surface area the faster the rate of diffusion • Difference in concentration – the greater the concentration gradient the greater the rate of diffusion • Diffusion distance – the less the diffusion path the greater the rate of diffusion • Permeability • Moistness – oxygen and carbon dioxide diffuse in solutions • Transport systems – effective transport system is needed to maintain a diffusion gradient (may include a vascular system)
or air • Oxygen content of a given volume of water is lower than that of air • Aquatic organisms must pass a greater volume of the medium (water) over its respiratory surface in order to obtain enough oxygen
ratio the better diffusion can support life alone • Unicellular organisms have a larger surface area to volume ratio • Multicellular organisms have a smaller surface area to volume ratio • Nutrients and oxygen would reach the inner cells but it would be too slow to sustain life processes • These organisms posses adaptations for gas exchange: gills in aquatic environments or lungs in terrestrial environments • Large moist areas for gaseous exchange is a site for potential water loss
aquatic organism • It is heterotrophic, ingests chemical energy by phagocytosis • Oxygen and nutrients can diffuse in and carbon dioxide can diffuse out directly • Distances within the body are small • Low metabolic rate
restricted to damp areas (e.g. underground) • Maintain a moist body surface (place of gaseous exchange) for diffusion • Gases dissolve in the moist environment and diffuse across the skin • Have a closed circulatory system (‘blood’ or respiratory pigment is transported around the body in vessels) • Blood is pumped around the body by 5 pseudo hearts (little bags of muscle)
from water by passing it over internal gills • Bony fish have 4 sets of internal gills supported by a bony arch • Operculum are on the outside of the fish and look like flaps • Gill filaments (each gill has 2 rows) are underneath the operculum • Gill filaments extend the surface area for gaseous exchange • Water is a dense medium with a low oxygen content • Water is forced over the gills by the changing of internal pressure
buccal cavity • Internal pressure becomes lower than that of the water outside of the fish • Water moves into the mouth (from high pressure to a lower one) • Operculum muscles contract and causes them to bulge outwards, this lowers the pressure in the operculum cavity • Water flows over the gill filaments and into the operculum cavity • Fish closes mouth and rises the floor of the buccal cavity • Internal pressure becomes higher than that of the water outside of the fish • Operculum opens and water flows out (from high pressure to a lower one) • The result of opening and closing the mouth is a continuous flow of water over the gills
(in the dense network of capillaries that run by the gills) flows in the opposite direction of the water being forced over the gills • Blood always meets water with a higher oxygen concentration • Gaseous exchange can occur over the whole gill filament • Maintains a concentration gradient, equilibrium is never reached
fish but mature into air breathing frogs • Use their moist skin as a respiratory surface for gaseous exchange when inactive or near water • Use lungs as a respiratory surface for gaseous exchange when active or further from water
oxygen • Air reaches the tissues by a branching system called tracheae • Tracheae open to the exterior of the insect by valves called spiracles • Smaller tracheae branch from and end as fine tracheoles • These end between the cells of the tissues • Contractions of the flight muscles causes compression and expansion of the thorax • This moves air in and out of the tracheoles • Movement is like the compression and expansion of bellows
organisms like fish • Use a less dense medium to obtain oxygen – air • Have to move around without the support of water • Control their own body temperature which is usually higher than their surroundings and takes up a lot of energy • Have internal lungs • Minimises water and heat loss
circulatory system • Heart pumps deoxygenated blood to the gills to get oxygenated by taking oxygen from water • Blood travels around the body giving oxygen to cells before returning to the heart
circulatory systems • Pulmonary circulation – Deoxygenated blood from heart to lungs, oxygenated blood from lungs to heart • Systemic circulation – Oxygenated blood to body’s cells, deoxygenated blood to the heart • Tissues receive as much oxygen as possible because oxygenated and deoxygenated blood does not mix • Fully oxygenated blood can be quickly delivered to tissues at high pressures • Blood travels at low pressures to the alveoli to prevent damage to vessels but gaseous exchange can still take place
diffuses from cell to cell, there are no blood vessels and blood can fill body cavities • Closed circulatory systems – blood is transported through blood vessels and does not fill body cavities
Open or closed Single or double Amoeba Water Cell membrane No circulation Annelida (earthworm) Air Moist skin Closed, double Fish Water Gill plates, operculum Closed, single Amphibian Air Moist skin, lungs Closed, double Insect Air Respiring tissue (muscle) Open, single Mammal Air Lungs, alveoli Closed, double
part of the body called the thorax • The diaphragm separates the thorax from the abdomen (digestive organs) • The job of the breathing system is to move air in and out of the lungs • Inhalation – intake of air into the lungs • Exhalation – air moves out of the lungs
up and out • Diaphragm muscles contract and it flattens • Increases volume in the thorax • Reduces pressure in the lungs • Air is forced into the lungs because pressure outside is greater than the pressure inside
and in • Diaphragm muscles relax and it curves upwards • Decreases volume in the thorax • Increases pressure in the lungs • Air moves out of the lungs as pressure outside is less than pressure inside
Capillaries keep blood supply and maintain a concentration gradient Endothelium tissue Thin epithelium wall Moist lining containing surfactants so gasses can diffuse Also keeps a larger surface area by stopping alveoli from sticking together
are thin so they shorten the diffusion pathway • Large surface area – leaves have a large surface area • Maintains concentration gradient – leaves are permeated by air spaces, spongy mesophyll tissue allows diffusion of gases into and out of stomata • Most covering – Spongy mesophyll tissues are coated in a layer of moisture • Timing – Plants only photosynthesis in daylight but they respire 24/7
long axes are perpendicular to the surface, less cell wall is blocking sunlight to each cell • Spongy mesophyll – intracellular air spaces inside the tissue allow oxygen and carbon dioxide to diffuse across the leaf • Spongy mesophyll – cells inside are moist so gases can dissolve before diffusing • Waxy cuticle – prevents water loss • Pores/stomata – allows water and gases through • Guard cells – change shape to open and close the stomata to help control gas exchange and water loss
= glucose + O2 • More oxygen produced • Oxygen diffuses out of the leaf • Carbon dioxide diffuses into leaf More respiration than photosynthesis • O2 + glucose = energy + CO2 + H2O • More carbon dioxide produced • Oxygen diffuses into leaf • Carbon dioxide diffuses out of leaf
guard cells • Usually found on the lower surface of the leaf • Guard cells change shape to open or close the stomata • Have thick inside cell walls and thinner outside cell walls • If water enters the guard cell, they become turgid and swell to open the pores/stomata • If water leaves the guard cell, they become flaccid and close the pore
guard cells photosynthesise and produce ATP • An active transport mechanism (supported by the ATP) takes up potassium ions from epidermal cells into the cytoplasm of guard cells • Stored starch (insoluble) is converted into malate (soluble) • Malate (hypertonic to outside the cell) lowers the water potential in the guard cells and water enters by osmosis • Inner walls of the guard cells are inelastic so when the cells become turgid they curve away from one another and opens the pores • The reverse happens at night and the pores close (less malate so is hypotonic to outside the cell)
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