ch 19-24
Carolus Linnaues' binomial nomenclature
-used to avoid ambiguity when communicating about research -latin -first part is the GENUS and the second part is the EPITHET, which is unique to each species. -The first letter is capitalized and the second lower case, the whole thing is italicized
*however some evidence suggests atmosphere had only nitrogen and carbon dioxide and was no reducing or oxidizing (electron moving). "neutral" atmospheres have produced organic molecules just the same. also researchers found these mcs formed under volcanic conditions. another source of organic mcs could have been meteorites. [murchison meteorite]
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*some ribozymes can make complementary copies of short pieces of RNA if they are supplied with nucleotide building blocks.
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Chromosomal mutations that affect many loci Are almost certain to be harmful May be neutral and even beneficial
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Geologic history and biological history have been episodic Marked by what were in essence revolutions that opened many new ways of life
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Molecular clocks Date the common ancestor of multicellular eukaryotes to 1.5 billion years The oldest known fossils of eukaryotes Are of relatively small algae that lived about 1.2 billion years ago
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Phylogeny refers to the development of a group, particularly through evolutionary lines. Consider, if you are familiar with it, the phrase "Ontogeny recapitulates phylogeny." Cladistics is a study in which groups (species, etc) are arranged on a phylogenetic tree according to the TIME at which they arose from other groups. For example, on a cladistic-type diagram, and earlier-evolving species would form a lower branch on the tree than one that evolved later. Taxonomy is the biological science that deals with arranging and naming groups and organisms. When Linnaeus first developed the form of taxonomy we use today, he based his system on morphological similarities and differences. These days, it is based on known phylogenetic relationships and similarities in DNA, for example. Systematics is a branch of Biology that deals with arrangement of taxonomic groups based on genetic relationships (usually). It's a way of making sense out of potentially confusing data.
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Some examples of geographic variation occur as a *cline*, which is a graded change in a trait along a geographic axis
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Some investigators have speculated that eukaryotic flagella and cilia Evolved from symbiotic bacteria, based on symbiotic relationships between some bacteria and protozoans
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The sickle-cell allele Causes mutations in hemoglobin but also confers malaria resistance Exemplifies the heterozygote advantage
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Two major mass extinctions, the Permian and the Cretaceous (meteor, dinosaurs) -caused by volcanic erruptions
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variation: Discrete characters Can be classified on an either-or basis Quantitative characters Vary along a continuum within a population
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four main stages of producing the first simple cells
1. abiotic (nonliving) synthesis of small organic moelcules, such as amino acids and nitrogenous bases. 2. joining of these mcs into macromolecules like proteins. 3. packaging of the mcs into *protocells*, droplets with membranes that maintained an internal chemistry. 4. origin of self-replicating molecules that eventually made inheritance possible.
why natural selection cannot fashion perfect organisms
1. selection can act only on existing variations. 2. evolution is limited by historical constraints. 3. adaptations are often compromises. 4. chance, natural selection, and the environment interact. "better than" basis
difference between an autopolyploid and an allopolyploid
An autopolyploid Is an individual that has more than two chromosome sets, all derived from a single species An allopolyploid Is a species with multiple sets of chromosomes derived from different species
Two basic patterns of evolutionary change can be distinguished: Anagenesis (ancestor gone) Cladogenesis (includes ancestor)
Anagenesis, also known as "phyletic change", is the evolution of species involving an entire population rather than a branching event, as in cladogenesis. When enough mutations have occurred and become stable in a population so that it is significantly differentiated from an ancestral population, a new species name may be assigned. A key point is that the entire population is different from the ancestral population such that the ancestral population can be considered extinct. A series of such species is collectively known as an evolutionary lineage. It is easy to see from the preceding definition how controversy can arise among taxonomists as to when the differences are significant enough to warrant a new species classification. Anagenesis may also be referred to as "gradual evolution".
