Cardiac glycosides (e.g., ouabain and digitalis) are a class of drugs that inhibits Na+-K+ ATPase.

TLS Online TPP Program

#Id: 9553

#Unit 11. Evolution and Behavior

Natural selection was Darwin’s brilliant hypothesis, that accounts for adaptations, features that appear “designed” to fit organisms to their environment.

TLS Online TPP Program

#Id: 9554

#Unit 11. Evolution and Behavior

Alfred Russel Wallace - Who was collecting specimens in the Malay Archipelago, had independently conceived of natural selection

TLS Online TPP Program

#Id: 9555

#Unit 11. Evolution and Behavior

Populational change is Darwin’s hypothesis that evolution occurs by changes in the proportions (frequencies) of different variant kinds of individuals within a population.

TLS Online TPP Program

#Id: 9556

#Unit 11. Evolution and Behavior

TLS Online TPP Program

#Id: 9557

#Unit 11. Evolution and Behavior

Where, though, do these hereditary variations come from?

This was the great gap in Darwin’s theory, and he never filled it. The problem was serious because, according to the prevailing belief in blending inheritance, variation should decrease, not increase.

TLS Online TPP Program

#Id: 9558

#Unit 11. Evolution and Behavior

Orthogenesis - “Straight-line evolution,” held that the variation that arises is directed toward fixed goals.

So that a species evolves in a predetermined direction by some kind of internal drive, without the aid of natural selection.