Macro Evolution (8) Flashcards
Macro evolution?
= large-scale evolutionary changes that take place over long periods of time.
Evidence for Macro evolution?
Fossil evidence.
What do we use to figure out the relationship between micro evolution & macro evolution?
We use genotypes & phenotypes.
SA’s Biodiversity THEN & NOW?
● THEN = Gorgonopsians, Dracovenators, Sauropods, Saber-toothed cat, etc.
● NOW = We have Mega-herbivores & mega-carnivores that have similar guilds to organisms in the past.
Describe Earth’s biodiversity?
Not constant as organisms change every time there’s mass extinctions/extinction events.
What do mass extinctions do to Earth’s biodiversity?
They limit Earth’s biodiversity by resetting the evolutionary clock.
Extinction?
= event where species die out/die and are nolonger existent.
Extinction types? (2)
• Background extinction (BRE).
• Mass extinction (ME).
BRE?
= involves the notion that if taxa didn’t go extinct Earth would be overrun & we wouldn’t have anywhere to left to stand.
What is BRE measured in?
Million species-years.
Million species years?
= number of extinctions expected per 10000 species per 100 years.
What is BRE measured over?
Measured over a time frame for a specific group.
Human lineage period?
0.5 million to 5 million years.
Average extinction rate for mammals?
2 species per million species-years.
What explains the BRE?
Red Queen Hypothesis (RQ).
RQ?
= states that an organism has to keep “running to stay in the same place”, i.e., to remain extant/survive.
Main takeaway from RQ?
Organisms compete & drive each other to extinction.
Results of RQ? (2)
• BRE rate that is non-zero.
• Constant extinction rates.
What happens when extinction rates > BRE rate?
6th extinction.
What is extinction rate measured by?
Measured by the no. of extinctions per million species-years.
How many current species of mammals?
5500.
Criteria for Mass Extinction? (2)
• ER > BRE.
• Short temporal duration.
ME Types? (5)
• Ordovician.
• End-Devonian.
• Permo-Triassic.
• End-Triassic.
• End-Cretaceous.
How did some organisms make it through/survive mass extinctions?
Through burrowing.
What do we call the effect that enabled organisms to survive ME?
Bottleneck effect.
When was Earth’s greatest biodiversity?
What would you predict from an evolutionary tree?
What is the Null hypothesis in terms of biodiversity over time?
= diversity should increase over time.
Exponential model attributes? (3)
• Implies constraint on speciation.
• No extinction considered.
• Low carrying capacity.
Constrained model attributes? (3)
• Implies constraint on speciation.
• Extinctions considered.
• High carrying capacity.
BRE 2?
= number of extinctions per million species years.
Place to study adaptive radiations?
Hawaiian islands.
Why are these islands the best places to study adaptive radiations? (3)
• Have a great time series.
• Help us observe what happens after “extinctions”.
• Surprising model for extinctions.
Egs of adaptive behaviour? (2)
• Hawaiian Silverswords.
• African Cichlids.
Types of evolutionary rates? (2)
• Diversification rates (DR).
• Phenotypic/Molecular change rates (PMR).
DR?
= represented on phylogenetic trees by high branch length density.
What is DR measured in?
number of lineages per million-years.
Short branch length?
= high diversification rates.
PMR?
= trait change over an amount of time.
How can one detect trait change over time?
By comparing the extant to the extinct.
Eg of high PMR?
Dinosaurs.
Eg of low PMR?
Horseshoe crab.
High DR + High PMR =?
High DR + High PMR = AR.
Circumstances enabling AR/ AR Criteria? (4)
• No competitors.
• Competitors die.
• Competitor replacement.
• Key innovations.
What to use/do when figuring out why an AR occurred for that species?
Look to AR criteria.
Key innovation?
= a structure that helps you exploit a newly available ecological niches.
What does a key innovation do?
Helps a species diversify.
Egs of key innovations? (2)
• Birds.
• Dolphins.
Key innovation in Birds?
Changes in the Pygostylia/Hindlimb shape & not powered flight.
Key innovation in Dolphins?
Echolocation.