homoplasies
Analogous structures or molecular sequences that evolved independently
Orthologous genes
Are genes found in a single copy in the genome Can diverge only once speciation has taken place
The best hypotheses for phylogenetic trees
Are those that fit the most data: morphological, molecular, and fossil
The biological species concept cannot be applied to
Asexual organisms Fossils Organisms about which little is known regarding their reproduction
difference between phylogeny and systematics
Currently, systematists use Morphological, biochemical, and molecular comparisons to infer evolutionary relationships Phylogenies are based on common ancestries inferred from fossil, morphological, and molecular evidence
neutral theory
Darwinian selection does not influence a lot of evolutionary change in genes and proteins because many of these changes do not affect fitness. Much evolutionary change in genes and proteins has no effect on fitness and therefore is not influenced by Darwinian selection And that the rate of molecular change in these genes and proteins should be regular like a clock
Homeotic genes
Determine such basic features as where a pair of wings and a pair of legs will develop on a bird or how a flower's parts are arranged (ex- insects)
outgroup comparison
Enables us to focus on just those characters that were derived at the various branch points in the evolution of a clade
5 conditions for hardy-weinberg equilibrium
Extremely large population size No gene flow No mutations Random mating No natural selection
point mutation
Is a change in one base in a gene Can have a significant impact on phenotype Is usually harmless, but may have an adaptive impact -rare in animals in plants, more rapid in microorganisms
heterochrony
Is an evolutionary change in the rate or timing of developmental events Can have a significant impact on body shape
relative fitness
Is the contribution of a genotype to the next generation as compared to the contributions of alternative genotypes for the same locus
allometric growth
Is the proportioning that helps give a body its specific form
When oxygen began to accumulate in the atmosphere about 2.7 billion years ago
It posed a challenge for life It provided an opportunity to gain abundant energy from light It provided organisms an opportunity to exploit new ecosystems
diploidy
Maintains genetic variation in the form of hidden recessive alleles
Population geneticists
Measure the number of polymorphisms in a population by determining the amount of heterozygosity at the gene level and the molecular level
Average heterozygosity
Measures the average percent of loci that are heterozygous in a population
neutral variation
Neutral variation increases genetic variation, allowing a population to carry more alleles that may help it respond to environmental change.
Earnst Mayr's dissection of Darwinian theory
Observation #1: For any species, population sizes would increase exponentially if all individuals that are born reproduced successfully Observation #2: Nonetheless, populations tend to be stable in size Except for seasonal fluctuations Observation #3: Resources are limited Inference #1: Production of more individuals than the environment can support leads to a struggle for existence among individuals of a population, with only a fraction of their offspring surviving Observation #4: Members of a population vary extensively in their characteristics No two individuals are exactly alike Observation #5: Much of this variation is heritable Inference #2: Survival depends in part on inherited traits Individuals whose inherited traits give them a high probability of surviving and reproducing are likely to leave more offspring than other individuals Inference #3: This unequal ability of individuals to survive and reproduce Will lead to a gradual change in a population, with favorable characteristics accumulating over generations
Balancing selection
Occurs when natural selection maintains stable frequencies of two or more phenotypic forms in a population Leads to a state called balanced polymorphism
The earliest types of photosynthesis Did not produce oxygen
Oxygenic photosynthesis Probably evolved about 3.5 billion years ago in cyanobacteria
The Origin of HIV
Phylogenetic analysis shows that HIV Is descended from viruses that infect chimpanzees and other primates A comparison of HIV samples from throughout the epidemic Has shown that the virus has evolved in a remarkably clocklike fashion
The theory of endosymbiosis
Proposes that mitochondria and plastids were formerly small prokaryotes living within larger host cells *horizontal gene transfer also contributed to the formation of eukaryotic cells
Hox genes
Provide positional information in the development of fins in fish and limbs in tetrapods ex: evolution of vertebrates from invertebrate animals
ribozymes
RNA molecules that act as catalysts. RNA evolved into DNA molecules because its a more chemically stable mc for genetic information and replicates more accurately
Paralogous genes
Result from gene duplication, so they are found in more than one copy in the genome Can diverge within the clade that carries them, often adding new functions
reproductive handicap
Sexual reproduction produces fewer reproductive offspring than asexual reproduction
principle of maximum likelihood
States that, given certain rules about how DNA changes over time, a tree can be found that reflects the most likely sequence of evolutionary events
ultrametric tree
The branching pattern is the same as in a phylogram, but all the branches that can be traced from the common ancestor to the present are of equal length
frequency-dependent selection
The fitness of any morph declines if it becomes too common in the population
phylogram
The length of a branch in a cladogram reflects the number of genetic changes that have taken place in a particular DNA or RNA sequence in that lineage
parsonious
The most parsimonious tree is the one that requires the fewest evolutionary events to have occurred in the form of shared derived characters Sometimes there is compelling evidence That the best hypothesis is not the most parsimonious
species selection model
Trends may result when species with certain characteristics endure longer and speciate more often than those with other characteristics The appearance of an evolutionary trend Does not imply that there is some intrinsic drive toward a particular phenotype
polytomy
a branch point from which more than two descendant groups emerge. signifies that evolutionary relationships among the taxa are not yet clear.
rooted
a branch point within the tree represents the most recent common ancestry of all taxa in the tree
evolution
a change over time in the genetic composition of a population, descent with modification.
