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Lecture 20

BIOL 1001 Lecture Notes - Lecture 20: Neoteny, Flattening, Heterochrony


Department
Biology
Course Code
BIOL 1001
Professor
Tamara Kelly
Lecture
20

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BIO 1001 MACROEVOLUTION CONTINUED MARCH 10TH, 2017
REVIEW:
- Duplicated genes can result in DNA replication and crossing over
- As long as one chromosome maintains its original function the duplicate is free to be
mutated
- We can get big changes in the body by altering the expression of a gene and
regulating when it turns on and off
Growth Patterns:
- Isometric growth Adult proportions are not significantly different than younger offspring
o Ex. Human’s do not experience isometric growth
- Allometric growth relative growth rates of different body parts during
development
Timing is everything:
- We can compare timing and pace of development between closely related species
therefore looking at
heterochrony
- Heterochrony changes in timing of developmental events between two taxa
o Difference between skulls of chimps and humans
There are times when growth starts and when growth stops between
the two
o Closely related salamander leg growth
Each is adapted for specific environment (mutation where there was a
change in gene that controls foot growth)
Changes in development timing:
- Juveniles are differentiated from adults by their inability to reproduce not by
specific morphology
- Ex. Animals some somatic cells can develop at a certain time
- Some species can get a mutation that allows them to reproduce earlier than normal
- Ex. Juvenile tiger salamander vs. Adult tiger salamander
o Juvenile are aquatic
o Then, reorganization of body
o Adult tiger are more on land
o This is an example of somatic development
- If you have somatic body cell development, normal development rate (ancestral)
- But our somatic development slows down, our reproductive development is at the
same rate (neoteny)
o Which can prove why some can be reproductively mature but somatic isn’t as
developed
o Ex. Animals that still have juvenile features
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