succession

• Succession is the changes in species over time.
• In primary succession, bare rock is colonised by pioneer species - moss and lichens. 
• Pioneer species reproduce asexually, wind disperses their seeds, they germinate rapidly, are fast growing, photosynthesise and tolerate low levels of water. This means that they do not rely on animals for reproduction and food. They can regrow rapidly after adverse weather conditions and can survive in harsh environments. 
• Pioneer species weather the rock to make sand and soil for rooted plants. When the pioneer species die they are decomposed and contribute nutrients for plants. The change in the habitat make it less hostile. 
• Lichens give way for mosses and then ferns outcompete mosses. 
• Over time the abiotic conditions become less harsh as succession continues, providing a greater number of niches and habitats. This increases biodiversity with more complex food webs and increased biomass. Eventually a climax community is reached where no more changes happen. 
• Animals undergo a similar succession process due to food and habitat availability. 
• Secondary succession happens after land is cleared (fire), its more rapid than primary succession and some seeds/spores are already present.