Practice Question for Mid-term I
Which of the following is not a characteristic of prokaryotes?
a) Spend most of their time in the diploid state
b) a nuclear region containing genetic material
c) very small cells with permeable membranes well adapted for feeding on
dissolved material
d) possess the broadest range of biochemical capabilities in the living world
e) can disperse either through resistant spores or as highly motile “swarmers”
In a Winogradsky column methane would be expected to be most abundant at
a) the bottom, farthest from the air, where hydrogen would be the most
abundant
b) in the middle of the column where traces of O2, will be present
c) in the lower portion of the column, where no O2 is present but other electron
acceptors (nitrate and sulphate) are
d) methane would not likely be found in such a column
e) methane would be present throughout the column
In a Winogradsky column where would you most likely find sulfate reducing bacteria
a) the bottom where conditions are most reducing and sulfide is the most abundant
b) in the middle of the column where traces of O2, will be present
c) in the lower portion of the column, where no O2 is present but other electron
acceptors such as sulfate are
d) throughout the anerobic portion of the column, but only if light is present
e) anywhere in the column where there is organic matter for these heterotrophs to
feed on.
In a Winogradsky column where would you expect to find Thiobacillus
a) at the bottom where conditions are most reducing and sulfide is the most abundant
b) in the middle where reduced sulfur compounds will be present and a slight
amount of O2 will be found as well
c) in the lower portion of the column, where no O2 is present but other electron
acceptors such as sulfate are present
d) throughout the anerobic portion of the column, but only if light is present
e) throughout the aerobic portion of the column
Thiobacillus causes severe pollution problems with poorly disposed mine tailings
a) because they utilize organic matter as their energy source and release toxic waste
products
b) because they convert ferric iron to ferrous which is highly toxic
c) they oxidize iron pyrites to ferric iron and sulfate releasing a large amount of
H+ into streams and rivers
d) because they convert ferric to ferrous iron which is highly toxic
e) because they use up all of the carbon dioxide in the water
In which environments would you expect to find Methanogens
a) they are Archaea so they are not abundant in the modern world
b) in anoxic wetlands, or deep in the mud of lakes and ponds
c) in the guts of animals
d) b and c are both true
e) a and b are both true
Sulfate reducing bacteria can be of considerable use in bioremediation because
a) have metal reductases which can precipitate out uranium from water
b) can be used to treat sewage because they can remove nutrients
c) can remove H+ ions from acidified water
d) they are capable of methylating inorganic mercury
e) both a and c are true.
Where would you expect to find Thiocapsa
a) in oxygen rich waters where there is little dissolved organic matter
b) near the bottom in lakes and ponds where there is little or no oxygen and sulfide is
present
c) at depths where some light is present
d) both b and c are true
e) none of these are true
Halobacterium are considered photoheterotrophs because
a) they require light to fix CO2 into organic matter
b) they emit bioluminescence using ATP from heterotrophic activity
c) they use light energy trapped by bacteriorhodopsin, and stored as ATP to
build their biomass from simple organic molecules
d) they produce bacteriorhodopsin a pigment that absorbs light
e) none of these are true
In examining a green ball a few mm across attached to an aquatic macrophyte, you find
that it contains an array of short tapered filaments with small anucleate cells, some
heterocysts, and some oblong akinetes. You have likely found
a) Nostoc
b) Aphanizomenon
c) Microcystis
d) Rivularia
e) Cladophora
In examining green cells found in cavities growing within Azolla leaves, you find them to
be small, circular cells arranged in filaments with heterocysts. You have likely found
a) Anabaena
b) Microcystis
c) Rivularia
d) Oscillatoria
e) None of these
In examining green material growing on rocks downstream from the sewage plant
effluent you find find greenish filaments with anucleate cells shorter than wide growing
within a thin gelatinous sheath, with no filaments or akinetes. You have likely found
a) Oscillatoria
b) Lyngbya
c) Cladophora
d) Microcystis
e) None of these
In a plankton sample you find a bloom of small greenish cells, with no chloroplasts
growing separately within a gelatinous matrix, with no heterocysts or akinetes. You have
likely found
a) Oscillatoria
b) Lyngbya
c) Aphanizomenon
d) Microcystis
