Elephantiasis is caused by

State reasons for the following:
$(i)$ Tapeworms do not have a digestive tract.
$(ii)$ Frogs have both skin and lungs for breathing.
$(iii)$ $A$ whale is a mammal,not a fish.

Name two plants for each of the following types:
$(i)$ Vascular cryptogams
$(ii)$ Naked seeded plants
$(iii)$ Flowering plants

On the basis of the following features,identify the group and give one example of each:
$(i)$ Presence of notochord at some stage of life.
$(ii)$ Unicellular,microscopic,and eukaryotic.
$(iii)$ Seeds are enclosed in fruits.

Which among the following is exclusively marine?

$A$ student enters the museum and observes the animal specimens. He looks at the one marked 'whale' and calls it a type of fish. How will you explain to him that whales and fishes belong to two different classes? List any three distinguishing features to justify your statement.