BIOL 1P92 Midterm
Evolution
- heritable change in one or more characteristic of a population or species from one generation to the next
Macroevolution vs microevolution
Macro: viewed on a larger scale
- formation of a new species or groups of related species
Micro: viewed on a small scale
- changes in a single gene or allele frequencies in a pop. over time
Species
- group of related organisms that share a distinctive form
Population:
all members of the same species that live in the same area at the same time and have the opportunity to interbreed
T/F: If they cannot produce viable offspring they are not considered part of the same species
TRUE
Who are four of the scientists who set the stage:
John Ray:
Carl Linnaeus:
George Buffon:
Jean-Baptiste Lamarck:
Who is another scientist who set the stage: *____ Darwin (not Charles)
- Erasmus Darwin
- an early advocate of evolutionary change and suggested life on Earth could have descended from a common ancestor
- made many observations based on selective breeding practices ("Artificial cultivation")
What is the Uniformitarianism hypothesis:
- from geology
- slow geological processes lead to substantial change
What is Catastrophism:
- which fit with religious teachings
- earth is 6,000 years old and only catastrophic events have changed its geological structure
Charles Darwin: What was his nationality, when was he born, what theory did he play a central role in
- British
- naturalist
- 1809
- central role in developing the theory that existing species have evolved from pre-existing species (natural selection)
- voyage on HMS Beagle from 1831-1836
- Galapagos finches
T/F: Papers by Darwin and Wallace both published, but were not well recognized
- TRUE
- went against religious teachings
What is one of the most important contributions to our understanding of biology
- On the Origin of Species (1859)
Who said: "The theory of descent with modification through variation and natural selection"
Charles Darwin
Evolution occurs from generation to generation due to two interacting factors:
1. Variation: in traits that occur among individuals and are heritable from parents to offspring
2. Natural Selection: individuals with traits that make them better suited to the environment flourish and reproduce, while others are less likely to survive and reproduce
(favourable traits become more prevalent in a pop. over time)
Genetic variation is an ___________ force in evolution as it allows natural selection to __________ or ____________ frequency of alleles ___________ in the population
Genetic variation is an important force in evolution as it allows natural selection to increase or decrease frequency of alleles already in the population
How is genetic variation advantageous to a population:
- it enables some individuals to adapt to the environment while maintaining the survival of the population
- caused by mutation:
- Random mating, random fertilization, and recombination between homologous chromosomes during meiosis
Spirit Bears example: Recessive mutation in the Melanocortin 1 Receptor gene
- Picture of a black fur bear and a white fur bear (but BOTH are black bears)
- The 'white' bear has a mutation in the melanocortin 1 receptor gene
- The likelihood of a spirit bear arising is quite rare -but might be more likely if there was more snow, because then the white fur would be an advantageous trait to have
Evolutionary Adaptation by natural selection example: Peppered Moths
- in england
- Coal burning, soot in the air that settles on trees
- Originally the peppered moths were majorly white although there was a few darker ones
- When the trees turned dark the white moths were eaten more by the birds
- Gradual shift to dark moths
Lamarckian vs. Darwinian views of evolution:
While both Lamarck and Darwin proposed theories of evolution, the key difference lies in how they believed traits were acquired and passed on:
Lamarck believed organisms could develop traits during their lifetime based on environmental needs and pass those "acquired characteristics" to their offspring EX.) STRETCHING OF TRUNKS
Darwin's theory of natural selection states that variations already present within a population are selected for by the environment, meaning only the advantageous traits are passed on to the next generation, not traits acquired during an individual's life EX.) THAT SLIGHTLY LONGER TRUNKS OBTAINED MORE FOOD
Types of Evidence: Beak Depth on Daphne Major
- medium ground finches on Daphne Major
- a model of natural selection
- beak depth is a heritable trait
- provides evidence of natural selection in action
- fewer seeds on the island from a drought - had to eat larger seeds so beaks over generations lengthened
Types of Evidence: Selective Breeding
- kind of manipulating natural selection (the traits that humans like and breed may have been eliminated via natural selection in the environment)
- differs from natural selection in how the parents are chosen - desirable phenotypes chosen by breeders
Type of Evidence: Biogeography
- study of the geographic distribution of extinct and living species
- isolated continents have evolved their own distinct plant and animal communities
