Eukaryote

Question 1

Bacteria v. Eukarya

Answer 1

1. absence (prokaryote) or presence (eukaryote) of a nucleus is the defining characteristic
2. Cell wall is always composed of carbohydrates, in bacteria peptidoglycan, in plants cellulose, Fungi chitin
3. Having organelles is a defining features of eukarya, rare in bacteria

Question 2

Defining characteristics of Animals v., Protozoa v., Fungi

Answer 2

Animals

• Cellularity: Multicellular
• Reproduction: Sexual or Asexual
• Membrane Sterol: Cholesterol
• Cell Wall: No
• Organ Systems: Yes -> defining characteristic

Protozoa
- Cellularity: Unicellular
- Reproduction: Asexual or Sexual
- Membrane Sterol: cholesterol is the dominant sterol
- Cell Wall: No
- Organ Systems: No

Fungi
- Cellularity: Unicellular or Multicellular. Unicellular fungi → Yeast. Multicellular fungi → Mold
- Reproduction: Asexual or Sexual
- Membrane Sterol: Ergosterol (targeted by antifungal drugs)
- Cell Wall: Yes
- Organ Systems: No

Question 3

Example Animal Microorganisms

Answer 3

All Helminths (worms)
la lombriz

1. Ascaris lumbricoides
   - Type: Nematode (roundworm)
   - Disease: Ascariasis (intestinal obstruction)
2. Enterobius vermicularis
   - Type: Nematode (pinworm)
   - Disease: Pinworm infection (perianal itching, especially in children)
3. Necator americanus
   - el anquilostoma
   - Type: Nematode (hookworm)
   - Disease: Hookworm infection (anemia, fatigue)
4. Taenia solium
   - la solitaria / la tenia
   - Type: Cestode (tapeworm)
   - Disease: Taeniasis (intestinal), Cysticercosis (brain/organ infection from larvae)

Question 4

Characteristics of Helminths

Answer 4

Las lombriz
- Posses multiple organ systems, but not all species have all systems, somes species are missing some systems or have a very simplified system -> can be a distinguishing characteristic between species
- Life cycles vary between simple to complex
- Less common and less problematic in temperate regions

Reproductions
Sexual reproduction common:
Dioecious: Male and female organs in separate individuals -> the species has a male and female sex
Monoecious: Male and female organs in the same individual -> tapeworm

Some organisms can undergo asexual reproduction during certain lifestages

Question 5

Asexual vs Sexual reproduction

Answer 5

Sexual Reproduction:
- involves two gametes: sperm and egg
- Offspring are genetically diverse
- Requires fertilization
- Occurs in both dioecious and monoecious organisms

Asexual Reproduction
- Offspring are genetically identical (clones) of parent
- No gametes or fertilization involved

Question 6

Characteristics of Roundworms

Answer 6

Nematodes
1. Fully intact digestive system -> mouth to anus
2. Dioecious -> separate male and female worms

Examples
1. Ascaris lumbricoides → Ascariasis
2. Enterobius vermicularis → Pinworm, Enterobiasis (most common in U.S.)
3. Necator americanus → Hookworm, Necatoriasis -> endemic to the SE US. Can make you lethargic, may have contributed to our stereotypes of southerners. Infect barefoot individuals by biting and entering through foot.

Question 7

General Characteristics of Tapeworms

Answer 7

Cestodes
1. Lack digestive system
2. Monoecious

Example
1. Taenia solium -> pork tapeworm -> pork intermediate species
- Common in: Areas where undercooked pork is eaten
- Disease: Taeniasis (intestinal tapeworm)
- Cysticercosis (larvae can invade human tissues — can be severe, especially in the brain)

2. Taenia saginata -> beef tapeworm -> beef intermediate species
   - More common than T. solium in many regions
   - Disease: Only causes taeniasis (intestinal infection, generally milder)
   - No cysticercosis risk (does not form larval cysts in humans)

Question 8

Physical characteristic of tapeworm

Answer 8

strobila
- body of tapeworm
- Long, flat, ribbon-like structure
- Can grow to meters in length

proglottids
- repeating segments that constitute body
- Older proglottids are larger and located at the tail end
- New segments are added at the scolex end
- Each mature proglottid contains both male and female reproductive organs → tapeworms are monoecious.
- Once fertilized, proglottids become gravid (filled with eggs), break off, and exit via the host’s feces to continue the cycle.

