Module 1 Exam Review Flashcards
Catastrophism
events in the past occurred suddenly and was caused by mechanisms that no longer operate
Uniformitarianism
mechanisms of change are constant over time
Lamark’s Hypothesis of evolution (2)
- Use and disuse- parts of the body used more become stronger
- Inheritance of acquired characteristics- organisms can pass modifications to offspring
Adaptations
inherited characteristics that enhance the survival and reproduction in specific environments
Natural Selection
a process in which individuals that have certain traits tend to survive and reproduce at greater rates because of these traits
- Survival of the fittest
- Not evolution but can lead to evolution
- Generally adapts a population to its environment
Artificial selection
modifying species by selectively breeding individuals that posses a desired trait
Homologous structures
structures in different species that are similar because of common ancestry
Ex. forelimbs of whales and cats
Vestigial Structures
remnants of features that served a function in the organisms ancestry
Convergent evolution
independent evolution of similar features in different lineages
EX. CAM photosynthesis evolved independently at least 2x, gliders
Analogous features
features that share similar function but not common ancestry
- result of convergent evolution
Genetic Variation
differences among individuals in the composition of their genes or other DNA segments
- introduced into pop. via sexual reproduction & mutation
Mechanisms that contribute to variation (3)
crossing over, independent assortment of chromosomes, fertilization
Gene pool
consists of all copies of every type of allele at all loci in every individual in a population
Hardy-Weinberg Principle
states that frequencies of alleles and genotypes in a population will remain constant from generation to generation provided only mendelian segregation of alleles
(unless acted upon by agents other than sexual recombination)
Conditions of Hardy-Weinberg equilibrium(5)
- no mutations
- random mating
- natural selection
- extremely large population size
- no gene flow
Genetic drift
chance events cause unpredictable allele frequencies from one generation to the next
“population emerging from sampling error doesn’t reflect original population”
founder effect
few individuals become isolated from larger population and form a new gene pool that doesn’t reflect the larger one
NEW PLACE
bottleneck effect
size of population is reduced by natural disaster or human action, surviving population is not genetically representative of original population
SAME PLACE
- non-selective reduction
gene flow
Transfer of alleles from one individual to another
Gene flow= Gene movement + gene establishment
Greater influence in smaller populations
relative fitness
the contribution an individual makes to the gene pool of the next generation relative to the contributions of other individuals
Directional, Disruptive, and stabilizing selection
Directional selection: individuals at one end of the phenotypic range survive/reproduce more successfully than other individuals
Disruptive selection:individuals on both extremes of phenotypic range survive/reproduce more successfully than other individuals
Stabilizing selection:intermediate phenotypes survive/reproduce more successfully than do extreme phenotypes
Sexual Selection
individuals with certain inherited characteristics are more likely to obtain mates
- can result in sexual dimorphism
Biological species concept
defines a species as a group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring
- reproductive isolation
Pro: based on evolutionary independence
Con: not applied to asexual species & fossils
Reproductive isolation
existence of biological barriers that impede members of 2 species from interbredding and producing viable offspring
Prezygotic barriers
Blocks fertilization from occurring before the zygote is formed
- habitat isolation
- behavioral isolation
- temporal isolation
- mechanical isolation
- gametic isolation
Lead to rapid speciation
Post zygotic barriers
barrier that prevents hybrid zygotes from developing into viable, fertile adults
- reduced hybrid viability
- reduced hybrid fertility
- hybrid breakdown (infertile offspring)
other definitions of species
- morphological
- ecological
- phylogenic
- morphological: by structural features
- ecological: by ecological niche
- phylogenic: by groups on individuals that share a common ancestor
Allopatric Speciation
gene flow is interrupted when a population is divided into geographically isolated sub-populations
- occurs by geological remodelling or colonization (“different land”)
Sympatric speciation
evolution of a new species from a surviving ancestral species while both continue to inhabit the same geographic region (“Same land”)
- can result from allopolyploid
Polyploidy, Autopolyploid, Allopolyploid
Polyploidy: when a species has an extra set of chromosomes(plants)
Autopolyploid: individual that has more than 2 chromosome sets that are all derived from a single species
Allopolyploid: when a sterile hybrid is changed into a fertile polyploid
Spontaneous increase in chromosome #
- Cannot interbreed with parent species so they are considered a new biological species
Radiometric dating
a method for determining the absolute the absolute age of rocks and fossils, based on the half-life of radioactive isotopes
Adaptive radiations
period of evolutionary change in which groups of organisms form many new species whose adaptations allow them to fill different ecological roles in their communities
phylogenic trees
depicting evolutionary relationships as a branching tree
there are no primitive species!!!*
- homologous traits to reflect evolutionary relationships
clade
monophyletic grouping that includes an ancestral species and all of its descendants
- distinguished by shared derived characters
molecular clock
amount of genetic change is used to estimate the date of past evolutionary events
parsimony
choosing the simplest hypothesis, requires the fewest base changes
Evolution
accumulation over time of inherited changes in populations leading to species which are related
Darwinian fitness
Individual’s ability to survive reproduction
population
Group of organisms of a single species in the same geographical area
- smallest unit that can evolve (individuals adapt!)
