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:
This represent the flow of energy.
lil more info:
The placement of the arrows in a food chain or food web is very important. The arrows always show the direction of the energy as it is transferred from one organism to another. The flow of energy can also be represented within an energy pyramid.
Answer:
esta es una expresión de admiración ante la belleza de los mecanismos evolutivos
Explanation:
El concepto de evolución como mecanismos naturales que está actualmente en boga fue originalmente planteado por Charles Darwin en su celebre publicación "El origen de las especies" (1859). La teoría de la evolución de Darwin está basada en la idea que las especies cambian constantemente con el tiempo a través del proceso de selección natural. Este mecanismo es responsable de la inmensa biodiversidad biológica observada en la naturaleza, la cual incluye la evolución de las especies, poblaciones y organismos individuales. Desde una perspectiva biológica, es imposible no quedar fascinado ante la naturaleza y contemplación de los procesos evolutivos.
Symptoms usually appear 30–60 minutes after eating toxic shellfish and includenumbness and tingling of the face, lips, tongue, arms, and legs. There may beheadache, nausea, vomiting, and diarrhea.
