RBSE Solutions Class 11 Biology Chapter 40 Ecosystem Structure and Function

RBSE Class 11 Biology Chapter 40 Multiple Choice Objective Questions

Question 1. Term "Ecosystem" was first used by
(a) R. Mishra
(b) Odum
(c) Climentus
(d) Tansley
Answer: (d) Tansley
In simple words: The word "Ecosystem" was first used by a scientist named Tansley. He helped us understand how living things and their environment work together.

🎯 Exam Tip: Remember key scientific terms and the scientists who first introduced them, as this is a common type of factual question.

Question 2. Assimilation of organic compounds at consumer level is called
(a) Primary production
(b) Gross production
(c) Secondary production
(d) Real production
Answer: (c) Secondary production
In simple words: When consumers take in and use organic food, it's called secondary production. They are not making new food from scratch like plants do.

🎯 Exam Tip: Distinguish between primary production (by producers) and secondary production (by consumers) to avoid confusion.

Question 4. The energy pyramid of grassland or pond ecosystem is always
(a) Inverted
(b) Inverted or straight
(c) Straight
(d) None of the options
Answer: (c) Straight
In simple words: In most ecosystems like grasslands or ponds, the energy pyramid always shows more energy at the bottom (producers) and less energy as you go up (consumers). This makes it look like a straight, upright pyramid.

🎯 Exam Tip: Understand that energy flow is always unidirectional and decreases at each trophic level, making energy pyramids generally upright.

Question 5. Alternative path of energy flow are found in
(a) Food web
(b) Food Chain
(c) Ecological Pyramid
(d) Bio geo chemical cycle
Answer: (a) Food web
In simple words: A food web shows many different ways energy can move between living things. Unlike a simple food chain, it offers alternative paths for energy flow.

🎯 Exam Tip: A food web represents a more realistic and complex network of feeding relationships compared to a single food chain.

RBSE Class 11 Biology Chapter 40 Very Short Answer Questions

Question 1. The equivalent name of ecosystem given by Prof. Mishra.
Answer: Ecocosm
In simple words: Prof. Mishra called an ecosystem by another name, "Ecocosm."

🎯 Exam Tip: Be aware of different terms used by scientists for the same ecological concepts, especially historical ones.

Question 2. Crop field and Garden are which type of ecosystem?
Answer: Crop fields and gardens are man-made ecosystems. They can be divided into two main parts: Lotic and Lentic.
In simple words: Crop fields and gardens are ecosystems created by people, and they can be split into two types based on water movement.

🎯 Exam Tip: Classify ecosystems as natural or artificial (man-made) and be able to give examples of each.

Question 4. Write the names of main components of ecosystem.
Answer: The main parts of an ecosystem are biotic and abiotic components. Biotic parts are all living things, and abiotic parts are non-living things like soil and water.
In simple words: An ecosystem has two main parts: living things (biotic) and non-living things (abiotic).

🎯 Exam Tip: Always remember the fundamental division of ecosystem components into biotic (living) and abiotic (non-living).

Question 5. Who proposed the term convert for the producers?
Answer: E.J. Kormondy was the one who suggested using the term "converter" for producers. This highlights their role in changing energy into usable forms.
In simple words: E.J. Kormondy suggested calling producers "converters" because they change energy.

🎯 Exam Tip: Know the specific contributions of important ecologists to the field.

Question 6. Who first gave the concept of ecological pyramids?
Answer: Charts Elton (1972) first introduced the idea of ecological pyramids. These pyramids show the relationships between different levels in a food chain.
In simple words: Charts Elton first came up with the idea of ecological pyramids in 1972.

🎯 Exam Tip: Relate the concept of ecological pyramids back to Elton and his contribution.

Question 7. What is photosynthetic Active radiation (PAR) for plants?
Answer: Photosynthetic Active Radiation (PAR) for plants refers to the solar radiation that ranges from 400 to 700 nanometers. This specific spectral band of light is what plants use for photosynthesis.
In simple words: PAR is the sunlight from 400 to 700 nanometers that plants use to make food.

🎯 Exam Tip: Define PAR accurately and mention its specific wavelength range, as this is crucial for understanding plant photosynthesis.

RBSE Class 11 Biology Chapter 40 Short Answer Questions

Question 1. Give the definition of ecosystem given by Tansley.
Answer: According to Tansley, an ecosystem involves the interaction between all organisms and their physical environment. This interaction helps maintain a balance between the living things and their surroundings, leading to the exchange of substances and the flow of energy. This system is known as an Ecosystem or Ecological system. Although Prof. Mishra called it "Ecocosm", the term "ecosystem" is widely accepted.
In simple words: Tansley said an ecosystem is when living things and their physical environment interact, sharing materials and energy, to stay balanced.

🎯 Exam Tip: When defining a term by a specific scientist, make sure to include the key elements of their definition, such as interaction, balance, and energy/substance exchange.

