EXAM1 [ch. 18, 19, 20] Flashcards
(141 cards)
1
Q
- broad, well supported explanation with rich predictive value
- based on natural phenomena and causes
- stands up to experimental tests
A
Scientific theory
2
Q
- the change in organisms throughout earth’s history
- descent with modification
- a change in genetic composition of a population from generation to generation
- individuals don’t, but populations do
A
Evolution
3
Q
Today’s life is different from and descended from earlier life
A
Descent with modification
4
Q
- antiquity through 1600’s
- fixed ideal species
- scala naturae (ladder of nature)
A
Aristotle (384-322 BC)
5
Q
- botanist
- orderly, nested classification system
- binomial naming
- age of reason (1700’s - 1800’s)
- Father of Taxonomy
A
Carl Linnaeus (1707-1778)
6
Q
- geologist
- slow, continuous process ⇒ geological features
- gradualism
A
James Hutton (1726-1797)
7
Q
- aka: Father of Geology
- uniformitarianism
- “Principles of Geology” (which was read by Darwin)
A
Charles Lyell (1797-1875)
8
Q
- expanded off of Hutton’s ideas
- same geologic processes in past as today
- rate of change today = rate of change in the past
- thus, the earth is very old
A
Uniformitarianism
9
Q
- wrote ideas that “forms minute” slowly acquired complexity over time
- Charles Darwin grandfather
A
Erasmus Darwin (late 1700’s)
10
Q
- naturalist
- linked evolution to adaptation
- extinct species have been replaced by descendants with new features (these adaptations helped them survive in environment)
- Darwin agreed with these ideas
A
Jean-Baptiste Lamarck (1744-1829)
11
Q
an inherited feature that helps an organism’s survival and reproduction in its present environment
A
Adaptation
12
Q
- Theory of inheritance of “acquired” characteristics through “use and disuse”
- if an organism changes during life in order to adapt to its environment, the changes are passed to its offspring
- Darwin rejected these ideas
A
“Lamarckism”
13
Q
- 1858, wrote to Darwin with same ideas about natural selection from his work in Malay Archipelago
- presented scientific papers on natural selection with Darwin before the Linnean Society
A
Alfred Wallace (1823-1913)
13
Q
- naturalist on HMS Beagle (1831-1836)
- travelled mostly to South America (+ Galapagos Islands)
- collected plants, wildlife, fossils
- observed species’ geographic locales and adaptations
- studied local geology
A
Charles Darwin exploration
13
Q
- developed evolution theory
- wrote “Origin of Species” in 1859
A
Charles Darwin
14
Q
- written by Darwin in 1859
- two main ideas: descent with modification and natural selection
A
“Origin of Species”
14
Q
- natural selection is the mechanism for evolution
- heritable variation exists in most species
- all species produce more offspring than the environment can support (based off Mathlthus’s work)
- but, many offspring die off before maturity
A
[Part 2] Darwin’s Theory: natural selection
14
Q
- unequal reproductive success among individuals (those with the best traits leave more offspring than others
- those heritable, favorable traits (adaptations) accumulate over vast time, matching the species to its environment
A
Natural selection inferences
14
Q
- all present life is related through descent with modification from a common ancestor in the past
- that evolution isn’t a totally new idea
- Earth’s many species are descendants of ancestral species that were different from the present-day species
A
[Part 1] Darwin’s Theory: Descent with modification
15
Q
- individuals in a population vary in their heritable characteristics
- organisms produce more offspring than the environment can support
A
Darwin’s natural selection observations
16
Q
- individuals that are well suited to their environment tend to leave more offspring
- over time, favorable traits accumulate in the population
A
Darwin’s natural selection inferences
17
Q
- explains both diversity & unity of life
- accounts for much of form and function
- can predict outcome of environmental change
- genetic variation is essential/a prerequisite
A
Theory of Evolution by Natural Selection
18
Q
antibiotic-resistance in bacteria
A
Natural selection in action
19
Q
- origin of life
- how variation works
- how inheritance works
- why variation still exists
- “sudden” changes in fossil record
- source of totally “new” characters
A
NOT explained in Darwin’s theory
20
- fossil record
- homology
- convergence
- biogeography
- molecular biology
Evidence of evolution
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- forms related by common ancestry
Homology
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- structures derived from a common ancestor (but possibly modified for different functions)
- similar structures due to evolutionary origin & based on genetics and developmental origin
-not common structures, but common ancsetor
Homologous Structures
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- remnants of ancestral (homologous) structures with no present adaptive function
- ex: blind cave salamanders have eyes (why? because [inference] they descended from a species that could see)
Vestigial structures
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- unrelated species have similar adaptations under similar environmental conditions
- _______ evolution: natural selection acted the same way under same conditions (the independent evolution of similar features (analogous) in different lineages)
- ex: torpedo shape for swimming
Convergence
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- a result of convergent evolution
- similar functions, but not a common ancestor
- similarities occur because similar selection pressures
- similar phenotypes will evolve in distantly related species due to the same evolutionary pressures
- similar structures due to functional or ecological constraints/pressures and characters can be very similar in appearance due to evolutionary convergence
- ex: white coat (fox & bird)
Analogous Structures
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- distribution of species
- corresponds to geographic history
Biogeography
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- DNA analysis supports evolution
- closely related organisms have similar DNA
- evolution of new functions for proteins after mutations
- mutation→DNA→segment/DNA sequence→gene→protein(s)
- DNA→mRNA→protein
- the more amino acid sequences shared, the more closely related
Molecular biology
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create changes in DNA
Mutations
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most diverse (holds basically everything; is 1st in classification system)
[Nested classification system] Domain
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most exclusive/specific grouping
[Nested classification system] Species
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scientific naming
- GENUS SPECIES
- genus is capitalized
- italicized
- have genus underlined and species underlined but not underlines together!
