Alguien me puede ayudar porfa? porque la tierra siempre cambia?

It is not known why earth changes always. However, it is a truth that Earth changes each day. The details are given in the explanation. Also, anything that exists is subject to change, and this is a universal truth, and that's why earth also changes sometimes through climatic change, and sometimes with the time.

Explanation:

The mother earth has seen all colors of life, but God keeps making new colors daily. There was once ice age, and then came Ice-free age. And even when we didn't exist, forests used to catch the fire through lightening. The volcanoes used to erupt during those days as well. And now the refrigerators. air conditioners. industries and all are depleting ozone layer and a lot out of these are causing an increase in temperature due to CO2 effect in the atmosphere. Arrhenius once studied the rate of rising temperature in the earth's atmosphere and proved in around 1896 that the temperature of the Earth is increasing, and with further studies, we are now up with the most accurate statistics related to earth's climate. If we do not take the initiatives then mother Earth might soon not be as good as it is used to be for living. Hence, we have to take care of the climatic condition of mother Earth and discard everything harmful.

this null effect is caused by a weak manipulation and ineffective internal validity. in a scientific study, as the one dr. morimoto is trying to perfom, internal validity refers to the confidence placed in the cause-effect relationship and to how well an experiment is done and able to eliminate confounding variables.        

this statement is true.

forests are public goods, available for everybody. when usage of such a good becomes interesting for consumers and its usage increases, there can be a risk of overexploitation. it is a non rival good therefore, if one person consumes the good it does not reduce the availability for subsequent consumers.

these caracteristics require the establishment of measures in order to prevent the destruction of a commonly owned space, for example, to restrict the amount of people that have access to the same time.