7.4- ventilation and gas exchange in other organisms

Why do single celled organism not have a gas exchange system?

Due to single celled organisms having a small size, they have a large surface area where gas exchange can occur. They also developed a thin surface membrane which makes the diffusion pathway shorter

Why do insects have a rigid exoskeleton?

The waxy coating of the exoskeleton is impermeable to gases which prevents water loss and provides protection

What’s a tracheal system?

The tracheal system is a gas exchange system in insects made of tubes (tracheae) that carry air directly to tissues through spiracles.

What are the pores on the trachea called?

Spiracles

What are spiracles?

spiracles are pores on the surface of the insects trachea that allow air in and out

What are sphincter?

Circular muscles that can contract to close the spiracles or relax to allow it to open, where air moves through.

What’s the trachea in insects?

A tube lined with chitin which branches into smaller tubes known as tracheoles

Why are the tracheal tubes lined with chitin?

The tracheal tubes being lined with spirals folds of chitin acts like a reinforcing wire that keeps the airways open during body movement

What are the properties of tracheoles?

Very small, thin, permeable walls, and numerous tubes that reach individual cells, providing a large surface area for diffusion of gases.

What helps move air inhaled and out of the spiracles in insects?

Body movements (e.g. abdominal contractions) and changes in pressure within the tracheal system help ventilate air.

What happens to the fluid in tracheoles when energy demand increases?

The fluid level decreases as it is drawn into surrounding tissues, increasing the surface area for faster oxygen diffusion.

Why does fluid level decrease at the end of the tracheoles?

During high respiration demand, lactic acid builds up in muscles, lowering water potential. Water moves out of tracheole fluid into tissues by osmosis, exposing more surface for gas exchange.

Why is insect blood yellowish green

Insects do not have red blood cells but instead have haemolymph

What are gills?

Specialised respiratory organs in fishes where gas exchange occurs between water and blood.

What are gills filament?

Thin, highly folded structures in fish gills that provide a large surface area for gas exchange.

Where are lamellae present?

Lamellae are present in the surface of the gill filaments

What are lamellae?

Thin plate-like structures on gill filaments that increase surface area and contain many capillaries for gas exchange.

How is the lamellae specialised for their function?

They are thin with a large surface area and a rich capillary network, giving a short diffusion distance and maintaining a steep concentration gradient.

What is a counter-current system?

A system where water and blood flow in opposite directions across the gill lamellae, maintaining a steep concentration gradient for efficient gas exchange.

What are the steps of ventilation occurring in fishes?

1. Mouth opens, buccal cavity floor is lowered → water drawn in.

2. Mouth closes, buccal cavity floor is raised → water forced over gills into the opercular cavity

3. Mouth is closed and operculum opens → water exits past gill lamellae through the operculum

How to do a fish dissection

1. Place fish on tray and secure it.

2. Cut open the operculum and body wall.

3. Expose gills and identify filaments and lamellae.

4. Observe structure carefully without damaging tissues.