Lecture 2: Evidence of Evolution Flashcards
- Species are immutable (do not change).
- Variation among individuals is limited.
- Lineages do not split.
- Species are created separately and independently →
genealogically unrelated. - Earth and its living creatures are young (~6,000 years
old). - John Ray (1686): “One species never springs from
the seed of another.”
Theory of Special Creation
Theory of Special Creation
* Species are __ (do not change).
* Variation among individuals is __.
* Lineages __.
- immutable
- limited
- do not split
Who said “One species never springs from
the seed of another.”
John Ray (1686):
Theory of Evolution: Descent with Modification
Species are not immutable → __
change over time
Theory of Evolution: Descent with Modification
Lineages split and diverge = __.
speciation
average beak size may change from one generation to the next
microevolution
Theory of Evolution: Descent with Modification
Over long periods of time, novel forms of life can derive from earlier forms = __.
macroevolution
(major points) Theory of Special Creation
- immutable
- limited
- genealogically unrelated
- earth is young
Theory of Evolution: Descent with Modification
Species are derived not independently but from common (shared) ancestors (genealogically related) = __
common ancestry
Earth and life are considerably more than __ years old
6,000
(major points) Theory of Evolution: Descent with Modification
- microevolution
- speciation
- macroevolution
- common ancestry
is simply a change in gene frequency within a population and can be observed over short periods of time, e.g., between one generation and the next
microevolution
examples of microevolution
- Evolution of antibiotic resistance
- mosquitoes evolving resistance to dichlorodiphenyltrichloroethane (DDT)
- gonorrheal bacteria strains evolving resistance to penicillin
- HIV strains evolving resistance to antiviral medicines
evidence of microevolution
- Selective breeding
- Direct observation of natural populations
- Anatomy of living species
- small herb that depends on a rainy season that runs from winter to spring
- individuals germinate, grow, flower, set seed, and die within a single year
- evolved flowering time
Brassica rapa
In mid-1990s, seasonal rains lasted into late spring = __
B. rapa __ → __ → __
- long growing season
- delays flowering –> grows larger –> make more seeds
In early 2000’s, seasonal rains ended early = __
B. rapa __ → __
- short growing season
- flowers early –> higher reproductive success
a useless or rudimentary version of a body part that has an important function in other, closely allied, species.
vestigial structure
vestigial features examples
- brown kiwi - useless wings
- royal python - spur (tiny remnant hindlimb)
human vestigial structures
- coccyx (rudimentary tailbone)
- arrector pili (a muscle at the base of each hair follicle, hair stands up when it contracts) chimpanzees
What is a species? Species are populations, or groups of populations, within and among which individuals actually or potentially interbreed and outside of which they do not interbreed → __ by __
- Biological Species Concept
- Ernst Mayr
How do we say if individuals belong to different species?
if individuals from different populations are:
[a] disinclined to mate, or
[b] mate but fail to produce healthy, fertile offspring
Evidence for speciation
- Evidence from laboratory experiments
- Evidence from natural populations
an RNA virus that infects Pseudomonas syringae
Φ6
Evidence for Speciation: Laboratory experiments
- The case of Bacteriophage Φ6
- The case of Drosophila pseudoobscura
The case of Bacteriophage Φ6
- Φ6 is an RNA virus infecting Pseudomonas syringae.
- Φ6WT infects four P. syringae varieties.
- Φ6broad, with a P3 gene mutation, infects an extra P. syringae variety and P. pseudoalcaligenes.
- Duffy et al. (2007) cultured four Φ6broad populations on P. pseudoalcaligenes for around 150 generations.
- Φ6E1narrow, a new strain, emerged mid-experiment, losing infectivity for P. syringae but retaining it for P. pseudoalcaligenes.
- Φ6E1narrow’s P3 gene alteration resulted in increased infectivity for P. pseudoalcaligenes and inability to infect any P. syringae strain.
The case of Drosophila pseudoobscura
- Dodd worked with lab populations of D. pseudoobscura descended from a common ancestral wild stock.
- Four populations evolving on a starch-based diet and four populations evolving on a maltose-based diet were studied.
- Mating trials were conducted to measure interbreeding tendencies.
- Virgin flies from starch and maltose populations were paired for mating.
- Out of 904 matings, 602 occurred between flies from the same food-based population, indicating partial reproductive isolation.
Example of Evidence of Speciation from Natural Populations
The case of Threespine Stickleback
The case of Threespine Stickleback
Stage I: Variation in threespine sticklebacks’ gill raker length observed in Robert’s Lake, Canada.
Stage II: Distinct subpopulations with interbreeding still occurring, seen between Robert’s Lake and Robert’s Creek, Canada.
Stage III: Limited interbreeding between benthic and limnetic forms observed in Paxton Lake, Canada.
Stage IV: Irreversible reproductive isolation between distinct types in Akkeshi Bay, Japan, with rare hybridization producing sterile offspring.
Several human diseases are caused by pathogens that originated in other animals, switched hosts, and evolved into new species that infect only humans. give examples
- diphtheria from a disease of domesticated herbivores
- measles from a disease of cattle
- smallpox from a virus of rodents or camels
generally refers to evolution above the species level. It encompasses the grandest trends and transformations in evolution, such as the origin of mammals and the radiation of flowering plants.
Macroevolution
are generally what we see when we look at the large-scale history of life.
Macroevolutionary patterns
Evidence of macroevolution
- Fossil Record – Transitional Forms
- A Living Transitional Form
A __ is any trace of an organism that lived in the past. The worldwide collection of it is called the __.
- fossil
- fossil record
__ published a list of 23 species known only from fossils to challenge the hypothesis that unusual forms in the fossil record would eventually be found alive. He argued that it’s impossible for these enormous creatures to still live but escape detection → __
- George Cuvier
- extinction
Fossil and living organisms in the same geographic region resemble each other but are distinct from organisms found in other areas → __
succession
If novel life-forms are descended with modification from earlier forms, then the fossil record should capture evidence of __ in progress, a __ showing a mix of traits typical of ancestral populations and novel traits seen later in descendants
- transmutations
- transitional species
The theory of descent with modification ultimately connects all organisms to a single
__.
common ancestor
Evidence of Common Ancestry
Homology
- structural homology
- molecular homology
the study of likeness.
homology
It refers to fundamental similarities underlying the obvious physical differences among species.
homology
inherited fundamental design from a common lineage/ancestor
Structural homology