Endemic - naturally found only in a particular location
**Different pressures in different environments**
Types of Evidence: Convergent Evolution
- two species from different lineages have independently evolved similar characteristics because they occupy similar environments
- they are not related
- different species, different evolutionary traits
SAME SOLUTIONS TO SAME PROBLEMS, BUT DIFF ANIMALS
ex.) hummingbirds and butterflies
- hovering, long and thin beak or probescis
ex.) English Ivy and wintercreep
- to climb up supports
Types of Evidence: Fossil Record (transitionary forms)
• Fossils are compared according to their age, from oldest to youngest
• Successive evolutionary change becomes apparent
• Transitional form: Fossils that provide a link between an ancestral form and its descendants
What is a Fishapod (Tiktaalik Roseae)
- a semi-aquatic amphibian
• Transitional form between fishes and tetrapods(walk on all 4 limbs)
• Had broad skull, flexible neck, eyes on top of head, primitive wrist, and five finger-like bones - but also fin-like structure
• Could peek above water and look for prey
Types of Evidence: Homology
- fundemental similarity due to descent from a common ancestor
- homology may be:
1. Anatomical
2. Developmental
3. Molecular - similar sequences
Examples of Vestigial structures: remnants or 'left-over' structures - no real pressure to get rid of it
- humans: bony tail in embryo and mucles to wiggle ears in adult
- manatees: fingernails on the flippers
What are HOMOLOGOUS GENES:
- two or more genes derived from the same ancestral gene
What are ORTHOLOGS
- homologous genes in different species
What are PARALOGS
- two or more homologous genes within a single species
produced by gene duplication events
What are GENE FAMILIES
- two or more paralogs within the genome of a single organism
What are globin genes
Allows for specialized function, expression at different times or in different tissues
Horizontal Gene Transfer or Vertical Gene Transfer
Vertical evolution: new species arise from pre-existing species by accumulation of genetic changes
Horizontal gene transfer: an organism incorporates genetic material from another organism, without being its offspring
• Same or different species
What is a GENE
- a DNA sequence that codes for an RNA or protein
- contributes to the characteristics and traits of an organism
- a gene is found at a chromosomal locus
- different variants of a gene are called alleles
________ organisms typically have _____ copies of every gene
DIPLOID organisms typically have TWO copies of every gene
Genotype vs. Phenotype:
Genotype: the combination of alleles that a person possesses at a single locus or number of loci
Phenotype: observable characteristics of a person, organ, or cell
POLYMORPHISM
- many traits or genes display variation within a population
- genes are usually polymorphic
Most variation (polymorphism) is due to _________________________ (SNPs)
Most variation (polymorphism) is due to SINGLE NUCLEOTIDE POLYMORPHISM (SNPs)
Explain the HARDY-WEINBURG EQUATION: highly impractical but useful
• Describes a mathematical relationship between allele frequencies and genotype frequencies in a population
• The Hardy-Weinberg equation states that:
• p2 and q2 are the genotype frequencies of the homozygotes
• 2pq is the genotype frequency of heterozygotes
○ Multiplied by 2 because two different gamete combinations produce heterozygotes
predicts that allele and genotype frequencies will remain the same generation after generation, if the population is in equilibrium (= 0.5)
• No evolutionary mechanisms acting on the population
• Conditions that must be met for equilibrium:
1. No new mutations
2. No natural selection
3. Large population
4. No migration between different populations
5. Random mating
what is endemic
- naturally found only in a particular location
convergent traits can also be called _____________ structures
ANALOGOUS structures
What is an example of convergent traits
- hummingbirds and hummingbird moth
Hummingbirds:
- ability to beat their wings rapidly and their long thib beak
Moth:
- have a proposcis
T/F, homology may be:
- anatomical
- developmental
- molecular (similar sequences)
TRUE
what is a gene:
A DNA sequence that codes for an RNA or protein
- found at a chromosomal locus
- contributes to the characteristics and traits of an organism
different variants of a gene are called alleles
T/F, diploid organisms have two copies of every gene
TRUE
if alleles are identical = ______________
if alleles are different = ______________
if alleles are identical = homozygous
if alleles are different = heterozygous
what are POPULATIONS
- Group of individuals of the same species that occupy the same environment and can interbreed with one another
- Some species occupy a wide geographic range and are divided into discrete populations
- Populations can change in size, geographic location, and genetic composition
T/F, large, healthy populations exhibit a high level of genetic diversity
TRUE
Disequilibrium
- populations rarely achieve equilibrium
why is Hardy-Weinburg equilibrium a useful concept?
