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BIO 111 EXAM 2
Protists are eukaryotes that don't include plants, animals and fungi. Monophyletic includes all
descendants and paraphyletic are some of the descendants. The term "protist" is paraphyletic, meaning
it does not include all descendants of a common ancestor. While eukaryotes as a whole are
monophyletic, protists excludes plants, animals, and fungi, making it paraphyletic.
Define protist. Is this a monophyletic term? Why or why not?
No, not all protists are unicellular. While most protists are small and unicellular, some are multicellular
and can reach sizes comparable to plants, animals, or fungi.
Multicellularity evolved independently dozens of times in eukaryotes. For example, brown algae, which
belong to the stramenopile group, evolved multicellularity independently of plants, despite their similar
appearance and photosynthetic ability.
Are all protists unicellular?
The loss of the cell wall was a crucial evolutionary step in eukaryotic origins because it allowed for a
more flexible cell surface. This flexibility enabled cells to:
- Grow larger while maintaining a high surface area-to-volume ratio by developing infolded membranes,
which improved nutrient and oxygen diffusion.
- Engulf other cells through phagocytosis, facilitating endosymbiosis, which led to the development of
organelles like mitochondria and chloroplasts.
Why was the loss of the cell wall an important evolutionary step in terms of the origins of eukaryotes?
Primary endosymbiosis means engulfment of cyanobacterium, only occurs once so the chloroplast
engulfed is monophyletic.
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Secondary endosymbiosis engulfment of cyanobacterium that was already engulfed
The difference is that one occurred once before and the secondary is the second time it's happened.
Primary endosymbiosis occurs when a cell engulfs a proteobactrium (first) and cyanobacterium giving
rise to mitochondria, forming a mutualistic relationship that leads to the evolution of chloroplasts. This
happened only once in the lineage that gave rise to red algae and green plants, making all chloroplasts
monophyletic.
Secondary endosymbiosis happens when a eukaryote engulfs another eukaryote that already has
chloroplasts from primary endosymbiosis. This allowed chloroplasts to spread to various protist
lineages. A key piece of evidence for secondary endosymbiosis is that many protists have chloroplasts
with three me
What is the difference between primary and secondary endosymbiosis?
An apicoplast is a non-photosynthetic plastid organelle derived from a chloroplast, found in
apicomplexan parasites. It is essential for their survival and often crucial for pathogenicity (ability of an
organism to cause disease).
An example of an organism that has an apicoplast is Plasmodium, the parasite that causes malaria.
What is an apicoplast? What is an example of an organism that has an apicoplast?
The contractile vacuole in Paramecium functions to expel excess water from the cell, helping maintain
water balance (osmoregulation).
Since Paramecium lives in freshwater and is hypertonic to its environment, water constantly diffuses
into the cell. The contractile vacuole uses ATP to pump water out, preventing the cell from swelling and
bursting.
Hypotonic vs hypertonic: hypotonic (want water to go into cell as solutes are higher concentration inside
cell) hypertonic (solutes are higher concentration outside of cell so water will follow them out)
What is the function of the contractile vacuole in Paramecium? Why do these organisms need this
structure?
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The long, thin pseudopods in foraminiferans extend from shell and are used to trap smaller plankton for
feeding, functioning like a spider web to capture prey
What is the function of the long thin pseudopods in formaniferans?
At first glance, the fact that Giardia and some other excavates lack mitochondria might suggest that the
nucleus evolved before the mitochondrion, implying that endosymbiosis happened later.
However, genetic evidence strongly suggests otherwise. Giardia's nuclear genome contains
mitochondrial genes, indicating that its ancestors once had mitochondria but later lost them. This
supports the idea that mitochondria evolved first, followed by the nucleus, and that some eukaryotes
secondarily lost their mitochondria. This process is consistent with how mitochondrial genes often
transfer to the nuclear genome, as seen in many eukaryotic lineages like yeast.
Explain why the biology of Giardia may at first glance seem to support the notion that the nucleus
evolved before the mitochondrion. What evidence conclusively demonstrates that this is unlikely to be
the case?
It makes sense that antibiotics can cause the irreversible loss of photosynthetic pigments in euglenids
because chloroplasts originated from bacteria through endosymbiosis so their ancient bacteria. Since
some antibiotics specifically target bacterial structures and functions, they can also disrupt chloroplasts,
leading to their permanent inactivation.
Once neutralized, the chloroplasts cannot regain function, and all future descendants of the affected
euglenid will also lack photosynthetic pigments, effectively turning them into permanent heterotrophs.
Why might it make sense that antibiotics that are typically used to combat bacteria can lead to
irreversible loss of photosynthetic pigments in euglenids?
