Biology-Evolution Flashcards
evolution
changes that occur in a population, species, or group of species; changes in allele frequencies in populations over time
microevolution
describes how populations of organisms change from generation to generation and how new species originate; changes in allele frequencies that occur over time within a population (due to mutation, selection, gene flow and drift)
macroevolution
describes changes in groups of related species over broad periods of geologic time; patterns of changes that determine phylogeny
phylogeny
evolutionary relationships among species and group of species
Larmarck’s 3 important ideas
- Use and disuse:
body parts of organisms develop w/ increased usage, while unused parts weaken - Inheritance of acquired characteristics-
body features acquired during the lifetime of an organism ( such as muscle bulk) could be passed on to offspring. This was wrong. - Natural transformation of species-
organisms produced offspring w/ changes, transforming each later generation into a slightly more complex form (no extinction or splits into more species)
natural selection
“survival of the fittest” was the driving force of evolution that is now called Darwinism.
neo-Darwinism, the synthetic theory of evolution, or the modern synthesis
genetics was incorporated into evolutionary thinking, creating a new, more comprehensive view of evolution
evidence for evolution
- Paleontology
- Biogeography
- Embryology
- Comparative anatomy
- Molecular biology
(evidence for evolution) Paleontology
fossils reveal the prehistoric existence of extinct species.
often found in sediment layers, (deepest => oldest specimens). (Large, rapid changes produced new species)
fossil types: actual remains, petrification, imprints, molds, and casts
(evidence for evolution) Biogeography
geography to describe distribution of species; unrelated species in different regions of world look alike when found in similar environment.
ex. rabbits and austrailian hare wallaby
continental drift- supercontinent Pangea slowly broke apart to 7 continents
(evidence for evolution) Embryology
similar stages in development (ontogeny) among related species. The similarities help establish evolutionary relationships (phylogeny)
Gill slits and tails are found in fish, chicken, pig, and human embryos
(evidence for evolution) Comparative anatomy
describes two kinds of structures that contribute to the identification of evolutionary relationships among species: homologous structures and analogous structures
(evidence for evolution) Comparative anatomy: Homologous structures
body parts that resemble one another indifferent species because they have evolved from a common ancestor
(evidence for evolution) Comparative anatomy: Analogous structures
body parts that resemble one another in different species, not because they have evolved from a common ancestor, but because they evolved independently as adaptations to their environments.
The fins and body shapes of sharks, penguins, and porpoises are analogous because they are adaptations to swimming
(evidence for evolution) Molecular biology
examines the nucleotide and amino-acid sequences of DNA and proteins from different species. Closely related species share higher percentages of sequences. In addition, all living things share the same genetic code.
More than 98% of the nucleotide sequences in humans and chimpanzees are identical. AA’s in cytochrome c often compared
natural selection
the differences in survival and reproduction among individuals in a population as a result of their interaction w/ their environment; responsible for producing adaptations (superior inherited traits) that increase individual’s fitness (ability to survive, leave offspring)
fitness
the relative ability to survive and leave offspring
Darwin’s arguments for theory of evolution by natural selection
- Populations possess an enormous reproductive potential: if all offspring produced and survived
- Population sizes remain stable: pop. generally fluctuate around a constant size
- Resources are limited: resources do not increase as pop. grow larger
- Individuals compete for survival: growing pop will exceed available resources => compete
- There is variation among individuals in a population: such as skin color
- Much variation is heritable: DNA is passed down
- Only the most fit individuals survive: survival of the fittest
- Evolution occurs as favorable traits accumulate in the population: best adapted individuals => best adapted offspring leave most offspring.
What are the five types of selection?
- Stabilizing selection
- Directional selection
- Disruptive selection
- Sexual selection
- Artificial selection
stabilizing selection
eliminates individuals that have extreme or unusual traits; individuals w/ the most common trait are the best adapted
bell curve (avg. height in human is in middle); favors an intermediate
directional selection
favors traits that are at one extreme of a range of traits, traits at the opposite extreme are selected against.