shared derived character
a character shared by a group of species that is not found in their ancestors. It is an evolutionary novelty unique to a clade.
shared ancestral character
a character that originated in an ancestor of the taxon (i.e. backbone)
modern synthesis
a comprehensive theory of evolution that integrated ideas from many other fields.
sexual selection
a form of natural selection in which individuals with certain inherited characteristics are more likely than other individuals to obtain mates
natural selection
a population can change over generations if individuals that possess certain heritable traits leave more offspring than other individuals. a process in which individuals that have certain inherited traits tend to survive and reproduce at higher rates than other individuals because of those traits.
gene pool
a population's genetic makeup, all copies of every type of allele at every locus in all members of the population
sexual dimorphism
a possible result of sexual selection, a difference in secondary sexual characteristics between males and females of the same species (peacock feathers)
horizontal gene transfer
a process in which genes are transferred from one genome to another through mechanisms such as exchange of transposable elements and plasmids, viral infection, and perhaps fusions of organisms.
hybrid zone
a region in which members of different species meet and mate, producing at least some offspring with mixed ancestry.
phylogenetic tree
a representation of the evolutionary history of a group of organisms -starts with biggest, most general, then branches off to more specific (ex: from order to species)
outgroup
a species or group of species from an evolutionary lineage that is known to have diverged before the lineage that includes the species we are studying (the ingroup)
geologic record
a standard time scale that divides earth's history into four eons and further subidvisions.
the bottleneck effect
a sudden change in the environment, such as a fire or flood, may drastically reduce the size of a population, resulting in genetic drift, causes the bottleneck effect. (some alleles get lost completely, others become over expressed, variation is decreased)
biological species concept
according to this concept, a species is a group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring.
maximum parsimony
according to this principle we should first investigate the simplest explanation that is consistent with the facts.
stabilizing selection
acts against both extreme phenotypes and favors intermediate variants
Protobionts
aggregates of abiotically produced molecules surrounded by a membrane or membrane-like structure ex:small membrane-bounded droplets called liposomes can form when lipids or other organic molecules are added to water -Simple reproduction, simple metabolism
molecular clock
an approach for measuring the absolute time of evolutionary change based on the observation that some genes and other regions of genomes appear to evolve at constant rates.
autopolyploid
an individual that has more than two chromosome sets that are all derived from a single species.
homoplasies
analogous structures that arose independently
hardy-weinberg principle
applies to the gene pool of a population that is not evolving, states that the frequencies of alleles and genotypes in a population will remain constant from generation to generation, provided that only Mendelian segregation and recombination of alleles are at work. Such a gene pool is in Hardy-Weinberg equilibrium. p^2 + 2pq + q^2 = 1
prezygotic barriers
block fertilization from occuring- they block species from mating. -habitat isolation -temporal isolation -behavioral isolation -mechanical isolation (reproductive organs dont fit) -gametic isolation (sperm can't fertilize egg)
sexual selection
can also cause sympatric speciation
microevolution
change in allele frequencies in a population over generations
morphological species concept
characterizes a species by body shape
cladistics
common ancestry is the primary criterion used to classify organisms
paraphyletic group
consists of an ancestral species and some, but not all, of its descendants. the most recent common ancestor of its members is part of the group.
postzygotic barriers
contribute to reproductive isolation after the hybrid zygote is formed. -reduced hybrid viability -reduced hybrid fertility -hybrid breakdown
biogeography
darwin's observations about the geographic distribution of species- closely related species tend to be found in the same geographic region, independent evolution, organisms exposed to similar niches have similar evolved characteristics.
genetic variation
differences among individuals in the composition of their genes or other DNA sequences.
neutral variation
differences in DNA sequence that do not confer a selective advantage or disadvantage.
tree of life
divided into three great clades called domains: Bacteria, Archaea, and Eukarya The early history of these domains is not yet clear
Hierarchical Classification from biggest to smallest
domain, kingdom, phylum, class (mammilia), order (canivora), family (feline), genus, species
hypothesis of oparin and haldane
earth's early atmosphere was a reducing (electron-adding) environment, in which organic compounds could have formed from simpler molecules. the energy for this synthesis could have come from lightning and UV radiation. early oceans were like a "primitive soup" of organic molecules.
prokaryotes
earth's first organisms, lived in dense mats and as free-floating individuals.
adaptive evolution
evolution that results when natural selection favors some alleles over others, creating a better match between organisms and their environment.
vesicles
fluid-filled compartments enclosed by a membrane-like structure, could be the bases for protocells. adding clay increases rate of vesicle self-assembly.
