Studied by 20 peopleevolution
change in the heritable characteristics (aka gene frequencies) of a population over time
fact: change has occurred
theory: how and why the change has occurred
comparative anatomy
study of similarities and differences between living things
homologous structures
structures inherited from common ancestor
shared among closely related species
can have similar or different functions
ex: mammal forelimbs
divergent evolution
organisms that share a recent common ancestor develop different traits due to their different environments
underlying “blueprint” for creating many structures is the same, creating homologous structures
analogous structures
similar functions
arent structurally related
dont show common descent
due to convergent evolution
ex: wings of insects and bats/birds
convergent evolution
organisms occupying similar roles and exhibiting similar traits
embryology
study of how organisms develop before birth/hatching
fossil
preserved remains or traces of ancient organisms
visual evidence of change over time
transitional fossils
organisms “in between” two species
law of superposition
older layers of earth on bottom, younger layers on top
radiometric dating
analyzing radioactive compounds in materials to determine a more exact age
ex: carbon dating
molecular evidence (for evolution)
closely related organisms have more similar DNA sequences and more similar amino acid sequence of shared proteins
molecular clock
measures time from changes in DNA
number of differences increase over time
hypothesis: DNA and protein sequences evolve at a rate consistent over time and consistent among different organisms
selective breeding
humans carefully controlling the breeding of certain plants and animals
resulting organisms show drastic differences compares to wild counterparts (evidence for evolution)
vestigal structures
inherited structures that have lost much of their original functions
stick around because theyre coded in DNA
ex: whales’/dolphins’ pelvic bones
biodiversity
diversity of life on earth
variety of living organisms (plants, animals, & microorganisms)
contains genetic/species/ecosystem diversity
comparing biodiversity:
different geological time periods have different biodiversity levels
evidence: fossils (fossil record = incomplete)
current time period = more diverse than past
genetic variation
differences in genomes among individuals of the same species
created randomly without a goal
essential for natural selection
fundamental aspect of life
genetic mutation
mechanism of evolution
any change in the DNA sequence of an organism
errors in copying the genetic information during DNA replication
results in alleles or other forms of a gene
most are neutral but can be harmful or beneficial
selection pressures
factors that lead to difference in survival or reproduction
causes a change in genetic composition of a population
density-dependent factors
affect the size of the population
depend on the density or the population in a given area (availability of food, finding mates, presence of predators, etc)
biological fitness
ability of an organism to survive and reproduce, pass on genetic material to offspring
determined by environment, survival value, reproductive potential
intraspecific competition
individuals of the same species compete with each other for resources
interspecific competition
individuals of different species compete with each other for resources
sexual selection
focused on finding mate and reproducing
intrasexual selection
males competing for mate, females competing for mate
intersexual selection
individuals of one sex (often female) choosing an individual of the opposite sex as a mate
gene pool
sum total of all the alleles of all the genes present in a population
indicator of the genetic variation that exists in a population
large gene pool indicates extensive genetic variation, greater ability to adjust and adapt
genetic drift
mechanism of evolution
change in allele frequencies in the gene pool of a population
due to random events
greater impact if populations are small/geographically isolated
can occur as the bottleneck effect or the founder effect
cant be caused by selective pressures (if so, then it would be natural selection)
allele
different versions of genes
gene pool
all of the genes and alleles within a population
gene flow
mechanism of evolution
aka genetic migration
occurs when organisms from one population move to a new area, genes “flow” into new population’s gene pool
gene flow in humans increased as travel increased
natural selection
inherited variations exist in populations and organisms with successful variations will better survive, reproduce, and pass their variations to next generation
mechanism of evolution
variation
same species, some differences
some variations are not inherited (natural selection only works on inherited variations)
random
descent with modification
sexual reproduction, offspring having variations from parents and from each other
inherit (descend) from parents (with some modifications or variations)
common descent
