Why fresh water protozoa bear contractile vacuole?

Which codon is the code for the amino acid histidine (his)?

Apair of fruit flies reproduces and has 1,000 offspring. all 1,000 of the offspring have the alleles gg. what is the most likely combination of alleles for each parent

Which statements best describe the differences or similarities between a comparative investigation and an experimental investigation? check all that apply. experimental investigations are best for showing cause-and-effect relationships, while comparative investigations do not necessarily show this type of relationship. comparative investigations are often impractical and unrealistic, while experimental investigations are the most practical and realistic kinds of investigations. comparative investigations allow for the use of a wide range of variables but do not have a control group, while experimental investigations involve variables that can be controlled. both experimental investigations and comparative investigations are designed to answer scientific questions. both experimental investigations and comparative investigations focus on making observations rather than collecting new data.