The promise of jobs and prosperity, among other factors, pulls people to cities. Half of the global population already lives in cities, and by 2050 two-thirds of the world's people are expected to live in urban areas. But in cities two of the most pressing problems facing the world today also come together: poverty and environmental degradation.
<span>Like the sporophytes of seed plants, those of ferns consist of stems, leaves androots. Stems: Fern stems are often referred to as "rhizomes", even though they grow underground only in some of the species.</span>
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.
Copied but correct answer.
Answer: C (She hasn't fastened the slide to the stage
Explanation:
In Microscopy even if the slide is not yet in focus,she will be able to see part of the slide which may appear as transparent image.Therefore this is a wrong answer.
If the microscope is not plugged it light can not come up.
If there are no specimen on the slide,the slide will still as transparent image at the focus.
No doubt Stella forgot to fasten the slide to the stage.,therefore the specimen on the slide was not in focus of the objective lens,rather she was focusing on the stage only,hence the visible white light.
Populations tend to grow because of repopulation.