(- if applicable, subspecies are the absolute most specfic)
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Taxonomy
- the science of classifying (or naming) species
- grouping or classifying species together based on similarities and differences (subjective)
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Survival of the fittest
- natural selection
- the reproduction of individuals with favorable genetic traits that survived environmental change because of those select traits.
- leads to evolutionary change
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Phylogenetic trees
diagrams used to reflect evolutionary relationships among organisms or groups of organisms
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Allele
- gene variants that arise by mutation and exist at the same relative location on homologous chromosomes
- one of a number of alternative forms of a DNA sequence at a particular locus
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Locus
the specific physical location of a gene on a chromosome
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Morphology
the study of the size, shape, and structure of animals, plants, and microbes and of the relationships of their constituent parts
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Gene pool
- the sum of all the genes (+alleles) in a population
- many genes have "fixed" alleles (homozygous in all individuals)
- other genes: 2 or more alleles
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Zygote
fertilized egg (2n (diploid) = 46)
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Fertilization
the union of two gametes (sperm + egg fuse to form a zygote)
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Prezygotic barriers
- BLOCKS reproduction
- temporal, habitat, behavioral, gametic, and mechanical isolation
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Temporal Isolation
- keeps different species different because of breeding schedules
- prezygotic barrier
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Habitat (egological) isolation
- species don't breed due to distance (they don't meet)
- prezygotic barrier
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Behavioral isolation
- behaviors that impact reproduction
- ex: courtship cues, mating calls/dances/rituals
- prezygotic barrier
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Gametic isloation
- sperm of one species might not be able to fertilize an egg from another species (gametes can't fuse)
- prezygotic barrier
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Mechanical isloation
- when mating is impossible due between different animal species due to the incompatibility of their sexual organs
- prezygotic barrier
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Postzygotic Barriers
- occurs after a hybrid zygote formation
- hybrid inviability, sterility, and breakdown
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Hybrid Inviability
- embryo is formed but can not survive development
- postzygotic barrier
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Hybrid sterility
- different species produce viable offspring the can not reproduce
- postzygotic barrier
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Hybrid breakdown
- second generation hybrids that can produce
- postzygotic barrier
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Strain
a genetic variant within a biological species
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What must be true of any organ that is described as vestigial?
it must be homologous to some feature in an ancestor
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Niche
Encompasses both physical and environment the organism requires (temperature, terrain) with the interactions it has with other species
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Adaptive Radiation
- process where organisms diversify rapidly from an ancestral species into a multitude of new forms due to change in the environment making new resources, niches, etc. available
- because many adaptions evolve from a single point of origin; thus causing the species to radiate into several new ones
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Hybrid zones
- may exist during allopatric speciation
- areas where two closely related species interact and interbreed
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Fitness
reproductive success and reflects how well an organism is adapted to its environment
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With fusion..
..the reproductive barriers weaken and gene flow can occur; hybrids are equally as fit as parents
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Sympatric Speciation
- Chromosomal error during cell division
- most common in plants
- speciation occurs in the same geographical area
- other factors create an isolated gene pool
- very rare process (esp. in animals)
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Polyploidy
- a condition where a cell or organism has an extra set or extra sets of chromosomes
- results from an error in meiosis, all move to one cell instead of separating
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Species
- group of organisms that can interbreed and produce viable, fertile offspring
- not based on similarity of appearance (variation within the same)
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Speciation
formation of two species from one original species
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A new species arises when..