Species
Group of organisms with common ancestry and physical structures that’re able to breed and have fertile offspring
Essentialism
Organisms are created in specific forms
Linnaeus
ancestral forms can reflect evolutionary relationships (descent with modification)
Assumptions made on evolution
Evolution takes time!
- natural selection acts on phenotypes with a generation, so variation must be partly heritable for natural selection to result in evolutionary change between generations
- small evolutionary changes can occur rapidly, complex adaptations need multiple changes over many generations
4 observations of natural selection
- variation in phenotype exists among individuals
- high reproductive potential= population increase geometrically
- individuals compete for limited resources
- “fit” offspring with characteristics matching current env. more likely to survive/reproduce
Comparative anatomy
existence of homologous structures beneath phenotypically different characters- indicate shared origin
Comparative embryology
Organisms that share common ancestor but were subjected to different selection pressure in adulthood were shaped differently in adult structures… but share common embryological stages
EVO-DEVO
Molecular biology
Evolutionary origins are reflected in DNA
Case study- Soapberry bugs
Bugs feeding apparatus changed when they transitioned from balloon vine fruit to flat-podded golden rain fruit, change persisted in lab
- change was adaptation (heritable) & not phenotypic plasticity
Developmental biology
Species differ as adults but have similarities as embryos
- EVO DEVO
How old is life on earth?
When did unicellular life evolve?
- 6 billion years old
3. 8 billion years old
Evolution of LUCA (key points)
Inorganic mol. > organic mol. > self-replicating mol. > aggregations > progenote
- early earth was highly volatile
Evolution of eukaryotes
Endosymbiotic hypothesis:
- Mitochondria arose from intracellular parasitic bacteria (env. conditions selected for endosymbiont)
- primitive mitochondria had very efficient metabolism
- mitochondria escaped toxic O2 atmo. & eukaryote got a “chef”)
Evidence: endosymbiotic hypothesis
- Mitochondria/chloroplasts have own DNA, “like bacteria”
- DNA sequencing shows they were primitive bacteria moving inside primitive eukaryote
BUT they produce toxic ROS Selective pressure> evolution - Mitochondria moved to nucleus - protective nuclear envelope - ways to manage waste
Great oxygenation event
photosynthesis by cyanobacteria increased O2 concentration in atmosphere
Ediacaran fauna
- Earliest complex multicellular organisms
- Large morphological diversity
Cambrian explosion
- Earth suddenly erupted into many new groups of organisms
- Organisms with modern body plans (segmentation)
Extinction
- when can mass extinctions occur
- 99.9% of species are now extinct
mass extinctions:
Extinction rate»_space; speciation rate
Periodic (cyclical)
>90% of species go extinct
Causes of mass extinction
- Gradual env. changes (press)
- ocean anoxia, climate change - Catastrophic event (pulse)
- asteroid, volcano
Extinction recovery
Extinctions create vacant niches
More complex the ecosystem, the more difficult/long the recovery
How do we get rapid evolutionary change (evolutionary novelty)
Heterochrony= changes to timing of development
Hox genes= set of patterning genes
Hox gene example: Ultrabithorax
Hox genes allowed formation of novel traits (new traits)
Paedomorphism
When adult at sexually mature stage, maintains juvenile traits
Ex. salamander vs axolotl (external gills)
Human paedomorphosis
Human as giant foetal ape (cranial morphology, etc.)
