About 20 minutes<span>Sperm can live outside of the body for only about 20 minutes
to an hour, depending on how exposed the semen is to the air and other
environmental factors. To avoid the slightest risk of pregnancy, a woman
should make sure that ejaculated semen doesn't get at all close to her
vagina.</span>
Answer:
Explanation:
Meiosis is a form of cell division that occurs in the sex cells of organisms. It ensures the reduction of a diploid cell to an haploid cell to allow for the formation of a diploid zygote after fertilization (contribution of both parents haploid sex cells to give a diploid zygote). Thus, this process is very essential and important.
The reduction is accomplished by 2 divisions after the duplication of chromosomes
- first division: separation of homologous pairs of chromosomes (this reduces the total in half)
- second division: separation of sister chromatids of a chromosome.
The rearrangement in meiosis occurs by crossing over/genetic recombination.
This is the exchange of genetic material between homologous pairs of chromosome bringing about a rearrangement and genetic variation
An example of a chromosomal abnormality that arises as a result of defects in this process is the Down Syndrome which is caused by a nondisjunction of the chromosomes 21 pair in a sex cell.
This condition produces offsprings that have some characteristic facial features, short stature etc
Step One - Obtain a clean microscope slide.
Step Two - Place a drop of liquid on the slide. This is the “wet” part of the wet mount. The liquid used depends on the type of cell being viewed:
If examining a plant cell, tap water can be used.
If examining an animal cell, physiological saline (or contact lens solution) must be used, because if plain water is used, the cell will explode from osmotic pressure. Unlike plant cells and bacteria, animal cells have no cell wall to structurally support them.
Step Three - Obtain the specimen to be used. Some introductory biology classics for viewing include:
Skin of an onion bulb: In order to view the cells, a very thin layer of skin must be obtained. Take a single layer of onion and bend it towards the shiny side. After it snaps, pull gently, and a transparent layer of skin, similar to Scotch tape, will appear.
Elodea leaf: Elodea leaves are two cell layers thick. The cells in one layer are smaller than the cells in the other, so elodea leaves can be used to better understand a microscope's depth of field.
Cheek cells: Human epithelial cells can be obtained by gently rubbing a toothpick on the inside of the mouth, and then swirling the toothpick in the physiological saline on the slide.
Pond water: Obtaining some water from a pond makes wet mount preparation a breeze, since the water and the specimens are both included.
Hope this helps
True. Alluvial fans, deltas, and deposition are examples of land formations that are formed from deposits by rivers.
Can you please mention which following. So that I can help you.... ☺️