.. the genetics in two populations become different enough that it prevents gene flow between populations
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Gene Flow
the movement of alleles across a species' range
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Biological Species Concept
- organisms that are reproductively isolated from each other are different species
- members of the same biological species share the same gene pool (there is gene flow between two populations)
- are reproductively isolated from other species by natural biological barriers
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Morphological Species Concept
- organisms that have significant morphological and anatomical differences are different species
- ex: sorting birds into species based on their wingspans and beak size
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Biological reproductive barriers
- Prezygotic
- Postzygotic
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How many genes are responsible for reproductive isolation features?
- may be many genes, but could also be as few as one
- ex: variation in one gene keeps 2 snail species from mating (shells spiral in different directions)
- mechanical isolation
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Issues with biological species concept
- fossil species
- asexual species
- sometimes hybrids do happen
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Allopatric Speciation
- speciation can occur when groups isolated geographically for long time
- physical barrier isolated one population
- not only physical barriers cause speciation: changes (mutations) over time or natural selection, etc. lead to the groups that are no longer reproductively compatible
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Dispersal
when a few members of a species move to a new geographical area
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Vicariance
when a natural situation arises to physically divide organisms
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Possible outcomes of hybrid populations
- reinforcement
- fusion
- stability
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(hybrid populations) Reinforcement
- hybrids are less fit than either purebred species
- the species continue to diverge until hybridization can no long occur
- reproductive barriers should be strong
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(hybrid populations) Fusion
reproductive barriers weaken until the two species become one
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(hybrid populations) Stability
fit hybrids continue to be produced
- hybrids survive or reproduce better then either parents species
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Aneuploidy
- results when the gametes have too many or too few chromosomes due to nondisjunction during meiosis
- the resulting offspring will have 2n+1 or 2n-1 chromosomes
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Rates of Speciation
- gradual speciation
- punctuated equilibrium
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Gradual Speciation
- species diverge gradually through time with small steps
- a rate of speciation
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Punctuated equilibrium
- species exhibit a large change in a relatively short period of time followed by long periods of stasis
- a rate of speciation
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Population
a group of individuals of the same species that live in the same area and interbreed, producing fertile offspring
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misconception: Individuals evolve during their lifetimes
Fact: natural selection acts on individuals, but only populations evolve
- genetic variation in population makes evolution possible (variation in heritable traits is a prerequisite for evolution)
- only genetically determined variation can have evolutionary consequences
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Phenotypic varation
mostly genetic, but environment can influence expression, creating non-heritable variation
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Sources of genetic variation
- new genes and alleles can arise by mutation or gene duplication
- sexual reproduction can result in genetic variation by recombining existing alleles (crossovers, independent assortment, random fertilization)
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Genotypic frequency
- % (proportion) of each genotype in the population
- %AA %Aa %aa
- genotype divided by population
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Allelic frequency
- % of each allele in the population
- %A allele and %a allele
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Microevolution
- a change in allele frequencies in a population over generations
- an evolving population is one that is showing genetic change over generations
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Population genetics
the study of what changes the allele frequencies in populations
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3 mechanisms that cause allele frequency changes
- natural selection (only causes adaptive evolution)
- genetic drift
- gene flow
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Hardy-Weinburg equilibrium
- IF a large population reproduces sexually at random, THEN the genetic frequencies should not change in next generation (remains in equilibrium)
- same frequency of alleles and genotypes in next generation
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H-W equilibrium Conditions
1. no mutations
2. mating is random
3. no selection (equal survival)
4. very large population size
5. no gene flow in or out
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H-W Equation
- p + q = 1
- p^2 + 2pq + q^2 = 1
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Variables for H-W Equation
- p = freq. dominant allele
- q = freq. recessive allele
- p^2 = freq. of homozygous dominant genotype
- 2pq = freq. of heterozygous genotype
- q^2 = freq. of homozygous recessive genotype
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Mechanisms of microevolution
1. natural selection
2. genetic drift (founder effect, bottleneck effect)
3. gene flow
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(Mechanisms of microevolution) Natural selection
- acts non-randomly on phenotypes of individuals
- changes allelic and genotypic frequencies of populations non-randomly
- always leads to adaptation of population to current environment
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(Mechanisms of microevolution) Genetic drift
- genetic frequency changes due to random events
- often occurs in small populations (ex: sampling errors in stats)
- random changes in allele frequency in either direction
- often reduces genetic diversity
- one allele may become "fixed" (all other alleles lost)
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(Mechanisms of microevolution) Founder effect
- a few of one species start new isolated population
- new gene pool differs from original source
- small population size lead to more drift
- better alleles may be lost
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(Mechanisms of microevolution) Bottleneck effect
- an event drastically cuts population size
- gene pool of survivors is random; some alleles are lost
- more genetic drift
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(Mechanisms of microevolution) Gene flow
- alleles move in/out of population
- includes migration of adults & dispersal of gametes, seeds, larvae
- results to add genetic diversity to population and tends to reduce genetic differences between populations
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Outcomes of natural selection on a population depend on?
