Chapter 28: Protists (Part 1, Week 5) Flashcards

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1
Q

T/F Protists are eukaryotes, live in most habitats, and are mostly microscopic in size.

A

True

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2
Q

What is a photosynthetic protist that generates at least half of the oxygen in the Earth’s atmosphere and produce organic compounds that feed marine and freshwater animals?

A

Algae

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3
Q

What is the oil that fuels our cars and industries derived from that accumalted on the ocean floor over millions of years?

A

Pressure-cooked algae!

Today, algae are being engineered into systems for cleaning pollutants from water or air and for producing renewable biofuels.

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4
Q

T/F Protists also include some parasites that cause serious human illnesses.

A

True

For example, in 1993, the waterborne protist
Cryptosporidium parvum sickened 400,000 people in Milwaukee, Wisconsin, costing $96 million in medical expenses and lost worktime.

Because this protist is exceptionally tolerant of the disinfectant chlorine, it is currently the major cause of diarrhea illness associated with aquatic recreational facilities such as swimming pools and waterparks.

Species of the related genus Plasmodium, which is carried by mosquitoes in many warm regions of the world, cause the disease malaria. Every year, nearly 500 million people become ill with malaria, and more than 2 million die of this disease.

As we will see, sequencing the genomes of these and other protist species has suggested new ways of battling such deadly pathogens.

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5
Q

[Start 28.1 Introduction to Protists]

What does the term protist come from meaning “first” in Greek, reflecting the observation that protists were Earth’s first eukaryotes?

A

Protos

Protists are eukaryotes that are not classified in the plant, animal, or fungal kingdoms.

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6
Q

What are the two common charateristics that protists display?

A

They are most abundant in moist habitats, and most of them are microscopic in size.

Protists play diverse ecological roles, live in diverse habitats, and display diverse types of motility.

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7
Q

What are the three major ecological types that protists occur in?

A

Algae, protozoa, and fungus-like protists

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8
Q

What is a term that applies to about 10 phyla of protists, including mostly photosynthetic and some nonphotosynthetic species; often also includes cyanobacteria?

A

Algae (singular, alga; means seaweed)

Applies to protists that are generally photoautotrophic, meaning that most can produce organic compounds from inorganic sources by means of photosynthesis.

In addition to organic compounds that can be used as food by heterotrophs—organisms that obtain their food from other organisms—photosynthetic algae produce oxygen, which is also needed by most heterotrophs.

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9
Q

Why are algae increasingly important sources of renewable biofuels?

A

Thanks to their photosynthetic abilities.

Despite the general feature of photosynthesis, algae do not form a monophyletic group descended from a single common ancestor.

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10
Q

What is a term commonly used to describe diverse heterotrophic protists?

A

Protozoa

Commonly used to describe diverse heterotrophic protists that feed by absorbing small organic molecules or by ingesting prey.

For example, the protozoa known as ciliates consume smaller cells such as the single-celled
photosynthetic algae known as diatoms.

Like algae, protozoa do not form a monophyletic group.

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11
Q

What process does Ciliates use to ingest diatoms, a golden-pigmented oil-rich, silica walled algal cells?

A

By the process of phagocytosis

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12
Q

What are heterotrophic protists that often resemble true fungi in having threadlike, filamentous bodies and absorbing nutrients from their environment?

A

Fungus-like protists

They have bodies, nutritional mechanisms, or reproductive mechanisms similar to those ofthe true fungi. For example, fungus-like protists often have threadlike, filamentous bodies and absorb nutrients from their environment, as do the true fungi.

However, fungus-like protists are not actually related to fungi; their similar features represent cases of convergent evolution, in which species from different lineages have independently evolved similar characteristics.

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13
Q

Even though protists occupy nearly every type of moist habitat, they are particularily common and diverse in?

A

Oceans, lakes, wetlands, and rivers.

Even extreme aquatic environments such as Antarctic ice and acidic hotsprings serve as habitats for some protists. In such places, protists may swim or float in open water or live attached to surfaces such as rocks or beach sand. These different habitats influence protists’ structure and size.

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14
Q

What are protists that swim or float in fresh or salt water and are members of an informal aggregate or organisms known as? This includes bacteria, viruses, and small animals.

A

Plankton.

The photosynthetic protists in plankton are called
phytoplankton (plantlike plankton).

