Evolution Flashcards
Linnaeus
founder of taxonomy
John-Baptiste Lamarck
evolution due to acquired traits FALSE
Cuvier
father of paleontology
did not follow evolution
strata: result of catastrophes
Hutton
theory of uniformitarism: earth is older than thought
Lyell
wrote Principles of Geology
Malthus
“An Essay on the Principle of Population”
Malthusian disaster: population overtakes food supply
Wallace
came up with idea of natural selection on his own
indirectly pushed Darwin to publish in 1859
4 Observations of Evolution
- variation in populations
- traits are inherited from parents
- all species capable of producing more offspring that environment able to support
- many offspring do not survive because of competition
2 Inferences of Evolution
- individuals with inherited traits that help them survive have more offspring
- unequal ability to reproduce makes one characteristic more prevalent
Evidence for evolution
- artificial breeding of plants and animals
- fossil records
- biogeography
- Endemic species
- Homology
- Analogy
- Vestigial structures
- Embryology
- Microevolution
Biogeography
geographic distribution of species.
pangea has come together and split apart 3 times
Endemic species
found in only one place one earth. usually islands
Homology
tetrapod arm structure
Analogy
result of convergent evolution: similar environments but no common ancestor
microevolution
initial drug resistance (vertical, traditional evolution)
second wave drug resistance: plasmid exchange (horizontal evolution)
Conditions for Hardy-Weinberg equilibrium
- large population
- Random mating
- No net mutations
- No selection/differences in ability to survive and reproduce
- No immigration/emigration
Effect of migration of evolution
- immigration: increases genetic variety
- emigration: reduces genetic variety
- homogenizing force
Random genetic drift
- change in allele frequency
- not an adaptive force, change due to chance
- could lead to fixation of an allele (greater chance in small population)
Directional natural selection
one extreme favored.
genetic variety reduced
Stabilizing selection
mean is favored.
Extreme phenotypes selected against
Disruptive selection
favors both extremes
genetic diversity increased, could lead to speciation
Balancing selection
broad term for any selection that acts to maintain diversity
Constraints of Natural Selection
- genetic variation needed
- phylogenetic inertia
- plietrophy
- Evolutionary trade-offs
- Random genetic drift interferes in small populations
Plietrophy
one gene that codes for many traits.
selection is unable to select against one of the traits because the others are necessary
Asymmetry of Sex
- eggs are expensive/hard to make—>makes women choosey
- sperm is cheap—->men limited by ability to find mate
Sexual dimorphism
males and females look different
Reasons for ornamentation
- Sexier son’s hypothesis/Fisher’s Runaway Process: females want sons to be sexy and mate so female chooses a sexy husband.
- “Good genes” trait: grey tree frogs with longer calls (that ladies like) have better fitness
Intrasexual combat
competition between males for females
intersexual choice
choosy females
It’s good to be a whore
- food gifts from possible mates
- Some mates are incompatible with each other
- Question of parentage gets more males involved in raising young
Point mutations
caused by replication error in meiosis or meitosis
Exon shuffling
expressed part of gene in new location leads to new protein
Transposable elements
transposons change positions within the genome
Horizontal gene transfer
transfer of genetic material from one individual to another
autopolyploid
individual with 2 or more sets of chromosomes from one species because of a failure to reduce number during meiosis
allopolyploid
individual with 2 or more sets of chromosomes from different species—>hybrid species
Rate of mutation dependent on….
- error rate
2. generation time
benefits of sex
- recombination creates new combinations of alleles
- increases genetic variation
- unfavorable mutations quickly purged from population
- Moving target for pathogens
costs of sex
- loss of fitness relative to clonal populations
- two-fold cost of sex: we cannot exponentially grow because we need males for ferilization
- only 1/2 of genes passed on
costs of being clonal
- evolutionary dead-end
- Muller’s Ratchet: mutations are not purged but perpetuated
- Kondrashov’s Hatchet: there is a level of mutations that is too high for an organism to survive
- Red Queen: clonal populations are a stationary target for pathogens
Allopatric speciation
Dispersal: colonization of islands/lakes
Vicariance: geological barriers cause isolatioin
Sympatric speciation
speciation without geographic barriers
results from polyploidism, niche partitioning, differences in habits between populations (like mating seasons)
Parapatric speciation
geologically separated but not isolated
Biological species concept
definition, strengths, weaknesses
Groups that can interbreed and produce viable/fertile offspring are a species
Strength: very clear
Weaknesses: not good for asexual populations, divergent species can hybridize, only applicable to present, ring species
Phylogenetic Species Concept
definition, strengths, weaknesses
constructs trees using DNA/other proteins
groups with a common ancestor are monophyletic
Strengths: easy to see relationships, can be used for extinct and extant species
Weaknesses: difficult to construct accurate trees, we may choose an unimportant trait and falsely relate/fail to relate species
Phenetic/Morphological Species concept
definition, strength, weaknesses
Identifies species using overall trait similarities
Strength: most intuitive, easiest to makes
Weaknesses: different species look similar (convergence), populations of same species may look different, speciation can occur without a change in appearance
Lamarck theory of evolution
“Ladder of Life”/linear process
implies progress
PROBLEM: all surviving species are equally evolved
Sister taxa
groups that share a common immediate ancestor
Phylogeny
depiction of ancestral relations between species
Pedigree
ancestral relations in a population
Taxon
tip of a branch
Node
speciation event.
most recent common ancestor of sister taxa
Monophyletic group
contains all sister taxa
Paraphyletic group
does not contain all sister taxa
examples: fish, prokaryotes
Polyphyletic groups
includes more than all sister taxa of one monophyletic groups
Polytomy
unresolved branch point
Molecular clock
- mutations occur at a certain rate
- more mutational differences between taxa=branched from a common ancestor longer ago
- therefor longer branches on phylogeny=greater evolutionary distance
Which type of mutations are best for making phylogenies?
