Which step of the nitrogen cycle occurs only in aquatic ecosystems? A. Cyanobacteria convert nitrogen into ammonium
B. Soil bacteria convert nitrogen into ammonium
C. Soil bacteria convert ammonium into nitrate
D. Ammonium enters the ecosystem when humans fertilize soil
E. Nitrates enter the ecosystems when humans fertilize soil

Which organisms have pharyngeal arches that develop from all three germ layers and go through the same development stages as embryos? 1.bird 2.ladybug 3.starfish 4.snake

Why reason best illustrates why hershey and chase chose to use viruses in their experiment?

The phylogenetic tree illustrates the relationship between humans and our closest living relatives. the tree was based on biochemical comparisons, including dna and amino acid sequences. according to the biomolecular data, we could infer that a) the four organisms do not have a common ancestor. b) humans are more closely related to chimps than any other apes. c) chimps are more closely related to gorillas than they are to humans. eliminate d) there is no evidence if any relationship between the four branches on the tree.