In the Ascaris lumbricoides life cycle, after eggs are ingested, the next stage in the life cycle that must occur before a mature adult can live in the host's intestine is called the:

Liver-lung migration

Explanation:

Ascaris lumbricoides is also known as round worm and humans get transmitted through contaminated food and water.

When they are ingested, the hatched larvae then penetrate into the intestinal mucosa and are carried to the liver through the portal venules and are then moved to the lungs . When they are in the lungs they rupture which results in them being coughed up and swallowed. After which they mature, mate and deposit eggs which are excreted and the cycle goes on when humans ingest food contaminated with the eggs.

They cause abdominal pain, nausea and anemia and are treated through drugs such as mebendazole.

not necessarily. higher fitness requires the organism to be reproductive successful. for example, an organism at age 10 with 15 offspring is much more fit than an organism at age 15 with only 5 offspring.