Explore Chapter 14: Ecosystems and Energy Flow with Maharashtra Board Class 12 Biology Solutions
Class 12 Biology can be a challenging subject, but with the right guidance, it becomes easier to understand and master. The Maharashtra Board Class 12 Biology Chapter 14 Ecosystems and Energy flow Solutions are a powerful study aid that helps students break down complex topics and prepare thoroughly for both board examinations and competitive entrance tests like NEET and MHT-CET.
Chapter 14, "Ecosystems and Energy Flow," is an important topic that explains the intricate relationships between living organisms and their environment. To simplify learning, detailed step-by-step solutions are provided here in an easy-to-understand format. These solutions are extremely popular among Class 12 students and are perfect for completing homework quickly and preparing effectively for exams.
All questions and answers from Chapter 14 of the Class 12 Biology textbook are available here for free. The YBStudy platform enhances your learning experience with 100% accurate solutions created by experienced biology educators. These expert-designed answers align perfectly with the Maharashtra Board syllabus, making them a reliable resource for academic success.
Maharashtra Board Class 12 Biology Chapter 14 Ecosystems and Energy Flow Solutions
Q1. Multiple Choice Questions
1. Which one of the following has the largest population in a food chain?a. Producers
b. Primary consumers
c. Secondary consumers
d. Decomposers
2. The second trophic level in a lake is________________
a. Phytoplankton
b. Zooplankton
c. Benthos
d. Fishes
3. Secondary consumers are __________
a. Herbivores
b. Producers
c. Carnivores
d. Autotrophs
4. What is the % of photosynthetically active radiation in the incident solar radiation?
a. 100%
b. 50 %
c. 1-5%
d. 2-10%
5. Give the term used to express a community in its final stage of succession?
a. End community
b. Final community
c. Climax community
d. Dark community
6. After landslide which of the following type of succession occurs?
a. Primary
b. Secondary
c. Tertiary
d. Climax
7. Which of the following is most often a limiting factor of the primary productivity in any ecosystem.
a. Carbon
b. Nitrogen
c. Phosphorus
d. Sulphur
Q. 2 Very Short Answer Question.
1. Give an example of ecosystem which shows inverted pyramid of numbers.Answer: Pyramid of number indicates the number of individuals at each trophic level. The pyramid of number is inverted in tree ecosystem. In this, the the first trophic level contains least number of trees.
2. Give an example of ecosystem which shows inverted pyramid of biomass.
Answer: There are two main types of biomass pyramid – inverted pyramid of biomass and the upright one. A good example of the inverted pyramid is in a pond ecosystem where the mass of phytoplankton, the major producers, will always be lower than the mass of the heterotrophs like fish and insects.
3. Which mineral acts as a limiting factor for productivity in an aquatic ecosystem?
Answer: Phosphorus is a limiting nutrient in many terrestrial and aquatic ecosystems. The productivity of the primary producers in these areas is limited, held in check by the amount of available phosphorus that is so vital for life.
4. Name the reservoir and sink of carbon in the carbon cycle.
Answer: Carbon is the chemical backbone of all life on Earth. Most carbon is stored in rocks and sediments, while the rest is stored in the ocean, atmosphere, and living organisms. These are the reservoirs, or sinks, through which carbon cycles. The ocean is a giant carbon sink that absorbs carbon.
Q3. Short Answer Questions
| Upright Pyramid of Biomass | Inverted Pyramid of Biomass |
|---|---|
| 1. Producers are more in biomass than herbivores. | 1. Herbivores have more biomass than producers. |
| 2. Usually seen in terrestrial ecosystems. | 2. Usually seen in aquatic ecosystems. |
| 3. Biomass decreases from producers to top carnivores. | 3. Biomass increases from producers to top carnivores. |
| 4. Energy is transferred efficiently up the pyramid. | 4. Energy transfer appears less efficient. |
| 5. The pyramid of energy is always upright. | 5. Only the biomass pyramid can be inverted; the energy pyramid is never inverted. |
| 6. Example: Forest ecosystem. | 6. Example: Marine ecosystem. |
| 7. The biomass of producers like trees is much larger. | 7. The biomass of producers like phytoplankton is very small. |
| 8. It reflects a stable and sustainable ecosystem. | 8. Often represents short-lived or rapidly reproducing producers. |
| Food Chain | Food Web |
|---|---|
| 1. A single linear path of energy flow. | 1. Consists of many interconnected food chains. |
| 2. Shows a single relationship between organisms. | 2. Shows multiple relationships between organisms. |
| 3. One organism depends on just one food source. | 3. Organisms depend on multiple food sources. |
| 4. Simple and easy to understand. | 4. Complex and more realistic. |
| 5. Example: Grass → Grasshopper → Frog → Snake → Hawk. | 5. Example: Hawk eats frog, mouse, and squirrel; frog eats grasshopper and beetle. |
| 6. Less stable – if one organism is removed, the chain breaks. | 6. More stable – offers alternate paths for energy flow. |
| 7. Incomplete picture of an ecosystem. | 7. Gives a complete view of feeding interactions in an ecosystem. |
| 8. Usually limited to 4–5 trophic levels. | 8. May contain multiple trophic levels with overlaps. |
Q4. Long Answer Questions
1. Define ecological pyramids and describe with examples, the pyramids of number and biomass.Answer: The Ecological pyramid is a graphic representation of the relationship between the organisms of various successive trophic levels for energy, biomass, and number.