• When researchers examine allele and genotype frequencies, and find that a population is not in equilibrium, this indicates a condition is being violated
○ It acts as a baseline to identify if a population's allele frequencies are changing over time, indicating potential evolutionary forces at play
What is microevolution
- changes in a population's gene pool from generation to generation
- due to:
- introduction of new genetic variation: occur at a low rate, do not significantly disrupt HW equilibrium
- mechanisms that alter the prevalence of an allele or genotype: potential for widespread genetic change
what is natural selection
process by which beneficial traits that are heritable become more common in successive generations
- over time, natural selection results in adaptations: changes in populations of living organisms that promote their survival and reproduction in a particular environment
T/F, reproductive success is a KEY piece of natural selection
TRUE
what is REPRODUCTIVE SUCCESS
- the likelihood of an individual contributing fertile offspring to the next generation
what are the two categories of traits of reproductive success
1. Traits that make organisms better adapted to their environment and more likely to survive to reproductive age
2. Traits directly associated with reproduction, such as those that affect the ability to find a mate or produce viable gametes and offspring
modern description of natural selection
- allelic variation arises from random mutation
- some alleles encode proteins that enhance survival or reproductive success
- individuals with beneficial alleles are more likely to survive and pass these alleles to the next generation
- over time, allele frequencies change through natural selection, altering the characteristics of a population
FITNESS meaning
- relative likelihood that a genotype will contribute to the gene pool of the next generation as compared to other genotypes
- measure of reproductive success
What are the four NATURAL SELECTION PATTERNS (DSDB)
1. Directional selection
2. Stabilizing selection
3. Disruptive/Diversifying selection
4. Balancing selection
Pattern of natural selection: Directional Selection
• Individuals at ONE EXTREME of a phenotypic range have greater reproductive success in a particular environment
• Initiators:
• Prolonged environmental change
• New allele with higher fitness introduced by mutation
• Causes the favoured allele to eventually predominate in a population
• May lead to a monomorphic gene (no variation)
Pattern of Natural Selection: Stabilizing Selection
• Favours the survival of individuals with intermediate phenotypes and selects against those with extreme phenotypes
• Example: Clutch size
• Too many eggs à offspring die due to lack of care and food, strain may decrease parent survival
• Too few eggs à does not contribute enough to next generation
Pattern of natural selection: Diversifying selection
• Favours the survival of two or more different genotypes that produce different phenotypes
• Likely to occur in populations that occupy heterogeneous environments
• Fitness value of one genotype is high in one environment, but lower in a different environment, and vice versa
• Members of the populations can freely interbreed
Pattern of natural selection: Balancing selection
• A type of natural selection that maintains genetic diversity in a population
• Over many generations results in balanced polymorphism: Two or more alleles are maintained in a population over
the course of many generations
• Two common ways this occurs:
1. Heterozygote advantage: Heterozygotes for a trait have the highest fitness
○ E.g. Sickle cell disease
2. Negative frequency-dependent selection: The fitness of a genotype decreases when its frequency becomes higher
○ Rare individuals have a higher fitness than common individuals
○ E.g. Predator & prey
Sexual Selection
- type of natural selection
- individuals with certain traits are more likely to engage in successful reproduction than other individuals
- often affects males more than female
SEXUAL DIMORPHISM
- significant difference between the appearances of the two sexes within a species
Intrasexual selection
- between members of the same sex
- males directly compete for mating opportunities or territories
ex.) horns in male sheep, antlers in male moose, male fiddler crab enlarged claws
Intersexual selection
- between members of the opposite sex
- aka mate choice
- often results in showy characteristics in males
Cryptic female choice:
- a type of intersexual selection that occurs by female-driven mechanisms at or after mating
• Leads to differential success of sperm in fertilizing the egg
• May sometimes function to inhibit inbreeding
ex.) Female guppies will control copulation to receive less sperm from less colourful males
The Cost of Reproduction:
• Sexual selection can explain traits that decrease survival but increase reproductive success
• If trait increases predation, its frequency may be lower in environments where predators are abundant
what is GENETIC DRIFT
• Changes in allele frequencies due to random chance
• Unrelated to fitness
• Favours either loss or fixation of an allele
• Frequency reaches 0% or 100%
• Effect is strongest in small populations, where infrequently occurring alleles face a greater chance of being lost