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Trypanosomes, which cause diseases like sleeping sickness, Chagas disease, and leishmaniasis, are
typically spread in human populations by insect vectors. These complex life cycles often involve the
following mechanisms:
Sleeping sickness is spread by the tsetse fly, which transmits the trypanosome from one human to
another. The parasite affects the nervous system, leading to comas if untreated.
Chagas disease is transmitted by assassin bugs (or kissing bugs), which bite humans and introduce the
trypanosome, leading to complications, particularly with the heart.
Leishmaniasis is spread by sand flies, which carry the trypanosome. Depending on the form the parasite
takes, it can cause skin lesions or be lethal in some cases.
In all these cases, the disease-causing protists rely on insect vectors to move between hosts and
complete their life cycle.
Trypanosomes typically have very complex life cycles. How are these disease-causing protists typically
spread in human populations?
Amoebas have lobe-shaped pseudopods that are shorter and thicker. These are primarily used for
phagocytosis, where the pseudopods surround and engulf prey, bringing it into the cell.
Rhizarians, on the other hand, have long, thin pseudopods that are used for trapping prey, similar to a
spider web, before bringing it in.
In summary, while both types of pseudopods are used for capturing food, amoeba pseudopods are
better suited for engulfing prey, whereas rhizarians use theirs for a more trapping mechanism.
How do the pseudopods of amoebas and rhizarians differ in structure and function?
A plasmodium is an acellular slime mold structure made up of thousands of nuclei that are not confined
in separate cells. Plasmodium is the genus of apicomplexan protists that causes malaria
What is the difference between plasmodium (when referring to slime molds) and Plasmodium?
Aggregation: Many individual amoeboid cells come together to form a "slug" (unit of a lot of cells)
2026/2027 BIO 111 EXAM 2 - BIO 111 EXAM 2.pdf BIO 111 EXAM 2.pdf? Verified answers with rationales
BIO 111 EXAM 2
Protists are eukaryotes that don't include plants, animals and fungi. Monophyletic includes all
descendants and paraphyletic are some of the descendants. The term "protist" is paraphyletic, meaning
it does not include all descendants of a common ancestor. While eukaryotes as a whole are
monophyletic, protists excludes plants, animals, and fungi, making it paraphyletic.
Define protist. Is this a monophyletic term? Why or why not?
No, not all protists are unicellular. While most protists are small and unicellular, some are multicellular
and can reach sizes comparable to plants, animals, or fungi.
Multicellularity evolved independently dozens of times in eukaryotes. For example, brown algae, which
belong to the stramenopile group, evolved multicellularity independently of plants, despite their similar
appearance and photosynthetic ability.
Are all protists unicellular?
The loss of the cell wall was a crucial evolutionary step in eukaryotic origins because it allowed for a
more flexible cell surface. This flexibility enabled cells to:
- Grow larger while maintaining a high surface area-to-volume ratio by developing infolded membranes,
which improved nutrient and oxygen diffusion.
- Engulf other cells through phagocytosis, facilitating endosymbiosis, which led to the development of
organelles like mitochondria and chloroplasts.
Why was the loss of the cell wall an important evolutionary step in terms of the origins of eukaryotes?
Primary endosymbiosis means engulfment of cyanobacterium, only occurs once so the chloroplast
engulfed is monophyletic.
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,2026- Complete Exam Prep Bundle:BIO 111 EXAM 2 BIO 111 EXAM 2.pdf Page 2 of 53
Secondary endosymbiosis engulfment of cyanobacterium that was already engulfed
The difference is that one occurred once before and the secondary is the second time it's happened.
Primary endosymbiosis occurs when a cell engulfs a proteobactrium (first) and cyanobacterium giving
rise to mitochondria, forming a mutualistic relationship that leads to the evolution of chloroplasts. This
happened only once in the lineage that gave rise to red algae and green plants, making all chloroplasts
monophyletic.
Secondary endosymbiosis happens when a eukaryote engulfs another eukaryote that already has
chloroplasts from primary endosymbiosis. This allowed chloroplasts to spread to various protist
lineages. A key piece of evidence for secondary endosymbiosis is that many protists have chloroplasts
with three me
What is the difference between primary and secondary endosymbiosis?
An apicoplast is a non-photosynthetic plastid organelle derived from a chloroplast, found in
apicomplexan parasites. It is essential for their survival and often crucial for pathogenicity (ability of an
organism to cause disease).
An example of an organism that has an apicoplast is Plasmodium, the parasite that causes malaria.
What is an apicoplast? What is an example of an organism that has an apicoplast?
