An important example of a "positive feedback loop" in the polar climate system is:
a. Scientists in remote places check on each others instruments.
b. Warming ocean water opens new areas for marine species.
c. Warmer winters cause more plant growth, providing more food.
d. Sea ice melt opens more ocean to sunlight, causing more melt.

Which is an advantage of having memory cells when a pathogen is encountered for a second time. a) the memory cells are what proliferate into clones of cells in response to the binding of an antigen. b) memory cells are vital to the primary immune response in that they immediately recognize pathogens even at the first encounter. c) memory cells are essentially effector cells that are short lived and attack antigens even without having a receptor specific to that antigen. d) it ensures that more lymphocytes with a receptor specific to a particular antigen will be present than in a host that had never encountered that pathogen.

When new rock is added to an oceanic ridge, the magnetized strips on either side of the ridge are evidence of sea-floor spreading. this is because the rocks on the two sides of the ridge o are equal in width and in polarity are polar opposites oare magnetized vary in width but are equal in polarity

As a review, define the terms autotroph and heterotroph. keep in mind that plants have mitochondria and chloroplasts and do both cellular respiration and photosynthesis!