After many generations => changes in allele frequencies (such as insecticide resistance)
ex.: insecticide resistance, peppered moth
industrial melanism
the selection of dark-colored (melanic) varieties in various species of moths as a result of industrial pollution
disruptive selection
occurs when the environment favors extreme or unusual traits
example: height variation in weeds of lawns and in the wild
sexual selection (nonrandom mating)
the differential mating of males (sometimes females) in a population
example: females increase fitness by increasing the quality of their offspring by choosing superior males
males increase fitness by maximizing the quantity of offspring produced
What are two kinds of sexual selection?
male competition and female choice
male competition
a kind of sexual selection that leads to contests of strength that award mating opportunities to the strongest males.
ex.: evolution of antlers, horns, and large stature or musculature are examples of this kind of sexual selection
female choice
leads to traits or behaviors in males that are attractive to females
ex: colorful bird plumage or elaborate mating behaviors
sexual dimorphism
differences in the appearance of males and females => becomes form of disruptive selection
artificial selection
form of directional selection carried out by humans when breed animals that possess desirable traits. This is not “natural”
mutations
provide the raw material for new variation. They can invent alleles that never before existed in the gene pool. Most mutations are deleterious, or harmful
sexual reproduction
creates individuals w/ new combinations of alleles. These rearrangements, or genetic recombination (crossing over, independent assortment of homologues, and random joining of gametes)
crossing over
exchanges of DNA between nonsister chromatids of homolgous, occurs during prophase I of meiosis
independent assortment of homologues
during metaphase I creates daughter cells w/ random combinations of maternal and paternal chromosomes
random joining of gametes
during fertilization contributes to the diversity of gene combinations in the zygote
What are sources of variation?
- mutations
- sexual reproduction
- diploidy
- outbreeding
- balanced polymorphism
diploidy
the presence of 2 copies of each chromosome in a cell
in the heterozygous condition (when two different alleles for a single gene locus are present), the recessive allele is hidden and “stored” for future generations
outbreeding
mating w/ unrelated partners, increases the possibility of mixing different alleles and creating new allele combinations
balanced polymorphism
the maintenance of different phenotypes in a population through heterozygote advantage, hybird vigor (heterosis), or frequency-dependent selection (or minority advantage)
heterozygote advantage
occurs when the heterozygous condition bears a greater selective advantage than either homozygous condition
Sickle cell (AA, AS, SS), AS is 14% in Africa because it has resistance against malaria
hybrid vigor (heterosis)
superior quality of offspring resulting from crosses between 2 different inbred strains of plants.
The superior hybrid quality results from a loci reduction w/ deleterious homozygous recessive conditions and an increase in loci w/ heterozygote advantage.
Ex.: a hybrid of corn, developed by crossing 2 different corn strains that were highly inbred, is more resistant to disease and produces larger corn ears than either of the inbred strains
frequency-dependent selection (or minority advantage)
least common phenotypes have a selective advantage. Common phenotypes are selected against. Phenotypes alternate between low and high frequencies , thus maintaining multiple phenotypes.
search image of common phenotypes => rare escape; rare eventually becomes common, cycle repeats
What are fives causes of changes in allele frequencies?
- natural selection
- mutations
- gene flow
- genetic drift
- nonrandom mating
natural selection
increase/decrease in allele frequencies due to the impact of the environment
gene flow
introduction/removal of alleles from the population when individuals leave (emigration) or enter (immigration) the population
genetic drift
random increase/decrease of alleles. There are two kinds: founder effect and bottleneck
founder effect (genetic drift)
allele frequencies in a group of migrating individuals are, by chance, not the same as that of their population of origin
bottleneck (genetic drift)
population undergoes a dramatic decrease in size. (natural catastrophe, predation, and disease)
nonrandom mating
individuals choose mates based upon their particular traits.
There are two kinds that are commonly seen: inbreeding and sexual selection
inbreeding (nonrandom mating)
occurs when individuals mate w/ relatives
Hardy-Weinberg equilibrium (genetic equilibrium)
allele frequencies in a population remain constant from generation to generation => no evolution.
- All traits are selectively neutral (no natural selection)
- Mutations do not occur.
- The population must be isolated from other populations (no gene flow)
- The population is large (no genetic drift)
- Mating is random
how is genetic equilibrium determined?
