What effect do keystone species have on an ecosystem?
A. They destroy habitats.
B. They maintain biodiversity.
C. They cause primary disturbances.
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D. They make weak species extinct.

What can be said about farmers in highly developed countries? a) they have little or no negative impact on the environment. b) they practice subsistence agriculture. c) they are able to incorporate polyculture into their farming practices. d) they utilize organic farming techniques on a regular basis. e) they rely on large amounts of energy from fossil fuels.

Which of the following is an effect of the uneven heating of the earth by the sun? a sea breeze a land breeze a convection current all of the above

Select the word from the list that best fits the definition a system made of 25 satellites