Скачать или смотреть PROKARYOTES TO EUKARYOTES | Lec. No. 02 | EVOLUTION

The endosymbiont hypothesis proposes that eukaryotic cells evolved through a symbiotic relationship between different species of prokaryotes. Specifically, it suggests that organelles such as mitochondria and chloroplasts originated from free-living bacteria that were engulfed by ancestral eukaryotic cells. Over time, these engulfed bacteria formed mutualistic relationships, eventually becoming integrated into the host cell and contributing essential functions, such as energy production in the case of mitochondria. This hypothesis is widely accepted and supported by evidence such as similarities in genetic material and membrane structure between organelles and certain bacteria.

The membrane invagination hypothesis suggests that certain cellular organelles, particularly the endoplasmic reticulum (ER) and Golgi apparatus, originated through invagination or folding of the cell membrane. This hypothesis proposes that infoldings of the plasma membrane gave rise to the membranous structures within eukaryotic cells.

According to this hypothesis, as the membrane folded inwards, it created a series of compartments and vesicles, forming structures like the endoplasmic reticulum. Over time, these invaginations could have further developed into the more complex membranous organelles seen in eukaryotic cells.

While the endosymbiont hypothesis explains the origin of certain organelles, the membrane invagination hypothesis focuses on the development of membrane-bound compartments within a cell. Both hypotheses contribute to our understanding of the evolutionary processes that led to the complexity of eukaryotic cells.

The transition from unicellular to multicellular organisms is a pivotal step in the evolution of life. It involves the development of mechanisms that allow individual cells to coordinate and specialize, forming a multicellular organism.

This transition likely occurred through a series of incremental steps, possibly driven by selective advantages such as increased efficiency, division of labor, and adaptability. Some key factors in this transition may include cell adhesion, communication, and the evolution of mechanisms to regulate cell differentiation and development.

Over time, multicellular organisms evolved diverse forms and structures, leading to the complexity of life we observe today. This transition is a fundamental aspect of biological evolution and has given rise to the incredible diversity of multicellular life on Earth.
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