Planktonic protists are necessarily quite small in size; otherwise they would readily sink to the bottom.

Staying afloat is a particularly important characteristic of phytoplankton, which need light for photosynthesis.

For this reason, planktonic protists occur primarily as single cells, colonies of cells held together with mucilage, or short filaments of cells linked end to end.

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15
Q

What are communities of microorganisms that are attached by mucilage to underwater surfaces such as rocks, sand, and plants?

A

Periphyton

Because sinking is not a problem for attached protists, these often produce multicellular bodies, such as branched filaments

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16
Q

What are photosynthetic protists that can be seen with the unaided eye; also known as seaweeds?

A

Macroalgae

Most macroalgae are multicellular, often producing large and complex bodies. Macroalgae usually grow attached to underwater surfaces such as rocks, sand, docks, ship hulls, or off shore oil platforms.

Seaweeds require sunlight and carbon dioxide for photosynthesis and growth, so most of them grow along coastal shorelines, fairly near the water’s surface.

Macroalgae serve as refuges for aquatic animals, generate large amounts of organic carbon that enters aquatic food chains, and play additional important ecological roles. Humans harvest some macroalgae for use as food or crop fertilizers or as sources of industrial chemicals to make diverse commercial products.

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17
Q

What are the major types of protist movements? (3)

A

Swimming by means of flagella or cilia.

Amoeboid movement

Gliding

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18
Q

Explain what flagella are that many types of photosynthetic and heterotrophic protists use to swim?

A

They are cellular extensions whose movement is based on interactions between microtubules and the motor protein dynein.

Eukaryotic flagella rapidly bend and straighten, thereby pulling or pushing cells through the water.

Protists that use flagella tomove in water are commonly known as flagellates.

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19
Q

What are flagellates typically composed of in cells and size? Also, why are flagellates typically the size they are?

A

Flagellates are typically composed of one or only a few cells and are small—usually from 2 to 20 μm long—because flagellar motion is not powerful enough to keep larger bodies from sinking.

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20
Q

T/F Some flagellate protists are sedentary.

A

True.

Some flagellate protists are sedentary, living attached to underwater surfaces.

These protists use flagella to collect bacteria and other small particles for food.

Macroalgae and other immobile protists often produce small, flagellate reproductive cells that allow these protists to mate and disperse to new habitats

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21
Q

What are cilia?

A

Tiny hairlike extensions on the outsides of cells.

Cilia are structurally similar to eukaryotic flagella but are shorter and more abundant.

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22
Q

What is a protist that moves by means of cilia, which are tiny hairlike extensions that occur on the outside of cells and have the same internal structure as flagella?

Also, what advantage of having many cilia compared to a protist that has flagella?

A

Ciliates

Having many cilia allows ciliates to achieve larger sizes than flagellates yet still remain buoyant in water.

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23
Q

What is the third type of movement which is a kind of motion that involves extending cytoplasm into lobes, known as pseudopodia?

A

Amoeboid movement.

(from the Greek, meaning false feet (psuedopodia)).

Once these pseudopodia move toward a food source or other stimulus, the rest of the cytoplasm flows after them, thereby changing the shape of the entire
organism as it creeps along.

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24
Q

What is a protist that moves by pseudopodia, which involves extending cytoplasm into filaments or lobes?

A

Amoeba (plural, amoebae)

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25
Q

[Start 28.2 Evolution and Relationships]

T/F Protists do not form a paraphyletic group.

A

Flase. They are a paraphyletic group; they are NOT a monophyletic group

The relationships of some protists are uncertain or disputed, and new protist species are continually being discovered. As a result, concepts of protist evolution and relationships have been changing as new information becomes available.

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26
Q

What analyses in modern phylogenetics are based on to identify that protists are classified as paraphyletic groups? (2)

A

Comparisons of DNA sequences and cellular features.

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27
Q

What are one of the seven subdivisions of the domain Eukarya where many protist phyla can be classified within?

A

Supergroups

Many different supergroups that each display distinctive features.

All of the eukaryotic supergroups include phyla of protists; some, in fact, contain only protist phyla.

The supergroup Opisthokonta includes the multicellular animal and fungal kingdoms and related protists, whereas another supergroup includes the multicellular plant kingdom and the protists most closely related to it.

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28
Q

How does the study of such protists (in supergroups) help?

