The only vertebrates in which blood flows directly from respiratory organs to body tissues without first returning to the heart are the
a) amphibians
b) fishes
c) mammals
d) reptiles

Researchers randomly divide participants into groups. each group takes a different amount of omega-3 fatty acid supplements daily for a month. one group receives a placebo. the researchers measure the impact on cholesterol levels in the blood. what is the purpose of random assignment in this experiment? a, to produce treatment groups with similar characteristics b, to ensure that all people with high cholesterol have an equal chance of being selected for the study c, to increase the accuracy of the research results and prevent skewness in the data

The picture shows a fishing technique called trawling. how might trawling affect marine biodiversity

Match the description of each organism to the appropriate category