Biology - organisms exchange substances with their environment

Why do fish need a specialised gas exchange system?

They have a small SA:V and impermeable membranes

What are the 4 features of the fish gas exchange system?

Gills, Gill arches, Gill filaments, Lamellae

What is the function and importance of the Gills?

They have lots of blood vessels so allow for efficient diffusion, They allow for the fish to extract oxygen from water

What is the function of the gill arches?

They hold gills in place and maintain space so that water can flow across the gill filaments

What is the function of the gill filaments?

Gill filaments are the main gas exchange surface. They are long thin structures that project from the gill arches, they are covered in lamellae, increasing surface area

What is the function of the lamellae?

They are thin structures that are packed with capillaries. The main process that occurs here is the countercurrent exchange flow, where blood and water flow in opposite directions in the capillaries to maintain a steep concentration gradient so oxygen is continuously diffused into the blood.

What are the steps of gas exchange in fishes?

1. Water enters mouth

2. Water flows over gill filaments

3. In the lamellae, oxygen diffuses from water into the blood

4. Carbon dioxide diffuses out into the water

What is ventilation and its importance?

The process of moving water over the gills. Water must continuously flow over the gills to maintain an oxygen gradient because the oxygen concentration in water is low and diffusion rate slows as the surrounding water becomes deoxygenated

What are the two ventilation processes?

Buccal pumping and Ram ventilation

What is the process of Buccal pumping?

This process forces water over the gills by a pressure difference.

1. Fish opens mouth, this lowers the floor of the buccal cavity so water flows in

2. Fish closes mouth, this raises the buccal floor so water is forced over the gils

3. Water exits from the operculum

What is the process of Ram ventilation?

1. Fish swims forward with mouth open

2. Water flows over gills automatically

Why do insects need a specalised gas exchange system?

They have a small SA:V so diffusion is slow

The waterproof exeskeleton prevents diffusion

What is the name of the insects specialised gas exchange system?

Tracheal system

What are the components of the tracheal system

Spiracles, Trachea, Treacheoles

Outline the structure and function of the spiracles

-Tiny pores on the body surface

-Allows gases in and out

Outline the structure and function of the trachea

-Large tubes which are supported by rings to prevent collapse

-Carries air directly into the body

Outline the structure and function of the tracheoles

-Tiny, thin tubes that branch off the trachea

-Site of gas exchange with cells

What are the 3 mechanisms of gas exchange in insects?

Diffusion, Mass transport, Water movement in tracheoles

Outline the diffusion path in insects

Oxygen diffuses down a concentration gradient.

Atmosphere→Spiracles→Trachea→Tracheoles→cells

Outline the mass transport mechanism in insects gas exchange

Insects contract their abdominal muscles to squeeze the trachea. 

This forces air in and out to maintain a steep gradient

Outline the water movement in the tracheoles as a mechanism of gas exchange in insects

In anaerobic respiration, lactate is formed which decreases the water potential. So water moves out of the tracheoles into the cells, this decreases the volume of the tracheoles, so air is drawn into the tracheoles. This increases the rate of diffusion

Outline 3 ways in which insects control water loss

1. Spiracles open/close to reduce evaporation

2. Waxy cuticle prevents water loss

3. Small SA:V minimises surface area for evaporation

Why do humans need a specialised gas exchange system

Humans are large, multicellular organisms with a high metabolic rate. Humans have a small SA:V, so diffusion is slow

What are the components of the respiratory system

Trachea, Bronchi, Bronchioles, Alveoli

Outline the structure and function of the trachea

The trachea is supported by rings of cartilage.

This prevents collapse

Outline the structure and function of the bronchi

The bronchi branches from the trachea, it carries air into each lung

Outline the structure and function of the bronchioles

The bronchioles are small tubes branching from the bronchi

They control airflow via muscle contraction

Outline the structure and function of the alveoli

The alveoli are tiny air sacs
They are the main site of gas exchange

Define ventilation

Ventilation is the mechanical process of moving air in and out to maintain a steep concentration gradient of gases

Outline the process of Inspiration (Inhaling)

1. External intercostal muscles contract, the internal intercostal muscles relax

2. The diaphragm contracts and falttens

3. The thoracic volume increases, lung pressure decreases → air moves in down a pressure gradient 

Outline the process of expiration (exhaling)

1. External intercostal muscles relax, internal intercostal muscles contract

2. Diaphragm relaxes

3. Thoracic volume decreases, lung pressure increases, so air moves out 

Outline the path of gas exchange in the alveoli

O₂  diffuses from the alveoli → travels across the alveolar and capillary epithelium → blood plasma → red blood cells

What is the equation to find pulmonary ventilation and what do each of the components mean

Pulmonary ventilation = Tidal volume x ventilation rate

pulmonary ventilation= vol of air moved in per min

tidal volume= vol of air in one breath

ventilation rate= breaths per min