The impact of asteroids and volcanic eruptions
Answer:
A single nucleotide polymorphism (SNP) is the most common gene variation found among people. A SNP represents a change in a single DNA block, called a nuecleotide, being able, for example, to replace a nucleotide cytosine (C), with a nucleotide thymine (T), guanine (G) or adenine (A) in the genome. They represent the 90% of all the human gene variations.
Explanation:
B. carbon dioxide
C. oxygen
D. nitrogen
Answer:
B. carbon dioxide is the correct answer.
Explanation:
The greenhouse effect is caused by human activities like cutting the forest and fossil fuel burning, increase the level of carbon dioxide gas(greenhouse gases) and creates global warming.
When the fossil fuel is burned carbon combines with oxygen to form Carbon dioxide and it increases the concentration of greenhouse gases and give rise to global warming.
The Greenhouse gases Carbon dioxide traps the radiating heat from the Earth, this heat is absorbed in the form of infrared radiations and the radiation is emitted which warmer the lower atmosphere and Earth surface,this result in melting of ice sheets, glaciers and warming the ocean
Thus carbon dioxide greenhouse gases which creates global warming.
Answer: C. Homologous chromosomes are separated in meiosis but not in mitosis.
Explanation: There are two main types of division that take place in eukaryotic cells, mitosis, and meiosis. Mitosis is the type of division that is used for growth, repair, and replacement of tissues. Therefore it is not necessary that the cells have different chromosome numbers or are varied genetically in the daughter cells in the case of mitosis.
Meiosis is the division that takes place to form the gametes for sexual reproduction. It is important in the first stages of meiosis I, to introduce variation and to halve the chromosome number.
Chromosomes numbers are halved (from 46 to 23) during meiosis I because the gametes (sperm and egg) come together and fuse during fertilization to form a zygote. When this fusion occurs (23 from the zygote and 23 from the egg), the chromosome number needs to be returned to that of the parent cell (46).
At the end of meiosis, four genetically unique cells are produced with half the number of chromosomes as the parent cell (23 cromosomes) . After the process of mitosis is completed, two cells genetically identical to each pther are produced and have the same number of chromosomes as the parent cell (46 cromosomes).
Genetic variation is actually important because of changing environmental conditions.
B) cold winters and cool summers.
C) located in the northern hemisphere.
D) a layer of frozen soil called permafrost.
Answer:
The correct answer would be A) many coniferous trees.
Taiga and tundra represent the two coldest biomes of the land on the planet.
The average annual temperature of taiga lies between 41° Fahrenheit and 23° Fahrenheit whereas the temperature of the tundra lies below 23° Fahrenheit throughout the year.
It makes the major difference between the plant life of the two biomes. The taiga is characterized by the presence of coniferous forests which consist of spruces, pines, and larches.
In contrast, vegetation in the tundra is mainly composed of grasses, shrubs, mosses, sedges, and lichens.