How do industrial metallic pollutants reach and accumulate in the human body if dumped into rivers? Name the causative agent of cholera. State four features in the leaf which can be used for classific

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22) Industrial wastes may contain metallic pollutants. State how such pollutants may indirectly reach and accumulate in the human body if the wastes were dumped into rivers.
Metallic pollutants from industrial waste dumped into rivers can reach and accumulate in the human body through the following process:

• Aquatic organisms (like algae and small plants) absorb the metallic pollutants from the contaminated water.
• These contaminated organisms are then consumed by small aquatic animals (e.g., fish, shellfish).
• Larger fish or other aquatic predators eat the smaller contaminated animals, leading to an increase in pollutant concentration at higher trophic levels (a process called biomagnification).
• Humans consume these contaminated fish or other aquatic animals, causing the metallic pollutants to accumulate in their bodies over time (bioaccumulation).

23) Name the causative agent of cholera.
The causative agent of cholera is the bacterium $\boxed{\text{Vibrio cholerae}}$.

24) State four features in the leaf which can be used for classification.
Four features in a leaf that can be used for classification are:

1. Leaf arrangement: How leaves are attached to the stem (e.g., alternate, opposite, whorled).
2. Leaf venation: The pattern of veins in the leaf blade (e.g., parallel, reticulate/net-like).
3. Leaf margin: The characteristics of the leaf edge (e.g., entire, serrate, lobed).
4. Leaf shape: The overall outline or form of the leaf blade (e.g., ovate, lanceolate, cordate).