Chapter 28: Protists (Part 1, Week 5) Flashcards
T/F Protists are eukaryotes, live in most habitats, and are mostly microscopic in size.
True
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?
Algae
What is the oil that fuels our cars and industries derived from that accumalted on the ocean floor over millions of years?
Pressure-cooked algae!
Today, algae are being engineered into systems for cleaning pollutants from water or air and for producing renewable biofuels.
T/F Protists also include some parasites that cause serious human illnesses.
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.
[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?
Protos
Protists are eukaryotes that are not classified in the plant, animal, or fungal kingdoms.
What are the two common charateristics that protists display?
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.
What are the three major ecological types that protists occur in?
Algae, protozoa, and fungus-like protists
What is a term that applies to about 10 phyla of protists, including mostly photosynthetic and some nonphotosynthetic species; often also includes cyanobacteria?
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.
Why are algae increasingly important sources of renewable biofuels?
Thanks to their photosynthetic abilities.
Despite the general feature of photosynthesis, algae do not form a monophyletic group descended from a single common ancestor.
What is a term commonly used to describe diverse heterotrophic protists?
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.
What process does Ciliates use to ingest diatoms, a golden-pigmented oil-rich, silica walled algal cells?
By the process of phagocytosis
What are heterotrophic protists that often resemble true fungi in having threadlike, filamentous bodies and absorbing nutrients from their environment?
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.
Even though protists occupy nearly every type of moist habitat, they are particularily common and diverse in?
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.
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.
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.
What are communities of microorganisms that are attached by mucilage to underwater surfaces such as rocks, sand, and plants?
Periphyton
Because sinking is not a problem for attached protists, these often produce multicellular bodies, such as branched filaments
What are photosynthetic protists that can be seen with the unaided eye; also known as seaweeds?
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.
What are the major types of protist movements? (3)
Swimming by means of flagella or cilia.
Amoeboid movement
Gliding
Explain what flagella are that many types of photosynthetic and heterotrophic protists use to swim?
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.
What are flagellates typically composed of in cells and size? Also, why are flagellates typically the size they are?
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.
T/F Some flagellate protists are sedentary.
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
What are cilia?
Tiny hairlike extensions on the outsides of cells.
Cilia are structurally similar to eukaryotic flagella but are shorter and more abundant.
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?
Ciliates
Having many cilia allows ciliates to achieve larger sizes than flagellates yet still remain buoyant in water.
What is the third type of movement which is a kind of motion that involves extending cytoplasm into lobes, known as pseudopodia?
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.
What is a protist that moves by pseudopodia, which involves extending cytoplasm into filaments or lobes?
Amoeba (plural, amoebae)
[Start 28.2 Evolution and Relationships]
T/F Protists do not form a paraphyletic group.
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.
What analyses in modern phylogenetics are based on to identify that protists are classified as paraphyletic groups? (2)
Comparisons of DNA sequences and cellular features.
What are one of the seven subdivisions of the domain Eukarya where many protist phyla can be classified within?
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.
How does the study of such protists (in supergroups) help?
Reveals how multicellularity originated in animals, fungi, and plants.
What protist supergroup originated very early among eukaryotes, and is important in understanding the early evolution of eukaryotes?
Excavata
Many of the Excavata feed by ingesting small particles of food in their aquatic habitats.
When food particles are collected within the feeding groove, they are then taken into cells by a type of endocytosis called?
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.