A

Reveals how multicellularity originated in animals, fungi, and plants.

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29
Q

What protist supergroup originated very early among eukaryotes, and is important in understanding the early evolution of eukaryotes?

A

Excavata

Many of the Excavata feed by ingesting small particles of food in their aquatic habitats.

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30
Q

When food particles are collected within the feeding groove, they are then taken into cells by a type of endocytosis called?

A

Phagocytosis (from the Greek, meaning cellular eating)

During phagocytosis, a vesicle of plasma membrane surrounds each food particle and pinches off within the cytoplasm. Enzymes within these food vesicles break the food particles down into small molecules that, upon their release into the cytosol, can be used for energy.

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31
Q

Bonus: What is the difference of the two types of endocytosis–phagocytosis and pinocytosis?

A

Phagocytosis breaks down solid material, while pinocytosis absorbs readily available nutrients in extracellular fluid hence why lysosomes are not needed.

Exocytosis does not occur in pincosytosis since there is no material that needs to be secreted. Everything it absorbs is readily available to used within the cell. It does occur at the end of phagocytosis.

32
Q

What happens to food particles after they entera feeding groove?

A

After food particles are collected in a feeding groove, they are enclosed by membrane vesicles and then digested by enzymes.

33
Q

Phagocytosis is also the basis for an important evolutionary process called what?

A symbiotic association in which a smaller species known as the endosymbiont lives within the body of a larger species known as the host.

A

Endosymbiosis

Phagocytosis provides away for protist cells that function as hosts to take in prokaryotic or eukaryotic cells that function as endosymbionts.

Such endosymbiotic cells confer valuable traits and are not digested. Endosymbiosis has played a particularly important role in protist evolution.

For example, early in protist history, endosymbiotic bacterial cells gave rise to mitochondria, the organelles that are the major site of ATP synthesis in most eukaryotic cells.

Consequently, most protists possess mitochondria, though these may be highly modified insome species.

34
Q

What are the three protist groups classified within the supergroup, Excavata?

A

Euglenoids, Kinetoplastids, and Metamonads

35
Q

What members of Excavata possess unique, interlocking, ribbon-like protein strips just beneath their plasma membranes?

A

Euglenoids

These strips make the surfaces of some euglenoids so flexible that they can crawl through mud.

Many euglenoids are colorless and heterotrophic, but Euglena and some other genera possess green plastids and are photosynthetic.

36
Q

What exactly are plastids? And how did do some excavata, like euglenoids, acquire them?

A

Plastids are organelles in plant and algal cells that are distinguished by their synthetic abilities and that were acquired via endosymbiosis.

Many euglenoids possess a light-sensing system that includes a conspicuous red structure known as an eyespot, or stigma, and light-detecting molecules located in a swollen region at the base of a flagellum.

These structures enable green euglenoids to detect light environments that are optimal for photosynthesis.

Most euglenoids produce conspicuous carbohydrate-storage particles that are held in the cytoplasm.

37
Q

What heterotrophic protists are named for a large mass of DNA known as a kinetoplast that occurs in their single large mitochondrion?

A

Informally known as kinetoplastids (formally Kinetoplastea)

These protists lack plastids, but they do possess an unusual modified peroxisome in which glycolysis takes place, known as a glycosome. (Recall that in most eukaryotes, glycolysis occurs in the cytosol.)

38
Q

Bonus! What is a peroxisome?

How are they different from lysosomes?

Since Kinetoplastids have an unusual modified peroxisome in which glycolysis takes place, known as a glycosome, what is its role?

A

Peroxisomes are organelles that sequester diverse oxidative reactions and play important roles in metabolism, reactive oxygen species detoxification, and signaling.

Lysosomes contain hydrolase. This is the component or enzyme that is responsible for digestion. Peroxisomes, on the other hand, contain three oxidative enzymes such as catalase, D-amino acid oxidase, and uric acid oxidase.

Basically, Lysosomes are responsible for the digestion of cells while peroxisomes are responsible for the protection of cells against hydrogen peroxide.

The glycosome is a host of the main glycolytic enzymes in the pathway for glycolysis. This pathway is used to break down fatty acids for their carbon and energy.

39
Q

What are heterotrophic flagellates, where some are parasitic species that attack the cells of animal hosts and absorb food molecules released from them?

