The population is exceeding what the Earth's resources can supply we hardly have enough food for certain countries and also to places like China who do not believe in global warming or anything of that sort pollute the air consistently which is why they've been in a fog for the past few weeks I believe and not only that if it continues we will use up all of our natural resources the more people the more resources
Mental wise would go down many aspects even the thought of dieing soon and emotional impact of loved ones and worrieness.
The horse and donkey, though closely related by sharing a common ancestor, are different species. They have different number of chromosomes hence pairing of homologous chromosomes during fusion of gametes becomes complicated. The mule will have an extra chromosome from the horse hence will have abnormalities such as sterility. A Mule is unable to reproduce due to this same phenomenon. Homologous chromosomes are not well paired for meiosis I.