Lecture 24a Flashcards
What is Emergent Complexity (or Emergence)?
A process whereby larger entities, patterns, and regularities arise through interactions among smaller or simpler entities that themselves do not exhibit such properties.
Why did the emergent complexity of snowflakes occur?
Because it is thermodynamically favored over disorder.
In terms of Emergent Complexity, how can life on Earth be thought of as?
The life currently on Earth can be thought of as emergent complexity that has developed over 4.3 billion years.
Emergent Complexity is continuing, both at the ______________ level and on _____________ levels. For example, humans are getting increasingly integrated/organized.
organismal, broader
Who was the first to theorize that existing species evolved from pre-existing ones?
Charles Darwin
What were the 3 important influences that helped Darwin develop his theory?
1) Theories of Geology
2) Darwin’s own experimental observations
3) Thomas Malthus’ “Essay on the Principle of Population”
How did Theories of Geology influence Darwin’s theory?
The Earth is very old and slow geological processes change the Earth’s characteristics.
How did Darwin’s own experimental observations influence his theory?
He made a voyage aboard the HMS Beagle where he carefully examined many different species. He noted similarities, but also differences that enabled various species to adapt to different environmental conditions.
How did Thomas Malthus’ “Essay on the Principle of Population” influence Darwin’s theory?
In this essay published in 1798, Malthus asserted that resources cannot keep up with the reproductive potential of humans. He argued that famine, war, and disease will limit population growth, especially among the poor.
When had Darwin largely formulated his theory of evolution by? When did he begin to write his book?
By the mid-1840s.
In 1856, he began to write a long book to explain his ideas.
Who was Alfred Wallace and what did he do?
A naturalist working in the East Indies who independently proposed the same ideas as Darwin concerning evolution.
In 1858, two papers, one by ____________ and one by _____________, were published in the Proceedings of the Linnaean Society of London.
Darwin, Wallace
In 1859, what did Darwin publish and what did it talk about?
His book “On the Origin of Species by Means of Natural Selection”
In it, Darwin expounded his ideas in greater detail and with experimental support.
Evolution needs __________ ____________, which is a consistent feature of most natural populations.
Genetic Variation
What did Darwin assume in regard to Genetic Variation? What did he not know?
Darwin assumed that some phenotypic variation is passed from parent to offspring.
However, he did not know the genetic basis for inheritance of traits.
Genetic Variation can involve what 3 things?
1) Allelic differences in genes
2) Changes in chromosome structure
3) Alterations in chromosome number
What is a Species?
A group of individuals whose members can interbreed to produce viable, fertile offspring.
The members of one species cannot successfully interbreed with members of other species.
T/F: Cheetah and lion are the same species.
False! While a cheetah and lion can mate, the offspring they produce would be sterile, thus, they are not part of the same species.
A single species may exist in….?
A single species may exist in 2 or more distinct populations that are evolving slowly into different species.
What is an Ecological Niche?
Describes how an organism or population responds to the available resources, competitors, and challenges (predators, pathogens, etc.), and how it in turn alters those same factors.
How an organism or population responds to and interacts with its environment.
T/F: A species tends to occupy more than a few ecological niches.
False! A species tends to occupy one or a few ecological niches.
Species are ________________ isolated from other species. Thus, they cannot successfully interbreed with other species.
reproductively
The reproductive isolation of a species can be achieved by what 2 mechanisms?
Prezygotic and Postzygotic mechanisms.
What are Prezygotic mechanisms?
Something prevents the formation of a zygote (fertilized egg).
What are Postzygotic mechanisms?
Something prevents the development of a viable or fertile offspring after fertilization has taken place.
What is an example of a Postzygotic mechanism?
Lions and Tigers can mate with each other to produce healthy offspring that are sterile; consequently, they are different species.
What is Speciation?
The formation of new species via evolution.
By examining fossil records, evolutionary biologists have found 2 different patterns of speciation. Name them.
Anagenesis & Cladogenesis
What is Anagenesis?
A single species is transformed into a different species over the course of many generations.
If newer offspring time-traveled back in time, they could not produce fertile offspring with their ancestors.
What is Cladogenesis?
A single species goes into 2 different ecological niches or geographically-different locations and gets divided into 2 or more species that lose the ability to make fertile offspring.
What is the most common form of speciation?
Cladogenesis
“New species better adapted to survive in original or new environment compared to older species.”
What type of Speciation is this?
Anagenesis
“Each new species develops characteristics that prevent it from interbreeding with the original one.”
