8/7/2019 W3 by Chau
1/3
Evolution in Extant PopulationsVariation in Form
Differentiation of Parts: different songs in
individualsOntogeny: similar beginning embryo which diverges
through development
Ambystoma tigrinum: different diet, different behavior
(carnivorous & herbivorous), identical
genotypeGrowthAccretion: shells and trees add new layers
Addition: Foraminifera and echinoderms add partsMolting: (crabs,
trilobites) shedding outer layer for larger bodice underneath;
outgrowing your
clothesModification: hands are born with all bones which
lengthen and changes over time
Isometric growth: proportions stay the same, size
changesAllometric growth: shape and features changes; apes and
humans
Sexual dimorphismPopulation variation (colors in plants, finger
lengths between gender)
geographic variation in deer mice leads to population variation
of camouflaging colorpatterns
variations of monarch flycatchers across islandsPhenotypic
plasticity: nutritional variation in beetles and Daphnia longiremis
(plankton)
Phenotypic plasticity vs rapid evolution (Northern pike)
Cline: gradual change in phenotype across landscape
(elevation)Ring species: variation across landscape until
speciation amongst adjacent populations
Modes of SpeciationAllopatric: physical barrier divides
population
Peripatric: small founding population enters isolated
nicheParapatric: new niche found adjacent to original one
Sympatric: speciation without physical separation
Origin of LifeWhat is life
process energy separate from environment store and process
information (DNA) replicate these instructions crown-group: life
stems from MRCA of all extant living organisms
Domains of life: Eukarya, bacteria, archaea
Lateral gene transfer (esp bacteria) complicates tree of life to
create web of lifePrimodial soup: amino acids synthesized from
methane, ammonia, hydrogen and boiling water
using electric spark for over a week (Miller)Banded iron
formation: indication of photosynthesis by cyanobacteria producing
oxygen to
support life on Earth; also creating stromatoliteSnowball
Earth
reduction of methane and CO2 due to lack of silicate weathering
in warmer conditions; heat nolonger trapped within atmosphere
(opposite of global warming today)
temperature cools, snow develops reflecting sunlight creating
positive feedback for more coolingand snow
8/7/2019 W3 by Chau
2/3
volcanism puts CO2 back into atmosphere, rescue
Readings
Palumbi - Humans as the Worlds Greatest Evolutionary Force
Use of antibiotics have quickly evolved many micro-organisms in
our world today, creating a
cascading effects on other species. Bacteria will develop
resistance to treatment as quickly as a
year after first use, forcing us to constantly develop new
vaccines and pesticides. Methods for
controlling this rapid evolution: withholding most powerful
drugs, screening for resistance
before therapy, integrated pest manage where multiple methods
are used simultaneously, refuge
planting, engineering evolution to make resistant individuals
less fit when chemicals are
removed.
Trinkaus - Late Pleistocene adult mortality patterns and modern
human establishment
High immature-adult ratios within fossil samples suggest
generally low adult life expectancy.
However, they may be a bias in who was buried, and older adult
skeletons are considered to bemore fragile and less likely to
become fossilized. It is concluded that mobility was necessary
for
survival, and individuals who are unable to keep up are left
behind to die. Changes in human
evolution during the Late Pleistocene must have been the result
of increase fertility or reduction
of immature mortality, not adult longevity.
Losos & Ricklefs - Adaptation and diversification on
islands
Darwin mentioned that isolated lineages can evolve
independently, ultimately forming new
species, so islands are excellent examples of this. Stephen
Gould proposes that, if history were
repeated, the outcome of evolution would be entirely different.
Islands are good models for
evolutionary studies because the first colonists are often
unchallenged and free to diversify innovel ways. Unbalanced
colonization and strong dispersal abilities sometimes make
islands
more diversified than continents, and old/isolated islands
contain species not found anywhere
else; Morris makes an argument that organisms would evolve to
fill the same ecological niches
(woodpeckers replaced by lemur that can also extract grubs from
trees), so not entirely novel.
Adaptive radiation: natural selection and sympatric speciation
eventually leads to a clade of
coexistent taxa, adapted and specialized to use a broad spectrum
of ecological space. Larger
islands have more complex geography and more opportunities for
allopatric isolation (more
niches). Older islands are more prone to extinction of species,
though the potential role of
extinction as a select agent and potentially creative force has
not yet been resolved.
Lazcano - Historical Development of Origins Research
For a long time, the theory of spontaneous life remained
unchanged due to
political/ideological pressures, until the birth of biochemistry
suggested that organic molecules
can be synthesized using organics. Most of the early experiments
did not consider Earths
primitive conditions, however. By considering the first life
forms as a collection of single
molecules, researchers (Miller) hypothesized a primordial soup
that can generate amino acids
