Ecology 2nd Paper Practical PDF

# Chapter 4: Study of Pond Ecosystem ## Ecosystem Any organism has a close relation with the abiotic substances of its surrounding environment. Organisms and environment exchange substances from one another. No organism can pass its life alone; one has to remain dependent on others for something....

# Chapter 4: Study of Pond Ecosystem ## Ecosystem Any organism has a close relation with the abiotic substances of its surrounding environment. Organisms and environment exchange substances from one another. No organism can pass its life alone; one has to remain dependent on others for something. Organisms and non-living substances affect the existence of one another, and they are both responsible for saving life on Earth. For example, holozoic animals remain dependent directly or indirectly on plants, whereas holophytic animals receive raw materials from the environment. After the death of living animals, microbes convert the degraded body into organic and inorganic constituents. Thus, the loss of abiotic substances is compensated. ## Definition of Ecosystem According to A.G. Tansley, an ecosystem includes both biotic and abiotic environments. Both environments are dependent upon each other. The dependency of biotic and abiotic environments upon one another is called an ecosystem. ## Components of Pond Ecosystem An ecosystem consists of two components: ### 1. Abiotic Component These can be divided into the following parts: * **Climatic:** Such as water, temperature, light, humidity, etc. * **Inorganic Matters:** These can be further divided into: * **Macro-nutrients:** Such as C, H, O, N, P, K, Mg, Ca, Fe, S. * **Micro-nutrients:** Such as Zn, Mn, Cu, Mo, B, Al. * **Gases:** Hydrogen, Oxygen, Nitrogen, Carbon dioxide, Ammonia, etc. * **Organic Substances:** These are helpful in establishing relations between abiotic and biotic components, for example: Proteins, Carbohydrates, and Lipids, etc. Abiotic constituents in a pond ecosystem are water, carbon dioxide, calcium, nitrogen, phosphorus, and amino acids, etc., which either remain dissolved in water or settle down undissolved on the bottom of the pond. ### 2. Biotic Components These can be divided into two parts: #### (A) Autotrophic Components These organisms synthesize food through inorganic substances. These include aquatic plants which synthesize food by inorganic substances such as CO₂ and water in the presence of chlorophyll and sunlight. This process is called **photosynthesis**. The chemical reaction for photosynthesis is: _{&nbsp;&nbsp;&nbsp;&nbsp;}$6CO_2+12H_2O \xrightarrow{Chlorophyll} C_6H_{12}O_6 + 6H_2O+6O_2 $_{&nbsp;&nbsp;&nbsp;&nbsp;}<br/> _{&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;}$sunlight$ Energy remains stored in food substances. This component is called **producer** (green plants in a pond are producers, the food synthesized by them is sufficient for all the organisms. The producers of plants have been divided as follows: 1. **Phytoplankton:** These are very minute and found on the surface of the pond. Their presence makes the pond water green. These are found abundantly upto the depth where sunrays penetrate the water, e.g., Eradrina, Volvox, Microcystis, Anabaena, Euglena, etc. 2. **Filamentous algae:** These are usually found on the water surface, such as Chara, Oedogonium, Spirogyra, etc. 3. **Emergent rooted plants:** These are surface floating rooted plants, such as Typha, Acorus. 4. **Submerged rooted plants:** The roots of these plants remain attached with the bottom, therefore these plants are fixed. e.g., Vallisnaria, Otelia. Some submerged plants are rootless, such as Utricularia, Ceratophyllum, Hydrilla. 5. **Surface floating rootless plants:** Some surface floating plants are also found in the pond, such as Pistia, Lemna, Wolffia, Ipomoea, Jussiaea. #### (B) Heterotrophic Components These are those components which remain dependent upon the food synthesized by producers or autotrophic components. These are called **consumers** and **decomposers**. These components rearrange the complex chemical substances and decompose them. It can be divided into the following components: **(a) Consumers:** The organisms which use the food synthesized by producers are called consumers. These can be divided into three types: 1. **Primary consumers or herbivores:** These include those consumers, which remain depend for their food only on vegetation. Thus, they directly obtain their food from the producers. * **Zooplankton:** These are those microbes which float on the surface of pond water with waves arising in the pond, such as Heliozoans, Copepods, Dinoflagellates, etc. * **Nektons:** These are free-living organisms which swim in between water surface and bottom. They have well-developed locomotory organs, such as Gastropods. * **Benthos:** These organisms pass their lives on the bottom of the ponds. These are creeping animals, such as Gastropods. 2. **Secondary consumers:** These are primary carnivores which feed upon the primary consumer or herbivore consumers to get the food. * In a pond, small fishes and predaceous bugs are secondary consumers. 3. **Tertiary consumers:** These are those animals which feed upon the primary carnivore or secondary consumers to get the food. These are also called top consumers. Big carnivore fishes are tertiary consumers in a pond. **(b) Decomposers:** These are those microbes which decompose the complex organic substances of the dead bodies of top consumers into simple physical elements. These physical elements again mix up with air and soil. The energy produced in the process of decomposition is used in the growth and reproduction of decomposers. The decomposers of a pond includes bacteria and fungi which decompose the complex organic substances of dead bodies of plants and animals into simple substances. These simple substances mix up in the pond water which is taken by aquatic plants in their diet, and thus the ecosystem continues. ## Study of Pond Ecosystem _The image shows a schematic representation of a pond ecosystem with the following features:_ - **Producers** (algae and aquatic plants) use sunlight for photosynthesis. - **Primary Consumers** (herbivores like zooplankton and small fishes) feed on producers. - **Secondary Consumers** (carnivores like larger fishes) feed on primary consumers. - **Tertiary Consumers** (top predators like larger fishes) feed on secondary consumers. - **Decomposers** (bacteria and fungi) break down dead organisms and waste, releasing nutrients back into the ecosystem. _This cycle demonstrates how energy flows through the ecosystem, showing the interdependence of all components._