Test 1 Flashcards
Fitness
Ability to survive and reproduce (pass on ones genes)
What leads to adaptive evolutionary change?
Natural selection
Selective advantage
Individuals that survive and produce fertile offspring
Natural selection acts on:
Phenotype
Polygenic control
Many plant and animal characteristics are controlled by more than one gene
Three kinds of selection which cause changes in the normal distribution:
- Stabilizing
- Directional
- Disruptive
Stabilizing selection
Selects against phenotypic extremes, favors individuals with average phenotypes (Human birth weights)
Directional Selection
When an environment changes, phenotypes at one extreme of the normal distribution are favored (Allele favored must already be present in the population)
ex. Peppered moths
Disruptive Selection
Extreme changes in the environment may favor two or more different phenotypes
(Very rare, selects against the average phenotype)
Results in a divergence of distinct groups of individuals within a population
Geographic variation
Genetic differences among different populations within the same species, such as a cline
Cline
Gradual change in a species phenotype and genotype through a series of geographically separate populations as a result of an environmental gradient
(Common among species with continuous ranges over large geographic areas)
Population genetics
The study of genetic variability within a population and of the evolutionary forces that act on it
Allele
Alternative forms of a gene located at a specific location on a specific chromosome
How is it possible to estimate the amount of observed variation that is genetic?
By the number, frequency, and kinds of alleles in a population
Population gene pool includes
All the alleles for all the loci present
Diploid
Two alleles at each genetic locus
How is evolution of populations described?
Genotype, phenotype, and allele frequency
Genotype
Genetic makeup, or combination of alleles, in an individual
Allele frequency
Fraction of all chromosomes in the population that carry that allele
The sum of all genotype frequencies equals
one
The Hardy-Weinberg Principle
Frequencies of alleles and genotypes in a population do not change from generation to generation unless influenced by outside factors
Genetic equilibrium
A population with no net change in allele or genotype frequencies over time
Evolution is occurring if ____ are changing of time
Allele frequencies
p^2
Frequency of AA
Q^2
Frequency of aa
2pq
frequency of Aa
Genetic equilibrium exists only when five conditions are me
- Random Mating
- No net mutations
- Large population size
- no migration
- no natural selection
Microevolution
Refers to relatively small generation to generation changes in allele or genotype frequencies within a population
Five microevolutionary processes
- nonrandom mating
- mutaiton
- genetic drift
- gene flow
- natural selection
Inbreeding increases:
Frequency of homozygous genotypes
Inbreeding depression
Inbred individuals have lower fitness than those not inbred
Assortative mating
Individuals select mates by their phenotypes
Positive assortative mating
Selection of mates with the same phenotype
Negative assortative mating
Selection of mates with different phenotype
Genetic drift
Random evolutionary changes in small breeding populations results in changes in allele frequencies in a population
Genetic drift decreases
Genetic variation within a population but increases genetic differences among different populations
Bottlenecks
Occasionally a population may rapidly and severely decrease due to disease, exploitation, or sudden environmental change
Genetic drift can occur in a small population of survivors causing many allele frequencies to differ from those proceeding the decline
Founder effect
Genetic drift tat results when a few individuals from a large population found a new colony
Gene flow counteracts
The effects of natural selection and genetic drift
Taxonomy
The science of naming, describing, and classifying organisms
Who founded modern taxonomy?
Carl Linnaeus
Morphological species concept
The classification of plants and other organisms into separate species based on their visible structural differences such as feathers or number of flower parts
Binomial nomenclature
Gives each species a name made up of two words ( in latin):
Genus species
Genus
First epithet (capitalized)
Species
Second epithet (lowercase)
The Biological species concept
A species consists of one or more populations whose members interbreed in nature to produce fertile offspring and do not breed with members of other species
When do new species evolve?
When populations become reproductively isolated from one another
Who first expressed the biological species concept?
