origin of an idea about origins

scientific theory

general explanation of an important natural phenomenon with a reliable body of evidence that has developed through extensive and repeated observations and experiments to support it

5 different lines of evidence supporting evolution

• fossil records

• biogeography

• genetics

• homology

• embryology

4 ways in which fossil records support evolution

• increase in complexity over time

• increase in diversity

• decent with modification (changes can be traced)

• transitional fossils (intermediate forms showing one group gave rise to another)

what can genetics tell us and how

• organisms descended from common ancestor

  • all have DNA & RNA

  • genes encoded to make identical proteins (enzymes in cellular respiration)

• how closely related organisms are

  • similarity of sequences of chromosomal DNA and mtDNA

  • more sequences shared → closer the relationship and how recent they diverged from common ancestor

example of homologous structure

pentadactyl forelimb in vertebrates

ideas before 1700

• divine power created unrelated species that remained unchanged

• Earth was young (6000 years old)

ideas during 1700 - 1800

• species had changed gradually over time

• Earth was millions of years old

two people who challenged previous ideas from before 1700

Erasmus Darwin + Jean-Baptiste Lamarck

contribution of Erasmus Darwin

wrote ‘Zoonomia’ that said life descended from common ancestor but offered no mechanism for evolution (transformation)

what theory did Jean-Baptiste Lamarck introduce and explain

• theory of inheritance of acquired characteristics (Lamarckism)

• use and disuse of body parts

  • environment changed → organism acquired new characteristic to adapt (eg organ size)

• inheritance of acquired characteristic

  • phenotypic change acquired by parent passed onto offspring → population change → new species formed

was Lamarck accurate in his theory and why?

No, phenotypic changes don’t cause environmental change ⇒ characteristics acquired during life is not heritable

difference between Charles Darwin and Lamarck way of evolution

• Lamarck: linear, simple organism → complex organism

• Darwin: branding → one ancestral species gave rise to two or more new related species

what expedition did Darwin go on

5 year expedition on his HMS Beagle across southern hemisphere

what book did Charles Darwin write and name 5 things it proposed

• common ancestor

• ancestral species → adaptation to new conditions → diversified into new species

• branching → one ancestral species gave rise to two or more new related species

• extinction

• natural selection (mechanism for evolution)

what was Alfred Wallace’s contribution

• in Malay Archipelago:

  • puzzling distrubition of two groups of organisms in north-western part & south-eastern part (Wallace’s line)

  • one was more like those on the Asian mainland and the other was like those in Australia

  • became isolated by deep seaways → evolved

  • brancing pattern of evolution