Which of the following examples of an ecological study involves the ecosystem level of organization?
1. effects of competition on survival
2. effects of an invasive plant species on birds nesting sites
3. effects of a disease on population size
4. the effects of human activities on biogeochemical cycling

Which of these is not an example of molecular homology? 1. use of dna and rna as genetic material 2.use of glycolysis as the first step in cellular respiration in both plants and animals 3. the lack of an igf-1 gene in prokaryotes 4. the use of aldolase b to break down fructose in bacteria, plants and animals