Answer:
With millions of different kinds of organisms in the world, scientists must find order in all of this diversity. Scientists group living organisms into one or more of a few major categories as part discipline known as taxonomy. The bodies of organisms are organized into functional systems—cells are organized into tissues, and tissues are organized into organs. Body systems carry out critical functions, such as locomotion, reproduction, digestion, and circulation. All living things on Earth are composed of the same carbon-based, molecular building blocks.

The tricuspid valve shuts. This prevents blood from flowing backward into the right atrium while the ventricle contracts. So, your answer will be the Tricuslid Valve. Hope I helped!
Answer:
The process whereby organisms better adapted to their environment tend to survive and produce more offspring. The theory of its action was first fully expounded by Charles Darwin, and it is now regarded as be the main process that brings about evolution.
Four conditions are needed for natural selection to occur: reproduction, heredity, variation in fitness or organisms, variation in individual characters among members of the population. If they are met, natural selection automatically results.