Which of these is a technique used in forest management, farming, prairie restoration or greenhouse gas abatement where a fire i
s started intentionally during the cooler months to reduce fuel buildup and decrease the likelihood of serious hotter fires. It also stimulates the germination of some desirable forest trees, thus renewing the forest.
This is called 'controlled' or 'prescribed' burning. Usually fires in the environment are regarded as undesirable and dangerous, but fires actually fulfil an important ecological role, and animals and plants had adapted to a certain frequency and intensity of fires. The seeds of some trees or grasses germinate after forest or grass fires, as the more open conditions after a fire allows the seedlings to compete and avoid being shaded and smothered by more established trees. Unfortunately, farming and forestry practices have in many cases resulted in a reduction of fires. A reduction in the frequency of fires also allows the build up of dead wood, and when a wild fire does occur, the amount of available fuel results in very hot, large and damaging fires. Therefore, management of forests and other environments such as prairies often use controlled burns to avoid the buildup of dead organic mass and to replicate the natural fire cycle.
Chromosomes can exchange genetic information during a process called "crossing over." This occurs when homologous chromosomes are lined up in pairs. This recombination of maternal and paternal genetic material is a key feature of meiosis.
A keystone species helps define an entire ecosystem. Without its keystone species, the ecosystem would be dramatically different or cease to exist altogether.
