Answer:
By studying the fossil record we can tell how long life has existed on Earth, and how different plants and animals are related to each other. Often we can work out how and where they lived, and use this information to find out about ancient environments. Fossils can tell us a lot about the past.
Explanation:
Answer:
A cell wall
Explanation:
Plant cells are enclosed by a rigid cell wall. When the plant cell is placed in a hypotonic solution , it takes up water by osmosis and starts to swell, but the cell wall prevents it from bursting.
Answer:
Phosphate sugar backbone:
The sugar-phosphate backbone forms the structural framework of nucleic acids, including DNA and RNA. This backbone is composed of alternating sugar and phosphate groups, and defines directionality of the molecule.
Nitrogenous base:
Nitrogen bases are the molecules that make up the steps of the ladders. There are four different nitrogen bases, namely; Guanine, Thymine,Adenine and Cytosine.
Pyrimidines are compounds that make a single 6-sided ring. Examples of pyrimidines are Cytosine and Thymine.
Purines on the other hand make 5-sided and 6-sided rings. Examples of purines are Guanine and Adenine.
The nitrogen bases are helped together through hydrogen bonds.
Hydrogen Bonds:
A weak bond between two molecules resulting from an electrostatic attraction between a proton in one molecule and an electronegative atom in the other.
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