With shorter necks, giraffe ancestors could not reach food-containing branches on tall trees. This resulted in the directional selection of giraffes with longer necks.
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Why is choosing a direction necessary? </h3>
It nearly appears obvious that the giraffe's long neck developed as a result of a lack of food in the lower branches of trees. The giraffe has a significant advantage because it is taller than any other mammal and can feed where few others can.
When compared to modern giraffes, the giraffe's ancient predecessors had a shorter neck. The plants that were lying at a higher level were inaccessible to them. Giraffe phenotypes have changed in various ways, and now have long necks to reach vegetation that is higher up. The extreme form is chosen above other features in directional selection. It was decided to choose the long-necked giraffe over the short-necked.
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Answer:
Movement of free water molecules from an area of low concentration to an area of higher concentration
Explanation:
I don't really know but I pick b.have always been vestigial.
Answer:
The correct answer is: a. True.
Explanation:
There are several membrane transport systems responsible for the passage of ions like Na+ and K+.
Cell membranes are semipermeable, which means they can regulate which molecules may and cannot flow through them. Some molecules may simply drift in and out of a cell (this is called simple diffusion), while others require specific structures to enter and exit (this type of diffusion is called facilitated diffusion), and still, others require an energy boost to pass the cell membrane (this is known as active transport).
Both simple diffusion and facilitated diffusion are types of passive transport: they happen without the energy boost that ATP gives, unlike active transport.
In passive transport, molecules follow their chemical gradients and travel through the most concentrated compartment to the less concentrated one to equal the concentrations. In active transport, on the other hand, the cell makes an effort to enter or exit ions against their chemical gradients and this is done particularly to maintain said gradients (they are required for the correct functioning of the cell).
Sodium and Potassium are two of the most important ions when it comes to maintaining these gradients: sodium is very concentrated in the outside of the cells (the extracellular compartment), while potassium is highly concentrated in the intracellular compartment. These differences in concentrations are maintained thanks to the Na+/K+ pump, a form of active transport. Apart from the Na+/K+ pump, these ions go through the membrane through passive transport as well, without requiring energy.
