exam 1 Flashcards
unity and continuity of life
-life on earth has descended from a common ancestor
-continuity among all living things stems from the inheritance of info encoded in DNA
adaptation and correlation
-evolution has been called that GUT of biology
adaptation and the correlation of structure and function
-adaptation provides a framework for making sense of the otherwise bewildering variation in nature
organisms interact with one another and their environment
-organisms must acquire energy from their environment
-competition, mutualism, predation and parasitism
-ecological context
diversity is valuable, yet under threat
-ecosystem services
-intangible benefits
-human activities threaten biodiversity
defining ecolution: broad definition - descent with modification
-suggests evolutions role in the unity and diversity of all species
-evolutionary relationships are often illustrated with treelike diagrams that show ancestors and their descendants
defining evolution: narrow definition
a change in the genetic composition of a population over generations
-note that evolution is something that happens to pop, not individuals
1795
Hutton proposes his principle of gradualism
1798
maithus publishes “essay on the principle of pop
1809
charles darwin is born
lamarck publishes his hypothesis of evolution
1812
Cuvier publishes his extensive studies of vertebrate fossils
1830
Lyell publishes principles of geology
1831-36
Darwin travels around the world oh HMS beagle
1844
Darwin writes his essay on descent with modification
1858
Wallace send darwin his hypothesis of natural selection
1859
on the origin of species is published
Thomas Malthus (1766-1834)
essay on the principle of pop (1798)
-charles darwin, from his autobiography (1876)
Georges Cuvier (1769- 1832)
-Fossils in older strata does not equal fossils in newer strata
-Cuvier advocated catastrophism
-didn’t believe in evolution
James Hutton (1726-1797) and Charles Lyell (1797-1875)
that changes in earths surface can result from slow continous actions still operating today
-lyells principle of uniformitarianism
-this view strongly influenced Darwins thinking
Jean-Baptiste de Lamarck (1744-1829)
-observed evolution in the fossil record
-proposed mechanisms:
-use and disuse
-inheritance of acquired characters
August Weismann barrier 1892
cutting mices tails dont make cut tailed offspring
Darwins personal history and contribution
-Charles Robert Darwin (1809- 1882)
-naturalist par excellence
-botany
-zoology
-incomplete forays into medicine and ministry
Voyage of the beagle (1831-1836)
-he observed that fossils resembled living species from the same region, and living species resembled other species from nearby regions
-rather than those of farther regions with similar environments
Darwin delays publication
-by 1840s, Darwin had worked out most of his hypotheses of how these adaptations could arise by natural selectino
-reluctant to publish
-collects more and more evidence
Alfred Russel Wallace (1823-1913)
reaches similar conclusions, sends manuscript to darwin
-succeeded where thers failed due to “immaculate logic and an avalanche of evidence”
on the origin of species by means of natural selection (1859)
Darwin explained three broad observations:
-the unity of life
-the diversity of life
-the match between organisms and their environment
descent with modification
-“evolution” does not appear in 1st ed. of Origin
-“Descent with modification” was the phrase he used
-attributes unity of life to descent of all organisms from a common ancestor
-gradual accumulation of modifications over millions of years leads to adaptations and biodiversity
evidence for evolution
-darwin noted that humans have modified others species by selecting and breeding individuals with desired traits, a process called artifical selection
-Darwin drew two inferences from two observations
observation 1:
members of a pop often vary in their inherited traits
-ladybugs have different shades and dots
inference 1
-individuals whose inherited traits give them a higher probability of surviving and reproducing in a given environment tend to leave more offspring than other individuals
if the environment changes
observation 2:
-all species can produce more offspring than the environment can support, and many of these offspring fail to survive and reproduce
inference 2
-the unequal ability of individuals to survive and reproduce will lead to the accumulation of favourable traits in the pop over generations
understanding natural selection : common misconceptions
-new discoveries continue to fill the gaps identified by Darwin in The origin of species
-figure
there are 4 types of data that document the pattern of evolution
-direct observations
-homology
-the fossil record
-biogeography
direct observations
fig 22.14- the rise of MRSA -READ
-which two points about natural selcation do the soapberry ex and the MRSA ex highlight?