Neutral mutations because they are not subject to selection
Parsimony
-uses discrete characteristics (mutations, a trait)
-correct tree is one that has the least character-trait transitions
BENEFITS:
-Simple and fast
DRAWBACKS:
-Less accurate at greater genetic distances
can be misleading if different lineages have different mutation rates
Out-group
taxon that is least related to all other taxa
Distance Matrix Model
-uses continuous or discrete traits
-assumes evolution happens at same rate in all branches
PROBLEMS:
-needs a lot of data for accuracy
BENEFITS:
-more accurate than parsimony
-fast
First nucleic material
RNA because ribozymes (RNA molecules) used to catalyze reactions
Endosymbiont Theory
chloroplast, mitochondria were once free living because have own circular DNA
Mitochondria have a double membrane
Characteristics of prokaryotes
no internal membrane, organelles, nucleus
bacteria and archaea (not a monophyletic group)
extremophiles
archaea that live in extreme environments
extreme halophile
archeae that live in extremely salty environments
ex: dead sea archaea
Extreme thermophiles
archaea living in extremely hot environments
Methanogen
archaea in swamps
produce methane gas as waste product
poisoned by oxygen
digest cellulose
subgroups of bacteria
- chlamydias
- spirocheles
- cyanobacteria
- gram-positive
- Proteobacteria
Obligate aerobes
required oxygen
obligate anerobes
poisoned by oxygen, use fermentation
faculatative bacteria
can do anaerobic and aerobic respiration
reasons for genetic variation in prokaryotes
- high mutation rate
- short generation time
- horizontal gene transfer
transformation
prokaryote takes up DNA from environment and incorporates it into its own
transduction
gene transfer between bactera by bacteriophages
Conjugation
genetic material transferred by sex pili conjugation tube (F factor required to produce pili
Pan Genome
combination of core and dispensible genes of bacteria
Cambrian explosion
new body forms (like hard body parts)
~1/2 billion years ago
evolution of first true animals
fossil record says happened quickly, molecular clock says it took for time
Origin of multicellularity
oxygen revolution
Results of oxygen revolution
-higher metabolic rate
-larger body size
-powered motion
because more energy could be gained from glucose through aerobic respiration than through anaerobic
Homeobox (HOX) Genes
turn on regulatory protiens, transcription factors
result of family of genes created by gene duplication
NOT in prokaryotes or plants
if expressed in wrong location, wrong body part made
Four Co-evolution Relationships
- Predator-Prey
- Host-Parasite/Pathogen
- Plant-Polinater
- Mimicry
Predator-Prey example
Murex strong shell and crab powerful claws
Host-Parasite/Pathogen
host defenses raised, pathogen more virulent
Parasite trade-offs
If parasite more virulent, kills host faster
If parasite less virulent, host infective for longer and probably won’t die
Plant-Polinater
directional selection causes it
If only one insect per plant, insect garunteed food, cross polination less of an issue
Batesian Mimicry
driven by predation
model evolves to not look like mimic mimic evolves to look like model
Evolution of chordates: 4 shared characteristics
- notocords
- nerve cord
- muscular post-anal tail
- Plaryngeal clifts/slits
Craniate
chordates with head
share skull, brain, eyes, other sensory organs
allows for complex movement
neural crest
in craniates, collection of cells near dorsal closing of neural tube in embryo
Notocord
longitudinal, flexible rod between digestive tube and nerve cord.
provides skeletal support
most vertebrates: a more complex bone structure formed
Nerve cord
develops into central nervous system
made of ectoderm
Pharyngeal clefts/slits
in aquatic animals=gills
ears, head, neck in arthropods
Consequences/Purpose of Developmental Genes
increased diversity
new morphological forms
transcription factors that regulate other genes’ expression rate, timing, spatial pattern of adult
characteristics organisms with verebral columns
efficient at capturing prey/avoiding predators enclosed spinal cord backbone elaborate skull fin rays (aquatic form) Example: sea lamprey
Gnathostomes
vertebrates with jaws
most likely evolved from modified skeletal support of pharyngeal slits
Characteristics of tetrapods
4 limbs, feet with digits neck fusion of pelvic girdle absence of gills ears to detect airborne sounds
Challenges of Life on Land
Must counterbalance in less dense air so strong/unflexable bones needed
Distinct vertebral regions/muscle groups to support posture
Limb girdles needed for locomotion
Amniote characteristics
amnion (protects embryo from mechanical shock) yolk sac (nutrients) Allantois (disposal for waste) Chorion (gas exchange)
Humans are different from chimps in five ways
- Transcription factors
- Brain size: body size ration
- Bipedalism
- Reduced jaw size
- Reduced sexual dimorphism
Larger Brain: evolution, consequences
Result of change in transcription factors expression/timing psychiatric disorders (schizophrenia, Alzheimer's) Cancer (results of loss of tumor suppressor gene
Bipedalism: consequences
freeing of hands
painful childbirth
stress in knees, back
non-grasping feet
Jaw Size: evolution, consequences
Result of change in diet
teeth didnt shrink enough for mouth=crooked teeth
Loss of Sexual Dimorphism: evolution of
change in sexual mating system
Multiregional Model
- Homo erectus left Africa and evolved into Homo sapiens independently across globe
- Gene flow between populations prevented speciation
- If true, lots of genetic diversity among human populations and about the same within regions
“Out of Africa” Model
- Homo erectus left Africa and speciated
- Homo sapien evolvd in Africa, migrated, and replaced Homo erectus
- If true, small genetic diversity among human populations and most diversity in Africa
- Evidence for: most genetic diversity is in Africa and genetic diversity among humans is small