e) Chlorella
In a plankton sample you find a bloom of filamentous dark anucleaute greenish cells,
arranged in irregular sheets. The filaments contain some heterocysts. You have likely
found
a) Oscillatoria
b) Melosira
c) Aphanizomenon
d) Ulva
e) None of these
Cyanobacteria
a) are photoautotrophs
b) have no chloroplasts
c) are sometimes toxic and unpalatable to herbivores
d) grow well at warm summer temperatures
e) all of these are true
Species that undergo meiosis
a) produce gametes that are individually unique
b) are diploid for at least a part of their life cycle
c) produce spores during some stage of their life cycle
d) consist of an array of genetic clones
e) both a and b are true
Species that undergo zygotic meiosis
a) do not undergo mitosis in the diploid state
b) increase their numbers asexually by producing haploid spores
c) produce diploid spores
d) generally have a quiescent zygote
e) a, b, and d are all true
A lineage that undergoes zygotic meiosis can mutate to a sporic biphasic life cycle in one
step by
a) undergoing meiosis in the zygote stage
b) dividing mitotically as a zygote to produce a functioning diploid organism
c) by eliminating the haploid stage from its life cycle
d) by producing gametes instead of spores at meiosis
e) none of these are true
A lineage that undergoes sporic meiosis can mutate in a single step to undergo gametic
meiosis by
a) undergoing meiosis in the diploid (sporophyte) stage
b) eliminating meiosis from its life cycle
c) by producing gametes instead of spores at meiosis
d) by producing both megaspore and microspores from its sporangia
e) this change cannot be accomplished in a single step
Meiosis enhances genetic variation among gametes or spores because
a) chromosomes of maternal and paternal origin sort independently
b) crossing over produces recombinant chromosomes not present in either parent
c) natural selection favours increased diversity
d) meiosis leads directly to gamete production and fertilization is a random process
e) both a and b are true
Evolutionary biologists are puzzled about the origin and widespread distribution of sex in
the living world because
a) populations that are asexual generally have higher fecundity than sexual ones.
b) production of male organisms and gametes specifically for the purpose of genetic
recombination is a costly process.
c) Although most lineages of higher plants and animals are sexual, asexual strains
have apparently arisen spontaneously in most taxa and often seem to be quite
successful, in some cases persisting for millions of years.
d) there is no one striking advantage to sex that can clearly offset the apparent
disadvantages
e) all of these are true.
Diploid cells have two copies of their genome, and this can be advantageous because
a) it allows for increased genetic redundancy would makes them less vulnerable
to mutagens
b) it permits them to combine with other cells and exchange genetic material
c) it allows them to complete the cell cycle faster and thus multiply more rapidly
d) requires them to accumulate more nitrogen and phosphorus in their cells to
support growth
e) all of these are true
Algae that produce gametes that are designated + or – instead of male or female, are
called
a) oogamous
b) anisogamous
c) isogamous
d) biphasic
e) none of the above
Filamentous green algae such as Oedogonium or Ulothrix have zygotic meiosis life
cycles that differ from Chlamydomonas in that
a) meiosis does not occur in the zygote, but is deferred to a later stage in the life
cycle
b) they are oogamous, but Chlamydomonas is isogamous
c) asexual growth potential is divided between increasing filament length and
zoospore production which increases the number of filaments
d) both b and c are true
e) none of these are true
Life cycles involving conjugation are a special case of which type of life cycle
a) zygotic meiosis
b) sporic meiosis
c) gametic meiosis
d) none of these
In Oedogonium we can infer that the mating type/sex of a cell is not determined at the
point where it hatches from the zygote because
a) there is no sexual stage in the life cycle
b) antheridia and oogonia form next to each other on the same filament
c) the same filaments give rise to both gametes and zoospores
d) filaments are formed when zoospores settle, attach themselves are begin to divide
e) none of these
In isogamous algae the mating type designated as + is functionally the female because
a) the gamete of the + mating type is larger
b) the genetic material in the zygote chloroplast usually has originated in the +
gamete
c) there is no way to tell which of the two is female because they are
morphologically identical
d) none of these are true
A widespread freshwater filamentous green alga that has a sporic meiosis (biphasic) life cycle is
a) Mougeotia
b) Stigeoclonium
