Answer:
Main sequence stars fuse hydrogen atoms to form helium atoms in their cores. About 90 percent of the stars in the universe, including the sun, are main sequence stars. These stars can range from about a tenth of the mass of the sun to up to 200 times as massive.
Stars start their lives as clouds of dust and gas. Gravity draws these clouds together. A small protostar forms, powered by the collapsing material. Protostars often form in densely packed clouds of gas and can be challenging to detect.
"Nature doesn't form stars in isolation," Mark Morris, of the University of California at Los Angeles (UCLS), said in a statement. "It forms them in clusters, out of natal clouds that collapse under their own gravity."
Smaller bodies — with less than 0.08 the sun's mass — cannot reach the stage of nuclear fusion at their core. Instead, they become brown dwarfs, stars that never ignite. But if the body has sufficient mass, the collapsing gas and dust burns hotter, eventually reaching temperatures sufficient to fuse hydrogen into helium. The star turns on and becomes a main sequence star, powered by hydrogen fusion. Fusion produces an outward pressure that balances with the inward pressure caused by gravity, stabilizing the star.
How long a main sequence star lives depends on how massive it is. A higher-mass star may have more material, but it burns through it faster due to higher core temperatures caused by greater gravitational forces. While the sun will spend about 10 billion years on the main sequence, a star 10 times as massive will stick around for only 20 million years. A red dwarf, which is half as massive as the sun, can last 80 to 100 billion years, which is far longer than the universe's age of 13.8 billion years. (This long lifetime is one reason red dwarfs are considered to be good sources for planets hosting life, because they are stable for such a long time.)
Explanation:
I hope this helped!
D. Learned behaviors do not directly affect natural selection because they are not inherited.
This is true because learned behaviors can be taught to the offspring but do not come within them the way instincts do.
Because they will grow really long if you don't
The difficulty with this answer, lies in the fact that not all of land and ocean biomes have been completely explored. The ocean is vast, covering approximately 70% of the Earth's surface, with literally vertical miles or kilometers of depth, and with some areas with sparse to no biodiversity. The same can be said about certain areas of large deserts with very low levels of biodversity, void of life, like vast deserts of the Sahara or Gobi. But, the Amazon rain forest contains still unknown species of plant and animal life, just like the ocean. Because of its vastness, intellectually, I would say the ocean contains more biodiversity, but the answer is scientifically, as of now, yet to be proven one way or the other.
Heart,eyes,blood vessels and skeleton people.
