Chapter 27 Flashcards
commonalities
- Phylogeny
- branch
- node
- tip
- outgroup
Phylogeny
evolutionary history of a group of organisms
Branch
population through time
Node
fork in the tree
represent a split where the two groups differ for some reason
Tip (terminal node)
end of a branch
Outgroup
a taxon closely related to a monophyletic group but not a part of it
Topologies
branching patterns
Trees are organized according to …
evolutionary history
Principle of parsimony
Phenetic
genetic distance
the computer estimates the differences in data between animals and places them in areas with the closer relatives
Cladistics
shared derived characteristics
Ancestral traits: existed in the ancestor
Derived traits: is a modified version of the ancestral trait
Each clade is determined by synapomorphy
Homology
traits are similar because of a shared ancestry
Convergent evolution or Homoplasy
traits are similar but there is no common ancestry (convergent evolution)
Sine genes
short interspersed nuclear evidence
Synapmorphy
shared derived trait that is present in the recent ancestor and lacking in the ancestral
Fossils
After burial
Decomposition doesn’t happen-preservation
Sediments make pressure-flat fossil
Decomposition slowly- Casts
Decomposition very slowly – premineralized fossil
Limitatons of studying the fossil record
Area of active deposition
Slow decomposition (ie. hard parts)
Tectonic movement
Natural disasters
Three eons
Hadeon, Archeon, Proterozoic
Precambrian
Beginning of the universe to 542 MYA
The solar system came into existence
Earth, land, oceans,
photosynthetic cells, eukaryotes,
red algae, lichens, sponges,
ocean oxygenated, first bilateral
Three eras
Paleozoic, Mesozoic, Cenozoic
Phenerozoic eon
542 MYA-present
Five major extinctions,
This is where oxygen became common
Multicellular organisms occurred
Paleozoic
initial diversification of animals
Mesozoic
dinosaurs and gymnosperms
Gymnosperms: seeds no flowers
Angiosperms: seeds within ovaries, flowering
Cenozoic
Angiosperms and mammals
Paleontologist focuses
Extinctions
New species and quick diversifications
Extinctions
60% of species are dead in 1 million years
We are in a possible sixth
Five main ones have definitely occurred
Background extinction
populations are at zero for normal environmental changes
Mass extinctions
sudden, temporary, large events cause animal dieoff
End Permian extinction
251 MYA
Nearly 60% families died out
Considered one of the worst
End Permian extinction
causes:
- increase in CO2, heat and SO2 leading to global warming and sulfuric acid in atmosphere,
- ocean was anoxic,
- sea level drop
- High CO2 and low O2 lead to low atmosphere places being the only livable areas
End Cretateous extinction
65 MYA
Caused by a large impact of a asteroid
Caused 60-80% of multicellular organism death
End Cretateous extinction evidence
Soot and ash
Tsunami
Sulfuric acid in water and air
Fireball of hot gases would make fires
Selectivity
Each extinction doesn’t quite kill everything
End Cretaceous:
dinosaurs pterosaurs, large marine reptiles died
Turtles, mammals, crocodiles, and amphibians survived
Why?
Hibernation, size, food availability
Recovery
Diversity from simplification
Adaptive radiation
Empty niches
The genes that survived got to reproduce (limitations of evolution)
Adaptive radiations
Single lineage produces multiple descendant species in multiple habitats with multiple resources
Adaptive radiations triggered by:
New resources
New ways to exploit resources
Cambrian explosion
565 MYA-505 MYA every major group of animals appears
Before this sponges and bacteria were the main life forms
Cambrian explosion
Why?
High oxygen levels
Predation occurred
Predator prey arms race
Movement into new niches: ocean floor-ocean-lakes and rivers-coast-land-mountains
Mutations increase # Hox genes
Hox genes are the genes that control embryotic development
