Trisomy 21 (nondisjunction) Down syndrome is usually caused by an error in cell division called "nondisjunction." Nondisjunction results in an embryo with three copies of chromosome 21 instead of the usual two. Prior to or at conception, a pair of 21st chromosomes in either the sperm or the egg fails to separate.
No never ! Virus will never have a cell wall but it does have a protein capsule !
Hey there!
Let's start with the first blank. The ozone layer starts in the stratosphere and is made of ozone gases made to protect the Earth from the Sun's harmful UV rays. If the ozone layer wasn't there (not to mention the rest of the atmosphere), we would be exposed to that kind of radiation. Thereofe, "Ultra violet rys would not be <u>blocked</u> by the ozone layer."
For the next one, a lot of levels of substances in the air would change, like UV and oxygen- as there would be more radiation from the lack of protection and all the oxygen would escape.
Hopefully this helps!
<span>Alfred Wegener proposed the theory of continental drift at the beginning of the 20th century. His idea was that the Earth's continents were once joined together, but gradually moved apart over millions of years.</span>
Answer: Confined aquifers tend to be much less vulnerable than unconfined ones, and deeper aquifers are less vulnerable than shallow ones. Steeper slopes mean that surface water tends to run off rather than infiltrate; and this can reduce the possibility of contamination.
Explanation: Learned this in school, no biggie though