bio 221 1-5 pt 1
selection vs evolution
Selection occurs within a population but evolution requires generations.
what do fossils show
show evolution over long time frames
cabbage, broccoli, cauliflower being descendant of wild mustard is an example of
artifical selection
can evolution happen on small time scales
yes
what are darwins 4 postulates
1. variation is pre existing and can be passed on to offspring
2. selection is based on environment
3. not all offspring survive (those who survive is non random)
4. differential reproduction (those with advantageous traits in that space and time are more likely to survive and reproduce)
what was darwins weakness
didn't propose a theory for inheritance, the concept of mutation was not developed until 1900's
what type of evolution did lamarck believe in?
transformational evolution
what type of evolution did darwin believe in?
variational evolution
what is the most powerful direct evidence of evolutionary change
fossils
what does fossilization need
an environment where they can fossilize
who first started study fossils
george cuvier first started studying fossils and first proposed extinctions
what is wrong with the fossil record
it is incomplete, we've only found the easiest to find fossils, hot humid areas rarely have fossils. fossils are also biased because hard and bony parts/ aquatic organisms fossilize better.
why is dating fossils hard
due to changing sediment conditons, if the environment that the fossil was in changes it can obscure the date
how old is the universe? how about the earth?
universe- 13.77 byo and earth- 4.5 byo
how do we know how old the earth is
because of 4.4 byo meteorite in australia and zircon crystals that are also this old, darwin also hypothesized this because of geological formations in england
how does a fully radioactive element decay
at a measurable rate
when were all radioactive isotopes formed
at dawn of solar system
what does the complete absence of shorter lived parent isotopes tell us
that our solar system is ancient
how old is life on earth?
approx 3.8byo, esitmated by principle of superpostion
list these key events from oldest to most recent, fossils of oldest known chordates (incl vertebrates), oldest land vertebrates, dinosaurs, oldest land plant fossils, our common mammalian ancestors, birds, the oldest trackways
520 Mya: fossils of oldest known chordates (incl vertebrates)
480 Mya: the oldest trackways
475 Mya: oldest land plant fossils
360 Mya: oldest land vertebrates
230 Mya: dinosaurs
180 Mya: Our common mammalian ancestor
150 Mya: birds
is there any fossils from the origin of life period
no just zircons and stromatolites
what are the two main hypotheses of the origin of life
deep sea vents and hot springs
what is the deep sea vent hypothesis
that there was tons of energy, carbon and lots of redox worthy chemicals
what is the hot spring hypothesis
that there was tons of energy and nutrients, lots of oxidized minerals
what is the miller-urey experiment
where they tried to recreate the conditons of early earth but failed
what can we hypothesize about the atmosphere and conditions of early earth through rocks?
very little oxygen, lots off ammonia, lots of methane, lots of volcanic activity. These conditions together could cause abiotic synthesis of organic molecules
what is the presumed origion of eukaryotes
1.8bya because of acritarchs
how old were mutlicellular fossils presumed to be
used to think 1.6 byo, interpreted as filamentous algae
635 myo were the oldest fossils intepreted as animals.. what are they?
sponges
what is lifes earliest animals
known as the ediacaran fauna
what did the cambrian, " the innovation era" give rise to
segmentation, 3 axis's, more complexity. (ex. trilobite, mollsucs, and first chordates)
what is the first hypothesis of why the cambiran was the innovation era
Increased O2, allowed more primary productivity, allows emergence of predators, allows inc in body size BUT oxygen levels didn’t necessarily change around Cambrian and larger animals already existed
what is the second hypothesis of why the cambrian was the innovation era?
Evolutionary innovation, evolution of novel traits (ex. Segmentation) allowed increased adaptability (ex. Hox gene cluster evolution may have sparked Cambrian)
what is the third hypothesis of why the cambrian was the innovation era?
