Once implantation has occurred, part of the blastocyst develops into the placenta. The transfer of antibodies from mother to foetus at the placenta in several different species can be seen in the graph below.
Contrast the changes in antibody concentration in the foetuses of humans and rats.
The graph below shows levels of a synthetic oestrogen called ethinylestradiol at different sampling locations along a river. Note that a treatment plant treats sewage wastewater before releasing treated water back into a river.
Calculate the percentage increase in ethinylestradiol concentration between 1 km upstream of the treatment plant and the point of discharge from the treatment plant.
One study investigated the effect of ethinylestradiol on reproduction in one species of fish. The researchers exposed fish in separate mesocosms to different concentrations of ethinylestradiol.
Explain why the scientists chose to carry out their investigation in mesocosms.
The scientists measured the effect of changing ethinylestradiol levels on egg production and embryo formation in fish populations. Their results are shown in the graph below. Note that the symbol * denotes a result that is significantly different from the control (0 ng L-1).
A student read these results and concluded that ethinylestradiol was harmful to reproduction in fish.
Use all the information provided throughout Q4 to evaluate the student’s conclusion.
