C3: Adaptations for Gas exchange in animals Flashcards
What must gas exchange surfaces be?
5 points
be moist - in terrestrial animals
be thin - (short diffusion pathway)
have a large surface area
be permeable to gases
have a good blood supply - to maintain concentration gradients (larger organisms only).
What does the amount of oxygen an organism needs depend upon?
The volume of the organism the higher it is the more oxygen is needed because more cells are respiring and metabolically active
What does the surface area to volume ratio of an organism affect
- the surface adapted for use for gas exchange
- the level of activity of the organism.
What does the rate at which oxygen is absorbed depend upon
3 points
Concetration gradient
surface area
diffusion distance
Why can insects not use their external surface for gas exchange?
Insects cannot use their external surface for gas exchange as they are covered in an impermeable cuticle layer to reduce water loss by evaporation. this lies over a thick chitin exoskeleton
In addition they have a relatively small surface are to volume ratio
Describe the structure of respiratory system of insect
The tracheael system consists of the spiricle and a system of chitin lined tracheae and trachaeoles
Describe the ventilation of an insect and its adaptations under intense activity
Oxygen within the air travels in through Spiricles (these are holes on the abdomon and the thorax) and enter the trachae and then into smaller tracheoels which provide a route directly to the muscles at the end of these tubes is fluid which allow the gases to dissolve in and then diffuse across the membrane to the working muscle.
during periods of activity the fluid layer shrinks making the diffusion distance smaller and the Whole body contractions aid ventilation by speeding up the movement of air through the spiracles.
Why do
Fish require a specialised gas exchange surface
3 points
- they have a smaller surface area to volume ratio
- they are relatively active and so have high metabolic rates making oxygen requirements high
- they require a ventilation mechanism to maintain concentration gradients for gas exchange.
Describe ventilation in bony Fish
Mouth Opens
buccal cavity lowers - pressure decreases as volume increases so water flows in
mouth shuts- pressure increases as volume decreases so water in forced through the gills as the operculum opens to let water out
Name three components of the Gill and its cover in bony fish
gill arch
filament
lamellae
operculum- gill cover
How is the ventillation system different in cartilaginous Fish then to bony fish and which is more effiecient
They do not have a special mechanism to force water over the gills and instead rely on movement so must keep swimming
in cartilaginous fish the blood flows in the same direction to the water which means a concentration gradient is not maintained and concentration of O2 never exceeds 50% as an equilibrium is eventually reached this is called parallel flow
whereas:
In bony fish the blood flows in the opposite direction to the water which maintains a concentration gradient in a system called counter current flow which and do not need to keep swimming which is more effiecient.
Describe the structure of the human gas exchange system
10 points
Larynx leading to trachea
trachea (semi circles of cartilage so its flexible )
bronci
bronchioles
alveoli
ribs
external and internal intercostal muscles
pleural membranes ( lubricant)
pleural fluid - in the pleural cavity
diaphram
Describe. The steps of ventilation in humans during inspiration
4 points
When the external intercostal muscles contract they raise the ribcage.
at the same time the diaphram contracts to become flat
so volume of the thorax (chest) increases.
The outer pleural membrane is pulled out.
This reduces pressure in the pleural cavity and the inner pleural
membrane moves outward.
This pulls on the surface of the lungs and causes the alveoli to expand.
As a result alveolar pressure decreases to below atmospheric pressure and air is drawn into the lungs.
Describe gas exchange in the Alveolus
5 points
provide a large surface area relative to human volume
gases dissolve in the surfactant which lines the alveoli Surfactant in the alveoli reduces surface tension and prevents the alveoli collapsing during exhalation.
walls have squamous epithelium, one cell thick so diffusion distance is small
an extensive capillary network to maintain diffusion gradient
the capillary walls are one cell thick contributing to the short diffusion pathway for gasses
Describe gas exchange in amphibians eg as a tad pole and a frog
As a tad pole their enviroment is aquatic so the respiratory surface is their gills but as they mature they develop lungs and lose thier gills.
as a result they use their lungs when on land but also thier skin, as it has a good blood supply, is kept moist by mucas secretion and it is permeable to gases. this suits thier envirmonet as it is both on land and in water in which case they use their skin as a main source
