Jean-Baptiste de Lamarck, a french naturalist was able to observed and saw evidences that organisms change through times. In the year 1809 he proposed that  the environment plays an important role why organisms changes. According to him, organisms evolved in response to their environment. Lamarck shows two basic facts as the basis of this observations. the first is the fossil records showing evidences that some organisms before are different from those who are living today. The second is the observation that organisms are well adapted on the environment in where they live.

Jean-Baptiste de Lemarck

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This observations developed three assumptions a.) The Theory of needs b.) The Theory of use and disuse c.) The Theory on passing on acquired traits.

The Theory of Needs

In the Theory of Needs, it is assumed that the organisms need to change in order to survive on its environment. It is assumed that organisms has an inborn urged to make their self better. This urge was developed because of their ancestors wants. An example for this are the giraffe, it is assumed that giraffe may have long necks because their ancestors before developed an urge to have a long neck for reaching the leaves of long trees. Same as the birds developed their wings because their ancestors has an urged to fly in order to fit with their environment. Same as the other animals such as the deer to have along and a swift legs for escaping predators. It was therefore assumed that every organism adapts in the environment in a certain way of life.

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Theory of Use and Disuse

The Theory of Use and Disuse explained that the animals may developed or change through times, depending on their needs. Parts of their bodies could be altered or re changed to be able to be fit with the existing environment. Hence birds trying to use their front limbs for flying purposes, eventually time change those limbs into wings. Another example are the snakes who where believe to have legs and short bodies, they change through times altering those legs and use to crawl, it is because they need to walk to narrow places, and they began to stretch their bodies rather than to walk.

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Theory of Acquired Traits

As explained by Lamarck, the developed changes was pass from parents to offspring. If an organism eventually developed a new body structure such as wings, long limbs or long necks, these characteristics could be pass into  the offspring, and this is what makes evolution.