The cell membrane protects the cell and keeps bad things like viruses from getting in the cell.<span>It consists of the lipid bilayer with embedded proteins.</span>
Answer:
Until recent history,extinctions have always happened gradually and on a small scale.
Explanation:
Extinction occur when environmental factors like natural disaster,habitat fragmentation,over exploitation,global change don't favor the survival of species thus gradually leads to extinction of species.
Some times human activity becomes the major problem for extinction.More over,poor reproduction,decline in population number and genetic inbreeding also leads to extinction.
99% of all species that exist on earth become disappeared.
Evolution leas to speciation which leas to formation of new species but species become extinct when they are unable to survive against competition.
Answer:
A. Carbohydrates are used to store energy and provide structure/support in living things.
Explanation:
The four primary functions of carbohydrates in the body are to provide energy, store energy, build macromolecules, and spare protein and fat for other uses.
Answer: Acid rain
The volcanic eruption is a natural phenomena that results in the liberation of the lava from the heap of the earth along with the gases. The volcanic eruption causes major damages to the vegetation lying above the erupted crater of the volcano. This results in the immense release of gases such as carbon dioxide, carbon monoxide, sulfur dioxide, hydrogen chloride, hydrogen fluoride, methane and ammonia all these gases are major pollutants of the air. These gases reacts with water vapor in the atmosphere and condense in the form of acid rain.
Answer:
The correct option is b. lower esophageal sphincter
Explanation:
The esophagus is the initial part of the digestive tract and its function is the transport of the alimentary bolus from the pharynx to the stomach, through the thorax and avoid the reflux thereof. It begins and ends in two sphincter structures, the upper esophageal sphincter and the lower esophageal sphincter, which separate it from the pharynx and stomach. The lower esophageal sphincter has two functions: relax during swallowing and prevent reflux of the gastric contents into the esophagus in the postdeglutory period. After swallowing, there is a relaxation of the lower esophageal sphincter, pressure dropping to levels similar to those of the gastric fundus, which allows the bolus to enter the stomach. This relaxation lasts a few seconds and is followed by a strong contraction that prevents backflow of food.