homology
-similarity resulting from common ancestry
-supports the evolutionary description of descent with modification
anatomical and molecular homologies
-homologous structures are anatomical resemblances representing variations on a structural theme present in a common ancestor
-forelimbs
-vestigial structures
-pseudogenes
fig
homologies and “tree thinking”
-evolutionary tress are hypotheses about relationships among different groups
-homologies form nested patterns in evolutionary trees
-evolutionary trees can be made using different types of data, for ex, anatomical and DNA sequence data
the fossil record. the transitin to life in the sea
-fossils can document important transitions
-ex. the transition from land to sea in ancestors of cetaceans
Biogeography
-the study of the geographic distribution of species, provides evidence of evolution
-earths continents were formerly united as single large continent (pangaea), but separated by continental drift
-an understanding continent movement and modern species distribution allows us to predict when and where different groups evolved
mendel and the modern synthesis
-one of the great challenges to Darwins theory of evolution by natural selection was the lack of understanding inheritance
-the next great advance in evolutionary biology would require genetics
gregor mendel
-demonstrated particulate inheritance
ready for a modern synthesis
-inheritance better understood
-new field of genetics develops
-in particular, population genetics
-stage is set for a synthesis of several disciplines under the umbrella of evolutionary biology
populations _ not _
populations evolve, not individuals
microevolution
-a change in allele frequencies in a population over generations
3 mechanisms cause allele freguencies in a pop over generations
-natural selection
-genetic drift
-gene flow
only natural selection causes adaptive evolution
what causes adaptive evolution
natural selection
genetic variation
-variation in heritable traits is a prerequisite for evolution
-mendels work on pea plants provided evidence of discrete heritable units (genes)
genetic variation among individuals is caused by:
differences in genes or other DNA segments
P=G+E
genetic veriation within and between populations
within pop:
-nucleotide variability rarely results in phenotypic variation
-note all phenotypic variation is the result of genetic variation
figs
where does genetic variation come from?
sources:
-new genes and alleles can arise by mutation or gene duplication
-sexual reproduction can result in genetic variation by recombining existing alleles
sexual reproduction
-sexual reproduction can shuffle existing alleles into new combinations
-crossing over
-independent assortment of chromosomes
-fertilization
hardy-weinberg
the equation can be used to test whether a pop is evolving
-the first step in testing whether evolution is occurring in a pop is to clarify what we mean by a pop
population
a localized group of individuals capable of interbreeding and producing fertile offspring
gene pools
consists of all the alleles for all loci in a pop
-a locus is fixed if all individuals in a pop are homozygous for the same allele
fig
allele frequencies
-if there are 2 or more alleles for a locus, diploid individuals may be either homozygous or heterozygous
-the frequency of an allele in pop can be calculated
-for dipoid organisms, the total number of alleles at a locus is the total number of individuals times 2
-the total number of dominant alleles at a locus is 2 alleles for homozygous dominant individual plus 1 allele for each heterozygous individual; the same logic applies for recessive alleles
-by covention, if there are 2 alleles at a locus, p and q are used to represent their frequencies
-frequency of all alleles in a pop will add up to 1
-that is, p + q = 1
the hardy-weinberg equation
-describes the genetic makeup we expect for a pop that is not evolving at a particular locus
-if the observed genetic makeup of the pop differs from hary-weinberg expectations, it can be concluded that pop may be evolving
-evolutionary null hypothesis
hardy-weinberg equilibrium
-in a given pop where gametes contribute to the next gen randomly, and mendelian inheritance occurs, allele and genotype freq remain constant from gen to gen
-such a pop is in hardy-weinberg equilibrium
fig
conditions for Hardy-weinberg equilibrium
-the HW theorem describes a hypothetical pop that is not evolving
-in real pop, allele and genotype freq do change over time
the 5 conditions for nonevolving pop are rarely met in nature:
-no mutations
-random mating
-no natural selection
-extremely large pop size
-no gene flow
genetic drift
fig
pop size matters
-all pop will experience genetic drift but the effects of genetic drift on allele freq is on average more pronounced in small pop
founder effect
-when a few individuals become isolated from a larger pop, this smaller group may establish a new pop whose gene pool differs from the source pop
-blown by storm to new area
bottleneck effect
-a sudden change in environment, such as a fire or flood, may drastically reduce the size of a pop
-a severe drop in pop size
consequences for pop
-cuz the change in allele freq is random and pop are independent, genetic drift leads to an increase in genetic variation among pop
-genetic drift is expected to lead to an increase in genetic variation among pop
fig
gene flow
-consists of movement of alleles among pop
-alleles can be transferred through movement of fertile individuals or gametes (pollen ex)
gene flow and local adaptation
-gene flow can decrease the fitness of a pop
-consider the water snake pop of lake eerie
mainland = A-C
Island = D
unexpected results- snakes on different places- they swam
natural selection trying to keep up but gene flow is overpowering
consequences for pop
-gene flow can lead to increased genetic variation within pop
-GF can lead to decreased differences in the allele composition among pop
-GF can increase the fitness of a pop through local adaptation
-can lead to spread of beneficial alleles
fig
natural selection fig
fig
relative fitness
-the conribution a genotype makes to the gene pool of the next gen ( # of offspring produced), relative to the contributions of other genotypes
-selection acts to increase the freq of alleles that confer a reprocuctive advantage (having higher relative fitness)
fig
directional selection
favours individuals at one end of the phenotypic range
extremes are selected for, intermediates selected aganst
disruptive selection
favours individuals at both extremes of the pheno range
-african finch ex: two bill morphs in black-bellied seed cracker finches
-large-billed individuals feed on sedges with hard seeds; small-billed feed on sedges with soft seeds
fig
stabilizing selection
-favours intermediate phenotypes and acts against extreme phenotypes
other forms of selection
-sexual selection
-balancing selection
-frequency-dependent selection
sexual selection
-is natural selection for mating success
-it can result in sexual dimorphism, marked differences between the sexes in secondary sexual characteristics
-certain inherited traits result in an increase in likelihood of obtaining mates!
