BIOFOUND 5.4 Gas Exchange and Circulation pt 1

Gas Exchange

The process by which animals acquire oxygen (O₂) from the environment and expel carbon dioxide (CO₂), which is a waste product of cellular respiration.

Respiratory Surface

A thin, moist area across which gases are exchanged; must have a large surface area and be permeable to gases.

Respiratory System

Organs and structures involved in ventilation and gas exchange (e.g., lungs, gills, tracheae).

Circulation

The movement of fluids (blood or hemolymph) that transports gases between the respiratory surface and cells.

Blood and Hemolymph

Fluids that carry oxygen and carbon dioxide in vertebrates (blood) and invertebrates (hemolymph).

Circulatory System

A system of vessels and pumps (like the heart) that moves blood or hemolymph to transport gases, nutrients, and waste.

Pressure Gradient

A difference in pressure between two areas that drives gas movement from high to low pressure.

Partial Pressure

The pressure a specific gas contributes to the total pressure of a gas mixture; gases move from areas of high to low partial pressure.

Fick’s Law of Diffusion

the physical law that governs how fast molecules diffuse Rate of Diffusion = k x A x (P2-P1)/D

K

a physical constant in Ficks Law that is specific to each gas

A

the surface area available for gas exchange in Ficks Law

What happens to rate of diffusion as surface area increases?

rate of diffusion will increase as surface area increases

(P2-P1)

In Ficks law, the partial pressure gradient, the larger the pressure gradient the faster the gas will diffuse

D

In ficks law, the distance that the gas must diffuse

What happens to the rate of diffusion as distance increases?

As distance increases the rate of diffusion will decrease

Major Tasks of the Respiratory System

1) Move oxygen into the body, 2) Remove carbon dioxide from the body.

Gas Movement at Respiratory Surface

Oxygen enters the body; carbon dioxide exits the body.

Fish Ventilation and Gas Exchange

Use gills with large surface area and thin membranes to facilitate diffusion

Buccal Pumping

Mouth opens and closes to force water over gills in Fish Gas Exchange

Ram Ventilation

Fish swim with mouths open to drive water over gills during Gas Exchange

Gill Structure

Includes gill arches, filaments, and lamellae to maximize surface area and minimize diffusion distance during Gas Exchange

Terrestrial Invertebrate Ventilation and Gas Exchange

Use a tracheal system, a network of air-filled tubes that deliver O₂ directly to cells

Spiracle

Small openings on the body surface that let air in and out during terrestrial invertebrate gas exchange

Tracheal Ventilation

Body movements or muscle contractions help ventilate the system during terrestrial invertebrate gas exchange

Terrestrial Vertebrate Ventilation and Gas Exchange

Use lungs with branching bronchi and bronchioles ending in alveoli

Alveolus

Tiny air sac with thin walls surrounded by capillaries for gas exchange during terrestrial vertebrate gas exchange