When the adults have reach a certain degree of weakness, the process of binary f...

This Biology question is asking about what happens when adult organisms become too weak to undergo binary fission. Binary fission is a type of asexual reproduction where an organism divides into two identical daughter cells. The question wants to know which organism replaces binary fission with conjugation when the adults are too weak.

Out of the options given, the correct answer is Paramecium. Paramecium is a type of unicellular organism that reproduces asexually through binary fission. However, when the organism becomes weakened, it undergoes a sexual process called conjugation. Conjugation is the process in which two Paramecium cells come together and exchange genetic material, resulting in genetic diversity in the offspring.

Euglena is another unicellular organism that reproduces asexually through binary fission. However, Euglena does not undergo conjugation when the adults become weak. Amoeba is also a unicellular organism that reproduces asexually through binary fission, but it does not undergo conjugation either. Plasmodium, on the other hand, is a unicellular organism that causes malaria and reproduces sexually through sporogony in the mosquito host.

In summary, the correct answer to this Biology question is Paramecium. When adult Paramecium organisms become too weak to undergo binary fission, they undergo conjugation instead, which is a sexual process that results in genetic diversity in the offspring. The other options given, Euglena, Amoeba, and Plasmodium, do not undergo conjugation when the adults become weak.