The answer is plants. Plants are at the start of the food chain :)
ANSWER:
After the volcanic eruption,lava cools down,vegetation reappears and microscopic plants grow,then the macroscopic plants and animals come at that place,then gradually the whole system builds and ecosystem recovers.
EXPLANATION:
Biodiversity means diverse population of plants and animals. After the volcanic eruption,both plants and animals donot exist because of high temperature and not suitable environment. With the passage of the time, the lava cools down and vegetation stars reappearing. First of all lichens and microscopic plants and after that macroscopic plants and animals come at that place.Thus suitable conditions reappear and gradually the whole ecosystem recovers.
Speciation<span> is the term used to describe the formation of a new </span>species<span> due to </span>natural selection<span>.</span>
