Darwinian Paradigm

Question 1

Define common descent

Answer 1

All organisms/current forms have descended from common ancestor

Question 2

Define descent with modification

Answer 2

Species change over time giving rise to new species

Question 3

Define gradualism

Answer 3

The idea that evolution occurs over a long period of time

Question 4

Define natural selection

Answer 4

organisms with phenotypes better suited to their environment have a higher fitness/survival rate/leave more offspring

Question 5

Multiplication of species

Answer 5

Common descent & divergence lead to endless multiplication of species over time as new forms replace old ones, eventually becoming extinct

Question 6

Which of the 5 theories in Ernst Mayrs Darwinian Paradigm were key novel contributions by Darwin?

Answer 6

Common descent, gradualism

Question 7

What were pre Darwinism ideas for natural selection?

Answer 7

300BC Plato & Aristotle - Essentialism
The idea that every being had its own essence and unchanging characteristics. This essence distinguished it from other species

EU Scientific Evolution 1500s-1800s
Pierre Belon 1500s - Comparative anatomy - homology
Lamarckism - 1700s - Giraffes - spontaneous generation - no common ancestor
Erasmus - 7100s spontaneous generation but had common ancestor
Led to idea of ‘transmutation’
Led to Darwins theory

Question 8

what were the main criticisms of the ‘problem of inheritance’ and how was this dispelled in the 20th century?

Answer 8

The main criticism was that blending inheritance would not result in large variations in phylogeny but would resort back to a single variation over time/averaging out of every characteristic, meaning natural selection was not possible.
This was dispelled when mendelian genetics was introduced: the idea of discrete inheritance, where new variations were recoverable in later generations.

Question 9

what were the main criticisms of the gaps in the fossil record and how was this dispelled in the 20th century?

Answer 9

Darwins idea of gradualism made people think that there would be many fossils, especially showing intermediate forms. However this wasnt the case and there were many gaps.
It was realised in the 20th century that fossil samples that are adjacent in stratigraphy are generally seperated by tens of 1000s of years in time, more than enough for distinctive species to arrive. from this, palentologists no longer expect to find intermediate forms. gaps should be expected.

Question 10

what were the main criticisms of the age of the earth and how was this dispelled in the 20th century?

Answer 10

the estimates of the earths age at the time claimed by geologists were too young for gradualism to have resulted in the diversity shown today.
1930s - geology & fossils began to provide longer timeframe for history of earth.

Question 11

Define biological species concept and list pros and cons

Answer 11

-Defines species in terms of gene flow/exchange between populations. If individuals can breed and produce viable offspring and share genetic information, they are considered the same species. -If species cannot reproduce with other individuals it is an isolated species.
-Not useful in asexually producing organisms
-helpful for species that appear morphologically identical, eg Western and Eastern Meadowlarks

Question 12

Define phylogenetic species concept and list some pros and cons.

Answer 12

-species form one single branch on phylogenetic tree and have a MRCA.
-help when this genetic/fossil data is available
-however factors such as incomplete sorting, ancestral polymorphism could result in species being more closely related to other branches