What is a cladogram?
type of evolutionary tree built on “cladistic” principles
What are the three "cladistic" principles and define them
- synapomorphies-shared traits of other common ancestors
- Parsimony –method that implies as few evolutionary steps as possible
- Coherence –trees built using different synapomorphies should agree
What is a node on a cladogram?
a branching point
How are cladograms built (3 steps)?
- 1.) analyzing DNA
- 2.) looking at synapomorphies
- 3.) coherence-justification via multiple fields of study
What is a theory?
a proposed explanation for a very general class of phenomena
What is a hypothesis?
a proposed explanation for a specific phenomenon or set of observations
What are the three domains of life?
Of the archaea, bacteria, and eukaryotes, which are the two that are closer to each other?
eukaryotes are closer to archaea
What is the synapomorphy for all eukaryotes?
membrane bound organelles
What is a scientific theory?
a proposed explanation for general phenomena that is well suppported
What are the 2 components of a scientific theory and explain what they mean?
- pattern-what is occuring
- process-why is this occuring
What is meant by descent with modification?
- species change over time. different populations of the same species diverge
- different species are related, not independent creatures
How did we prove descent with modification? (4 ways)
- 1.) measuring the ages of the earth's strata (layers) via radiometric aging
- 2.) analyzing fossils
- 3.) Homologies
- 4.) Identifying homoplasy aka convergent evolution
What are fossils?
mineralized remains of organisms
a lineage with living representatives
a lineage whose members are all dead
What do transitional fossils tell us? What do they help build?
- They tell us which species are more closely related, show transition, evolution.
- Helps us build cladograms
Genetic and molecular homologies tell us...
species share the same gene
What are homologies?
similarities in characteristics due to shared ancestry
Define structural homologies
- physical similarities
- ex. bones
Define developmental homologies
Define genetic and molecular homologies
similarities in the DNA (genes)
similarities in characteristics due to environment not ancestry
We can insert our DNA into a plasmid and express the same protein because of what?
We can understand the development of humans via looking at flies. Why is this?
developmental homologies- different species have similar embryo stages or features, which we can compare
Define allele frequency
amount or percent of alleles proportional to other alleles in population
any measurable aspect of an organism
What is evolution?
change in allele frequency within a population over time
Define natural selection
- certain heritable traits lead to higher reproduction success relative to other individuals in the population
- that heritable trait is favored
Evolution=______ while natural selection=_______
group of individuals of one species that live in a particular place
What are the four major causes of evolution?
- genetic drift
- genetic bottleneck
- founder effect
any change in the hereditary material of an organism
Define genetic drift
a change in allele frequency due to sampling error
In a __________, genetic drift tends to eliminate alleles
Define sampling error
- a statistical error in which the sample does not
- represent the entire population
Define genetic bottleneck
- sudden loss of individuals or alleles within a population
- key giveaway: natural disaster
Is genetic bottleneck a form of genetic drift?
Define founder effect
- establishment or start of a new population
- new population does not equal old population
What are the four modes of natural selection and define them?
- directional- favors one extreme trait and pushes the graph to the left or the right
- disruptive- favors two extreme traits and creates a bump on the left and right
- stabilizing- favors intermediate traits and pushes the bump in the middle
- balancing- does not favor any traits, the graph remains the same, no change!
Which of the following modes of natural selection increases genetic variation?
What mode of natural selection would lead to increased speciation?
disruptive- this favors two phenotypes which could lead to them becoming separate species!
Which mode of natural selection: The allele frequency shifts in one direction over time
Which mode of natural selection: increases genetic variation when natural selection favors two extreme phenotypes
Which mode of natural selection: it results in a decrease of genetic variation when natural selection selects against the phenotype
Which mode of natural selection: the allele frequency stays the same
Darwin's thought process for natural selection as the mechanism for evolution (4 bullet points)
- 1.) all organisms have great capacity to reproduce
- 2.) despite this, most populations maintain a stable size for long periods of time
- 3.) because within a population, individuals in their traits, which influences the ability to reproduce
- 4.) Those individuals with traits best suited to the environment will tend to produce more surviving offspring.
Why is it so important for the offspring to be viable?
so the traits can be passed down to other generations, so the lineage will not die
Misconceptions of evolution (list 3)
- evolution creates perfection- wrong, there are constraints with adaptation
- evolution is over- wrong, evolution is still occuring
- individuals limit their reproduction for the "good of the species"- wrong, adaptations come about via natural selection
Hardy Weinberg principle/Equilibrium
model that states that allele and genotype frequencies in a population will remain constant from generation to generation in the absence of other evolutionary influences.
We are in Hardy Weinberg Equilibrium when there is... (5)
- no gene flow
- no genetic drift
- no natural selection
- no mutation
- random matings
What are the three species concept?
- biological species concept
- morphospecies species concept
- phylogenetic species concept
Biological species concept
- defines a species as a group of populations that are reproductively compatible with each other
- prezygotic barriers or postzygotic barriers
anything that prevents individuals from two populations/species forming a zygote together.
Prezygotic barriers and their definitions (5)
- temporal isolation- Populations adapted to different habitats or are active at different times of day or year.
