Quaestio: How do our model organisms perform the life process of transport?

Nunc Agenda:Think about the path food takes. What

happens to those nutrients after they are absorbed through the villi of the small

intestine?

What is Transport?• Transport: The life process by which

substances move into or out of cells or are distributed within cells.

• Remember, every cell requires substances from the environment to survive and all organisms need to have a way of getting materials to and from each cell. – Question: Can you name some of these materials?

Key ideas• Nutrients, gases, and wastes must be

transported throughout the organism

• Small animals have cells in direct contact with the environment so diffusion alone is sufficient for transport

• Larger, more complex organisms require circulatory systems to move materials within the body

A circulatory system must have 3 parts:

– 1. A fluid in which materials are transported.

– 2. A network of tubes or body spaces through which the fluid flows.

– 3. A way of pumping fluid through the tubes or spaces.

Protozoans• Unicellular

• Perform cell transport through diffusion and active transport

• Cell is in direct contact with the external environment

Diffusion

Hydra– Recall: Hydras have two

layers of cells.• The Ectoderm• The Endoderm

–Both cell layers are in direct contact with the external environment.

–Materials pass by diffusion and active transport

Earthworm

• Large and complex• All cells NOT in contact with the external

environment• Closed –circulatory system– Transports materials around the body within tubes

or blood vessels

Earthworm anatomy• 4 main parts of circulatory system– Dorsal vessel • On top – over the digestive tract

– Ventral vessel• On bottom – below the digestive tract

– Aortic arches• 5 “hearts” that force blood down the ventral vessel

– Capillaries• Smallest blood vessels - allows for diffusion of materials

in and out of cells

Top View

Top View

Aortic Arches

Earthworm blood

• Blood = a fluid that carries nutrients, gases, wastes, water, and other dissolved substances

• No red blood cells – But do have hemoglobin-like pigments to carry O2

Earthworm Circulation• Aortic arches pump blood

into the ventral blood vessel

• Blood then enters the dorsal vessel at the posterior end and return to heart

• Capillaries branch off the main vessels

Grasshopper circulation• Open – circulatory system– Blood flows within vessels some of the time, but

in other areas blood flows directly into body spaces called sinuses

– Blood directly bathes cells for exchange of materials

Grasshopper Circulatory System: Side View

Grasshopper circulation

• Single blood vessel = the aorta– Dorsal (on back)

• A tubular set of hearts is located along the back of the animal.– Blood moves through a dorsal blood vessel and then out

into sinuses and directly bathes cells.– Blood then reenters blood vessels.

Grasshopper Blood• Grasshopper blood does not contain hemoglobin.

It is actually called hemolymph.– It is colorless.

– It does not transport O2 or CO2.• These respiratory gases are transported on a different

pathway.

– Hemolymph’s function is to transport nutrients and wastes.

Comparison Of Open And Closed Circulatory Systems

Questions:

• What are the main parts of a circulatory system?

• Name the processes that are involved in the transport of materials in protists.

• How does a closed circulatory system differ from an open circulatory system?

• What type of circulatory system do you expect to find in a bee?