Georges Cuvier
french scientist who developed the study of fossils and opposed the idea of gradual evolutionary change. He believed in *catastrophism*, the speculation that teach boundary between strata represents a catastrophe, such as a flood or drought, that destroyed many of the species living at that time.
one of the most important types of mutation in evolution because it increases the number of genes in the genome, providing further opportunities for evolutionary changes
gene duplication
allopatric separation
gene flow is interrupted when a population is divided into geographically isolated subpopulations
sister taxa
groups of organisms that share an immediate common ancestor and hence are each other's closest relatives
clade
groups of species which have a common ancestral spcies
vestigial organs
homologous structures of marginal importance to the organism that are remnants of structures that served important functions in the organism's ancestors.
systematics
how biologists reconstruct and interpret phylogenies, a discipline focused on classifying organisms and determining their evolutionary relationships.
taxonomy
how organisms are named and classified
diploidy
in diploid organisms, a considerable amount of genetic variation is hidden from selection in the form of recessive alleles.
polyphyletic group
includes taza with different ancestors. the most recent common ancestor is not part of the group.
Jean-Baptiste de Lamarck
incorrect mechanism to explain how evolution occurs: use & disuse (the idea that parts of the body that are used extensively become larger and stronger, while those that are not used deteriorate- i.e. giraffe stretch neck to reach high branches) and inheritance of aquired characteristics (an organism can pass modifications made during their lifetime to offspring). He also thought that organisms have an innate drive to become more complex.
intrasexual selection/ mate choice
individuals of one sex compete directly for mates of the opposite sex
adaptations
inherited characteristics of organisms that enhance their survival and reproduction in specific environments.
stromatolites
layered rocks that form when certain prokaryotes bind thin films of sediment together. all such fossils were similar in overall structure and were from shallow marine bays.
sedimentary rocks/ strata
layers of sediment where most fossils are found.
important guys you need to know
linnaeus: binomial nomenclature james hutton: uniformitarianism (the assumption that the same natural laws and processes that operate in the universe now have always operated in the universe in the past) jean baptiste lamark: wrong mechanism for evolution thomas malthus: law of population, population will be checked by famine and disease. (applies to darwin because this means only the fitter organisms survive) georges cuvier: fossil record, catastrophism charles lyell: principles of geology darwin- duh mendel- inheritance alfrad russel wallace- the unlucky bastard who also thought of natural selection but didnt get the credit
earth's first atmosphere
little oxygen, compounds released by volcanic eruptions [nitrogen, CO2, methane, ammonia, and hydrogen], earth cooled causing water vapor to condense into oceans and much of the hydrogen escaped into space.
nucleotide variability
molecular level, little of this variation results in phenotypic variation because many of the differences occur within introns, noncoding segments of DNA lying between exons, the regions retained in mRNA.
variation is caused by
mutation and recombination of alleles in sexual reproduction (more important)
taxon
named taxonomic unit at any level of hierarchy
natural selection is the only mechanism that consistently causes adaptive evolution
natural selection consistently increases the frequencies of alleles that provide reproductive advantage and thus leads to adaptive evolution (not random)
Three major factors alter allele frequencies and bring about most evolutionary change
natural selection, gene flow, genetic drift
conditions for hardy-weinberg equilibrium
no mutations random mating no natural selection extremely large population size (causes geneitc drift: allele frequencies fluctuating by chance from one generation to the next) no gene flow (alleles stay inside the population)
disruptive selection
occurs when conditions favor individuals at both extremes of a phenotypic range over individuals with intermediate phenotypes (ex environment avoring white and black mice over gray ones because there are white and black rocks)
directional selection
occurs when conditions favor individuals at one extreme of the phenotypic range, thereby shifting a population's frequency curve for the phenotypic character in one direction or the other. (mice go from being predominantly tan to predominantly black because its easier to hide from a new predator)
balancing selection
occurs when natural selection maintains two or more forms in a population.
hybrids
offspring that result from an interspecific mating.
descent with modification
organisms share many characteristics, leading Darwin to perceive unity in life. He attributed the unity of life to the descent of all organisms from an ancestor that lived in the remote past. He also thought that as the descendants of that ancestral organism lived in various habitats over millions of years, they accumulated diverse modifications, or adaptations, that fit them to specific ways of life, leading to rich diversity of life.
punctuated equilibria
patterns in fossil record showing periods of apparent stasis punctuated by sudden change. Niles Eldredge and Stephen Jay Gould
adaptive radiations
periods of evolutionary change in which groups of organisms from many new species whose adaptations allow them to fill different ecological roles, or niches, in their communities. occurs after mass extinctions.