Question 2. What do you mean by functions of Ecosystem.
Answer: Ecosystem functions describe the biological, geochemical, and physical processes and parts that happen within an ecosystem. Simply put, it's about the ecosystem's structure and how its parts work together. Ecosystem functions can be explained using:
(A) Ecological Pyramids
(B) Food Chains and Food Webs
(C) Energy Flow
(D) Cycling of Minerals.
In simple words: Ecosystem functions are all the natural processes and interactions that happen inside an ecosystem, like how energy moves or how elements cycle, explained by pyramids, food chains, and more.

🎯 Exam Tip: When asked about ecosystem functions, list and briefly explain the main processes like energy flow, nutrient cycling, and trophic relationships.

Question 3. Define Ecological efficiency?
Answer: Ecological efficiency is a measure of how well energy is transferred from one trophic (feeding) level to the next. On average, only about 10% of the energy from one level is transferred to the next, while the rest is lost, mostly as heat.
In simple words: Ecological efficiency shows how much energy moves from one part of a food chain to the next, which is usually around 10%.

🎯 Exam Tip: The "10% rule" is a crucial concept in ecological efficiency; make sure to mention it in your definition.

Question 4. Differentiate Primary producers and Secondary producers.
Answer: Primary producers are organisms, mainly plants, that create their own food through processes like photosynthesis. They form the base of the food chain. Secondary producers are typically carnivores or omnivores that eat other organisms (primary consumers or other secondary consumers) to get energy. The original source refers to "Quaternary producers" as secondary producers which is a less common term for secondary consumers.
In simple words: Primary producers are plants making their own food. Secondary producers are animals that eat other animals.

🎯 Exam Tip: Clearly define primary producers (autotrophs) and secondary producers (carnivores/omnivores) and their roles in energy flow.

Question 5. Give two-two examples of blue green algae and symbiotic bacteria associated with Nitrogen fixation.
Answer: Here are examples for each category:
Symbiotic bacteria: Azotobacter and Rhizobium.
Blue-green algae: Nostoc and Anabaena.
In simple words: Azotobacter and Rhizobium are bacteria that help plants get nitrogen. Nostoc and Anabaena are blue-green algae that do the same.

🎯 Exam Tip: Memorize specific examples of organisms for important biological processes like nitrogen fixation.

Question 6. Differentiate standing state and standing crop.
Answer: Standing state refers to the amount of inorganic nutrients present in an ecosystem at a specific time, such as carbon, nitrogen, and phosphorus. Standing crop, on the other hand, is the total living biomass (amount of living organisms) present in a given area or ecosystem at a particular time.
In simple words: Standing state is about the non-living nutrients in the ecosystem right now. Standing crop is about the total weight of all living things in the ecosystem right now.

🎯 Exam Tip: Clearly distinguish between "state" (inorganic, non-living) and "crop" (organic, living biomass) when differentiating these terms.

RBSE Class 11 Biology Chapter 40 Essay Type Questions

Question 1. What do you mean by ecological pyramids? Describe ecological pyramids of number and biomass in forest ecosystem.
Answer: Ecological Pyramids:
The ecological food chain has many food levels, called trophic levels, where each level is a step in how food is passed along. Many trophic levels are connected to each other.
An ecological pyramid is a picture that shows the relationship between different trophic levels in an ecosystem. These pyramids show the amount of living matter or how many organisms are present at each level. Charls Elton first introduced this idea in 1927, so they are also called Eltonian Pyramids. These pyramids are shaped like triangles.
There are three main types of ecological pyramids:
(A) Pyramids of Number:
These pyramids show the number of individual organisms at each trophic level. They illustrate that usually, the number of larger organisms is less than the number of smaller organisms. These pyramids can be upright (like in a grassland ecosystem) or inverted (like in a parasitic ecosystem). For example, a grassland ecosystem has many grass plants (producers), fewer rabbits (primary consumers), and even fewer foxes (secondary consumers), creating an upright pyramid.
(B) Pyramids of Biomass:
Biomass is the total amount of organic matter present in an organism. Pyramids of biomass show how much living material is present at each trophic level. These pyramids are typically upright in most ecosystems, such as grassland, forest, and crop ecosystems, meaning there is more biomass at the lower trophic levels (producers). For example, in a forest, the large trees (producers) have much more biomass than the animals that eat them (consumers).
In simple words: Ecological pyramids are drawings that show how many living things or how much living material there is at each level of a food chain. Pyramids of number count organisms, and pyramids of biomass weigh all the living matter. They usually get smaller as you go up the food chain.

🎯 Exam Tip: Define ecological pyramids clearly, state their types, and provide specific examples for upright and inverted pyramids of number and biomass.