Scolex
- Specialized attachment structure at one end
- Has hooks (made of hardened chitin-like material) and suckers (muscular structures for attachment)
- Function: Attaches to intestinal wall and resists peristalsis
- Marks the youngest part of the tapeworm

Question 9

Describe Taenia solium / Taenia saginata lifecycle

Answer 9

1. Eggs released
   Humans (definitive host) pass eggs or gravid proglottids in feces.
   Contaminate the environment (soil, water, vegetation).
2. Intermediate host ingests eggs
   Pigs / cows (intermediate host) eat contaminated food or water.
   Eggs hatch into oncospheres inside the pig’s / cow’s intestine.
3. Larvae migrate
   Oncospheres penetrate the intestinal wall.
   Travel via blood to muscles, where they develop into cysticerci (larval cysts).
4. Humans ingest cysticerci
   Eating undercooked or raw pork with cysticerci infects humans.
   Larvae evaginate in the small intestine.
5. Scolex attaches
   The scolex (head) of the tapeworm attaches to the intestinal wall.
   Matures into an adult worm.
6. Adult worm develops
   Grows in the small intestine, producing proglottids that generate new eggs.
   Cycle continues when eggs are excreted again.

Humans = Definitive host (host adult worm)

Pigs = Intermediate host  for Taenia solium -> risk of cysticercosis 

Cows = Intermediate hosts for Taenia saginata -> no risk of cysticercosis

Question 10

Diseases of Taenia solium

Answer 10

1. Taeniasis - most common
   - Humans are the definitive host
   - caused by ingestion of tapeworm larva (cysticerci) in muscle tissue of food animal
   - the mature tapeworm lives in the gut
   - Symptoms: Often mild or asymptomatic; may include abdominal discomfort, nausea, or visible proglottids in stool.
   - easily treatable
2. Cysticercosis
   - Humans as accidental intermediate host
   - Caused by ingestion of tapeworm eggs
   - Cysticerci live in human tissue
   - Symptoms: Depends on location; may involve muscle nodules, pain, or skin lumps.
   - treatable
   - Long-term effects: May cause scarring or calcified cysts in tissue.
3. Neurocysticercosis
   - Cysticercosis of the brain
   - symptoms: Seizures, headaches, neurological deficits
   - seizures may persist long-term, brain scarring or damage can be permanent

Question 11

Protozoa

Answer 11

• unicellular
• non-photosynthetic
• motile - Flagella, cilia, or pseudopodia -> the majority of protozoa are mobile during trophozoite stage. Cysts are typically non-motile. Historically motility was used to classify (ex/ flagellates -> flagella, ciliates -> cilia, amoeboids -> pseudopodia, apicomplexans -> gliding (non-motile forms)
• Organelles may be unique, modified, or missing (diverse adaptations)
• Reproduction: Can be asexual, sexual, or both, Some species have separate sexual and asexual life cycles
• Lifecycles may be complex with asexual and sexual reproductive steps and multiple hosts

Question 12

Life stages of Protozoa

Answer 12

1. Trophozoite
   - stage that occurs in ALL protozoa
   - Vegetative form: organisms are metabolically and reproductively active, are motile. During this stage they feed, grow, and reproduce
2. Cyst
   - Not found in all protozoa
   - a dormant state
   - cysts have a higher (outside the host) resistance compared to trophozoite

Question 13

Motility types protozoa

Answer 13

1. Cilia
   - Structure: Many short, hair-like projections covering the cell
   - Movement: Coordinated beating of cilia propels the organism through liquid. Movement is fast and smooth
2. Pseudopodia
   - Structure: Extensions of cytoplasm called pseudopods (“false feet”)
   - Movement: Crawling motion by flowing cytoplasm (amoeboid movement). Movement is flexible, slow, shape-shifting
3. Flagella
   - Structure: One or a few long, whip-like appendages
   - Movement: Rotational or whip-like motion of the flagellum pulls the cell forward

Motility is closely linked to life cycle stage and function -> trophozoites are usually the motile form

Question 14

Example groups of protozoa

Answer 14

Candida albicans

Question 15

Lifecycle toxoplasma gondii

Answer 15

• Definitive host: Cats
  
  • Ingest infected prey with tissue cysts
  • Cysts release bradyzoites, which become trophozoites in the intestinal epithelium
  • Trophozoites multiply and undergo sexual reproduction
  • Produce and shed oocysts in feces
  • Oocysts become infectious in the environment (1–5 days)
  • Intermediate hosts: Humans, rodents, birds
    
    • Ingest infectious oocysts from contaminated food, water, or soil
    • Oocysts release active form (trophozoites), which spread through the body
    • Trophozoites eventually form cysts in tissues (especially brain, eyes, muscles)
  • Cycle continues: Cats are reinfected by eating animals with tissue cysts
  • Reinfection of cats: Occurs by consuming intermediate hosts with tissue cysts, restarting the cycle

Changes in infected rodent behavior
1. Infected rodents lose their fear of cat urine.
2. Some show increased attraction to cat scent.
3. This increases their chance of being eaten by cats → completing the parasite’s life cycle.