How do these two parasitic protists differ in how they are transmitted from one human host to another?

A

Metamonads

Trichomonas vaginalis and Giardia intestinalis.

These specialized heterotrophic flagellates use flagella to disperse across the surfaces of moist host tissues; the flagellates then absorb nutrients from living cells.

The intestinal parasite Giardia intestinalis is transmitted from one person to another via fecal wastes, whereas the urogenital parasite Trichomonas vaginalis can be transmitted by sexual activity.

40
Q

What is a parasitic protist, that contains two active nuclei and produces eight flagella, that causes giardiasis, an intestinal infection that can result from drinking untreated water or from unsanitary conditions in day-care centers?

A

G. intestinalis

Nearly 300 million human infections occur every year, and the disease also harms young farm animals, dogs, cats, and wild animals.

In the animal body, flagellate cells cause disease and also produce infectious stages known as cysts that are transmitted infeces and can survive several weeks outside a host.

When an animal ingests as few as 10 of these cysts, within 15 minutes stomach acids induce the flagellate stage to develop and adhere to cells of the small intestine.

T. vaginalis and G. intestinalis were once thought to lack mitochondria, but they are now known to possess simple structures that are highly modified mitochondria.

41
Q

How have T. vaginalis and G. intestinalis genomes been powerfully affected?

A

One common feature is that horizontal gene transfer from bacterial or archaeal donors has powerfully affected both genomes.

About 100 G. intestinalis genes are likely to have been acquired via horizontal gene transfer. In T. vaginalis, more than 150 cases of likely horizontal gene transfer were identified, with most transferred genes encoding metabolic enzymes such as those involved in carbohydrate or protein metabolism.

42
Q

What supergroup includes land plants (aka the kingdom, Plantae) but also encompasses several protist phyla where the land plants evolved from green algal ancestors

A

The supergroup is called “Land plants and relatives” …… ok?

Together, plants and some closely related
green algae form the clade Streptophyta, informally known as streptophytes, whereas most green algae are classified in the phylum Chlorophyta

The red algae, classified in the phylum Rhodophyta, are also regarded as close relatives of green algae and land plants.

43
Q

For the supergroup land plants and relatives, multicellularity first rose in what closely related algae?

And which primary plastids in this supergroup are macroalgae in which multicellularity arose independently?

A

Streptophyte algae phylum first arose in multicelluarity giving rise to the eventual kingdom plantae.

Chlorophyte phylum and red algae (Rhodophyta phylum) arose independent within multicellularity.

44
Q

Where do diverse structural types of green algae occur?

A

Fresh water, the ocean, and on land or ice surfaces.

Most of the green algae are photosynthetic, and their cells contain the same types of plastids and photosynthetic pigments that are present in land plants.

Some green algae are responsible for harmful algal growths, but others are useful as food for aquatic animals, as model organisms, and as sources of renewable oil supplies. Many green algae possess flagella or the ability to produce them during the development of reproductive cells.

45
Q

Why are green algae increasingly important in medicine?

A

Because they produce channel rhodopsins, light-activated ion channels.

Green algae use these channel proteins to detect and respond to light, and researchers are studying the proteins in an attempt to understand and possibly treat blindness in animals.

46
Q

T/F Most species of protists known as red algae are multicellular land macroalgae.

A

False. Most are multicelluar marine macroalgae.

The red appearance of these algae is caused by the presence of distinctive photosynthetic pigments that are absent from green algae and land plants.

Red algae characteristically lack flagella—a feature that has strongly influenced the evolution of this group, resulting in unusually complex life cycles

47
Q

Why are the life cycles of red algae important to humans?

A

These life cycles are important to humans because red algae are cultivated in ocean waters for the production of billions of dollars worth of food or industrial and scientific materials yearly.

For example, the sushi wrappers called nori are composed of the sheetlike red algal genus
Porphyra, which is grown in ocean farms.

Carrageenan, agar, and agarose are complex polysaccharides that are extracted from red algae and are essential to the food industry and in biology laboratories for cultivating microorganisms and working with DNA.

48
Q

What is a plastid that originated from a prokaryote as the result of primary endosymbiosis?

A

Primary plastid

The plastids of red algae resemble those of green algae and land plants (and differ from those of most other algae) in having an enclosing envelope composed of two membranes.

49
Q

What is the process by which a eukaryotic host cell acquires prokaryotic endosymbionts?

