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Lecture 2

BIOLOGY 1M03 Lecture Notes - Lecture 2: Internal Consistency, Special Creation, Aniridia

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Jon Stone

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BIOLOGY 1M03- Lecture 2- Chapter 24 Evolution by Natural Selection
Part 1
Key Concepts
Populations and species evolve, meaning that their characteristics change through time
Evolution: Changes in allele frequencies over time
Evolution by natural selection occurs when individuals with particular alleles survive or
reproduce more effectively than their competitors in a population
Adaptation: A genetically based trait that increases a typical individual’s ability to survive and
produce offspring in a particular environment
Evolution by natural selection is not progressive, and does not change the characteristics of the
individuals; it only changes the characteristics of the population
Animals may behave altruistically in SOME conditions, and not all traits are adaptive
All adaptations are constrained by trade-offs and by genetic historic factors
Scientific theories often comprise observations about a natural pattern and a proposed process
that explains that pattern.
In the theory of evolution by natural selection, Charles Darwin and Alfred Russel Wallace in 1858
made the claim that evolution has occurred, that species have changed through time. Then the
authors proposed natural selection as a process to explain the pattern of evolution.
Evolution by natural selection has become one of the best-supported and most important
theories in the history of scientific research
24.1 The Evolution of Evolutionary Thought
Plato claimed that every organism was an example of a perfect essence of type created by God
and that these types were unchanging
Typological thinking involves the idea that species are unchanging types and that variations
within a species are unimportant/misleading
Aristotle ordered these types of organisms into a linear scheme called the great chain of being
In this chain, species were organized into a sequence based on increasing size and complexity
(with humans at the top)
This great chain of being remained popular in religious and scientific though into the 18th
Lamarck and the Idea of Evolution as Change Through Time
In 1809 Jean-Baptiste de Lamarck was the first to propose a formal theory of evolution.
Lamarck proposed that simple organisms originate at the base of the great chain by
spontaneous generation and then evolve by moving up the chain over time
He also suggested that the process responsible for this pattern was the inheritance of acquired
He theorized that individuals change in response to their environment and then pass those
changes on to their offspring
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