SOME IMPORTANT QUESTIONS REGARDING ECOSYSTEM CLASS 12

 1. Add a short note on Pyramid of biomass , energy and number .

Ans:-      The relationship between numbers, biomass, energy or bio productivity of different trophic levels in an ecosystem can be represented by a pyramid known as the ecological pyramid or Eltonian pyramid. The ecological pyramids show the energy flow in the system.

A biomass pyramid is the representation of total living biomass or organic matter present at different trophic levels in an ecosystem. Biomass is calculated as the mass of living organisms present at each trophic level in a given sample size. It can be represented as dry weight in grams or calories per unit area. A bomb calorimeter is used to measure biomass. Trophic level is the specific place that a living organism occupies in a food chain. In a biomass pyramid, producers (1st trophic level) are at the base, followed by herbivores (primary consumers) and then carnivores (secondary and tertiary consumers) at the top. The pyramid of biomass shows the flow of energy from producers to consumers. We know that only 10 per cent of the energy gets transferred to the next trophic level and the rest is either utilised for metabolic processes or excreted out.

An energy pyramid, also known as a trophic or ecological pyramid, is a graphical representation of the energy found within the trophic levels of an ecosystem. The bottom and largest level of the pyramid is the producers and contains the largest amount of energy. As you move up the pyramid, through the trophic levels to primary, secondary and tertiary consumers, the amount of energy decreases and the levels become smaller. While energy can not be created or destroyed is it released as heat within each level. Approximately only 10% of energy is passed from one level to the next.

This Pyramid shows the numbers of the producers, herbivores and the carnivores at their successive trophic levels. This pyramid can be either upright, or inverted or partially upright.

Pyramid of numbers in grassland Ecosystem

In a grassland ecosystem, the number of producers (mainly grasses) is always maximum, followed by decreasing numbers at second trophic level (herbivores), third trophic level (carnivores) and least number of apex predators. Thus, a pyramid of numbers in grassland is upright.

Pyramid of Numbers in Pond Ecosystem

In a pond ecosystem, the producers are Phyto-planktons such as algae, bacteria etc. They are maximum in number. The small herbivorous fishes, rotifers etc. are smaller in number than producers , while the small carnivorous fishes are even less in number. Finally, the apex consumers or biggest carnivorous fishes are least in number. Thus, the Pyramid of numbers in a Pond Ecosystem is also upright.

2. Define ecological succession. Write the parts of succession with the help of flowchart.

Ans:-  It is the process of evolution of a species in a steady and gradual manner in a region over a period of time. It can also be described as the sequence of colonization of species in an ecosystem form a barren region. It is a course of evolution in the species with the development of the biological area over a long run starting from:

Pioneer Species –> Intermediate Species –> Climax Specie... 

Stages of Ecological Succession

Clements (1916)$(1916)$ has discussed the process of ecological succession. This process involves the following stages, which are as follows:

1. Nudation: Development of bare area or nudation without any form of life. It may be caused due to several factors like volcanic eruptions, landslides, floods, erosion, earthquake, forest fire, the spread of disease, etc.
2. Invasion: It is the successful establishment of a species in a barren area. The arrival of reproductive bodies or propagules of various species and their settlement in the new or bare area occurs by air, water, etc., known as migration. Adjustment of establishing species with the prevailing conditions is known as ecesis. Then the individual species are multiplied by reproduction and increase their numbers; this is called aggregation.
3. Competition and coaction: After aggregation, the individuals of a species compete with other organisms for food, space and other resources. The intraspecific and interspecific competition takes place along with interaction with the environment. New invasion by plants and animals takes place.
4. Reaction: The modification of the environment through the influence of living organisms on it is called reaction.
5. Stabilisation (Climax): The stage at which the final or climax community becomes more or less stabilised for a longer time in that particular environment is known as stabilisation.

3. What is GPP and NPP ?

Ans:-Gross primary productivity (GPP) refers to the rate of production of organic matter during photosynthesis.

Net primary productivity :
Net primary productivity (NPP) refers to the remainder of the gross production which is left after its use by the producers or plants in the process of respiration. Net primary productivity is the biomass that is available to the heterotrophs in an ecosystem for consumption.
Hence, NPP = GPP - Biomass lost due to respiration by plants

 NPP = GPP – Plant respiration

4.Distinguish between food chain and food web .

Ans:-

Difference Between Food Chain And Food Web
Food Chain	Food Web
A linear pathway showing the flow of energy	A multitude of networks showing the flow of energy
An organism of higher level trophic feeds on a specific organism of lower trophic level	An organism of a higher trophic level has access to more members of a lower trophic level.
Does not affect the adaptability and competitiveness of organisms.	It has a role in improving the adaptability and competitiveness of an organism.