Mitochondria and the plastids of green and red algae are examples of organelles that originated via this term.

A

Primary endosymbiosis

During primary endosymbiosis, heterotrophic host cells captured cyanobacterial cells via phagocytosis but did not digest them.

These endosymbiotic cyanobacteria provided host cells with photosynthetic capability and other useful biochemical pathways and eventually evolved into primary plastids.

50
Q

What are the differences between primary, secondary, and tertiary endosymbiosis?

Just include their very identifiable characteristics!

A

Primary endosymbiosis - involves the acquisition of a cyanobacterial endosymbiont by a host cell without a plastid. Envelope of 2 membranes.

Secondary endosymbiosis - involves the acquisition by a host cell of a eukaryotic endosymbiont that contains one or more primary plastids. Envelope of more than 2 membranes.

Tertiary endosymbiosis - involves the acquisition by a host cell of a eukaryotic endosymbiont that possesses secondary plastids. Multiple membranes (much more than 2)

51
Q

During the evolution of a primary plastid, what happens to the bacterial cell? Primary endosymbiosis.

A

The wall of the cell is lost, and most endosymbionit genes are transferred to the host nucleus.

52
Q

During the evolution of a secondary plastid, what happens eukaryotic endosymbionit? Secondary endosymbiosis.

A

Most components of the endosymbiont cell are lost, but a plastid is often retained within an envelope of endoplasmic reticulum.

53
Q

T/F All cells of plants, green algae, and red algae contain one or more plastids, and most of these
organisms are photosynthetic.

A

True.

However, some species (or some of the cells within the multicellular bodies of photosynthetic species) are heterotrophic because photosynthetic pigments are not produced in the plastids.

In these cases, plastids play other essential metabolic roles, such as producing amino acids and fatty acids.

54
Q

Review: What are secondary plastids? This is, typically, for most other photosynthetic protists and not the plants and green and red algae.

A

A plastid that has originated by the endosymbiotic incorporation of a eukaryotic cell containing a primary plastid into a eukaryotic host cell.

The process, secondary endosymbiosis, a process that occurs when a eukaryotic host cell acquires a eukaryotic endosymbiont having a primary plastid.

55
Q

Why do secondary plastids have more than two membranes?

A

Because such eukaryotic endosymbionts are often enclosed by the endoplasmic reticulum (ER).

56
Q

What are two algal phyla that include single-celled flagellates whose plastids originated by secondary endosymbiosis involving the incorporation of plastids derived from a red algae?

A

Cryptomonads and hatophytes.

Occurring in marine and fresh waters, cryptomonads are excellent sources of the fatty-acid-rich food essential to aquatic animals.

Haptophytes are primarily unicellular marine photosynthesizers; somehave flagella and others do not. Some haptophytes are known as the coccolithophorids because they produce a covering of intricate white calcium carbonate discs known as coccoliths.

57
Q

What often forms massive ocean growths that are visible from space and play important roles in Earth’s climate by reflecting sunlight?

A

Coccolithophorids

In some places, coccoliths produced by huge populations of ancient coccolithophorids accumulated on the ocean floor, together with the calcium carbonate remains of other protists, for millions
of years.

These deposits were later raised above sea level, forming massive limestone formations or chalk cliffs such as those visible at Dover, on the southern coast of England.

58
Q

What three supergroups seem to be closely related, based on recent phylogenetic studies and have plastids acquired by secondary endosymbiosis or, in some cases, by tertiary endosymbiosis?

A

Alveolata, Stramenopila, and Rhizaria.

59
Q

What three important phyla does the supergroup Alveolata contain?

A

Ciliophora, or ciliates

Apicomplexa, a medically important group of parasites (contains the malarial agent Plasmodium)

Dinozoa, known as dinoflagellates

60
Q

How are dinoflagellates recognized? (2)

A

Dinoflagellates are recognized both for their mutualistic relationship with reef-building corals and for the harmful blooms (red tides) that some species produce.

61
Q

Why is the supergroup Alveolata named the way it is?

A

The supergroup Alveolata is named for saclike membranous vesicles known as alveoli that are present at the cell periphery in all of these phyla

62
Q

Where do alveoli lie?

A

Beneath the plasma membrane of a dinoflagellate, along with defensive projectiles, called extrusomes, that are ready for discharge.

