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Terms in this set (76)
Process by which populations become genetically isolated and then diverge into two or more species
A group of individuals that belong to the same species and live in the same area
Darwin on Macroevolution
-believed all life evolved from a common ancestor
-small changes in inherited traits accumulated over time to result in the origin of new species
Evolutionary changes over deep geological time that lead to new species or groups of species
Biological Species concept
Species do not breed with each other (interbreed)
Challenges with Biological Species Concept
-Asexual Species (do not reproduce sexually)
-Extinct Species (How do you know if extinct species interbred?)
-Geographically Isolated (
-Occasional interbredding (two birds that look and sound different)
General Lineage Concept
A species is a population of an evolving lineage (ancestors and descendants), with differences in morphology, DNA sequences, ecology, reproductive isolation
-feeds on birds
Develop a concept map merging what you know about microevolution (use your Lab 2 assignment as a starting point) and speciation. What role do the different evolutionary mechanisms have with regard to promoting speciation or limiting speciation? Are some mechanisms more important in speciation than others? Which mechanism is unlikely to have a role? Why?
Explain how genetic drift and natural selection contribute to speciation.
Natural selection can result in organisms that are more likely to survive and reproduce and may eventually lead to speciation. A second process called genetic drift describes random fluctuations in allele frequencies in populations, which can eventually cause a population of organisms to be genetically distinct from its original population and result in the formation of a new species.
Sympatric speciation occurs without _______________isolation.
Explain the pattern of selection that is involved in sympatric speciation.
Sexual Selection- when females prefer metes of different patterns or backgrounds which could result in a separation of one large sympatric population into smaller populations that eventually become distinct species because they selectively breed among themselves
In New Zealand, some mountain chains experience glaciation from time to time. When this happens, glaciers and wintery conditions occur on the peaks of the mountain and extend down the mountain to the point that many separate mountains become connected. When the glaciers and the winter conditions recede up the mountain, the mountaintops become isolated from one another. Over time, with repeated bouts of isolation, a group of plants known as buttercups diversified into 14 species.
-What evolutionary process occurs when the populations become join during glaciation? Explain.
-What evolutionary processes occur within each population when the glaciers recede? Explain. -After repeated cycles of glaciation, why doesn't interbreeding occur?
Explain how natural selection in two allopatric populations can lead to speciation
Over time, the populations may become genetically different in response to the natural selection imposed by their different environments. If the populations are relatively small, they may experience a founder effect: the populations may have contained different allelic frequencies when they were separated. Selection and genetic drift will act differently on these two different genetic backgrounds, creating genetic differences between the two new species.
Would you expect two populations that recently diverged into species to have more or fewer homologous traits than two species that diverged a long time ago? Explain. Use your textbook to help you understand homologous traits.
What are reproductive isolating mechanisms?
mechanisms that prevent interbreeding between species
What is the difference between pre- and post-zygotic mechanisms?
prezygotic mechanisms prevent the formation of a zygote
postzygotic mechanisms block the development of a viable and fertile individual after fertilization takes place
Males and females of two species mate, but the sperm from one species is not able to fertilize eggs from the other. What kind of RIM is operating?
If two closely related species overlapped in where they lived (their distribution) but never bred together, what RIMs might be operating? How would you distinguish between the RIMs?
-Temporal- different mating seasons
-Behavioral- two species may not mate because they have different behaviors such as songs
Concept map ideas related to speciation and RIM and include evolutionary processes that promote and constrain divergence.•
How does systematics use taxonomy and phylogenies to make sense of biodiversity and evolution?
Discuss the concept of a phylogeny and explain in detail how phylogenetic trees are constructed. See Section 26.3o
-e.g. What is a shared derived character?
-How do you identify a shared derived trait in a phylogenetic tree? An ancestral trait?
-What is parsimony?
-identify the parts of a phylogenetic tree; e.g. what is a node versus a branch point? What information is conveyed by each?
Compare and contrast anagenesis and cladogenesis. How could you identify each on a phylogenetic tree?
Anagenesis- single species evolves into a different species
Cladogenesis- splitting or diverging of one species into two or more species
-allopatric speciation is the most prevalent way for this to occur
What constitutes a monophyletic group? Paraphyletic? and Polyphyletic? If the evolutionary history of a group is very well understood, which of these groupings will be illustrated in that group's phylogeny?
