Exchange between organisms and their environment

What is tissue fluid?

The environment around the cells of multicellular organisms

The smaller the organism, the ___ the surface area to volume ratio?

Larger

What do smaller organisms use for gas exchange?

Diffusion

Single-called organisms can diffuse substances in and out of the cell surface membrane

What are features for efficient gas exchange?

Large surface area

Large surface area to volume ration

Thin: short diffusion path

Selectively permeable

Movement of the internal medium to maintain a diffusion gradient

What is the relationship between surface area, difference in concentration and length of diffusion path?

What substance need to be interchanged between an organism and its environment?

Respiratory gases, nutrients (glucose, amino acids, minerals), excretory products (urea, CO2) and heat

Organisms with a high metabolic exchange rate require what?

A larger surface area to volume ratio