Evolution (PP16) Flashcards
What is evolution and what does it involve>
Evolution is the heritable change in characteristics within populations over the span of multiple generations
It involves the non-random selection of random variation resulting in the development & diversification of life
Does evolution increase or decrease with time?
This diversity tends to increase with time
What is variation caused by?
Mutation
How does a mutation arise??
Note: mutations are constantly arising due to small errors in the replication process – each generation is slightly different from the previous
do mutations have affect on phenotype?
Mutations are random, and may have small, large, or no effect on phenotype
who do you associate with catastrophism
george cuvier
Who is georges cuvier?
French scientist who helped develop the field of paleontology
what are fossils are where can they be found
Fossils = preserved remains, imprints, or traces of organisms
Can be found in sedimentary rock (in layers / strata)
did georges cuvier believe in catastrophism or gradualism
catastrophism
What does each stratum represent
Each stratum represents a different catastrophe
What is catastrophism
Species had all been wiped out by violent catastrophes. Changes did not arise slowly but through chaotic processes
What is catastrophism opposed to?
Gradualism
what is gradualism
the theory that Major changes can take place through the cumulative effect of slow but continuous processes
who do you associate with gradualism and what did they postulate ?
Hutton & Lyell (geologists) postulated that changes in the Earth’s surface might result from slow, continuous actions (still operating today)
what did lyell believe
Lyell: rate of geological processes have not changed throughout history (the world is old)
what did hutton believe
Hutton: canyons formed from rivers (proposed gradualism)
what are the aspects of the lamarkian theory of evolution
Hypothesized that species evolve through use / disuse & inheritance of acquired traits
CHOOSE WHICH TRAITS GET PASSED ON
why did the lamarkian theory not pass
Proposed mechanisms unsupported by evidence
We do not change by striving
What are the aspects of the darwinian theory of evolution
Hypothesized that species evolve through the mechanism of natural selection, resulting in increased diversity
what is thee process of darwinians theory of evolution
Process:
Genes mutate
Individuals undergo selection
Populations evolve
who was the other scientist with the same theory as Darwin
Wallace
What was Darwins journey called and what was its purpose
Voyage of the Beagle (1831-1836) to survey life’s “endless forms most beautiful”
where did Darwin go and what animals did he observe ?
Travelled to the (geologically new) Galapagos Islands (amongst other locales)
Observed slight variation in phenotypes of finches, mockingbirds, & tortoises by island
what did darwin refer evolution as?
descent with modification”
what book did darwin publish
ON the origin of species
explain diversity and unity
Diversity: conceived of natural history as a branching tree
Unity: similarities between living organisms attributable to descent from a common ancestor
Darwin talked about inheritance but…
He Did not yet understand the genetic mechanisms
Was darwins work always accepted?
Work was not widely accepted until 20th century
e.g. Scopes Monkey Trial of 1925 (the State of Tennessee v. John Thomas Scopes)
what do the root, branches and tips represent in a phylogenetic tree
Root: distant ancestor
Branches: divergence of species
Highest tips: living species
What was the first evolution observation
Populations have capacity to produce more offspring than actually survive (if all survived, population would increase exponentially)
But populations tend to be stable (face limited resources & predators) LOOK AT GRAPH ON SLIDES
what was the second evolution observation>
Variation exists within a population
These different traits are heritable
Some traits are beneficial & improve the likelihood that an individual will survive & reproduce
what was the first evolution inference
Individuals who inherit traits that grant a higher probability of surviving & reproducing will have more offspring (they are more ‘fit’)
what does it mean when an organism is “fit”
when an organism inherist traits that grant a higher probability of surviving & reproducing will have more offspring
what was the second evolution inference
Differences in reproductive success will result in accumulation of favourable traits (favourable alleles) in the population (over the span of several generations)
what did darwin lack
an understanding of inheritance to explain how variation might arise & be transmitted
Still considered the trait blending hypothesis to be true
what did mendel do to help darwins theory
Proposed a model of inheritance (discrete heritable units = genes)
what is the unit of evolution
population
what is the most important mechanism for adaptive evolution
natural selection
what does gradualism explain
Gradualism explains big changes as the accumulation of many smaller changes over long time periods
what are the 4 pieces of evidence for evolution
- Paleontology (fossil record)
- Biogeography
- Comparative anatomy (homology, embryology)
- Molecular evidence
what are the issues with the fossil record
- Soft tissues do not fossilize
- Soft-bodied organisms are not well represented
- Can only examine certain parts of organisms (skeletal structure & other hard tissues)
- Relatively few individuals are actually fossilized
what does the fossil record allow us to do
examine long-extinct species
How can you separate fossils by era?
By the Stratification of rock layers allows us to separate fossils by era
What can you see through the fossil record and what can it piece togethere
See incredible diversity, but also ‘transitional’ forms (succession of forms) in layers where they are expected to be found
Can piece together a roadmap of descent & dead ends
what are the two types of dating methods?
