Study the diagram of the geologic time scale.

which method is most likely used to identify what happened before the start of the paleozoic era?

a - scientists study fossils from the jurassic period.
b -scientists observe index fossil records of the mesozoic era.
c -scientists examine fossil evidence during the precambrian time.
d -scientists explore the emergence of mammals and humans in the cenozoic era.

If someone could do the first couple, just so i can see how it's done that would be great! 20 points. complete a dichotomous key for the 10 leaves on the common leaves sheet. the chart provided here allows for 11 pairs of statements. depending on how you build your dichotomous key, you may or may not need all of them, or you may need to add some.

Which of the following is a common danger of commercial fishing?

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.