Explain the importance of fossils.

Explanation

(i) Parasitic adaptation of Leech:
(a) Blood is sucked by pharynx
(b) The salivary glands produce hirudin which does not allow the blood to coagulate.
(c) Anterior and posterior ends of the body are provided with suckers by which the animal attaches itself to the body of the host.
(ii) Importance of Fossils:
(a) Fossils are useful in classification of plants.
(b) Fossils throw light on phylogeny and evolution of plants
(c) Fossil plants give a historical approach to plant kingdom
(d) Fossil plants can be used in the field of descriptive and comparative anatomy