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Exchange between organisms and the environment (Insects/ Single celled…
Exchange between organisms and the environment
Fish
Gills
Gill filaments
Stacks of layers which contain gill lamellae increasing the surface area
Gill lamellae
Sites of gas exchange increase surface area
Counter current flow
Flow of blood opposite to flow of water/ oxygen
Maintains a constant concentration gradient
Diffusion constantly occurring
Insects/ Single celled organisms
Single celled organisms exchange by simple diffusion
Insects have exchange system which increases surface area and conflicts with water loss
Single celled organisms have no complex exchange structures
Insects have internal network of trachea/ these then split into tracheoles
Short diffusion pathway between trachea and body cell
Gases pass along a diffusion gradient high concentration to low concentration
Muscle contractions can squeeze the trachea enabling mass movements of gases to increase speed of exchange
the ends of tracheoles contain water, this allows the easier diffusion and exchange into respiring cells
Plants
Stomata
Tiny pores mainly situated in the bottom of the leaf
Each stomata is surrounded by guard cells which contain chloroplasts which are photosensitive
Able to balance the conflicting needs of gas exchange and control of water loss
Diffusion takes place in air which makes it more rapid
Large surface area of mesophyll cells for rapid diffusion
Short diffusion pathway
Structure of leaves
Waxy cuticle and upper epidermis
Palisade mesophyll and spongy mesophyll (sites of photosynthesis)
Lower epidermis and stomatal pores
Humans
Structure
Bronchi: divisions of trachea leading into each lung similar to trachea structure and produce mucus.
Bronchioles: series of sub divisions leading into alveoli made up of muscle and epithelial cells to control air flow in and out of the alveoli
Trachea: wind pipe which is flexible and supported by cartilage. Also contain ciliated epithelial and goblet cells
Nasal cavity
Alveoli: minute air sacs which are sites of gas exchange, they are lobed and contain collagen and elastic fibres to allow the alveoli to stretch and expand
Exchange
Exchange occurs via diffusion and partial pressures
High concentration of Oxygen in alveoli in lungs
High concentration of Carbon dioxide in blood stream
Large surface area and short diffusion distance allow for fast exchange
Mechanism
Inspiration
Active process
External intercostals contract
Ribs pulled out and up increasing thorax volume
Diaphragm contracts increasing thorax volume causing a decrease in lung pressure
Expiration
Mostly passive process
Internal intercostals contract
volume of thorax decreases as ribs move down and in
diaphragm relaxes causing decreased thorax volume and lung pressure increases