Predation and arms race, if predation arose during Cambrian it could explain, inc body size, hard body size, motility/ swimming ability
when did land plants arise? what plants?
the late Ordovician and early Silurian period (450 Mya). Most likely liverwort like organisms, possibly co invaded by fungi, vascular plants evolved after
what is the oldest known land animal fossils ~ 428 mya
millipede
what are amniotes~ 314 mya
amniotes produce shelled eggs
what was the event when the meteor hit earth 66 Mya (end of cretaceous) and caused a massive shift on earth? what happened to organism popualtions
this was the paleogene mass extinction event which caused the loss of big reptiles but the little mammals thrived (prob due to loss of predators)
what did darwin think about assoicating the most recent common ancestor of species.
Darwin thought, more shared features= more recent common ancestor
what are infromative characters/traits in a phylogeny
vary with the taxa of interest, have different states, can be morphological, behavioural, biochemical, genetic.
why do we need to use taxonomy and phylogenetics?
to reconstruct evolutionary relationships so that trees can reflect shared ancestry
order the 9 domains
life, domain, kingdom, phylum, class, order, family, genus, species
what did mendel determine about hwo traits of offspring were determined
mendel determined that traits of offsprings were determined by parental factors that remained discrete.
what are discrete traits
traits that have no blending
what did mendel use to study traits
hand pollinated pea plants with known traits, he was the first to use math to explain predicted traits in offspring
explain the results of mendels pea experiment
Crossed round and wrinkled peas, all progeny were round (F1)- all showed only one parental phenotype, no blend, these were heterozygote (het) and showed the dominant traits. Then he crossed Rr and Rr and got progeny that were 3 R: 1 W (approximately).
what did mendel find about the nature of how traits come
that traits came in pairs and the genes are halved in germ cells
what are mendels 3 laws
law of dominance, law of segregation, law of independent assortment
what are non mendelian traits
most traits dont follow the phenotypic ratios of mendelian inheritance because of multiple alleles of one gene, influence on other genes and influence of environment
how is variation created in a population of diploid organisms
a diploid (2n) will only carry 2 alleles in an individual but multiple alleles can exist in population which can create variation in a population without necessarily being influenced by other genes or the environment
what are two exmplaes of mutliple alleles
ex. pavilion dardanus butterlfies which have multiple alleles which give rise to multiple wing patterns within the same speices
ex. human ABO blood type has 3 alleles, 9 possible genotype within pop, 4 possible phenotypes
are most traits continous or discrete
most traits are continous
what is a continous trait
where their phenotypic variation exists on spectrum
what causes continous traits
polygenic inheritance, where many genes contribute to the same traits
how much of an impact can the environment have on phenotype
environmental conditions can have a great impact on phenotype, even greater than genotype sometimes.
what are examples of enviornmental condtions that can impact phenotype
These conditions can include, temp, availability of nutrients, presence of toxins/mutagen, some can be the maternal effect
how do you know if a phenotype has a genetic origin or is purely environmental
Easiest way is to force mate individuals with opposite phenotypes if the progeny will follow a Mendelian inheritance pattern in the F2 but most traits aren’t Mendelian.
what is the broad structure of eukaryotic DNA
it is arranged into chromosomes, multiple linear chrosomes. DNA in eurkaryotes is organzied using histone proteins. The DNA wraps around a histone octomer creating a nucleosome.
what is the advantages of how DNA is organized
The organization of DNA protects it from damage, organizes the nucleus and limits access of transcriptional machinery to DNA
where are chromsomes stored, how does it sizes work
chromsomes are stored in the eukaryotic nucleus (membrane bound organelle), chromosome sizes can vary greatly- msot eukaryotes are diploid (2n)
how do soma and germ cells differ.
in the soma of humans cells are diploid but germ cerlls are haploid
what is the general steps of central dogma
DNA to RNA (transcription), RNA to protein (translation). Only one strand of DNA is used as a template.
what carries out translation.
