The cholera bacterium was first identified as a disease-causing agent through the groundbreaking work of Dr. John Snow in London in 1854. Dr. Snow mapped the incidence of disease and found that it clustered around a particular water pump. How did he make the causal connection between that pump and the disease

Dr. John Snow in London in 1854 discovered that the water where the cholera outbreak was prevalent was the same water used in other places. He came to a conclusion that it must be as a result of the pipes transporting the water. The pipes were found to have sewage surrounding them which made the water contaminated.

When the pipes were removed from the sewage surroundings the contamination, sickness and death rates reduced drastically.

the answer is yes, they are born/created, then they grow to their limit then produce offspring, then die.

the level of progesterone is low at the pre-ovulatory phase of the cycle but it gradually increases and the levels are high at the luteal phase. if pregnancy occurs, the level of progesterone will be high throughout the pregnancy.

if egg is fertilized and the mother gets pregnant, progesterone starts preparing the uterus for the implantation. it starts building up the lining of uterus and make it hostile of the period of pregnancy.