- relative fitness
- forms of natural selection
- sexual selection
- limitations of natural selection
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Relative Fitness
- fitness is relative to other individuals in the population
- "fittest" had the best reproductive success
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Forms of natural selection
- Directional selection
- diversifying selection
- stabilizing selection
- frequency-dependent selection
- sexual selection
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Directional selection
- form of natural selection
- selects phenotypes at one end of the spectrum of existing variation
- shifts the population's genetic variance toward the new, fit phenotype
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Diversifying selection
- form of natural selection
- intermediates are less fit than extremes
- maintains diversity
- increases genetic variance
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Stabilizing selection
- form of natural selection
- intermediate types more fit than extremes
- decreases genetic variance
- higher death rate selects against low birth size, higher death rate selects against large birth size
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Frequency-Dependent selection
- form of natural selection
- the fitness of a phenotype depends on how common it is in the population
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Sexual selection
- form of natural selection
- success based on traits related to obtaining mates (not directly related to environment)
- leads to sexual dimorphism
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Intrasexual selection
individuals of one sex compete directly for mates of the opposite sex
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Intersexual selection
also called mate choice, individuals of one sex (usually females) are choosy in selecting their mates from the other sex
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Phylogeny
the evolutionary history of a species and its relationship to other species (shown as a tree)
110
Types of phylogenetic trees
- rooted: single lineage (at base) represents common ancestor
- unrooted: show relationships but not a common ancestor
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3 Domains of life
- bacteria (cells do not contain nucleus)
- Archaea (cells do not contain nucleus; they have a different cell wall from bacteria)
- Eukarya (cells do contain a nucleus; include the plants, animals, fungi, and protists)
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(rooted phylogenetic tree) Root
indicated that an ancestral lineage gave rise to all organisms on the tree
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(rooted phylogenetic tree) Branch point
indicated where two lineages diverged
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(rooted phylogenetic tree) basal taxon
a lineage that evolved early and remains unbranched (think outgroup)
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(rooted phylogenetic tree) Sister taxa
when two lineages stem from the same branch point
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(rooted phylogenetic tree) Polytomy
A branch with more than two lineages
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Systematics
the study of phylogenetic relationships
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(parts of a phylogenetic tree) Taxon
taxa (plural); group(s) of organisms (species, family, domain, etc. )
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(parts of a phylogenetic tree) Clade
a grouping that includes a common ancestor and all the descendants (living and extinct) of that ancestor (monophyletic groups) (ex: all the species on a branch)
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Cladistic analysis
- grouping organisms in a way the reflects their evolutionary relationship
- Monophyletic group (clade)
- paraphyletic group
- polyphyletic group
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Monophyletic group
consists of an ancestral species and all of its descendants
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Paraphyletic group
consists of an ancestral species and some, but not all, of its descendants
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Polyphyletic group
consists distantly related species but does not include their most recent common ancestor
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Binomial Nomenclature
- aka: specific name
- by Carl Linnaeus (1800's)
- genus (group) + "specific epithet"
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Advantages of phylogenetic classification over Linnaean classification [tree over ladder]
- tells evolutionary history
- does not "rank" organisms and does not suggest that 2 identically ranked groups are comparable
- Linnaean classification "ranks" groups of organisms artificially into kingdoms, phyla, orders, etc.
126
Cladistics
- method of determining phylogeny or method of hypothesizing relationships among organisms
- analysis depends on characters (anatomical or physiological or behavioral or genetic sequences
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Genotype
the genetic constitution of an individual organism
128
Phenotype
the set of observable characteristics of an individual
129
Gene duplication
any duplication of a region of DNA that contains a gene
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Crossovers
during meiosis, homologous chromosomes trade some of their alleles by crossing over
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Independent Assortment
the alleles of two (or more) different genes get sorted into gametes independently by one another (gene variants = alleles)
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Fixed allele
an allele that is the only variant that exists from that gene in a population
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Homozygote
an individual having 2 identical alleles of a particular gene
134
Heterozygote
an individual having 2 different alleles of a particular gene
135
Adaptive evolution
natural selection selects the most beneficial alleles and this increasing their frequency in the population, while it selects against deleterious alleles
136
Outgroup
a more distantly related group of organisms that serves as a reference group when determining evolutionary relationships of the ingroup