- habitat isolation- live in different places
- behavioral isolation- Signals used toattract mates differ between populations.
- mechanical isolation- can't physically mate
- gametic isolation- gametes are not compatible
- Reduced hybrid viability (survivorship) or fertility (reproductive capacity).
- ex. mule
Why don't we always use the biological species concept? Issues?
- some organisms reproduce asexually
- it only applies to extant species (not extinct)
classifies species based on their appearance
Issues with the morphospecies concept:
- two different species can look identical or very similar but they are different species
- two same species can look completely different but they are the same species
Phylogenetic Species Concept
a group of organisms with a shared, unique genetic history
Issues with Phylogenetic Species Concept
- only available for a minority of species
- polyploidy also violates this concept
A tree falls over, separates two ants. The ants evolve into two different species. What type of speciation is this?
Allopatric speciation by Vacariance (physical barrier)
What are the two modes of speciation?
- allopatric speciation (living apart)
- sympatric speciation (living together)
- species divergence through long-term spatial isolation, especially by a physical barrier (vicariance)
- or by dispersal- some part of the population goes off and moves to a new geographic location and adapts
- speciation that occurs when two diverging populations live in the same area
- 1.) by disruptive selection- adapt to different niches in the same geographic area
- 2.) by polyploidization
What is the difference between cladogenesis and anogenesis?
- Anogenesis is over progression
- Cladogenesis is branching off to form new species
- happens when one ancestral lineage diversifies rapidly, creating many species with diverse traits
- rapid evolutionary diversification within a lineage
Autopolyploidy – speciation involving failed meiosis and gamete fusion between 2 individuals of the same species
Allopolyploidy – interspecific fertilization followed by chromosome doubling
the study of how organisms interact with the environment
2 components to “environment”:
- Biotic – other organisms
- Abiotic – physical environment
Terrestrial Biomes (“communities”):
characterized by dominant vegetation type; controlled by climate (annual mean temperature & precipitation)
What determines temperatures?
Why do we have seasons?
earth's tilt at 23.5 degrees
Hadley cells: major cycles in global air circulation
Define rain shadow
thirsty side of the mountain that lacks warm and moist air
srudy of how and why the number of individuals in a population change over time
grows until it reaches carrying capacity
focuses on the interactions that affect the distribution or abundance of a species
Types of species interaction and define them (5)
- 1.) mutualism (+/+)- an interaction that benefits both species
- 2.) competition (-/-)- an interaction that occurs when two species use a limiting resource
- 3.) herbivory (+/-)- consumption of plant tissue
- 4.) parasitism (+/-)- consumption of tissue/nutrients from host
- 5.) predation (+/-)- one animal kills and consumes an individaul
Competition is a result of....
the evolutionary change in resource use
affects a trait to allow it to exploit different resources
What happens if there is too much overlap between the niches of 2 different species? (state the term and define it)
Competitive exclusion- the stronger species will drive the other species to extinction
- Pattern of evolution over large time scales
- Larger than the species level
- Same 4 mechanisms of gene flow, natural selection etc
Earth's estimate age
4.54 billion years
Precambrian Era and it's 3 key events
- first 4 billion years in Earth
- oxygen revolution
- Cambrian explosion- first appearance of oldest animal fossils
- first eukaryotes- membrane bound organelles, nucleus
Paleozoic Era key events
- plants colonize land
- continental drift- movement of continents over time
How might the building of mountain ranges affect organisms with respect to evolution and its mechanisms?
rain shadows effects and reduce gene flow between populations
- a large scale, widespread extinction event that occurs within 1 million years
- rapid extinction
normal rate of extinction
Early Paleozoic Era
- Cambrian explosion- huge amount of animal diversity
- first mass extinction due to the cooling at the end of Ordovican
Mid-Late Paleozoic Era
- great diversification of land plants; insects and tetrapods evolved and diversified (including ancestors of mammals …)
- Cooling at end Devonian – Second great mass extinction
Late Paleozoic Era
- formation of Pangea
- warm and humid on land- great forests (coal)
- End Permian (P/T) extinction- due to volcano, 95% marine species, 70% terrestrial families
The Mesozoic Era
- Mostly hot, humid
- Radiation of reptiles, origin and radiation of dinosaurs
- Radiation of gymnosperms
- origin of flowering plants (angiosperms), birds, mammals
Two Mesozoic Mass Extinctions
- 1) End Triassic (200 mya)
- 2) K/T or K/P (65 mya- end of dinos) Iridium anomaly at boundary
The Cenozoic Era (65 mya to present)
- Cooler and drier
- Slow recovery at first
- Radiation of birds, mammals, angiosperms, insects
- Origin of apes (30 mya)
True or False: “Prokaryotes are a paraphyletic group”
evolutionary group that includes an ancestral population and some but not all of its descendants
evolutionary group that includes an ancestral population and all of its descendants
Prokaryotes are (3)
- Ubiquitous- found everywhere
- organic molecules
- ex. glucose
- inorganic molecules
- ex. NH3, H2S
- use inorganic sources
- ex. CH4 , CO2
absorb carbon compounds produced by other organisms
Lateral gene transfer
bacteria can acquire genes from each other and from the environment
use of living organisms to degrade pollutants