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Biology Unit 1- Natural Selection > Charles Darwin > Flashcards

Flashcards in Charles Darwin Deck (11)
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Evidence for evolution is used to prove that

- Life on Earth has changed over time
- All life has descended from common ancestors


independent confirmation

when multiple, independent pieces of evidence point to the same conclusion



- are as old as the rock they belong to
- they are formed from sediment
- there are very few fossils for the number of species which shows that we know very little about earth


Traditional way of classification vs. post evolution theory

Traditionally living organisms have been classified based on morphological and anatomical similarities.
Under the light of evolution: similarities due to the common ancestor.


Evidence for anatomy: Embryology

- Related organisms have very similar developmental stages = inherited from common ancestor

- Embryos often go through stages useful to presumed ancestor but not to current organism - e.g. gill slits in mammals, reptiles, birds
- The more similar the stages, the more similar the organism


Evidence for anatomy: homology

Homologies are similar (but modified) structures that are often put to very different uses in related organisms. That homologous structure was present in the common ancestor but diverged over time.
- this proved that all life came from a common ancestor


Evidence from anatomy:
vestigial structures

Structures with no apparent use in an organism but is homologous with useful structures in other related organisms.
- this shows that life evolved from a common ancestor and that successful traits are inherited by descendants (but they may not use them)
- vestigial structures are homologous structures but it lost its function in one of the groups.


Convergence- analogous structures

- structures that have similar functions and but very different anatomy
- the similarities are due to similar environments but do not demonstrate any recent common ancestry
- not used in phylogeny?


Biochemistry and molecular evidence- not available to Darwin

Analysis of protein structure, immune responses, genetic sequences all show increasing differences as common ancestors become more remote
Can be used as evolutionary clock


Comparative behaviour

- Behavior can also evolve
- Many behaviours are found in variations within one or a few lineages – correlate with anatomical differences
- Mating displays correlate with genetic differences (?)
- Small behavioural changes, sometimes controlled by a single gene, prevent similar - species from mating


evidence conclusion

conclusion is that life has evolved over time. Now it is a question of HOW it has evolved over time.