Adaptations for Exchange in Animals Flashcards
what does the rate of oxygen depend ?
depends on the surface area available for gas exchange.
surface area to volume ratio affects :
- the surface adapted for use for gas exchange
- the level of activity of the organism.
why might surface area to volume ratio decrease
As organisms increase in size, their surface area to volume ratio decreases and so specialised respiratory surfaces are needed.
what is needed when the surface area to volume ratio is decreased?
specialized respiratory surfaces
fish require specialized gas exchange surfaces as
- 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.
ventilation in bony fish
- Mouth opens, the floor of the buccal cavity lowers so volume increases, pressure decreases and water rushes in.
- Mouth closes, the floor of the buccal cavity raises, increasing pressure and pushing water over the
gills. - Pressure in gill cavity increases and water forces operculum open and leaves through it.
why do fish require a ventilation mechanism?
to push water, a dense medium with low oxygen content, over the high surface area gill filaments.
Removal from water causes these gill filaments to collapse, stick together and the gas exchange surface becomes too small for survival.
what do the gills contain?
gill filaments
gill lamellae
gill rakers
what does gill lamellae do?
act as the gas exchange surface
across which the water flows
function of gill rakers?
Gill rakers prevent large particulates
entering and blocking the gills.
gas exchange surfaces must be :
- 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 is continuous flow / parallel flow ?
If water and blood flow in the same direction,
equilibrium is reached and oxygen diffusion
reaches no net movement halfway across the
gill plate.
what is counter-current flow ?
If water and blood flow in opposite directions
across the gill plate, the concentration
gradient is maintained and oxygen diffuses
into the blood across the entire gill plate.
How AMOEBA’S adapt to the challenge of gas exchange:
*Single cell
*Large surface area to volume ratio
*Rate of oxygen diffusion through external surface meets demand. A low metabolic rate means oxygen demand is low.
*Thin membrane provides a short diffusion distance to the middle of the cell.
*simple diffusion
How FLATWORMS adapt to the challenge of gas exchange:
*Multicellular
*Smaller surface area to volume ratio
*Flattened body to reduce diffusion distance so rate of oxygen diffusion through body
surface meets demand
How EARTHWORM adapt to the challenge of gas exchange:
- cylindrical Multicellular
*Even smaller surface area to volume ratio
*Slow moving and low metabolic rate ∴ require little oxygen
*Rely on external surfaces for gas exchange but the circulatory system needed to distribute oxygen. The circulatory system transports oxygen to the tissues and removes
carbon dioxide, maintaining a steep diffusion gradient
*Mucus secreted to moisten surface and slow moving to reduce oxygen demand
what is the gas exchange surface for humans?
Alveoli
The gas exchange surface,
lined with a surfactant that
reduces surface tension
and prevents collapse
on exhalation.
ventilation in humans ?
inspiration
gas exchange in amphibia
They don’t ventilate like fish but movement of the gills through water maintains a
concentration gradient.
info you should pick out
Amphibia have soft, moist skin and exchange gases over their surface at rest.
Oxygen and carbon dioxide circulate through a closed circulation system containing hemoglobin.
When active, movements of the buccal
cavity ventilate lungs, which are simple with few alveoli.
how does an organisms size relate to its surface area to volume ratio?
the larger the organism the lower the surface area to volume ratio
how does surface area to volume affect the transport or molecules ?
the lower the SA/V ratio, the further the distance molecules must travel to reach all parts of the organism.
diffusion alone is not sufficient in organisms with small SA/V ratios
Why do larger organisms require mass transport and specialised gas exchange surfaces?
● Small SA/V ratio
● Diffusion insufficient to provide all cells with the required oxygen and to remove all carbon dioxide
● Large organisms more active than smaller organisms
- Name four features of an efficient gas exchange surface
● Large surface area
● Short diffusion distance
● Steep diffusion gradient
● Ventilation mechanism
define ventilation
The movement of fresh air into a space and
stale air out of a space to maintain a steep
concentration gradient of oxygen and
carbon dioxide.
Name the organ of gaseous exchange in fish.
gills
Name the organ of gaseous exchange in fish.
gills
what are gill filaments ?
● Main site of gaseous exchange in fish, over which water flows
● They overlap to gain resistance to water flow - slows down water flow to maximise the gaseous exchange
● Found in large stacks, known as gill plates, and have gill lamellae which provide a large surface area and good blood supply for exchange
Explain the process of ventilation in bony fish
● Buccal cavity volume increases and pressure decreases to enable water to flow in
● Contraction of the buccal cavity forces water across the gills
● Pressure in the gill cavity rises, opening the operculum.
Water leaves
How is a steep diffusion gradient maintained across the entire gas exchange surface in bony fish?
due to counter current flow
define counter current flow
Blood and water flow in opposite
directions across the gill plate.
How does counter-current flow maintain a steep diffusion gradient? What is the advantage of this?
● Water is always next to blood of a lower oxygen concentration
● Keeps rate of diffusion constant and enables 80% of available oxygen to be absorbed
What type of flow is exhibited in
cartilaginous fish
parallel flow
define parallel flow
Water and blood flow in the same
direction across the gill plate.
