Tree of Life: Evolutionary Relationships Flashcards by Nicole Easton

What is the tree of life?

the interconnection of all life on our planet

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What does the tree of life serve as a metaphor for?

common descent in the evolutionary sense

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What is classification?

putting things into groups (classes)

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What is taxonomy?

science of naming and classifying organisms

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What is phylogeny?

evolutionary history of species, or species groups, including the splitting of lineages

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What is a phylogenetic tree?

hypothesis about evolutionary relationships within a set of species or groups of species

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What is systematics?

science of working out relationships

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What is a taxon (plural taxa)?

species or group of species

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What is cladistics?

method that groups species based on features they share due to common ancestry?

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How are organisms grouped in cladistics?

by common descent

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What is a cladogram?

phylogenetic tree that is produced following approach of cladistics

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What is a cladogram a hypothesis for?

how lineages split during evolution

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What are clades (in a cladogram)?

group containing an ancestral species and ALL of its descendants

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What are clades nested within?

clades

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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

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What give clues to/show common descent?

homologous characters

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What are shared derived characters?

evolutionary novelty unique to a particular group;

shared by all members but NOT found in ancestors

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What do shared derived characters reveal?

common descent

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What are shared derived characters shared among?

all members of one group of the line but NOT found in ancestors

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What types of homologous characters are there?

shared derived characters;

shared ancestral characters

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From where did shared ancestral characters originate?

in an ancestor

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In what organisms are shared ancestral characters found?

all descendent species AND their ancestor

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Of the 2 types of homologous characters, which is not as useful in determining evolutionary relationships?

shared ancestral characters

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What should shared derived characters have?

the same structure and function

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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?

1. examine taxa and note shared derived character 2. prepare character matrix 3. 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

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DESCRIBE DERIVED CHARACTERS

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EXPLAIN HOMOLOGY, ANALOGY, AND HOMOPLASY

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KNOW HOW TO CONSTRUCT PHYLOGENETIC TREES

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DESCRIBE THE DIFFERENCE BETWEEN MONOPHYLETIC, PARAPHYLETIC, AND POLYPHYLETIC

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EXPLAIN THE UNIVERSAL TREE OF LIFE

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