Functional webs which emphasize the most important links in the food web. Line thickness relates to the importance of a link, which may or may not describe energy flow.

 

TLS Online TPP Program

#Id: 4452

#Unit 13. Methods in Biology

Thicker sections must be fixed, dehydrated, embedded in plastic, sectioned, and then stained with electron dense heavy metals for TEM.

TLS Online TPP Program

#Id: 4453

#Unit 13. Methods in Biology

For TEM two types of staining is done:

Negative staining

Metal shadowing

TLS Online TPP Program

#Id: 4454

#Unit 13. Methods in Biology

Negative staining- heavy metal coats the grid but is excluded from the regions where the sample has adhered.

TLS Online TPP Program

#Id: 4455

#Unit 13. Methods in Biology

Commonly used heavy metals

Uranyl acetate

Osmium tetraoxide 

TLS Online TPP Program

#Id: 4456

#Unit 13. Methods in Biology

Metal shadowing- thin film of platinum is coated from a fixed angle. it provides information about the three-dimensional topology of the sample.

TLS Online TPP Program

#Id: 4457

#Unit 13. Methods in Biology

Scanning electron microscopy (SEM) allows investigators to view the surfaces of unsectioned metal-coated specimens