Short & Long Question Answers with Solution: Ecosystem | Biology Class 12 - NEET PDF Download

Short Answer Type Questions

Q1: What are the three types of ecological pyramids?
Ans: The three types of ecological pyramids include:

• Pyramid of Number.
• Pyramid of Biomass.
• Pyramid of Energy.

Q2: Describe the importance of the ecosystem.
Ans: Ecosystems play a crucial role in maintaining environmental equilibrium. They provide us with clean air for respiration and act as carbon reservoirs to regulate the climate. Ecosystems also facilitate nutrient cycling through various biogeochemical processes, ensuring access to clean drinking water without the need for costly treatments. They serve as habitats for numerous species, offering both food and shelter. Furthermore, ecosystems serve as sources of raw materials for various domestic and commercial purposes.

Q3: What is the Ecological Pyramid?
Ans: An ecological pyramid is a visual depiction illustrating the connections among various organisms in different trophic levels within an ecosystem.

Q4: Why do abiotic elements like temperature, oxygen availability, and soil pH affect the rate of decomposition?
Ans: The configuration of basophilic (alkaline-loving) and acidophilic (acid-loving) bacteria is shaped by the soil's pH level. Anaerobic processes occur when oxygen is absent and only partially break down a substance, while aerobic processes occur in the presence of oxygen and fully break down a substance. Microorganisms cannot reach their optimal growth potential at higher temperatures; however, stress-tolerant microbes flourish in low or high-temperature conditions.

Q5: What is the importance of the ecosystem?
Ans: Ecosystems contribute to environmental equilibrium by supplying clean air for respiration and acting as carbon reservoirs to control the climate. They facilitate nutrient circulation through various biogeochemical processes, ensuring access to uncontaminated drinking water without the need for expensive treatments. Ecosystems serve as habitats, offering sustenance and refuge to numerous organisms. Additionally, they serve as sources of raw materials for diverse industrial and household needs.

Q6: Why is the rate of decomposition affected by abiotic factors such as pH of the soil, availability of oxygen, temperature etc?
Ans: The soil's pH level influences the configuration of basophilic (preferring alkaline conditions) and acidophilic (preferring acidic conditions) microorganisms. Aerobic processes occur when there is oxygen present, leading to the complete breakdown of a substance, while anaerobic processes occur in the absence of oxygen, resulting in an incomplete breakdown of substances. Microorganisms do not thrive to their maximum potential at elevated temperatures; however, stress-tolerant microbes thrive in both low and high-temperature environments.

Q7: How can the problem of “tiger poaching” impact the ecosystem’s ability to function?
Ans: Tigers have a vital role in the food chain and contribute to maintaining ecological equilibrium. They help regulate the health of the forest by controlling the population of herbivores and by removing sick and elderly animals from the ecosystem. The presence of tigers also serves as an indicator of the forest's well-being. Protecting tigers is intertwined with the conservation of forests and ensuring the availability of food and water resources for all.

Q8: In the study of the ecosystem, what are the limitations of ecological pyramids?
Ans: The following are the shortcomings:

• One species can operate at multiple trophic levels.
• These pyramids depict only straightforward food chains, whereas nature predominantly consists of intricate food chains.
• Decomposers, which are essential for ecosystem stability, are not considered in these pyramids.

Q9: Why are the trophic levels in the ecosystem limited?
Ans: The limited number of trophic levels, typically around 4-5, is due to the fact that only about 10% of energy is transferred from one trophic level to the next, and this energy transfer decreases as we move up the food chain. The remaining energy is used for essential life processes like respiration, leaving insufficient energy to sustain additional trophic levels through the flow of energy. As a result, the number of trophic levels is constrained.

Q10: Why does primary productivity vary in different ecosystems?
Ans: Primary productivity is the speed at which plants, also known as primary producers, capture and store solar energy to create chemical energy. This process varies across ecosystems because the type and abundance of producers differ, directly influencing the levels of primary production.