• Reduces genetic diversity
• May quickly alter allele frequencies after population reduction, e.g.:
• Population bottleneck
• Formation of a founder population
what is BOTTLE EFFECT
a mechanism that drives genetic drift
- Population size is reduced dramatically, and then rebuilds
- Randomly eliminates members without regard to genotype
- When the population is small, genetic drift may rapidly reduce the genetic diversity
- Surviving members may have allele frequencies different from original population
explain the founder effect
- also causes genetic drift
• Small group of individuals separates from a larger population and establishes a colony in a new location
• Relatively small founding populations are expected
to have less genetic variation than original population
• By chance, allele frequencies in founding population may differ markedly from original population
• Fewer individuals to select from, allele frequencies differ from the original one given time
• Amish of Lancaster descended from 3 couples
• Ellis-van Creveld syndrome rare in human population
• Traced back to 1 of the 3 original couples
what is gene flow
- transfer of alleles into or out of a population
occurs when: fertile individuals move between populations having different allele frequencies
what does migration tend to REDUCE and what does it tend to INCREASE
• Reduce differences in allele frequencies between the two populations
• Increase genetic diversity within a population
what is nonrandom mating and what are the two forms that it occurs in
• Individuals choose their mates based on their genotypes or phenotypes
• Affects the balance of genotypes predicted by Hardy-Weinberg
• Occurs in two forms:
1. Assortative / disassortative mating
2. Inbreeding
Assortative and Disassortative Mating:
• Assortative mating
• Disassortative mating
Assortative mating: Individuals with similar phenotypes are more likely to mate
• Increases the proportion of homozygotes
- a female is choosing a mate that looks more similar to her - diff than sexual selection
• Disassortative mating: Dissimilar phenotypes mate preferentially
• Increases heterozygosity
Inbreeding:
- does inbreeding plumet or raise genetic diversity
• Mating of two genetically related individuals
• Increases homozygosity and decreases heterozygosity
• May have negative consequences with regard to rare recessive alleles
- it plumets genetic diveristy
T/F, inbreeding occurs if: homozygous offspring have a lower fitness value, inbreeding lowers the mean fitness of a population
TRUE
what animal is an example of inbreeding
florida panther
The Earth is believed to have formed from the aggregation of planetesimals(rocks) ~____ BYA
4.55 BYA (billion years ago)
life emerged between ____ and ____ BYA
4 and 3.5 billion years ago
DNA is made by ________________ process
DNA is made into RNA by _________________ process
RNA is made into proteins by _________________
DNA is made by REPLICATION process
DNA is made into RNA by TRANSCRIPTION process
RNA is made into proteins by TRANSLATION process
• Organic molecules and macromolecules formed spontaneously and slowly accumulated in early oceans
= Prebiotic soup
where did this "prebiotic soup" originate
1. Reducing atmosphere hypothesis
2. Extraterrestrial hypothesis
3. Deep-sea vent hypothesis
what is a PROTOBIONT:
An aggregate of prebiotically produced molecules and macromolecules that have acquired a boundary, such as a lipid bilayer
• Allows it to maintain an internal chemical environment distinct from that of its surroundings
what are the four characteristics of a protobiont:
1. A boundary separating external environment from internal contents
2. Polymers inside containing information
3. Polymers inside with enzymatic function
4. Capable of self-replication
T/F: living cells may have evolved from LIPIDS and COACERVATES
true
what are the three RNA functions
1. Ability to store information
2. Capacity for self-replication
3. Enzymatic function (ribozymes)
(DNA and proteins cannot do all 3 functions)
What nucleic acids do DNA and RNA have
DNA: Adenine, Thymine, Cytosine, Guanine
RNA: Adenine, Uracil, Cytosine, Guanine
Advantages of DNA/RNA/Protein world
• Information storage
• Incorporation of DNA to store information would relieve RNA of this function, and allow RNA to perform more complex catalytic functions
• DNA has increased stability - two strands!
• Ancestral RNA may have been able to make DNA from RNA template
• Metabolism and other cellular functions
• Proteins have vastly greater catalytic potential
• Proteins can perform other tasks – structural, transport, etc.
• Ancestral RNA likely contributed to polypeptide formation
○ Still plays central role in protein synthesis!
WHAT DOES LUCA STAND FOR
= last universal common ancestor
fossils are formed in ________________ rock
SEDIMENTARY rock
what are the FOUR layers of sedimentary rock:
1. Sedimentation: Eroded sediments end up in the water and begin to settle
2. Compaction: with time, more layers pile up and presses down the lower layers
3. more layers (strata) and further compaction forces out water of the layers
4. Salt crystals glue the layers together (cementation). Rock mass formed its sedimentary.
radioisotope dating looks at what??