How are traits selected for/against
- selection of the fittest
- evolution is not goal directed
- Natural selection acts on phenotypes within a generation
- small changes can occur rapidly but usually it is a slow process
Other mechanisms of evolution
- Sexual selection
- Drift
- Random mutations
- Gene flow
How is variation introduced
Measure variation:
heterogeneity & allelic richness
Mutations
Heritable changes
- In haploids, most mutations are harmful (bacteria)
- In diploids, new mutations are hidden by other allele
Case study: E. coli
Mutations can be good & lead to evolution/adaptation!
Rapid reproduction + high mutation = strength in numbers
- E. coli were unable to aerobically citrate but with 1 mutation they were able to
Sexual reproduction
Variation in genetic structure of organisms between generations, due to 3 factors:
- random mating
- random segregation of parental chromosomes in meiosis
- meiotic recombination between homologue chromatids/crossing over
Sex is good when…
environment is unpredictable
Genes aren’t good
Sex is bad when…
Genes are good already
Clone is better!
Sex in large populations
all sources of random variation cancel each other out
As long as:
mating is random & population is big
Balanced polymorphism
Active maintenance of variation
- diploidy, patchy environments, frequency-dependent selection
Diploidy
Hides variation as recessive
Patchy environment
Environment presents variation in a variable, variation in the population will be adaptive since organisms may occupy environment fully
dark and light moths > only dark in forest of dark/light trees
Frequency-dependent selection
Specific phenotype becomes very frequent, environment can adapt to it (predator develops new hunting strategies)
Organism presents a phenotype deviating from it will become better adapted to the environment
Case study: Sickle cell anemia
Trade off= heterozygote advantage
AA= can get malaria Aa= Resistant to malaria but may have disease aa= fatal disease, resistant to malaria
Case study: Beta-thalassemia
Heterozygote advantage
- Blood disorder that can protect from malaria
Phenotypic plasticity
Pheno= genotype + environment
Ex. human height increasing
- diet, genes, environment
Micro-evolution (short-time) forces
Changes in a short time frame
Non-random mating
- weed out weak alleles
Assortative mating
Inbreeding depression
- if you mate with relatives, increased chance of recessive disease
Hardy-Weinberg equilibrium Equation
Allelic frequency: p + q = 1
Genotypic frequency:
p^2 + 2pq + q^2 = 1
p= frequency of allele 1 q= frequency of allele 2
p^2= frequency of homozygous dominant genotype 2pq= frequency of heterozygous recessive genotype q^2= frequency of homozygous recessive genotype
Case study: Greater Prairie Chickens
Bottleneck effect
human influence: habitat destruction
- if you allow gene flow you can restore balance
Case study: Afrikaner’s
Founder effect
Huntington’s disease is abnormally high
Chris study example: selection
In mountains=
shorter reproduction time
Higher flowers, flower earlier
Morphological (speciation)
anatomical differences
Pro: widely applicable
Con: subjective
(vulnerable to convergent evolution)
Phylogenetic
Smallest phylogenetic group
Pro: widely applicable, testable
Con: few phylogenies available
Reproductive Isolating Mechanisms (RIMs)
- prevent gene flow between species
- reproductive isolation between species can be pre/post-zygotic
- Organisms that don’t sexually reproduce can be classified based on morphological & biochemical characteristics
Behavioral isolation
Distinctive plumage, scents, calls
Required courtship behaviors
Temporal isolation
-normally refers to lack of mating between animals with diurnal vs nocturnal habits
Mechanical isolation
pollinator “coevolution”
Gametic isolattion
Gametes cannot fertilize
- incompatible sperm + egg
- Molecular recognition on cell surfaces
Sympatric speciation example
Apple maggot fly
hawthorn fruit= slow maturation
apples= introduced & mature faster > favored rapid larval development
Now 2 species, hawthorn and apple maggot
Allopatric speciation example
Snapping shrimp
- vicariance (habitat split)
- shrimp isolated by isthmus of panama
- population diverged bc no gene flow
Case study: sympatric speciation in lake Malawi
Fish are territorial: lots of sexual conflict + rapid evolution
- hybrids viable > mating behavior is RIM
- sensitive to human activities bc water is now murkier
Phylogenetics
Study of evolutionary relatedness among various groups of organisms
Macroevolution: Gradualism
Product of microevolution & adaptive divergence along very long periods of time
Gradualism is rare, mostly punctuated equilibrium
Monophyletic
Includes most relevant common ancestor
Paraphyletic
Contains most recent common ancestor & most of descendants
Polyphyletic
Lack common ancestor
