What plagued the slums of urban communities in the 19th century? 1. overcrowding
2. crime
3. disease
4. all the above

As our current atmosphere formed, the concentrations of various atmospheric gases fluctuated. match each gas with the explanation that best describes how its proportion changed during the evolution of the atmosphere.

According to the federal regulations, which of the following studies meets the definition of research with human subjects? a. a researcher uses the customs office’s passenger lists for ships bringing immigrants to the us between 1820-1845 to track the numbers of immigrants from certain ethnic groups.b. a researcher conducts a linguistic study of comments posted on a local public blog.c. a developmental psychologist videotapes interactions between groups of toddlers and their care givers to determine which intervention methods most effectively manage aggression.d. a researcher asks the director of a local free clinic about the number of patients in the last two years with newly diagnosed hiv/aids.

Which statement below accurately describes the carrying capacity of any ecosystem? a. it is not affected by any abiotic or biotic resources. b. it does not affect the species of an ecosystem. c. it is completely dependent upon the food supply. d. it is affected by both abiotic and biotic resources