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Flashcards in Chapter 4 Deck (24):

the fossil record

based on the sequence of fosiils found within rock strata and the ages of rocks and fossil scientists have established a geological record


the history of earth is divided into three eons

1. archean
2. proterozoic
3. phanerozoic (most recent)


the phanerozoic is the most recent eon and it is divided into three eras

1. palezoic
2. mesozoic
3. cenozoic
-eras are further subdivded into periods
-the boundaries of eras are marked by mass extinctions
-lesser extinctions often mark the boundaries of periods


paleozoic era

virtually all life was aquatic


mezozoic era

-an abundance of reptile fossil were found here as a well as being the era of the dinosaur
the beginning of mammals and flowering plants also occurred in this era
-at the end of this era all but the form of dinosaurs were extinct


cenozoic era

was an explosive evolution of mammals, birds, and angiosperm plants
-because this era is the most recent occurring approximately 65 million years ago, more is known about it and the periods are further sun-divided into epochs


the continental drift

german meterologist Wegner proposed that the earth began as one great mass which broke up into continents that then drifted into their current positions
-continental drift is the slow, continuous movement of earths crustal on the hot mantle
-important geological processes occur at plate boundaries


sliding plates

are earthquakes zones


colliding plates

forming mountains



means all the land and is the term assigned to the superconinent
-250 million years ago plate movements brought all of the previously separated land masses together to form pangea
-this brought species that has been evolving in isolation back together to compete with one another
-it also lowered the sea level, draining shallow coastal seas probably killing marine organisms that inhibited these environments
-terrestrial environments were also cold and dry
-the formation of pangea reshaped biological diversity and caused a number of extinctions, but provided lots of opportunity for those organisms that survived the changes


the break up of pangea

the breakup of pangea led to the modern arrangement of continents
-this breakup occurred 180 million years ago
-the gradual collision of India and Eurasia resulted in the formation of the Himalaya mountains
-Australia marsupials became isolated when the continents separated and placental mammals arose on other continents


the breakup of pangea- lung fishes

ancient vertebrates called lung fishes have unique pattern of distribution that can be explained by the breakup of pangea
-fossilized lung fishes have been found on all continents except Antarctica therefore the lungfishes must have evolved when pangea was intact


mass extinctions

reasons that extinctions may occur include
-destruction of habitat
-unfavourable climatic changes
-changes in the biological community
intro of predators
intro of compeitiors
-there have been 5 mass extinctions over the past 500 million years
each of these mass extinctions led to 50% or more of the earths species becoming extinct
-whatever the reason for them mass extinctions profoundly affect biological diversity
-removes species which are thriving due to highly advantageous features


anthropogenic activity

activities mediated by humans


adaptive radiation and mass extinction

dramatic adaptive radiation occurs following mass extinctions
various ecological niches that have been vacated by extinction are filled by surviving organisms



is the history of a species or a group of species


homologous structures

may look and function differently in different species but they exhibit fundamental similarities because they evolved from the same structure in a common ancestor
-comes from divergent evolution
-organisms which share similar morphologies are likely to be closely related
-not all likenesses are inherited from a common ancestor


convergent evolution

species from different evolutionary branches may come to resemble one another if they live in similar environments and natural selection acts to favor the same adaptions
-body structures and sometimes whole organisms may come to resemble one another
-this similarity due to convergent evolution is called analogy structures


convergent and divergent

convergent & analogous structures - different to similar
divergent & homologous structures - similar to different



this biological discipline focuses on classifying organisms and determining their evolutionary relationships
taxonomists assign a two-part or binomial name to organisms
-the first part is the genus to which the species belongs
-the second part it the species itself
-both are italicized and the genus must be capitalized the species must not be capitalized
-strain (not capitalized or underlined)


grouping of species

genera (plural of genus) are grouped into progressively larger categories
the major groups of classification from the most inclusive (least degree of relatedness) to least inclusive (greatest degree of relatedness)
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clade: a group of species that includes its ancestral species and all of its descendants
-an inclusive group of ancestors and descendants is referred to as a monophyletic
-shared dervived characters: these are new traits which develop in an organism and is passed on to its descendants
-shared ancestral characters: these are the original traits present in the ancestral groups
shared derived traits distinguished clades and the branch points in the tree of life
cladograms compare an ingroup and an outgroup:
ingroup: this is the group of taxa that is actually being analyzed
outgroup: this is a species or a group of species that is known to have diverged before the linage that contains the groups to be studied


molecular systematic

molecular systematics is the comparing of nucleic acids or other molecules to look for relatedness
-the more recently that two species have evolved from a common ancestor the more similar their DNA sequences should be
-similarily the longer they have been on separate evolutionary paths the more distinct their DNA is expected to be
-DNA encodes ribosomal RNA (rRNA) is useful to investigate relationships that diverged hundereds of millions of years ago
-this DNA changes very slowly
-DNA of the mitocondria (mtDNA) reveals more recent evolutionary events
-this DNA evolves rapidly


organizing the domains of life

in the late 1960's scientists were using 5 kingdoms system:
-monera: prokaryotes
-protista: diverse mostly unicellular eukaryotes
molecular studies highlighted serious flaws in this 5 kingdom system
-today the three kingdom system is used
-molecular evidence indicates that the two prokaryote groups: bacteria and archeae diverged very early on
it also reveals that archea are more closely related to eukarotes than are bacteria