Skin is the first line of defense mechanism of our immune system. It acts as a barrier for pathogenic and opportunistic microorganisms. However, skin itself has a microbiota that does not allow other microorganisms to invade or colonize. Any wound, cut or change in the pH of skin due to environmental conditions or any disease might lead to the entry of the opportunistic microorganisms inside the skin. This leads to several skin disorders such as dermatitis, eczema, cellulitis, warts, etc. Thus, it is extremely important to keep the skin hydrated and healthy to avoid any kind of microbial invasion.
Lithosphere is the final layer on the planet Earth, erosion caused by wind (atmosphere) or rain (hydrosphere) may also wear down rocks in the lithosphere.
Answer: The blanks can be correctly filled up with prophase I and metaphase II.
Explanation:
In females, finite number of oocytes are present since birth. The process of oogenesis initiate in embryonic stage only. However, oogonia divide and mature to form primary oocytes. These primary oocytes start meiotic division but arrest in prophase I stage before birth.
After a girl attains puberty, one primary oocyte resumes its division each month during a menstrual cycle. The primary oocyte divides to form secondary oocyte and polar body.
Polar bodies degenerate after completing meiosis II. However, secondary oocyte halts its division again at metaphase II until fertilization takes place. Once fertilization takes place it completes its meiosis II and results into mature ovum and polar body.
Hereditary mutation - may be passed to another generation, occurs in gametes, variation that may enhance survival.
Somatic mutation - not passed from generation to generations, occurs in body cells.
Both- changes in DNA.
<h3><u>Explanation:</u></h3>
Mutations are defined as sudden changes in DNA that takes place by changing a particular nucleotide or a portion of DNA, or even a whole chromosome which has potential to change characters of an organism. Mutation was first proposed by Hugo de Vries who is also known as the Father of Mutation Theory.
Mutations can occur in any cell of body. It may occur in somatic cells, or in germ mother cells. But the mutations that occur in germ mother cells are actually the mutations that are carried forward by the gametes into next generations. Mutation in somatic cells get obliterated as the organism dies. And the Mutation in gamete cells are those mutations which are capable to cause variations in progenies which can led to better survival of the progenies.
