Gas Exchange in Organisms

The surface area to volume ratio plays a significant role in determining the types of adaptations an organism will have. For example, small organisms have a large surface area to volume ratio, which allows for efficient diffusion of substances, while larger organisms have a smaller surface area to volume ratio, leading to adaptations like villi and microvilli for more efficient absorption.

Large organisms have adaptations such as villi and microvilli for efficient absorption of digested food, alveoli and bronchioles for gas exchange in mammals, spiracles and tracheoles for gas exchange in terrestrial insects, gill filaments and lamellae for gas exchange in fish, thin wide leaves for gas exchange in plants, and many capillaries for efficient exchange at tissues.

<p>False</p> Signup and view all the answers

<p>Countercurrent flow in fish gills refers to the water flowing over the gills in the opposite direction to the flow of blood in the capillaries. This ensures that a concentration gradient is maintained across the entire length of the gill lamellae, maximizing oxygen uptake from the water. The oxygen concentration in the blood is never allowed to reach equilibrium with the water, allowing for constant diffusion.</p> Signup and view all the answers

<p>The three key adaptations in plants for efficient gas exchange are a large surface area provided by a large number of fine tracheoles, thin walls of tracheoles for short diffusion distances, and the creation of steep diffusion gradients by the production of carbon dioxide and the use of oxygen, which facilitates efficient movement of gases.</p> Signup and view all the answers

<p>Xerophytic plants have adaptations like sunken stomata to trap moisture, thicker cuticles to reduce evaporation, curled leaves to trap moisture, and longer root networks to reach more water, all aimed at minimizing water loss.</p> Signup and view all the answers

<p>All gas exchange surfaces share three key features: a large surface area, a short diffusion distance, and a mechanism to maintain the concentration gradient.</p> Signup and view all the answers

<p>The circulatory system in mammals is a closed, double circulatory system, meaning the blood remains within blood vessels and travels through the heart twice. This helps maintain the pressure of blood flow, reducing damage to the capillaries in the alveoli and providing time for gas exchange. It ensures efficient transport of oxygenated blood to the body's tissues and deoxygenated blood back to the lungs.</p> Signup and view all the answers

<p>The valves in the heart prevent backflow of blood, ensuring unidirectional flow. They open and close based on pressure gradients, with semilunar valves located in the aorta and pulmonary artery, and atrioventricular valves between the atria and ventricles.</p> Signup and view all the answers

<p>False</p> Signup and view all the answers

<p>The Bohr effect occurs when a high carbon dioxide concentration causes a decrease in the affinity of haemoglobin for oxygen due to the acidic nature of carbon dioxide. This results in a shift of the oxyhaemoglobin dissociation curve to the right, leading to the release of oxygen in respiring tissues.</p> Signup and view all the answers

<p>Llamas, living at high altitudes with lower partial pressures of oxygen, have haemoglobin with a higher affinity for oxygen, allowing them to efficiently load oxygen even in low-oxygen environments compared to humans. Humans have haemoglobin with a typical affinity for oxygen at normal atmospheric pressures.</p> Signup and view all the answers

<p>As water moves into the roots by osmosis, it increases the volume of liquid inside the root, resulting in increased root pressure. This pressure forces water upwards against gravity.</p> Signup and view all the answers

<p>Translocation is the process by which organic substances, primarily sugars, are transported throughout the plant via the phloem. This is achieved by the mass flow hypothesis, which explains the movement of sucrose from its source (production site) in the leaves where it's created during photosynthesis, to sink cells (respiring cells) where it's used.</p> Signup and view all the answers

<p>Companion cells are closely associated with sieve tube elements in phloem and have a crucial role in providing ATP necessary for the active transport of organic substances. Due to the lack of organelles in sieve tube elements, they depend on the companion cells for resources and energy.</p> Signup and view all the answers

<p>Tracing experiments use radioactively labelled carbon to track its movement as it's incorporated into sugars during photosynthesis. The presence of these labelled sugars in specific tissues on an x-ray film indicates the pathway of transport, highlighting the role of the phloem. Ringing experiments involve removing a ring of bark and phloem from a tree trunk, leading to swelling above the removed section. This swelling contains sugars, demonstrating that the phloem is responsible for sugar transport, while the removal of xylem does not impede this process.</p> Signup and view all the answers