sexual dimorphism
the systematic difference in form between individuals of different sex in the same species
2 types of sexual selection
intrasexual selection and intersexual selection
intrasexual selection
-the strongest most fit gets the mate
-they fight others to impress
intersexual selection
-female choosiness
-do behaviours to get attention
-birds dancing
How do females preferences evolve?
fig
balancing selection
-why are disadvantageous alleles not removed by natural selection?
-balancing selection occurs when netural selection maintains stable frequencies of two or more phenotypic forms in a pop
balancing selection includes
-heterozygote advantage
-freqency-dependent selection
heterozygote advantage
-occurs when heterozygotes have a higher fitness than do both homozygotes
-natural selection will tend to maintain two or more alleles at that locus
-heterozygote advantage can result from stabilizing or directional selection
Aa is protected cuz it acts like AA
hetero with intermediate = stabilizing
frequency-dependent selection
-the fitness of a phenotype declines if it becomes too common in the pop
-selection can favour whichever phenotype less common in a pop
fig
why natural selection cannot fashion perfect organisms
-1 can only act on existing variations -only the fittest phenotypes in a pop
-2) evolution is limited by historical constraints–cant add random limbs. Birds wings have parts that were already there
-3) adaptations are often compromises- organisms do many diff. things. Seals could walk better online with feet but then cant swim as well
-4) chance, natural selection, and the environment interact- wind doesn’t blow the fittest allele to a new island. so founder effect not always the best
speciation
-the origin of new species, is at the focal point of evolutionary theory
-evolutionary theory explains how new species originate and how pop evolve
-microevolution vs macroevolution
what is a species?
-the biological species concept is based on the potential to interbreed rather than on physical similarity
limitations of the biological species concept
-gene flow can occur between distinct species
-ex, grizzly bears and polar bears can mate to produce “grolar bears”
Other species concepts
-morphological SC
-lineage/Phylogenetic SC
the lineage species concept
fig
what is and isnt a species has consequences
-eastern long-toed salamander is currently list as being of “special concern” in alberta cuz of its narrow distribution in the province
-genetic data reveals that the range of this subspecies is even more limited in the province than current range maps show
-there is some evidence taht this subspecies is reproductively isolated from the others
what are the reproductive barriers
-habitat isolation,
-temporal isolation,
-behavioural isolation
-mechanical isolation,
-gametic isolation,
-reduced hybrid viability,
-reduced hybrid fertility,
- hybrid breakdown
habitat isolation
2 species that have different habitats in the same area might see each other rarely
temporal isolation
species that breed during different times of day, seasons, or years, can’t see each other to mix their gametes
behavioural isolation
-behavioral rituals enable mate recognition- a way to identify potential mates
-different dances might make others confused and leave
-toothless
mechanical isolation
-mating is attempted but morphological differences prevent its successful completion
-snails, right snails have penis on right side, cant mate with left side snails
gametic isolation
-sperm of one species might not be able to fertilize eggs of another species
-might not be able to penetrate or will die fast
reduced hybrid viability
-genes of different parent species may interact in ways that impair the hybrids development or survival in its environment
reduced hybrid fertility
-if the chromosomes of the 2 parent species differ in number or structure, meiosis in the hybrids may fail to produce normal gametes
-they become infertile like mules
hybrid breakdown
some first-gen hybrids are viable and fertile, but when they mate with one another or with either parent species, offspring of the next generation are feeble or sterile
speciation
-the process by which one species splits into 2
-barriers = traits
fig
trait divergence: ex
-the colonization of freshwater by a marine stickleback ancestor occurred in many separate locations, and was accompanied by a consistent suite of changes
marine fish:
-longer
-slimmer body
-long spines
-lots of armor plates
-salt water physiology
-open-water (limnetic)
-more gill rakers
freshwater:
-smaller
-deeper body
-shorter (or absent spines)
-freshwater physiology
-fewer armor plates
-bottom (benthic) feeding
-fewer gill rakers
-speciaton can occur in 2 ways
-allopatric speciation
-sympatric speciation
allopatric speciation
“other country)
-gene flow is interrupted when a pop is divided into geographically isolated subpopulations
-barrier def differs for different organisms
reproductive isolation as a by-product of selection
-in ponds with predatory fishes, the mosquitofishs head is stremlined and the tail is powerful, enabling rapid bursts of speed
-in ponds without predatory fishes, mosquitofish have a different body shape that favours long, steady swimming
allopatric speciation in snapping shrimp
-gene flow occured between atlantic and pacific pop.
