Cyanobacteria, also known as blue-green algae, are found in vast quantities in fresh and salt water. Cyanobacteria are able to conduct photosynthesis. By utilising energy from the sun, they produce carbohydrates from water and carbon dioxide. As a byproduct, they produce oxygen. So cyanobacteria provided oxygen to the atmosphere that allowed other lifeforms to develop.
The correct statements are I, III and IV.
An angiosperm refers to a plant, which exhibits flowers and generates seeds enveloped within a carpel. The angiosperms include a large group of herbaceous plants, grasses, shrubs, and the majority of trees. While gymnosperms refer to the plants that exhibit seeds but not safeguarded by any kind of fruit or ovary. It includes the cycads, gingko, and conifers.
Both the angiosperm (sunflower) and gymnosperm (gingko) are seed-bearing plants. However, the seeds of a sunflower are safeguarded by a flower or fruit, while for the gingko, there is no mechanism like that, i.e, there is not any kind of protection. Additionally, sunflower exhibit phenomenon of double fertilization, which is not witnessed in the case of gingko.
