20 Flashcards
Evidence of ancient life
stromatolites: 3.2 BYA
layers of sediment left by cyanobacterial mats
Are stromatolites evidence of life or non-organic origin?
2008 study of 2.7 Gy stromatolites: Found shapes similar to bacteria, associated with the kind of nanocrystals in modern bacteria-grown stromatolites.
What was in the microfractures? (originally thought to be carbon)
hematite deposits
What happened when energy was added to Earth’s early atmosphere?
The basic building blocks of life were created
primordial soup model (list characteristics)
– Early oceans full of organic material
– Methane-ammonia atmosphere
– Addition of external energy (heat/UV/lightning)
into these gases end up into monomers
– Most widely accepted model
Urey-Miller Experiment
Abiotic production of amino acids, resulting in the production of 13 of 22 amino acids used in living systems
How did life come from outer space?
comets
Evidence of comets carrying life + what did these comets carry?
intense early bombardment of Earth by rocky and icy bodies
carry organic molecules, amino acids
ex. Murchison meteorite
How did life come from the center of the Earth?
hydrothermal waters
Primitive bacteria at surface of Earth
chemotrophs – Yellowstone hot spring bacteria
similar bacteria found in very deep wells, mid-ocean ridge black smokers
2 main types of organisms
prokaryote, eukaryote
characteristics of prokaryote
small, no nucleus, limited organelles, simple ring chromosome with few genes
characteristics of eukaryote
large, organelles, nucleus, complex chromosomes with many genes
symbiosis
evolution of eukaryotes from prokaryotes
gene flow
movement of alleles between pop due to migration
tends to make pop more genetically similar over time (uniform allele freq)
genetic swamping
the reduction in a population’s ability to adapt due to gene flow from a maladapted population
local genotypes replaced with hybrids
adaptive introgression
alleles move between populations via gene flow, helping local pop adapt to environment w/o needing new mutations
introducing something foreign that leads to better fitness
what can gene flow lead to?
new populations, new traits, even new species
speciation
the process by which one species splits into two species
this is an example of macroevolution
microevolution
changes in allele frequency in a population over time
macroevolution
broad patterns of evolutionary change above the species level
How do new species originate from existing species?
Over time, populations of a single species connected by gene flow can diverge genetically, giving rise to a new species
species
basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity
most common way to define species
biological species concept
biological species concept
according to BSC, a species is a group of pop whose members
- have potential to interbreed in nature
- produce viable, fertile offspring
- do NOT produce viable, fertile offspring with members of other such groups
how does reproductive isolation occur
it results when biological barriers impede members of two species from interbreeding and producing viable, fertile offspring
classified by whether factors act before or after fertilization
what do these barriers limit
formation of hybrids and gene flow between the forming species
the BSC relies on the disruption of which aspect of pop genetics?
gene flow
2 main types of biological barriers
prezygotic barriers, postzygotic barriers
prezygotic barrier
blocks fertilization from occuring by:
- impeding diff species from attempting to mate
- preventing successful completion of mating
- hindering fertilization if mating is successful
zygote
diploid cell produced by the union of haploid gametes during fertilization; i.e. a fertilized egg
types of prezygotic barriers
habitat isolation
temporal isolation
behavioral isolation
mechanical isolation
pollinator isolation
gametic isolation
habitat isolation
2 species that occupy diff habitat within same area may encounter each other rarely
temporal isolation
species that breed at diff times of day cannot mix their gametes
nocturnal animals and diurnal animals
behavioral islation
courtship rituals and other unique behaviors to a species are effective barriers to mating
pollinator isolation
species of plant that attract diff types of pollinators have barrier to reprod
bee pollinating flower vs hummingbird pollinating flower
mechanical isolation
mating attempted, but morphological diff prevent completion