1. Maintaining metabolism
Introduction

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

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

5. 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

6. 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

7. 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

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

10. …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

12. …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

14. 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

15. 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

16. 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

20. T p 164
Try Q 1 - 4

21. 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

24. 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

25. 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

26. Sensory receptors
effectors activated

27. 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

29. 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

32. …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

34. 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