.
• As the depth of the ocean increases, it gets darker, colder, and with less available oxygen.
• Organisms living in deep-sea ecosystems within the dysphotic and aphotic zones have unusual adaptations that help them survive in these challenging environments.
• Some organisms have extremely large mouths that allow them to catch whatever nutrients fall from shallower ocean depths.

• 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.

• A biome is an area of the planet that can be classified according to the plants and animals that live in it.
  • Temperature, soil, and the amount of light and water help determine what life exists in a biome.
  • Biomes are distinct biological communities that have formed in response to a shared physical climate.
  • A biome is a broader term than habitat.
• Each biome consists of many ecosystems whose communities have adapted to the small differences in climate and the environment inside the biome.”
• Hence the option 1 is correct.

• Biomes or Terrestrial Ecosystems
  • The terrestrial part of the biosphere is divisible into enormous regions called biomes.
  • No two biomes are alike.
    • They are characterized, by a distinct climate (precipitation and temperature mainly), vegetation, animal life, and general soil type.
  • The climate determines the boundaries of a biome and the abundance of plants and animals found in each one of them.

Concept:​​

• Eutrophication: It is an enrichment of water by nutrient salts that causes structural changes to the ecosystem.
• Compounds that contain nitrogen and phosphorus (fertilizers) drive the eutrophication. These nutrients are generally not toxic.
• Effects on aquatic life: They can have a large impact on the health of rivers and estuaries such as increased overgrowth of algae and aquatic plants, depletion of fish species, general deterioration of water quality.

Explanation:

• To increase crop yield, fertilizers contain nitrates and phosphates.
• When these get washed up into water bodies, the resulting increase of nitrate or phosphate in the water encourages algae growth, which forms a bloom over the water surface.
• The algae leech the nutrient from the water body and kill aquatic life.
• So, eutrophication in the lake is due to the presence of nitrogen and phosphorous.

• Eutrophication is the increase in the concentration of nutrients in an ecosystem.
• Cultural eutrophication is the process that speeds up natural eutrophication because of human activity.
• Natural eutrophication has been occurring for millennia.
• The most common nutrients causing eutrophication are nitrogen N and phosphorus P.

• Increased nutrient enrichment can arise from both point and non-point sources.
• Eutrophication is the mechanism by which the lakes obtain nutrients (phosphorus and nitrogen) and sediments from the surrounding.
• Sulfur dioxide is released naturally by volcanic activity and is produced as a by-product of copper extraction and the burning of fossil fuels contaminated with sulfur compounds.
• Sulfur dioxide is widely used in the food and drinks industries for its properties as a preservative and antioxidant.