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1 
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species that appear after bacteria, lichen, and moss during ecological succession 
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2 
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present at the start of primary succession 
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3 
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human activity that involves clearing trees and leads to secondary succession 
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4 
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change and replacement of organisms in an area over time 
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5 
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present at the start of secondary succession 
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9 
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human activity that involves growing crops and leads to secondary succession 
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11 
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number of years it takes for secondary succession to occur 
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13 
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organisms that sprout or release seeds when small fires are present 
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14 
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natural disaster caused by excessive rainfall and leads to secondary succession 
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16 
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causes primary succession by melting 
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17 
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causes secondary succession and eliminates brush that could lead to large forest fires 
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19 
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organism made up of a fungus and an algae that is a pioneer species 
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21 
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part of the community that changes in ecological succession 
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22 
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species that appear after grasses during ecological succession 
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24 
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another pioneer species like lichen 
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