Heterochrony changes timing of developmental events o

  • York University
  • BIOL 1001
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  • julianamas
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Heterochrony  changes timing of developmental events o Can only tell by looking at same species o Mutations in genes controlling development can have profound effects on morphology - Body plans are controlled by conserved genes - If expression is altered it can affect growth rate find more resources at oneclass.com find more resources at oneclass.com
What differentiates a juvenile from an adult? - Cannot reproduce while adults can find more resources at oneclass.com find more resources at oneclass.com
BIO 1001 MACROEVOLUTION CONTINUED MARCH 10 TH , 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 iso metric 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 Whi ch can prove why some can be reproductively mature but somatic isn’t as developed o Ex. Animals that still have juvenile features find more resources at oneclass.com find more resources at oneclass.com
- Paedomorphosis retention of juvenile characteristics in adults o Tadpole body but adult reproduction o Flattening of the face in humans find more resources at oneclass.com find more resources at oneclass.com
BIO 1001 HUMAN EVOLUTION MARCH, 13 - Many cladograms don’t pay attention to humans - Humans share common descent with apes (we are apes) o Our DNA is more similar to chimpanzees vs. gorilla-chimpanzee comparison - Evidence for this is genetic and fossil data Why is Pan in a different genus than Homo - Pan = Chimps, Homo = Humans - It is believed that the difference between the two genus’ is very small - Most organism groups

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