what makes this astronomical object the only place to have life?
Chemical reactions led to the first self-replicating molecules
Earth
Chemical reactions led to the first self-replicating molecules about four billion years ago
what happens when a keystone species is removed from an ecosystem apex The ecosystem would be dramatically different or cease to exist altogether. can you explain the meaning of this category? A keystone species is a species which has a disproportionately large effect on its natural environment relative to its abundance what animals fall under this category? wolf who introduced this system? Robert T. Paine what is the meaning of the environment mentioned above? It encompasses all living and non-living things occurring naturally. where is this environment applicable? Earth or some parts of Earth what is this place? Earth is the third planet from the Sun and the only astronomical object known to harbor life. how was it formed? A solar nebula partitions a volume out of a molecular cloud by gravitational collapse, which begins to spin and flatten into a circumstellar disk, and then the planets grow out of that disk with the Sun
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Earth [SEP] Origin of life and evolution
Chemical reactions led to the first self-replicating molecules about four billion years ago. A half billion years later, the last common ancestor of all current life arose. The evolution of photosynthesis allowed the Sun's energy to be harvested directly by life forms. The resultant molecular oxygen () accumulated in the atmosphere and due to interaction with ultraviolet solar radiation, formed a protective ozone layer () in the upper atmosphere. The incorporation of smaller cells within larger ones resulted in the development of complex cells called eukaryotes. True multicellular organisms formed as cells within colonies became increasingly specialized. Aided by the absorption of harmful ultraviolet radiation by the ozone layer, life colonized Earth's surface.