-the 2 species arose as a consequence of geographic separation
-regions that are isolated or highly subdivided by barriers typically have more species than other similar regions
-geographic isolation prevents interbreeding between members of allopatric pop, physical separation is not a bio barrier to reproduction
sympatric speciation
“same country”
-speciation takes place in geographically overlapping pop
-sympatric speciation can occur if gene flow is reduced by factors including:
-polyploidy
-sexual selection
-habitat differentiation
ployploidy
-the presence of extra chromosome sets due to accidents during cell division
-autopolyploid vs allopolyploid
fig
sexual selection
-sexual selection can drive sympatric speciation
-sexual selection for mates of different colours has likely contributed to speciation in cichlid fish in lake victoria
habitat differentiation
the fish select fish that are closely like them to mate
under a weird light thing the females thought different fis were like them and so mated
does sexual selection in cichlids result in reproductive isolation?
fig
rotations around the nodes (common ancestors)-
don’t change the evolutionary relationships!
fig
-tree construction is based on 2 main concepts
-principle of parsimony
-the use of shared, derived homologies
parsimony
-the assumption that evolution proceeds by a smaller rather than a larger number of events
the simpilest tree is the best
fig
shared, derived homologies
-derived means non-ancestral (new trait)
fig
inferring phylogenies: a worked ex
grouping taxa by shared derived traits
-the most inclusive group includes all taxa with vertebrae (shared, derived character) and separates the ingroup from the outgroup
-the next most inclisive group includes all taxa with a boney skeleton and separates our basal ingroup taxa from the others
-the next most inclusive group includes all taxa with 4 limbs
-the next most inclusive includes all taxa with an amnitic egg
-we then have 2 equally inclusive groups; one that has hair and one that has 2 post-orbital fenestrae. these tie for our place in the hierarchy
fig
translating phylogeny into classification
3 potential ways
-based on monophyletic groups
-based on paraphyletic groups
-based on polyphyletic groups
monophyletic group (clade)
consists of an ancestral species and all of its descendents
fig
paraphyletic group
consists of an ancestral species and some of its descendents
fig
polyphyletic groups
consists of various species with different ancestors
fig
evolution can be defined more-
narrowly as a change in genetic composition of a pop over generations (narrow def)
evolution is something that happens to populations NOT individuals
gradualism
water makes tiny changes. then after years it will be big enough to be canons and such
Lammarckianism
is not true in a lot of situations
(cutting mice tails wont make their offspring not have tails)
epigenetic changes
moms with lots of stress adds menthol groups to baby (lamarckinism)
catastrophism
-theory that earths surfaces and landscape can largely be explained by sudden, short-lived, and violent events such as cataclysmic earthquakes, floods, and volcanic eruptions
uniformitarianism
the idea that earth has always changed in uniform ways and that the present is the key to the past
variation in a pop
traits that are heritable and more desired that is given to offspring
allele freq ex
consider a pop of wildflowers incompletely dominant for colour:
320 red (CrCr)
160 pink (CrCw)
20 white (CwCw)
-calculate the number of copies of each allele:
of flowers =
# of alleles =
320+160+20 = 500 individuals x 2 alleles (white and red) = 1000 alleles
Cr = (320 x 2) + 160 = 800 Cr
Cw = (20 x 2) + 160 = 200 Cw
(800 + 200 = 1000)
Cr= 800/1000 = 0.8
p + q = 1
0.8 + q = 1 q = 0.2
convergenct evolution
orgainisms that are closely related share characteristics cuz of common descent, distantly related organisms can resemble one another
-independent evolution of similar features in differnt lineages
hetero zygote advantage ex sickle cell
HH = no sickle cell
Hh = some normal, some sickle
hh= sickle cells, but is protected by malria
Hh is the most advantages with malaria cuz it is protected
favours phenotypes that are-
less common
-fish
Autopolyploidy
occurs when organisms have more than 2 sets of chromosomes from the same species
alloopolyploid
2 different species interbreed and produce hybrid offspring
various mechanisms can change a sterile hybrid into a fertile polyploid
-allos are fertile when mating but cant interbreed, and so they represent a new biological species
why are most hybrids sterile
the set of chromosomes from one species cannot pair during meiosis with the set of chromosomes from the other species
-morphy
character/ trait
sym/syn
shared
apo
derived/new
pleisio
ancient/old
aut
self/single
