Predators rarely kill and eat all available prey because:
predator and prey species often occupy the same trophic level in an ecosystem
prey species often lack protective mechanisms to deter being eaten
many predator and prey species have a commensalistic relationship
predator species often will switch its prey as one prey species becomes less abundant

As a small change in a person's dna can cause a genetic disorder

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.

7. describe two strategies that parents can use to cope with stress. 8. describe the three types of childcare available to families. 9. what can parents do to be more involved in their children's education at home and at school? 10. which factors should a parent consider when choosing a childcare option?