Answer:
Milankovitch cycle
Explanation:
Milankovitch cycle was discovered by Mr. Milutin Milankovitch, who described that there occur changes in the earth's orbit in 3 cycles which are distinctly of different lengths.
There occurs changes in the shape of the earth's elliptical orbit from minimum to maximum and comes back to the minimum, which takes near about 100,000 years.
The tilt of the earth is about 23.5°, which changes from about 21.5° to 24.5° and gain goes back about 41,000 years approximately.
The imaginary internal axis of the earth rotates unsteadily with a period of nearly 23,000 years.
Thus, these changes occurring in the earth's elliptical shaped orbit takes place every 100,000 years and is a cycle of the Milankovitch cycle.
The spinal cord is the answer
To package and ship things through the cell
A single variable.
In an experiment we are trying to figure out how one thing (independent) effects another thing (dependent) so we want to keep everything constant. We want that experiment to be controlled so nothing else is effecting our dependent variable. That way we can be 100% sure that any change to our dependent is due to our independent variable. Hope that makes sense