all living things are related
share a common ancestor
adaptation
noun: any variation that helps survival
process: populations change so there is a higher percentage of organisms with favorable traits (adaptations, because adaptations allow for more reproduction)
only works if favorable traits are inherited
more adaptations leads to higher fitness and more reproduction
structural adaptations
variations in body of organisms
ex: color, shape, patterns, etc
mimicry, camouflage
behavioral adaptations
variations in instincts
ex: fight or flight, mating behaviors, food retrieval methods, etc
physiological adaptations
variations in metabolic processes
common in bacteria, insects, and plants
ex: antibiotic/pesticide resistance
selective pressure
choose what traits are beneficial/detrimental
predation
traits in prey that cause them to be selected against
traits in predators that cause them to be selected for
physiological selective pressures
disease/antibiotic resistance
metabolic efficiency
sexual selective pressures
traits that increase mating success (help with direct competition and attracting a mate)
results in sexual dimorphism
sexual dimorphism
differences between sexes in secondary sex characteristics
directional selection
one extreme is favored over the others
stabilizing selection
the middle is favored over both extremes
disruptive selection
both extremes are favored over the middle
binomial distribution
mechanisms of evolution
natural selection
gene flow
genetic drift
genetic mutation
bottleneck effect
random natural events such as earthquakes or tsunamis can lead to sudden decreases in populations
new population might not represent genetic diversity of original population
founder effect
small subset of population breaks away to colonize new area
may not be exact genetic representation of the original population
neo-darwinism
phenotype is largely a product of the genotype
natural selection increases frequency of beneficial alleles
genetic drift and gene flow can also bring changes in gene frequencies
mutation
ultimate source of genetic variation
stabilizing selection
favors average individuals with intermediate forms of the trait
eliminates the extremes
results in loss of genetic diversity
directional selection
favors one extreme form of the trait over all other forms
most seen when environment changes
disruptive selection
both extreme forms of the trait are favored over the intermediate forms
hardy-weinberg principle
in a stable population, frequency of alleles would remain constant generation after generation
p2+2pq+q2=1
equation helps calculate the genotype frequencies of homozygous dominant, heterozygous individuals, and homozygous recessive individuals
Conditions:
No mutations
Random mating
No natural selection
No genes should enter or leave population
Large population
artificial selection
similar to natural selection
perpetuated by humans
humans select organisms with desirable traits
Molecular phylogeny
can determine how closely two species are related at a molecular level
more similar genes/proteins indicate more closely related
species
a group of potentially interbreeding populations
defined by reproductive compatibility
similar organisms can mate and produce viable and fertile offspring
Speciation
process by which new species arise
splitting of one ancestral species into two or more descendant species that are different and can not interbreed
creates new gene pool
reproductive isolation
all barriers that prevent populations of the same species from interbreeding and/or producing fertile offspring
geographic isolation
reproductive isolation due to geographical barriers
ex: river, dam, road, large distance between populations, etc
allopatric speciation
nothing but geographical isolation
population split into two and evolve separately
sympatric speciation
new species is formed in the same location
due to isolating mechanisms, behavioral/temporal isolation
temporal isolation
differences in the timing of the reproductive cycle (mating seasons, gamete production, etc)
behavioral isolation
differences in mating rituals (courtship dances, mating calls, etc)
prezygotic barriers
barriers that prevent formation of the zygote, prevent mating
postzygotic barriers
barriers after zygote is formed, after fertilization
inviability, sterility, etc
adaptive radiation
rapid evolution of an ancestral species in different lines to utilize the avaliable ecological niches/jobs
hybridization
interbreeding between two species that leads to a new species
new species often reproductively isolated from parent species
more common in plants
pre/postzygotic barriers exist
polyploidy
caused by non-disjunction of chromosomes during cell division (mitosis or meiosis)
caused by a diploid cell or organism acquires one or more additional sets of chromosomes
allopolyploidy
special case of polyploidy
hybrid that has multiple chromosome sets that are derived from the different parental species
can be considered sympatric speciation
morphological characteristics
physical characteristics
species