Apicomplexa

Question 16

Lifecycle Cryptosporidium parvum

state disease caused

Answer 16

Cryptosporidiosis

1. Thick-walled oocyst is ingested

Found in contaminated water, food, or recreational water

2. Oocyst reaches small intestine
   Releases sporozoites, which invade intestinal epithelial cells

3a. Asexual reproduction (merogony)
Sporozoites replicate as merozoites
Some reinfect nearby cells → auto-infection, maintains infection in host

3b. Sexual reproduction (gametogony)
Merozoites differentiate into male and female gametes
Fuse to form a zygote
Zygote develops into thick and thing wall oocysts

• Thick-walled oocysts: excreted in feces → transmission to new hosts
• Thin-walled oocysts: remain in host -> burst within the same host and release sporozoites -> cause auto-infection

Asexual reproduction
results in reinfection - Infection persists in current host through auto-infection

Sexual reproduction
- results in transmission - new host become infected by ingesting thick walled oocysts
- results in reinfection - thin walled oocysts burst releasing sporozoites which infect nearby cells

Apicomplexa

Question 17

Describe Giardia duodenalis

Answer 17

• Flagellated protozoan
• Trophozoite stage: active / symptomatic stage. Trophozoite stage only seen within the host
• Cyst stage: infective stage
• Most common intestinal parasite in the US

Structure:
- Has an adhesive disc on the ventral surface which helps the parasite attach to the host’s intestinal lining
- Motile via flagella
- Flagella also generate a vacuum between the parasite and the host
- No true mitochondria -> exclusively uses anaerobic metabolism
- Contains mitosomes -> Evolved from mitochondria -> Do not produce ATP -> Used in protein maturation
- Contains two nuclei (symmetrically arranged)

Question 18

Lifecycle Giardia

Answer 18

1. Encystment occurs in the large intestine of host
   Trophozoites form protective cysts before being passed in stool
2. Cysts and trophozoites are released in feces
   Only cysts survive outside the host
   Trophozoites perish quickly in the environment
3. Cysts persist in the environment
   Especially in cool, moist, rainy conditions (e.g., soil, water, surfaces)
   Can survive for long periods
4. Cyst is ingested by a new host
   Often via contaminated water, food, hands, or surfaces
5. Excystment occurs after cyst passes through the stomach -> Releases trophozoites, which attach to intestinal lining and reproduce

Question 19

Defining characteristics of Fungi

Answer 19

Eukaryotic organisms that may be unicellular (yeasts) or multicellular (molds)

Distinguishing features:
1. Cell wall primarily composed of chitin. May contain other carbohydrates such as β-glucans
2. Normally saprophytic
3. Use Aerobic respiration and/or fermentation to produce ATP
4. Are hapload for the majority of life-cycle
5. Most fungi can reproduce both sexually and asexually. Asexual is generally more common.
- Asexual Reproduction: Budding small daughter cell forms from the parent, enlarges, and detaches releasing a spore. This leaves a *bud scar** on the parent cell
- Sexual reproduction: Two haploid cells of different mating types fuse -> diploid cell -> meiosis -> produce haploid spore.

Saprophytic organisms obtain nutrients by decomposing dead or decaying organic matter.

saprophytic fungi a key role in nutrient recycling, breaking down complex organic material and returning elements like carbon and nitrogen to the ecosystem.

Question 20

Name of Fungal diseases

Answer 20

Mycosis refers to any disease caused by fungal infection, ranging from superficial (e.g., ringworm) to systemic (e.g., cryptococcosis).

mycoses -> plural

mycosis -> singular

Question 21

Describe Yeast Morphology

Answer 21

• unicellular
• Cells are typically oval to round
• Yeasts do not form hyphae, distinguishing them from molds
• Yeasts most commonly reproduce asexually in a process called budding.

