Respuesta :
Answer:
Here are the Brief summary of the evolution :
- After earth formed, Volcanoes emtted gas and meteroite brought ice
- Earth cooled and the atmosphere thicken, meanwhile the ocean is also formed
- Cyanobacteria increased the amount of O2
- O2 released into atmosphere and Eukaryotes evolved
hope this helps
Answer:
It can be summarized by first explaining the Origin of universe, followed by evolution of first life form which includes chemical evolution followed by biological evolution.
Explanation:
Origin of universe: Big bang theory explains the origin of universe around 20 bya. It states that a huge explosion called big bang took place in the space after which universe expanded in volume and the temperature of the space came down.
Billions of galaxies were formed, of which milky way galaxy was formed around 4.5 bya.
From the molten mass of volcanoes several gases were releases into the surroundings slowly forming the atmosphere but it was reducing in nature unlike today's oxidising atmosphere.
Life appeared 500 million years after the formation of earth.
Chemical evolution: It was explained by Oparin-Haldane hypothesis.
Free atoms -> simple inorganic molecules -> simple organic molecules -> complex organic molecules (DNA, RNA, protein) -> first life form.
Origin of heterotrophs: First living organisms were anaerobic and heterotrophs. When the supply of existing organic molecules was exhausted, autotrophs were evolved, capable of producing their ow organic molecules by chemo-synthesis or photosynthesis.
At later stages, oxygen releasing photosynthetic organisms developed like cyanobacteria.
Formation of eukaryotic cell: The prokaryotes gradually developed true nucleus and other specialzed organells. Thus free living eukaryotic organism originated in the ancient ocean around 1.5 bya.
