3.1/2 Gas Exchange

Explain how the size of an organism affects its surface area to volume ratio and why this is important

As the size of an organism increases, the surface area : volume ratio decreases.

This is important for heat regulation, nutrient uptake and metabolic rate

how might a larger organism adapt to compensate for small sa;v

specialised gas exchange system, larger surface area eg folding

why cant insects use their bodies as an exchange system

they have a waterproof chitin exoskeleton and a small sa;v ratio in order to conserve water

name and describe 3 main featues of insects gas transport system

spiracles: holes on the body surface which my be opened or closed by a valve for gas or water exchange

trachae: large tubes extending through all body tissues supported by rings to prevent collapse

tracheoles: smaller branches dividing off the trachae

pulmonary ventilation rate

tidal volume x breathing rate , can be measured with spirometer

tidal volume

volume of air we breathe in and out during each breath at rest

expiration

• external intercolostal muscles relax, internal contract, bringing the ribs down and in

• diaphragm relaxes and domes upwards

• volume of thorax decreases

• air preessure inside lungs is therefore higher than the pressure outside so air moves out to rebalance

inspiration

• external intercolostal muscles contract, internal relac, pulling ribs up and out

• diaphragm contracts and flattens

• volume of thorax increases

• air pressure outside the lungs is therefore higher than pressure inside so air moves in to rebalance

explain why oxygen uptake is a measure of metabolic rate in organisms

oxygen used in respiration which is a metabolic process, provides atp

mammals such as a mouse and a horse are able to maintain constant body temperature. use knowledge of surface area to volume ratio to explain the higher metabolic rate of a mouse compared to a horse

as a mouse is smaller it has a larger surface area to volume ratio than a horse. this means faster heat loss per gram in relation to body size and faster respiration releases heat

Apply your knowledge of surface area : volume ratio to explain adaptations to body shape or the development of exchange systems Flattened shape

Flattened shape- organisms such as flatworms have a flattened shape, increasing their surface area : volume. Maximises surface area available for diffusion

Apply your knowledge of surface area : volume ratio to explain adaptations to body shape or the development of exchange systems Elongated shape

Elongated shape- some organisms like snake have elongated bodies. This increases surface area: volume aiding in more efficient gas exchange

Apply your knowledge of surface area : volume ratio to explain adaptations to body shape or the development of exchange systems Respiratory systems

Respiratory systems- larger organisms have developed respiratory systems to increase surface area for gas exchange.

Apply your knowledge of surface area : volume ratio to explain adaptations to body shape or the development of exchange systems Circulatory systems

Circulatory systems- to overcome limitations of diffusion over large distances, large animals have these systems to transport nutrients, gases and waste product

Describe and explain the relationship between surface area : volume ratio and metabolic rate

As sa:v increases, so does metabolic rate

Explain the adaptations of a single called organism for efficient gas exchange

The short diffusion pathway means that single cell organisms can rely on its cell surface for gas exchange.

explain the process of gas exchange in insects

• gasses move in and out of the tracheae through the spiracles

• a diffusion gradient allows oxygen to diffuse into the body tissue while waste co2 diffuses out

• contraction of the muscles in the tracheae allows mass movement of air in and out

why cant fish use their body as an exchange surface

they have a waterproof, impermeable outer membrane and a small surface area to volume ratio

Explain how the tracheal system is adapted to allow efficient gas exchange

Thin walls so short diffusion distance to cells

Large number of tracheols so large surface area for gas exchange

Body can be moved by muscles to move air so maintains a concentration gradient for oxygen

Explain how tracheal systems balance a need for oxygen and minimising water loss

Spiracle control- spiracles can open and close to regulate amount of air entering. By closing spiracles, insects minimise water loss

Describe the structure of fish gills

located within the body, supported by arches, along which are multiple projections of gill filaments, which are stacked up in piles

describe structure of lamellae

at right angles to fill filaments, give an increased surface area. blood and water flow across them in opposite directions

Explain how fish gills are adapted to maximise gas exchange

Counter current flow-

• the counter-current system is that it maintains a steep concentration gradient over the full length of the capillary.

• blood and water flow in opposite directions, water always next to blood of a lower oxygen concentration.

• diffusion gradient maintained along the length of lamella

name and describe three adaptations of a leaf that allow efficient gas exchange

1. thin and flat to provide short diffusion pathway and larger surface area to volume ratio

2. many stomata in the underside, allow gases to easily enter

3. air spaces in the mesophyll allow gases to move around the leaf, facilitating photosynthesis

how do plants limit their water loss while still allowing gasees to be exchanged

stomata regulated by guard cells which allows them to open and close as needed. most stay closed to prevent water loss while some open to let oxygen in

describe the pathway taken by air as it enters the mammalian gaseous exchange system

nasal cavity— trachea— bronchi— bronchioles— alveoli

nasal cavity function

a good blood supply warms and moistens the air entering the lungs. goblet cells in the membrane secrete mucus which traps dust and bacteria.

tracheae function

• wide tube supported by c-shaped cartilage to keep the air passafe open during pressure changes

• lined by ciliated epithelium cells which move mucus toward throat to be swallowed preventing lung infection

• carries are to the bronchi

Explain the role of cartilage in trachea and bronchi

Trachea Food must not go down with the air so when we swallow a flap of cartilage called the epiglottis closes over the entrance to the trachea.

Bronchi Here the cartilage is in small sections connected by muscle and elastic fibres. Provide structure and support preventing collapse.

Explain the role of ventilation in terms of maintaining diffusion gradients

The gradient is maintained by ventilation in the lungs coupled with the continuous flow of blood. Breathing movements constantly result in a change of air in the alveoli, providing fresh oxygen and removing carbon dioxide. Oxygen diffuses into the red blood cells. As the blood flow rapidly moves the red blood cells on, they are replaced by oxygen-poor cells. This ensures that the concentration of oxygen in the alveoli is always much higher than the concentration in the blood.

Explain mechanism of breathing

• When the muscles of the diaphragm contract, the dome flattens

• External inter colossal muscles contract.

• we move our ribs up and out to produce a larger increase in volume and decreases pressure in thoracic cavity (to below atmospheric, resulting in air moving in)

• Breathing out - Diaphragm relaxes and internal intercostal muscles contract

• (Causes) volume decrease and pressure increase in thoracic cavity (to above atmospheric, resulting in air moving out);

Explain the process of gas exchange, relating to ventilation and blood circulation

Without active ventilation, air could not reach our lungs at a rate even close to that needed to supply our oxygen needs. Our energy demands change, for example, when we start to run. So we must also vary the rate at which we ventilate our alveoli.

Describe the features of squamous epithelium

Thing flat cells closely packed together to form a smooth low friction surface

Thin reduces diffusion gradient. Rapid gas exchange

Larger surface area maximises diffusion

Permeable allows gasses to pass through easily

Smooth surface minimises resistance to airflow