Maintaining metabolism Introduction

Metabolic Rate Metabolic rate can be calculated by measuring rates of oxygen consumption or CO2 or heat production Measurements are made using respirometers

Explain how this respirometer could be used to give a measure of the oxygen consumption rate of the seeds.

Oxygen delivery High metabolic rates require efficient delivery of oxygen to cells In vertebrates, oxygen is delivered in blood pumped by the heart Vertebrate hearts have evolved to increase efficiency of the delivery of oxygen to tissues This has been achieved by the evolution of double circulation and the separation of pulmonary (oxygenated) and systemic (deoxygenated) bloods

Single/double Separate single no double incompletely in some Vertebrate class Single/double Separate fish single no amphibian double reptile incompletely in some bird or mammal completely

Comparative circulation Fish – single so loss of pressure a problem Amphibian and reptile – double so pressure maintained but tissue blood incompletely oxygenated Bird and mammal – double so pressure maintained and tissue blood completely oxygenated

Lungs Amphibian lungs are small, thin-walled sac without alveoli Amphibians use skin and mouth for gas exchange unless highly active

…continued Reptiles and mammals have lungs with a complex system of branching tubes ending in many alveoli and giving a huge surface area The surface area is moist and richly supplied with blood

…continued Birds are the most active vertebrates They have a system of extra air sacs to keep air flowing through the lungs in one direction

Adaptations for low oxygen niches Humans respond to high altitude by increasing the number of red blood cells by up to 20% when moving from sea level to 4000 metres It takes several weeks for this adaptation to take effect Diving mammals such as seals and whales are able to slow their heart rate during dives so conserving oxygen usually used by heart muscle Changes occur which make the animal less buoyant and so energy is conserved since it becomes easer to remain at depth

Oxygen through geological time For 2 billion years after its formation, the Earth’s atmosphere had no oxygen After this time the evolution of photosynthesis produced an atmosphere with about 1% oxygen About 600 million years ago the level rose to its present day level of 20% allowing the evolution of large air breathing organisms including megafauna

Oxygen consumption and fitness VO2 max is the maximum oxygen that an individuals body can take up and use This measure is regarded as a way of indicating physical fitness in humans It is measured using a procedure involving exercising on an ergometer – a treadmill or exercise bike

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Conformers and Regulators Abiotic factors such as temperature can vary in an organism’s environment Regulators adjust their metabolic rate using physiological mechanisms to maintain a steady state Conformers cannot alter their metabolic rate using physiological means

Conformers The state of a conformer’s internal environment varies with the external environment Conformers live in stable environments such as the ocean depths The advantage of conforming is low metabolic energy costs The disadvantage of conforming is being limited to narrow ranges of environments and lack of ability to tolerate change should it occur Some conformers use behavioural responses to increase the range of conditions which they tolerate

Regulators Regulators have physiological homeostasis which maintains the internal steady state This uses the principle of negative feedback to maintain the internal environment and has metabolic costs in energy

Sensory receptors effectors activated

Example - Thermoregulation Changes in body temperature detected by the hypothalamus in the brain Nervous impulses sent to effectors [sweat glands, thyroid gland and muscles of blood vessel walls and skin] Effectors make corrective responses which tend to return the temperature to the normal set point Negative feedback switches off the corrective responses

Summary of skin responses Too hot Sweating increases and evaporation of sweat increases heat loss by convection Vasodilation increases blood flow to skin and increases heat loss by radiation

…continued Too cold Thyroid gland releases a hormone which increases metabolic rate Hair erector muscles pull hair up trapping a layer of air and increasing insulation Vasoconstriction reduces blood flow to skin reducing heat loss by radiation

Maintaining metabolism during environmental change Project – max 500 words with illustrations For each section… describe the content using an example and relating it to survival through the maintenance of metabolism Dormancy Hibernation Aestivation Daily Torpor Migration Research methods using tracking Innate and learned influences on migratory behaviour Extremophiles eg. thermophilic bacteria