Lec 15: What darwin saw Flashcards
Why are fossils records incomplete?
Because it only preserves by chance the animals that were managed to be preserved. It doesnt give us the exact ancestor we evolved from, but just gives EVOLUTIONARY TRAJECTORIES
Why was tiktalik or fisherpod important?
It showed the phase where, fishes got limbs to come on to land.
Why are fossils important?
They show evolutionary trajectories over deep time, as they provide record for how organisms change over time.
Supported Darwin’s claims that evolution occurred over time, organisms were not created in a static form
What are key and important things about geography?
- Earth is very old (helps to support darwin’s claims to say organisms evolved over a long historical time)
- Intermediate forms: Evidence of common ancestor, linking features between living and extinct animals.
- Fossils on the top of strata are the fossils of younger organism that are similar to current day’s organisms
What were key observations from Galapagos Islands?
- Vestigial Characters: Flightless birds ( Flightless Cormorants)
2.
What were the reasons flightless cormorants lose the ability to fly?
Possible hypotheses are:
- Decent by Modification: It evolved via natural selection.
- Flying could have been costly, as there are no predators on the Galapagos island, and it should be a good swimmer to catch fish rather then being at flight
What are the examples of animals with Vestigial traits?
- Flightless cormorants
- Blind Cavefish
3.
What are the vestigial characters of blind fish?
- Very little pigment, dark pigment has very little selective advantage
- There are signs that they could once have eyes, but they do not now, since they live in the dark
What are examples of vestigial characters in humans?
- Ear muscles
- Appendix
- Tail bone
4.Goosebumps
How do you know we lost most of olfactory genes?
When plotted Y: % dead gene
X: primates, humans lost the most % of genes, and so did our close relatives.
But the advantages were evolving trichromatic vision.
What is evidence from morphology?
Similarity between the skeletal system for many birds, humans and bats show similar modifications
Bats and birds are not related
But this showed evolution by natural selection, it also shows we were all related.
Bacteria and humans share approximately 500 common genes. This shows common ancestry.
How did organism, cacti get to the fairly new Galapagoes islands?
- The islands were relatively new, old ones were 500-1000 million years whereas the young ones were only a 1Mya
- This would have attracted all the animals that are good at dispersal
- Cacti has fruits, hence it should have attracted them to eat, and birds must have popped them.
Why did different tortoise have different shells in the Galapagos Islands?
- Decent by Modification and evolution by Natural Selection
What led to rapid changes in the finches?
Sudden change in the environment leads to rapid evolution
why was there less diversity on the islands when Darwin observed them?
If only a subset of species can get to the island, then there is a loss of specie diversity upon arrival
What were the key observations form the Galapagos?
- Less diversity in species than in mainland
- Species on these islands resemble the species on the mainland but are slightly different
- Many similar-looking but not identical types of species on different islands.
- the father a specie moves from the mainland, the more different it looks
What is adaptive radiation?
It is a rapid evolution in a way, you get more lineages over a short period of time.
It is the evolution of ECOLOGICAL and PHENOTYPIC diversity within a rapidly multiplying lineage as a result of speciation
What needs to be present for adaptive radiation to occur?
- Originates from a common ancestor
- The process results in a array of many species
- The species differ in traits, that allow it to exploit different resources and expand their resources
How do you identify adaptive radiation?
- Recent common ancestry from a single specie (like finches and tortoise)
- Phenotype-environment correlation
- Rapid speciation
When does adaptive radiation occur?
When there was a mass extinction, or volcanic event, anything that technically reseats the diversity on the island, because there are a lot of niches there.
What did Darwin see in Australia?
Distinct flora and fauna with high ENDEMISM and unique adaptations
Biological uniqueness is a result of its long history of isolation from other masses
What was similar between islands and Australia?
Similar characteristics like Radiation, Endemism, unique adeptness
What is evidence from biogeography?
Geographically close organisms resemble each other
In convergent evolution, similar adaptations take place in different parts of the world to a similar environment.
Geographically isolated regions have very unusual animals