Fossil age is estimated by radiometric dating
(measures the amount of a radioisotope and its decay product)
Each radioisotope has a unique _______________ that can be used for dating
Each radioisotope has a unique HALF-LIFE that can be used for dating
what is HALF-LIFE
time required for exactly one-half of original isotope to decay
name the factors that affect the fossil record: A.G.E.N.T.S (plus P)
A - anatomy
G - geological processes
E - environment
N - number
T - time
S - size
P - paleontology
what are the four eons of Earth's timeline
- Hadean
-Archaean
- Proterozoic
- Phanerozoic
= make up the Precambrian era
what are 6 ENVIRONMENTAL CHANGES
1. Temperature
2. Atmosphere
3. Landmasses
4. Floods and glaciations
5. Volcanic eruptions
6. Meteoric impacts
what are the four periods of Earth
1. Pre-Paleozoic period
2. Paleozoic period (Pangaea)
3. Mesozoic period
4. Cenozoic period (modern Earth)
what are the two domains of prokaryotic life
- Archaea and bacteria
T/F: all life forms are PROKARYOTIC and ANAEROBIC
TRUE
Heterotrophs vs. Autotrophs
Heterotrophs: derive energy from chemical bonds within organic molecules that are consumed - likely came first
Autotrophs: directly harness energy from inorganic molecules or light
what are layered structures of calcium carbonate called
STROMATOLITES
define Endosymbiosis, Endosymbiont, and Host
• Endosymbiosis: within, beneficial relationship
• Endosymbiont: provided resources (energy or food)
• Host: provided protection from the environment
what are the three major cell lineages and which are more closely related to each other
- Bacteria, Archaea, Eukarya
- bacteria and archaea are more distinct from each other
- archaea is more related to eukarya than it is to bacteria
in the _______________ eon there are _____ eras:
- _________________
- _________________
- _________________
in the PHANEROZOIC eon there are THREE eras:
- Paleozoic - cabrian, etc. (least recent)
- Mesozoic -triassic, jurassic, creataceous periods
- Cenozoic - tertiary, quaternary, etc (most recent)
explain the Burgess Shale
- rock bed in Canadian Rockies that produced an abundance of fossils from the Cambrian period
causes of Cambrian Explosion
1. Evolution of shells allowed animals to exploit new environments - also to escape predation
2. Increase in atmospheric oxygen levels allowed for more complex body plans
○ Production of ozone layer helped screen UV radiation
3. Evolutionary arms race between predators and prey
towards the end of the ____________ period, there was drastic climate change - which triggered mass extinction and a big loss of diversity
towards the end of the ORDOVICIAN period
list the order of the periods (from oldest to most recent) in the Paleozoic era
1. Cambrian Period
2. Ordovician Period
3. Silurian Period
4. Devonian Period
5. Carboniferous Period
6. Permian Period
list the periods in the Mesozoic era
- cretaceous period
- jurassic period
- triassic period
list the periods in the cenozoic era (2)
- tertiary period
- quaternary period
what period did insects and tetrapods come into existence
Devonian Period
explain tetrapod evolution
- four limbs
- increased adaptations for survival on land
- dragged itself forwards using strong front limbs
what period saw the emergence of reptiles
- carboniferous period
at the end of which period was the largest known mass extinction event (that eliminated 90-95% of marine species and large proportion of terrestrial species)
Permian period
- was due to glaciations or volcanic eruptions
which era is the "Age of Dinosaurs"
- Mesazoic era
Mesozoic era = "middle animals"
did the triassic period have the emergence of first dinosaurs and mammals
YES
what is the Cretaceous Period known for?