Ernst Mayr
Shortcomings of BSC
- Applies only to sexually reproducing organisms
- Does not apply to bacteria, or extinct organisms
- Individuals assigned to different species sometimes do successfully interbreed
The phylogenetic species concept
A population is declared a separate species if it has undergone evolution long enough for statistically significant differences in diagnostic traits emerge
(Testable by comparing gene sequences between two groups)
Shortcomings of PSC
- Requires thorough studies of DNA sequencing
2. Many subspecies would become separate species
Prezygotic Barriers
Reproductive isolating mechanisms that prevent mating or fertilization from taking place
Types of prezygotic barriers
Temporal isolation habitat isolation behavioral isolation mechanical isolation gametic isolation
Temporal isolation
Two groups reproduce at different times of the day, season, or year
Habitat Isolation
Two closely related species in the same geographic area live and breed in different habitats in that area
Behavioral Isolation
Sexual Isolation
Species-specific courtship behaviors
Mechanical Isolation
Structural differences in reproductive organs prevent successful mating between species
Gametic Isolation
If mating takes place, molecular and chemical differences between species prevents fertilization
Postzygotic Barriers
Fertilization occurs between gametes of two closely related species despite their prezygotic barriers
Generally, the embryo of an interspecific hybrid spontaneously aborts
Speciation begins when?
When a population becomes reproductively isolated from other populations and their gene pools diverge
Allopatric Speciation
Speciation that occurs when one population becomes geographically isolated from others of the species and evolves by natural selection and/or genetic drift
Sympatric
Speciation between two populations in the same geographic range
When does sympatric speciation occur?
When reproductive isolating mechanisms evolve at the start of the speciation process
How does sympatric speciation occur?
In two ways:
A change in ecology or in ploidy
Polyploidy
Having more than two sets of chromosomes
Autopolyploid
The chromosome complement consists of more than 2 copies of homologous chromosomes (from the same species)
Allopolyploid
The chromosome complement consists of more than 2 copies of chromosomes derived from different species
When does allopolyploidy occur?
When two species mate to produce a hybrid species
How does autopolyploidy arise?
By the fusion of gametes of the same species
How does allopolyploidy arise?
By the fusion of gametes of the different species
What does autopolyploidy consist of?
Homologous chromosome sets
What does allopolyploidy consist of?
All chromosome sets are not homologous
What causes autopolyploidy?
Mainly caused by nondisjunction of chromosomes
What causes allopolyploidy?
Mating of different species
Allopolyploidy gametes have a _____ # of chromosomes from either parent
Different number of chromosomes
Outcomes of allopolyploids
- New species outcompeted by established species (bcomes extinct)
- New species may coexist with both parental species
- New species may outcompete and replace parental species
Hybrid Zone
An area of overlap between two recently diverged populations in which interbreeding takes place and hybrid offspring are common
Three possibilities within hybrid zones:
- Reinforcement (Hybrids are less fit than parental species)
- Fusion (Just as fit)
- Stability (More fit)
Two models of evolution based on observed fossil record
- Punctuated equilibrium
2. Phyletic gradualism
Punctuated equilibrium
Long periods of stasis are interrupted by short periods of rapid speciation (perhaps triggered by changes in the environment)
Phyletic Gradualism
Evolution proceeds continuously over long periods
Macroevolution
Large-scale phenotypic changes in populations at the species level and higher such as new species, genera, families, orders, classes, phyla, kingdoms, and domains
Adaptive Radiation
The evolutionary diversification of many related species from one or few ancestral species in a relatively short period
May occur when species are able to exploit numerous new ecological opportunities
Adaptive Zones
New or vacant ecological niches that were not exploited by an ancestral organism
(Vacant adaptive zones are more common on islands than continents)
Four requirements for chemical evolution
- Little or no free oxygen
- A source of energy
- Availability of chemical building blocks
- Time
Two hypothesis explaining the formation of organic molecules
- Prebiotic soup hypothesis
2. Iron-sulfur world hypothesis
Prebiotic soup hypothesis
Proposes that organic precursors formed near earths surface
Iron-sulfur world hypothesis
Proposes that organic precursors formed at cracks in the oceans floor
Microspheres
A type of protobiont formed by adding water to abiotically formed polypeptides
Stromatolites
Composed of many minute layers of microbial biofilms
Another type of fossil evidence of early cells
Cyanobacteria were first to obtain…
Hydrogen electrons by splitting water
Serial endosymbiosis
Suggests that early eukaryotic cells were assemblages of formerly free-living prokaryotes
Endosymbionts may have been ___ not ___
Ingested not digested
Earths history is divided into
eons, eras, and epochs based on major geologic, climate and biological events
Life originated during the
Archaean eon (4.6-2.6 bya)
Paleozoic Era
542-251 mya
Cambrian Ordovician silurian devonian carboniferous permian
The Cambrian Period
During cambrian radiation evolution was rapid, with the sudden appearance of many new animal body plants
The Devonian Period
Explosive radiation of fishes with jaws (The Age of Fishes)
Amphibians, wingless insects, and all major plant groups but flowering plants also originated during this time
Carboniferous Period
Amphibians underwent an adaptive radiation and became the dominant carnivores in terrestrial ecosystems
Reptiles, cockroaches and dragonflies appear
Permian extinction (Mass Extinction)
Between the permian and triassic periods (251 mya)
more than 90% of marine species and 70% of vertebrate genera living on land became extinct
Dinosaurs went extinct
At the end of the cretaceous period (66 mya)
When did Human ancestors appear?
