Answer:
C. At least five mass-extinction events have occurred during the last 500 million years.
Explanation:
- The history of mass extinct is related to the five mass extinctions that are caused over by the 350 million years n which many species have disappeared in there short geologic time.
- A massive extinction is caused in the Permian Triassic extinction event i.e about 250 mn years ago which on an estimate has killed 90% of the species.
- The Cretaceous–Paleogene extinction event that occurred over 66 million years ago is known to have wiped out the dinosaurs and many other species.
Answer:
True, polar covalent bond
Explanation:
A covalent bond is one of the types of the chemical bond which is formed when the electrons are shared between the two atoms.
Based on the magnitude of the sharing of electrons between atoms two types of covalent bonds are formed which are: pure covalent bond in which the electrons are shared equally whereas the polar covalent bond in which the electrons are shared unequally between two atoms.
Since there is a type of covalent bond formed which has unequal sharing of electrons called polar covalent bond therefore true is the correct answer.
Aneuploidy can result in the final daughter cell if the spindle fibers fail to pull a chromosome toward the pole as in case of non-disjunction.
Explanation:
Aneuploidy is a condition which arises when one or more chromosome is missing in the final daughter cells.
Non-disjunction refers to the failure of chromosomal or chromatid segregation or separation during cell division. This results in erroneous meiosis or mitosis leading to the formation of final daughter cells or gametes with an extra or missing chromosome. This condition is aneuploidy.
Failure of separation or segregation of:
- Homologous chromosomes occur in Anaphase I, affects four daughter cells.
- Sister chromatids during Anaphase II, affects two daughter cells
This failure of separation leads to aneuploidy chromosomal abnormalities like monosomy, trisomy, etc which can cause diseases like Down’s syndrome, Turner’s syndrome etc.
Answer<u>:</u><em><u>C. Population size determines water demand</u></em>
Explanation:Population size determines water demand. Water is needed for household use, sanitaion,farming, and industrail use,so when the population increases,water demand increase.
<em>Hope this is right(-)-) </em>
<em><u>For study island</u></em>
