What defines a species of organisms? what makes them a species?

there are so many examples for that in different areas, like biology experiment carried out in our lab recently.

here's one link:

he movement of air through earth's or any planet's atmosphere is called wind, and the main cause of earth's winds is uneven heating by the sun. this uneven heating causes changes of atmospheric pressure, and winds blow from regions with high pressure to those with low pressure.

i hope this : )