Quiz 1 Content - BIEB150

Biological (organic) evolution

change in the frequency of heritable characteristics of biological populations over successive generations

results in transformation of species over time, including:

• changes of traits that occur within species

• the genes that encode these traits

• the origin of new species

what evolves?

everything, plants, animals, fungi, bacteria

gene/genotype

sequence of DNA that codes for a molecule, the functional unit of heredity

phenotype

observable traits

four evolutionary processes:

mutation, migration, drift, and selection

migration

the movement of individuals or genetic material between populations, introducing new genetic variation and influencing adaptation, speciation, and population differentiation

drift

fundamental, random mechanism where allele frequencies in a population change over generations due to chance events, rather than natural selection

population differentiation

the accumulation of genetic and phenotypic differences between geographically and ecologically separated populations of a species

Why did “sabre teeth” evolve in Smilodon, musk deer, walruses

and the extinct gorgonopopsids (extinct relative of mammals)?

an optimal, highly effective specialized weapon for puncturing, tearing, and delivering quick, lethal wounds to large prey

Why does the order of Chiroptera include 1500 species of bats but Pholidota only includes 8 species of pangolins?

evolutionary adaptations that allowed bats to unlock vast ecological niches, while pangolins specialized into a narrow, restricted niche

if something is heritable it can ____

evolve

What are evolutionary biologist particularly interested in?

what is happening in between generations, why genotypes/phenotypes change in frequency across generations

earth was formed:

4.54 billion years ago

life emerged:

roughly 3.8 billion years ago

all life descends from one single common ancestor:

around 3.5 billion years ago

400-700 million years

bombardment of meteors

1.5 billion years:

LUCA, last common universal ancestor

1.7 billion years:

bacteria begin to produce oxygen, oxygen now affecting organisms, led to 1st mass extinction because oxygen is toxic to most organisms

2 billion years:

great oxygenation event where oxygen was no longer captured by oceans or land. So begins a significant increase in the atmosphere

3.5 billion years

first plant life appears, probably in the form of green algae

Aristotle and the Great Chain of Being

• arranged all life into “bins” on a scale from lower to higher

• from lower to higher: minerals and ores, elements, plants, animals, humans, angel-like beings, angels, God

carl linnaeus (1707-1778)

• made Linnean taxonomy, binomial nomenclature

• species, genus, family, order, class, phylum, kingdom

• believed species were created and remained invariant over time

• believed earth is very young, 4,000 years old

problems with work from Linnaeus and Aristotle:

• heavily influenced by contemporary religious beliefs

• thought the earth was young and static

• organisms are unchanging

• paleontologists uncovered data to challenge these assumptions

George Cuvier (1769-1832)

• “father of palaeontology”

• found that fossils differed from living species, discovered extinction from this idea

• discovered extinction from finding a mastadon/mammoth bone and realized an animal of that size would’ve been found if it currently existed

Cuvier stratigraphy in Paris:

• discovered that there are several alternating marine and terrestrial deposits

• evidence of catastrophic events (floods) that eradicate species

Cuvier catastrophism

the idea that Earth’s features and life are shaped mainly by sudden, extreme events (e.g. mass extinctions), rather than slow, gradual change key point is that he believed in sudden events

Cuvier evolution/extinction beliefs:

• did not believe that species evolve

• did find extinction to explain disappearances in fossil record

James Hutton (1726-1797) and Charles Lyell (1797-1875)

changes in the earth’s crust due to slow continuous process known as “uniformitarianism”, earth is much older than previously thought

Jean-Baptiste Lamarck (1744-1829)

• one of the first to recognize evolution, but got a few things wrong

• was still working w the great scale from lower to higher organisms

• to explain microbes, he suggested that life was still being spontaneously generated, but evolved into more complexity

• also believed in “the inheritance of acquired characteristics” (law of Use and Disuse)

inheritance of acquired characteristics/examples of aquired characteristics:

tattoos, circumcision, piercings, hair color (when dyed), injuries

what is an example where Lamarck may have realized acquired characteristics are NOT inherited?

circumcision

what did Darwin know about?

• Linnean grouping of species into taxa

• gradual geological change (Hutton and Lyell)

• extinction and species turnover (Cuvier and others)

• Lamarckian ideas about evolution

• knew Earth is old

Who was Darwin’s inspiration for his trip on the HMS Beagle in 1836?

Alexander von Humboldt, explored the Andes in South America

HMS Beagle Journey:

• journey took 5 years

• very cramped quarters

• darwin was often sea-sick

Galapagos:

volcanic islands off the coast of Ecuador, not much there

Darwin didn’t pay much attention to what animals on the Galpagos?

tortoises and finches

what animal did Darwin pay attention to?

mockingbirds

What did Darwin notice about the ground-finches?

nearly perfect graduation in beak size, ranging from narrow-thick and short-long

What do the finches beak adaptations say about them?

adaptation to different diets

What did Darwin notice from rich people breeding pigeons for fun?

that selective breeding may lead to differences in phenotypes of the pigeons

Alfred Wallace (1823-1913):

• traveled the world and came up with the same ideas Darwin had of natural selection and descent with modification

• he reached out to Darwin, and Darwin realized he needed to publish his ideas first

what were Darwins two big ideas and how did he figure them out?

