Unit 3 - Organisms exchange substances with their environment
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Exchange between organisms and their environment Condensed Notes
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Unit 3 - Organisms exchange substances with their environment
Institution
AQA
The following document contains my structured and easy to read condensed notes filled with great diagrams for all of Biology AQA A level. The boxes for every chapter contain all the concepts you need to know for each chapter with the notes are followed below. Notes are bite sized and will help with...
Unit 3 - Organisms exchange substances with their environment
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Exchange between organisms and their environment
● Exchange
○ Digestive system
○ Human lungs and gas exchange
○ Plant gas exchange
○ Single celled/insects gas exchange
○ Fish gills
● Exchange surfaces
● Mass transport in animals
○ Haemoglobin
○ Circulatory system
○ Heart and cardiac cycle
● Mass transport in plants
○ Xylem - transpiration
■ Xerophytes
○ Phloem - translocation
● External vs internal environment
○ To survive, organisms transfer materials across plasma membranes between the
two environments
○ As animals increase in size, the ratio of their surface area to volume ratio
decreases e.g a baby has a larger SA to V ratio
○ For effective transfer
■ Larger surface area
■ Very thin - short diffusion distance
■ Selectively permeable
● Fick’s law
● Gas exchange
○ Single celled organisms
■ Diffusion over a large surface area
○ Insects
■ Trachea and tracheoles
■ Spiracles
■ Respiration gases move in and out of the tracheal system in 3 ways
● Along a diffusion gradient
● Mass transport
● The ends of the tracheoles are filled with water
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