אבולוציה איקריוטית

The first eukaryotic cell originated from a primitive prokaryotic cell, which had its genetic material freely bundled in the cytoplasm.

These cells were surrounded by a plasma membrane but lacked any membrane-bound organelles inside.

As the cell evolved, the plasma membrane invaginated and pinched off, giving rise to membrane-enclosed intracellular bodies or organelles, such as the endoplasmic reticulum or ER.

The ER later organized itself to form the nuclear envelope around the DNA cluster.

Additionally, the ER budded off vesicular clusters that fused together to form the Golgi apparatus.

According to the Endosymbiont theory, this ancestral cell then engulfed a small, aerobic prokaryote.

This bacteria escaped digestion and enabled the host cell to use oxygen and generate energy. It eventually evolved into mitochondria - the powerhouse of the existing eukaryotic cells.

In due course, some of these ancestral eukaryotic cells acquired additional endosymbionts like cyanobacterium, a group of bacteria capable of photosynthesis.

These endosymbionts later evolved into chloroplasts, the site of photosynthesis in green algae and plants.