Answer:
He identified that diseases are caused by malfunctioning cells.
That all cells arise from pre-existing cells.
If your car is changing speed by accelerating or decelerating, or changing directions by turning or hitting a bump, your body can sense these accelerations. You might be pressed against the back of your seat while speeding up or against the car door as you turn for example. If you are cruising at a constant speed, with no changes in speed or direction, you wouldn't be able to feel it. You would need to use your other senses. You could see the scenery going by through the windows, with closer objects moving by more quickly than objects in the distance. You could also hear sounds like the wind rushing by and the hum of the tires rolling on the highway.
Answer:
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).