- for essentially wiping out the dinosaurs
- from another mass extinction at the end of the period
the Cenozoic era is sometimes called the Age of ____________
the Age of Mammals
did the Cenozoic Era have amazing diversification of birds, fish, insects, and flowering plants
yes
the Quaternary period
- widespread extinction of many species of animals
- certain hominins become more like living humans
Macroevolution
- occurs at or above the species level
what are species defined as
Species: A group of organisms that maintains a distinctive set of attributes in nature - can't always think that all members of a species look identical because of sexual differences (ex. Male lion vs. female lion)
- Panthera leo
- Genus: Panthera
- Specific epithet: leo
- For species names (genus and specific epithet) are both either underlined or italicized
Panthera leo
- which is the genus and which is the specific epithet
Genus: Panthera
Specific epithet: leo
- both should be underlined or italicized
how many species are currently identified
- 2 million species
define subspecies:
- groups of the same species that have somewhat different traits but not different enough to be called a separate species
define Ecotypes
bacterial species – genetically distinct population adapted to local environment - happens a lot
what are the 5 characteristics commonly used to characterize species
1. morphological traits: measurable traits that distinguish them
- BUT, members of the same species can look very different and members of diff species can look similar
2. ability to interbreed (biological species concept)
3. molecular features
- DNA sequences within genes
- gene order along chromosomes
4. ecological factors
- factors related to an organism's habitat
5. evolutionary relationships
- based on phylogenies
- evolutionary trees
- fossil record and DNA sequences
explain the Biological Species Concept
- who created it
- A biological species is a group of interbreeding (or potentially interbreeding) individuals, that is reproductively isolated from other such groups
i.e., a group of individuals whose members have the potential to interbreed with one another in nature to produce VIABLE, FERTILE OFFSPRING but they CANNOT successfully interbreed with members of other species
- created by ERNST MAYR
name the 5 PREzygotic isolating mechanisms
1. Ecological (spatial) isolation from habitats
2. Temporal isolation from mating timing
3. Behavioral isolation from mating signals, sexual selection
4. Mechanical isolation from reproductive structures
5. Gametic isolation from gamete incompatibility
Postzygotic isolating mechanisms: Hybrid inviability, Hybrid sterility, Hybrid breakdown
Hybrid inviability: : Species hybrids not surviving (cross is made and they don't survive)
- the egg of one species is fertilized by the sperm from another species, but the fertilized egg fails to develop past the early embryonic stages
Hybrid sterility: Species hybrids not producing functional gametes - ex.) Zebroids and mules
- an interspecies hybrid survives, but it is sterile.
Hybrid breakdown: Reduced fitness of F2 - ex.) Tiglons and Ligers
- the F1 interspecies hybrid is viable and fertile, but succeeding generations (F2 and so-on) become increasingly inviable. This is usually due to the formation of less-fit genotypes by genetic recombination
what is SPECIATION and its underlying cause?
Speciation - formation of a new species
cause- the accumulation of genetic changes that ultimately promote enough differences so that we judge a population to constitute a unique species
- they become different enough that if brought back to their descendants they could not breed with them anymore
explain the two patterns of speciation: Cladogenesis and Allopatric speciation
Cladogenesis:
- division of a species into two or more species
- requires gene flow between populations to be interupted
Allopatric speciation:
- most prevalent method for cladogenesis
- occurs when some members of a species become geographically separated - so there is no gene flow, so they evolve independently and diverge into different species (they cannot interbreed anymore)
Explain SYMPATRIC SPECIATION (sym = same)(patric = homeland)
Occurs when members of a species that are within the SAME range diverge into two or more different species even though there are no physical barriers to interbreeding
Mechanisms include:
1. Polyploidy
2. Hybrid speciation
3. Adaptation to local environments
4. Sexual selection
the pace of speciation: Gradualism vs. Punctuated equilibrium
Gradualism
- each new species evolves continuously over long spans of time
• Large phenotypic differences that produce new species are due to the accumulation of many small genetic changes
Punctuated equilibrium
• Tempo more sporadic
• Species in equilibrium for long periods and then short rapid bursts of changes
Both views have merit
what is Evo-Devo: Evolutionary Developmental Biological
Compares the development of different organisms to understand:
• Ancestral relationships between organisms
• Developmental mechanisms that bring about evolutionary change
Involves the discovery of genes that control development, and how their roles vary in different species
