The cell membrane functions as a selective barrier. We call these kind of membranes as differentially permeable or semi permeable membrane. It can decide what substances can pass in and out. Therefore it can surround the cytoplasm (which is the inside of a cell) to separate the cell's content from the surroundings.
A) genetic drift
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Answer:
Explanation:
The molecular and cellular mechanisms and processes that explain muscle contraction in striated muscle occur in the myofibril sarcomere. Their understanding depends on the organization's understanding of the structure of the sarcomere. In an imaginary experiment we first assemble an ideal sarcomere.
Remember that the myofibril is a set of cylindrical compartments that are located next to each other, constituting an elongated cylinder. Each of these cylinders is a sarcomere and borders its neighbor on a line or band called, line or band z.
On each side of the z line, thin cylindrical filaments that are actin filaments are inserted. Each actin filament is formed by a double strand of actin molecules that are rolled over each other. In this organization, actin is called actin F.
Answer:
there are tree hypothesis
Explanation:
There are several mechanisms by which multicellularity could have evolved:
1. A group of cells were added in a slug-shaped mass called grex, which was moved as a multicellular unit, as the Myxomycota do.
2. The primitive cell suffered an incomplete division of the cell nucleus generating a cell with multiple nuclei or syncytium. Next, membranes formed around each nucleus and the space was occupied by organelles. This resulted in a group of cells connected in an organism, an observable mechanism in Drosophila.
3. Daughter cells did not separate after cell division, resulting in a conglomeration of identical cells in an organism, which later developed specialized functions. This is observed in embryos of plants, animals and colonial cyanoflagellates.
Should read more about the topic here, google it:
<em>Multicellular development in a choanoflagellate; Stephen R. Fairclough, Mark J. Dayel and Nicole King
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<em>In a Single-Cell Predator, Clues to the Animal Kingdom’s Birth</em>