What type of Speciation is this?
Cladogenesis
What is Allopatric Speciation?
A species gets split into 2 populations by geographic barriers (river, volcano, rising sea levels, etc.) and the populations diverge from each other.
What is Parapatric Speciation?
Occurs when members of a species are not completely geographically isolated.
What are 2 different mechanisms for how Parapatric Speciation occurs?
1) Partial separation by geological processes
2) Sedentary species
Describe partial separation by geological processes.
A mountain range may divide a species into 2 populations. Breaks in the range allow for infrequent interbreeding.
Basically, the mountain could be crossed but is rarely crossed.
Describe Sedentary Species.
Certain organisms are so sedentary (don’t move a lot) that 100 to 1,000 meters may be sufficient to limit interbreeding between groups. Plants, terrestrial snails, grasshoppers, and lizards may speciate in this manner.
What is Sympatric Speciation?
Occurs when a species splits into 2 despite occupying the same habitat.
2 groups of animals may start to fall into different ecological niches, and their physical characters then diverge due to differing selection.
What is an example of Sympatric Speciation?
In plants, a common way for sympatric speciation to occur is the formation of polyploids. Polyploidy is so frequent in plants that it is a major form of speciation.
T/F: Polyploidy is just as common in animals as it is in plants.
False! By comparison, polyploidy is far less common in animals.
“The habitat ranges of wolves and coyotes overlaps substantially, and they can still interbreed to produce viable fertile offspring. However, they pursue somewhat different game and interbreed only when their own kind are not available”
What type of speciation is this?
Sympatric speciation
T/F: Speciation can be fast or slow. Overall, the fossil record and known genetic phenomena tend to support the idea that the tempo of evolution can indeed be quite variable.
True!
What are 3 ways in which Speciation can occur by?
Gradualism, Punctuated Equilibrium, and a combination of Gradualism and Punctuated Equilibrium
What is Gradualism?
Each new species evolves continuously over long spans of time.
What is Punctuated Equilibrium?
Species exist relatively unchanged for many generations. These long periods of equilibrium with the environment are punctuated by short periods where evolution occurs at a rapid rate due to stress.
What does Speciation usually look like?
A combination of gradualism and punctuated equilibrium.
What is Phylogeny?
The sequence of events involved in the evolutionary development of a species or group of species.
What is a Phylogenetic Tree?
A diagram that describes the phylogeny of a species.
For phylogenetic trees these days, increasingly, _____________ and ____________ __________ _______________ data is being used.
nucleotide and amino acid sequence
In Phylogenetic Trees, what do nodes or branch points illustrate?
Illustrate when a species diverges into 2 or more species (Cladogenesis).
In Phylogenetic Trees, what do the tips of the branches represent?
Species that became extinct (no survivors) or modern species.
T/F: A Phylogenetic tree of all life on Earth compared the sequences found in all living organisms and it shows relatedness between all life on the planet.
True!
What are the 3 main evolutionary branches?
Bacteria, Archaea, Eukaryotes
What is Horizontal Gene Transfer?
Genes get moved from one species to another.
This was widespread during early stages of evolution.
T/F: Horizontal gene transfer is common in eukaryotes and uncommon in prokaryotes.
False! It is prevalent in prokaryotes and far less common among eukaryotic species (multicellularity and sexual reproduction may be barriers).
What 2 things in the cell did bacterium give rise to through Horizontal Gene Transfer?
Chloroplasts and Mitochondria
What 4 groups can the Eukaryotic branch be subdivided into?
Protists, fungi, animals, and plants
Molecular genetics had led to the eukaryotic branch being broken into a number of __________________.
Plants are with _________.
Animals and fungi are in the ___________ supergroup.
supergroups
algae
same
What are Molecular Clocks?
Change in sequence of neutral (no consequence if DNA is changed) DNA over time is thought to be relatively constant.
Helpful in determining how closely-related 2 species are.
Why is the Mitochondrial DNA sequence change a popular molecular clock?
Because it is not subject to meiotic recombination
Are we able to obtain DNA sequence information from past species?
Yes, it is occasionally possible using tissue samples from museum specimens
In 1984, researchers first succeeded in determining DNA sequences from _____________ species. What was the organism?
extinct
The organism was quagga (Equus quagga), which is a zebralike species that became extinct in 1883.
What did the analysis of the quagga organism do?
This pioneering study opened up the field of ancient DNA analysis, also known as Molecular Paleontology.
