Modification of
basic body plants
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, Darwin and evolution
Charles Darwin, born in England
• Noted observations of animals, plants and geology.
• Wondered why there was such a variety of species on Earth (living & extinct)
• Asked why some species only differed slightly from others
• Thought about how each organism had become so well adapted to its environment.
1859: Formulated theory of “descent with modification.”
Now referred to as theory of Evolution through natural Selection
Biological evolution is the process of change by which new species develop from pre-existing species
over time.
Darwin realised that separate groups of animals tend to have certain basic structures in common even
though these structures are modified to perform different functions.
Organisms with similar structures might have acquired these traits from a common ancestor and therefore
they must be on the same evolutionary lineage.
From the ancestral population members of a species moved to different environments
↓
Those with characteristics that were better suited to different circumstances survived & reproduced
↓
These individuals passed these characteristics on to their offspring and gradually body plans were
modified
↓
Eventually new species were formed
This is called adaptive radiation.
Morphological divergence:
Development of different structural characteristics in organisms that come from the same ancestor.
Homologies or homologous structures:
Structures that have certain features in common with each other and with the ancestral stock from which
they arose.
•A result of divergent evolution. Allowed descendants to fill a wide variety of ecological niches.
•Darwin able to explain how living species are connected to similar species living nearby.
Page 2 of 7
basic body plants
Page 1 of 7
, Darwin and evolution
Charles Darwin, born in England
• Noted observations of animals, plants and geology.
• Wondered why there was such a variety of species on Earth (living & extinct)
• Asked why some species only differed slightly from others
• Thought about how each organism had become so well adapted to its environment.
1859: Formulated theory of “descent with modification.”
Now referred to as theory of Evolution through natural Selection
Biological evolution is the process of change by which new species develop from pre-existing species
over time.
Darwin realised that separate groups of animals tend to have certain basic structures in common even
though these structures are modified to perform different functions.
Organisms with similar structures might have acquired these traits from a common ancestor and therefore
they must be on the same evolutionary lineage.
From the ancestral population members of a species moved to different environments
↓
Those with characteristics that were better suited to different circumstances survived & reproduced
↓
These individuals passed these characteristics on to their offspring and gradually body plans were
modified
↓
Eventually new species were formed
This is called adaptive radiation.
Morphological divergence:
Development of different structural characteristics in organisms that come from the same ancestor.
Homologies or homologous structures:
Structures that have certain features in common with each other and with the ancestral stock from which
they arose.
•A result of divergent evolution. Allowed descendants to fill a wide variety of ecological niches.
•Darwin able to explain how living species are connected to similar species living nearby.
Page 2 of 7
