Eukaryotik

Eukariotik, or eukaryotik, describes organisms whose cells contain a true nucleus enclosed by a membrane and a complex endomembrane system. The term comes from the Greek eu- meaning true and karyon meaning nucleus. Eukaryotik cells are distinguished from prokariotik cells by their compartmentalized organization, which includes membrane-bound organelles such as mitochondria and, in plants and algae, chloroplasts, as well as an extensive cytoskeleton.

Key features of eukaryotik cells include a nuclear envelope with nuclear pores, linear chromosomes housed in the nucleus, and ribosomes of about 80S in the cytoplasm (with mitochondria and chloroplasts possessing their own 70S ribosomes). They routinely implement an internal transport network via the endoplasmic reticulum and the Golgi apparatus, forming an elaborate endomembrane system. The cytoskeleton provides structure, mobility, and intracellular transport. Many eukaryotes are multicellular and exhibit differentiated tissues, though unicellular eukaryotes (such as yeasts and many protists) also exist.

Eukariotik life is diverse, encompassing four major kingdom-level groups: Animals, Plants, Fungi, and Protists. Reproduction commonly involves mitotic cell division, and many lineages also undergo meiosis and sexual reproduction. This domain exhibits a wide range of metabolisms and habitats, from moist terrestrial ecosystems to aquatic environments.

Origin and evolution are explained in part by endosymbiotic theory: mitochondria are derived from an ancestral proteobacterium, and chloroplasts (in photosynthetic lineages) from cyanobacteria, demonstrated by organellar DNA, double membranes, and ribosomal size consistent with their bacterial ancestry.