Image Sources
(1) USDA.
http://en.wikipedia.org/wiki/File:Cropduster_spraying_pesticides.jpg.
Public Domain.(2) http://en.wikipedia.org/wiki/Image:Snake_browntree.jpg. GNU-FDL.(3).(4) http://en.wikipedia.org/wiki/File:Mauna_Loa_Carbon_Dioxide.png.
GNU-FDL.(5) http://en.wikipedia.org/wiki/Image:Population_curve.svg. Public Domain.(6) USFWS.http://commons.wikimedia.org/wiki/File:Coral_Reef.jpg. Public
Domain.(7) http://commons.wikimedia.org/wiki/File:Nur04512.jpg. Public Domain.(8) http://en.wikipedia.org/wiki/Image:Hummingbird_hawkmoth_a.jpg. CC-BY-SA
2.5.(9) http://en.wikipedia.org/wiki/Image:
World_population_growth_-_time_between_each_billion-person_growth.svg.
Public Domain.(10) http://en.wikipedia.org/wiki/Image:EltonFW.jpg. Public Domain.
(11) A giraffe is an example of a vertebrate.. GNU-FDL.
(12) http://en.wikipedia.org/wiki/Image:
Percentage_living_on_lessthan%241_per_day_1981-2001.png. Public Domain.
(13) USFWS.http://upload.wikimedia.org/wikipedia/commons/thumb/3/30/Ursus_
maritimus_Polar_bear_with_cub_2.jpg. Public Domain.
(14) Fungi are decomposing this tree.. CC-BY 2.5.
(15) http://en.wikipedia.org/wiki/Image:Tractors_in_Potato_Field.jpg. CC-BY
2.0.
(16) http://en.wikipedia.org/wiki/Image:Equisetum_arvense_stem.jpg. GNU-FDL.
(17) http://en.wikipedia.org/wiki/Image:Food_chain.jpg. Public Domain.
(18) NASA.http://en.wikipedia.org/wiki/File:Carbon_cycle-cute_diagram.jpeg.
Public Domain.
