Herpes simplex virus 1 (hsv-1), infects humans and produces most cold sores. the virus is contagious. herpes simplex can be spread through contact with saliva, such as sharing drinks. hsv-1 persists in the body by becoming latent and hiding from the immune system in the cell bodies of neurons. after the initial or primary infection, some infected people experience sporadic episodes of viral reactivation or outbreaks. how would scientists with viewpoint #1 respond to the description the herpes virus? a) a virus is alive because it causes disease. b) a virus is not living; it responds to chemical changes in the environment. c) a virus is alive; it can respond and/or adapt to changes in the environment. d) a virus is not living; it has no genetic material and does not undergo division.

Ans. (C). A virus is alive; it can respond and/or adapt to changes in the environment.

Viruses are connective links between living and non-living things as they show characteristics of both. Viruses can be considered as living inside the host body, where they use host machinery to replicate their own genetic material and make their progeny.

Viruses can be respond to changes in their surrounding environment as other living organisms and adapt to those changes. For example, herpes simplex virus 1 becomes adapt to responses shown by immune system of host.

Thus, the correct answer is option (C).

the oldest known insects are believed to live around 400 millions ago as suggested by the fossil records.   some plants having woody stems also evolved during this time.

after the evolution of insects the first four legged species or the tetrapods evolved in shallow freshwater habitats from the intermediate species approximately 397 million years ago. the tetrapods went on conquering the land giving rise to amphibians, reptiles, mammals and birds.

the major split in tetrapods first occurred 340 million years ago branching off from amphibians.

363 million years ago when the carboniferous period began the insects started roaming on land and taking flights, following which the four limbed tetrapods adapted in the terrestrial habitat.