Macroevolution Flashcards
What is the “study of layering rock”?
stratigraphy
Define “Lagerstätten”.
Sites with abundant supply of unusually well preserved fossils (often including soft tissues) from the same period of time
What is the Burgess Shale?
Lagerstätten in Canada that preserved fossils from Cambrian period
What are the 6 major provinces defined by Wallace?
- nearrctic
- neotropical
- Ethiopian
- palearctic
- oriental
- australian
Define vicariance.
Formation of geographic barriers to dispersal and gene flow, resulting in separation of once continuously distributed population (ex. mountains, rivers)
What is anagenesis?
whole sale transformation of lineage from one form to another; considered alternate to lineage splitting or speciation
What is cladogenesis?
an evolutionary splitting event where a parent species splits into two distinct species, forming a clade
What is the difference between anagenesis and cladogenesis?
Anagenesis is when one lineage turns into a new species, while cladogenesis is a parent species transforms into several new species, forming a distinct clade
What is stasis? Is it common?
Stasis is when there is little or no directional change for years in the fossil record and most lineages in the fossil record have experienced it
What occurs after a period of stasis?
There is a period of rapid change, which is often not seen in fossils
Define punctuated equilibria.
Most species undergo little change, but there are periods punctuated by brief periods of rapid morphological change (speciation)
Define phyletic gradualism.
Idea that new species arise through gradual transformation, and evolution has a constant rate
What is the difference between punctuated equilibria and phyletic gradualism?
Gradualism is selection and variation that happens more gradually. Over a short period of time it is hard to notice. In punctuated equilibrium, change comes in spurts. There is a period of very little change, and then one or a few huge changes occur
What is the equation for diversity change on a global scale?
D1 + originations - extinctions = D2
What are the two important factors that affect diversity through time?
Origination & extinction
Define turnover.
extinction/disappearance of some species and their replacement by others (known as origination)
Some species have ___ (high/low) turnover rates but strong overall clades.
high
Define standing diversity.
Number of species present in a particular area at a given time
What are challenges in using the fossil record to understand life’s origins?
- distinguishing species based on fossils
2. fossil record is not a complete picture of the past biodiversity
What are the three great evolutionary faunas?
Cambrian (trilobite), Paleozoic (brachiopod), Modern (mollusk) (these names refer to when faunas reach peak diversity)
What are the two theories on what causes the transition between fossil periods?
- It could be caused by new species evolving, or species going extinct.
- Could be caused by geological context of the fauna
What is one method to reconstruct the history of climates?
Can use chemistry of rocks, because the climate has fluctuated over time due to changes in carbon dioxide levels
What is the definition of adaptation radiations?
Evolutionary lineages that have undergone rapid diversification into a variety of lifestyles or ecological niches (ex. Hawaiian crickets)
When do adaptation radiations occur?
When clades evolve to occupy ecological niches in the absence of competition, and when big spaces in ecological niches occur due to extinction; also because new adaptations are shown to be key innovations that evolve to allow them to occupy habitats that were previously not possible
____ was the time when major taxonomic groups appeared for the 1st time in fossil record.
Cambrian Explosion
What occurred because of the Cambrian Explosion in the habitats and food webs of animals?
It expanded habitats for animals and spurred increased complexity of the food web.
What are possible causes of extinction?
mutation, genetic drift, natural disaster, killing them off, habitat loss, human actions
Define background extinction.
Normal rate of extinction for taxon or biota
What do clades do to survive background extinction?
Lineages branch to form new species at greater rate than background extinction rate
What is a mass extinction?
A statistically significant departure from background extinction rates that results in loss of taxonomic diversity; increases in extinction or decreases in origination
What is the biggest mass extinction?
Occurred at the boundary of Permian and Triassic periods
What were the 3 events that had high extinction rates?
End of the Ordovician, end of Permian, and end of Cretaceous
What are the 3 reasons for mass extinctions?
- sea level regressions & transgressions (rising & spreading of sea)
- climate
- biological causes – losing other species
- solar flares, supernovas, cosmic rays, etc.
What ended the Cretaceous period?
It ended because of the iridium object impact, which caused wildfires & dust obscuring the Sun
Why is today considered part of the 6th mass extinction?
The higher extinction rate, drop in diversity, causes by humans (exploitation, habitat loss, disease, air pollution)
What are complex adaptations?
Suites of coexpressed traits that experience selection for a common function
What makes phenotypes considered “complex”?
when influenced by environment and genetic factors, and when multiple components must be expressed together for a trait to function
What is a regulatory network?
systems of interacting genes, transcription factors, promoters, RNA, and other molecules
What are Hox genes?
Hox genes are a group of related genes that control the body plan of an embryo along the anterior-posterior (head-tail) axis; switches involved in specifying what appendage develops on a segment.
