Star is a brilliantly glowing sphere of hot gas whose energyis produced by an internalnuclear fusion process. Stars are contained in galaxies. A galaxy contains not only stars, but clouds of gas and dust. These clouds are callednebulae, and it is in a nebula where stars are born. In the nebula is hydrogen gas which is pulled together by gravityand starts to spin faster. Over millions of years, more hydrogen gas is pulled into the spinning cloud. The collisions which occur between the hydrogen atoms starts to heat the gas in the cloud. Once the temperature reaches 15,000,000 degrees Celsius, nuclear fusion takes place in the center, or core, of the cloud. The tremendous heat given off by the nuclear fusion process causes the gas to glow creating a protostar. This is the first step in the evolution of a star. The glowing protostar continues to accumulate mass. The amount of mass it can accumulate is determined by the amount ofmatter available in the nebula. Once its mass is stabilized, the star is known as a main sequence star. The new star will continue to glow for millions or even billions of years. As it glows, hydrogen is converted into helium in the core by nuclear fusion. The core starts to become unstable and it starts to contract. The outer shell of the star, which is still mostly hydrogen, starts to expand. As it expands, it cools and starts to glow red. The star has now reached the red giant phase. It is red because it is cooler than the protostar phase and it is a giant because the outer shell has expanded outward. All stars evolve the same way up to the red giant phase. The amount of mass a star has determines which of the following life cycle paths the star will take.
Answer:
D.
They break down dead organisms.
Explanation:
Trait approaches to leadership propose that leadership ability arises from distinctive personal characteristics. These personality traits shape personality.
Personality refers to the singular and unique patterns of thoughts, emotions and behaviors that exhibit a person.
The trait approaches represent different methodologies to analyze the personality of a person (for example, his/her leadership skills).
These approaches (trait approaches) put major emphasis on the traits of a person that can be considered markers of personality.
Learn more about personality traits here:
brainly.com/question/6491553
Answer:
Cells from the pure culture can cause disease in healthy individual after infecting it with the pure culture.
Explanation:
Koch postulates says that microbes are the cause of every disease. These microbes can be isolated from the infected host and can be grown outside the host in a pure culture. Then this pure culture is able to cause disease in a healthy host after infecting the host with pure culture. Then this same microbe can again be isolated from the second host.
So Koch postulates which proves that cells from the pure culture can cause disease in healthy individuals after infecting it with the pure culture was the step that enabled Koch to determine that a particular microbe is the cause of the disease because it was causing disease in healthy individual also.
