Question

The residents of Nanganallur and Adambakkam wanted to revive an environment park on

AdambakkamEri. The lake needs to be desilted and deepened and a bund is to be formed for a walkers’

path. Moreover, steps are to be taken to prevent the discharge of sewage through storm water drains and

the dumping of garbage on the lake bunds. The environmentalists say that invasive species like water

hyacinth have clogged this water body. Also, the discharge of sewage into the lake has resulted in the

growth of unwanted plants. This is blocking the air-water interface, thereby reducing the dissolved oxygen

in the water and killing a lot of fish. The water bodies clogged by the invasive species also become a

breeding ground for mosquitoes. The State Government has been requested to expedite the works for this

at the earliest.

Question 26:

When an alien species (plant or animal) that does not belong to an ecosystem is introduced, it spreads and

competes with the native plants for space and nutrients and becomes problematic in the absence of

natural enemies. These intruders are called invasive alien species.

What are the ill effects of an invasive species like water hyacinth?

i. Blockage of sunlight from reaching native aquatic plants.

ii. Starving the water of carbon dioxide

iii. Domination and phasing out of fish and other native species.

iv. Change in the water quality with respect to the dissolved oxygen and the water pH due to release

of CO2 .

v. Starving the water of oxygen.

vi. Desilting of the water body

vii. An increase in algae blooms, mosquito infestation due to dense matting and decreased water flow.

a) i , ii, iii, iv, v

b) i, iii, v, vii, iv

c) iii, v, vi, vii

d) iii, iv, v, vi​

Answer 1

Answer:

Option D

Explanation:

Among the various options given regarding the negative impact of water hyacinth (Eichhornia crassipes) on ecological and marine life, the correct options are listed below;

• Domination and phasing out of fish and other native species.
• Change in the water quality with respect to the dissolved oxygen and the water pH due to release of CO2 .
• Starving the water of oxygen.
• Desilting of the water body

Hence option D is the correct one

Answer 2

The ill effects of an invasive species like water hyacinth are b) i, iii, iv, v, vii.

Explanation:

• Invasive species are not native organisms to a particular area. They shift from one place to another and cause harm to the native organisms.
• Water hyacinth is an aquatic plant which is native to Amazon basin. They produce attractive flower with feathery roots floating freely.
• They also affect the environmental and economic trait of a place. These organisms adapt to new places easily.
• These plants grow up to 1 meter which deprives aquatic plants and animals from sunlight. These organisms always out compete the native organisms.
• They absorb major of  the oxygen and increase the mosquitoes.