Question 2. Explain food chain and food web by giving examples.
Answer: Food Chain:
Food refers to the organic substances used by plants and animals to get biological energy. Autotrophic plants (producers) make their own food through photosynthesis, using chlorophyll, carbon dioxide, water, and sunlight. These producers are eaten by primary consumers (herbivores). Primary consumers are then eaten by secondary consumers (carnivores), who in turn might be eaten by tertiary consumers or even larger top predators. This sequence of "who eats whom" in an ecosystem is called a food chain. Each step in the food chain is known as a trophic level, expressed as T1, T2, T3, and so on.
A food chain illustrates the feeding relationships between organisms. Usually, food chains have a maximum of six trophic levels. This is because at each level, about 90% of the energy is used for respiration and other activities, and only about 10% is transferred to the next trophic level. So, very little energy reaches the highest trophic levels.
Types of Food Chains:
(a) Grazing Food Chain: This type of food chain starts with living green plants. Energy captured from the sun by plants moves to grazing herbivores, then to carnivores. This chain depends on autotrophic energy and solar energy. Example: Grass → Rabbit ⇒ Fox ⇒ Lion ⇒ Bacteria.
(b) Parasitic Food Chain: This chain starts with larger organisms and ends with smaller, parasitic organisms. The large organisms are hosts, and the small organisms are parasites. Example: Man (Host) ⇒ Nematode (Parasite) ⇒ Bacteria (Parasite).
In simple words: A food chain shows how energy moves as one living thing eats another. A food web is like many food chains linked together, showing all the different ways energy flows in an ecosystem. Grazing chains start with plants, while parasitic chains start with a big host and end with small parasites.

🎯 Exam Tip: Define both food chains and food webs, emphasizing the linearity of a chain versus the interconnectedness of a web. Provide clear, simple examples for each type of food chain.

Question 3. What do you mean by ecosystem? Describe it structural aspects.
Answer: An ecosystem is a system where all organisms interact with their physical environment to maintain a balance. This interaction involves the exchange of substances and the flow of energy, forming what is known as an Ecosystem or Ecological system. The ecosystem is considered a functional unit of ecology. The British ecologist Arthur Tansley first used the term "ecosystem." He defined it as the interaction between biotic factors (like plants, animals, and other organisms) and abiotic factors (like weather, soil, air, and temperature).
Before Tansley, Karl Mobius (1877) called it Biocoenosis, Forbes (1887) used Microcosm, and Mishra referred to it as Ecocosm. However, "ecosystem" is the term universally accepted today.
Structure and Function of Ecosystem:
The structure of an ecosystem includes its biotic and abiotic components. Key structural features are the species composition (the types of species present) and stratification (how species are arranged vertically). It also involves studying the number of species, the biomass of organisms, their life cycles, their distribution, and the quantity and distribution of abiotic substances.
The function of an ecosystem involves the flow of energy and nutrients. These flows keep the various components of the ecosystem working together as a single unit.
In simple words: An ecosystem is where living things and their environment work together, sharing energy and materials. It has living (biotic) and non-living (abiotic) parts, and its structure includes how many types of life there are and how they are arranged. Its main jobs are moving energy and recycling nutrients.

🎯 Exam Tip: When describing an ecosystem, include its definition, historical context (different terms used), and a clear explanation of its structural (composition, stratification) and functional (energy flow, nutrient cycling) aspects.

Question 4. Explain Universal energy flow model in an ecosystem. Give suitable diagram.
Answer: Universal Energy Flow Model:
E.P. Odum (1983) developed a generalized model by combining both the single-channel model and the Y-shaped model of energy flow. This model illustrates that energy flows through an ecosystem, typically starting with producers and moving through various consumer levels. It accounts for energy inputs, outputs, and losses at each trophic level, showing how energy is utilized and dissipated as it moves through the food web.
The table-like diagram classifying ecosystems is an organizational tool to understand where energy flow occurs:
Basis-Habitat
(i) Terrestrial Ecosystem
1. Forest Ecosystem
2. Grassland Ecosystem
3. Desert Ecosystem
(ii) Aquatic Ecosystem
Types of Water
a. Fresh Water Ecosystem
Nature of Water
* Running Water (Lotic)
1. Spring Ecosystem
2. River Ecosystem
3. Canal (Nullah) Ecosystem
* Stagnant Water (Lentic)
1. Lake Ecosystem
2. Pond Ecosystem
3. Puddle (Pokhar) Ecosystem
b. Marine Ecosystem
(i) Ocean Ecosystem
(ii) Sea Ecosystem
(iii) Estuaries Ecosystem
In simple words: The Universal Energy Flow Model, created by Odum, shows how energy moves through an ecosystem. It starts from sunlight, goes to plants, then to animals, and some energy is lost at each step. This model combines different ways to show how energy flows in nature.

🎯 Exam Tip: For the Universal Energy Flow Model, clearly explain Odum's contribution and mention its key aspects: energy input, transfer through trophic levels, and energy loss. Supplement with examples of ecosystem types for context.