Evolution

Theory Development

Charles Darwin and Alfred Wallace independently proposed a theory of evolution whilst collecting a range of evidence towards it, separately. 20 years after their independent work, they collaborated and published their scientific ideas in 1858. They proposed the idea that all species of living things have evolved from simple life forms over a long period of time. There is a lot of scientific research to suggest that living things existed, billions of years ago.

Theory of Evolution

Alfred Russel Wallace independently proposed the theory of evolution by natural selection. He published joint writings with Darwin in 1858 which prompted Darwin to publish On the Origin of Species (1859) the following year.

Wallace worked worldwide gathering evidence for evolutionary theory. He is best known for his work on warning colouration in animals and his theory of speciation.

Alfred Wallace did much pioneering work on speciation but more evidence over time has led to our current understanding of the theory of speciation.

Charles Darwin, as a result of observations on a round the world expedition, backed by years of experimentation and discussion and linked to developing knowledge of geology and fossils, proposed the theory of evolution by natural selection. Individual organisms within a particular species show a wide range of variation for a characteristic. Individuals with characteristics most suited to the environment are more likely to survive to breed successfully. The characteristics that have enabled these individuals to survive are then passed on to the next generation. There was much controversy surrounding these revolutionary new ideas in his book On the Origin of Species (1859). The theory of evolution by natural selection was only gradually accepted because:

  • The theory challenged the idea that God made all the animals and plants that live on Earth
  • There was insufficient evidence at the time the theory was published to convince many scientists
  • The mechanism of inheritance and variation was not known until 50 years after the theory was published.

Other theories, including that of Jean-Baptiste Lamarck, are based mainly on the idea that changes that occur in an organism during its lifetime can be inherited. We now know that in the vast majority of cases this type of inheritance cannot occur.

If two populations of one species become so different in phenotype that they can no longer interbreed to produce fertile offspring they have formed two new species.

Evidence for Evolution

The theory of evolution by natural selection is now widely accepted.

Evidence for Darwin’s theory is now available as it has been shown that characteristics are passed onto offspring in genes. There is further evidence in the fossil record and the knowledge of how resistance to antibiotics evolves in bacteria.

Fossils

Fossils are the ‘remains’ of organisms from millions of years ago, which are found in rocks. Fossils may be formed:

  1. From parts of organisms that have not decayed because one or more of the conditions needed for decay are absent
  2. When parts of the organism are replaced by minerals as they decay
  3. As preserved traces of organisms, such as footprints, burrows and rootlet traces.

Many early forms of life were soft-bodied, which means that they have left few traces behind. What traces there were have been mainly destroyed by geological activity. This is why scientists cannot be certain about how life began on Earth. We can learn from fossils how much or how little different organisms have changed as life developed on Earth.

What are fossils?
Your answer should include: Remains / Organisms / Millions / Years / Ago / Rocks
Explanation: Fossils are the ‘remains’ of organisms from millions of years ago, which are found in rocks.
Which two famous scientists worked together to create the theory of evolution?
Your answer should include: Charles / Darwin / Alfred / Wallace
What are Jean-Baptiste Lamarck’s view on evolution?
Your answer should include: Changes / Organism / Lifetime / Inherited
Explanation: Changes that occur in an organism during its lifetime can be inherited.