All MCQs

Earthworms have a closed circulatory system with major vessels that direct blood flow. This supports exchange and transport through the segmented body.

Small or flat animals may exchange materials effectively by diffusion because cells are close to the external environment. Large animals require transport systems.

Platelets are essential for normal clot formation. Low platelet count can lead to prolonged bleeding or easy bruising.

Vasodilation increases vessel diameter, reducing resistance and often increasing blood flow to a tissue.

Hemoglobin binding is crucial for oxygen transport. Impaired binding reduces oxygen delivery, causing tissue hypoxia.

Hemoglobin binds oxygen reversibly in red blood cells, allowing blood to carry far more oxygen than plasma alone.

Invertebrate clotting responses help seal wounds and trap pathogens. This is part of innate defense and fluid balance.

Arteriole constriction reduces local perfusion. Less warm blood reaches the tissue, making it cooler and paler.

Dehydration lowers plasma volume, which can reduce venous return and blood pressure. Circulatory regulation attempts to compensate.

Hemocyanin is a copper-containing respiratory pigment found in many arthropods and molluscs. Oxygenated hemocyanin is often bluish.

Lymph nodes filter lymph and contain immune cells. Swelling often reflects immune activation during infection.

Large capillary surface area and short diffusion distance maximize exchange of gases, nutrients, and wastes between blood and cells.