Botany strengthen the secondary cell walls of xylem tracheids and vessels to keep them from collapsing when a plant sucks water through them under water stress. Lignin is also used in other cell types like sclerenchyma fibres that provide structural support for a plant and is a major constituent of wood. Sporopollenin is a chemically resistant polymer found in the outer cell walls of spores and pollen of land plants responsible for the survival of early land plant spores and the pollen of seed plants in the fossil record. It is widely regarded as a marker for the start of land
Development of Spore survive in a strange world, with elements of "Nintendogs". The mobile phone version of "Spore", called "Spore Origins", was based on the tide pool phase, in which players try to survive as a multicellular organism, with gameplay similar to "flOw". On March 6, 2008, an iPhone version was demonstrated at Apple's iPhone SDK press event, though there was no commitment to ship such a product given at that event. The iPhone-Spore demo made use of the device's touch capabilities and 3-axis accelerometer. Electronic Arts confirmed on March 31, 2008 that "Spore" would be receiving post-release expansion packs. Only one expansion