What allows substances to pass back and forth between the placenta and the embryo?

In 2015, about ten percent of total u.s. energy consumption was from renewable energy sources. renewable energy plays an important role in reducing greenhouse gas emissions. when renewable energy sources are used, the demand for fossil fuels is reduced. sanjay and his family want to cut back on their use of non-renewable resources at home. they are thinking of an alternate way to heat their home without adding more greenhouse gases or pollutants to the environment. which renewable resource would not fit into their plan? a) solar power b) burning wood c) constructing a wind turbine eliminate d) generating hydroelectric power

How would you describe the the organisms in the second row of model 1 that are connected to the parents by a line

There are only about 250,000 known fossil species. true or false