Common factor in AR?
Convergent evolution.
Why is convergent evolution a factor in AR?
It occurs as a consequence of similar ecological pressures through physical world constraints.
Egs of physical constraints? (3)
• Temperature.
• Geography.
• Water.
Explain water as a physical constraint?
Water remaining the same all these years as it has enabled basal “fish”, basal “reptile”, varanid lizard, crocodilians and mammals to exist even if they are of different taxa but have similar phenotypes.
Physical constraints for Cichlids? (4)
• Water/Lake depth.
• Sand (burrowing).
• Dietary pattern.
• Freshwater.
Important physical constraints in Cichlids? (2)
• Dietary pattern.
• Body shape.
2 important MEs?
• Permo-Triassic.
• End-Triassic.
Exponential models graph description? (2)
• Exponential increase.
• Waves/Water waves increase.
Constrained models graph description? (2)
• Exponential decrease.
• Hills graph/fingers graph (up down up down).
Promoters of AR? (3)
• Key innovations.
• Niche vacancy.
• Incumbent advantage/Current advantage.
AR?
= the evolution of many diverse species from a common ancestor as they fill different ecological niches.
Ordovician?
= most invertebrates died.
End-Devonian?
= amphibians & invertebrates died.
Cretaceous?
= all dinosaurs died.
Anapsid?
= modern animals with no openings behind the eye.
Synapsid?
= modern animals with 1 opening behind the eye.
Diapsid?
= modern animals with 2 openings behind the eye.
Eg of anapsid?
Tortoises.
Egs of synapsids? (2)
• Mammals.
• Mammals ancestors.
Egs of diapsids? (5)
• Dinosaurs.
• Lizards.
• Snakes.
• Crocodiles.
• Birds.
Evidence of diapsids?
Dinosaur eggs discovered in Eastern Free State.
Most distant ancestor of tortoises?
Eunotosaurus.
Distant ancestor of dinosaurs & crocodiles?
Proterosuchus.
Synapsids groups? (3)
• Pelycosaurs.
• Therapsids.
• Mammals.
Mammal-like reptiles in SA? (2)
• Pelycosaurs.
• Therapsids.
Discovery of mammals?
Karoo, SA.
Oldest mammal in the world?
Megazostrodon.
Where was the evidence of human technology found?
South Africa.
Human technology includes? (3)
• Fire use.
• Tools.
• Art.
Highly specialized species disadvantage/risk?
High vulnerability to extinction.
Highly specialized species eg?
Humans.
1st & oldest Multicellular microorganism?
Otavia.
1st four-legged organism?
Tutucias.
Difference between reptile & mammal?
Mammals have a hard palate, while reptiles do not have a hard palate.
Outline the “Timeline”?
Single-celled algae.
|
Multicellular organisms.
|
Fishes.
|
Amphibians.
|
Reptiles (anapsids, synapsids, diapsids).
|
Mammals.
Human discoveries from SA? (5)
• Taung child.
• Mrs Ples.
• Little foot.
• Australopithecus sediba.
• Homo naledi.
Macroevolution attributes? (4)
• Evolution above the species level.
• Occurs on geological timescales.
• Sums of lots of microevolution.
• Extinctions are major parts of it.
Macroevolutionary patterns? (3)
• Stasis.
• Adaptive radiation.
• Extinction.
Pharenozoic era?
= a time of invertebrate life forms where processes such as continental drift & continental glaciation, and the Cambrian explosion occurred.
Patterns of macroevolution observed in plants? (2)
• More higher orders of plants emerged.
• Increased photosynthetic capacity.
Eg of organisms that are perfect for understanding macroevolution?
Bivalves.
Rates of evolution/Kinds of rates of evolution? (2)
• Phylogenetic rates.
• Taxonomic rates.
Phylogenetic rates?
= rates at which characters/character complexes evolve.
Taxonomic rates?
= rates at which taxa with different traits originate & go extinct.
Difference between Taxonomic & Phylogenetic rates?
● Phylogenetic rates = rates at which characters evolve.
● Taxonomic rates = rates at which taxa with different traits originate & go extinct.
