Which sources do scientists use to reconstruct past climate conditions? check all that apply. fossils frozen in glaciersdaily temperaturespollen grains preserved in sedimentrunning watertree rings

fossils frozen in glaciers, pollen grains preserved in sediment , tree rings

Paleoclimatic records are observed by the scientists all over the world which can be observed from the tops of the mountains to the bottom of the ocean.

Fossils frozen in glaciers: Is the example of the climatic conditions in the past as the rocks preserving fossils are likely to undergo changes in them by the action of weather conditions.

Pollen grains preserved in sediment: Pollen grains are hard substances which are called as male gametes of plants. These remain undegraded by the soil microbes. They remain embedded in the layers of strata depending upon the weather conditions.

Tree rings: In some trees a typical ring can be observed in the cross- section these rings added one in a year are also affected by the external climate of the trees.

step 1: nitrogen fixation- conversion of atmospheric no₂ into forms useful to plants by lightning, bacteria, and cyanobacteria.

step 2: nitrification-process of converting ammonia to nitrite or nitrate.

step 3: assimilation-plant roots absorb new form of nitrogen.

step 4: ammonification-conversion of organic nitrogen to ammonia by bacteria involved in decomposition.

step 5: denitrification-bacteria turns the decomposed matter back into n₂o, which is released into atmosphere; repeat cycle.