What types of traits are most informative in constructing phylogenies? Explain.
True or False. Shared ancestral traits are very informative when constructing evolutionary trees. (Explain!
A phylogenetic tree includes five evolutionary changes in its construction, whereas a second tree includes seven. Which one should be select as the correct hypothesis? On what principle do we base this decision?
the first based on the principle of parsimony
When and how did life originate? What four stages are hypothesized to have occurred during the origin of life? What were the first organisms? Questions are based on reading assignment for lecture
Explain the order with which different lineages arose over geological time. Explain why prokaryotes arose before eukaryotes, why single-celled organisms arose before multicellular ones? How does that make sense? What principle could you use to explain these patterns?
In what environment did life first emerge? What happened to permit life to emerge on land?
What impact did the emergence of cyanobacteria have on the Earth?
Has the climate and atmosphere on Earth been constant over time? What key gases have changed in the atmosphere since the formation of the Earth?
How has continental drift influenced the history of life on Earth?
Explain one outcome that followed several mass extinctions.
When did each of the five mass extinctions occur? What organisms were lost?
What percentage of Earth's history includes bacteria? Seed plants? Birds? Humans?
What is a species?
a group of populations in which individuals have the potential to interbreed and produce viable, fertile offspring.
two species most closely related to each other
- share most recent common ancestor
The key to speciation
What is reproductive isolation?
the situation where different species may live in the same area, but properties of individuals prevent them from interbreeding
Potential mates do not meet
or they do not mate if they do come in contact
members of two species may mate but no fertilization occurs
hybrids form but offspring is not viable or fertile
species occupy different habitats
species differ in timing of breeding
traits preferred by female for mate choice are different
morphological differences prevent members of different species from interbreeding
gametes may be exchanged but the gametes do not unite
fertilized egg cannot progress past an early embryo
hybrid offspring produced but it is sterile and cannot reproduce
F1 offspring are viable and fertile but successive generations become increasingly unviable
study of diversity and evolutionary history of the living world
two parts of systematics
process of describing, naming and classifying organisms
-hierarchial system of naming all living things
-top level domain
-3 broad domains : bacteria, archaea, eukarya
study of the evolutionary history of organisms
Phylogenetic tree is based on
similarities are inherited from a common ancestor
traits similar in appearance and function that exist in two or more species because they share a common ancestor
similarities inherited from common ancestry
similar due to convergent evolution aka homoplasy
-organisms may not share a recent common ancestor but experienced similar selective pressures in their environments
-this leads to independent evolution of similar traits
What traits do we want?
We want homologous traits, we have to watch for analogous ones
traits are similar but were not inherited from a common ancestor
shared ancestral trait
trait inherited from an ancestor older than the last common ancestor of the group
1 species per million species per year
-10-100 species per year
-fossil record: species have existed that we don't see currently
extinction of many species at high rate over "short" span of time
-more species die out that typical
-often environmental change is a trigger
When a single ancestral species has evolved into a wide array of descendant species that differ in their habitat, form, or behavior
-ex: 1000 species of Drosopholia in Hawaii originated from one specie of fruit fly
characteristics used to identify a species
Occurs when a population becomes isolated from other populations and evolves into one or more species
-Occurs when a small population moves to a new location that is geographically isolated and have evolved into distinct species
the splitting or diverging of one species into two or more species
-typically involves a geographic barrier such as a body of water
What is a clade?
a group of organisms that includes the common ancestor of the group and the related species that evolved after it
You are building a phylogenetic tree and want to evaluate the usefulness of certain traits for uncovering the evolutionary relationships in a group of plant species. Which of the following would be most useful?
A trait that is found in two species that share a most recent common ancestor
T orF: Populations evolve, individuals are subject to natural selection
Organisms that are not closely related to one another that display similar traits such as the flying habit of sugar gliders or flying squirrels, reflect ______, in which unrelated species evolved similar traits due to similar selection pressures in their environments
horizontal gene transfer
A process in which an organism incorporates genetic material from another organism without being the offspring of that organism
Which of the following is not a criterion to be used in constructing a cladogram?
all shared derived characters are only present in common ancestors and not at the tip of the tree
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