Things organisms need to exchange with their surroundings
Oxygen, carbon dioxide, water, ions
As the organism gets bigger
The SA:vol ratio decreases
Thermoregulation
Control of body temperature
Organisms that maintain a constant internal body temperature
Mammals and birds
Metabolic rate
The amount of energy expended by an organism in a given time period
Elephants have a small surface area to volume ratio
Adaptations large animals have to lose heat
Large, flat ears / Sweating or panting / Vasodilation
Being flat or hollow helps multicellular organisms exchange respiratory gases by increasing the surface area to volume ratio, allowing for faster rates of diffusion
How insects reduce water loss
Close their spiracles, waterproof exoskeleton
Difference between tracheae and tracheoles
Tracheae are larger and have rings of cartillage
Insects close the spiracles to reduce water loss
How some insects increase ventilation
Abdominal pumping
Water is more dense than air
Water contains less oxygen than air
Warm water contains less oxygen than cold water
Diffusion of gases is slower in water than in air
Water flow across the gills of fish
Counter-current system
Key components of the gill
Filament and lamellae
Operculum
Gill flap
Gills
Large surface area as filaments at right angles with lamallae
The countercurrent flow in fish gills maintains a concentration gradient along the whole length of the lamellae
The countercurrent flow is important as it allows water to flow in the opposite direction to blood, maintaining the concentration gradient
Leaf adaptations for gas exchange
Large surface area / Spongy mesophyl with air spaces to maintain concentration gradient
The gas needed for leaves to photosynthesise is carbon dioxide
The gas that will diffuse into the palisade mesophyll cells at night is oxygen
Stomata
Openings on the underside of leaves that allow gas exchange
Stomata are sometimes closed to reduce water loss
Xerophyte
A plant adapted for dry environments
Adaptations of xerophytic plants
Sunken stomata / Reduced surface area of leaves / Hairs at stomata / Thick waxy cuticle / Rolled leaves
Path of oxygen from air to blood in mammals
Into mouth/nasal passage, down trachea, into bronchi, into bronchioles, into alveoli, across epithelium and capillary endothelium into blood
Ventilation
Breathing - movement of ribs and muscles/diaphragm to increase air flow to lungs
The rings of cartilage in the trachea prevent collapse
Intercostal muscles
They work in pairs with opposite motions of contraction and relaxation
When the diaphragm contracts, the volume of the thorax increases
The external intercostal muscles contract to pull the ribs up and out
When the volume of the thorax increases, the pressure inside the thorax decreases
Tidal volume
Volume of air in/out of the lungs at rest with each breath