Please enable JavaScript.
Coggle requires JavaScript to display documents.
exchange and transport (specialised exchange surfaces (multicellular…
exchange and transport
specialised exchange surfaces
organisms need to exchange substances with their environment
cells need oxygen and glucose for metabolic processes e.g. aerobic respiration
they also excrete waste products e.g. carbon dioxide and urea
smaller animals have a higher SA:V ratio than larger animals
multicellular organisms need exchange surfaces
in single celled organisms substances can diffuse directly in/out of cell via cell membrane - the diffusion rate is fast as the diffusion distance is small
multicellular organisms have cells deep within body which means they have a large diffusion distance
larger animals have a low SA:V ration so its difficult to supply every cell with the substances they need through a small surface
multicellular organisms have a higher metabolic rate so they use oxygen and glucose faster
exchange surfaces have special features to improve efficiency
large SA, thin walls, moist, good blood supply and ventilation
e.g. root hair cells
the cells grow hair like structures which increase the surface area which increases the rate of osmosis and active transport
e.g. alveoli
gas exchange surface in lungs
each alveolus is made of a single thin layer of alveolar epithelium
O2 diffuses out of the alveolar space and into blood CO2 diffuses in opposite direction
the thin alveolar epithelium decreases diffusion distance, increasing rate
surrounded by a network of capillaries and the lungs are ventilated which help maintain a concentration gradient
e.g. fish gills
contain large network of capillaries and are well ventilated to help maintain a concentration gradient
gaseous exchange system in mammals
in mammals lungs are the exchange organ
1) air enters trachea through inspiration
2) the trachea splits into 2 bronchi
3) each bronchus branches off into bronchioles
4) the bronchioles end in alveoli where gases are exchanged
5) ribcage, intercostal muscles and diaphragm work together to move air in and out
structures in gaseous exchange system have different functions
goblet cells- secrete mucus, traps microorganisms and dust particles in inhaled air preventing them from reaching the alveoli
cilia- waft the mucus, this moves the mucus containing dust/pathogens upward to the throat to be swallowed preventing lung infection
elastic fibres- in the walls of trachea, bronchi, bronchioles and alveoli help process of expiration. on breathing in the lungs inflate and elastic fibres stretch, then the fibres recoil to help force air out in exhalation
smooth muscle- in walls of trachea, bronchi and bronchioles allows their diameter to be controlled, during exercise the smooth muscle relaxes and widens, this means there is less resistance to air flow and air can move in and out of the lungs more easily
rings of cartilage- in the walls of trachea (c shaped) and bronchi provide support. its strong but flexible and prevents the trachea and bronchi collapsing when you breath in and the pressure drops
ciliated= trachea, bronchi and bronchioles
ventilation in mammals
ventilation in mammals is breathing in and out
inspiration:
the external intercostal muscles and diaphragm muscles contract
this causes ribcage to move upwards and out and the diaphragm to flatten, increasing volume of the thorax (space where lungs are)
as the volume of thorax increases the lung pressure decreases (below atmospheric level)
this causes air to flow into lungs
inspiration requires energy (active process)
expiration:
the external intercostal muscles and diaphragm muscles relax
the ribcage moves downwards and inwards and the diaphragm becomes curved
the thorax volume decreases causing the air pressure to increase (above atmospheric level)
air is forced out of lungs
normal expiration is passive (doesn't require energy)
expiration can be
forced
by the intercostal muscles contracting to pull ribcage down and in
tidal volume is the volume of air in a normal breath
Tidal volume- the volume of air in each breath- usually around 0.4dm3
vital capacity- the maximum volume of air that can be breathed in or out
breathing rate- how many breathes are taken - usually in a minute
oxygen uptake/ consumption- the rate at which an organism uses up oxygen
spirometers can be used to investigate breathing
1) a spirometer has an oxygen filled chamber with a moveable lid
2) the person breathes through tube connected to the oxygen chamber
3) as the person breathes in and out, the lid of the chamber moves up and down
4) these movements can be recorded by a pen attached to the lid of the chamber- this writes on a rotating drum, creating a spirometer trace. Or the spirometer can be hooked to a motion sensor- this will use the movements to produce electronic signals, which are picked up by a data logger
5) the soda lime in the tube the subject breathes into absorb carbon dioxide
the total volume of gas in the chamber decreases over time. this is because the air that's breathed out is a mixture of oxygen and carbon dioxide. the carbon dioxide is absorbed by soda lime -so there's only oxygen in the chamber which the subject inhales from. s the oxygen gets used up by respiration, total volume decreases
ventilation in fish and insects
fish use a counter current system for gas exchange
1) water containing oxygen enters the fish through the mouth and passes out of the gills
2) each gill is made up of lots of gill filaments/ primary lamellae which give a large surface area. the gill filaments are also covered in secondary lamellae which increase the surface area further. each gill is supported by a gill arch
3) the gill plates have lots of blood capillaries and a thin surface layer of cells to speed up diffusion
4) blood flows through the gill plates in one direction and water flows over in the opposite direction (counter current). maintains a large concentration gradient
ventilation in fish
1) fish opens its mouth which lowers floor of buccal cavity. the volume of buccal cavity increases decreasing pressure, water is sucked in
2) when the fish closes its mouth, the floor of the buccal cavity is raised again. the volume decreases, pressure increases. the water is forced out of cavity across the gill filaments
3) each gill is covered by a bony flap called operculum. the increase in pressure forces the operculum on each side of the head to open, allowing water to leave the gills.
insects use tracheae to exchange gases
1) air is moved into tracheae via spiracles (pores on insects surface)
2) oxygen travels down concentration gradient towards the cells. carbon dioxide from the cells moves down its own concentration gradient towards the spiracles to be released into atmosphere
3) the trachea branch off into tracheoles which have thin permeable walls and go to individual cells. the tracheoles also contain fluid which oxygen dissolves in.
4) the oxygen then diffuses from this fluid into body cells. carbon dioxide diffuses in the opposite direction
5) insects use rhythmic abdominal movements to change the volume of their bodies and move air in an and out of the spiracles. when larger insects fly their wing movements pump their thoraxes too.