Ascientist observes an enzyme polypeptide chain arrange in spiral turns that rise upaward and are held in place by hydrogen bonds. which level of structural arrangement is s/he looking for?

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.

Which of the following is one of the four conditions necessary for natural selection to occur in a population? fewer organisms are born than the habitat can support mutation does not occur organisms have identical characteristics variation is inherited

Which member of the following food chain will be least affected by ddt, a pesticide water pollutant, if bio-magnification is occurring? algae> zooplankton> crayfish> leopard frog> large mouth bass