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BIO Exam 2 - Stack 1

History of Life on Earth; Phylogeny

Key events in life's history include the origin of ___ and ___ organisms and the colonization of ___. - single-celled - multi-celled - land
___ show evolutionary relationships. Phylogenies
Phylogenies are inferred from ___ and ___ data. - morphological (form and structure of organisms) - molecular (DNA)
The first sing-celled organisms appeared on Earth approximately ___ billion years ago. About 3 billion years elapsed before the ___ occurred (~500 million years ago). - 3.5 - colonization of land
phylogeny the evolutionary history of a species or group of species
To construct phylogenies, biologists use systematics. What is that? a discipline focused on classifying organisms and determining their evolutionary relationships
The study of ___ has helped geologists establish a geologic record of Earth's history. fossils
What were the first single-celled organisms, and where does the earliest evidence of their origin come from? - prokaryotes (heterotrophic, anaerobic) - stromatolites
What are stromatolites? layered rocks that form when certain prokaryotes bind thin films of sediment together
For how long were prokaryotes the only life forms on Earth? from 3.5 to 2.1 billion years ago, so about 1.4 billion years
What's the relationship between the evolution of photosynthesis and the appearance of atmospheric oxygen? - photosynthesis evolved (light energy from the sun used to synthesize sugars from CO2; released oxygen as a waste product) - carried out by autotrophs - oceans became saturated with oxygen, so it started releasing into the atmosphere
What were cyanobacteria and what was their role? - the first oxygen releasing, photosynthetic bacteria (autotrophic, aerobic) - saturated the ocean with oxygen, which then led to oxygen being released into the atmosphere
autotroph an organism that obtains organic food molecules without eating other organisms or substances derived from other organisms; autotrophs use energy from the sun or from oxidation of inorganic substances to make organic molecules from inorganic ones
heterotroph an organism that obtains organic food molecules by eating other organisms or substances derived from them
anaerobic organism - an organism that does not require oxygen for growth - may react negatively or even die if oxygen is present - may be unicellular (e.g. protozoans, bacteria) or multicellular
aerobic organism - an organism that can survive and grow in an oxygenated environment - some need oxygen, others can go without if necessary
What did this increase in atmospheric oxygen mean for the evolution of prokaryotic organisms? - (oxygen can attack chemical bonds, inhibit enzymes, and damage cells) - rising O2 meant that many prokaryotic groups died out - Some survived in anaerobic environments, others w/ adaptations (cellular respiration: glucose+O2+ADP+phos. → CO2+H2O+ATP)
The first single-celled eukaryotes appeared about ___ years ago. 2.1 billion
What are the defining features of eukaryotic cells? - nuclear envelope (w/ linear DNA) - mitochondria and other internal structures - cytoskeleton
What is the endosymbiont theory of how eukaryotic features evolved from prokaryotic cells? mitochondria and plastids (general term for chloroplasts and related organelles) were formerly small prokaryotes that began living within larger (host) cells
What is the hypothesis of serial endosymbiosis? mitochondria evolved before plastids through a sequence of endosymbiotic events
What is the evidence for the endosymbiotic origin of mitochondria and plastids? - inner membranes of both are homologous to the plasma membranes of living prokaryotes - both replicate similarly to certain prokaryotes - each contain a circular DNA molecule not assoc. w/ large amounts of proteins - similar cellular machinery
What did the evolution of multicellularity make possible? greater morphological diversity (a single cell can't is what it is)
Why were multicellular eukaryotes limited in size and diversity until the late Proterozoic (ca. 570 MYA)? severe ice ages
What is the “snowball Earth” hypothesis? suggests that most life would have been confined to areas near deep-sea vents and hot springs or to equatorial regions of the ocean that lacked ice cover
What was the Cambrian explosion (535 to 525 MYA)? - a relatively brief time in geologic history when many present day phyla of animals first appeared in the fossil record - emergence of the first large, hard-bodied animals - major lineages of all animals were established
There is fossil evidence that cyanobacteria and other photosynthetic prokaryotes coated damp territorial surfaces well over a billion years ago. However, larger forms of life did not begin to colonize land until about ___ years ago. 500 million
The gradual evolutionary venture out of aquatic environments was associated with adaptions that ___ and ___. - made it possible to reproduce on land - helped prevent dehydration
What sorts of adaptations were associated with the colonization of land by plants? - vascular systems (for transporting materials internally) - leaves with a waxy coating
(Colonization of land) What was the deal with fungi? - roots of most plants were associated with fungi - fungi helped plants absorb water and nutrients from the soil - in turn, the fungi would obtain their organic nutrients from the plants
(Colonization of land) What was the deal with arthropods such as insects and spiders? - the first animals to colonize land - had hard outer coverings to retain moisture
(Colonization of land) What was the deal with tetrapods? - evolved from a group of lobe-finned fishes - humans arrived late in the scene
When did humans show up? 195,000 years ago (so not long ago at all in the grand scheme of things)
taxonomy a scientific discipline concerned with naming and classifying the diverse forms of life
systematics - a discipline used by biologists to construct phylogenies - focused on classifying organisms and determining their evolutionary relationships - use info from fossils, genes, molecules, etc.
Phylogenies show ___ relationships. evolutionary
binomial nomenclature a two-part, latinized format for naming a species, consisting of the genus and specific epithet (which is unique for each species within the genus)
What is the first part of a binomial? - the genus - (what different species belong to)
What is the second part of a binomial? - the specific epithet - (unique to each species) - (usually a description of the species)
What are the advantages of using Latin or Latinized names? - avoids ambiguity when communicating about research - latin was the scientific language - standardization
