Darwin, Wallace & Lamarck

This lesson covers:

  1. The work of Darwin and Wallace in the development of the theory of evolution
  2. Darwin and Wallace's theory of evolution
  3. Why the theory of evolution was only gradually accepted

Darwin and Wallace


Theories and and understanding around evolution have changed drastically over time. Nowadays, the majority of scientists accept the theory of evolution by natural selection, which was proposed by Darwin and Wallace.

Charles Darwin made a number of important observations:

  1. Individual organisms within a species show a wide range of variation for a specific trait.
  2. Darwin observed variations between species adapted to different environments.
  3. Older layers of rock contained fossils of less complex organisms, while more recent layers showed more organisms.

Charles Darwin and Russel Wallace independently proposed the theory of natural selection:

In his book, "On the Origin of Species", Darwin proposed that natural selection is the driving force behind the gradual development of species over time.


Russel Wallace independently arrived at a similar conclusion to Darwin, and they later presented a joint paper together, providing additional support to the theory.

Illustration showing two giraffes, one with a shorter neck labeled less likely to survive and one with a longer neck labeled more likely to survive, demonstrating natural selection.

According to Darwin and Wallace's theory, giraffes have long necks because:

  1. Some giraffes had longer necks than others, due to variation within the species.
  2. Giraffes with longer necks were better adapted to their environment, as they could eat leaves from taller trees.
  3. Giraffes with longer necks had a higher chance of surviving and reproducing, and passed on the trait of long necks to their offspring.
  4. Over many generations, this process produced modern giraffes, with very long necks.

It took time for the theory of evolution to become widely accepted


Many people didn't accept Darwin and Wallace's theory, for several reasons:

  1. Religious reasons - Darwin's theory challenged the religious belief that God created all life forms.
  2. Lack of evidence - a lack of hard evidence made many scientists hesitant to accept Darwin & Wallace's theory.
  3. DNA hadn't been discovered yet - the mechanism for inheritance and variation, now understood through genetics, was unknown during Darwin's time.

According to Darwin and Wallace's theory, what is the driving force behind the gradual development of species over time?

Natural selection

Genetic mutation

Environmental adaptation

Inheritance of acquired traits

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According to Darwin and Wallace's theory, why do giraffes have long necks?

Giraffes with shorter necks had a higher chance of surviving and reproducing

All of the above

Giraffes with longer necks were better adapted to their environment

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