Fungal cell walls are built largely from chitin, a tough nitrogen-containing polysaccharide that also forms insect exoskeletons.
Missing Word
chitin
Chitin is a strong polysaccharide containing nitrogen. It stiffens fungal cell walls in place of the cellulose that plants use, and it is the same material found in insect exoskeletons.
Category: Fungal Biology
Question 2
In most fungi, cross walls called septa divide the hyphae into separate cells that are linked by pores.
Missing Word
septa
Septa are the internal cross walls of fungal hyphae. Their pores let cytoplasm and nutrients pass between neighboring cells, while fungi lacking septa have one continuous multinucleate hypha.
Category: Fungal Biology
Question 3
Fungi store excess carbohydrate as glycogen, the same storage polysaccharide used by animals rather than the starch used by plants.
Missing Word
glycogen
Glycogen is a highly branched polymer of glucose. Fungi and animals both store energy this way, one of several traits that reflect their close evolutionary relationship.
Category: Fungal Biology
Question 4
Eating rye infected by the fungus Claviceps purpurea can cause ergotism, a disease marked by convulsions, hallucinations, and gangrene.
Missing Word
ergotism
Ergotism is poisoning by alkaloids that Claviceps purpurea produces in infected cereal grains. One of these compounds, lysergic acid, is a chemical precursor of LSD.
Category: Microbes and Disease
Question 5
An opportunistic infection is one that takes hold when a person's immune defenses are weakened, as in late-stage AIDS.
Missing Word
opportunistic
Opportunistic infections are caused by organisms, including fungi such as Pneumocystis and Candida, that rarely sicken healthy people but take advantage of a weakened immune system.
Category: Microbes and Disease
Question 6
Malaria is caused by Plasmodium, a single-celled apicomplexan parasite carried by Anopheles mosquitoes.
Missing Word
Plasmodium
Plasmodium is the genus of apicomplexan parasites that cause malaria. Its life cycle requires both a mosquito and a vertebrate host, and in humans it infects liver cells and then red blood cells.
Category: Microbes and Disease
Question 7
A zoonosis is any infectious disease that is transmitted from animals to humans.
Missing Word
zoonosis
A zoonosis is a disease that passes from animals to people. Plague, carried by rodents and their fleas, is a classic example.
Category: Microbes and Disease
Question 8
Chloroplasts are thought to descend from a cyanobacterium that was engulfed by an early eukaryotic cell that already had mitochondria.
Missing Word
cyanobacterium
A cyanobacterium is a photosynthetic bacterium. Chloroplasts resemble cyanobacteria in size, membranes, circular DNA, and division, supporting their origin by endosymbiosis.
Category: Endosymbiosis and Early Life
Question 9
The inner membrane of a mitochondrion is folded into cristae, which resemble the surface membranes of certain bacteria.
Missing Word
cristae
Cristae are the folds of the inner mitochondrial membrane. Their resemblance to bacterial membranes is one piece of evidence that mitochondria began as engulfed bacteria.
Category: Endosymbiosis and Early Life
Question 10
Stromatolites are layered rock structures built by mats of photosynthetic prokaryotes that trap sediment, and fossil examples date back billions of years.
Missing Word
Stromatolites
Stromatolites form as microbial mats grow upward and bind layers of sediment. Fossil stromatolites are among the oldest evidence of life on Earth, and living ones still form today in a few places.
Category: Endosymbiosis and Early Life
Question 11
In an amoeba, a food vacuole fuses with a lysosome, whose digestive enzymes break down the engulfed food.
Missing Word
lysosome
A lysosome is a membrane-bound organelle filled with digestive enzymes. When it merges with a food vacuole formed by phagocytosis, its enzymes digest the contents, and leftover wastes leave the cell by exocytosis.
Category: Protist Biology
Question 12
Single-celled eukaryotes such as Euglena are covered by a pellicle, a flexible layer of interlocking protein strips beneath the plasma membrane.
Missing Word
pellicle
A pellicle is a supportive but flexible covering made of protein strips. It lets cells such as Euglena keep their shape while still changing it slightly as they move.
Category: Protist Biology
Question 13
Diatoms are single-celled photosynthetic algae enclosed in glassy cell walls made of silica.
Missing Word
Diatoms
Diatoms are photosynthetic stramenopiles whose two-part walls are made of silica. They are major primary producers in oceans and fresh water.
Category: Protist Biology
Question 14
Dinoflagellates called zooxanthellae live inside the tissues of reef-building corals and supply the coral with most of its energy.
Missing Word
zooxanthellae
Zooxanthellae are photosynthetic dinoflagellate symbionts. The coral gives them shelter and nutrients, and they give the coral sugars, which is why reef corals depend on light.
Category: Protist Biology
Question 15
Protist is an informal term for any eukaryote that is not an animal, a plant, or a fungus.
Missing Word
Protist
Protist is a catchall name for a very diverse set of eukaryotes. Molecular data show that some protists are more closely related to animals, plants, or fungi than to each other, so the old kingdom Protista is no longer a formal group.
Category: Protist Biology