O-LevelBiologyTransport in Humans5090/21 · May/June 2023 · Q612 Marks

The human heart pumps blood which circulates around the body in blood vessels.

(a)(i)Name the chamber of the heart with the thickest wall.[1]
(a)(ii)State what causes the sound of the heartbeat.[1]
(a)(iii)Name the blood vessel that carries blood from the aorta to the liver.[1]
(a)(iv)State one function of blood plasma.[1]
(b)Explain the difference between antibodies and antibiotics.[3]
(c)Describe how the process of natural selection has led to the development of strains of antibiotic-resistant bacteria.[5]

Mark scheme

Marking points from the official mark scheme (May/June 2023). The mark or mark type is shown in brackets.

[1] left ventricle ;
[1] closing of valves ; A opening and closing of valves
[1] hepatic artery ;
[1] named substance transported ; A blood clotting
[1] antibodies produced by white blood cells / internally / by the body ;
[1] antibiotics are drugs / medicines (that are administered) ; A produced externally/in a lab/in a fermenter
[1] antibodies produced in response to an antigen / bind with an antigen ;
[1] antibodies are more specific than antibiotics ;
[1] antibodies affect viruses, antibiotics do not ; A antibodies are proteins, antibiotics are not
[1] variation within a population ;
[1] mutation produces resistant bacteria ;
[1] antibiotic kills many bacteria / some survive antibiotic ;
[1] survivors reproduce ;
[1] pass on alleles to next generation ;
[1] repeated over many generations ;
[1] higher proportion of bacteria in population can resist antibiotics ;
[1] misuse / over-prescription increases chances ;
[1] AVP ; e.g. short-generation time of bacteria

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