Important thing to note in macroevolution?
Timescale.
Stasis?
= a block of little or no evolutionary change in a species.
Rates of character evolution is explained by?
Punctuated equilibrium.
Why couldn’t Gould & Eldridge use the punctuated equilibrium to explain the pattern of stasis & rapid bursts of evolution?
It’s because the data they had didn’t support the punctuated equilibrium.
Questions to ask regarding Rate of character evolution: Stasis? (2)
• Why is evolution so slow?
• Why do some traits remain the same over such large timespans?
What organism was stasis tested with & what was the result?
Bivalaves
• 24 characters of 19 lineages compared through time were found to be remarkably similar.
List of hypotheses accounting for stasis? (3)
• Internal/Genetic constraints.
• Stabilizing selection for constant optimum phenotype.
• Ephemeral local divergence.
What do we mean by the hypothesis of Internal/Genetic constraints account for stasis?
We mean that the organism has o internal/genetic requirements to enable it to survive & remain in the environment they’re in.
Eg of hypothesis 2 to account for stasis?
Glaciers in the Northern hemisphere.
What does hypothesis 2 of accounting for stasis involve?
Habitat tracking.
Habitat tracking?
= where when environmental conditions change & some populations follow their preferred habitat instead of adapting to the new conditions.
Explain hypothesis 3 that accounts for stasis?
How does hypothesis 3 account for stasis?
Egs of how long-term evolutionary change is more likely to happen in stable environments? (2)
• Cape Floristic region.
• Drakensberg region.
In what type of environments is long-term evolutionary change likely to occur?
In stable environments.
Phylogenetic conservatism?
= trait that hasn’t changed over multiple group of families.
Eg of Phylogenetic conservatism?
Mammals (synapomorphies of large groups).
Phylogenetic conservatism attributes? (2)
• Presence of living fossils.
• Traits remain the same over millions of years.
Why would there be so little change?
Consider stabilizing selection & niche conservatism.
Niche conservatism?
= how an organism is engaging with the environment which might keep them where it is.
Limitations on variations? (3)
• Not all features are equally variable.
• Some traits display little phenotypic variation despite underlying genetic variation.
• Hsp90 in Drosophila.
Eg of Limitations on variations?
Drosophila.
Kinds of Evolution of novelty? (5)
• Features originate as new structures.
• Developmental by-products.
• Ancestral function that becomes accentuated.
• Decoupling of multiple functions
• Duplication with divergence.
Eg of Evolution of novelty 1?
Titanotheres.
Eg of Evolution of novelty 2?
Acid sequestration in Butterflies.
Eg of Evolution of novelty 3?
Eg of Evolution of novelty 4?
Salamander tongues.
Eg of Evolution of novelty 5?
Teeth.
Complex characteristics?
= where complex traits arise from “simple” traits & can integrate other structures.
Law that explains complex characteristics?
Dollo’s law.
Dollo’s law?
= states that complex characters are seldom regained if lost.
Eg of complex characteristics?
Eyes.
How are eyes an eg of a complex characteristic? (2)
• We see lots of incremental changes (in each component).
• Co-opting among the different components occurs.
Ho in terms of biodiversity?
Ho: Diversity should increase over time.
How do we estimate biodiversity? (3)
• Count species (or higher order taxa).
• Fossils.
• “Pull of the Recent”.
How do fossils help us estimate biodiversity? (2)
• Offer useful temporal information.
• Offer information on when species originated & went extinct.
“Pull of the Recent”?
=
How do we use “Pull of the Recent” to estimate biodiversity?
Predictions/Models of biodiversity over time? (2)
• Exponential model.
• Constrained model.
Biodiversity during the Pharenozoic era observations? (2)
• All genera vs Well-resolved genera.
• Biodiversity is steadily/gradually increasing.
Well-resolved genera role?
Give an accurate picture of what biodiversity looks like.
Exponential model of biodiversity?
= exponential model without extinction.
Constrained model of biodiversity?
= exponential model with extinction.
Thing to consider in Constrained model of biodiversity?
Organisms expand to fill niches & use resources as much as they can (carrying capacity).