In Africa during the late Miocene and early Pliocene epochs
When did Genus Homo appear?
Approximately 2.5 mya
A mass extinction of large mammals at the end of the Pleistocene coincided with the appearance of human hunters
Paleoanthropology
The study of human evolution
Paleo=ancient; Anthropos=human
The first primates descended from what?
Small, shrewlike placental mammals that lived in trees and ate insects
When did the first primates appear?
By the early Eocene
Large brain is associated with
Increased sensory input, intelligence, and socialization
Arboreal adaptation
Long, Slender limbs that rotate freely at the hips and shoulders, stereoscopic vision
Hominoids
A group composed of apes and hominins
Five genera of hominoids in existence today
Gibbons Orangutans gorillas chimpanzees humans
Homo erectus probably evolved from
Homo ergaster
The church insists on
the special creation of mans soul
The Catholic faith obliges us to hold that
Sould are immediately created by God
The church allows for the possibility that man’s body
Developed from previous biological forms
Biodiversity
The variety of living organisms and the ecosystems in which they belong
Systematics
The scientific study of the diversity of organisms and their evolutionary relationships
Classification
Arranging organisms into groups based on similarities that reflect evolutionary relationships among lineages
Taxon
A formal grouping of organisms at any given level
Taxonomic Levels
Species Genus Family Order Class Phylum Kingdom Domain
The Three Domains
Archaea
Bacteria
Eukarya
Cladogram
A type of phylogenetic tree in which each branch represents a clade
Clade
A group of organisms with a common ancestor
Node
Branching points
Represents the divergence of two or more new groups from a common ancestor
Root
Represents the most recent common ancestor of all the clades depicted in the tree
Phylogeny
The evolutionary history of a group of organisms from a common ancestor
Homology
The existence of shared ancestry between a pair of structures or genes in different taxa
Reversal
A trait reverts to its ancestral state
Homoplasy
The development of similar looking structures by the result of adapting to similar environments through convergent evolution
Shared Ancestral Characters
Features that were present in an ancestral species and remain present in all groups descended from that ancestor
Shared Derived Characters
Novel traits that evolve when two populations separate and begin to evolve independently
Characters that originate in a recent common ancestor and are present in its descendants
Molecular Systematics
Focuses on molecular structure to clarify evolutionary relationships
Macromolecules that are functionally similar in two different types of organisms are considered homologous if…
Their subunit sequence is similar
___ Have been extensively used to determine evolutionary relationships among bacteria
rRNA
rRNA analysis has suggested ___ are more closely related to ___ than to ___
Fungi are more closely related to animals that to plants
Cladograms show three types of taxonomic relationships
- Monophyletic groups
- Paraphyletic groups
- Polyphyletic groups
Monophyletic group
Includes an ancestral species and all its descendants
Defined by shared derived characters
Sister taxa share the most recent common ancestor on a cladogram
Paraphyletic Group
Contains a common ancestor and some, but not all, of its descendants
Shares ancestral characters
Polyphyletic Group
Consists of several evolutionary lines that do not share the same recent common ancestor
Unnatural grouping that misrepresent evolutionary relationships
Out-group Analysis
Used to estimate which attributes are shared derived characters in a given group of organisms
Outgroup
A taxon considered to have branched off earlier than the taxa under investigation, the ingroups
An ideal out-group is the in-groups
Sister taxon
Valid monophyletic group
