Rebekah is studying lichens growing on a cooled lava field. what is rebekah most likely researching? a )secondary succession b) climax communities c) pioneer species d) disturbances

The correct answer is C: Pioneer species.  

Explanation:

Succession refers to changes produced in the composition and structure of communities after a perturbation. There are different grades of successions according to the perturbation intensity.

·        Primary succession: The perturbation is so intense that it eliminates all the forms of life in the area. It is the sequence of species appearance in an exposed area that has not been influenced by any other species or community before. It occurs when a new extension appears or emerges, or the rock gets exposed but it can not be colonized directly. This propitiates a new habitat that might be colonized for the first time. The new area needs to suffer erosion and different chemical and physical processes that fragment, degrade and dissolve the rock to make colonization possible.

·        Secondary succession: The perturbation has partially or completely removed all vegetable life forms, but the soil is still good, fertile, has spores and seeds.

In any case, succession begins with a few invasive species called pioneers, which are the first to colonize the area.

A primary succession might occur, for example, after a volcanic eruption, where lava produces new rock as it flows. This new rocky extension must suffer weathering and other natural forces that fragment the rock and make a place for new resistant species to grow, such as lichens. These are the pioneer species and they do not have many soil requirements. They help to degrade even more the rock and to form new and better soil where less resistant species may grow. Eventually, these new species will replace the pioneers.  

answer: land bridge theory. land bridge theory held that shifting portions of dry land explained the finding of identical species on different continents. plate tectonic theory eventually eliminated the land bridge theory.