How many mass extinctions have there been in the last 500 million years?

Which of the following is not a benefit of green revolution? a) new crop varieties b) increased crop yields c) cost effective d) new crops may require larger amonts of water than the previous ones.

Sydney drew a flow chart to illustrate the nitrogen cycle.which labels best complete the flow chart? x: producers undergo photosynthesis.y: nitrogen compounds are released into the air.x: nitrogen compounds are released into the air.y: producers undergo photosynthesis.x: free nitrogen is in the atmosphere.y: producers absorb nitrogen compounds through their roots.x: producers absorb nitrogen compounds through their roots.y: free nitrogen is in the atmosphere.

What are some aquatic organisms that live in cold water temperatures?