- Allele frequencies for each allele (p, q)
- Frequency of homozygotes (p^2, q^2)
- Frequency of heterozygotes (pq + qp = 2pq)
Also, the following equations hold:
- p + q = 1 (all alleles sum to 100%)
- p^2 + 2pq + q^2= 1 (all individuals sum to 100%)
for example see pg. 135
species
group of individuals capable of interbreeding.
speciation
the formation of new species, occurs by the following processes: allopatric speciation, sympatric speciation, or adaptive radiation
allopatric speciation
pop. is divided by a geographic barrier so that interbreeding between the 2 resulting pop. is prevented. If the gene pools sufficiently diverge, then interbreeding between the populations will not occur if the barrier is removed
e. g. (mountain ranges, rivers, any region that excludes vital resources
sympatric speciation
formation of new species w/o the presence of a geographic barrier. This may happen through balanced polymorphism, polyploidy, or hybridization
balanced polymorphism
natural selection due to polymorphism.
ex: an insect pop. has a polymorphism for color. Each color provides camouflage to a different substrate, and if not camouflaged the insect is eaten. Under these rules, only insects w/ the same color can mate. Thus, similarly colored insects are reproductively isolated from other subpopulations, and their gene pools diverge as in allopatric speciation
polyploidy
the possession of more than the normal two sets of chromosomes found in diploid (2n) cells.
(3n,4n in plant two viable diploid gametes and two sterile games with no chromosomes => tetraploid 4n zygote formed => repeat with diploid gametes male/female => reproductive isolation with normal gametes)
hybridization
2 different forms of a species (closely related species) mate and produce progeny along a geographic boundary called hybrid zone (more genetic variations => hybrid can live beyond range of either parents)
adaptive radiation
rapid evolution of many species from a single ancestor; occurs when the ancestral species is introduced to an area where diverse geographic or ecological conditions are available for colonization.
What are the two categories of isolating mechanisms?
prezygotic isolating mechanisms- prevent fertilization
postzygotic isolating mechanisms-prevent the formation of fertile progeny
Reproductive isolation: prezygotic isolating mechanisms
- habitat isolation- species do not encounter one another
- temporal isolation- species mate or flower during different seasons or times of day
- behavioral isolation-species does not recognize another species as a mating partner because it does not perform the correct mating ritual
- mechanical isolation- male/female genitalia are structurally incompatible or when flower structures select for different pollinators.
- gametic isolation- male gametes do not survive in the environment of the female gamete do not recognize others
Reproductive isolation: postzygotic isolating mechanisms
- hybrid inviability- zygote fails to develop properly and dies b4 reaching reproductive maturity
- hybrid sterility- hybrids become functional adults, but are reproductively sterile (eggs or sperm are nonexistent or dysfunctional)
- hybrid breakdown- hybrids produce offspring that have reduced viability or fertility
what are the four patterns of evolution?
- divergent evolution- describes 2 or more species that come from a common ancestor and have become different over time
- convergent evolution- describes 2 unrelated species that share similar traits because each adapted to similar ecological lifestyles/conditions
- parallel evolution-describes 2 related species that have made similar evolutionary changes after their divergence from a common ancestor
- coevolution-evolution of 1 species in response to new adaptations that appear in another; occurs bet. predator/prey, pollinators/flowering plants, pathogens/animal immune systems
macroevolution
patterns of evolution for groups of species over extended periods of geologic time
What are the 2 macroevolution theories?
- phyletic gradualism-argues that evolution occurs by the gradual accumulation of small changes. Individual speciation events/major changes in lineages occur over long periods of geologic time.
- punctuated equilibrium- evolutionary history consists of geologically long periods of stasis w/ little/no evolution, interrupted, or “punctuated” by geologically short periods of rapid evolution. The absence of fossils revealing intermediate stages of evolution is considered data that confirms rapid evolutionary events
chemical evolution
describes the processes that are believed to have contributed to the formation of the first living things.