c) Zygnema
d) Cladophora
e) Melosira
You collect some green algae attached to rocks along the shore of a large lake. The alga
has branched filaments, and the cells are large (nearly 0.5 mm) and contain a nucleus and
many disc-like chloroplasts. You have most likely found
a) Cladophora
b) Stigeoclonium
c) Zygnema
d) Oedogonium
e) Spirogyra
You collect some pondwater and find green spherical hollow colonies with daughter
colonies inside embedded in a gelatinous matrix. Each of the cells has a single U-shaped
chloroplast and a pair of flagellae. You have like found
a) Chlamydomonas
b) Volvox
c) Microcystis
d) Pediastrum
e) Hydrodictyon
You collect some pondwater and find cells composed of two mirror image halves with a
cellulose wall, a large green chloroplast, and a nearly centrally located nucleus. Some of
these cells are paired up with others and forming a conjugation vesicle. You have likely
found
a) Scenedesmus
b) Ankistrodesmus
c) a desmid
d) Pediastrum
e) Cymbella
You collect some pale greenish filaments from some nearshore stones. The cells are
rectangular with many small discoid chloroplasts, a nucleus and a cellulose wall. You
find that some of the filaments are linked together with tube-like bridges, and the cells of
both filaments are empty with dark zygospores aligned between them. You have likely
found
a) Spirogyra
b) Zygnema
c) Oedogonium
d) Ulothrix
e) Mougeotia
Diatoms do well in the plankton of large lakes during spring and fall because
a) the wind-mixed unstratified water column is nutrient rich
b) the well mixed watercolumn keeps these relatively dense cells from settling to the
bottom
c) the high viscosity of cold water slows down the sinking speed of diatoms
d) diatoms can stand to live at low light levels
e) all of these are true
The chloroplasts of diatoms usually appear brown because
a) they have little chlorophyll in them
b) they contain a type of chlorophyll which is not green
c) they are rich in carotenoids which usually impart a brownish appearance
d) none of these are true
You collect a plankton sample from a large lake during springtime and find a many long
siliceous filaments composed of cylindrical cells in girdle view, that contain large brown
chloroplasts. You have likely found
a) Melosira
b) Lyngbya
c) Uroglena
d) Ceratium
e) Fragillaria
Although the mosses and pterophytes are quite dependent on water, the most plausible
reason why they haven’t done nearly as well in the aquatic environment as flowering
plants is
a) the leaves and their stomata do not function effectively in water
b) flowers are required in order for fertilization to be completed in water
c) their rhizomes are not able to tolerate anoxic sediments
d) their spores are adapted to be released and transported by air, which limits
them to very shallow, marginal aquatic environments
e) they are much more primitive than flowering plants
The life cycle of mosses remains strongly dependent on water because
a) the leaves lack a waxy cuticle and stomatal control mechanism for minimizing
water loss
b) their rhizomes and stems lack efficient conducting tissues to transport water
c) their spores are released into water and require water for dispersal
d) the male gametes are flagellated and require water in order to locate the
archegonium
e) a, b and d are all true
The life cycles of pterophytes (ferns, horsetails, quillworts etc) remain somewhat
dependent on water because
a) the leaves lack a waxy cuticle and stomatal control mechanism for minimizing
water loss
b) they lack effective rooting and vascular tissue
c) their spores are released into water and require water for effective dispersal
d) the male gametes are flagellated and require at least a film of water to locate
the archegonium
e) a, b and d are all true
The green portion of a moss plant
a) is the haploid gametophyte and produces antheridia and archegonia
b) is the diploid sporophyte
c) provides nutritional support for the sporophyte
d) produces haploid spores
e) both a and c are true
The reproductive stems of horsetails
a) are haploid, whereas the vegetative stems are diploid
b) produce male and female gametes
c) are part of the sporophyte and have strobilae at their tips which produce
haploid spores
d) produce both megaspores and microspores
e) are often found growing as submerged macrophytes
The aquatic fern, Azolla, is somewhat atypical compared to most ferns in that
a) it does not have sporangia
b) they grow on the water surface with their rhizomes suspended in the water,
instead of rooted in soil
c) it is heterosporous rather than homosporous like most ferns
d) b and c are both true
e) a and b are both true
Aquatic ferns of the genus Salvinia have become invasive pests in many parts of the
world because
a) they are polyploid (sterile) and are capable of rapid vegetative growth, because
