Changes within a population over generation (single species)
Evolutionary changes that result in different species (speciation)
Steps of evolution and species formation
Population isolated into groups -> no longer interbreed
Each acquires mutations independently, different selective environments
Genetic/behavior differences enough that no longer mate
Imagine each row= many generations passing, each dot= many individuals in populations
Splits= populations no longer interbreeding
Populations continually evolving over time
Given this info/diagram, which 2 species would share the most similar characteristics in the present?
A) Sp. B and C
What would share more similar characteristics?
More closely related species will share more similar characteristics than less closely related species because they share more evolutionary history
Based on time since divergence, is species A more closely related to species B or C?
B) Equally closely related to B and C
Species A has been separated from B & C for an equal amount of time
Same amount of time on independent evolutionary paths between A:B and A:C
Did species B or C evolve from species A?
No, species A, B, and C all evolved from a common ancestral population
Extant species cannot evolve from one another -> species evolve from common ancestors
Framework for phylogenetics
You can form hypothesis about the evolutionary relationships of species/groups of species based on shared characteristics
-more closely related species will share more characteristics than those less closely related
Different species evolved from a historic common ancestor
-time since divergence results in shorter/longer accumulation of evolutionary differences between species
Studies evolutionary history/relatedness of groups
What does phylogenetic test?
Hypotheses of evolutionary relationships between groups based on shared characteristics
More closely related species have more shared characteristics
How does time move in a phylogeny?
From the base of the tree (older) to the tips of the tree (recent)
What is the base of a phylogeny tree
Shared ancestor of all species on the tree
What are the tips of the tree branches?
Nodes of phylogeny trees?
Common ancestors -> species diverge from common ancestors
Why are species with more recent common ancestor are more closely related?
There is less time to accumulate genetic differences from each other
Which point on the tree is the most common ancestor of amphibians and sharks/rays?
Which of the following is the closest relative of amphibians?
D) two of the above are equally closely related to amphibians
Lobe-finned fish diverged much longer before amphibians
Which of the following is the closest relative of sharks and rays?
D) all of the above are equally closely related to sharks and rays
*don't count the nodes
Do these trees depict the same evolutionary relationships?
Yes, evolutionary relationships are depicted via common ancestors (nodes)
Can rotate trees along nodes
Which of the following phylogenies to the is not an accurate representation of the evolutionary relationships?
C) this suggests that humans are equally to everything but they are only close with yeast
Which of the following pairs would share the most similar characteristics based on their shared evolutionary history?
A) Lily and Fern
How to decide which organisms are more closely related to each other in order to build a tree?
Shared, derived characteristics that result from common ancestry
Similarity resulting from common ancestry
Different forms of the character
More closely related taxa will share more character states
Group with characteristics that are ancestral to the group of interest (ingroup)
If ingroup species have different character state for a character, must be a new evolutionary feature for the group
Character state found in the ancestor of the group (the outgroup will have plesiomorphic characteristics)
Derived character states found in descendants of the group; evolutionary novelties acquired after divergence from the ancestral group
Shared, derived character states that indicate homology
More closely related groups will share more synapomorphies
Plesiomorphies in this chart?
Outgroup characteristics (no)
Apomorphies in the chart?
Ingroup characteristics (yes)
Synapomorphies in the chart?
Everything except hair because only leopards have hair
Coding the ancestral vs. derived states
A common ancestor and all of its descendants
The only valid evolutionary group
Also called a clade
Why does monophyletic grouping make sense?
Defined by shared derived characteristics. You can't randomly exclude descendants
A group containing a common ancestor but NOT all of its descendants
A group characterized by 1 or more homoplasies
Homoplasy (analogous structure)
Character states appear the same in 2 taxa but not evolved from a common ancestor
Wings are adapted for flight but they are independent
Under what circumstances might an analogous structure develop?
Similar adaptations in response to similar environmental pressures
Independent evolution of the same character state in multiple, separate lineages
How many monophyletic groups does this tree have?
The simplest explanation is the best
Best tree= tree with fewest evolutionary steps
How are phylogenies hypotheses?
Testable and falsifiable
What type of character is the presence of thorns?
Homoplasy- thorns evolved independently in species B and C
Does this tree of life (with 2.3 million known species) with the common ancestor at 3.5 billion years ago show which organisms are more or less highly evolved?
No because evolution doesn't make organisms "better" or "highly evolved"
All life has the same 3.5 billion year evolutionary path because of our common ancestor
Does the tree of life provide an explanation for how the first life on Earth developed?
In other words, does it tells how Earth went from lifeless to the first organism?
No, evolution only explains how life that already existed changes over time