Regeneration in planarians depends on the presence of stem cells called neoblasts. These cells are distributed throughout the body and, when part of the worm has been amputated, they are activated to reform the tissues that have been removed.
Answer:
A scientific theory is an explanation of an aspect of the natural world that can be repeatedly tested and verified in accordance with the scientific method
Explanation:
People with two copies of the sickle cell gene have the disease. People who carry only one copy of the sickle cell gene do not have the disease, but may pass the gene on to their children. Abnormal hemoglobin, called hemoglobin S, causes sickle cell disease (SCD). The problem in hemoglobin S is caused by a small defect in the gene that directs the production of the beta globin part of hemoglobin. This small defect in the beta globin gene causes a problem in the beta globin part of hemoglobin, changing the way that hemoglobin works.
The common ancestor.
A phylogenetic tree shows how a species
originates (by evolution) other species. It’s very similar a genealogic tree. If
you want your family tree, you should write down your name and the names of all
your brothers and sisters and then draw a line from all those names to the
names of your parents, and then draw a line from the name of your father to the
names of your gramma and grampa, and then do the same with the names of your aunts
and uncles. If you repeat the process with many, many generations, you will
have the common ancestor to all of those relatives. You can do the same with
species: for example, humans are supposed to have a common ancestor with
monkeys, so their lines will end together in the same point in the graph. Then
you have to draw a line from that point to another point that will be shared
with other mammalians, then Mammalians share a point with other vertebrates,
and so on… If you keep on going, you will get to LUCA someday.