they do not expend energy on spore production
b) spores are not really required by ferns for effective dispersal
c) human activities including boat travel, canals, barges etc, and attempts to
eradicate them probably all serve to spread these plants, which then grow rapidly
once they gain access to open habitat
d) their seeds are likely being dispersed by migratory waterfowl
e) all of these are likely true
f) a and c are likely true
The female gametophyte in a flowering plant
a) is a free living haploid organism produced from a germinating megaspore
b) has no independent existence, and is limited to an 8-celled entity inside the ovule
of a pistillate flower
c) grows downward within the pistil of a flower when a pollen grain germinates
d) is produced from a megaspore
e) both b and d are true
The pollen grain of a flowering plant is
a) homologous to the microspore in Azolla
b) produced on an anther
c) is a haploid spore produced from a microsporangium
d) usually dispersed by insects or wind
e) all of the above are true
Azolla and Isoetes are similar in that
a) they have heterosporous life cycles
b) they grow as small leaf clusters on the water surface that have trailing rhizomes
c) they are both flowering plants
d) they are both aquatic pterophytes
e) both a and d are true
Vallesneria are similar to Azolla and Isoetes
a) in that they are all heterosporous
b) in that they have tiny flowers that are wind pollinated
c) in that they can sprout asexually from rhizomes or terminal buds
d) in that they produce separate male and female flowers
e) both a and c are true
Lemna is similar to Azolla and Salvinia in that
a) they are all heterosporous
b) that they rarely reproduce sexually
c) in that they are capable of asexual proliferation from fragments or terminal buds
d) in their growth form which is a cluster of leaves floating on the water surface with
rhizomes suspended from it
e) all of these are true
Myriophyllum exhibits several traits that are commonly seen in aquatic flowering plants
a) finely dissected leaves that maximize surface/volume ratio
b) relatively high shoot/rhizome ratio
c) tiny flowers that are wind pollinated
d) ability to proliferate vegetatively through fragmentation
e) all of these are true
Typha differs from most aquatic plants
a) in that their flowers are large, conspicuous and insect pollinated
b) in that they produce extensive rhizomes through which they can proliferate
asexually
c) in that their leaves are generally not consumed by aquatic herbivores so their
biomass enters the food chain mostly after they die, decay and are consumed by
detritivores
d) a and b are both true
e) b and c are both true
The gliding motion of Dugesia on a substrate
a) does not require a hydrostatic skeleton/coelom
b) is produced mainly by the cilia on its ventral surface
c) involves cilia beating within a thin layer of mucous
d) a, b and c are all true
e) none of these are true
The feeding of Dugesia and Hydra are similar in that
a) their mouth also serves as the anus
b) they are both carnivorous and feed on large prey
c) they both have a muscular pharynx
d) both a and b are true
e) a, b, and c are all true
Rhabdocoels differ from Triclads
a) in regards to their feeding mechanism
b) in the shape of their intestine
c) in that rhabdocoels are not carnivores whereas triclads are
d) mainly in size
e) none of these
True or False
In Spirogyra all of the cells in the same filament are of the same mating type/sex.T
In isogamous algae the gamete designated as the + or – mating types are functionally
indistinguishable. F
The overall similarity of the Charophycean life cycle to that of plants is one of the
reasons that we consider them the likely ancestors of plants F
In algae that undergo conjugative life cycles there are no flagellated spores or gametes. T
Although Volvox is colonial and Chlamydomonas is unicellular their sexual life cycles are
nearly identical except that Volvox is oogamous whereas Chlamydomonas is isogamous.
T.
The only flagellated diatom cells are the sperm of pennate diatoms. T
A culture of diatoms is growing asexually by mitotic divisions. These cells are all
haploid. F
Bryophytes and pterophytes, which retain some dependence on water for sexual
reproduction, have not done nearly as well in the aquatic environment as their more
terrestrially adapted descendents, the flowering plants. T.
The microspore of Isoetes is homologous to the pollen grain of Potamogeton. T
The tentacles of Hydra and Plumatella function similarly. F
Mesostoma is a voracious predator on mosquito larvae and other zooplankton. T
Fill in the blanks
The only two groups of freshwater organisms that we have encountered so far, for which
silicon is an essential element are the _Diatoms________ and the _sponges_______.
