Speciation is not a mechanism of microevolution.
Answer:
The correct answer is- Immune system
Explanation:
There are physical, chemical and immunological barriers present in our body which helps us to protect from the foreign antigen. They all assist each other and helps in pathogen removal from our body.
The physical barrier includes skin, gastrointestinal tract, respiratory tract, etc which do not allow the microbe to enter the body. Chemical barriers include tear, saliva, acid in the stomach which kills microbes on the body surface.
Immune cells like macrophages, B cells kills microbes when it gets in the body. Lymphatic system also contain immune cells and helps in microbe removal.
So the immune system is assisted by physical barrier, chemical barrier, and lymphatic system.
Unoxygenated blood from veins enters the right atrium then it goes down to the right ventricle then out through the pulmonary artery to the lungs where it becomes oxygenated blood which then enters the heart through the pulmonary veins and it goes to the left atrium and then is pumped down to the left ventricle and out through the aorta to the arteries where it travels to different organs and becomes deoxygenated and then the cycle repeats itself.
The answer 4 the above question sounds like a vitamin D deficiency.
The correct order of steps in a gram staining procedure is:
(4) the specimen is treated with a stain called crystal violet.
(1) iodine is added as a fixative or mordant.
(3) the specimen is flushed with alcohol to dehydrate peptidoglycans and trap the stain.
(2) the specimen is treated with a stain such as safranin or fuchsin (a pink stain)
Gram staining is a common staining technique which helps to classify the bacteria into two categories: Gram positive and Gram negative. Gram positive bacteria appear violet in color and Gram negative bacteria appear to be pink. This color difference appears due to the difference in the bacterial cell walls.
To know more about Gram staining, here
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