How many insect species are there in 2017?

There are at least 900,000 species, but many more probably have yet to be discovered. Insects all have bodies consisting of a head, a thorax of three segments, usually three pairs of legs and often one or two pairs of wings. Their heads have compound eyes and long antennae that are sensitive to touch and smell.

then that particular organisms become extinct.

what statement best describes the difference between the sympathetic and parasympathetic nervous systems?

the sympathetic nervous system prepares the body for intense physical activity and is often referred to as the fight-or-flight response. the parasympathetic nervous system has almost the exact opposite effect and relaxes the body and inhibits or slows many high energy functions.