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Summary Life sciences notes matric - evolution
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EVOLUTIONDevelopment of the theory of evolution
What is evolution?
The gradual change or development of something
What is biological evolution?
The change in the gene pool of a population during the course of time by such processes
such as mutation, natural selection and genetic drift
o Descent with modification
Micro-evolution: evolution within a species
Macro-evolution: the decent of different species from a common ancestor over
many generations
Why is it so important that we know about biological evolution?
• Has become the unifying concept that acts as foundation for understanding all
biology
• Supports and explains many aspects of everyday life
• Challenges people to really think for themselves
How did life originate?
Þ Source of speculation
Þ Current scientific opinion = there was a single origin of life
All life shares the same genetic code and similar basic enzymes
Þ Only thing certain is that life on earth appeared very early – about 3.7 mya
How did species diversity originate?
A- Before 1700
Most scientists accepted that:
§ Species were unrelated and remained unchanged
§ The earth was young, perhaps only 6000 years old and static (unchanging)
, EVOLUTION
B- 1700 to early 1800
Creative thinkers such as Erasmus Darwin and Jean-Baptiste Lamarck began to
challenge these concepts
They became convinced that:
§ Species had changed gradually over time
§ The earth was millions of years old
ERASMUS DARWIN
o 1731- 1802
o Successful country doctor, scientist, philosopher, inventor, poet and author
o Famous book: Zoonomia
o Put forward the idea that life on earth descended from a common ancestor
o He suggested that species must have changed or evolved over time
JEAN-BAPTISTE LAMARCK
o 1774- 1829
o French naturalist
o Book: Philsophie Zoologique
o Proposed that species were not fixed
Observations include:
Þ Living species are different to fossil types
Þ Domestication and selective breeding resulted in animals and plants changing
Þ Cross-breeding of plant species led to new characters appearing
How did Lamarck suggest that species changed?
He suggested that organisms changed during their lifetime so that they could survive
in new environments and that these acquired changed were then passed on to
offspring
Þ Use and disuse of body parts
Þ Inheritance of acquired characteristics (known as Lamarckism)
Some examples of Lamarckism:
Þ Long neck and legs of modern giraffe were result of generations of short-
necked and short-legged ancestors
Þ Stretching necks to feed on leaves at higher levels
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