( ( ( Some species ) ( of arthropods ) ) ( ( ( reproduce ( through ( external fertilization ) ) ) ( whereas ( others ( use ( internal fertilization ) ) ) ) ) . ) )
(ROOT (S (NP (NP (DT Some) (NN species)) (PP (IN of) (NP (NNS arthropods)))) (VP (VBD reproduce) (PP (IN through) (NP (JJ external) (NN fertilization))) (SBAR (IN whereas) (S (NP (NNS others)) (VP (VBP use) (NP (JJ internal) (NN fertilization)))))) (. .)))
Some species of arthropods reproduce through external fertilization whereas others use internal fertilization.
(ROOT (S (NP (NNS Amphibians)) (ADVP (RB sexually)) (VP (VB reproduce) (PP (IN through) (NP (JJ external) (CC or) (JJ internal) (NN fertilization)))) (. .)))