AQA AS BIOLOGY 7401/1 Paper 1 Question Paper & Mark scheme June 2023 VERIFIED 100%

AQA AS BIOLOGY 7401/1 Paper 1 Question Paper & Mark scheme June 2023 VERIFIED 100% What are the advantages of multi-cellular organisms? - --able to move -able to hunt(likely to he in top if food chain) -able to adapt to environment -specialised body reigons -able to find a mate What are the disadvantages of multi-cellular organisms? - -As they get bigger diffusion is less efficient and specialised exchange surfaces are needed Single felled organisms have a __________ surface area to volume ratio - -Large How is oxygen obtained in a single felled organism? - -Oxygen is absorbed across body surface by diffusion carbon dioxide given off in a similar way How does gas exchange occur in insects? - -As tracheoles carry oxygen to tissue oxygen is used up creating a low concentration of oxygen. This causes gaseous oxygen to be drawn into tracheoles diffusing into n dioxide produces causes a concentration gradient in the opposite direction and CO2 travels along trachea into the atmosphere How does mass transport link to gas exchange in insects? - -Muscles in the trachea contract and squeeze air through the trachea speeding up gas exchange Why does the water in the end of tracheoles have an effect on gas exchange? - -Lactate produced by anaerobic respiration causes water potential in muscle cells to become lower. This means water in the end of tracheoles to move into muscle cells by osmosis. The loss of water in the tracheoles causes a low pressure which draws in more air What is a spiracle what does it do? - -Spiracles are tiny pores in the trachea in which gases enter and exit. Spiracles May open or close though the use of valves Insects are small hence have a ________ diffusion pathway - -Short Fish have a ______ surface area to volume ratio, which means? - -Small SA:V ration meaning the body cannot supply and remove realities gases easily Why is the structure of the gills? - -The Gill is broken up into smaller sections called gill filaments which are stacked up in a pile at a right angle top of each other called the gill lamella which increases SA What is oxygen taken from in gas exchange in fish? - -Water taken in through the mouth Blood flows in the _______ direction to water in fish this is caked ___________ - -Opposite Counter current flow How does counter current exchange work? - -Water and blood flow in opposite directions, water has a high concentration oxygen