Question 22

Describe Mold Morphology

Answer 22

• multicellular
• long tubular filaments of interconnected cells called hyphae (hypha singular). Hyphae often give mold its “fuzzy” appearance.
• Mass of hyphae is called a mycelium

Question 23

Dimorphic Fungi

Answer 23

• can grow as either mold or yeast, depending on environmental temperature
• Grow as mold outside human host (cooler temps)
• Convert to yeasthen inside the human host (at 37°C)
• Yeast form is associated with invasion and dissemination in the body
• Dimorphism is a COMMON trait of primary (true) pathogens — fungi that can cause disease in healthy individuals
• Not typical of opportunistic pathogens, which require a compromised immune system

Question 24

Describe Coccidioides immitis

Answer 24

• Primary pathogen
• Dimorphic: mold in environment, spherule in host
• Causes coccidioidomycosis (Valley Fever)
• Found in dry soils, especially in Arizona and southern California
• Transmitted by inhalation of spores carried in dust
• Can cause pulmonary infection or disseminated disease
• Key Features:
  
  • No yeast phase: spherules are unique to Coccidioides
  • No human-to-human transmission
  • Classified as a primary pathogen

Question 25

**Cryptococcus neoformans**

Answer 25

Cryptococcosis is a fungal disease caused by *Cryptococcus neoformans*, often affecting immunocompromised individuals. It can cause pneumonia or spread to the brain (meningitis). **Cryptococcus neoformans** - *Type:* Dimorphic fungus - *Transmission:* Inhalation of spores from soil contaminated with bird droppings. - *Disease:* Causes cryptococcosis, which may begin as a lung infection and can spread to the central nervous system, causing **cryptococcal meningitis**, especially in immunocompromised individuals (e.g., AIDS patients). - *Key Features:* Has a thick **polysaccharide capsule** that helps it evade the immune system; detected with India ink staining. - **primary pathogen**

Question 26

**Trichophyton rubrum** - name diseases

Answer 26

- *Opportunistic pathogen* - **Dimorphic**: switches between **mycelial (filamentous)** and **yeast-like** forms depending on conditions - Mycelial form colonizes **keratinized tissues** (skin, nails) - Yeast-like form may aid in **penetration and immune evasion** - Causes **tinea infections** - Spread via **direct contact or fomites** - Grows in **moist, warm environments** - **Tinea pedis** → *Athlete’s foot* - **Tinea cruris** → *Jock itch* - **Tinea corporis** → *Ringworm of the body* - **Tinea capitis** → *Scalp ringworm* - **Tinea unguium** (also called **onychomycosis**) → *Nail fungus*

Question 27

**Candida auris**

Answer 27

- *Opportunistic pathogen* - **Not truly dimorphic**, but can form **aggregates** - Causes **invasive infections**, especially in healthcare settings -> **Nosocomial** - Notably **multidrug-resistant**, complicating treatment - Can **persist on surfaces**, leading to nosocomial outbreaks - Requires **specialized laboratory methods** for accurate identification

Question 28

**Candida albicans**

Answer 28

- *Opportunistic pathogen* - transitions between **yeast** and **hyphal** forms - Causes **candidiasis**, ranging from superficial to systemic infections - Part of normal **human microbiota**, but can overgrow when host defenses are compromised (dysbiosis) - **Hyphal form** is associated with tissue invasion and virulence - Typically **susceptible** to antifungals, but resistance can develop

Question 29

Amebic dysentery

Answer 29

- *Cause:* - Caused by the protozoan *Entamoeba histolytica* - Spread via ingestion of **cysts** in contaminated food or water (fecal-oral route) - *Life Cycle Summary:* 1. **Cysts** survive stomach acid → reach small intestine 2. Excystation releases **trophozoites** 3. Trophozoites migrate to **colon**, multiply, and form **ulcers** 4. Some trophozoites **encyst** and are shed in feces; others may enter bloodstream → liver → **liver abscess** 5. As a protozoan parasite, *E. histolytica* reproduces asexually through **binary fission**. - *Symptoms:* - **Bloody, mucus-filled diarrhea** - Abdominal cramping and pain - Possible fever and **liver tenderness** if extraintestinal spread occurs - *Name Breakdown:* - **Entamoeba** = “internal amoeba” (*enta* = within, *amoeba* = shape-shifting cell) - **Histolytica** = “tissue-destroying” (*histo* = tissue, *lytica* = lysis)

Question 30

Fungemia

Answer 30

Fungemia is the presence of fungi (usually *Candida*) in the bloodstream, a serious condition often seen in hospitalized or immunocompromised patients.

Question 31

Fungal vaginitis

Answer 31

Fungal vaginitis is a vaginal infection caused by *Candida species*, resulting in itching, discharge, and discomfort.

