Key Area 3: Metabolic Rate Unit 2: Metabolism and Survival

Metabolic Rate The metabolic rate of an organism is the quantity of energy consumed per unit of time. This can be studied using equipment called respirometers and calorimeters. Metabolic rate can be measured as: Oxygen consumption/per unit of time Carbon dioxide production/per unit of time Energy production as heat/per unit of time CfE Higher Biology Metabolism and Survival

Metabolic Rate CfE Higher Biology Metabolism and Survival Simple respirometers - measure the amount of oxygen consumed

Metabolic Rate CfE Higher Biology Metabolism and Survival

Metabolic Rate Calorimeters measure metabolic rate as: Energy production as heat/per unit time. CfE Higher Biology Metabolism and Survival

Basal Metabolic Rate (BMR) CfE Higher Biology Metabolism and Survival What is meant by basal metabolic rate? This is the minimum rate of energy release needed by an organism to maintain essential body processes. It occurs at rest and periods of inactivity. What are essential body processes? Maintenance of vital organs such as heart, lungs and brain.

Comparing metabolic rates CfE Higher Biology Metabolism and Survival Why are the metabolic rates for these organisms different? Write several sentences explaining why.

Metabolic Rate CfE Higher Biology Metabolism and Survival The greater the mass of an organism the higher the organism’s metabolic rate. BMR is higher per unit of body mass in small animals compared to larger ones. Small animals have a higher metabolic rate because they require a greater delivery of oxygen to the tissues around the body. Small animals have a greater surface area to volume ratio, so more heat is lost.

Oxygen delivery CfE Higher Biology Metabolism and Survival What happens as an organism experiences an increased need for energy? Its’ metabolic rate increases and therefore so does the rate of aerobic respiration and the consumption of oxygen. Multicellular organisms need efficient oxygen delivery systems like a cardiovascular system.

Circulatory systems CfE Higher Biology Metabolism and Survival What can you remember about the circulation of blood around the body? Write down as much as you can.

Circulatory systems CfE Higher Biology Metabolism and Survival Heart – made of 4 chambers - pump – 2 ventricles, 2 atria – Right atria receives deoxygenated blood from body and pumps it to lungs – Left atria receives oxygenated blood from lungs and pumps it to body 3 types of blood vessels – Arteries: carry blood away from heart (under high pressure) – Veins: carry blood back to the heart (under low pressure) – capillaries: smallest vessels which link to the tissues of the body allowing exchange of nutrients, gases and waste products. Major vein delivering deoxygenated blood to heart – vena cava Major artery delivering oxygenated blood to the body - aorta

Closed Circulatory Systems CfE Higher Biology Metabolism and Survival Vertebrates have closed circulatory systems. What does this mean? This means that the blood is contained in a continuous circuit of blood vessels. The blood in this continuous circuit is kept moving by the heart which acts as a pump. The blood is pumped into large vessels (arteries)then into smaller vessels, veins and then capillaries, the smallest vessel. A drop in pressure occurs here due to the resistance the narrowing vessels offer the blood Oxygen moves quickly from the blood in the capillaries into respiring cells. Carbon dioxide moves the other way.

Single circulatory system CfE Higher Biology Metabolism and Survival In fish, blood passes through a 2 chambered heart once for each complete circuit of the body. Blood flows to the gills straight from the heart at high pressure But goes to the capillaries of the body at low pressure. This is an inefficient process and primitive method.

Single circulatory system CfE Higher Biology Metabolism and Survival Why is this an inefficient system? Why does blood pass through the heart only once?

Double circulatory system CfE Higher Biology Metabolism and Survival Why is this system ‘double’? Blood passes through the heart twice for each complete circuit of the body. Blood is pumped at high pressure to both the heart and the lungs. Blood flow is therefore vigorous. This is a more efficient system than the single system.

Incomplete Double circulatory system CfE Higher Biology Metabolism and Survival This system is found in amphibians and reptiles. It is described as incomplete because the heart has one ventricle. This means that there is mixing of oxygenated and deoxygenated blood. The moist skin of amphibians allows oxygen to diffuse in to the blood from the air which deals with this problem. In reptiles there is a partial division of the ventricle by a septum. This means the amount of blood mixing is reduced.

