A plant fossil is any preserved part of a plant that has died long back. Fossils may be a prehistoric impression that may be hundred to millions of years old. Majority of the plant fossils are disarticulated parts of plants, it is rare to find plants to be preserved as whole.

The organisms which live in extreme environmental conditions on earth are called extremophiles.

Importance of Ethnobotany
(i) It provides traditional uses of plant.
(ii) It gives information about certain unknown and known useful plants.
(iii) The Ethnomedicinal data will serve as a useful source of information for the chemists, pharmacologists and practitioners of herbal medicine.
(iv) Tribal communities utilize Ethnomedicinal plant parts like bark, stem, roots, leaves, flower bud, flowers, fruits, seeds, oils, resins, dyes, gum for the treatment of diseases like diarrhoea, fever, headache, diabetes, jaundice, snakebites, leprosy, etc.

Paleobotany is derived from Greek words paleon that means "old" and botany the study of plants. It is the branch of Paleontology that deals with recovery and identification or plant remains of geological past.

Vermiform appendix, Nictitating membrane, Caudal Vertebra and Coccyx.

(i) According to this theory life originated spontaneously from lifeless matter.
(ii) It was believed that fishes originated from mud, frogs from moist soil and insects from decaying matter.

Extraterrestrial or Cosmic orgin: Some scientists still believe that life came from outer space. This states that units of life called spores (Panspermia) were transferred to different planets including Earth. This is still an idea of some Astronomers.

Palaeontology.

Archaeopteryx.

Homologous organs.