lab midterm Flashcards
how do we represent which organisms are alive in a phylogenic tree
dead end branched that don’t make it to the present are extinction events. further back means that species no longer exists
why are all phylogenetic trees considered a hypothesis
because we can’t go back in time to verify the exact branching pattern
what are all organisms traced back to
an organism that lived 3.7 billion years ago. this group of prokaryotes, which forms the basal tree of life is collectively referred to as LUCA (last universal common ancestor
describe the LUCA hypothesis
Some fundamental cellular components such as DNA, ribosomes, and
plasma membranes, which are still universally shared by all life forms, were present in the
LUCA. These components are so molecularly complex that it is unlikely that they would be
so similar if they evolved independently. An example of this are ribosomes, which are
comprised of 50+ proteins and RNA molecules thousands of nucleotides long.
define taxonomy
the scientific discipline concerned with naming and classifying groups of biological organisms.
organisms. Taxonomists group organisms based on
similarities in morphology and/or molecules into taxonomic categories starting with the most
inclusive category,
(domain, kingdom, phylum, …)
what is the complete taxonomy of a human?
domain: eukarya
kingdom: animalia
phylum: chordata
class: mammalia
order: primates
family: hominidae
genus: homo
species: sapiens
what is a monophyletic clade
all members of a monophyletic clade are closer relatives to each other than they
are to all organisms outside the clade. A monophyletic clade could contain a group of closely
related genera, which taxonomists would refer to as a family, or a group of distantly related
phyla, which taxonomists would refer to as a kingdom—monophyletic clades can happen at
any taxonomic rank within the tree of life.
definition of a monophyletic clade
a group that converges on a
common ancestor prior to joining other clades.
paraphyletic bs polyphyletic groups
Paraphyletic groups exclude some descendants of the last common ancestor of the group.
Polyphyletic groups exclude some descendants as well as the common ancestor of the
group (Figure 1.
define character, give an example
an anatomical, physiological or molecular feature found in an organism
characters. For instance, all members of the mammal clade have vertebral
columns and hair. Hair is unique to mammals, but the presence of a vertebral column is also
found in other clades
for mammals, are the milk-producing mammary glands ancestral or derived? explain
derived because it’s unique to mammals
describe ancestral character
fish). Vertebral columns are found in
these other clades as well as mammals because this character evolved in an early
vertebrate ancestor, long before the emergence of these later clades. For mammals, the
vertebral column is therefore an ancestral character
all mammals have a backbone, but it
is ancestral to the formation of the mammal clade itself.
describe derived character
contrast, hair evolved in an early
mammal ancestor; therefore, all mammals, and only mammals, have hair. For mammals,
hair is therefore a derived character - all mammals have hair because it was derived in an
early ancestor within the mammal clade.
for mammals, are hinged jaws ancestral or derived? explain
ancestral because it is older than the mammal
what are shared derive characters
characters shared by only some lineages within a clade. can be used to identify less inclusive clades.
clades. For example, mammals and
reptiles (including birds) share a similar reproductive structure called the amniotic egg, and
the amniotic egg is one of the shared derived characters that helps set apart the
monophyletic clade Amniota (mammals and reptiles) within the more inclusive clade
define homologous characters
Shared characteristics that can be traced back to a common ancestor (i.e. shared due to
descent) are referred to as homologous characters.
describe convergent evolution
d convergent evolution—the characters converged on a similar morphology, often
because of similar ecological pressures
define analogous characters
Shared characters that are a result of convergent
evolution and not common ancestry are referred to as analogous characters.
are analogous characters useful for constructing phylogenies? why?
no because they can be misleading, can make lineages appear more closely related than they are
What process could cause two taxa that are not closely related to look quite similar (at least
superficially) and result in a taxonomic error?
convergent evolution. (I think)
are the wings of butterflies homologous or analogous? explain
analogous
bird wings are analogous because they are not derived from a common ancestor but evolved independently to perform the same function: flight.
are the wings of butterflies and dragonflies homologous or analogous?
homologous
what is progressivism?
It is common for students to visualize evolution as progressing through a long series of
lesser organisms only to finally reach humans, which were thought to be the pinnacle of
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evolution. This view, known as progressivism, was historically quite common but is now
seen as being thoroughly obsolete
why is progressivism incorrect?
because evolution isn’t linear
Is it more accurate to say “humans descended from chimps” or “humans and chimps shared
a common ancestor”? Explain
humans and chimps share a common ancestor because chimps are not extinct and it is more scientifically accurate
are all eukaryotes equally related?
Of course, each domain is incredibly diverse, containing
(in the case of Eukarya), millions of species, all of which are comprised of cells containing
nuclei and other membrane bound organelles. This does not mean that all eukaryotes are
equally related, however; some species within Eukarya share a common ancestor recently
(millions of years ago), whereas some eukaryotes would be much more distantly related.
which one would be considered the most parsimonious tree in different phylogenetic trees
most parsimonious tree would be the one with the least number of
mutations and is thus the most likely tree or best explanation.
how does DNA store information
in the nucleotide sequence
what is a non-coding region
region of DNA is a part that does not directly code for proteins.
What is a genome? How big is your genome? How much of it is non-coding?
the entire set of DNA instructions found in a cell
23 Paris of chromosomes
about 99%
define homologous genes
genes that exist in taxa because they were inherited from a common ancestor
—genes are passed down the tree of life just as morphology is passed
down the tree; in fact, morphology is passed down because genes are. Also, you would
need to align the homologous sequences to allow direct comparisons
define conserved gene sequences. why are they so important
DNA sequences that move through evolutionary time relatively
unchanged are referred to as conserved gene sequences, and conserved sequences are
almost always linked to a critical function.
do non-doing regions diverge quickly after a speciation event
yes
what are the different shapes that bacteria can be?
Round bacteria are called cocci (coccus = singular), rod-shaped
bacteria are bacilli (bacillus = singular). Other shapes include spirilla (spirillum =
singular), which are flexible, spiral shaped cells
describe cyanobacteria
Cyanobacteria are unusual in a number of ways. Not only are they much larger than
traditional bacteria, they are all photosynthetic. Most of them grow in multicellular filaments
(a chain of cells). Cells in these filaments can be round or rectangular in shape, but are not
called cocci or bacilli.
gram positive vs gram negative bacteria
Cells that stain purple are called gram-positive bacteria and cells that stain pink are called
gram-negative bacteria. The Gram reaction is based on structural differences in the outer
covering of the cell. Most bacteria have a layer of peptidoglycan in the cell wall, outside the
plasma membrane. Peptidoglycan protects the cell from lysis in a
hypotonic environment. Gram-positive bacteria have a very thick layer of peptidoglycan.
Gram-negative bacteria have a more complex outer coating – a thin layer of peptidoglycan
is sandwiched between an inner and outer membrane.
dinoflagellates. know what they look like
Motile photosynthetic organisms that are a very important component of marine ecosystems.
Over half of the known species are photosynthetic but many are mixotrophs
Some dinoflagellates, under certain conditions, can reproduce very rapidly. This uncontrolled
reproduction can result in what is known as a “Red Tide”. Some species can produce a
poison that paralyzes the nervous system of animals.
what do female cones look like vs male cones
label plant
lable eudicot root
