bio20b: form and function

what affects the way an animal interacts with its environment

its form, that is an animal’s size and shape

how do physical laws of water constrain evolution

water is roughly 1000x denser than air and is more viscous - anything that causes drag impedes the swimmer greatly. this caused the evolution of many fast swimming ocean animals to form a fusiform(tapered on both ends)

reasons for similar shapes of animals in the same environments

natural selection often results in similar adaptations when facing the same environmental challenges

how do physical laws influence animal body size

as body dimensions increase, thicker skeletons are required to maintain support aswell as muscles required in movement which must take up a greater fraction of the total body mass else mobility becomes limited.

what do animals exchange with the environment

nutritents, waste products, and gases with their environment

what does exchange mean in molecular terms

substances dissolved in an aqueous solution move across sthe plasma membrane of each cell

why are smaller, single celled organisms more efficient

a single celled organism such as a amoeba, has a sufficient membrane surface area in contact with its environment to cary out all necessary exchange.

surface area to volume relationship

the rate of exchange is proportional to the membrane surface area, whereas the amount of material that must be exchanged is proportional to the body volume.

what is required of a multicellular organization to work

if every cell has access to a suitable aqueous environment, either inside or outside the animal’s body

how do simple organisms maximize direct exchange of their cells

some animals have a body wall of two cell layers thick. Thus with an open cavity both layers of cells are routinely exposed to the environment.

Others maximize exposure with a flat shape which places most cells in direct contact with its particular environment

Explain the limitations of exchange surfaces in complex organisms

increasing the number of cells decreases the ratio of outer surface area to total volume.

A larger animal has more cells, nevertheless every cell must have access to nutrients

how are all cells of a larger animal involved in exchange

adaptations that allow sufficient exchange occur in specialized surfaces that are extensively branched or folded

what does branching and folding surfaces help achieve

this arrangement protects delicate tissues from cuts and dehydration.

its shape also increases the surface area

interstitial fluid

the spaces between cells are filled with fluid called interstitial fluid

internal body fluids link __ __ __ __ __

exchange surfaces to body cells

what enables all cells throughout the body to obtain nutrients and get rid of wastes

exchange between the interstitial fluid and a circulatory fluid (blood)