LGS A-Level OCR Biology - Unit 3 - Circulatory Systems
Specialist transport systems are essential because larger or more active organisms have high metabolic demands and low surface area to volume ratios, making diffusion alone inefficient. Substances like oxygen, nutrients, and hormones must be transported from where they’re produced or absorbed to where they’re needed, while waste products must be carried away for excretion.
Give 5 reasons why specialist transport systems are needed
metabolic demands of most animals is high
SA:V decreases as animal size increases so diffusion distances increase whilst SA avaliable becomes relatively smaller
molecules are made in one place but needed in another
food will be digested in one organ system but needs to be transported to every cell
waste products of metabolism need to be removed from cells and transported to excretory systems
Key Terms
Give 5 reasons why specialist transport systems are needed
metabolic demands of most animals is high
SA:V decreases as animal size increases so diffusion distances increase whilst SA avaliable becomes...
As an organism gets larger what happens to the diffusion distance?
It gets larger
Why does a greater level of activity in an organism increase demand for glucose and oxygen?
more activity requires more energy
more energy requires more aerobic respiration
which requires more reactants (oxygen and glucose)
Why does a greater volume of an organism mean a greater demand?
greater volume means greater number of cells
each cell requires energy
so demand for energy/glucose/oxygen increases
Define mass flow
the movement of fluids down a pressure or concentration gradient
Define circulatory system
the transport system of an organism
Related Flashcard Decks
Study Tips
- Press F to enter focus mode for distraction-free studying
- Review cards regularly to improve retention
- Try to recall the answer before flipping the card
- Share this deck with friends to study together
| Term | Definition |
|---|---|
Give 5 reasons why specialist transport systems are needed | metabolic demands of most animals is high SA:V decreases as animal size increases so diffusion distances increase whilst SA avaliable becomes relatively smaller molecules are made in one place but needed in another food will be digested in one organ system but needs to be transported to every cell waste products of metabolism need to be removed from cells and transported to excretory systems |
As an organism gets larger what happens to the diffusion distance? | It gets larger |
Why does a greater level of activity in an organism increase demand for glucose and oxygen? | more activity requires more energy more energy requires more aerobic respiration which requires more reactants (oxygen and glucose) |
Why does a greater volume of an organism mean a greater demand? | greater volume means greater number of cells each cell requires energy so demand for energy/glucose/oxygen increases |
Define mass flow | the movement of fluids down a pressure or concentration gradient |
Define circulatory system | the transport system of an organism |
Define open circulatory system | a transport system with a heart but with few vessels to contain the transport medium |
Define closed circulatory system | the transport medium is enclosed in vessels and does not come into contact with the cells of the body |
Define haemolymph | the blood like fluid contained in insects |
Define single circulatory system | a circulatory system where the blood flows through the heart once during a complete circuit of the body |
Define double circulatory system | a circulatory system where the blood flows through the heart twice during a complete circuit of the body |
Define pulmonary circulation | The portion of the circulatory system which carries deoxygenated blood away from the right ventricle of the heart to the lungs and returns oxygenated blood to the left atrium and ventricle |
Define systemic circulation | The part of the cardiovascular system which carries oxygenated blood away from the heart to the body and returns deoxygenated blood back to the heart |
Give examples of organisms with a single closed circulatory system | Fish and annelid worms |
Give examples of organisms with a double closed circulatory system | Birds and most mammals |
Give an example of an organism with an open circulatory system | Insects |
Why are fish able to be highly active despite having a single closed circulatory system? | the countercurrent exchange mechanism means they can take up a lot of O2 from water their body weight is supported by the water they do not maintain their own body temperatures |
Why are single closed circulatory systems not very efficient? | Blood pressure drops considerably so blood flows slowly back to the heart |
Why are double closed circulatory systems very efficient? | each circuit passes through only one capillary network this maintains relatively high blood pressure so fast flow of blood back to the heart is maintained |
What are the general features of circulatory systems? | fluid to transport dissolved gases, nutrients, and waste a pumping mechanism to move fluid sometimes vessels to carry the fluid |
How are open and closed circulatory systems different? | blood enclosed in vessels in closed but not in open in open circulatory systems the fluid fills body cavities open less efficient |
What is an advantage of having an open circulatory system? | less vulnerable to pressure |
What is an advantage of closed circulatory systems? | more efficient |
What is a disadvantage of open circulatory systems? | requires low metabolic rate so does not work for larger animals |
What is a disadvantage of closed circulatory systems? | requires more energy |
What are the differences between single and double circulatory systems? | go through the heart once in one complete circuit in single and twice in double single has two sets of capillaries while double has one double maintains higher pressure than single |
What is the disadvantage of single circulatory systems? | They are less efficient |