Evolution

Question 1

Charles Darwin

Answer 1

British naturalist who conceived of the theory of evolution

Question 2

Theory of evolution

Answer 2

Explains how new species come into existence, adapt to environments, & why specific groups share specific traits

Question 3

Four basic principles of life

Answer 3

1. Heritable - a trait is part of organism’s genetic code and has chance to be copied to their offspring. Trait MUST be heritable to evolve.
2. Variation - In order for selection to occur, there must be variation in that trait in a population. Source of NEW heritable traits is Random Genetic Mutation.
3. Advantage - Organism’s traits affect how successfully they can survive & thus reproduce. Variation of trait MUST provide advantage (differential success) over other variations for evolution to occur.
4. Competition - Natural environments have limited resources. Competition for resources permits only some organisms to survive & reproduce. Some versions of a trait MUST be ‘selected out’ for evolution to occur & must occur cause of competition.

Question 4

When is it evolution?

Answer 4

When many new traits become widespread & organisms are so different from their ancestors that they constitute a new species. Does NOT require extinction of ancestors.

Question 5

Natural Selection

Answer 5

Competitive selective process by which detrimental traits are competitively discarded & advantageous traits are retained.

Question 6

How are organisms grouped together?

Answer 6

Based on their most recent shared common ancestor.

EX. all dinos are classified together because they evolved from single species of amniote tetrapods.

Question 7

Character

Answer 7

Any heritable trait that can be described & labeled.

Question 8

Shared Derived Character (AKA Synapomorphy)

Answer 8

Character present in two or more groups & their common ancestor, but not in any more distantly related groups.

Question 9

Convergent Evolution

Answer 9

Evolution of similar traits in two different lineages, usually due to adapting to similar environments & modes of life.

Question 10

Examples of convergent evolution

Answer 10

Spinosaurus & Ouranosaurus - both have sail, spino therapod & ourano iguanodont, spino has more synapomorphies w/ saurischians and ourano w/ ornithischians. So, most likely scenario is convergent evolution.

Wings of birds, bats & pterosaurs.

Question 11

Parsimony (AKA Occam’s Razor)

Answer 11

All things being equal, the simplest answer is usually the right one.

Question 12

Character Matrix

Answer 12

List of characters a specimen has that is compiled by the researcher & given to a computer program to apply Parsimony & classify the specimen.

Question 13

Phylogenetic Trees

Answer 13

Resulting arrangements of computer programs. Look like diagrams of a ‘family tree’. Composed of nodes & branches.

Question 14

Nodes

Answer 14

Where two branches diverge, shows the point at which the two lineages shared a common ancestor.

Question 15

Branches

Answer 15

Show how descendants of shared common ancestors continued to diverge from eachother.

Question 16

Clade

Answer 16

A group of species that share a common node.

Can be very small (two species) or very large. Must contain the ancestor & ALL its descendants.’

Question 17

“Missing Links”

Answer 17

Organisms that show an evolutionary connection b/w two major groups of organisms by displaying some traits that are characteristic of one group & some traits that are characteristic of the other group.

Question 18

Thomas Henry Huxley

Answer 18

Colleague of Darwin & earliest advocate for theory of evolution.

First scientist to recognize birds evolved from dinos, citing Archaeopteryx as the ‘missing link’.

Question 19

Archaeopteryx

Answer 19

Exquisitely preserved in fossil deposits.

Long wing feathers & tail feathers like birds. Teeth, clawed fingers, & long series of tail vertebrae like dinosaurs.

Huxley showed transitional forms DO exist in the fossil record & birds are branch of dino family tree.

Question 20

Post Huxley Discoveries linking dinos and birds

Answer 20

Increasing # of characters that birds & other therapods share.

Sinosaurospteryx - first non-avian dino to be discovered with feathers. Used for insulation, not flight.

Yutyrannus - Large tyrannosaurid, showing that some large dinosaurs had feathers as well.

Question 21

Line between dinos and birds

Answer 21

Blurry AF! Lots of dino-like birds and bird-like dinos.

Question 22

How do we define birds?

Answer 22

Aves - Crown group of birds, includes all living as well as extinct taxa.

Avialae - ‘flying dinosaurs’, includes extinct species that looked very similar to modern birds (archaeopteryx).

Question 23

4 main definitions of birds & their issues

Answer 23

1. Archaeopteryx & all its descendants - Problem; New phylogenetic analyses show that Archaeopteryx was more closely related to dromaeosaurid theropods than modern birds.
2. Feathered Dinos - Problem; Many feathered dinos (like Yutyrannus) are found & added to this definition, meaning even Tyrannosaurs would be birds.
3. Flying Dinos - Problem; Difficult to determine which dinos were capable of flying (as opposed to gliding).
4. Crown Dinos (i.e. last common ancestor of all extant birds & their descendants). - Problem; fails to recognize many feathered & flying dinos more closely related to birds than to archaeopteryx.

Question 24

Which bird definition is favoured by Paleontologists

Answer 24

Crown Dinos - use Avialae for clade containing Archaeopteryx & its descendants.