Studied by 270 people
Theory
An explanation of the natural world that has been extensively tested and supported by observation and experiment (not falsified)
T/F: Theories are open to change and even being discarded in light of new evidence?
T/F: True
Life
Carbon based cellular structures with controlled energy conversion (Metabolism), ability to replicate, store and process information, with variations, able to evolve
Louis Pasteur
This person tested which hypothesis about life was correct: spontaneous generation or all cells from cells
Pasteur’s experiment
Set up flasks, one with a flask that doesn’t allow cells in and one that does. This experiment supported the hypothesis that all cells come from existing cells
Panspermia hypothesis
“All seeding” Life originated elsewhere in the universe, and was “seeded” on Earth from space from (comets, asteroids or other cosmic source)
T/F: Was the panspermia hypothesis a crackpot theory?
T/F: no, seeding of complex biomolecules such as amino acids has been proposed, raw materials for life to form?
T/F: amino acids occur in space
T/F: True, amino acids have been found in comets, interstellar dust clouds and carbonaceous meteorites
Other hypothesis for life on Earth
Amino acids are easy on Earth (Stanley L. Miller and Harold Urey classic Life Spark Experiment)
What are Origin of Life experiments?
Biochemistry (Chemical evolution), not biological evolution, which begins with the first population of living organisms
LUCA “Last Universal Common Ancestor” (Theoretical) of Life
Unknown most recent common ancestor of all current life on Earth (not necessarily the first life form, but the first surviving one): basic genes shared by 3 domains
Where did LUCA likely form?
Hydrothermal vents, where energy, raw materials, and other key condition are present in seawater (likely but not confirmed)
What follows the survival of LUCA is what Charles Darwin called ____
Descent with modification, now known as biological evolution
What was LUCA probably the ancestor of?
Archaea (rather than true bacteria)
Until the 1970s, life was classified into 5 kingdoms, which were
bacteria, animals, plants, fungi and protists
Biochemical research, including DNA, confirmed that although both archaea and bacteria are unicellular prokaryotes and look alike, they are fundamentally____
different in their biochemistry (cell wall and membrane composition), and other features
Unicellular prokaryote
no nucleii or organelles
Archaea are called ____: found in extreme environments like hot springs and animal guts
“extremophiles”
Universal Tree of Life
A continually updated phylogeny of the 3 domains of life, based on genetic sequencing of ribosomal RNA, an ancient form of RNA that all life forms in the 3 domains share
Eukaryotes
have larger, more complex cells than prokaryotes, with membrane bound nucleii and organelles, but also have ribosomes (rRNA) inside cells. Animals, fungi and land plants are the most common Eukaryotes seen by humans
What are Eukaryotes more closely related to?
Eukaryotes are more closely related to Archaea than bacteria, based on genetic and biochemical similarities
first evolutionary tree
1837 Darwin’s sketch from his notebook, 22 years before publishing Origin of Species in 1859
Past crossovers in the tree
Some evolution can happen by horizontal transfers of DNA or whole organisms. E: Cyanobacteria gave rise to chloroplasts and proteobacteria are ancestral to mitochondria
Taxonomy
system of classification of organisms
Binomial naming system
Linnaean, all organisms given a binomial name in Latin, comprised of Genus followed by a species name
Alexander von Humbolt
German scientists, naturalist and geographer that has more things named after him than anyone else
Central Dogma of Biology
Based on the discovery of the structure and function of the DNA double helix by Watson and Crick (And Rosaline Franklin and Maurice Wilkins)
Who made the first accepted correct model of the double helix of DNA?
Watson and Crick in 1953
Evolution
The change in the genetic characteristics of a population over time.
Population
Group of individuals of the same species living in the same area at the same time.
T/F: Individuals within a population can evolve
T/F: False, they may live or die, reproduce or not, but only the population can evolve
T/F: Darwin used the word evolution
T/F: False, he used the term descent with modification, for his view of change in organisms, derived from both artificial selection of variations in domesticated animals and plants, and his insight of natural selection in nature
Microevolution today
Microorganisms evolve most rapidly, especially viruses. Covid variants and subvariants like Omicron and Kraken are current examples. Mutations alter spike proteins, changing the ability of mutants to attach to host cells.
