Answer:
It allows water and other molecules to enter and exit the system.
Explanation:
Plants have both a cell membrane and a cell wall. These allow needed molecules, such as water, to enter the cell. Both the cell wall and the cell membrane are semi permeable, which means that they choose what can enter and leave the cell. Molecules like water and other useful things to the cell enter it, and things such as waste leave the cell through the membrane and wall.
Remember that only plant cells have cell walls. Animal cells only have a cell membrane. But both the wall and membrane have the same purpose.
Answer:
A. A change in the gene pool over time
Explanation:
The evolution is the change in the gene pool over time. Therefore, the option (A) is the correct answer.
Answer:
Viruses: stay the same
Infected cells: Increase
Unaffected cells: decrease
Explanation:
DNA is composed of nucleotides, which are composed of three parts:
1. A five carbon carbohydrate (pentose)
Pentose is classified as a monosaccharide (simple carbohydrate), and its molecular formula is represented by
. They are water soluble molecules with sweet taste. Monosaccharides may have from three carbon atoms (trioses) to six (hexoses). In DNA is present pentose (5 carbon atoms)
2. A nitrogenous base
Nitrogenous bases are ring-shaped compounds that contain nitrogen in their molecular structure. They are classified into two groups: purines and pyrimidines
The purine bases are adenine (A) and guanine (G). They are larger and contain more than one ring in their structure,.
The pyrimidines, cytosine (C), uracil (U) and thymine (T), are smaller and composed of a single ring.
3. One or more phosphate groups
A phosphate consists of a trivalent anion that contains one phosphorus atom and four oxygen atoms. Its molecular formula is expressed by
.