Keystone species - Species within a community that has a role out of proportion to its abundance. Pisaster (starfish) preyed on a variety of intertidal organisms Beaver , Fig Tree, Digs

TLS Online TPP Program

#Id: 4322

#Unit 11. Evolution and Behavior

TLS Online TPP Program

#Id: 4323

#Unit 11. Evolution and Behavior

 Pasteur made a series of flasks with long, twisted necks (“swan-neck” flasks)

TLS Online TPP Program

#Id: 4324

#Unit 11. Evolution and Behavior

His design allowed air inside the flasks to be exchanged with air from the outside, but prevented the introduction of any airborne microorganisms, which would get caught in the twists and bends of the flasks’ necks.

TLS Online TPP Program

#Id: 4325

#Unit 11. Evolution and Behavior

If a life force besides the airborne microorganisms were responsible for microbial growth within the sterilized flasks, it would have access to the broth, whereas the microorganisms would not.

TLS Online TPP Program

#Id: 4326

#Unit 11. Evolution and Behavior

He correctly predicted that sterilized broth in his swan-neck flasks would remain sterile as long as the swan necks remained intact.

TLS Online TPP Program

#Id: 4327

#Unit 11. Evolution and Behavior

However, should the necks be broken, microorganisms would be introduced, contaminating the flasks and allowing microbial growth within the broth.