On the Origin of Species
Focused on natural selection as the key process of biological change over time
Whose key insights form a foundation of modern evolution today?
Charles Darwin
What are Darwin’s 2 key insights?
Explained how biodiversity came to be a mechanism, documented many examples from both natural and artificial selection
First of Darwin’s key insights
Explained how biodiversity came to be: a mechanism, natural selection acting on a variation. (Although he knew nothing of chromosomes, genes, DNA or other sources of heredity, only that traits are somehow passed from parents to offspring
Second of Darwin’s 2 Key Insights
Documented many examples from both natural and artificial selection that plants and animals are products of descent with modification from ancestral forms.
Ideas before Darwin
Most Classical philosophers and scholars were creationists (Believed that a deity created the universe and all life forms by supernatural means), but some were curious about the natural world
Ancient World: Greece and Rome
Emphasis on mythology, supernatural stories and strange combinations of living things. But some philosophers tries to make sense of nature through careful observations of real organisms
Plato
Greek philosopher Plato claimed that every organism was an example of a perfect essence or type created by god and these types were unchanging
Typological thinking
Every organism thought to be an example of a perfect essence or type created by god and that these types were unchanging. Variations in these species were unimportant noise to understanding origin
Aristotle
Greek philosopher ordered known organisms into the linear great chain of being
Scale of Nature
Linear great chain of being in which species were fixed types, species were organized into a sequence based on size and complexity, sequence started with minerals and lower plants, and humans were at the top of the chain
T/F: Enlightenment was the age of reason
T/F: True, Enlightenment = age of reason
Early hints about changes in nature
Earth formed according to laws of physics and chemistry, older than previously thought, and life emerged as distinct species that could transform when the environment changed
When was the age of reason?
1600-1700s AD
Who proposed the first (but flawed) evolutionary theory (beginning with continual spontaneous generation)?
Jean Baptiste Lamark
What was believed in the Enlightenment?
Life emerged as distinct types that could change when the environment changed and that the earth is formed according to the laws of physics
T/F: Natural selection uses population thinking rather than individual thinking
T/F: true, it uses population thinking
Who claimed that inherited variations among individuals in a population are key to understanding evolution?
Darwin and Wallace
Paleontology
Study of fossils
What had a profound impact on early evolutionary thinking?
Fossils and Paleontology
What fossil was a clear intermediate between reptiles and birds?
the Archaeopteryx
Georges Cuvier
In Paris, fossils resemble but are not exactly the same as modern species. Extinctions are a fact! Very controversial with creationists
Darwin’s timeline
Grew up in Shrewsbury, England in an upper class medial family, then medical school in Edinburgh, trained to become a clergyman at Cambridge, then invited to serve as a unofficial naturalist and gentleman companion
Context for Darwin’s thinking
Aristotle’s great chain of being was still generally accepted and that earth was still very young, and that landforms were fixed
Main purpose of the Beagle voyage
To map the coast of South Africa and voyage around the world making latitude and longitude measurements
How long was the voyage of the Beagle?
5 years, meant to be 2
What did Darwin read?
Principles of Geology by Charles Lyell, and concluded that supernatural processes weren’t needed as explanations for natural processes observed today
What did Darwin find on the Galapagos islands?
A great number of aboriginal creations (endemic species only found there), variation of the same species across the islands, gradation and diversity among birds, and similarities to South American species
Phylogenetic tree
diagram that illustrates the ancestor-descendant relationship among taxa. Illustration of a hypothesis about the ancestor-descendant relationships among taxa based on currently available information. They’re grouped into phylogenetic taxa based on unique shared traits that result from common ancestry.
T/F: Galapagos mockingbirds do not share a common ancestor and are not each others’ closest living relatives
T/F: False, they are in fact each other’s closest living relatives and share a common ancestor
Endemic
A species native and restricted to a certain place
Why did Darwin not release his findings for decades?
He was worried about the social impact of his findings in Victorian England
Who was Darwin’s Bulldog?
Thomos H. Huxley, a biologist
Who was the forgotten evolutionary thinker?
Alfred Russel Wallace was
What did Alfred Wallace find?
Found similar evolutionary ideas as Darwin, found in Malayan region: common ancestry of life forms, natural selection changes species, but lost main collections in ship fire.