half-life
rate of decay, time required for 50% of the parent isotope to decay
basal taxon
refers to a lineage that diverges early in the history of a group
branch points
represent the divergence of two evolutionary lineages from a common ancestor
james hutton
scottish geologist who proposed that Earth's geologic features could be explained by gradual mechanisms current operating in the world (like erosion)
homologies
similarities due to shared ancestry
homology
similarity resulting from common ancestry (same structure, different function)
sympatric speciation
speciation that occurs in populations that live in the same area. factors that can make this happen: polyploidy habitat differentiation sexual selection
endemic species
species that are found nowhere else in the world
parsimony
states that the cladogram implying the least number of changes in character states is the best. efficient. requires the fewest evolutionary events to have occured. the assumption that nature will always take the simplest route possible.
radiometric dating
technique to determine the age of a fossil based on the decay of radioactive isotopes. a radioactive parent isotope decays to a daughter isotope.
stanley miller
tested their hypothesis by creating laboratory conditions
gene variability
the average percentage of loci that are heterozygous
macroevolution
the broad pattern of evolution above the speices level
plate tectonics
the continents are part of great plates of earth's crust that essentially float on the hot, underlying portion of the mantle. movements in the mantle cause the plates to move over time (continental drift.)
relative fitness
the contribution an individual makes to the gene pool of the next generation relative to the contributions of other individuals
adaptive radiation
the evolution of diversely adapted species from a common ancestor upon introduction to new environmental opportunities
phylogeny
the evolutionary history of a species or group of species.
reproductive isolation
the existence of biological barriers that impede members of two species from interbreeding and producing viable, fetile offspring.
gradualism
the idea that profound change can take place through the cumulative effect of slow but continuous processes.
convergent evolution
the independent evolution of similar features in species of different lineages. occurs when similar environmental pressures and natural selection produce similar (analogous) adaptations in organisms from different evolutionary lineages.
cyanobacteria
the main photosynthetic prokaryotic organism for billions of years. began the release of oxygen to the earth's atmosphere, resulting in the extinction of many prokaryotic groups and rise of anaerobic organisms that use cellular respiration.
monophyletic
the only time when a clade and taxon are the same thing. It is a clade consisting of an ancestral species and all of its descendants.
speciation
the process by which one species splits into two or more species
evolutionary adaptation
the result of natural selection- an accumulation of inherited characteristics that enhance organisms' ability to survive and reproduce in specific environments.
phylogenetic species concept
the smallest group of individuals that share a common ancestor, forming one branch on the evolutionary tree.
population genetics
the study of how populations change genetically over time
the modern synthesis
the study of how populations change genetically over time Reconciled Darwin's and Mendel's ideas
gene flow
the transfer of alleles into or out of a poplation due to the movement of fertile individuals or their gametes.
charles Lyell
thoery of uniformitarianism: the same geologic processes that operated in the past continue to operate today at the same rate.
ecological species concept
views species in terms of its ecological niche, the sum of how members of the species interact with the nonliving and living parts of their environment.
the founder effect
when a few individuals become isolated from a larger population and establish a new population whose gene pool differs from the source population. think: they found themselves in another place
polyploidy
when a species originates from an accident during cell division that results in extra sets of chromosomes.
allopolyploid
when an infertile hybrid is able to propagate itself asexually (thus they cant mate with any other species, making them a species of their own)
genetic drift
when chance events cause allele frequencies to fluctuate unpredictably from one generation to the next, especially in small populations *its like if theres only 5 plants, and 3 of them are red, theres a much bigger chance that eventually all the flowers will be red than in a population of 100 plants.
habitat differentiation
when genetic factors enable a subpopulation to exploit a habitat or resource not used by the parent population (ex populations that feed on apple trees vs populations that feed better on lower bushes)
reinforcement
when hybrids are less fit than members of their parent species, natural selection tends to strengthen prezygotic barriers to reproduction.
stability
when hybrids in the zone continue to be produce and survive better than members of either parent species.
heterozygote advantage
when individuals who are heterozygous at a particular locus have greater fitness than do both kinds of homozygous, resulting in balancing selection to maintain two or more alleles at that locus.
analogous structures
when similarities occur because of similar environmental pressures
fusion
when so much gene flow occurs that reproductive barriers weaken further and the gene pools of the two species become increasingly alike unlike they fuse into a single species.
frequency-dependent selection
when the fitness of a phenotype depends on how common it is to the population.
paedomorphosis (think pedo)
when the rate of reproductive development accelerates compared to somatic development The sexually mature species may retain body features that were juvenile structures in an ancestral species
polymorphism
when two or more clearly different phenotypes exist in the same population of a species