HISTORY OF EUKARYOTES:
1. Evidence indicates that the first Eukaryotic cells first appeared on the earth approximately 2 billion years ago. Fossilized cells appear in shale sediments from China, Russia and Australia the date from 850-950 million years ago. 2. Biologists have discovered evidence to suggest that the eukaryotic cell evolved from prokaryotic organisms by a process of intracellular symbiosis. 3. Some of the organelles that distinguish eukaryotic cells originated from prokaryotic cells that became trapped inside them. 4. The structure of these first eukaryotic cells was so versatile that eukaryotic microorganisms soon spread out into available habitats and adopted greatly diverse styles of living. 5. The first primitive eukaryotes were probably single celled and independent, but over time some forms began to cluster in permanent groupings called colonies. With further evolution some of these cells within colonies became specialized or adapted to perform a particular function advantageous to the whole colony such as locomotion, feeding, or reproduction. 6. Multicellular organisms are composed of distinct groups of cells that cannot exist independently of the rest of the body. 7. The cell groupings of multicellular organisms that have a specific function are termed tissues and groups of tissues make up organs. 8. Protozoa , algae and fungi are unicellular
9. Plants, animals, mushrooms and seaweeds are multicellular.
FORM AND FUNCTION OF THE EUKARYOTIC CELL: EXTERNAL AND INTERNAL STRUCTURES:
A. Eukaryotic cells are complex and compartmentalized into individual organelles B. Major organelles and other structural features include: * Appendages (cilia and flagella)
* Cell wall
* Cytoplasmic or cell membrane
* Organelles (nucleus, nucleolus, endoplasmic reticulum, Golgi complex, mitochondria and chloroplasts) * Ribosomes