Answer :Four characteristics were to be used for the classification of all viruses:
Nature of the nucleic acid in the virion.
Symmetry of the protein shell.
Presence or absence of a lipid membrane.
Dimensions of the virion and capsid.
Explanation:
Answer:
Mechanical barriers — which include the skin , mucous membranes , and fluids such as tears and urine — physically block pathogens from entering the body. Chemical barriers — such as enzymes in sweat , saliva , and semen — kill pathogens on body surfaces.
Functional and economically most important mineral in nutrition of layers
is calcium, primary because of egg production, i.e. forming of the egg shell.
The correct option is C.
The heart is part of the cardiovascular system. The heart pump the blood round the body several times in a day. The blood is made up of several types of cells which carry out specific function in the body, these include the white blood cells which serves as soldiers of the body. The lymph refers to the fluid that circulate throughout the lymphatic system. Both the blood and the lymph are carried round the body by the cardiovascular system during the process of circulation.<span />
A biotic factor is all of the students in the classroom.
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