A pyramid of biomass is a graphical representation of biomass present in a unit area of various trophic levels. It shows the relationship between biomass and trophic level quantifying the biomass available in each trophic level of an energy community at a given time.
A pyramid of numbers is a graphical representation that shows the number of organisms at each trophic level. It is an upright pyramid in light of the fact that in an ecosystem, the producers are always more in number than other trophic levels. The pyramid of numbers was advanced by Charles Elton in 1927.
2. What is primary productivity? Give a brief description of factors that affect primary productivity.
Answer: Productivity refers to the rate of generation of biomass in an ecosystem. It is expressed in units of mass per unit surface (or volume) per unit time, for instance grams per square metre per day (g/ m2/ day). The mass unit may relate to dry matter or to the mass of carbon generated.
It can be divided into gross primary productivity (GPP) and net primary productivity (NPP). Gross primary productivity of an ecosystem is the rate of production of organic matter during photosynthesis. Plants themselves use a considerable proportion of this GPP for their respiration. Hence, gross primary productivity minus respiratory losses (R) constitute the net primary productivity (NPP).
Net primary productivity is the available biomass for the consumption, to heterotrophs (herbivores, carnivores and decomposers). The annual net primary productivity of the whole biosphere is approximately 170 billion tons (dry weight) of organic matter. Of this, the productivity of the oceans is only 55 billion tons.
Primary productivity (GPP) depends on the plant species inhabiting a particular area. It also depends on a variety of environmental factors, availability of nutrients and photosynthetic capacity of plants. Therefore, it varies in different types of ecosystems.
3. Define decomposition and describe the processes and products of decomposition.
Answer:
Decomposers break down complex organic matter into inorganic substances like carbon dioxide, water and nutrients, and the process is called decomposition.
The important steps in the process of decomposition are fragmentation, leaching, catabolism, humification and mineralization. Detritivores (e.g. earthworm) break down detritus into smaller fragments or particles. This process is called fragmentation.
By the process of leaching, water soluble inorganic nutrients go down (percolate) into the soil horizon and get precipitated as unavailable salts. Bacterial and fungal enzymes degrade detritus into simpler inorganic substances. This process is called as catabolism. It is important to note that all the above steps in decomposition operate simultaneously on the detritus.
Humification and mineralization occur during decomposition in the soil. Humification leads to accumulation of partially decomposed, a dark coloured, amorphous, colloidal organic substance called humus that is resistant to microbial action and undergoes decomposition at an extremely slow rate. Humus formation changes soil texture and increases water holding capacity of soil. Being colloidal in nature humus serves as a reservoir of nutrients. The humus is further degraded by some microbes and release of inorganic nutrients occurs by the process known as mineralisation.
Decomposition as a process requires oxygen. Temperature and soil moisture are the most important factors that regulate decomposition indirectly to help soil microbes. Warm and moist environment favours decomposition whereas low temperature and anaerobic conditions inhibit decomposition.
4. Write important features of a sedimentary cycle in an ecosystem.
Answer: Sedimentary cycles have their reservoirs in the Earth’s crust or rocks. Nutrient elements are found in the sediments of the Earth. Elements such as sulphur, phosphorus, potassium, and calcium have sedimentary cycles.
Sedimentary cycles are very slow. They take a long time to complete their circulation and are considered less perfect cycles. This is because during recycling, nutrient elements may get locked in the reservoir pool, thereby taking a very long time to come out and continue circulation. Thus, it usually goes out of circulation for a long time.
5. Describe the carbon cycle and add a note on the impact of human activities on the carbon cycle.
Answer:
The carbon cycle is the process in which carbon travels from the atmosphere into organisms and the Earth and then back into the atmosphere. Plants take carbon dioxide from the air and use it to make food. Animals then eat the food, and carbon is stored in their bodies or released as CO2 through respiration.
All life forms on Earth are carbon-based because carbon is the main component of all the organic compounds of protoplasm. It constitutes 49% of the dry weight of organisms. If we look at the total quantity of global carbon, we find that 71% carbon is found dissolved in oceans. This oceanic reservoir regulates the amount of carbon dioxide in the atmosphere.
Human activities have a tremendous impact on the carbon cycle. Burning fossil fuels, changing land use, and using limestone to make concrete all transfer significant quantities of carbon into the atmosphere. The ocean absorbs much of the carbon dioxide that is released from burning fossil fuels.
