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.
Transparent materials allow light to pass through freely. translucent lets light pass through, but after the light is scattered.
With the advent of industrialization, several trees have been cut at an alarming rate for raw materials and various other purposes. This felling of trees can be regulated by selective cutting, clear-cutting and shelterwood cutting.
Forest fires are one of the common causes of loss of forests. Sometimes the forest land is set on fire to make the land available for commercial purposes. Once cleared, there can be no vegetation. Natural forest fires are also responsible for the destruction of huge forest covers. Latest fire fighting techniques should be adopted to conserve the forest. However, forest fires are an important part of the ecosystem and it helps replenish nutrients in the soil from dead and decaying matter.
More trees should be planted to increase the forest cover. Trees should be selected according to the geographical conditions of a particular region and proper care should be taken during the growth of trees.
Prevention of exploitation of forestry and forest products is necessary for the conservation of forest.
The existing forests should be protected from diseases by spraying chemicals, antibiotics or development of pest-resistant strains of trees.
