Lecture 11 - Macroevolution Flashcards
What is irreducible complexity?
- a system composed of several parts that all contribute to a function
- removal of any part causes the system to cease functioning
What is the rebuttal to irreducible complexity?
- pieces of complex systems often have functions of their own
- “making a simpler mouse trap”
What is an example of a rebuttal against reducible complexity argument?
- bacterial flagellum (basal body)
- made of parts that could serve other functions
- can function if parts are missing
What is another example against reducible complexity?
-eyes
What does “the evolution of new species is rarely if ever observed” mean as a critique of evolution?
-we never see it happen
What are 2 major rebuttals against the claim that new species are never observed?
- too little of time to observe origin of new species (<0.0066% of biological history)
- we HAVE observed origin of new species
(in lab, polyploidization, naturally without polyploidization)
What is punctuated equilibrium?
- periods of evolutionary stasis interspersed by major change
- (nothing, then sudden change)
punctuated equilibrium is not explained by ___________
Darwinian Theory
What did Darwin’s theory believe in instead of punctuated equilibrium?
gradualism
What are 3 rebuttals to punctuated equilibrium?
- punctuations that appear abrupt in fossil record may take tens of thousands of years
- periods of apparent stasis may fail to give a true impression of biochemical changes not detectable in fossil record
- slight genetic changes may result in phenotypic changes
Sometimes changes at a single ______ can cause _______
gene, speciation
In many cases, what is the origin of large phenotypic changes?
evolution of genes controlling development (evo-devo)
What is heterochrony?
changes in rate and timing
What does heterchrony include?
- changes in relative growth rates of different body parts (allometry)
- changes in timing of reproductive vs. somatic development
What does relatively rapid reproductive growth result in?
paedomorphosis
What is paedomorphosis?
sexually mature adults with juvenile morphology
What is allometry?
changes in relative growth rates of different body parts
Changes is allometric growth lead to differences between what 2 species?
human and chimp adult skulls
What is an example of a paedomorphic pet? What are its qualities?
- dogs
- relative to ancestral wolves domesticated dogs have:
1. softer fur
2. larger head/eyes
3. droopier ears
4. more submissive behavior
5. shorter muzzle
Alteration in ______ controlling the placement and organization of _____ _______ cause major _______ change
genes, body parts, evolutionary
what are homeotic genes?
genes that control body plans
How do homeotic genes work?
They control the developmental fate of groups of cells
What are Hox genes? What do they provide?
- products of one class of homeotic genes
- positional information in animal embryos
What is an example of Hox genes controlling evolution?
- fish fins to tetrapod limbs
- suppresses leg formation in insects but not crustaceans
What are 5 hallmarks of macroevolution?
- evolution is not goal oriented
- evolution is not a ladder from simple to complex
- novel features often arise through intermediate stages (each serving a function)
- evolution recycles features and put them to new uses
- evolution leaves baggage behind
What does it mean that evolution is not goal oriented?
- mutations are random
- selection “chooses” mutations that increase reproduction/survival
- evolution gropes blindly in many directions at once
What was the old view of evolution? Ladder or tree?
ladder from one-hole to two-holes
What was one of the first organisms that was discovered having a complex digestive system?
ctenphora
All organisms evolved from a ______ _________
common ancestor
What is an example of novel features arising through intermediate stages?
partial wings (they can be adaptive)
What is an exaptation?
many characters evolved for purposes other than those for which they are currently used
What are 3 examples of exaptation?
- feathers evolved for insulation, co-opted for flight
- protein used for cell adhesion in multicellular organisms first evolved in singled celled choanocytes
- ancient angae had genes for survival on land before they left for water and colonized land
What are 3 examples of human evolutionary baggage?
- appendix
- trachea
- blind spot
What are the 3 major criticisms of macroevolution?
- irreducible complexity
- no observations of speciation
- punctuated equilibrium inconsistent with Darwin
What are the 2 roles of “evo-devo” in driving large changes?
- changes in rate and timing
2. changes in spatial pattern