Name and describe the main features of
an insect’s gas transport system
● Spiracles - small, external openings along the thorax and abdomen through which air enters, and air and water leave the gas exchange system
● Tracheae - large tubes extending through all body tissues, supported by rings of chitin to prevent collapse
● Tracheoles - smaller branches dividing off the tracheae
What is the main site of gas exchange in
insects?
tracheoles
Describe the adaptations of the insect tracheal system to a terrestrial environment.
● Spiracles can be opened or closed to regulate diffusion
● Bodily contractions speed up the movement of air through the spiracles
● Highly branched tracheoles provide a large surface area
● Impermeable cuticle reduces water loss by evaporation
Describe the ventilation of the tracheal system in insects.
Expansion of the abdomen opens the thorax spiracles
(through which air enters) and closes the abdominal
spiracles
● Compression of the abdomen closes the thorax spiracles
and opens the abdominal spiracles (through which air is
expelled)
Compare the gas exchange surface of an active and inactive amphibian.
● Active amphibian has simple lungs
● Inactive amphibian relies on its moist
external surface for gas exchange
how are mammals adapted for gas exchange?
Alveoli provide a large surface area and thin
diffusion pathway, maximising the volume of
oxygen absorbed from one breath. They also
have a plentiful supply of deoxygenated blood, maintaining a steep concentration gradient.
describe the structure and function of the larynx
A hollow, tubular structure located at the
top of the trachea involved in breathing
and phonation.
Describe the trachea and its function in the
mammalian gaseous exchange system.
● Primary airway, carries air from the nasal cavity down into the chest
● Wide tube supported by C-shaped cartilage to keep the air passage open during pressure changes
● Lined by ciliated epithelial cells which move mucus, produced by goblet cells, towards the back of the throat to be swallowed. This
prevents lung infections
describe the structure of the bronchi
● Divisions of the trachea that lead into the lungs
● Narrower than the trachea
● Supported by rings of cartilage and lined by
ciliated epithelial cells and goblet cells
describe the structure and function of bronchioles?
● Many small divisions of the bronchi that allow the passage of air into the alveoli
● Contain smooth muscle to restrict airflow to the lungs but do not have cartilage
● Lined with a thin layer of ciliated epithelial cells
describe the alveoli
● Mini air sacs, lined with epithelial cells
● Walls one cell thick
● Good blood supply to maintain a steep diffusion gradient
● 300 million in each lung
what are pleural membranes ?
Thin, moist layers of tissue surrounding
the pleural cavity that reduce friction
between the lungs and the inner chest
wall
define pleural cavity
The space between the pleural
membranes of the lungs and the inner
chest wall.
what are intercostal muscles ?
A set of muscles found between the ribs
on the inside that are involved in forced
exhalation.
what are external intercostal muscles?
A set of muscles found between the ribs
on the outside that are involved in forced
and quiet inhalation.
Explain the process of inspiration and the changes that occur throughout the thorax.
● External intercostal muscles contract (while internal relax), raising the ribcage
● Diaphragm contracts and flattens
● Outer pleural membrane moves out, reducing pleural cavity pressure and
pulling the inner membrane out
● The alveoli expand. Alveolar pressure falls below air pressure so air moves
into the trachea
what is a surfactant ?
A fluid lining the surface of the alveoli that
reduces surface tension and prevents
collapse of the alveoli during exhalation.
function of waxy cuticle
Reduces water loss from the leaf
surface.
Describe how the upper epidermis is adapted for photosynthesis
● Layer of transparent cells allow light to
strike the mesophyll tissue
● Epidermal cells also synthesise the waxy
cuticle, reducing water loss
Where is the palisade mesophyll layer
located?
directly below the upper epidermis
How is the palisade mesophyll layer
adapted for photosynthesis?
It receives the most light so contains the
greatest concentration of chloroplasts.
How is the spongy mesophyll layer
adapted for photosynthesis?
● Contains air spaces that reduce the diffusion distance for carbon dioxide to reach the chloroplasts in the palisade layer
● Contains some chloroplasts
What is a vascular bundle?
The vascular system in dicotyledonous
plants. It consists of two transport
vessels, the xylem and the phloem.
Why are vascular bundles important in
photosynthesis?
They form a large network to deliver
water and nutrients to photosynthetic
tissues and remove glucose.
Describe how the lower epidermis is adapted for photosynthesis.
It contains many stomata which enable
the evaporation of water and inward
diffusion of CO2
Describe how the lower epidermis is adapted for photosynthesis.
It contains many stomata which enable
the evaporation of water and inward
diffusion of CO2
what are stomata?
Small holes found on leaves that can be
opened or closed by guard cells to
control gas exchange and water loss.
summarise the ‘malate theory’
The ‘malate’ theory states that the
accumulation or loss of malate and K+ ions
by guard cells results in changes in turgor
pressure that open or close the stomata
summarise the ‘malate theory’
The ‘malate’ theory states that the
accumulation or loss of malate and K+ ions
by guard cells results in changes in turgor
pressure that open or close the stomata
By what mechanism do K+
ions enter guard cells?
active transport
How does the accumulation of K+
and malate ions affect guard cells?
● Lowers the water potential of guard cells
● Water moves in by osmosis
● Guard cells becomes turgid, opening the
stomata
Why is starch important for the stomatal opening?
starch is converted into malate ions