Long Answer Type Questions

Q1: What is the Food Chain? Explain the different types of food chains in the ecosystem.
Ans: A food chain is described as a series of interconnected links within a food web that illustrates the energy flow within an ecosystem.
In this system, producers are consumed by various levels of consumers, including primary and secondary consumers, and ultimately by detritivores and decomposers. When multiple individual food chains coexist within an ecosystem, they collectively form a Food Web. To some extent, both food chains and food webs share similarities with each other.

Q2: Explain the biogeochemical cycle. What role does the reservoir play in this cycle? Give an illustration of a sedimentary cycle using a reservoir found in the earth’s crust.
Ans: A biogeochemical cycle represents the movement of nutrient molecules through various components of ecosystems. There are two distinct types of nutrient cycles: sedimentary and gaseous. The atmosphere serves as the reservoir for gaseous cycles, like the nitrogen cycle, while for sedimentary cycles, the earth's crust acts as the reservoir, as seen in the phosphorus cycle. The purpose of the reservoir is to compensate for any shortage resulting from imbalances in the outflow and influx of nutrients. The rate at which nutrients are released into the atmosphere is influenced by various environmental factors such as temperature, soil moisture, pH, among others.
The phosphorus cycle, which relies on the earth's crust as its natural reservoir, serves as an example of a sedimentary cycle. It originates on land, moves into the ocean, and then returns to land. Phosphates, found in rocks, enter water bodies due to processes like weathering and soil erosion. The uplifting of seafloors caused by tectonic plate movements exposes phosphates on land surfaces. Over time, weathering releases phosphates, making them more accessible in the soil, where plant roots absorb them. Herbivores and other organisms obtain this element from plant producers. Phosphorus is further released into the ecosystem during the decomposition of deceased organisms and organic matter, facilitated by phosphate-solubilizing bacteria.

Q3: Explain  Biotic Components and Abiotic Components of the Ecosystem with examples.
Ans: Ecosystems consist of two interconnected components: Biotic and Abiotic.

• Biotic Components encompass the various living organisms present in an ecosystem. These biotic components can be classified into autotrophs (organisms that produce their own food), heterotrophs (organisms that rely on others for food), and saprotrophs (decomposers that break down organic matter).
• Abiotic Components, on the other hand, constitute the non-living elements within an ecosystem. Examples of abiotic components include elements such as air, water, soil, minerals, sunlight, temperature, nutrients, wind, altitude, and turbidity.

Q4: Define decomposition. Describe the many steps involved in decomposition.
Ans: Decomposers, which include bacteria and fungi, play a crucial role in converting complex organic matter into simpler inorganic elements like carbon dioxide (CO2), water (H2O), and minerals. This process is known as decomposition. Detritus comprises the remains of deceased plants such as leaves, bark, flowers, as well as deceased animals and feces.
Several important decomposition processes include:

• Fragmentation: Detritivores, organisms specialized in this role, break down detritus into smaller pieces.
• Leaching: Water-soluble inorganic nutrients leach into the soil layer, where they eventually precipitate as less accessible salts.
• Catabolism: Enzymes produced by bacteria and fungi break down detritus into basic inorganic compounds.
• Humification: This process leads to the accumulation of humus, a dark-colored, amorphous substance. Humus decomposes at an extremely slow rate and is highly resistant to microbial degradation.
• Mineralization: Some microorganisms further break down humus, releasing inorganic nutrients through the mineralization process.

Q5: Explain the biogeochemical cycle. What is the significance of the reservoir in this cycle? With a reservoir situated in earth’s crust, give an example of a sedimentary cycle.
Ans: A biogeochemical cycle refers to the movement of nutrient molecules through various elements of an ecosystem. There are two types of nutrient cycles: sedimentary and gaseous. In gaseous cycles, the atmosphere serves as the reservoir, as seen in the nitrogen cycle, while in sedimentary cycles, the earth's crust acts as the reservoir, as exemplified by the phosphorus cycle. The role of the reservoir is to compensate for deficiencies that occur due to imbalances in nutrient outflow and inflow. Various environmental factors, including temperature, soil moisture, and pH, influence the rate at which nutrients are released into the atmosphere.
The phosphorus cycle is an example of a sedimentary cycle, starting on land, moving into the ocean depths, and then returning to land. Phosphates, in the form of phosphates, are found in rocks. Erosion and weathering processes introduce them into water bodies. The movement of crustal plates results in the uplift of seafloors, exposing phosphates on land surfaces. Over time, weathering releases these phosphates, making them available in soil and absorbable by plant roots. Herbivores and other organisms acquire this element from plant producers. Phosphorous is also released during the decomposition of deceased organisms and waste materials, facilitated by phosphate-solubilizing bacteria.

