What benefits do nitrogen-fixing organisms provide in an ecosystem?
a. they release nitrogen compounds into the air
b. they convert nitrate into gaseous nitrogen
c. they turn atmospheric nitrogen into organic nitrogen compounds.
d. they eat organisms that contain large amounts of nitrogen compunds

In which part of the body is a ball-and-socket joint found?

During crossing-over, a. genetic material is exchanged between nonsister chromatids, resulting in new combinations of alleles. b. nonsister chromatids from each homologous chromosome of a tetrad are exchanged, resulting in new combinations of alleles. c. one homologous chromosome of a tetrad is exchanged with another tetrad, resulting in new combinations of alleles. d. sister chromatids from each homologous chromosome of a tetrad are exchanged, resulting in new combinations of alleles. e. genetic material is exchanged between sister chromatids, resulting in new combinations of alleles.

Which of the following is a responsibility of a scientist