What is the order of Linnaean classification? (Remember the mnemonic!) - domain, kingdom, phylum, class, order, family, genus, species - (Dirty King Phillip Came Over From Great Spain)
taxon - a named taxonomic unit at ANY given level of classification - (ex. Panthera pardus...Panthera is the taxon at the genus level, pardus at the species...mammalia would be the taxon at the class level)
Why do we classify organisms at all? - recognition - it's a way to structure our human view of the world
How was this type of hierarchical classification done classically? people grouped species based on their morphological characters (so, what they looked like)
Classifying organisms based on their morphological characters may reflect relatedness, but does it necessarily reflect evolutionary history? no, its just has nothing to do with history
What do phylogenetic trees purport to show? - the evolutionary history of a group of organisms - shows common ancestry - the branching pattern of these trees often match how taxonomists have classified groups of organisms nested within more inclusive groups
A phylogenetic tree represents a hypothesis about evolutionary relationships. Why would we call this a hypothesis? - because a lot of common ancestors are extinct - DNA analyzed on things existing today are used to hypothesize with phylogenetic trees - things that have been separated for less time have less genetic differences...greater time, more differences
branch point where lineages diverge (on a phylogenetic tree)
polytomy an unresolved pattern of divergence (on a phylogenetic tree)
sister taxa - groups of organisms that share an immediate common ancestor (branch point) - located at the tip ends of branches on a phylogenetic tree
basal taxon - a lineage that diverges early in the history of a group - originates near the common ancestor - (basal...base...=thing that split off first)
What does it mean when a phylogenetic tree is rooted? a branch point within the tree (often drawn furthest to the left or bottom) is included that represents the most recent common ancestor of all taxa in the tree
Phylogenetic trees are intended to show patterns of ___. descent
Although closely related organisms often resemble one another due to their common ancestry, they may not if ___ or ___. - their lineages have evolved at different rates - they faced very different environmental conditions
On a phylogenetic tree, crocodiles, lizards/snakes, and birds share a common ancestor. However, crocodiles and birds share an additional branching point. What does this mean? crocodiles are more closely related to birds than to snakes and lizards (since the crocs and birds share a more recent common ancestor)
The sequence of branching in a tree does not necessarily indicate the actual (absolute) ___ of the particular taxa. ages
Unless given specific information about what the branch lengths in a phylogenetic tree mean, we should interpret the diagram solely in terms of ___. patterns of descent
Two taxa on a phylogenetic tree are next to each other. Does this mean that one of them evolved from the other? no (remember that branching points can be flipped, so that will change the order of taxa)
A person collects plants for pharmaceutical testing looking for natural products with anti-cancer activity. When the National Cancer Institute gets a “hit” on an extract from a particular plant, how do you think that person proceeds from there? - they grab that sample, find its sister taxa, and test those for anti-cancer activity too - one of them might work better than the first sample did
Phylogenies are inferred from morphological and molecular data. These analyses can reflect evolutionary relationships only if the characters used result from common ancestry. What does that mean? it is important to focus on features that result from common ancestry because only those reflect evolutionary relationships
What does it mean when we say that the limbs of humans, cats, whales, and bats are morphologically homologous? - they may have different functions (flying vs. swimming, etc.), but the underlying anatomy is similar - this is due to a common ancestor with the same bone structure
If you were to look at genes sequences and other DNA sequences from morphologically homologous organisms, what would you find? that their DNA would be more similar compared to other organisms (ex. mammals vs. reptiles/insects/etc.)
What do you think we would find if we were to compare DNA sequences from bats to DNA sequences from birds? - there would be a larger difference between bats and birds than between bats and humans/cats/whales - both are tetrapods and their wings are homologous as limbs, but bats are mammals, birds are not; so, they are not as closely related
As swimming organs, what’s the deal with whale fins and shark fins? - the swimming organs have the same function, but they evolved independently (not from a common ancestor) - the swimming limbs are analogous
As swimming organs, whale fins and shark fins are _____________ and the result of ________________. - analogous structures - convergent evolution
As flying organs, bat wings, bird wings, and butterfly wings are _____________ and the result of ________________. - analogous structures - convergent evolution
analogous - having characteristics that are similar because of convergent evolution, not homology - they evolved independently
convergent evolution the evolution of similar features in independent evolutionary lineages
homology phenotypic and genetic similarities due to common ancestry
Bat wings and bird wings are ___ as limbs, but they are ___ as flying organs. - homologous - analogous
homoplasies analogous structures that arose independently; same as analogy
When are morphological structures more likely to be homologous? - when the common ancestor is more recent - (the more elements that are similar in two complex structures, the more likely it is that they evolved from a common ancestor)
When are genes more likely to be homologous? - when the common ancestor is more recent - (if genes in two organisms share many portions of their nucleotide sequences, it is likely that the genes are homologous)
nucleotide sequence alignment - a way of arranging the sequences of DNA/RNA/protein to identify regions of similarity that may be a consequence of functional, structural, or evolutionary relationships between the sequences - done with a computer; gaps are added so sequences align
What would you call two DNA sequences (from two diff. organisms not closely related) that coincidentally share 25% of their bases? a molecular homoplasy
Created by: jessica.gvc



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