class of organisms
classified by shared morphological characteristics (Linnaeus created this system)
tend to look more similar to each other
named using both genus and species names (genus comes first, species is all lowercase, ex: Homo sapiens)
different species sharing a genus have some common characteristics
sexual dimorphism
males and females have very different characteristics
chromosome
allow DNA to be accurately copied during cell division
each species has a set number of chromosomes, common to all members of species
within nucleus of cells, only eukaryotes
number of chromosomes is a shared trait among species
karyotyping
involves isolating condensed chromosomes taken from actively dividing cells
individual chromosomes are stained to highlight banding patters
shown in a karyogram
karyotype can determine sex
genome
stores all genetic information of an organism
single-nucleotide polymorphisms (SNPs)
occurs when a single nucleotide is replaced with another
causes variation and diversity
genome size
amount of DNA in a haploid cell
different species’ genomes vary in size and sequence
not directly correlated to either organism size or complexity
exceptions to the biological species concept
when two species have same number of chromosomes so hybrid would have an equal amount of pairs
horizontal gene transfer cases variation in asexually reproducing organisms (can be organisms of different species)
dichotomous key
tool used in fieldwork to aid in the identification of organisms
composed of binomial questions/statements based on physical characteristics (ex: fur or no fur, antlers or no antlers, flat antlers or round antlers)
DNA barcoding
unknown specimen/environmental sample (typically water or soil) is collected, DNA is extracted
identified specific DNA sequences
creates a unique “barcode” which is compared to a catalog of other barcodes
helps measure biodiversity
classification
sorting and organizing of things or ideas into groups or categories based on a set of criteria
developed mainly by Carl Linnaeus
hierarchy of taxonomy
domain
kingdom
phylum
class
order
family
genus
species
cladistics
—
molecular evidence
provide the most unbiased evidence that two species belong to the same clade
cladistic analysis
technique in evolutionary biology
based on the idea that shared genetics or traits that have been passed down from a common ancestor are what identify a clade
compare base/amino acid sequences of several organisms within species
clade
group of species with a single common ancestor and a set of common traits/characteristics
must include all species descended from specific common ancestor
cant include any species that dont share common ancestor
hierarchical and can be subdivided into smaller groupings
calibration point
in molecular clock analysis
period of time in which the precise moment that two species diverged is known
caldograms
used to compare traits of various organisms and explore evolutionary links
Kingdom eubacteria
cell type: prokaryote
cell number: unicellular
mode(s) of nutrition: photosynthesis or other organisms
reproduction: asexual
cell wall: made of peptidoglycan
motility: yes, if flagella or cilia
environment: everywhere, in/on other organisms
example: E. coli
kingdom archaebacteria
cell type: prokaryote
cell number: unicellular
mode(s) of nutrition: chemosynthetic or other organisms
reproduction: asexual
cell wall: yes, not made of peptidoglycan
motility: yes, if flagella
environment: extremophile
example: colors in morning glory pools (Yellowstone)
Kingdom anamalia
cell type: eukaryotes
cell number: multicellular
mode(s) of nutrition: internal digestion
reproduction: mostly sexual
cell wall: no cell wall
motility: various ways
environment: aquatic and terrestrial
example: zebra
kingdom plantae
cell type: eukaryote
cell number: multicellular
mode(s) of nutrition: photosynthesis
reproduction: mostly sexual
cell wall: cellulose
motility: not motile
environment: aquatic and terrestrial
example: daisy
kingdom fungi
cell type: eukaryote
cell number: mostly multicellular
mode(s) of nutrition: external digestion
reproduction: mostly sexual
cell wall: chitin
motility: not motile
environment: terrestrial
example: mushrooms
kingdom protista
cell type: eukaryote
cell number: mostly unicellular
mode(s) of nutrition: mostly autotrophic
reproduction: mostly asexual
cell wall: sometimes
motility: flagella or cilia
environment: mostly aquatic
example: algae
morphological species concept
species are categorized based on shared morphological (physical) characteristics
does not capture the full picture
sex chromosomes
not homologous
play major role in sex determination
23rd pair in humans
XX (female) or XY (male)
biological species concept
defines a species taxon as a group of organisms that can successfully interbreed and produce fertile offspring
addresses two issues with morph. species concept
issues:
cant apply to asexual reproduction
horizontal transfer of DNA
hard to determine exact point of speciation in eukaryotes
Note
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