At the molecular level, gene duplication often produces novelty in a lineage. This process provides another evolutionary pathway by which a protein can switch functions, without loss of the original function. What analytical approach helped the most to answer the question of evolution in the aldosterone-M receptor pair in the study of Jamie Bridgham and her colleagues

Bridgham et al. (2006) showed that the interaction between a steroid hormone (aldosterone-M) and its receptor (mineralocorticoid) evolved by Darwinian gradualism. In this work, the authors demonstrated  a primitive affinity between the hormone and its receptor that was initially present in chemically similar but more ancient ligands. This result has implications in understanding the association between gene duplication and the evolution of hormone signaling pathways. For example, in invertebrates, this work reinforces the importance of gene duplication in the existing interaction between paralogous glucocorticoid receptors and their receptor mineralocorticoid genes that were derived from duplication (Thornton 2001).

The publications above cited are the following:

J.T. Bridgham, S.M. Carroll, and J.W. Thornton (2006). Evolution of hormone-receptor complexity by molecular exploitation. Science, 312(5770), 97-101.

JW Thornton. Evolution of vertebrate steroid receptors from an ancestral estrogen receptor by ligand exploitation and serial genome expansions, Proc Natl Acad Sci USA (PNAS), 2001, vol. 98 10 (pg. 5671-5676).

he is very short, and he can only reach halfway up on the elevator buttons. but on a rainy day, he has his umbrella with him, and he uses it to poke the button at the top.

when the displaced particles are perpendicular to the direction the wave travels, is called a transverse wave, whereas in longitudinal wave the displace practices are parallel to the direction of the wave.

in the given image:

first image shows - longitudinal wave

second image shows - transverse wave

third image shows - longitudinal wave

fourth image shows - longitudinal wave