Complete Double circulatory system CfE Higher Biology Metabolism and Survival This system is found in birds and mammals. It is described as complete because the heart has two ventricles which are separated by a septum. This prevents mixing of oxygenated and deoxygenated blood. Lots of oxygenated blood is delivered to respiring tissues and it is also able to pick up heat from these tissues and circulate it. It is the most efficient and advanced circulatory system.

Lung Complexity CfE Higher Biology Metabolism and Survival What can you remember about the structure of the lungs? Write down all you can.

Lung Complexity CfE Higher Biology Metabolism and Survival Amphibians have permeable skin and can exchange gases primarily through their skin and also their mouth cavity. Their lungs are only used during vigorous activity. Because of this, their lungs are small, thin walled sacs which do contain some alveoli. These lungs provide a small relative surface area for gaseous exchange compared to those of more advanced vertebrates.

Lung Complexity CfE Higher Biology Metabolism and Survival Reptiles and Mammals possess a branching system of tubes that end in millions of alveoli. They have a thin moist inner lining with a large surface area (about 100m 2 in humans). This is an efficient gas exchange system which allows large amounts of oxygen to pass to the blood to be used by metabolising cells.

Lung Complexity CfE Higher Biology Metabolism and Survival Birds especially flying birds are the most active of the vertebrates. This means they require more oxygen relative to their body size. Birds have 2 extra groups of air sacs next to the lungs to push air through the lungs.

CfE Higher Biology Metabolism and Survival In inhalation: the posterior air sacs fill with fresh air while the anterior air sacs fill with stale air from the lungs. In exhalation: fresh air passes from the posterior sacs to the lungs and the stale air passes to the outside.

Lung Complexity CfE Higher Biology Metabolism and Survival This means that air is forced in one direction through the lungs twice rather than into alveoli and back out again by the same route as occurs in mammals. The bird’s lung does not have dead end alveoli but has parabronchi which are many tiny channels.

Lung Complexity CfE Higher Biology Metabolism and Survival The following website shows various different animations on ways to breathe. different-ways-to-breathe.html

Physiological Adaptations for low oxygen niches CfE Higher Biology Metabolism and Survival Some animals have adaptations that allow them to survive and exploit environments that have low oxygen levels. There are two main low oxygen niches: 1. High altitudes 2. Deep diving marine habitats

High Altitude Adaptations CfE Higher Biology Metabolism and Survival Humans survive best at sea level where O 2 concentration is 20%. The air is thinner at high altitudes and therefore less O 2 is gained per breath. To counteract this humans secrete a higher concentration of erythropoietin. A hormone which stimulates red blood cell production. Increasing the number of red blood cells increases the oxygen carrying capacity of the blood. This is because the amount of haemoglobin is increased.

Deep Diving Animals CfE Higher Biology Metabolism and Survival Mammals, such as dolphins, seals and whales can make deep water dives over long periods of time, even though they breathe air. In order to do this, these animals can slow their heart rate down from 125bpm to 10bpm. This conserves oxygen as there is less used by cardiac muscle. Their lungs can also partially collapse as the pressure underwater increases with depth. The air is therefore forced into a smaller volume making the animal less buoyant and easier for the animal to dive. The animal can conserve energy and use it for hunting prey.

Evolution of the Atmosphere CfE Higher Biology Metabolism and Survival Describe what has happened to the concentration of oxygen as the geological timescale has increased using the graph.

Evolution of the Atmosphere CfE Higher Biology Metabolism and Survival When the earth originally formed it contained no oxygen. The appearance of oxygen after 2-3 billion years has been attributed to the evolution of cyanobacteria. These organisms are able to photosynthesise and therefore produce oxygen. Oxygen levels then rose again about 600 million years ago. There is no definite reason for this. However, fossil records provide evidence that this did occur. They show a sudden increase in size at this time which means the organisms must have been larger. Larger organisms would only be able to survive if a high concentration of oxygen was present.

Measurement of VO 2 CfE Higher Biology Metabolism and Survival VO 2 is the maximum oxygen uptake that a person’s body can uptake and use during intense exercise. The oxygen consumption stays steady despite the increase in the exercise workload. VO 2 max is regarded as the best indicator of cardiovascular fitness. It is measured by using carbon dioxide and oxygen analysers connected to an individual performing exercise on a treadmill or exercise bike. The greater the VO 2 then the fitter the individual.