What was the amount of oxygen in earths early atmosphere

Which is one example of a phenotypic change that is not genetic

What type of plant is good for a bioassay and where can i buy it? i only have a month.

The serengeti plains are part of the african savanna ecosystem and are home to a variety of different species of plants and animals. the serengeti plains experience a seven-month period of seasonal drought each year, during which the ecosystem receives only four inches of rain and the availability of some resources becomes very scarce. which type of limiting factors does the seasonal drought in the serengeti plains affect?