Diatoms that appear circular in _valve________ view are referred to as __centric_______
diatoms
Many aquatic plants can spread rapidly, asexually, through _fragmentation__________.
The anther in a flowering plant produces pollen grains from a structure homologous to
the __microsporangium___________of Azolla or Isoetes
The life cycle of Azolla and Isoetes both have __heterosporous____________ life cycles,
which differs from most ferns and horsetails which are
_homosporous_________________.
Freshwater sponges can withstand adverse conditions by producing asexual resistant
stages called __gemmules__________ which are functionally analogous to the
__statoblasts___________ of freshwater bryozoans.
The filter-feeding mechanism of a sponge is driven by the __collar
cells_______________, whereas that of the bryozoan uses
its__lophophore____________________.
The name rhabodcoel refers to their __rod-shaped_____________ gut cavity
The antero-lateral sensory structures in triclads are called __auricles_____________.
Explain—i.e give an explanation for the following:
metal reductases could be useful to sulfate reducing bacteria
reduced metals will precipitate as metal sulphides which removes sulphide ions from
the water. Sulphide ions are a waste product of the metabolism of sulphate
reducers.
Methanogens are of considerable interest to people who are trying to predict climate
change
Methane is a very potent greenhouse gas and therefore understanding the bacteria
that produce methane of are considerable importance to climate change modeling.
Sulfate reducing bacteria would not do well in the presence of oxygen
Sulphate reducing bacteria are anerobic heterotrophs and would not do well in
competition with aerobic heterotrophs for organic matter.
Thiocapsa are generally found in a layer close to the substrate but not often in the mud or
high in the water column
These are photosynthetic bacteria and need to be found where there is light, yet
reduced sulphur is still present.
There is no way that a lineage undergoing zygotic meiosis can mutate in a single step to a
gametic meiosis life cycle.
Two changes are required for this transition to occur. First the zygote needs to
delay meiosis and form a diploid mitotic stage (sporophyte). After this, when
meiosis does occur the sporophyte needs to produce gametes directly, rather than
spores.
Why meiosis increases the variety of genetic combinations in a population
Meiosis independently assorts the chromosomes in the cell, so that the haploid cells
produced have all combinations present. Crossing over also produces an infinite
variety of new chromosomal combinations that weren’t present in the initial diploid
cell.
How we can infer that the mating type/sex of the cells released from an Oedogonium
zygospore is not predetermined at the point of release.
Both sexes appear side by side within the same filament, which originated from one
cell when the zygospore germinated.
Suggest a possible reason why many of the filamentous algae that undergo conjugation
have a slimy external surface that prevents epiphytes from attaching to them
The epiphytes that commonly grow on filamentous alge could obstruct conjugation
by preventing the filaments from lining up properly.
Root development in aquatic flowering plants is much less than that found in their
terrestrial counterparts.
Terrestrial plant roots need to anchor a much heavier plant than aquatic plant roots
do, since aquatic plants are essentially weightless since they are immersed in a much
more buoyant medium.
Explain why it is advantageous to Sphagnum to produce leaves that resist decay when
they are dead, and contain spongy lacunae that absorb water.
Mosses need to stay wet as much as possible, and the spongy lacunae of dead mosses
can help retain water in the immediate area that the living gametophytes are
growing. If they are decomposed they would of course lose their spongy texture,
and there would be little peat buildup.
How eutrophication generally affects submerged macrophytes, and plants like Lemna,
Azolla and Salvinia are not susceptible to these effects.
Submerged plants can be impacted by eutrophication (increased nutrient loading to
water) since these nutrients directly stimulate phytoplankton growth which reduces
light penetration and therefore restricts the depths to which macrophytes can grow.
Macrophytes only access nutrients from sediments so nutrient inputs would only be
indirectly available to them. Lemna, Azolla and Salvinia all float on the surface and
have rhizomes that take up nutrients directly from the water, so they would be
positively impacted by enrichment.
Why plants like Potamogeton amplifolius or P. praelongus produce better fish habitat
than plants like Myriophyllum and Elodea.
Their leaves are larger and they grow in a spaced out manner not in a densely
packed weed bed. The increased spacing in the community allows a wide range of
fish sizes to hide in the weeds, but still allows them to see and ambush food. In
dense Myriophyllum and Elodea beds, there is no space for larger fish to operate,
and only tiny fish can manage to feed.