What prompted Darwin to publish his theory?
Huxley
When was Darwin’s Most famous book published?
On the origin of species by means of natural selection, or the preservation of favored races in the struggle for life was published in 1859
What did Darwin’s book have in it?
Descent with modification, all species share common ancestry, heritable variations present in all organisms, changes occur through natural selection
Darwin’s 4 Postulates were
Individual variation, inheritance, overproduction, competition
Observation 1 of Darwin’s 4 postulates
Individual variation - individuals within a species vary in traits and characteristics
Observation 2 of Darwin’s 4 postulates
Inheritance, traits are inherited by offspring from their parents
Observation 3 of Darwin’s 4 postulates
overproduction, more individuals are born than can survive in a stable population
Observation 4 of Darwin’s postulates
Competition, individuals compete for resources
Genotypes
Genetic composition of an individual organism’s DNA
Phenotypes
physical expression of the genotype, often referred to as the physical characteristics or traits
Natural selection
Process that sorts the phenotypes of a population (any by proxy also sorts the underlying genotypes
Natural selection: textbook focus
The process by which individuals with certain heritable traits tend to produce more surviving offspring than individuals without those traits, leading to a change in the genetic makeup of the population
T/F; Natural selection can act as any heritable trait (i.e a characteristic based on genetic variation)
T/f: True, it can
Phenotype differences are?
Physical structural differences, physiological and biochemical differences, developmental patterns
Physical or structural differences
body or body part size, shapes, colors, patterns
Physiological and biochemical differences
proteins, structural and regulatory, enzymes and hormones
T/F: traits can also include any genetic differences
T/F: true, DNA changes as small as single nucleotide differences (point mutations), or different DNA sequences, small or large
Conditions for natural selection
There is a heritable (genetic) variation, the variation results in a fitness differential (=advantage or disadvantage to reproduction in the current environment), then that trait will evolve in that population by natural selection
Evolutionary fitness
Not survival alone, but an individual’s contribution of genes to the next generation (i.e reproductive success compared to others)
Physical fitness
Good health or physically in good shape. But not evolutionary fit if no children produced
What determines evolutionary fitness?
number of surviving offspring produced to the next generation (population gene pool)
What was key evidence for Darwin?
Enormous variability potential in species, artificial selection was key evidence for Darwin
Homologous traits
similar structures in descendent organisms can be explained as a result from inheritance from a common ancestor
Homology examples
vertebrates having 4 limbs
Homoplasy
Convergent evolution, a trait that has evolved independently in two different species or organisms not because of a common ancestor
What evidence for the evolution of cetaceans, whales and dolphins, illustrate the idea of internal consistency?
Fossil cetaceans have unique ear bones only found in living and fossil cetaceans, skeletons of fossil cetaceans indicate transitions between terrestrial, amphibious and aquatic forms, vestigial hip and limb bones are found in some living and fossil adult whales and in dolphin embryos
How are vestigial structures evidence for evolution?
provide evidence for common ancestry, ex: whales have a vestigial hip and limb bones. The genetic information to make hind limbs is still there, but has been stopped at some point due to genetic regulation
Directional selection
Changes the average value of a trait
Stabilizing selection (also common)
Average individuals are favored, high fitness = stability. Selection against extreme traits
Before claiming natural selection, must show that
heritable variation exists (is beak depth a heritable trait?) - Yes, offspring inherited the larger beaks of surviving parents
A fitness differential exists (is there an advantage for having different beak depths?) - yes, survival and reproduction was better for birds with beaks larger than average that could crack larger seeds from drought plants
T/F: Natural selection changes individuals
T/f: False, it SORTS them
Corrections about natural selection
individuals can’t evolve, only populations of a species can evolve
Individuals do not select which genes to pass on, reproductive individuals pass on genes that may be advantageous or disadvantageous
Selection (not random) is adaptive, but mutations and genetic drift occur naturally
Natural selection is not purposeful or forward looking, but operates in the present environment
Evolution does not produce perfections, only workable adaptations
Evolution is not goal directed, adaptations don’t occur because organisms want or needs them (ex: roses have thorns because some ancestors had a thorn producing mutation, and survived and reproduced more effectively than those without thorns
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