Look back at the reaction for photosynthesis. trees that are cut down can no longer photosynthesize.

As we can see from the photosynthesis equation, for a plant to be able to perform photosynthesis it will need CO2, water and slar energy. CO2 and solar energy can only be absorbed by the leaves of the plant. For this reason, if a plant is cut and its entire crown is uprooted, leaving only the trunk, it will not be able to perform photosynthesis, since it will not be able to absorb CO2 and solar energy. Consequently, the tree will not be able to release oxygen into the atmosphere.

If all the trees in the world were cut down, we would experience an increase in the concentration of CO2 in the atmosphere and a decrease in the concentration of O2, which would be very harmful to our lives.

the unequal cytoplasmic division that  results  in  one egg  and three polar bodies ensures that a fertilized  egg has  ample nutrients  forits journey  to  the uterus.