Transcript Skin Breathers - Nayland College

Skin Breathers
Skin Breathers - Earthworms

These animals use
their skin as their gas
exchange organ.

To maintain a moist
surface area they
secret mucus. If they
dry out they will
suffocate.

What happens
when it rains?

What happens
when it is dry?
Where did we find
them? (our soapy water

investigation)
Skin Breathers

Gases such as oxygen and carbon dioxide
can only diffuse about 1 mm into an
organism. That puts a limit to how big an
organism can get.

Worms are clearly bigger than that. How
have worms managed to grow to such
sizes?
Skin Breathers

How have earthworms managed to
obtain:



A large surface area?
A thin membrane?
A moist surface area?

How is the earthworms' gas exchange
system suited to their way of life?

What about those critters living in water?
Segmented worms found in
marine environments

Class Polychaeta. = "many bristles.“

The bristles are filled with blood vessels.They increase
the worm's surface area for gas exchange.

The circulatory systems of many polychaetes contain
haemoglobin … allows the worms to live in stagnant
mud where food is plentiful but oxygen is scarce.
Diffusion across a membrane



Hydra
Animals with central
cavity filled with water.
Their bodies are only
two cell layers thick
Diffusion across a membrane
Simple animals that lack
specialized exchange
surfaces have flattened,
tubular, or thin shaped body
plans, which are the most
efficient for gas exchange.
However, these simple
animals are rather small in
size.
Single celled organism

Single celled organisms exchange gases directly
across their cell membrane. However, the slow
diffusion rate of oxygen and carbon dioxide limits
the size of single-celled organisms.
Biozone p190