Question

9 Lake Erie Food Web RETUR IEL AN RENTAL TUNA N 116 This image is a work of the United States Great Lakes Environmental Research Laboratory(GLERL), taken or made as part of that person's official duties. As a work of the US federal government, the image is in the public domain.

Answer 1

1. a) Producers - Green alga and flagellates

b) Herbivores - Molluscs and mayfly nymph

c) Carnivores - Perch and carp

2. There are 5 trophic levels namely a) Green and light blue colored one - level 1, b) orange one - level 2, c) dark blue - level 3 d) light purple - level 4 e) dark purple - level 5 (left top corner)

3. Carbon cycling in the ecosystem - Carbon is major element which is constituted in all living forms. It is the fundamental element which is found in every macro-molecules like carbohydrates, fats and proteins etc. The three main ways in which Carbon is cycled in an ecosystem include respiration, decomposition and combustion. During respiration, glucose is broken down to give energy and carbon dioxide (therefore, it is released in to the atmosphere as CO₂ gas). In the decomposition, by the action of microorganisms the complex organic molecules along with dead remains of plants and animals are converted into simpler and small molecules which in turn are composed of carbon. Thus, how goes into atmosphere. In the combustion process, matter is burnt in presence of oxygen which in turn releases carbon dioxide which goes in to atmosphere.      

4. a) Oxygen cycle can be explained from the given food web.

Oxygen is one of the most crucial and vital elements to be known till now. It is used in every process like - respiration, photosynthesis, decomposition and combustion.

Respiration - Animals and plants respire by taking oxygen from the atmosphere, while aquatic animals and plants take dissolved oxygen.

Photosynthesis - Plants to make their food, they acquire dissolved (released by the animals) carbon dioxide and prepare their food.  

Decomposition - Dead and decaying animals release carbon dioxide which goes into the atmosphere and the cycle starts again.

b) The other cycle could be carbon cycle.

5. Human activities may have adverse affects on aquatic ecosystem in the following ways:

a) Due to increased vehicular pollution, it is becoming difficult for the animals and plants to sustain their lives as the amount of dissolved in decreasing at an alarming rate due to intermixing with other harmful chemicals.

b) Increases usage of fertilizers and pesticides in the agricultural lands. This lead to biomagnification of harmful chemicals in the aquatic organisms which gets accumulated in the subsequent level as one organism is a prey for another.  

c) Increased killing of animals for varied purposes.