Ap Biology Chapter 42 Guided Reading Answer Key

Affiliate 42

Circulation and Gas Exchange

Lecture Outline

Overview: Trading Places

Every organism must exchange materials with its surround, and this exchangeastward ultimately

occurs at the cellular level.

oThe resources that fauna cells need, such every bit nutrients and oxygen, motility across the

plasma membrane to the cytoplasm.

oMetabolic wastes, such as carbon dioxide, move out of the cell.

In unicellular organisms, exchanges occur directly with the external surroundings.

Multicellular organisms take specialized systems for exchanging materials with the

surroundings and for transporting system materials betwixt sites of commutation and the residual of

the trunk.

For aquatic animals, structures such every bit thouills present an expansive surface area to the outside

surroundings.

Oxygen dissolved in the surrounding water diffuses across the thin epithelium covering the

gills and into a network of tiny blood vessels (capillaries).

At the same time, carbon dioxide diffuses out into the water.

oDiffusion is rapid due to the short distances involved.

Pumping of the heart moves oxygen-rich blood from the gills to the other tissues of the torso.

At that place, further short-range substitution of gases, nutrients, and wastes occurs.

Concept 42.1 Circulatory systems enable substitution at a distance

Diffusion alone is not adequate for transporting substances over long distances in animals—

for example, for moving glucose from the digestive tract and oxygen from the lungs to the

brain of a mammal.

Diffusion is insufficient over distances of more than than a few millimeters because the time it

takes for a substance to diffuse from ane place to another is proportional to the squardue east of the

distance.

oFor example, if it takes i 2nd for a given quantity of glucose to diffuse 100 µm, it volition

accept 100 seconds for information technology to diffuse ane mm and about 3 hours to diffuse ane cm.

The relationship between altitude and diffusion time places a chiliadajor constraint on the trunk

plan of animals.

Ane solution is a body size and shape that bring many or all cells in direct contact with the

environs.

Lecture Outline for Campbell/Reece Biology, 9th Edition, © Pearson Education, Inc. 42-1

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