Define ortholog.
Homologous genes separated by speciation event
What is a paralog?
Homologous genes produced by gene duplication that are both possessed by same species
Natural selection often retools the form and function of characters within population, leading to complex adaptations far from perfect, but with fitness advantages
Statement
What is deep homology?
Condition that occurs when growth and development of straits in different lineages result from underlying genetic mechanisms that are inherited from a common ancestor; may help explain parallel evolution
What are fossils?
Remains or traces of once living organisms
What are conditions that usually prevent fossilization?
Scavengers, bacterial decay, dissolution in water, physical disturbance (wave action, wind)
What conditions promote fossilization?
rapid burial, anaerobic environments, protection from physical disturbance (quiet, deep water)
Most fossils are found in ___ rocks.
sedimentary
What are favorable environments that allow fossilization?
Oceans tend to collect the bulk of the sediments. Some locations include: continental slope, deep ocean core, ancient “core”, and deep lake sediments
What are the less favorable environments?
upland environments, continental deposits (sandbars and gravel pits)
What are ways that soft tissue is preserved in fossils?
rapid burial, anoxic conditions (avalanche of fine mud into deep water)
What are the 4 principles used for relative dating of sediments?
- superposition
- original horizontality
- lateral continuity
- cross-cutting
What is superposition?
It is when the youngest layer is on top
What is original horizontality?
When layers are first deposited horizontally and then may be deformed later
What is lateral continuity?
Layers of sediments are assumed to continue laterally over distances (within a region, not usually between continents)
What is cross-cutting?
geological bodies that are cut across other things are younger
Why are fossils used for biostratigraphic correlation?
It allows relative dating of fossils in different places, because different fossils occur in different layers of rock because biotas were different at different times
What types of rocks do we date using absolute dating techniques?
We use igneous rocks
How are sedimentary rocks dated?
Can use principles of stratigraphy to place fossils relative to dated rocks
Intrusions are ___ than host rocks.
younger
How was the geological time scale (GTS) derived?
from the spatial distribution of rocks and the vertical sequence of rocks & contained fossils
Know the GTS
Phanerozoic, the Eras & 4 critical periods (Cambrian, Permian, Devonian, Cretaceous)
What kind of fossils provide evidence of descent with modification?
transitional fossils
“Fossils inform biotic history”. What does this statement mean we can infer?
Extant species share a common ancestor in the past.
Fossils are critical in reconstructing ___ history and ancient ___.
climate history & ancient environments
What are two characteristics that fossils tell us about evolution?
The tempo (rate) and mode (pattern) of evolution
What are the 2 modes of evolution?
anagenesis (gradual change within a lineage) and cladogenesis (splitting of lineages)
Which is more common: stasis (punctuated equilibrium) or gradualism?
Lots of stasis, some gradualism
Look at fossil pattern…is it gradualism or stasis?
Powerpoint #2!
What are 2 hypotheses that explain stasis?
- constraint, or limits or biases in the generation of variation
- fluctuating selection, perhaps tracking a changing environment
What process adds originations?
speciation
Lineages survive only if ___ exceed ___. (originations, extinctions)
originations exceed extinctions
What is considered the cause for the Permian Event (extinction)?
Siberian volcanism, global warming, spread of deep marine anoxic waters, ocean acidification because of CO2 of volcano, volcano also releases methane
What is considered the cause for the Cretaceous Event?
Impact in Yucatan led to global cataclysm and caused rapid cooling
Why is it possible that because of the increase in CO2, we could be living through the 6th mass extinction?
Increased CO2 leads to warming, which leads to ocean acidification, and warming drives O2 out of upper ocean layers
What is novelty?
Qualitatively new structure with discontinuous origin making a relatively abrupt deviation from ancestral characters
What is one of the most important evolutionary innovations?
Jaws!
What are the 3 reasons why natural selection will occur?
- Individuals are variable in some traits
- At least some of this variation is heritable
- The variation causes differential survival and reproduction
Any phenotypic change is mediated through ___.
developmental processes
Are there some kinds of mutations that produce more significant, coordinated change? Can mutations be functional?
In some cases, mutations can be accommodated through processes inherent to development. Ex. muscles, nerves, & capillaries will automatically compensate for change in bone shape/size!
What is heterochrony?
Change in timing (ex. sexual maturation is accelerated because of a mutation); could explain the origin of vertebrates
If the Hox genes (regulatory genes) are the same in all animals, how is there such diversity?
same toolkit genes, expressed at different times, in different places, and different amounts during development, can yield very different morphologies
How do changes in the amount of expression of gene networks change animals?
It changes the amount of whatever the gene is controlling; ex. decreased expression = decreased limb length