heterotroph theory
proposes that the first cells were heterotrophs (incapable of making their own food)
origin of life
- the earth and its atmosphere formed (CO, CO2, H2, N2, H2O, S, HCl, HCN, but little to no O2)
- the primordial seas formed (gases condensed into water and minerals as earth cooled)
- complex molecules were synthesized (formation of org. soup from inorganic, energy from UV, lightin, heat, radiation => acetic acid, formaldehyde and amino acids
- Polymers and self-replicating molecules were synthesized
- Organic molecules were concentrated and isolated into protobionts
- primitive heterotrophic prokaryotes formed
- primitive autotrophic prokaryotes were formed
- oxygen and the ozone layer formed and abiotic chemical evolution ended
- eukaryotes formed
origin of life: where did the energy come from that catalyzed the formation of organic molecules from inorganic molecules?
came from mostly UV light, but also lightening, radioactivity, and heat
origin of life: who were A.I. Oparin and J.B.S. Haldane?
they independently theorized that simple molecules were able to form only because oxygen was absent
origin of life: who was Stanley Miller?
he tested the theories os Oparin and Haldane by simulating an experiment under primordial conditions
origin of life: protenoids
abiotically produced polypeptides. They can be experimentally produced by allowing amino acids to dehydrate on hot, dry substrates
origin of life: protobionts
the precursors of cells; able to carry out chemical reactions enclosed within a border across which materials could be exchanged, but were unable to reproduce.
origin of life: microspheres and coacervates
are experimentally (and abiotically) produced protobionts that have some selectively permeable qualities
origin of life: endosymbiotic theory
eukaryotic cells originated from a mutually beneficial association (symbiosis) among various kinds of prokaryotes. Specifically, mitochondria, chloroplasts, and other organelles established residence inside another prokaryote, producing a eukaryote
What is evidence for the endosymbiotic theory?
- mitochondria and chloroplasts posses their own DNA. The DNA is circular and “naked” (w/o proteins) as is the DNA of bacteria and cyanobacteria
- Ribosomes of mitochondria and chloroplasts resemble those of bacteria and cyanobacteria, with respect to size and nucleotide sequence
- Mitochondria and chlorplasts reproduce independently of their eukaryotic host cell by a process similar to the binary fission of bacteria.
- Mitochondria and chloroplasts have 2 membranes (both phospholipid bilayers). The 2nd membrane could have been acquired when the introduced prokaryote is surrounded , in endocytosis fashion, by a vesicle produced by the host prokaryote.
- The thylakoid membranes of chloroplasts resemble the photosynthetic membranes of cyanobacteria
(evidence for evolution) Comparative biochemistry
organisms w/ common ancestor = common biochemical pathways
neutral variation
variation w/o selective value (e.g. fingerprints in humans)
geographic variation
variation of a species dependent on climate or geographic conditions. A graded variation of a phenotype due to this is known as a cline; variation from north/south environments is a north-south cline
Universe age
12-15 billion years old
solar system age
4.6 billion yrs old
earth age
4.5 billion yrs old
fossil age
3.6 billion yrs old
photosynthetic bacteria age
2.3 billion yrs old
eukaryotic bacteria age
1.5 billion yrs old
Miller and Urey
used ammonia, methane, water and hydrogen sealed + simulated lightning => saw several organic molecules, AA’s, starting materials, but no NAs!
What was the modern atmosphere like?
78% nitrogen, 21% oxygen, 1% argon, then a lot of other less important gases
vestigial structures
structures that appear to be useless but had ancestral function; ex humans (appendix and tail), horses (splints), python (legs reduced to bones)
mullerian mimicry
2 or more harmful species that are not closely related, and share 1 or more common predators, have come to mimic each other’s warning signals
batesian mimicry
deceptive; harmless species has evolved to imitate the warning signals of a harmful species directed at a common predator
gene pool
all the alleles for any given trait in the populaiton
anagenesis/phyletic evolution
one species replaces another, straight path evolution
cladogenesis/branching evolution
new species branches out from parent species
deme
small local population (e.g. all the beavers along specific portion of a river)
general categories of living organisms
autotrophic anaerbones (chemosynthetic bacteria), autotrophic aerobes (green plants, photoplankton), heterotrophic anaerobes (yeast), heterotrophic aerobes (amoebas, earthworms, humans)
symbiosis
relationship between 2 species. Can be: mutualism (beneficial/beneficial), commensalism (beneficial/neutral), parasitism (beneficial/detrimental)
