Question

photosynthesis oxygen re-evolution endosymbiosis,multicellularity are important events in history that set the stage for evolution of diverse organisms we are familiar with today please explain these events and how they set the stage for this diversity providing examples and details

Answer 1

Photosynthesis: Two and a half billion years ago, single-celled organisms called cyanobacteria harnessed sunlight to split water molecules, producing energy to power their cells and releasing oxygen into an atmosphere that had previously had none. These early environmental engineers are responsible for the life we see around us today, and much more besides.

Photosynthetic cyanobacteria reengineered the planet. Photosynthesis led to two more singularities—plants and animals appeared. The remaining singularities are mass extinctions as a result of something happening to the global environment, and photosynthesis likely caused one of those as well. Oxygen can be highly toxic because it's so reactive. It chews up your DNA, and it binds to the metal compounds that cells use to shuttle electrons around. Any microbes that couldn't cope with this new pollutant died off, or were forced to hide in oxygen-depleted environments.Atmospheric oxygen resulted from a change to a microbe's metabolism that evolved once, at a specific time in the earth's history.

Oxygen Revolution: he atmosphere on early Earth was very different than what we have today. It is thought that the first atmosphere of the Earth was made up of hydrogen and helium, much like the gaseous planets and the Sun. After millions of years of volcanic eruptions and other internal Earth processes, the second atmosphere emerged. This atmosphere was full of greenhouse gases like carbon dioxide, sulfur dioxide, and also contained other types of vapors and gases like water vapor and, to a lesser extent, ammonia and methane.This combination of gases was very inhospitable to most forms of life. While there are many theories, such as the Primordial Soup Theory, Hydrothermal Vent Theory, and the Panspermia Theory of how life began on Earth, it is certain that the first organisms to inhabit the Earth did not need oxygen, as there was no free oxygen in the atmosphere. Most scientists agree that the building blocks of life would not have been able to form if there had been oxygen in the atmosphere at that time.

Endosymbiosis:Endosymbiosis has played many roles in the evolution of life, but the two most profound effects of this process were undoubtedly the origins of mitochondria and plastids in eukaryotic cells. There are many parallels in how these organelles originated and how their subsequent evolution played out, for example, the reduction of the bacterial symbiont genome and the development of a protein-targeting system.There are also many differences, however, and one of the more striking is the ultimate fate of the organelle once established: where mitochondria were integrated into the host and the two were seemingly never again separated,, plastid evolution has seen many more twists, turns and dead ends (for other reviews that cover various aspects of this history.

Multicellularity:The evolution of multicellular life from simpler, unicellular microbes was a pivotal moment in the history of biology on Earth and has drastically reshaped the planet’s ecology. However, one mystery about multicellular organisms is why cells did not return back to single-celled life.“As an example, consider an ant colony where only the queen is laying eggs and the workers, who cannot reproduce, must sacrifice themselves for the colony,” Libby said. “What prevents the ant worker from leaving the colony and forming a new colony? Well, obviously the ant worker cannot reproduce, so it cannot start its own colony. But if it got a mutation that enabled it to do that, then this would be a real problem for the colony. This kind of struggle is prevalent in the evolution of multicellularity because the first multicellular organisms were only a mutation away from being strictly unicellular.”