Apicomplexans: Characteristics and Life Cycle

Questions and Answers

What is a characteristic feature of Euglenids?

Having membrane-bounded sacs (alveoli) just under the plasma membrane

Having a single mitochondrion with a kinetoplast

Being a parasitic trypanosome

Having one or two flagella that emerge from a pocket at one end of the cell (correct)

Trypanosoma gambiense causes Chagas' disease.

False

Dinoflagellates are abundant components of both marine and freshwater _______________.

phytoplankton

Match the following groups with their characteristics:

Euglenids = Having one or two flagella that emerge from a pocket at one end of the cell Kinetoplastids = Having a single mitochondrion with a kinetoplast Dinoflagellates = Are abundant components of both marine and freshwater phytoplankton Alveolates = Having membrane-bounded sacs (alveoli) just under the plasma membrane Signup and view all the answers

What is the name of the disease caused by another pathogenic trypanosome?

Chagas' disease Signup and view all the answers

The SAR supergroup is universally accepted as monophyletic.

False Signup and view all the answers

What is the characteristic feature of Apicomplexans?

Infectious cells called sporozoites Signup and view all the answers

Apicomplexans have only asexual stages.

False Signup and view all the answers

What is the name of the parasite that causes malaria?

Plasmodium Signup and view all the answers

Ciliates have large ______________________ and small micronuclei.

macronuclei Signup and view all the answers

What is the function of cilia in Ciliates?

To move and feed Signup and view all the answers

Match the following Alveolates with their characteristics:

Apicomplexans = Parasites of animals Ciliates = Use cilia to move and feed Signup and view all the answers

What is the process by which a unicellular organism engulfs another cell, which becomes an endosymbiont and then an organelle in the host cell?

Endosymbiosis Signup and view all the answers

Mitochondria are believed to have evolved by endosymbiosis of a photosynthetic cyanobacterium.

False Signup and view all the answers

Diatoms have a sexual stage called conjugation.

False Signup and view all the answers

What composes much of the sediments known as diatomaceous earth?

Fossilized diatom walls Signup and view all the answers

What is the name of the pathogen that causes yeast infections in human females?

Trichomonas vaginalis Signup and view all the answers

Diplomonads have modified mitochondria called _______________________.

mitosomes Signup and view all the answers

Match the following protist groups with their characteristics:

Diplomonads = Have modified mitochondria called mitosomes Parabasalids = Have reduced mitochondria called hydrogenosomes Euglenids = Are photosynthetic Signup and view all the answers

What is the name of the organelle found in diplomonads that is involved in anaerobic biochemical pathways?

mitosomes Signup and view all the answers

What is a characteristic shared by most protists?

They are single-celled Signup and view all the answers

Protists are classified into only two supergroups: Excavata and SAR.

False Signup and view all the answers

What is the term for the process by which an organism engulfs another cell, leading to the formation of organelles?

endosymbiosis Signup and view all the answers

Some protists are ______________________, obtaining energy by ingesting or absorbing nutrients.

heterotrophic Signup and view all the answers

Match the following protist characteristics with their definitions:

Eukaryotic = Has no nucleus Photosynthetic = Uses chloroplasts for photosynthesis Heterotrophic = Ingests or absorbs nutrients Mixotrophic = Switches between autotrophy and heterotrophy Signup and view all the answers

How do some protists obtain nutrients?

Through both phagocytosis and diffusion Signup and view all the answers

All protists are autotrophic.

False Signup and view all the answers

Primary endosymbiosis occurs when a heterotrophic eukaryote consumes a ______________________ cell, leading to the formation of red or green algae.

bacterial Signup and view all the answers

What is unique about the cytoskeleton of Excavates?

It has unique properties Signup and view all the answers

Parabasalids are known to produce oxygen as a byproduct of their energy production

False Signup and view all the answers

What is the name of the disease caused by Trypanosoma?

African sleeping sickness and Jacques disease Signup and view all the answers

Euglenozoa have rod-shaped _______________________.

flagella Signup and view all the answers

Match the following Excavate subgroups with their characteristics:

Diplomonads = Parabasalids a) modified mitochondria called microsomes, two nuclei, multiple flagella, and anaerobic energy production = b) reduced number of mitochondria, anaerobic, and produce hydrogen gas as a byproduct Signup and view all the answers

What is a characteristic feature of Alveolates?

Presence of alveoli Signup and view all the answers

Stramenopiles can be only photoautotrophic.

False Signup and view all the answers

What is the name of the disease caused by Plasmodium?

malaria Signup and view all the answers

Dinoflagellates can be found in ______________________ environments.

freshwater and marine Signup and view all the answers

Match the following Alveolates with their characteristics:

Dinoflagellates = Have two whip-like flagella Apicomplexans = Include parasites like Plasmodium Ciliates = Have rows of cilia Signup and view all the answers

What is a characteristic feature of Diatoms?

Presence of a silica test or frustule Signup and view all the answers

Ciliates can only reproduce asexually.

False Signup and view all the answers

What is the name of the pigment that gives Golden Algae their characteristic color?

yellowish Signup and view all the answers

Brown Algae are found in ______________________ environments.

marine Signup and view all the answers

What is the term for the process by which an organism engulfs another cell, leading to the formation of organelles?