Chicken vs. duck feet
Chicken feet: non-webbed pattern
- noninterconnected digits
- gremlin protein levels not expressed in interdigit regions in chicken
Duck feet: webbed pattern
- BMP4 levels are expressed
Define taxonomy
- the science that identifies, names, and classifies new species
- Carolus Linnaeus was the first modern practitioner of taxonomy - did not believe in evolution
who created a system of bionomial nomenclature
Linnaeus
*remember* Genus is capitalized, but the epithet is NOT capitalized
*remember* Genus is capitalized, but the epithet is NOT capitalized
State the Taxonomic Hierarchy: a nested series of formal categories
(D.K.P.C.O.F.G.S.S)
Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species, Subspecies
Taxonomy vs. Systematics:
Taxonomy:
- Science of describing, naming, and classifying living and extinct organisms and viruses
Systematics:
- Study of biological diversity and the evolutionary relationships among organisms, both extinct and modern
Taxonomic groups are based on hypotheses regarding evolutionary relationships derived from systematics
*REVIEW TABLE 25.1 FROM LECTURE ON CH 25*
*REVIEW TABLE 25.1 FROM LECTURE ON CH 25*
Phylogenetic Trees:
- depicts the evolutionary history of a group of organisms
- allow biologists to define evolutionary classifications
- can be modified as more info becomes available
- hypotheses that portray the branching pattern of evolution
- read a tree from bottom (extinct) to top (extant)
Anagenesis vs. Cladogenesis:
Anagenesis: some point in the fossil record where something looks like species A but there are changes, then call it species B - assume that species A has gone extinct - pattern keeps repeating
- No branching or diverging
Cladogenesis: something happens, an event, and it divides and there is divergence, ends up with two different species
explain what a CLADE and a NODE is in a phylogenetic tree
Nodes: branch points in a phylogenetic tree
Clade: consists of a common ancestral species and all of its descendant species - monophyletic lineage
Polyphyletic vs. Paraphyletic Taxa:
- Polyphyletic taxa - from diff lineages
○ Include species from separate lineages
○ Not intentionally used in systematics
- Paraphyletic taxa - excluding relatives on the right
○ Contain an ancestor and some but NOT ALL descendants
Homologies vs. Homoplasies
Homologies:
- Homologous characters resulting from common ancestry, so phenotypic similarities between organisms reflect underlying genetic similarities
- Can differ considerably among species
Homoplasies: (analogies)
- Analogous characters do not result from common ancestry
- Phenotypically similar and have similar functions
explain Convergent Evolution
- the evolution of similar adaptations in distantly related organisms that occupy similar environments
- homoplasy is often the product of convergent evolution
define homoplasy
- phenotypic similarity that evolved independently in different lineages
Traditional classification vs. Cladistic classification:
Traditional Classification:
- uses phenotypic similarities and differences
- saying that all the ones are more similar than they are with birds, the cladistic one showing how birds ARE similar to reptiles
Cladistic Classification:
- focus on recently evolved character states
- considered all one group, all considered reptiles
Character states: each character can exist in two forms
Ancestral characters - plesiomorphic (plesiotypic)
- old forms of traits
Derived characters - apomorphic (apotypic)
- new forms of traits, relative to other organisms
Synapomorphies vs. Symplesiomorphies
Synapomorphies: shared derived characters
Symplesiomorphies: shared ancestral traits
- useful to work out relationships
Plesiomorphies: do not help to work out relationships
Autopomorphies: unique derived traits - do not help to work out relationships
what is the Principle of Parsimony:
Preferred hypothesis is the one that is the simplest for all the characters and their states
For example: If two species possess a tail, assume that a tail arose once during evolution and both species descended from a common ancestor with a tail as opposed to each species independently evolving a tail.
ex.) according to the principle of parsimony, tree number 3 is the more likely choice because it requires only five mutations
**review Figure 25.13** from CH 25!!
**review Figure 25.13** from CH 25!!
Molecular clocks:
- - Because mutations that arise in noncoding regions of DNA do not affect protein structure, they are probably not often eliminated by natural selection
- If mutations accumulate in these segments at a reasonably constant rate, differences in their DNA sequences can serve as a molecular clock, indexing the time at which two species diverged
Molecular Clocks:
- Favourable mutations are rare, detrimental mutations are quickly eliminated – so most mutations are neutral
- If neutral mutations occur at a constant rate they can be used to measure evolutionary time
- Not perfectly linear over long periods of time
- Not all organisms evolve at the same rate
- Differences in generation times between different species
One of the most prominent features of the bacteria and archaea is their _____________.
is their DIVERSITY.
