I think the inheritance process in cases like the rat, tomato, etc. it's not necessarily an acquired trait that's passed on....    I see it more like a range of capacities that the organism has, for example:    Let's say a particular individual of tomato plant has genetic code that allows it to grow inside a range from 1mt to 6mt... now for simplicity sake let's say that how much it grows it's controlled by the concentration of CO2 in the environment it develops, of course this input is also subject to an accepted range, let's say 10% to 60%.    This means that if this individual develops in a 10% C02 environment it will only grow up to 1mt, anything less than 10% is lethal, in the same manner in an environment of 60% it'll grow up to 6mt, anything more than 60% is also lethal.    So even if you clone this individual organism you'll end up with plants of different sizes depending on the environment they develop, not changing a single gene in it's DNA.    Now if we add the randomness of mutation to the scenario, we can get individuals whose CO2 tolerance is lower than 10% and higher than 60%, resulting in sizes lower than 1mt and higher than 6mt, BUT (and here lies the trick) the mutated individuals will be naturally selected depending on the environments current CO2 range let's say it's 50% to 70%, this will produce that individuals whose tolerance range fall or tops the environment's will die off and only the ones around that range will survive and proliferate, if the environment range goes up, so will the organism population average tolerance and the opposite if it goes down.    Of course this is subject to biology's own rules of how higher or lower a tolerance range for CO2 can be fiscally supported by an organism, an it's obviously way more complex than a single trait that relates to a single tolerance range, but I think this hypothetical example makes my point. :D