Which of the following scenarios represents change to an ecosystem brought about by biotic factors?
a. a wildfire caused by lightning striking a tree
b. a flood caused by a severe storm
c. a landslide caused by cattle overgrazing
d. a volcano

(select all the correct choose each statement that is scientific. - the opinions of randomly selected participants in a survey prove the idea that global temperatures are not increasing on earth. - the universe's average temperature and rate of expansion support the idea that it began as one super-dense and hot mass 13.8 billion years ago. - ocean tides are caused by the uneven gravitational pulls of the moon and sun on different parts of earth. - human life is more valuable than other forms of life on earth because humans are more intelligent than other organisms.