Fossil evidence attributes? (3)
• Important for macroevolution.
• Best evidence for macroevolution.
• Helps us understand how phenotypes have changed through time.
Why
• Earth’s biodiversity isn’t constant.
• Effect of mass extinctions.
How do we know that Earth’s biodiversity is not constant?
Through observation of the rates of origination & extinction.
Rates of origination & extinction attributes? (2)
• Show change over time.
• Adapt population growth models.
Types of rates regarding biodiversity? (2)
• Rates of origination.
• Rates of extinction.
Rates of origination (RE)?
= how often species are arising/emerging.
Rates of extinction (RE)?
= how fast animals/species are dying out.
High RO + High RE =…?
High RO + High RE = High Turnover.
Drivers of RO & RE? (3)
• Degree of specialization.
• Population dynamics.
• Geographic ranges.
What do we mean by “Degree of specialization”?
We mean how specialized/the extent of specialization of an organism.
What do we mean by “Population dynamics”?
We deal with competition (either due to co-evolution or extinction) & adaptation experienced by an organism.
What do we mean by “Geographic ranges”?
We mean how far your geographic area spans (small or large areas).
Result of geographic ranges?
Narrow geographic range, More chances of going extinct.
Extinction attributes? (3)
• Likened to hitting reset.
• Major determining factor in biodiversity.
• Non-random.
The 2 ME types that we focus on?
• Permo-Triassic.
• End-Triassic.
Permo-Triassic attributes? (4)
• Diversification of amniotes, turtles & mammals.
• Major extinction.
• Bottom of food chain, particularly calcareous organisms are decimated.
• Animals that survival were found in burrows.
Permo-Triassic?
= period when it was cool, but warming up with the presence of ice caps.
Place where the turnover of the Permo-Triassic can be observed/identified?
Valley of Desolation in the Karoo.
Cause of Permo-Triassic?
Siberian traps (flood basalts) where there was heavy ocean acidification.
End-Triassic?
= period where it was much hotter without the presence of ice caps.
End-Triassic is AKA?
End of Life Part II.
Cause of End-Triassic?
Volcanism.
How did Volcanism cause End-Triassic?
As Pangaea starts to break up, the proto-Atlantic ocean begins to lift, leading to flood basalt deposition in the Central Atlantic Magnetic Province (CAMP).
End-Triassic attributes? (3)
• High Archosaur diversity before extinction event.
• Diapsids, particularly Archosaurs, don’t make it through/don’t survive.
• Dinosaurs take over after extinction event
Place where the turnover of the End-Triassic can be observed/identified?
Golden Gate National Park.
Eg of extinction in plants?
Large-leafed & Small-leafed plants.
Attributes on plants being an eg of extinction? (6)
• Small populations.
• Slow reproductive rate.
• Poor dispersal.
• Carnivory vs Herbivory.
• Ecology.
• Narrow range.
Explain the attributes on plants being an eg of extinction?
These attributes make such plants specialized in a sense, which increase their chances of going extinct.
Explain AR Criteria 1?
Establishing in a new area.
Explain AR Criteria 2?
Competitors die due to extinctions (RQ or otherwise).
Explain AR Criteria 3?
Where one taxon is just that much better.
Explain AR Criteria 4?
Where you have adaptive breakthroughs.
What do ARs depend on? (2)
• High rates of speciation.
• High rates of phenotypic change.
Things that promote ARs? (3)
• Key innovations.
• Incumbent advantage.
• Niche vacancy.
Macroevolution constraint?
Physics of the natural world (Niche similarities).
Results of macroevolution constraints? (2)
• Produces convergence.
• Similarity in form that’s not due to phylogeny.
Thing to note regarding microevolution & macroevolution? How are they connected?
Microevolutionary processes lead to macroevolutionary patterns.
AR attributes? (3)
• Short early branches.
• Long later branches.
• Understood through evolutionary rates.
What do we mean by “similar guilds”?
We mean that the Mega-herbivores & mega-carnivores of today have similar requirements and play similar roles within a community to Mega-herbivores & mega-carnivores in the past.