All members share at least one derived character
Each branch reflects the addition of…
One or more shared derived characters
Principle of Parsimony
Use the simplest explanation to interpret the data when choosing between multiple, competing cladograms
Prokaryotic domains
Archaea and Bacteria
Cocci (coccus)
Spherical
Cocci description
Occur singly, in groups of twos, in long chains, or clumps
Bacilli (Bacillus)
Rod-shaped
Bacilli description
Occur as single rods or long chains of rods
Spirochete or spirillum
Spirals
Flexible or rigid
Spirochete description
A comma-shaped spirillum is a vibrio
Cell wall
Around the plasma membrane supports bacterium and keeps the cell from bursting under hypotonic conditions
Peptidoglycan
A complex polymer consisting of two amino sugars linked with short polypeptides, to form a single macromolecule that surrounds the entire plasma membrane
Peptidoglycan is absent in the ___ cell wall
Peptidoglycan is absent in the archaean cell wall
Structurally the wall is necessary for:
- Maintaining shape
- Countering the effects of osmotic pressure
- Providing attachment sites for bacteriophages
- Providing a rigid platform for surface appendages
Gram-Positive
Absorb and retain crystal violet stain
Has a thick peptidoglycan layer
Gram-negative
Do not retain the stain
Have an outer membrane and a thin peptidoglycan layer
Lipid portion contains LPS
Bacteria also use ___ to attach to surfaces such as rocks, plant roots, or human teeth (dental plaque)
Capsules
Bacteria use ___ and ___ to attach to cell surfaces or to each other
Fimbriae and pili
Fimbriae
Are hundreds of hairlike appendages made of protein
Pili
Appendages that are longer (and fewer) than fimbriae
Sex Pili
Help transmit DNA between bacteria
Endospores
Dormant, extremely durable cells
____ Do not form endospores
Archaea
Three parts of a bacterial flagellum
- basal body
- a hook
- a single filament
Binary fission
One cell divides into two similar cells in which circular DNA replicates, then an ingrowth of plasma membrane and the cell wall forms a transverse wall
Budding
A cell develops a bulge (bud) that enlarges, matures, and eventually separates from the mother cell
Fragmentation
Walls develop within the cell, which then separates into several new cells
Vertical gene transfer
Transfers genetic material from parent to offspring
Horizontal gene transfer
Transfers genetic material to another organism that is not its offspring
Three different mechanisms for gene transfer
- Tranformation
- Transduction
- Conjugation
___ and ___ are important sources of genetic variation for diversification and adaptation
Horizontal gene transfers and genetic recombination
Autotrophs
Use inorganic compounds to manufacture organic molecules
Heterotrophs
Obtain carbon atoms from organic compounds made by other organisms
Chemotrophs
Obtain energy from chemical compounds
Phototrophs
Captures energy from light
Nitrification
Conversion of ammonia to nitrite and nitrite to nitrate (a form that can be used by plants and fungi)
Archaea have no ___ in cell walls or ____
Peptidoglycan in cell walls or simple RNA polymerase
Ester Linkages
Occur in PM of eukaryotes and bacteria
Ether linkage
Occur in PM archaea
Archaea inhabit ___ Environments
Harsh Environments
Two major phyla of Domain Archaea
Crenarchaeota and Euryarchaeota
Crenarchaeota
Consist mainly of extreme thermophiles, which require very high or very low temperature for growth
Euryachaeota
Methanogens, extreme halophiles and extreme thermophiles
Methanogens
inhabit oxygen-free environments
Mutualism
Both partners benefit
Commensalism
One partner benefits and the other is neither harmed nor helped
Parasitism
One partner lives on or in the other
the parasite benefits and the host is harmed
Biofilms
Communities of micro-organisms consisting of many species of bacteria, and may include other organisms such as archaea, fungi, and protozoa
