Darwins's theory of natural selection is an evidence of evolution by acquiring characters that make survival of an organism feasible in a typical environment.
Fossils records are used to support this theory, by figuring out the common ancestry of different species and different traits that have evolved in them with time.
Embryology is also used as an evidence which shows common origin of the organisms. Other evidences are geographic distributions and homologous structures of the living organisms.
Answer:
Hey, I answered your last question(the same one), so you should check the last question you posted.
Planarias are flat worms that live freely in freshwater and sometimes in teh logs, soil, plants, or other dump or humid areas. They are from the class of Turbellarians. They have a very good ability in regeneration. They are acoelomerate which means that their body is very solid without any hollows.
They excrete unwanted objects from their body using their excretory system which is consists of series of tubes with length similar to their body length. The flame cells remove excess water through the use of the cilia and pass them to the ducts. At the end of the duct, there exist pores called the nephridiapores.
There are three types of hormonal release control (increase or decrease production), which is stimulated by
1. specific molecules, minerals or particular nutrients ( chemical regulation)
2. other hormones (hormonal regulation)
3. input from nervous system. (neural regulation)
If the inhibition is caused by a different hormone, it would be considered hormonal regulation. In the given example, the hormone is produced in the target organ.
However, if the inhibition is due to the accumulation of the hormone itself, then it is an example of a <em>negative feedback</em>.