Question 32

Giardiasis

Answer 32

Giardiasis is a diarrheal illness caused by the protozoan *Giardia duodenalis*. - Spread via contaminated water, it involves both cyst and trophozoite stages.

Question 33

Histoplasmosis

Answer 33

Histoplasmosis is a fungal infection caused by *Histoplasma capsulatum*. Transmitted by inhalation of spores from bird or bat droppings. **Histoplasma capsulatum** - *Type:* Dimorphic fungus (mold in environment, yeast in tissue). - *Transmission:* Inhalation of microconidia from soil contaminated with bird or bat droppings, especially in river valleys (e.g., Ohio & Mississippi River). - *Disease:* Causes **histoplasmosis**, a respiratory infection that may resemble flu or pneumonia; can become disseminated in immunocompromised individuals. - *Key Features:* Converts to yeast form at body temperature; survives and multiplies inside **macrophages**.

Question 34

Malaria

Answer 34

Malaria is a protozoan disease caused by *Plasmodium* species, transmitted by *Anopheles mosquitoes*. It infects liver and red blood cells.

Question 35

Nosocomial infection

Answer 35

A nosocomial infection is acquired in a hospital setting, often caused by resistant pathogens like MRSA or *Candida auris*. hospital conditions allow opportunistic pathogens — microbes that don't usually cause disease in healthy individuals — to cause serious infection

Question 36

Onychomycosis

Answer 36

- *Definition:* Fungal infection of the nails (toenails or fingernails). - *Dermatophyte-caused:* - Most common cause (~80–90% of cases). - Caused by fungi like **Trichophyton rubrum**. - Affects **toenails more commonly**. - Invade keratinized tissue (skin, nails, hair). - *Candida-caused:* - Less common; a type of **yeast infection**. - More often affects **fingernails**, especially in those with frequent hand immersion or immunosuppression. - Caused by *Candida species* (e.g., *Candida albicans*). - *Note:* Both types require antifungal treatment, but identification helps guide appropriate therapy.

Question 37

Oral thrush

Answer 37

Oral thrush is a fungal infection of the mouth caused by *Candida albicans*; it appears as white plaques on the tongue and mucosa.

Question 38

Saprophyte

Answer 38

A saprophyte is an organism, usually a fungus or bacterium, that feeds on and decomposes dead organic matter.

Question 39

Toxoplasmosis

Answer 39

**Toxoplasmosis** - *Cause:* Caused by the protozoan parasite *Toxoplasma gondii*. - *Transmission:* - Ingestion of oocysts from **cat feces** (litter boxes, soil) - Ingestion of tissue cysts in **undercooked meat** - **Congenital transmission** (mother to fetus) - Rarely through organ transplant or blood transfusion - *Disease:* - Often **asymptomatic** in healthy individuals - Can cause **flu-like symptoms** (fever, lymphadenopathy, fatigue) - In **immunocompromised patients** (e.g., AIDS), it can cause **severe encephalitis** - In **pregnancy**, may lead to **congenital toxoplasmosis** (brain and eye damage in fetus) - *Key Features:* - Forms **tissue cysts** in brain, muscle, and other organs - Diagnosed via **serology** or PCR; visible on imaging in CNS infections - *Treatment:* - **Pyrimethamine + sulfadiazine + folinic acid** for active disease - No treatment needed for asymptomatic, immunocompetent individuals

Question 40

Trichomoniasis

Answer 40

**Trichomoniasis** - *Cause:* Caused by **Trichomonas vaginalis**, a flagellated protozoan parasite. - *Transmission:* **Sexually transmitted**; no cyst stage—transmitted as trophozoites. - *Disease:* - In **females**: Vaginal itching, frothy yellow-green discharge, burning, and discomfort during urination or intercourse. - In **males**: Often asymptomatic, but may cause urethritis or prostatitis. - *Key Features:* - Motile **trophozoite** stage visible in wet mount microscopy - Lacks a cyst stage - Confined to the **urogenital tract** - *Diagnosis:* Microscopy, antigen tests, or nucleic acid amplification (NAAT) - *Treatment:* **Metronidazole** or **tinidazole** (single dose), treat both partners to prevent reinfection

Question 41

Describe Naegleria fowleri

Answer 41

**Naegleria fowleri** - *Type:* **Free-living amoeboid protozoan** in the group Excavata - *Transmission:* Enters the body when **contaminated warm freshwater** (lakes, hot springs, poorly chlorinated pools) enters the **nose** during swimming or diving - *Life Cycle:* - Exists in **three forms**: cyst, trophozoite (infectious stage), and flagellated form - **Trophozoites** migrate along the olfactory nerve to the brain - *Disease:* - Causes **Primary Amebic Meningoencephalitis (PAM)** - Rapidly progressive and often fatal brain infection - Symptoms include headache, fever, stiff neck, confusion, and seizures - Disease progresses quickly, usually within days.