Relative dating
Radiometric dating (absolute)
explain relative dating
Relative dating
Use position of fossils in sedimentary rock layers (strata)
The deeper the fossil, the older it is
Not exact, & issues of disturbance
explain carbon dating
Radiometric dating (absolute)
Use of unstable radioactive isotopes with known half-lives (radioactive decay)
After 1 half life, half of the atoms have become stable decay products
Can compare amount of isotope vs. decay product to determine age
the deeper the fossil…
the older it is
explain carbon dating
Use radioactive 14C isotope (forms stable 14N)
Same ratio of 14C:12C in a living organism as in the atmosphere
Can trace through CO2 incorporated into the organism (dead organisms don’t respire)
Over time, 14C:12C ratio will decrease
Works for organic samples younger than ~75,000 years old
carbon dating uses what isotope
Radioactive 14C isotope to form stable 14N
what is the issue with carbon dating
only works for samples younger than 75000 years old
explain potassium-argon dating
Use radioactive 40K isotope (forms stable 40Ar)
Rocks will retain 40K isotope once they solidify from their molten state (gives the time of their formation)
Works for mineral & glass samples between 1,000 years old & a billion years old
what isotope does potassium argon use
Radioactive 40K isotope (forms stable 40Ar)
what is biogeography
Study of the geographic distribution of organisms
do organisms fill every enrvironmeent that could accommodate them? explain
NOO
each species has a unique geographical origin, though some may have dispersed
Each major geographical area has its own distinct flora & fauna
each major geographical area has its own distinct….
flora and fauna
Explain why animals in different places from different ancestors have analogous structures
because Some similar animals that have adapted to similar environments have evolved independently from different ancestors – analogous structures
What explains why some organisms on certain continents are related to/ressemble organisms on different continents?
Continental drift & the presence of land bridges helps
what is homology
Homology = similarities between organisms due to a common (shared) ancestor
how do homologous structures evolve
evolved through adaptive radiation (diversified into new forms from a common ancestor)
explain adaptive radiation
Organisms diversied but have Homologous structures because they come from from a common ancestor)
ORGANISMS WITH SHARED ORIGIN
give examples of homologous structures
Bat wing, whale fin, & human arm
Reptile eye & mammal eye
explain how analogous structures come about
They have Structural similarities are due to a similar environment / function
BECause of Convergent evolution (independent origin)
explain convergent evolution
organisms can have similar/analougous structures because they evolved in similar environments
give examples of analogous structures
Butterfly wing & bird/bat wing
Octopus eye & human eye
What does vestigial mean
reduced / degenerate / remnant)
why do some structures become vestigial
They are not needed, and there is nothing preventing the genes that make them from being lost, so these structures can be lost too
give an example of.a structure becoming vestigial
Snakes no longer have limbs (they once did), though they still have remnants of the pelvic girdle (from which the legs would have grown)
what does Ontology recapitulates phylogeny mean
it means development reveals evolutionary history)
During development, can embryos show certain traits / structures at certain points that do not appear in the fully developed organism?
YES
why are some ancestral genes quickly silenced in development
Some ancestral genes are quickly silenced (turned off) to prevent those structures from fully developing
true or false:Embryos of many different species appear very similar at certain points during their development
true
give an example of ancestral traits devceloppign and being silenced
human embryos go through a stage where they briefly form the start of gills (fish-like), and a stage where the bud of a tail is transiently seen (tadpole-like)
Are many genes conserved (shared) between different organisms, though there might be differences in their sequence?
Yes
The more distantly related the species…
the more differences in the sequence
do proteins involved in similar processes have homologous sequences? what does this suggest
yes, it suggests that these proteins had a common origin)
TRUE OR FALSE: Not All organisms use DNA with the same 4 bases and the amino acid code is not shared by all organisms
false
genes are conserved but what might change about them
how and when they function might change
is evolution directed? why or why not
NO
There is no aim or ultimate goal, no final destination – it is not teleological
Does not necessarily lead to greater complexity
true or false: evolution maximizes fitness?
false
Evolution does not care about making a “perfect” organism (because it doesn’t care about anything)
It’s all about what works well enough to survive & propagate
What doesn’t work well enough or what isn’t useful is selected out (if there’s strong enough selective pressure)
what will decide the prevalence of a trait>
the strength of the selective pressure
is evolution always conspicuous? explain
Evolutionary changes / adaptation arise over multiple generations
no
Small inherited changes may not be easily seen
Not all changes are useful / beneficial
true of false: evolution can only happen over long periods of time. why
false
Evolution can work over long or short timescales
Some changes occur rapidly if there’s strong selective pressure
do populations or individuals evolve
populations
are Changes within an individual are typically inherited by their offspring? if no, what is the exception?
Changes within an individual are not typically inherited by their offspring (unless those changes affect gametes)
Does evolution make incremental changes>
Small changes built upon small changes over the course of millions of years
did we evolve from monkeys? why or why not
We did NOT evolve from monkeys or chimpanzees
We have a common ancestor, but we did not come from them
Evolution is NOT a linear path
recent changes in humans
lactose intolerance
Novel hair & eye colours
Reduced melanin to improve vitamin D synthesis
Spread of sickle cell allele to give resistance to malaria
