Tree of Life: Evolutionary Relationships Flashcards
What is the tree of life?
the interconnection of all life on our planet
What does the tree of life serve as a metaphor for?
common descent in the evolutionary sense
What is classification?
putting things into groups (classes)
What is taxonomy?
science of naming and classifying organisms
What is phylogeny?
evolutionary history of species, or species groups, including the splitting of lineages
What is a phylogenetic tree?
hypothesis about evolutionary relationships within a set of species or groups of species
What is systematics?
science of working out relationships
What is a taxon (plural taxa)?
species or group of species
What is cladistics?
method that groups species based on features they share due to common ancestry?
How are organisms grouped in cladistics?
by common descent
What is a cladogram?
phylogenetic tree that is produced following approach of cladistics
What is a cladogram a hypothesis for?
how lineages split during evolution
What are clades (in a cladogram)?
group containing an ancestral species and ALL of its descendants
What are clades nested within?
clades
What is the main difference between a cladogram and a phylogenetic tree?
cladogram = HYPOTHESIS about actual evolutionary history of a group & branch lengths don't indicate anything but order; phylogenies = true evolutionary history & branch lengths indicate closeness of relationship
What give clues to/show common descent?
homologous characters
What are shared derived characters?
evolutionary novelty unique to a particular group;
shared by all members but NOT found in ancestors
What do shared derived characters reveal?
common descent
What are shared derived characters shared among?
all members of one group of the line but NOT found in ancestors
What types of homologous characters are there?
shared derived characters;
shared ancestral characters
From where did shared ancestral characters originate?
in an ancestor
In what organisms are shared ancestral characters found?
all descendent species AND their ancestor
Of the 2 types of homologous characters, which is not as useful in determining evolutionary relationships?
shared ancestral characters
What should shared derived characters have?
the same structure and function
In comparing fish and mammals, fish have scales and mammals have hair. What kind of character is having hair for mammals and why?
having hair = derived character for mammmals;
since only mammals have ancestors with hair
What is homology?
existence of shared ancestry between a pair of structures or genes in different species
What is homoplasy?
formation of homologous tissues;
structures look alike regardless of homology or analogy
What is analogy?
comparison of two things based generally on their structure
How many organisms are needed for homology, and what does homology indicate about them?
2+;
recent common ancestor
What do analogous structures do?
perform similar functions
What does analogy indicate about two species?
may or may not have a recent common ancestor
What does homoplasy indicate about two species?
nothing - structures look alike regardless of homology or analogy
What does it mean when homology, analogy, and homoplasy all converge (SEE VENN DIAGRAM)?
?
Distinguish between homology, homoplasy, and analogy?
homology: similarity in origin (implies common ancestor);
homoplasy: similarity in appearance but not origin;
analogy: similarity in function but not in origin
Which of analogies, homoplasy, and homologies are likely results of convergent evolution?
analogies and homoplasy
What is phylogeny?
the historical development of groups of organisms so as to depict descent from ancestors
What is the depiction of phylogeny called?
phylogenetic tree
What is the term for branches on a phylogenetic tree?
clades
What are organisms analyzed on in cladistic phylogeny and what is it used to determine?
analyzed on the basis of characteristics they share;
in order to determine their ancestor-descendent relationship
What do shorter links between groups in a phylogenetic tree indicate?
a closer relationship
How can we use morphological data to determine common ancestry?
look for similar characteristics;
use morphological data to distinguish
What are three types of molecular data we can use to determine common ancestry?
mutation rates, neutral genes, highly-conserved genes
How can mutation rates be used to determine common ancestry?
higher rate (?) = more mutations = greater distance between species
What is the problem with using mutations to determine common ancestry (and example)?
one mutation can cause a change and another can bring it back;
even though 2 mutations have happened (implying greater distance b/w species), it looks like none (implying closer relationship);
ex: black/white moths during industrial revolution
What are neutral genes?
genes that don’t do anything;
have coding sequences but are not expressed
How can neutral genes be used to determine common ancestry?
look at mutations and compare between species (?)
What are highly-conserved genes?
genes that don’t mutate - have very few changes
What are poorly-conserved genes?
genes with a lot of variation/mutations
What are highly-conserved genes useful for and why?
have rare changes;
useful to differentiate between large groups of organisms
What do branch lengths in a cladogram indicate?
order;
not time or degree of evolutionary change
What is one valid clade (give the term term)?
monophyletic
What clades are missing some descendents?
paraphyletic clades
What do species in polyphyletic clades have?
different ancestors
What does a monophyletic clade include?
a common ancestor and ALL of its descendants (i.e. a clade);
“one cut” off the tree of life
What does a paraphyletic clade include?
a common ancestor and SOME of its descendants (i.e. a clade minus some groups)
What does a polyphyletic clade include?
a group composed of a number of organisms which might bear some similarities, but does not include the most recent common ancestor of all the member organisms
What are ingroups?
the various species being studied
What is an outgroup?
a species or group of species that is closely related to the ingroup, but has diverged before the ingroup
What is a sister group?
outgroup
Why do systematists compare ingroup species with the outgroup?
to differentiate between shared derived and shared ancestral characteristics
What are the steps to constructing a cladogram?
- examine taxa and note shared derived character
- prepare character matrix
- make cladogram that is consisten with character matrix
What are the two rules for choosing the best tree?
maximum parsimony and maximum likelihood
What does maximum parsimony mean in terms of choosing the best tree and why is it a rule?
choose the tree that requires the FEWEST evolutionary events;
because it’s the most likely tree
What does maximum likelihood mean in terms of choosing the best tree?
choose the tree that reflects the MOST LIKELY sequence of evolutionary events
What does the maximum likelihood rule of choosing the best tree use?
rules about how DNA sequences tend to change over time
What can DNA similarity be used for?
tod etermine the relative amount of genetic change
What can the fossil record be used for?
to determine approximate time that lineages split
What do molecular clocks do and what do they use to do it?
estimate the absolute time of evolutionary change;
use constant rates of evolution in some genes to do this
What are the three domains of life?
Eukarya, Archaea, Bacteria
What are the characteristics of rRNA genes?
shared by all life;
highly conserved
What is the order of the following events?
A) symbiosis of mitochondrial ancestor and eukaryote ancestor
B) symbiosis of bacterium & archaean
C) symbiosis of chloroplast ancestor with ancestor of green plants?
B, A, C
KNOW THE DEFINITION OF PHYLOGENY AND CLADISTICS
(learning outcome)
DESCRIBE DERIVED CHARACTERS
(learning outcome)
EXPLAIN HOMOLOGY, ANALOGY, AND HOMOPLASY
(learning outcome)
KNOW HOW TO CONSTRUCT PHYLOGENETIC TREES
(learning outcome)
DESCRIBE THE DIFFERENCE BETWEEN MONOPHYLETIC, PARAPHYLETIC, AND POLYPHYLETIC
(learning outcome)
EXPLAIN THE UNIVERSAL TREE OF LIFE
(learning outcome)