Q6: What do you mean by an ecosystem’s productivity? What forms of productivity also discuss the variables that affect an ecosystem’s production?
Ans: Ecosystem productivity refers to the rate at which vegetation within an ecosystem converts solar radiation energy into biomass per unit area and per unit time. This measure is typically expressed as energy units (calories) produced within a given area (square meters) over a specific time period (usually a year).
There are two main types of productivity:

• Primary productivity: This represents the amount of biomass or organic matter produced by plants through photosynthesis within a specific area over a certain period of time. Primary productivity is categorized into two types:
  • Gross primary productivity (GPP) quantifies the total amount of food produced by producers (plants) during photosynthesis.
  • Net primary productivity (NPP) is calculated as the difference between respiration loss (R) and gross primary productivity:
    NPP = R - GPP
• Secondary productivity: Secondary productivity pertains to the rate at which consumers store organic materials, and it measures how quickly consumers synthesize these materials over a specific time period.

Various factors influence primary productivity, including environmental conditions, nutrient availability, and the capacity of plants to perform photosynthesis.

Q7: Explain how energy flow supports the second law of thermodynamics in an ecosystem.
Ans: According to the second law of thermodynamics, any process involving transformations results in energy wastage in the form of heat and an increase in disorder, with the exception of deep hydrothermal ecosystems. In the case of Photosynthetically Active Radiation (PAR), only a small percentage, typically ranging from 2% to 10%, is absorbed by organisms engaged in photosynthesis to produce organic matter. Subsequently, this energy is utilized for metabolic activities, food production, and biomass storage, although the latter is relatively minimal.
The biomass or captured energy is then transferred to the next trophic level following Lindeman's law, which states that approximately 10% of the stored energy is passed on to the next trophic level in a consecutive manner.

Q8: Describe how the law of thermodynamics is supported by energy flows in an ecosystem.
Ans: The second law of thermodynamics dictates that any process involving transformations leads to energy loss in the form of heat and an increase in disorder, except for deep hydrothermal ecosystems. In the context of Photosynthetically Active Radiation (PAR), only a small fraction, typically ranging from 2% to 10%, is absorbed by organisms engaged in photosynthesis, resulting in the production of organic matter. This energy is subsequently allocated for various purposes, including metabolic processes, food production, and biomass storage, although the latter is minimal. Following Lindeman's law, the biomass or captured energy is passed on to the subsequent trophic level, with approximately 10% of the energy reserves being transferred from one trophic level to the next in a cascading manner.

Q9: How does nature favour to raise the gross primary productivity while man tends to raise the net primary productivity?
Ans: Energy within an ecosystem follows a unidirectional flow from one trophic level to the next. In nature, systems are designed to benefit organisms engaged in specific activities. For instance, plants primarily engage in photosynthesis, which constitutes their primary activity and contributes to gross primary productivity. The efficiency of this activity in plants depends on the inputs it receives and tends to increase with higher inputs.
Humans, on the other hand, rely on plants as part of their net primary productivity. Whether a specific plant has a low or high gross primary productivity is not a major concern for humans, as they are more interested in the overall productivity of plants as a source of sustenance.

Q10: When compared to how man tends to increase net primary productivity, how does nature favour increasing gross primary productivity?
Ans: Energy in an ecosystem flows in a one-way direction from one trophic level to the next. Natural systems are designed to benefit organisms engaged in specific activities. For instance, plants primarily engage in photosynthesis, which is their main activity and constitutes the primary source of gross primary productivity. The efficiency of this plant activity depends on the inputs it receives, and higher inputs lead to increased production.
In contrast, humans depend on vegetation for their sustenance. They are not concerned about whether a particular plant has a high or low gross primary productivity because it is a part of their net primary productivity.