The IUCN red list classifies the organism as endangered , extinct, threatened and vulnerable organism. The organism are classified on the basis of their number and presence on the particular area.
Extinct species is the species that are no longer present on the earth. The extinct species has been eliminated due to the unfavorable environmental condition and due to human activities. No single organism is present of the extinct species.
The term "photoperiodism" was coined to describe a plant's ability to flower in response to changes in the photoperiod: the relative lengths of day and night. Because flowers produce seeds, flowering is crucially important for the plant to complete its life cycle.