• ideas: descent with modification and natural selection

• realized in his field work that some species fit their environment and that their behaviors aligned with their environment

• pigeon breeding showed descent with modification I thinkkkk

descent with modification definition:

• all species, living and extinct, have descended, without interruption, from one of a few original forms of life

• species that diverged from a common ancestor are at first similar, but then accumulate differences over greater spans of time

• Darwin also included extinction, showing lineages that fizzled out over time

What does descent with modification imply?

species are nested into each other/share common ancestors

if descent with modification is correct, what should there also be evidence for:

• species change through time (microevolution)

• lineages split to form new species (speciation)

• novel forms derive from earlier forms (macroevolution)

• species are not independent but connected by descent from a common ancestor (common ancestry and homology)

• Earth and life on Earth are old (deep time)

natural selection definition:

• differential reproductive success (survival and/or reproduction) of individuals that differ in one or more characteristics

• explains how the traits of a population change over time and why organisms are suited to their environment

How did Darwin discover natural selection?

through observation of artificial selection in pigeons where they developed weird phenotypes, morphology, and behavior

example of natural selection:

large beaks during a drought were the only bird type that survived because it allowed them access to the drought resistant seeds/food

Darwin’s four postulates for Evolution by natural selection:

1) individuals vary in phenotype

2) some phenotypic variation is passed to offspring

3) more offspring are produced than can survive and/or reproduce

4) survival and reproduction are not random, but related to aspects of phenotypic variation

key points about natural selection and evolution:

• natural selection does not necessarily mean evolution will occur

• this is because natural selection can occur without genetic (heritable) changes

• evolution can occur without natural selection (random changes) but change must be heritable

• evolution via natural selection is a non-random change in a heritable characteristic

distinguishing between pattern and process:

• evolution is a pattern

• natural selection is a process

• this is crucial as evolution and natural selection do NOT have to go in unison

what do we call traits that have evolved due to natural selection?

adaptations, these are characteristics that enhance the survival or reproduction of organisms that bear them, relative to alternative character states, note all adaptations evolve by natural selection

ex of adaptations: color matching environment, no eyes in cave fish/dark environments

succulant leaves in SD as an example of natural selection:

plants with large, fleshier leaves can store more water, which helps individuals survive droughts

Darwin’s theory of heritability:

pangenesis theory - gemmules that were seeds which wander from each organ to the gonads and then are passed on to the next generation

Francis Galton:

• Darwin’s cousin

• tested pangenesis theory

• used white and brown rabbits

• blood transfusion between white and brown rabbits to see if white rabbit would give rise to brown rabbit

Who’s work replaced Darwin’s theories about heredity?

Gregor Mendel, genes don’t blend instead:

• there are dominant and recessive alleles

• alleles are maintained and not ‘blended’

• there is segregation in further generations

Discovery of DNA and the genetic code:

1950’s by James Watson, Francis Crick, and Maurice Wilkins

Discovery of DNA allowed to study molecular evolution:

• Motoo Kimura

• able to understand the “particles” of evolution

• observe and study actual mutations, the source of genetic variation

• Motoo Kimura proposed the neutral theory of molecular evolution, which emphasized that many genetic changes are driven by genetic drift rather than natural selection

Modern synthesis:

1) recognizes several mechanisms of evolution in addition to natural selection. one of these, random genetic drift, may be as important as natural selection

2) characteristics are inherited as discrete entities called genes. variation within a population is due to the presence of multiple alleles of a gene

3) speciation is (usually) due to the gradual accumulation of small genetic changes. this is equivalent to saying that macroevolution is is simply a lot of microevolution

whole genome sequencing:

• first organisms to have entire genome sequences was haemophilus influenzae in 1995

• first multicellular eukaryote was Caenorhabditis elegans in 1998

• human genome was completed in 2001

• since then, sequencing technology has imporved dramatically and thousands of taxa have been sequenced

whole genome sequencing and evolution:

• patterns of species relatedness using phylogenies

• the genes involved in adaptation

• the evolution of genomic structure

• the role of microbiomes in evolution

Evidence of evolution

evolution has passed more tests than almost any other idea in biology

5 types of evidence supporting evolution as a process:

1) micro-evolution

2) macro-evolution

3) speciation

4) descent from common ancestor

5) deep time

microevolution

• change in the heritable traits of a population across generations

• seen WITHIN a species

• can happen quite rapidly (generation) misconception that evolution takes millions of years

• changes due to 4 processes: mutation, selection, gene flow and genetic drift

microevolution examples:

• antibiotic resistance

• bull-headed dung beetles, within 40 years adapted to winter in Canada and summer in Florida

