Amarine ecologist counts the number of crabs in three different intertidal regions that are each two hectares. the crab counts are 7, 2, and 6, respectively. what is the best estimate of population density per hectare for this particular species of crab?

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.

Match the description of each organism to the appropriate category

If an organ has six haploid chromosomes,how many chromosomes are present. 6 12