BIOLOGY MODULE 3 (papers 1 & 3) Flashcards
exchange and tranport, transport in animals, transport in plants
what is the ease of exchange of substances dependent on?
- organisms SA:V
- smaller animals have larger SA:V
why do multicellular organisms need exchange surfaces?
cannot rely on diffusion alone:
- some cells are deep within the body - diffusion distance too large
- smaller SA:V so hard to exchange enough substances to supply large volume
- high metabolic rate so use oxygen and glucose faster
what special features do exchange surfaces have to improve efficiency?
large SA e.g. root hair cells
thin e.g. alveoli
good blood supply and/or ventilation e.g. fish gills & alveoli
how are root hair cells adapted to improve efficiency of exchange surfaces? (SA)
- large SA
- increases rate of absorption of water and mineral ions
how is the alveoli adapted to improve efficiency of exchange surfaces? (THIN)
- each alveolus made from single layer of thin, flat cells (alveolar epithelium)
- O2 diffuses out alveolar space into blood, CO2 diffuses in opposite direction
- thin alveolar layer decreases diffusion distance when O2 and CO2 diffusion happens which increases rate of diffusion
how is the alveoli adapted to improve efficiency of exchange surfaces? (VENTILATION/BLOOD SUPPLY)
- have large capillary network, giving each alveolus its own blood supply
- lungs are ventilated so air constantly replaced
- helps maintain O2 and CO2 concs
how are fish gills adapted to improve efficiency of exchange surfaces? (VENTILATION/BLOOD SUPPLY)
- gas exchange surface in fish
- O2 and CO2 exchanged between fish’s blood and surrounding water
- gills = large network of capillaries - well supplied with blood
- well-ventilated so fresh water constantly passes over gills
- maintains conc gradient of O2 and increases rate of O2 diffusing into blood
what are the exchange organs in mammals?
the lungs
how are the lungs the exchange organ in mammals?
- as you breathe in, air enters trachea
- trachea split into 2 bronchi (one bronchus to each lung)
- bronchus branches off to bronchioles
- bronchioles end in alveoli where gases are exchanged
- ribcage, intercostal muscles & diaphragm move air in and out
what are the structures in the gaseous exchange system?
- goblet cells
- cilia
- elastic fibres
- smooth muscle
- rings or cartilage
what are goblet cells?
- secrete mucus
- mucus traps microorganisms and dust
- stops them reaching alveoli
what are cilia?
- beat the mucus
- moves mucus upward away from alveoli and towards throat
- prevents lung infections
what are elastic fibres?
- in walls of trachea, bronchi, bronchioles and alveoli
- help process of breathing out
- on breathing in, lungs inflate and elastic fibres are stretched, fibres recoil and push air out
what is smooth muscle?
- in walls of trachea, bronchi and bronchioles
- allows diameter to be controlled
- exercises makes smooth muscle relax & tubes widen so less resistance to air flow in and out lungs
what are rings of cartilage?
- in walls of trachea and bronchi
- provide support
- strong but flexible so stops trachea and bronchi collapsing when breathing in
which epitheliums are ciliated in the lungs?
trachea
bronchi
larger bronchiole
smaller bronchiole
which epitheliums are not ciliated in the lungs?
smallest bronchiole
alveoli
what is ventilation in mammals?
breathing in and out
what happens during inspiration?
- external intercostal & diaphragm muscles contract
- causes ribcage to move up & out and diaphragm flatten, increasing volume of thorax
- when thorax volume increases, lung pressure decreases
- causes air flow into lungs
- active process - requires energy
what happens during expiration?
- external intercostal & disphragm muscles relax
- rubcage moves down & in
thorax volume decreases, air pressure increases - air forced out lungs
- passive process - doesnt require energy
- expiration can be forced (internal intercostal muscles contract)
what is tidal volume?
volume of air in each breath
what is vital capacity?
maximum volume of air that’s breathed in and out
what is breathing rate?
how many breaths are taken (usually per min)
what is oxygen consumption/oxygen uptake?
rate that an organism uses up oxygen
what can be used to investigate breathing?
spirometer
how does a spirometer work?
- has oxygen-filled chamber with movable lid
- person breathes through tube connected to oxygen chamber
- when breathing, chamber moves up and down
- movements recoded with pen attached to lid of chamber (spirometer trace)
- soda lime in tube breathes into absorbs CO2
what happens to the total volume of gas in the chamber?
- decreases over time as air thats breathed out is a mixture of CO2 and O2 but CO2 is absorbed by soda lime
- oxygen gets used up in respiration
explain how fish use a counter-current flow system for gas-exchange
- water enters fish’s mouth and passes out through gills
- gill plates have thin surface layer of cells to speed up diffusion
- blood flows through gill plates in one direction and water flow in opposite direction (counter current)
- conc of oxygen in water is always higher than in blood
what is the structure of a gill?
- made of thin branches (gill filaments) so have a large SA for gas exchange
- gill filaments are covered by many gill plated
- each gill supported by a gill arch
how are fish gills ventilated?
- fish opens mouth, lowering floor of buccal cavity
- volume of buccal cavity increases, decreasing pressure in cavity so water is sucked in
- when fish closes mouth, floor of buccal cavity raises so volume inside cavity decreases, pressure increases so water is forced out across gill filaments
- each gill’s covered by a bony flap (operculum) to protect gill
- increased pressure forces operculum on each side of head to open so water leaves gill
how do you dissect a gill?
- place fish on dissection tray
- push back operculum and use scissors to remove gills
- cut each gill arch through bone at top and bottom
- draw gill and label it
what do insects use to exchange gases?
tracheae
how do insects use tracheae to exchange gases?
- air moves into tracheae through pores on insect surface (spiracles)
- oxygen goes down conc gradient to cells, CO2 from cells moves down its own conc gradient to be released into atmosphere
- tracheae branch off into smaller tracheoles & have thin, permeable walls
- tracheoles also contain fluid that O2 dissolves in
- O2 diffuses into body cells, CO2 diffuses in opposite direction
how do you dissect the gaseous exchange system in insects?
- fix insect to dissecting board
- examine tracheae, then cut & remove exoskeleton from abdomen
- use syringe to fill abdomen with saline solution to see tracheae (looks sliver)
- can examine tracheae under light microscope with wet mount, should see rings of chitin in walls of tracheae
what is the circulatory system like in a fish?
- single
- closed
- heart pumps deoxygenated blood to gills and then blood goes oxygenated from gills to rest of the body, then turns deoxygenated and goes back to heart
what is the circulatory system like in a mammal?
- double
- closed
- right side pumps doxygenated blood to lungs
- from lungs blood goes oxygenated and travels back to the heart, then to the left side to rest of the body
- from rest of the body it goes to the heart, when blood enter heart, it enters right side again
which system sends blood to the lungs?
pulmonary system
which system sends blood to the rest of the body (not lungs)?
systemic system
what is the advantage of the mammalian double circulatory system?
can give blood an extra push between the lungs and rest of the body - oxygen is delivered to tissues more quickly
what is a closed circulatory system?
- blood is enclosed within blood vessels
- heart pumps blood to arteries which branch out into capillaries
- substances diffuse from blood in capillaries into body cells but blood stays
- veins take blood back to heart
what is an open circulatory system?
- blood isnt enclosed in blood vessels all the time
- heart is segmented so contracts in a wave starting from the back, pumping blood into single main artery
- artery opens up into body cavity
- blood flows around insects organs, makes its way back to heart through valves
how does an open circulatory help an insect?
supplies insects cells with nutrients
how do the insects cells get supplied with oxygen?
done by a system of tubes called tracheal system