50% probability that a human sperm cell will carry an X chromosome
Option (III) .Cephalization, the clustering of neurons and interneurons in the anterior part of the animal, is apparent in <u>Planaria.</u>
What is planaria?
- Planaria is a genus of planarians in the family Planariidae.
- When an individual is cut into pieces, each piece has the ability to regenerate into a fully formed individual.
- Currently the genus Planaria is defined as freshwater triclads with oviducts that unite to form a common oviduct without embracing the bursa copulatrix and with an adenodactyl present in the male atrium.
- The testes occur along the whole body.
- Planaria originally have habitats in dark, murky water which results in such sensitivity .
- They are also sensitive to other stimuli such as chemical gradients, vibration, magnetic and electric fields .
- Their central nervous system includes the anterior (head, brain and eyes) and middle (abdominal trunk and pharynx).
To know more about planaria, refer:
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Nitrogen fixation is the process where atmospheric nitrogen is converted by bacteria into biologically usable forms.
plant can not take nitrogen directly from the leaves.
Answer:
He examined covered and uncovered meat to determine that maggots came from eggs.
Explanation:
Prior to Redi's experiment and other supporting experiments, it was formerly believed that life could emanate from non-living things, for example, the generation of maggots from rotting meat.
In 1668, a scientist called Francesco Redi disproved the idea of spontaneous generation. He did this when he experimented that the maggots from meats are only as a result of eggs laid by flies when they perched on the meat.
He placed the meat in two jars; an uncovered jar and another in a covered jar with a cloth, after several days, the uncovered jar had maggots on the meat, while the covered jar had no maggot on the meat, but on the cloth. With this experiment, he was able to demonstrate that the maggot arose from the eggs of the flies, not the meat itself which is nonliving and hence, disproved the idea of spontaneous generation.
