Then, those survivors would reproduce and pass on "superior traits". In my drawing there are two species of birds, one has a long beak (species A) and the other a small beak (species B).
Both species of birds are trying to get food out of the tree but the species with the small beak does not reach it. Species B dies and Species A lives on and reproduces. Species A's offspring now posses the gene for the long beak and when they reproduce, they'll pass it on too. Lamarck's Theory: Lamarck believed that there was no ancestor species and that the species would acquire new traits after a long period of time only if they practiced using a specific trait.
For example, in my drawing I have one giraffe straining his neck trying to reach higher food.
There are also two other ones that have no clue now to reach the higher food. As a result of constantly straining his neck to reach the food, his offspring grew longer necks and then their offspring grew longer necks. The end result is all giraffes eventually start to have long necks as each generation goes on and they can all reach the food now.