(both domain Archaea and domain Bacteria are prokaryotic and lack membrane-bounded nucleus
Common Shapes of Prokaryotic cells: Spherical, cylindrical or rod-shaped, spiral-shaped, comma-shaped
Spherical (cocci)
Cylindrical or rod-shaped (bacilli)
Spiral-shaped (spirilla)
Comma-shaped (vibrios)
Prokaryotic cell walls: Gram-positive vs. gram-negative bacterial cells walls
Gram-positive bacterial cell walls: a single, relatively thick peptidoglycan layer (open-faced bologna sandwich)
Gram-negative bacterial cell walls: a relatively thin peptidoglycan sheath surrounded by an outer lipopolysaccharide (LPS) membrane (bologna sandwich)
Gram-positive stains vs. Gram-negative stains
Gram-positive bacteria: killed by penicillin
- appear purple because crystal violet retained
Gram-negative bacteria: outer membrane protects from penicillin
- appear pink because crystal violet lost
- thick layer so it has a hard time accessing it
Explain flagella and pili - where are they located
Flagella: embedded in CELL WALL
- rigid helical proteins
- rotate like propellers
Pili: on the SURFACE
- rigid shafts of protein extending from cells walls
- help them adhere to other cells
Antibiotic resistance
Antibiotic: natural or synthetic substance that kills or inhibits growth of bacteria and other microorganisms
How do they develop resistance to antibiotics:
○ Pump antibiotics out of cell
○ Produce molecules that bind to antibiotics
○ Produce enzymes that break down antibiotics
○ Gene mutation
○ Horizontal gene transfer
RESISTANCE IS A FORM OF EVOLUTIONARY ADAPTATION - MICROEVOLUTIONARY CHANGES
what is biofilm:
- complex appregation of microorganisms attached to surface and surrounded by film of polymers
○ Harmful when attached to surgical equipment and supplies
○ Beneficial when used in sewage treatment plants or in cleanup of toxic organic molecules in groundwater - can eat the sewage and clean the water
Give facts on Cyanobacteria and Proteobacteria
Cyanobacteria: photosynthetic bacteria in water
- named for blue-green or cyan colour
- produce blooms and may release toxins harmful to the health of humans/animals
Proteobacteria: very large group of Gram-negative bacteria
- high metabolic diversity
- includes many species important in medicine, agriculture, industry and basic research
T/F, Cyanobacteria are the only prokaryotes that generate oxygen as a product of photosynthesis
TRUE
how many proteobacteria subgroups exist:
- Amazing diversity of form and metabolism
○ α – proteobacteria
§ Ancestors of mitochondria, Rhizobium, Agrobacterium
○ β – proteobacteria
§ Nitrosomonas
○ γ – proteobacteria
§ Neisseria, Vibrio, Salmonella, Escherichia coli
○ ε – proteobacteria
§ Helicobacter
Explain the extremophiles
- Can occupy habitats with extreme conditions
- High salt content – halophiles
- Acidity
- High methane levels
- High temperatures – hyperthermophiles
- Example: Methanopyrus
- Grows in deep-sea thermal vents at 98° Celsius
- Cannot grow at temps under 84° Celsius
Environments like: hot springs, hydrothermal vents, salt lakes
Archaea, specifically ___________, are found in low-oxygen environments like swamps, lakes, marshes, intestines, etc.
Methanogens
define Horizontal Gene Transfer:
- Movement of one or more genes from one species to another
- increases genetic diversity
the vast majority of Eukaryotes are ___________.
protists
name two characteristics of protists
- protists are most abundant in moist habitats
- most of them are microscopic in size
what are the three major "ecological" groups of protists
1. Algae: generally photoautotrophic
2. Protozoa: heterotrophic
3. Fungus-like: resemble fungi in body form and absorptive nutrition
Plankton vs. Phytoplankton vs. Periphyton
Plankton: swimming or floating protists
Phytoplankton: photosynthetic protists
Periphyton: communities of microorganisms
three types of ecological role of protists
1. Algae (plant-like)
2. Protozoans (animal-like)
3. Fungal-like
three classifications of movement of protists
1. Flagellates
2. Ciliates
3. Amoeboids
Characteristics of protists
Characteristics of protists:
Unlike bacteria and archaea, protists are eukaryotes and therefore, have:
- A membrane-bound nucleus, with multiple, linear chromosomes
- Microtubules and microfilaments, in addition to cytoplasmic organelles, including mitochondria and chloroplasts (in photosynthetic species)
- Transcription and translation characteristics similar to other eukaryotes
Describe protist habitat and structure
Habitat: Aqueous
- Aquatic or moist terrestrial locations
- Oceans, freshwater lakes, ponds, streams, and moist soil and within host organisms
Structure: unicellular or colonial with little differentiation
- some are large multicellular organisms (giant kelp)
are kelps protists?
largest, most complex protists
- multicellular marine forms
Is amoeba a protist?
YES
- heterotrophs (feed on bacteria, other protists, organic matter)
- have pseudopodia that extend and retract
- ASEXUAL, SINGLE-CELLED
Plantae: includes ______ _________ and two protist groups
- Includes land plants (kingdom Plantae) and two protist groups, all photoautotrophs
1. Rhodophyta (red algae): most small marine seaweeds
- plantlike bodies with stalks and leaflike blades
- typically multicellular
2. Chlorophyta (green algae)
- same pigment as true plants
- little differentiation
- high diversity of body forms and life cycles
What does a Choanoflagellate look like
- named for collar surrounding flagellum (looks kinda like a balloon)
- single-cell protist