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Flashcards in gas exchange Deck (33)
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how do you achieve the best diffusion rates

large area
moist ( allow a medium in which gases can dissolve)
diffusion path must be short


what is gas exchange

the diffusion of gases down a concentration gradient across a respiratory surface between or organism and its environment. the gases being exchanged are CO2 and 02


how do amoeba perform gas exchange

use the cell membrane as a gas exchange surface. the diffusion can occur through the membrane as it is:
thin - moist - permeable - diffusion path is short


what is a flat worm and what advantage does it have

aquatic organism
very flat so large surface area
diffusion pathways are short


what is an earthworm and what advantage does it have

cylindrical less surface area
their skin is the respiratory surfaces they secrete out a mucus to make their skin soft
they have haemoglobin to carry the oxygen away from the surface in order to maintain a concentration gradient


characteristics of insects

most live in dry habitats
small surface area to volume ratio
inefficient gas exchange
waterproof layer covering surface to prevent water loss


describe the respiratory system of an insect

every segment has a spiracle leads into a trachea which leads into tracheoles and goes to all respiring cells in body
ventilation to change pressure


describe gas exchange in humans

gas exchange occurs in the lungs
connected to the outside air with a set of tubes
the trachea starts at the back of the mouth and branches to form 2 bronchi
one bronchus goes into each lung
each bronchus branches many times getting smaller to form tubes called bronchioles
at the end of the bronchioles are alveoli
each alveolus is folded for a set of interconnected spaces there are many alveoli providing a large surface area for gas exchange
the alveoli surrounded by blood capillaries transporting blood to and from the lungs


how does inspiration in humans work

ribcage expands as rib muscles contract
impulse from brain causes intercostal muscles to contract
diaphragm contracts
air pressure in lungs decreases
air movement into lungs
lung volume increases


how does expiration in humans work

rib cage gets smaller as rib muscles relax
no nerve impulses are sent
diaphragm relaxes and air pressure in lungs increases
air movement out of lungs
lung volume decreases


what are antagonistic muscles

internal and external intercostal muscles


what is expiration assisted by

elastic recoil of the lungs following the stretch of elastic fibres


what happens during exercise

impulses are sent to contact internal intercostal muscles for a more forceful expirations and contraction of the abdominal muscles to push the diaphragm into a more domed position


where does gas exchange in fish occur

in gills which are supported by a gill arch which is made of bonds
the space between the gill arch is called gill slit
each gill has two rows of gill filaments which are covered in folds called lamellae


what is the distance between water and blood cells

5 micrometres


what is the distance between 2 lamellae

50 micrometres


how are lamellae kept apart

water holds them open


how does passive ventilation in fish take place

swim forward with mouth open
point mouth upstream


how does active ventilation in bony fish take place

1- mouth opens and operculum closes
2- buccal cavity lowers so volume increases, pressure decreases which creates a pressure difference so water flows in
3- mouth closes and operculum opens
4- buccal floor raises and pressure increases
5- water if forced across gills, gill cavity pressure increases
6- operculum opens


how does parallel flow work

cartilaginous fish have no special mechanism to force water over the gills, they rely on swimming for ventilation
blood travels the same direction as water


what is the concentration limited to in parallel flow

50% as it reaches a concentration equilibrium and no longer has a concentration gradient


what part of the gill lamella does parallel flow use

only part of it


how does counter current flow work

blood in the gill capillaries flows in the opposite direction to the water flowing over the gill surface
water has a higher oxygen concentration than the blood


why is counter current flow a more efficient system

it used the whole gill lamella as water has a higher oxygen concentration than the blood at all times


what percentage of oxygen can the gills remove from the water



what happens to plants in darkness

no photosynthesis takes place only respiration
the plant doesnt use a transport system
each cell obtains gases it needs by difusion


what adaptations do plants have

cuticle - prevents gas exchange in that area and prevents water loss
stomata - gases come in
large surface area and thin
spongy mesophyll - gas exchange occurs, moist and diffuse into mesophyll
palisade mesophyll contains lots of chlorophyll


how do plants combat water loss

stomata opens and closes
water evaporates from the wet cell walls in and contact with any air spaces in the leaf and is lost by transpiration


what other adaptations do plants have

surface of mesophyll cells in contact with air spaces in leaf
surface is large and diffusion distances are small
so gases only have to travel across a single cell


how do you reduce water loss in plants

high humidity
low temp
out of the wind
closing the stomata