Answer:
I'm pretty sure the answer is B! Hope this helps:]
Answer:
unicellular life first
Explanation:
it arose billions of years ago while multicellular life forms around at least 600 million years ago
The unit of measurement in an ecological footprint is the global hectare.
Answer:Wildebeest are considered keystone species because their presence has myriad effects on the ecosystem, unlike those of any other species. Wildebeest are the "lawnmowers" of the Serengeti grassland. They keep grass short which in turn reduces the frequency of fires.
Soil, water and food are all nonliving reservoirs of infection
