a) withheld information from test subjects about their condition
Explanation:
The Tuskegee syphilis study which was carried between 1932-1972 in the Macon County, Alabama on the African-Americans infected from syphilis.
The U.S. Public Health Service started the study promising the infected persons that they will receive the benefits from the studies like a healthy meal, proper antibiotic medication and other benefits.
But the U.S Public Health Service failed to provide the services mainly the medication in which antibiotic penicillin which could treat the disease was not provided to the patient. As a result of this, syphilis continued in their generations also and people and about 100 subjects died.
They were told that they had bad blood which cannot be treated and thus in 1972, this raised a question over this issue related to ethics as to why the penicillin was not provided as well why the person was kept away from the reality.
The biologist is performing model-building type of investigation.
Explanation:
In the given scenario it is mentioned that the biologist is making a diorama of a plant cell. The diorama refers to the 3-D model of the specimen or object of the interest. The diorama of the specimen helps in gaining accurate knowledge of the concept as the subject is seen visually.
It also rules out much difference which arises about a concept through theoretical knowledge. Diorama is stable yet highly reliable evidence and it can also be altered according to the research and analysis.
Allopatric speciation is a type of speciation that is caused due to geographical isolation that results in the separation of the population of the same species that once inhabited the same geographical area.
Due to this geographic separation, the species become so isolated that no more gene flow occurs between the two species and therefore, with time new species get formed.
The various geographic changes that can contribute to the separation of the two species can be - formation of mountains, islands, water bodies, glaciers, etc.
The populations that get separated due to the geographic barriers are subjected to different selective pressures and hence, speciation occurs.
During Telophase 2, a nuclear envelope forms around each set of new chromosomes. In this stage, cytokinesis occurs, which is responsible for producing four daughter cells each with a haploid set of chromosomes. During the crossing-over phase some chromosomes are observed to have segments that have recombined with the original parent chromosomes. <span> When the phase is over, the two cells are now finally separated and their nuclear membranes are fully formed causing the meiosis cell division to be completed.</span>