Why most aquatic plants have tiny inconspicuous flowers compared to their terrestrial
counterparts.
Aquatic plants are wind or water pollinated rather than insect pollinated. The large
conspicuous flowers of terrestrial flowering plants are mostly adapted to facilitate
insect pollination.
How a sponge moves water through its body and feeds itself.
The flagellar motion of the collared choanocytes pumps water through the
spongocoel and out the oscula. This sucks water into the body through the ostia.
The small particles contained in the water deposit on the collars which function as a
kind of sieve, and the particles are ingested to form food vacuoles in the
choanocytes, which transfer these on to other cells in the sponge body.
The function of the mesogloea in a sponge
The mesogloea provides a kind of structure to the sponge body wall, by virtue of the
spicules it contains, it also contains undifferentiated amoebocytes which can help
maintain the body since they can differentiate into either choanocytes, ostiocytes or
epidermal cells.
The lophophore of a bryozoan looks superficially like the tentacular crown of the
cnidarians polyp, but they function very differently.
The bryozoans lophophore is a filter-feeding adaptation whereas the cnidarian
tentacles are equipped with nematocysts for capturing large prey.
Sponges and bryozoans both filter-feed but the way they do it is quite different.
Sponges use collar cells which pump water and strain out particles on the sieve-like
collar, whereas bryozoans use mucous coated tentacles on the lophophore to trap
small particles, which are moved toward the mouth by ciliary action.
Animals that eat large prey whole often use the same opening as mouth and anus.
It is physically simpler to disgorge the remains of a large prey by vomiting it back
out the mouth, than to break it up so much that it can be moved along through an
intestine.
Matching
Aphanizomenon
Azolla
Bryophytes
Ceratium
Filamentous diatoms
Halobacterium
Mesostoma
Platyhelminthes
Raphed diatoms
Rivularia
Sagittaria
Spirogyra
Sulfate reducers
Thiocapsa
Triclads
Vallisneria
Photoheterotroph --Halobacterium
metal reductases—sulphate reducers
anaerobic photoautotroph--Thiocapsa
short tapered filaments with basal heterocysts and akinetes-Rivularia
filaments of tiny rectangular cells arranged in irregular sheets-Aphanizomenon
long spiral chloroplast--Spirogyra
capable of a gliding motion on a substratum—raphed diatoms
cells joined at their valve faces—filamentous diatoms
Mixotroph--Ceratium
parasitic sporophyte--bryophytes
heterosporous fern--Azolla
male and female flowers on separate shoots--Vallinsneria
anthers and pistils in separate flowers on the same plant-Sagittaria
potential mosquito control agents--Mesostoma
free living flatworms, flukes and tapeworms--Platyhelminthes
simultaneous hermaphrodites--Triclads.
Short essays
Mine wastes can have a devastating impact on aquatic ecosystems because. Explain the
role of Thiobacillus in these effects, and how mine wastes should be handled to prevent
this.
Humans have always had a love-hate relationship with Cyanobacteria, Explain
Many benthic diatoms exhibit a life cycle that alternates between a solitary motile phase
and an attached filamentous phase. Explain how this would be advantageous for life in a
stream or a wave washed shore.
Although the mosses and pterophytes are quite dependent on water, they haven’t done
nearly as well in the aquatic environment as flowering plants. Expand on this point, and
using what you know about plant life cycles suggest an explanation for this pattern.
Salvinia spp, most of which are polyploid and sterile are proliferating as pests in many
parts of the world. Many other aquatic plants have also become major pests through
vegetative proliferation. Suggest a mechanism by which an asexual fern can spread
effectively enough to become major pests without being able to produce spores, which
are required by most ferns for effective dispersal.
Azolla, Salvinia, and Lemna all share the same basic growth form. Describe it and
suggest some advantages and disadvantages to this growth form and in which types of
aquatic habitat they are successful and where they are not.
Ferns as a group remain at least partially dependent on water for reproduction, and,
though they like wet places, few have become truly aquatic. Moreover, those that are
aquatic have a growth form quite atypical for ferns. Expand on this, and based on your
knowledge of the fern life cycle suggest and explanation for these observations.
Altlhough Turbellarians are often considered to be very primitive organisms because they
have no coelom, they are actually quite sophisticated animals functionally. Explain.