Question 42

Describe Entamoeba histolytica

Answer 42

**Entamoeba histolytica** - *Type:* **Protozoan parasite** in the group Amoebozoa - *Transmission:* **Fecal-oral route** via ingestion of mature cysts in contaminated food or water - *Life Cycle:* - Ingested **cysts** pass through the stomach and release **trophozoites** in the intestine - Trophozoites multiply and may invade the intestinal wall or spread via blood to the liver - Some trophozoites encyst and are passed in feces - *Disease:* - Causes **amebic dysentery** (bloody diarrhea, abdominal pain) - Can lead to **liver abscesses** and extraintestinal disease in severe cases

Question 43

Describe Giardia duodenalis

Answer 43

**Giardia duodenalis (also known as G. lamblia or G. intestinalis)** - *Type:* **Flagellated protozoan parasite** in the group Excavata - *Transmission:* **Fecal-oral route**, commonly through ingestion of cysts in contaminated water or food - *Life Cycle:* - Ingested **cysts** pass through the stomach and release **trophozoites** in the small intestine - Trophozoites attach to the intestinal wall with a ventral adhesive disc - Some trophozoites encyst before being passed in feces - Both **cysts** (infectious) and **trophozoites** (non-infectious) may be excreted - *Disease:* - Causes **giardiasis**, marked by **watery diarrhea**, gas, abdominal cramps, and **foul-smelling stools** - Does **not invade tissue**; symptoms result from malabsorption and inflammation of the intestinal lining

Question 44

Why is dimorphism adaptive for fungal pathogens?

Answer 44

- *Definition:* Dimorphic fungi can switch between **mold (mycelial) form in the environment** and **yeast form in host tissues** - *Adaptation Benefits:* - **Survival in diverse environments**: Mold form thrives at lower temperatures (soil), yeast form thrives at body temperature - **Tissue invasion:** Yeast form is better suited for spreading within host tissues - **Immune evasion:** Yeast form may avoid immune detection or resist phagocytosis - **Efficient transmission:** Mold form produces spores for dispersal in the environment - *Examples:* **Histoplasma capsulatum**, **Coccidioides immitis**, **Blastomyces dermatitidis**

Question 45

Describe Plasmodium falciparum

Answer 45

**Plasmodium falciparum** - *Type:* **Apicomplexan protozoan parasite** - *Transmission:* Transmitted by the bite of an infected **female Anopheles mosquito** - *Life Cycle:* - **Sporozoites** enter bloodstream, travel to liver, and infect hepatocytes - Multiply to form **merozoites**, which are released into the blood - Merozoites infect **red blood cells**, multiply, and cause RBC lysis - Some develop into **gametocytes**, which are taken up by a mosquito to continue the cycle - *Disease:* - Causes the **most severe form of malaria** - Symptoms include **cyclical fever**, chills, anemia, fatigue, and **cerebral malaria** in severe cases - Destroys red blood cells and can obstruct capillaries, especially in the brain, kidneys, and lungs

Question 46

Compare Excavata, Apicomplexans, and Amoebozoa

Answer 46

1. **Amoebozoa** A group of protozoa that move and feed using pseudopodia (temporary projections of cytoplasm). - protozoa that move and feed using pseudopodia - Often free-living, but some are parasitic - Example species: *Entamoeba histolytica* -> amebic dysentery 2. **Apicomplexa* A group of obligate intracellular parasitic protozoa characterized by an apical complex used to invade host cells. - Non-motile in adult form - All possess an apicoplast (organelle from secondary endosymbiosis) - Complex life cycles with sexual and asexual stages - Example species: *plasmodium falciparum* -> malaria, *cryptosporidium parvum* -> cryptosporidiosis, *toxoplasma gondii* -> toxoplasmosis 3. **Excavata** A diverse group of protozoa, many of which have a feeding groove ("excavated") and use flagella for movement. - Often anaerobic or have modified mitochondria - Many are intestinal parasites or live in other low-oxygen environments - Example species: *giardia duodenalis* -> giardiasis, *Trichomonas vaginalis* -> trichomoniasis (STD), *Naegleria fowleri* -> primary amebic encephalitis