DNA or protein from a virus entered bacterical cells during infection
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The breathing process occurs as follows: Inhalation increases the volume of the lungs, which reduces internal pressure and causes air to enter. Then the exhalation makes the opposite process. Gaseous exchanges occur in the lung alveoli and are responsible for eliminating the gases we do not need and preparing the oxygen to be spread throughout the body.
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<u>Answer</u>: Natural selection.
<u>Explanation</u>:
- The concept of <em>natural selection</em> was given by <em>Charles Darwin.</em>
- According to this concept, in a given environment the organisms that possess <em>better adaptations</em> have<em> higher chances of survival</em> and, leave behind a <em>greater number of progenies</em>.
- When malaria outbreak occurs, the allele frequencies change and only the organisms that possess the alleles which help them to <em>survive</em> this outbreak due to resistance against malarial infection will be selected by nature and<em> hence, this is an example of natural selection.</em>
Answer:
b. a semi-permeable double layer of phospholipids that have hydrophilic heads and hydrophobic tails
Explanation:
B is correct as the cell membrane is selectively semi-permeable. It is selectively semi-permeable because this quality allows it to control what can and can't enter the cell, and how it does so.
The cell membrane also has a phospholipid bi-layer comprised of a double layer of phospholipids which have hydrophilic head and hydrophobic tails. This is because the heads are made of phosphate and are polar and are therefore attracted to water (hydrophilic), while the tails are made of lipids (i.e. fats, oils) which do not mix with water and are therefore hydrophobic.
The properties of each phospholipid is also why they form the double layer structure, the hydrophilic heads naturally face outwards into the water and protect the hydrophobic tails on the inside.
Hope this helped!
