<span>After ovulation, an oocyte, or egg cell, remains viable in the female body for up to 24 hours. The generally accepted lifespan in a woman's body is 12 to 24 hours for the egg and up to five days for the sperm cells. Intercourse occurring as many as five days prior to ovulation, therefore, could potentially result in pregnancy.</span>
The fossil record shows a sequence from simple bacteria to more complicated organisms through time, it is very reliable because it is physical evidence and by studying fossils, scientists can learn how much (or how little) organisms have changed as life developed on Earth.
Unsaturated fatty acids are a component of the phospholipids in cell membranes and help maintain membrane fluidity. The Phospholipids contain a variety of unsaturated fatty acids, when compressed, the “kinks” in their tails push adjacent phospholipid molecules away, that helps in maintain fluidity in the membrane. Unsaturated fatty acids have at least one double bond, creating a "kink" in the chain, the absence of double bonds decreases fluidity, making the membrane very strong and stacked tightly.
The ratio of saturated and unsaturated fatty acids determines the fluidity in the membrane at a temperature, at appropriate temperatures the phospholipids have enough kinetic energy to overcome the intermolecular forces holding the membrane together, which increases membrane fluidity.
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Answer:
<u>Light microscope</u>:
- use a beam of light to produce magnified images
- can be used to examine living cells and tissues
<u>Scanning electron microscope</u>:
- use a beam of electrons to produce magnified images
- can be used to examine DNA
- can be used to examine cells
<u>Transmission electron microscope</u>:
- use a beam of electrons to produce magnified images
- can be used to examine DNA
- can be used to examine cells
Explanation:
Light microscope: is a commonly used microscope also known as compound microscope. Magnifies images from 40X upto 1000X. It uses ray of visible light to produce a magnified image. The light microscope can be used to view specimen of both living and dead cells or tissues. However, it doesn't give a detailed view of a specimen like electron microscope.
Scanning electron microscope: It uses electron beam as an illuminating source. It has a much higher resolving power than light microscope because it uses electrons instead of light. It magnifies object upto 500000 times the actual size. Internal structures can also be viewed. However, only dead specimen can be used because the beam of electrons can kill the cells. They are of two types:
- <u>Scanning electron microscope(SEM): </u>an electron beam passes over the specimen's surface and displaces electrons which are then focused on a screen to form an image. Images appear in 3-D
- <u>Transmission electron microscope: </u>electromagnets magnify the image by passing beam of electrons through a thin specimen. Images appear in 2-D
