5 - Comparative CardioRespiratory Systems Flashcards
What is the primary function of the cardiorespiratory system
To enable gas exchange and transport via ventilation, circulation, and diffusion
How do some organisms survive without a cardiorespiratory system
They rely on diffusion across the body surface, so they must be small or have low metabolic rates
What does Fick’s Law state about gas diffusion
It depends on surface area, partial pressure gradient, and membrane thickness
What types of respiratory structures exist across species
Skin (amphibians)
Gills (fish)
Lungs (mammals, birds)
Tracheae (insects)
Why must organisms without specialised respiratory structures be small or have low metabolic rates
Because diffusion alone is not efficient for meeting high oxygen demands
Which invertebrates have no circulatory system
Sponges and hydra — they use simple diffusion
What is an open circulatory system
Hemolymph flows freely around organs (e.g., insects, crustaceans)
What is a closed circulatory system
Blood stays in vessels, allowing better pressure and flow control (e.g., earthworms, vertebrates)
Describe the circulatory system of fish
Two-chambered heart, single circulation loop
How is circulation different in amphibians and reptiles
Three-chambered heart, with some mixing of oxygenated and deoxygenated blood
How do birds and mammals differ
They have a four-chambered heart with full separation of oxygenated and deoxygenated blood
Why is breathing in water more energetically costly than in air
Water contains less oxygen and is more viscous
What is counter-current exchange in fish gills?
Blood flows opposite to water, maximising oxygen uptake
How do terrestrial animals achieve efficient gas exchange
Through lungs with large surface areas
What molecules carry oxygen in blood and muscles
Haemoglobin (in blood) and myoglobin (in muscles)
What is the Bohr Effect
Higher CO₂ and acidity lower Hb’s O₂ affinity, helping O₂ release to tissues
Haldane Effect
Deoxygenated haemoglobin binds CO₂ more easily, aiding CO₂ transport
What is the mammalian dive response
A set of adaptations (apnea, bradycardia, vasoconstriction) to conserve oxygen during dives
How do diving mammals store oxygen in muscles
They use myoglobin, which has a high oxygen affinity
How does the body adjust to increased oxygen demand (e.g., during exercise)
By increasing ventilation rate/volume and cardiac output, and redirecting blood flow
What happens during hypoxia or hibernation
The body prioritises oxygen supply to vital organs and slows metabolism
How has the circulatory system evolved across species
From diffusion-based to complex closed systems with high pressure and efficiency
What are advantages of a closed circulatory system
Faster oxygen transport, better control of blood flow, and improved thermoregulation