To Summarize

A food chain is a basic network that shows the linear flow of nutrients and energy from one trophic level to another. A food web is a multitude of interconnected food chains at many trophic levels. Furthermore, a food web accurately represents all the various food chains that exist in an ecosystem

.5.Write the Lindemann's 10% law of energy flow.

Ans:-

1. Lindemann gave the ten percent law in 1942.
2. This law states that only 10 percent of energy in a food chain out of the total energy is transferred from one trophic level to another.
3. The rest of the energy is utilized for other metabolic processes and some are released as heat.

6.Write the features of energy flow in an ecosystem .

Ans:-

1. The energy flow is unidirectional and linear. It means energy can flow in a fixed direction, from lower levels to higher levels. i.e., $\mathrm{Producers}\to \mathrm{Primary}\mathrm{consumers}\to \mathrm{Secondary}\mathrm{consumers}\to \mathrm{others}$.
2. The 10% law. Only 10% of the total energy present in a level is transferable to the higher levels. The rest is lost to the surroundings in form of community heat.
3. Due to the 10% Law, we can say that the longer the food chain the least energy is obtained by the top-level consumer

7.Define inverted pyramid.

Ans:-An inverted pyramid is formed when the number of individuals or biomass is minimum and increases at each trophic level. The pyramid of biomass in a pond ecosystem is an example of an inverted pyramid because the biomass of phytoplankton may be smaller than that of zooplankton.

8.Mention the importance of carbon cycle and phosphorus cycle.

Ans:-The carbon cycle is vital to life on Earth. Nature tends to keep carbon levels balanced, meaning that the amount of carbon naturally released from reservoirs is equal to the amount that is naturally absorbed by reservoirs. Maintaining this carbon balance allows the planet to remain hospitable for life. Scientists believe that humans have upset this balance by burning fossil fuels, which has added more carbon to the atmosphere than usual and led to climate change and global warming.

The phosphorus cycle matters because phosphorus is an essential nutrient for sustaining life on Earth, where it plays a central role in the transfer of energy within organisms, the structure of the genetic material, and in the composition of cell membranes, bones and teeth.

9.State the roles of decomposer in ecosystem.

Ans:-

1. Decomposers in ecosystems act as environmental cleaners by decaying dead plants and animals.
2. They aid in the recycling of nutrients.
3. They make room for a new life in the biosphere by decaying the dead.
4. They contribute to the reintroduction of different elements into moisture, soil, and air for reuse by producers such as crop plants

10.Mention the components of ecosystem with the help of flowchart.

Ans:-

There are two main components of an ecosystem which are in constant communication with each other.  They are the biotic components and the abiotic components.

Biotic Components of Ecosystem

The living components of an ecosystem are called the biotic components. Some of these factors include plants, animals, as well as fungi and bacteria. These biotic components can be further classified, based on the energy requirement source. Producers, consumers, and decomposers are the three broad categories of biotic components.

• Producers are the plants in the ecosystem, which can generate their own energy requirement through photosynthesis, in the presence of sunlight and chlorophyll. All other living beings are dependent on plants for their energy requirement of food as well as oxygen.
• Consumers include herbivores, carnivores, and omnivores. The herbivores are the living organisms that feed on plants. Carnivores eat other living organisms. Omnivores are animals that can eat both plant and animal tissue.
• Decomposers are the fungi and bacteria, which are the saprophytes. They feed on the decaying organic matter and convert this matter into nitrogen and carbon dioxide. The saprophytes play a vital role in recycling the nutrients so that the producers i.e. plants can use them once again.

Abiotic Components of Ecosystem

Abiotic components are the physical and/or the chemical factors that act on the living organisms at any part of their life. These are also called as the ecological factors. The physical and chemical factors are characteristic of the environment.  Light, air, soil, and nutrients, etc. form the abiotic components of an ecosystem.

The abiotic factors vary from ecosystem to ecosystem. In an aquatic ecosystem, the abiotic factors may include water pH, sunlight, turbidity, water depth, salinity, available nutrients and dissolved oxygen. Similarly, abiotic factors in terrestrial ecosystems can include soil, soil types, temperature, rain, altitude, wind, nutrients, sunlight etc.

Here, the sun is the energy source. Producers/plants use this energy to synthesize food in the presence of carbon dioxide and chlorophyll. The energy from the sun, through several chemical reactions, turns into chemical energy.