Wildlife can be scarce in many large, densely populated cities. A few plants and animals can be found in these areas. For example, rats, mice, pigeons, cockroaches, and other insects are common in cities. Trees can grow by sidewalks or in local parks. Some cities even have small populations of coyotes within city limits.

Do you think these cities meet the definition of an ecosystem? Explain your reasoning.

What are the seven economic and social goals?

What sentence best supports the statement that hormones are involved in the regulation of homeostasis? a. the hormone erythropoeitin increases the production of red blood cells when oxygen levels are low. b. the hormone oxytocin promotes labor contractions of the uterus during childbirth. c. the hormone melatonin induces sleep and its production is slowed by exposure to light. d. the hormone cortisol suppresses the immune system and is produced when the body is under stress.

Compare the shapes of the bones of the human skull with the shapes of the bones of the human leg. how do the shapes differ? why are the shapes important?