1.Serial endosymbiosis is the most supported theory on how the firsteukaryotic cells evolved from prokaryotic cells. The figure depicts theevolution of eukaryotic cells which include links to prokaryotic cellsfrom early in the history of life.Identify the cellular structures involved in the connection of eukaryoticand prokaryotic cells. Describe the characteristics of the cellularstructures that supports the evolutionary connection.а.

They consist of eubacteria and archaebacteria. Eukaryotes have complex internal organisation and differ from the prokaryotes. They have membrane bound nucleus and other internal membranous organelles. The cellular structures connecting prokaryotes and eukaryotes are mitochondria and chloroplasts. The origin of these organelles in the eukaryotes is explained by the serial endosymbiosis theory. It was promoted by Lynn Margulis. It states that eukaryotic cells evolved when free living prokaryotes became incorporated into larger prokaryotic cells which eventually gave rise to the mitochondria and the chloroplast. It is believed that the phagocytosis of a bacteria by another prokaryotic cell resulted in the development of the eukaryotic cell. The phagocytosed bacteria obtain nutrients from the host cell. They continued to reproduce independently with subsequent generations retaining the endosymbiont. They lost the ability to function without each other. These bacteria is what formed the mitochondria of the present day eukaryotic cell. Eukaryotic plants and photosynthetic protists evolved by ingestion of the photosynthetic bacteria by prokaryotes or eukaryotes. These are the chloroplasts. The characteristics of chloroplasts are: They are round/oval shaped organelles. They are double membraned organelles. They have 70S ribosomes for protein synthesis. It consists of a fluid filled region called the stroma which has stacked sacs called grana connected by stroma lamellae. Involved in the production and storage of energy. They play a vital role in photosynthesis. They contain their own DNA (deoxyribonucleic acid). The characteristics of mitochondria are: Mitochondria are self replicating and have two membranes. They have their own DNA which is similar to bacterial DNA. They have ribosomes, enzymes and transport systems which are similar to those in bacteria. They produce energy in the form of ATP (adenosine triphosphate) They can be spherical/cylindrical or branched.