Chapter 25 Flashcards
microevolution
evolution observed at the population level
macroevolution
evolution over a very long period of time
phylogeny
evolutionary history of a group of organisms
phylogenetic tree
simplified diagram of evolutionary history of group of organism
systematics
discipline of biology that characterizes and classifies relationships among organisms and builds tree of life
taxa
named group of organisms at any level of classification system
how do phylogenetic trees answer the question of taxonomy
help describe, name, and classify species
branch
line representing a species or other taxon through time
root
most ancestral branch in tree
tip
endpoint of branch
- represents living or extinct species
outgroup
taxon that diverged before taxa you are trying to classify
node
point within tree where branch splits into two or more branches
- represents the most recent common ancestor
polytomy
node that depicts ancestral branch dividing into three or more descendant branches
sister groups
two lineages that are each other’s closest relatives
- two descendants that split from same node and are each other’s closest relative
what does the number of nodes depends on
number of taxa that are included in a tree
trait
any heritable genetic, morphological, physiological, developmental, or behavioral characteristic that varies among taxa
what characters are used to build a phylogenetic tree
- molecular characters (DNA)
- morphological characters
data matrix
table the enables you to score character states of each taxon
- trait is (1)present or (2)absent
ancestral trait
character that existed in an ancestor
derived trait
modified form of ancestral trait
- found in descendant
how do derived traits originate
mutation
selection
genetic drift
synapomorphy
another name for shared derived traits in multiple taxa
monophyletic group
evolutionary unit that includes an ancestral species and all of its descendants
homology
similarity due to common ancestor
- same source
homoplasy
occurred when traits evolved independently in two or more different lineages and are similar for reasons other than common ancestry
- same form
parsimony
assumes that the most likely explanation or pattern is the one that requires the fewest steps
- count number of character state changes required to produce each pattern, lowest number of these is best
evolutionary distance
more rapid evolutionary change may occur in some branches than others
- look at average frequency of character state changes between individual pairs of taxa
maximum likelihood and Bayesian analysis
- mathematical models
- popular with molecular data sets
- precise estimates of evolutionary history
what is a common cause of homoplasy
convergent evolution
convergent evolution
independent evolution of similar traits in distantly related organisms due to adaptation to similar environments
fossils
pieces of physical evidence from an organism that lived in the past
what are the different types of fossils
intact
compression
cast
permineralized
trace
intact fossil
forms when decomposition does not occur and organic remains preserved intact
compression fossil
sediments accumulate on top of organism and become cemented into rocks
permineralized fossils
organisms decompose extremely slow and dissolved minerals gradually infiltrate interior of cells and harden
cast fossil
buried organism decomposes, leaving an empty cavity in sediments that fills with dissolved minerals and hardens to form a cast
trace fossil
sedimentation and mineralization preserve indirect evidence of an organisms in the environment
how do fossils form
organism must perish in an environment where they are buried rapidly and decomposed slowly
what types of organisms are most likely to form fossils based on habitat bias
ones that live in a location where sediments are actively being deposited
what types of organisms are most likely to form fossils based on taxonomic bias
- those with hard parts of the body (bones or shell)
what kind if fossils are much more common based on temporal bias
recent fossils compared to ancient fossils
- older a fossil is, longer it has been exposed to destructive forces
what types of organisms leave fossils more often based on abundance bias
ones thar are abundant, widespread, and present on Earth for long periods of time
how is the Earth’s history divided into
segments called eons, eras, periods, and epochs
what tool do researches use to identify times on the fossil record
radiometric dating
Anthropocene
reflect dramatic physical, chemical, and biological changes humans are causing on Earth
adaptive radiation
single lineage rapidly produces many descendant species with a range of adaptative forms
what are the three parts to adaptive radiation
monophyletic group
speciated rapidly
diversified ecologically into many niches
niche
range of conditions that a species can tolerate and the range of resources that it can use
what mechanisms can trigger adaptive radiations
extrinsic (external)
intrinsic (within)
adaptative radiation of animals is called
Cambrian explosion
- rapid diversification of animal body types and lineages
fauna
collection of animal species
what are the potential causes of the Cambrian explosion
higher oxygen levels
rise of algae
evolution of predation
new niches gives rise to more new niches
new genes, new bodies of water
mass extinction
rapid extinction of a large number of diverse species around the world
what is the opposite of a mass extinction
adaptive radiation
background extinction
refers to lower, average rate of extinction observed when mass extinction is not occurring
what is “The Big Five”
five spikes denoting a large number of extinctions within a short time
difference between background and mass extinctions
- background occur when normal environmental change, emerging disease, predation pressure, or competition reduces certain populations to 0
- mass result from extraordinary, sudden, and temporary changes in environment
what are extinctions often followed by
adaptive radiations due to ecological opportunity
