The development of scientific explanations


In 1859 Charles Darwin published one of the most important books in all biology called 'On the Origin of Species'. It followed his round-the-World expedition during which he visited the Galapagos Islands. He first developed this theory of evolution by natural selection in the late 1830s. He delayed publication for fear of the reaction from the Church.

Obtaining evidence for evolution is challenging. Scientists originally looked for small but gradual changes in organisms within the fossil record. The case study of the peppered moth obtained more evidence.

Scientists now use evidence that did not exist during Darwin's lifetime:

  • development of antibiotic resistant bacteria like MRSA
  • DNA analysis

New explanations are not usually accepted until more evidence is found.


Memory is a person's ability to store and retrieve information. It can be divided into your short-term and long-term memories. Short-term memory lasts for about 30 seconds. Long-term memory lasts an entire lifetime. Although revising for exams is difficult, there is no limit to the amount of information that can be stored in long-term memory. People who have sadly suffered brain damage, lose their long-term memory but can retain their short-term memory. This suggests that they work in different ways.

The multistore method for memory is a model to try to explain how our short-term and long-term memories interact. It is regarded as a good model but does not yet provide an exact explanation.

A flow diagram of how a stimuli is processed into short-term and long-term memory