Translation is carried out by ribosome and uses a universal codon table. 3 nucleotides= 1 amino acid
what allows for mutuational tolerance
Redundancy in the genetic code allows mutational tolerance (more than one codon encoding same amino acid. Most of redundancy is @ 3rd codon.)
what gives rise to different cells in eukarytoes
In most euk, each cell contains the exact same entire genome. Only a fraction of genes are expressed giving rise to different cell types.
when does most gene regulation occur
Most gene regulation occurs at the level of transcription initiation. This is regulated by a region of the DNA called the promoter.
what is another common area of gene regulation
alternative splicing
is most of the eukaryotic genome expressed
Most of eukaryotic genome is not expressed and most doesn’t become protein
pseudo genes are
genes that have mutated such that they no longer contain a promoter, hence not being transcribed to mrna
what are genetic markers
markers are specific sequences of DNA, often located throughout the genome, can be used as refrerence points to track the inheritance of genes linked to certain traits. the goal is to find genetic markers significantly associated with the extremes of the trait
what are transposable elements
jumping genes, products of ancient viral infection. Can change positions within the DNA, can cause mutations by disrupting the genes or regulatory regions that they jump to.
a bigger genome is a more complex genome? example?
no gemone size is unrelated to complexity, genome size caries greatly between organisms. ex. sea anemones have more genes than humans.
where do most complex organisms get variation from
from alternative splicing not from gene #
what is alternative splicing
process by which a single gene can produce multiple different versions of protein, occurs during RNA processing. alternative splicing allows for the exons (coding regions) to be arrange in different combinations leading to the production of multiple proteins from the same gene.
what does evolution rely on to drive variation and selection
meiosis
what are the products of meiosis
4 genetically different haploid gametes
through what mechanisms does meiosis generate genetic variation
crossing over, independent assortment, random fertilization
pair of chromosomes have the same blank but potentially different blank
pair of chromsomes have same gene order but potentially different alleles
what is the point of meiosis
it generate genetic variation and haploid gametes.
how does meoisis cause gentic variation
due to the crossing over in prophase I (homo chromo exchange genetic material)
and
independent assortment in metaphase I (homo chromo pairs line up, arrange randomly)
and
random fertilization (random sperm and random egg)
is a mutation always harmful
only the environment determines if a mutation is harmful (most common), neutral, beneficial (rare).
how do asexual organisms get varation
they rely on very rare benefical mutations for variation
what are the 4 types of point mutations
silent muation, missense mutation, nonsense mutation, frameshift mutation
what is a point mutation
change in a single base pair of DNA sometimes due to DNA replication error or exposure to mutagens
what is a silent mutation?
change in DNA seq that doesnt change protein seq
ex. GAA changed to GAG but both of these code for the same amino acid
what is a missense mutation?
a change in a single base pair that results in a codon coding for a different amino acid which can affect protein function
ex. GAG mutated to GTG code for a different amino acid which can affect the protein.
what is a nonsense mutation
point mutation that changes codon to a stop codon, causing protein to be prematurely shortened. Can cause to loos of function or non fuctional proteins.
ex. CAA muated to UAA (stop codon), causes translation to stop early.
frameshift mutation
deletetion/insertion of nucleotide so that the reading frame shifts of the genetic sequence.this leads to a complelety different protein sequence after the point of mutation which can be devastating to protein function
which point mutations effect the protein
missense maybe, nonsense, frameshift
are point mutations rare
no they are common, but the rarer events have greater effects
are aneploid rare
yes, gain/loss of chromosome
what is gene dosage
gain or loss of chromosomes, often have great effects
is the odd of any one base pair mutating low
yes
what is the average number of point mutations that occur in the genome of an indiviudal from one gen to the next.
around 61
what does HW eqbrm allows us to predict
HW allows us to predict the particular phenotypes in offspring for an entire pop
what does HW eqbrm provide
HW eqbrm provides a null hypothesis for testing evidence of evolutionary change.
how could the ratio of genotypes and phenotypes be the same in every generation
if there was no selection/mutation/drift
is H-W eqbrm satisifed in reality
no, to be satisifed a population must be infinitely large, have no net muation, no net migration, mate randomly, and have no selection (no disadvantageous/advantageous traits)
if H-W satisifed how would the pop look
alleles and genotype freq in offspring would be the same as parent gen
what is HW eqbrm equation. p=? q=?
P^2 + 2pq + q^2= 1
p= dominant allele
q= recessive allele