Lecture 24: Macroevolution part 1 Fossils Flashcards
What is macroevolution? (2)
a mix of diversification and extinction
What is a fossil
Any trace left by past organisms
Types of fossils (5)
1) Amber, freezing and natural mummies. Has the least altered remains but is rare
2) Permineralization and replacement. Where dissolved minerals replace origonals mineral content or precipitate in and around it, resulting in 3D details of internal and external structures. Ie typical dinosaur fossils
3) Molds and casts. where remains decay after being buried in sediment, they from unfilled spaces called molds. When new materials fill those spaces and harden into rock, they become casts
4) compression and impression fossils. When organic matter is buried in the sediment before it decomposes, the weight of the sediment leaves a 2D impression in the material bellow
5)Trace fossils. things like trackways and burros, prints etc
Fossilization depends on (3)
- Durability of specimen or protection: To prevent mechanical breakup from scavengers flooding and wave action
- burial: rapid burials provide the best defense against breakup and usually happen in water-saturated sediment
- Lack of oxygen: prevents decomposition from aerobic bacteria
Most common fossils (2)
-Marine bivalves (they have hard structures and are already buried
-Teeth
Biases in Fossil record (5)
- Habitat bias
2.Taxonomic bias
- Temporal bias
- Collection bias
- Geographic bias
Habitat bias
-Sedimentary deposits accumulate mostly in coastal marine areas composed of material eroded from landmasses, therefore fossil record is mostly made of marine organisms as they lived in the environments most favorable for fossilization.
Taxonomic bias
Bias towards organisms with mineralized structures (shells or bones), because they become fossils easier. Animal phyla without hard structures are under-represented. Additionally, critical plant parts like flowers can rarely become fossils
Temporal bias
Old rocks rarer than new rocks as mountains erode and tectonic plated subduct, meaning the fossil record is more faithful in recent fossils than old ones.
Collection bias
Certain types of fossils are preferentially collected ie dinosaurs vs fish and plants
Geographic bias
Most marine invertebrate fossils are collected in north America and Europe, meaning we know far more about those regions that others
Fossils and evolution (4)
-Fossils can tell us different information than DNA, but this info should be used complementary to DNA rather than without it
-Fossils give us morphological information, meaning its constrained to the morphospecies concept
-Because of this, convergence is difficult to recognize
-And its hard to distinguish between adults and young
Phanerozoic era (4)
-About the time jellyfish came into the picture up until when humans came into the picture
-Has three eras: Paleozoic (ancient life), Mesozoic (middle life) and Cenozoic (recent life)
-Within the cenozoic, there are three peroids: Paleogene, neogene and holocene
-Something they combine the paleogene and neogene peroids into a single peroid called the tertiary
Time scales (5)
eons are made up of eras, which are made of periods, which are made of epochs which are made of stages
Aquatic beginnings
-Fossil evidence dates photosynthetic micro-organisms similar to cyanobacteria 3300-3700 MYA
-These fossils are found in sedimentary deposits like cherts and shales
-These organisms are called Stromatolites
Stromatolites
-layered mats of algae and bacteria
-Likely contained the ancestors of cyanobacteria
-Evolution of photosynthesis may have paralleled increasing light exposure at the surface of the matts
Evolution of Algae (5)
-3700 MYA - earliest dated stromatolites
-3300 MYA earliest prokaryotes including photosynthesizers
-2100 MYA first eukaryotic organisms the Grypania (giant unicellular algae)
-1200 MYA first red algae the bangia
-800 MYA first green algae the cladophora
Dates for the eras
-Paleozoic ~543 -251 MYA
-Mesozoic ~251-65 MYA
-Cenozoic ~65 MYA to present
