Chemicals produced by bacteria that limit the growth of other bacteria are called antibiotics.
Answer:
The correct answer is b. He determined that DNA contains four nitrogenous bases.
Explanation:
Levene was an American biochemist who studied the structure of DNA in the early 1900s and in 1920 he found that DNA consists of four nitrogenous bases that are Adenine, Guanine, Thymine, Cytosine.
He also found deoxyribose sugar and phosphate group and said that nucleotide is the basic unit of DNA which contains a ribose sugar with attached nitrogenous base and phosphate group.
He also concludes that an equal amount of adenine, guanine, thymine, and cytosine makes the DNA which is now known as tetranucleotide hypothesis. So the correct answer is b. He determined that DNA contains four nitrogenous bases.
Answer:
The cells present in the stem are part of the xylem and phloem conductive tissues. They are characterized by being elongated and in tubular form because they transport the substances, the xylem transports water and inorganic mineral sales that the root absorbs from the soil. The phloem is responsible for transporting substances synthesized in photosynthesis.
Its tubular and elongated shape facilitates the transport of these substances
<span>The ash trees are being cut when the show signs of
infestation of the ash borer. Ash borer in particular the Emerald Ash Borer
(EAB) is a tiny bug but can really do a great damage to the tree. When the tree
is infested with the ash borer, they lay their eggs in the bark of tree, when
the eggs hatch the lavas would start eating on the inner tissues of the tree
blocking the flow of nutrients and water in the tree that causes the tree’s to
death. If the tree is infested they cut
it down, burn and bury the wood to stop the spread of infestation. Ash trees
are valued for its strength and elasticity that is often used to make baseball
bats, bows, tool handles and other products that needs durable wood.</span>