<span>The discoverers of DNA were not James
D Watson and Francis Crick. They are the first scientist to formulate an
accurate description of the DNA’s (deoxyribonucleic acid) complex ,
double-helical structure. They discovered that base pairing nucleotides must
be; adenine and thymine; and cytosine and guanine. These base pairs are held
together by a hydrogen bond, atype of chemical reaction that s easy to break
and easy to reform. The statement is “DNA
is a double helix made of two strands linked together with hydrogen
bonds.”</span>
Answer:
Explanation:
halocline
wind
dissolved salts
ionic
Coriolis
Convection currents flow due to variations in the temperature and salinity in seawater, which both influence its density. Variations in density in different regions of the ocean will cause water to flow from less dense areas to more dense areas as water heats up and becomes less saline, producing a horizontal convection current. Vertical convection currents can arise as cooler, more saline water sinks, causing warmer, less saline water to rise.
Answer:
Oxygen levels stay above 15 percent starting 200 million years ago
Explanation:
Atmospheric oxygen levels are related to the evolution on Earth and changes in geochemical cycles that involve climate variations.
The presence of O
2 and evolution of oxygen gave new opportunities to the life on Earth. Oxygen levels in atmosphere have fluctuated between 15% and 35% of atmospheric volume, since the start of the Cambrian period.
So, form the starting 200 million years ago, oxygen level stay above 15 percent and the correct option is "B".
