Learning Outcomes:
Changes in an organism’s metabolic activity, in addition to structural features and changes in physiological processes and behaviour, enable the organism to maintain its internal environment within tolerance limits (temperature, nitrogenous waste, water, salts, and gases) (SU)
This page focuses on the underlined parts above. Specifically...
To learn about the second part of the syllabus point, read through overview in Chapter 10.3. Then we will go to these in more detail later inthe course via following weebly pages:
This page focuses on the underlined parts above. Specifically...
- the definition of tolerance limits , optimum range and physiological stress
- Metabolic actvitiy and the effect of temperature and pH on metabolism
To learn about the second part of the syllabus point, read through overview in Chapter 10.3. Then we will go to these in more detail later inthe course via following weebly pages:
- Temperature and Homeostasis (10.4)
- Water, Salts, Gases and Homeostasis (Chapter 11)
- Nitrogenous Waste and Homeostasis (11.2 specifically)
Tolerance Limits (Chpt. 10.3)
- Tolerance refers to how well an organism functions under different environmental conditions.
- Remember: organisms are adapted to their typical/natural environment.
- The degree to which a species can cope with its environmental conditions is a measure of how well it is adapted to its environment.
- An organism's ability to function, grow and reproduce is dependant to on:
- The presence of critical environmental resources or conditions
- At critical times of their year or life cycle
- While organism may be able to survive in a range of conditions, they also have tolerance limits.
- We see evidence of species tolerance limits everywhere!
Everyday examples of tolerance limits:
- We don't grow raspberries in Geraldton...
- They need summer maximums of 24 degrees celcius or lower
- They need winter minimums of -7 degrees celcius or lower (preferably with a frost)
- POLAR BEARS would never be kept at Perth Zoo...
- Polar bears are very good at generating and trapping their own body heat.
- Polar bears are very bad at losing exess body heat.
- If kept at temperatures above 20 degrees celcius they are likely to overheat.
The law of tolerance was proposed by an American zoologist, Victor Shelford in 1911
Tolerance Range: Each organism has a set range of temperatures, pressure and nutrients which they can tolerate.
Optimum Range: Homeostasis maintains the internal levels of heat, water and substances within an optimum range to ensure survival.
Physiological Stress occurs when an organism's internal environment moves beyond the optimum range. This typically happens which the species is outside its envionmental tolerance range.
- According to the law of tolerance, populations have optimal survival conditions within critical minimal and maximal thresholds
- As a population is exposed to the extremes of a particular limiting factor, the rates of survival begin to drop
Tolerance Range: Each organism has a set range of temperatures, pressure and nutrients which they can tolerate.
Optimum Range: Homeostasis maintains the internal levels of heat, water and substances within an optimum range to ensure survival.
Physiological Stress occurs when an organism's internal environment moves beyond the optimum range. This typically happens which the species is outside its envionmental tolerance range.
The cause of tolerance limits...
Let us take a step back to Unit 2 (Year 11) and put all the puzzle pieces together...
Metabolic Activity:
Do you remember....?
If the internal environment gets too hot/cold/acidic/alkaline - enzyme function is hindered and the body cannot complete essential chemical reactions for maintenance of life.
If the body does not maintain an optimum pH range, it cannot ensure a constant supply of nutrients to cells, thus it cannot maintain a constant internal temperature.
Did you know?
Physiological processes help maintain homeostasis:
If you have been exercising for a while...
The body has Physiological Mechanisms which come to the rescue...
Structural & behavioural features help maintain homeostasis:
Continuing with the exercising example...
Behavioural features:
Structural features:
Metabolic Activity:
Do you remember....?
- Metabolism is the sum of all chemical reactions that occur within an organisms to maintain life
- Most of these reactions require the help of enzymes as catalysts
- Enzymes have an optimal pH and temperature range outside of which they will not function properly.
If the internal environment gets too hot/cold/acidic/alkaline - enzyme function is hindered and the body cannot complete essential chemical reactions for maintenance of life.
If the body does not maintain an optimum pH range, it cannot ensure a constant supply of nutrients to cells, thus it cannot maintain a constant internal temperature.
Did you know?
- Carbon dioxide (a waste product from cellular respiration) can alter an organism's internal pH
- An increase in CO2 concentration causes a decrease in pH (lower pH = more acidic)
- A low pH reduces enzyme function > slowing metabolic rate > reducing heat generated > further slowing metabolic rate
- Just one example of why substances need to be kept at ideal concentrations in order for a body to function.
Physiological processes help maintain homeostasis:
If you have been exercising for a while...
- Your muscle cells have required more glucose and oxygen for respiration.
- Your muscle cells have also generated more CO2 as a waste product.
- The increase in respiration reactions also generates more heat
The body has Physiological Mechanisms which come to the rescue...
- Breathing rate increases to allow more blood to past through the lungs, thus more opportunity for CO2 to be released.
- Breathing rate increase also allows more oxygen to be diffused into blod to supply muscle cells.
- Increased temperature is detected by the hypothalamus which sgnals sweat glands to operate, increasing rate of heat loss.
Structural & behavioural features help maintain homeostasis:
Continuing with the exercising example...
Behavioural features:
- You will want to remove any excess clothing - this also enables the sweat to be more effective
- You will slow down you movements
- You may move to a cooler spot (shade)
Structural features:
- Your body has a huge network of capillaries over the alveoli to allow for more rapid gain of O2 and release of CO2
- Your body has more sweat glands in the locations that tend to overheat the most (e.g armpits)
Now you should:
- Read pages 341 - 348
- 2022 Creelman Chapter 4, Question 25 and 41
- Complete Question set 10.3