• stickleback

• malaria resistance within 20 years

speciation

• the process by which new species arise

• single variable population

• differentiated populations connected by gene flow

• distinct reproductively isolated species

• increasing reproductive barriers over time

definition of a species:

species are groups of actually or potentially interbreeding populations, which are reproductively isolated from other such groups

speciation - ring species

• exemplify the speciation continuum

• at the end of a barrier there are 2 populations coming together that are reproductively isolated

• in contrast, adjacent populations on either side of the barrier are able to mate successfully

ring species example:

salamanders of california, lineages split in central valley of california

speciation - ecological speciation in timema stick insects

• two different insects, one that is stripy and one that is flat to blend with environment

• different timema live and feed on different host plants and have adapted to these different lifestyles

• divergence of some populations living on different hosts is recent and individuals from different plants can sitll interbreed when they encounter each other

• this suggests this is a case of speciation still in action

macroevolution

• fossils!

• don’t have DNA

macroevolution example:

a woolly mammoth and an american mastodon differ in several key traits. studying their evolutionary history helps us understand why these differences evovled

macroevolution - temporal patterns of succession - the modern horse

• fossils with more ancestral traits are found in older layers of rock compared to more derived forms

• when we look across layers of rock we can find evidence of how traits evolve across time

pakicetus is an example of?

macroevolution into a whale, land to aquatic animal

macroevolution - transitional fossils, archaeopterix

• we expect to find evidence of transitions between forms within the fossil record - what Darwin called “transmutation of species”

• Archaeopterix has the wings and feathers like birds but sharp teeth and claws like many non-avian mesozoic dinosaurs

• transitional fossil has a combination of traits characteristic of different groups

is archaeopteryx ancestor of all birds?

no, close relative but not direct ancestor

macroevolution - Tiktaalik

• Tiktaalik sheds light into the timepoint where the very first fish ventured onto land

• 375 million years old

• had fish-like gills and scales AND limb bones similar to contemporary land animals

common ancestry and homology

• descent from a common ancestor was a key prediction of Darwin’s theory

• phylogenetic trees reflect the smilarities between ancestors and descendents

• homology is the term used to describe the similarity of traits between species dues to descent from a common ancestor

• closely related species have more shared traits

• more distantly related species have more differences due to a greater length of time evolving independently

evidence of common ancestry and homology

• all forms of life share certain traits

• nucleic acids encode genetic info

• lipids, proteins

• unlikely for these complex systems to evolve independently multiple times

• we all share common ancestor

ex of homology:

human arm, dog leg, bird wing, whale fin, chicken wings

ancestry/homology - vestigial organs

traits that have lost allo r part of their ancestral function

ex: appendix we have no use for it now

deep time

• Darwin’s theory suggested that the earth and life on it were old

• from geologists who have used isotopic analyses to look at radioactive decay we know earth is about 4.5 billion years old

• banded formations of rock

• earliest fossil evidence of life on earth is of stromalites. these are 3.7 billion years old

• age was determined using radiometric dating

• they are layered rock structures made by photosynthetic cyanobacteria (trace fossils)

deep time - banded iron formations

• ancient marine rocks with silica and iron alternating layers

• show when life altered earth’s chemistry

• younger layers have no red sediment

• microbes made rust bc they started to produce oxygen

stromatolites/cyanobacteria

first fossil evidence on earth

corn/maize

example of artificial selection

another example of artificial selection:

evolution of chickens, bread to grow bigger and faster

are dogs their own species - morphological species concept

yes they have strong phenotypic differences

are dogs their own species - biological species concept

no, they can interbreed produce hybrids

are dogs their own species - evolutionary species concept

no dogs are nested within grey wolves, however coyotes are their own species

silver fox domestication experiment

• studied process of domestication with foxes, for the last 67 years since 1959

• over six generations they produced foxes that could be handled and pet, wagged their tails, and whined when humans left

• foxes also differed in their physical characterstics

pleiotropy

single gene influences multiples traits in an organism

genetic linkage

genes nect to each other can cause indirect selection for other traits

Darwin’s four postulates for evolution by natural selection:

1) phenotypic variation

2) aomw phenotypic variation is passed to offspring

3) more offspring are produced than can survive and/or reproduce

4) survival and reproduction is not random, but related to aspects of phenotypic variation

phenotypic variation:

• ladybugs, ears, dog fur

• hieght distribution

• phenotypic variation represents the raw material for selection to act on

heritability of phenotypic variation

• heritability can be quantified by looking at the relationship between the average parent phenotype and the offspring phenotype

• low heritability graphed as scattered

• high heritability, linear correlation

ex of a trait with high heritability:

• body height

• great tits plumage

is human behavior heritable?

• substance abuse shows weak but consistent patterns

• environment is much more important for substance abuse

many traits are heritable to:

some degree, a lot of phenotypic variation is dependent on the environment

ex: being gay

more offspring are produced than survive/reproduce:

• when many offspring are produved eventually resources become limiting

• under these conditions there is fierce competition

• many of the offspring will die from lack of resources, predation or disease

• in natural populations only a fraction of offspring will survive or reproduce

survival and reproduction is not random

ex is surviving better when coloration matches habitat