63
Q

While some alveoli of some dinoflagellates seem empty, giving the cell surface a smooth appearence, what do some contain which forms an armor-like enclosure?

A

Plates of cellulose

64
Q

How many of the different species of dinoflagellates are heterotrophic and how many possess photosynthetic plastids that orginated by secondary or tertiary endosymbiosis?

A

About half and half of all species of dinoflagelletes.

65
Q

What supergroup encompasses a wide range of algae, protozoa, and fungus-like protists that usually produce flagellate cells at some point in their lives?

This means straw hair in greek.

A

Stramenopila (referred to as the stramenopiles)

Named for distinctive strawlike hairs that occur on the surfaces of flagella of these protists.

These flagellar hairs function something like oars to greatly increase swimming efficiency. Stramenopiles are also known as heterokonts (from the Greek, meaning different flagella), because the two flagella often present on swimming cells have slightly different structures.

One notable Stramenopile includes the fungus-like protist Phytophthora infestans, which causes the serious potato disease known as late blight.

P. infestansis responsible for an estimated $7 billion in crop losses every year.

Photosynthetic stramenopiles include diatoms (Bacillariophyceae), whose glasslike silicate cell walls are elaborately ornamented with pores, lines, and other intricate features

66
Q

What is mined for use in reflective paint and other industrial products?

A

Ancient diatoms or diatomaceous earth.

Recent genome sequencing projects have focused on the processes by which diatoms produce their detailed silicate structures; understanding of these processes may prove useful in industrial microfabrication applications.

BONUS!
SEM of the silicate cell wall of the common diatom
Cyclotella meneghiniana, showing elaborate ornamentation of the structure. The many pores in the colorless silicate wall lighten the cell, helping to keep it afloat in the water.

Forests of giant kelps occur along many ocean shores, providing habitat for diverse organisms.

67
Q

Several groups of flagellates and amoebae that have thin, hairlike extensions of their cytoplasm—known as filose pseudopodia—are classified in what supergroup?

A

Rhizaria (from the Greek rhiza, meaning root)

68
Q

Rhizaria includes the phylum Chlorarachniophyta, that have what type of shaped cells that possess secondary plastids obtained from green algae?

A

Spider-shaped cells

69
Q

What are the Radiolaria and Foraminifera phylas of Rhizaria that produce exquisite mineral shells?

A

Ocean plankton!

Fossil shells of foraminiferans are widely used to infer past climatic conditions, because ratios of stable oxygen isotopes contained in the shells can be analyzed to reconstruct past water temperatures.

70
Q

How does the supergroup Amoebozoa, including many types of amoebae, move by extension of?

A

Pseudopodia

71
Q

What type of protists in the supergroup Amoebozoa is widely used as a model organism for understanding movement, communication among cells, and development?

A

Slime molds

In response to starvation, large numbers of
Dictyostelium amoebae aggregate into a multicellular slug that produces a cellulose-stalked structure containing many single-celled, asexual spores.

Infavorable conditions, these spores produce new amoebae, which feed on bacteria. A recent study revealed that some Dictyostelium
clones carry favored bacterial food through these reproductive stages, showing a simple “farming” behavior.

72
Q

What is included in the supergroup Opisthokonta?

A

Animal, fungal kingoms, and related protists.

73
Q

How did the supergroup Opisthokonta get its name?

A

This supergroup is named for the presence of a single posterior flagellum on swimming cells.

Nuclearia is a protist genus that feeds by phagocytosis and seems particularly closely related to the kingdom Fungi.

74
Q

What are the 125 species of protists, located within the supergroup Opisthokonta, that are single-celled or colonial protists featuring a distinctive collar surrounding the single flagellum?

This collar is made of cytoplasmic extensions that filter bacterial food from water currents generated by flagellar motion.

A

Choanoflagellates (CO-ANO-FLAGELLATES)

75
Q

What supergroup with its respective phylum is believed to represent the closest living relative of animals?

A

Choanoflagellates

Genomic studies have revealed genes that encode cell adhesion and extracellular matrix proteins. Such proteins help choanoflagellates attach to surfaces and were also essential to the evolution of multicellularity in animals.

The choanofl agellate genome also encodes the p53 protein, a regulatory transcription factor that plays essential roles in the animal cell cycle, cancer, and reproduction.