Allow materials to be exchanged between the blood and tissues, carry blood towards the heart, and carry blood away from the heart.

Capillaries; veins; arteries

Capillaries allow materials to be exchanged between the blood and tissues, veins carry blood towards the heart, and arteries carry blood away from the heart.

Capillaries are small blood vessels through which molecules such as oxygen and glucose enter the cells.  

Veins are tubes or blood vessels that transport blood toward the heart. Veins mostly transport deoxygenated blood towards the heart except the pulmonary and umbilical veins, which transports oxygenated blood toward heart.

Arteries are blood vessels that transport blood away from the heart to other parts of the body. Arteries have elastic walls and they are stronger and thicker than veins.

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explanation:

plate tectonics and volcanic euptions

over time, plate tectonic processes cause continents to move to different positions on the globe.

for example, britain was near to the equator 300 million years ago, and therefore was hotter than it is today. for further details look at our climate through time poster or online map.

the movement of the plates also causes volcanoes and mountains to form and these too can contribute to a change in climate.

mountain ranges formed by plate tectonics. large mountain chains can influence the circulation of air around the globe, and consequently influence the climate.   warm air might be deflected somewhere cooler by the mountains.