Living Environment Translated Arabic 2014 | Page 70

52. Nitrogen fixation- the process in which some types of bacteria in
the soil change nitrogen gas into a form of nitrogen that plants can
use
53.Carbon cycle- a model that describes how carbon molecules move
between the living and nonliving world
54. Energy pyramid- a diagram that compares energy levels used by
producers, primary consumers, and other energy levels.
55. Succession- natural, gradual changes in the types of species that
live in an area
56. Primary succession- establishment and development of an
ecosystem in an area that previously had no soil or plants
57. Pioneer species- organisms that are the first to live in an previously
uninhabited area
58. Secondary succession- reestablishment of a damaged ecosystem in
an area where the soil is still intact
59. Climax community- a stage of succession community of plants that
is relatively stable and undisturbed and has reached an end
60. Native species- an organism that naturally lives in an ecosystem
61. Introduced species- an organism that does not naturally live in an
ecosystem and is brought into a foreign ecosystem
62. Sustainability- the ability of an ecosystem to maintain itself
without using up all of its natural resources