The contractile vacuole in Paramecium functions to expel excess water from the cell, helping maintain
water balance (osmoregulation).
Since Paramecium lives in freshwater and is hypertonic to its environment, water constantly diffuses
into the cell. The contractile vacuole uses ATP to pump water out, preventing the cell from swelling and
bursting.
Hypotonic vs hypertonic: hypotonic (want water to go into cell as solutes are higher concentration inside
cell) hypertonic (solutes are higher concentration outside of cell so water will follow them out)
What is the function of the contractile vacuole in Paramecium? Why do these organisms need this
structure?
2026/2027 BIO 111 EXAM 2 - BIO 111 EXAM 2.pdf BIO 111 EXAM 2.pdf? Verified answers with rationales
,2026- Complete Exam Prep Bundle:BIO 111 EXAM 2 BIO 111 EXAM 2.pdf Page 3 of 53
The long, thin pseudopods in foraminiferans extend from shell and are used to trap smaller plankton for
feeding, functioning like a spider web to capture prey
What is the function of the long thin pseudopods in formaniferans?
At first glance, the fact that Giardia and some other excavates lack mitochondria might suggest that the
nucleus evolved before the mitochondrion, implying that endosymbiosis happened later.
However, genetic evidence strongly suggests otherwise. Giardia's nuclear genome contains
mitochondrial genes, indicating that its ancestors once had mitochondria but later lost them. This
supports the idea that mitochondria evolved first, followed by the nucleus, and that some eukaryotes
secondarily lost their mitochondria. This process is consistent with how mitochondrial genes often
transfer to the nuclear genome, as seen in many eukaryotic lineages like yeast.
Explain why the biology of Giardia may at first glance seem to support the notion that the nucleus
evolved before the mitochondrion. What evidence conclusively demonstrates that this is unlikely to be
the case?
It makes sense that antibiotics can cause the irreversible loss of photosynthetic pigments in euglenids
because chloroplasts originated from bacteria through endosymbiosis so their ancient bacteria. Since
some antibiotics specifically target bacterial structures and functions, they can also disrupt chloroplasts,
leading to their permanent inactivation.
Once neutralized, the chloroplasts cannot regain function, and all future descendants of the affected
euglenid will also lack photosynthetic pigments, effectively turning them into permanent heterotrophs.
Why might it make sense that antibiotics that are typically used to combat bacteria can lead to
irreversible loss of photosynthetic pigments in euglenids?
2026/2027 BIO 111 EXAM 2 - BIO 111 EXAM 2.pdf BIO 111 EXAM 2.pdf? Verified answers with rationales
, 2026- Complete Exam Prep Bundle:BIO 111 EXAM 2 BIO 111 EXAM 2.pdf Page 4 of 53
Trypanosomes, which cause diseases like sleeping sickness, Chagas disease, and leishmaniasis, are
typically spread in human populations by insect vectors. These complex life cycles often involve the
following mechanisms:
Sleeping sickness is spread by the tsetse fly, which transmits the trypanosome from one human to
another. The parasite affects the nervous system, leading to comas if untreated.
Chagas disease is transmitted by assassin bugs (or kissing bugs), which bite humans and introduce the
trypanosome, leading to complications, particularly with the heart.
Leishmaniasis is spread by sand flies, which carry the trypanosome. Depending on the form the parasite
takes, it can cause skin lesions or be lethal in some cases.
In all these cases, the disease-causing protists rely on insect vectors to move between hosts and
complete their life cycle.
Trypanosomes typically have very complex life cycles. How are these disease-causing protists typically
spread in human populations?
Amoebas have lobe-shaped pseudopods that are shorter and thicker. These are primarily used for
phagocytosis, where the pseudopods surround and engulf prey, bringing it into the cell.
Rhizarians, on the other hand, have long, thin pseudopods that are used for trapping prey, similar to a
spider web, before bringing it in.
In summary, while both types of pseudopods are used for capturing food, amoeba pseudopods are
better suited for engulfing prey, whereas rhizarians use theirs for a more trapping mechanism.
How do the pseudopods of amoebas and rhizarians differ in structure and function?
A plasmodium is an acellular slime mold structure made up of thousands of nuclei that are not confined
in separate cells. Plasmodium is the genus of apicomplexan protists that causes malaria
What is the difference between plasmodium (when referring to slime molds) and Plasmodium?
Aggregation: Many individual amoeboid cells come together to form a "slug" (unit of a lot of cells)
2026/2027 BIO 111 EXAM 2 - BIO 111 EXAM 2.pdf BIO 111 EXAM 2.pdf? Verified answers with rationales
