The nucleus of an atom contain protons and neutrons, which make up most of the mass of an atom.
The answer would be 2 and 3 ( 2nd answer choice)
Cell walls are supporting structures that help the plant to have a fixed shape and protect it from injury. Other than that, it helps to keep the plant turgid so that it can stay firm and upright. Because when it enters a high water potential solution, as water moves in, the water exerts turgor pressure on the cell wall and the cell wall thus exerts an opposing pressure to keep water out. Hence cell wall is needed for the plant.
On the other hand, animal cells do not need to keep the structures, as they have the skeletal system to protect the organs and cushion them against any
external injuries.
I hope that helped
<span>The two main sources that lead to increased genetic variation are:
</span>1. Gamete mutations
2. Recombination.
Gamete mutations:
Gametic mutations are the mutations that occur in germline cells (sperm and egg). Due to this, the mutations are able to be passed on from one generation to another. One of the most famous gametic mutations<span> is hemophilia.
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Recombination:
Genetic recombination is the production of offspring with combinations of traits that differ from those found in either parent.
Sloths (three-toed), chameleons