Vascular tissue
Of course plants don't have hearts, but they do have vessels which transport water, minerals, and nutrients through the plant. These vessels are the vascular tissue.
The anterior, middle, and posterior.
Oxygen is needed by aerobic organisms for cellular respiration process. Oxygen happens when the muscles are working faster than energy can be produced. Energy is still produced but anaerobic process is done to cope up. The signs of oxygen debt are panting and muscle fatigue.
Light speed in water is 2.25 times 10^5 m/s so the index of refraction is higher than the index of refraction of light in a vacuum which is 1.0. (speed in vacuum for light is 300,000 km/s)
Index of refraction of light in water is 3.0 time 10^5 m/s divided by 2.25 times 10^5 m/s = 1.33.
Hope this is what you wanted.