Cyanobacteria play an important role in the evolution of the earth and biosphere. Cyanobacteria play a role in the oxygenation of the atmosphere and oceans that began since the great oxidation event. These living things are the main producers in the ocean in the past and present and are the ancestors of Chloroplasts. The morphology commonly used is still difficult to read for microfossil interpretation which makes the identification of cyanobacteria in the early fossil record still ambiguous. This study was conducted to review classical and new cyanobacterial biosignatures. In addition, this study will also analyze the fossil record of cyanobacteria mentioned earlier and the challenges of molecular approaches to modern cyanobacteria. The suggestions we provide are new calibration points for molecular clocks and strategies to increase insight into the timing and patterns of cyanobacteria evolution and oxygenic photosynthesis.

Open seed plants or Gymnosperms and closed seed plants or Angiosperms are two subdivisions of seed plants. Seed plants reproduction tool consists of strobilus or flowers. The reproductive tool of closed seed plants is a flower that grows from a bud equipped with petals, stamens, and pistils. The purpose of this study was to observe the reproductive structure of seed plants. This research was conducted at Instructional Laboratory 1, UIN Sunan Gunung Djati Bandung. The method used was direct observation in the laboratory by analyzing the internal structure of reproductive organs. The results Angiosperms such as bungur flowers (Lagerstroemia speciosa) have complete reproductive organs and produce seeds in closed ovaries, while gymnosperms such as pine (Pinus merkusii) have strobilus as reproductive organs and open seeds. Although gymnosperms and angiosperms share many similarities in basic adaptations and functions, they differ significantly in internal structure and reproductive mechanisms.