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Term Term description
Haber-Bosch process

An industrial method of directly synthesizing ammonia (NH3) from hydrogen (H+) and nitrogen (N2), developed by the German chemists Fritz Haber and Carl Bosch. This has led to an annual doubling of the amount of atmospheric nitrogen that is fixed and made biologically available, in turn having significant impacts on ecosystem processes.


The area or natural environment in which an organism or population normally lives. A habitat is made up of physical factors such as soil, moisture, range of temperature, and availability of light as well as biotic factors such as the availability of food and the presence of predators. A habitat is not necessarily a geographic area, for a parasitic organism it is the body of its host or even a cell within the host's body.

habitat fragmentation

When a habitat is broken into several smaller section by human activities and construction (e.g. roads, agriculture, cities) the organisms are confined to smaller areas of land with fewer resources. Fragmented habitats greatly impede animal migrating patterns.

Hadley cells

Circulation patterns of atmospheric convection currents that are strongest and most well defined at the equator. These circulating cells of atmosphere carry equatorial hat toward the north and south poles.

heat engine

An engine that converts heat energy into mechanical energy.

heat sink

Any environmental landscape or medium that absorbs heat is a heat sink. For example, forests and oceans can absorb heat better that a city landscape.

heavy soils

Soils with a high percentage of small clay particles and characterized by slow water infiltration into the soil, slow water percolation through the soil, low soil aeration, and a tendency for the soil to hold moisture with great tension.


A unit of area in the metric system that is equal to 10,000 square meters or 2.47 acres.


Personification of the Sun in Greek mythology.

Henry's Law

Henry's Law states that the solubility of a gas in a liquid is directly proportional to the partial pressure of the gas above the liquid. For example, the amount of CO2 that is dissolved in the earth's oceans is directly proportional to the concentration of CO2 in the atmosphere directly over the oceans. As [CO2] in the atmosphere increases, so does the [CO2] dissolved in the ocean water which causes ocean acidification.


Chemical substances that are toxic to plants and used to destroy unwanted vegetation or "weeds" in agriculture.


An animal that feeds mainly (or only) on plants.


An organism that cannot manufacture its own food and instead obtains its food and energy by taking in organic substances, usually plant or animal matter. All animals, protozoans, fungi, and most bacteria are heterotrophs.

high yield crop

High-yield agricultural crops are those that have been bred, genetically modified, or fertilized to increase their production yields.


In Islam, an area set aside for the conservation of nature, typically including fields, wildlife, and forests.


An ancient  and diverse religious and cultural tradition of Southeast Asia, characterized by the belief in reincarnation, one absolute being of multiple manifestations, the law of cause and effect, following the path of righteousness, and the desire for liberation from the cycle of births and deaths.

holy water

In Christianity, water that has been blessed by a priest or other religious leader and used in religious practices and ceremonies.



The tendency of an organism or cell to regulate the chemical processes that take place internally so as to maintain health and functioning, regardless of outside conditions. The ability to maintain a steady body temperature is an example of homeostasis.

Any of a family (Hominidae) of erect bipedal primate mammals that includes recent humans together with extinct ancestral and related forms and in some recent classifications the gorilla, chimpanzee, and orangutan
Homo sapiens
(Latin for “wise man”) The species to which all modern human beings belong. Homo sapiens is one of several species grouped into the genus Homo, but it is the only one that is not extinct.

An expert in the science of cultivating plants (fruit or flowers or vegetables or ornamental plants).

human dignity

The moral quality of human personhood by virtue of one's body, mind and soul, and expressed in human autonomy, equality, freedom, sociality and sacrality.

human rights

Moral powers of human personhood by virtue of human dignity that call for a person or group’s immunity from unjust harm (e.g. the right not to have my bodily integrity abused, the right not to have my expression of ideas suppressed, the right not to have my practice of religion forbidden) and entitlement to basic goods necessary for life (e.g. my right to food, my right to shelter, my right to health care).


When a person demonstrates humble traits such as mildness, modesty, patience and deference.


A brown or black organic substance consisting of partially or wholly decayed vegetable or animal matter that provides nutrients for plants and increases the ability of soil to retain water.


The act of mixing or reproductively crossing different species or varieties of animals or plants and thus to produce hybrids. Hybridization occurs naturally in nature, but can be done artificially by humans in agriculture practices to produce hybrids with desired traits.

hydraulic fracturing

(fracking) A controversial process of natural gas extraction, where millions of gallons of water, sand and chemicals are pumped underground to break apart the rock and release the natural gas for use as an energy source.


Chemical made up of carbon and hydrogen that are found in raw materials such as petroleum, coals and natural gas, and derived products such as plastics.

hydrogen bond

A chemical bond connecting a hydrogen atom of one molecule to an electro--negatively charged atom, especially a nitrogen, oxygen, or fluorine on another molecule.

hydrologic cycle

The natural cyclic transfer of water vapor from the Earth's surface via evaporation into the atmosphere, from the atmosphere via precipitation back to earth, and through runoff into streams, rivers, and lakes, and ultimately into ground water and the oceans.

hydrologic cycle

The natural cyclic transfer of water vapor from the Earth's surface via evaporation into the atmosphere, from the atmosphere via precipitation back to earth, and through runoff into streams, rivers, and lakes, and ultimately into ground water and the oceans.


Water-loving. In Chemistry, a term applied to polar molecules that can form a hydrogen bond with water.


Water-fearing. In Chemistry, a term applied to nonpolar molecules that cannot bond with water.


All of the Earth’s water; this would include water found in the sea, streams, lakes and other waterbodies, the soil, groundwater, and in the air.

hydrothermal vents

A fissure on the floor of a sea out of which flows water that has been heated by underlying magma. The water can be as hot as 400°C (752°F) and usually contains dissolved minerals that precipitate upon contact with the colder seawater, building a stack of minerals, or chimney. Hydrothermal vents form an ecosystem for microbes and animals, such as tubeworms, giant clams, and blind shrimp that can withstand the hostile environment.


Any of the threadlike filaments produced by certain bacteria.

hyporheic zone

A region beneath and alongside a stream bed, where there is mixing of shallow groundwater and surface water.


A supposition or proposed explanation of a phenomenon made on the basis of limited evidence as a starting point for further investigation.


Inadequate levels of oxygen for survival, particularly in aquatic, marine and soil environments.

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