Please help STAT with these questions. Will rate, thank you so much! Question 27
ID: 301691 • Letter: P
Question
Please help STAT with these questions. Will rate, thank you so much!Question 27 1.67 pts Which of the following organisms has a closed circulatory system? O Sponges O Cnidarians Nematodes O Insects O Vertebrates 1.67 pts Question 28 Which of the following features DOES NOT improve the rate of diffusion? O Thin membranes lining respiratory organs such as gills and lungs O Multiple infoldings of respiratory surfaces, such as lamellae in gills O Inhaled fresh air is mixed with old air from the previous breathing cycle O Blood circulates in counter current direction to water flow in gills
Explanation / Answer
1) Option 5 is the correct answer.
Vertebrates have a closed circulatory system. In closed circulatory system, blood is pumped by heart and flows through blood vessels. It does not directly fill body cavities. Of the other given options, Sponges, cnidarians and nematodes do not have a well defined circulatory system, while insects or arthropods have an open circulatory system.
2) Option 3 is the correct answer.
The mixing of inhaled fresh air with the old air from previous cycle does not improve the rate of diffusion. Rate of diffusion of gases in the respiratory system is dependent upon the thickness of the membrane and the surface area of the diffusion surface.
3) Fish: Single-loop circulation, blood passes through heart once before going to tissues.
Fishes have a two chambered heart with one atrium and one ventricle. The atrium collects blood that has returned from the body, while the ventricle pumps the blood to the gills where gas exchange occurs and the blood is re-oxygenated; this is called gill circulation. The blood then continues through the rest of the body before arriving back at the atrium; this is called systemic circulation.
Amphibians: Double-loop circulation, blood goes through the heart twice but mixes with deoxygenated blood returning from the tissues.
Amphibians have two circulatory routes: one for oxygenation of the blood through the lungs and skin, and the other to take oxygen to the rest of the body. The blood is pumped from a three-chambered heart with two atria and a single ventricle.There is some mixing of the blood in the heart’s ventricle, which reduces the efficiency of oxygenation.
Mammals: Double-loop circulation, complete separation of oxygenated and deoxygenated blood.
Mammals have the most efficient heart with four chambers that completely separate the oxygenated and deoxygenated blood; it pumps only oxygenated blood through the body and deoxygenated blood to the lungs.
4) Option 1 is the correct answer.
An antigen is a toxic or foreign agent that is capable of being recognised by the cells of immune system and mounting an immune response by adaptive immune system.
5) Option 1 is the correct answer.
Cytotoxic T-cells are the cells responsible for cell mediated immunity. These are able to induce apoptosis in body cells displaying epitopes of foreign antigen on their surface, such as virus-infected cells, cells with intracellular bacteria, and cancer cells displaying tumor antigens;