Endosymbiosis Signup and view all the answers

What is a characteristic feature of Brown Algae?

They have structures that resemble those of plants Signup and view all the answers

Red Algae obtain their color from an abundance of the pigment chlorophyll.

False Signup and view all the answers

What is the term for the process by which Brown Algae undergo an alternation of generations?

Alternation of generations (where diploid sporophytes produce haploid spores that develop into gametophytes) Signup and view all the answers

Green Algae are characterized by their ______________________ shape.

filamentous Signup and view all the answers

Which of the following is an example of a Green Algae?

All of the above Signup and view all the answers

Match the following Algae groups with their characteristics:

Green Algae = Found mainly in freshwater environments Red Algae = Obtain their color from an abundance of phycocyanin Brown Algae = Have structures that resemble those of plants Signup and view all the answers

Volvox is a type of Brown Algae.

False Signup and view all the answers

Stramenopiles are characterized by having two flagella, one ______________________ and one hairy.

smooth Signup and view all the answers

What is the characteristic feature of amoeboid protists?

Moving using pseudopodia Signup and view all the answers

Ryze area is a subgroup of Uniconta protists.

False Signup and view all the answers

What is the common feature of Foraminifera and Radialarians?

Tests Signup and view all the answers

Uniconta is a clade that includes protists, animals, and ______________________.

fungi Signup and view all the answers

Which of the following is an example of a Uniconta protist?

Slime mold Signup and view all the answers

Entamoebas are parasites of the gastrointestinal system of mammals.

True Signup and view all the answers

Match the following amoeboid protists with their characteristics:

Tubulinians = Amoebas that move using cytoplasmic streaming Entamoebas = Parasites of the gastrointestinal system of mammals Foraminifera = Have tests made of calcium carbonate Slime molds = Can form a sporangium and release spores Signup and view all the answers

What is the term for the extensions of cytoplasm used for locomotion and capturing prey in amoeboid protists?

Pseudopodia Signup and view all the answers

What happens to the merozoites after they penetrate the red blood cells?

They divide asexually inside the blood cell and then break out to infect other RBC Signup and view all the answers

Ciliates have only one type of nucleus.

False Signup and view all the answers

What is the process by which genetic variation occurs in Ciliates?

Conjugation Signup and view all the answers

Sporozoites infect _______________________ cells.

liver Signup and view all the answers

Match the following stages in the life cycle of Plasmodium with their descriptions:

Sporozoites = Injected by mosquito into human Merozoites = Formed from sporozoites in liver cells and infect red blood cells Gametocytes = Formed from some merozoites and infect another mosquito Zygote = Formed from gametes in mosquito digestive tract Signup and view all the answers

What is the characteristic feature of Alveolates?

They have membrane-enclosed sacs (alveoli) just under the plasma membrane Signup and view all the answers

Apicomplexans have only asexual stages.

False Signup and view all the answers

What is the name of the parasite that causes malaria?

Plasmodium Signup and view all the answers

Brown Algae are found in _______________ environments.

deep part of the ocean Signup and view all the answers

Match the following Alveolates with their characteristics:

Dinoflagellates = have two flagella twisted around the cell Apicomplexans = parasites of animals, and some cause serious human diseases Ciliates = have membrane-enclosed sacs (alveoli) just under the plasma membrane Signup and view all the answers

All Brown Algae are unicellular.

False Signup and view all the answers

What is the term for the process by which Brown Algae undergo an alternation of generations?

Alternation of generations Signup and view all the answers

What is the type of life cycle that brown algae Laminaria has?

Alternation of generations Signup and view all the answers

What role do protists play in their habitats?

Both symbiont and producer Signup and view all the answers

Some protists are parasitic.

True Signup and view all the answers

What is the name of the disease caused by Pfiesteria shumwayae?

Fish kills Signup and view all the answers

Photosynthetic protists are limited by ______________________ in aquatic environments.

nutrients Signup and view all the answers

Match the following protist groups with their characteristics:

Dinoflagellates = Causes red tides Phytoplankton = Important producers that obtain energy from the sun Plasmodium = Causes malaria Signup and view all the answers

What happens to the biomass of photosynthetic protists when sea surface temperature increases?

It decreases Signup and view all the answers

Study Notes

Apicomplexans

Are parasites of animals and cause serious human diseases
Spread through their host as infectious cells called sporozoites
Have a complex of organelles at one end (apex) for penetrating host cells and tissues
Have sexual and asexual stages that require two or more different host species to complete
Plasmodium is an apicomplexan that causes malaria and requires both mosquitoes and humans to complete its life cycle
Approximately 900,000 people die each year from malaria

Ciliates

Are a large and varied group of protists that use cilia to move and feed
Have large macronuclei and small micronuclei
Genetic variation results from conjugation, a sexual process in which two individuals exchange haploid micronuclei
Conjugation is separate from reproduction, which generally occurs by binary fission

Stramenopila

Includes important phototrophs and heterotrophs
Most have a "hairy" flagellum paired with a "smooth" flagellum
Includes diatoms, golden algae, brown algae, and oomycetes

Diatoms

Are unicellular algae with a unique two-part, glass-like wall of hydrated silica
Are a major component of phytoplankton and are highly diverse
Fossilized diatom walls compose much of the sediments known as diatomaceous earth
Reproduction is mainly asexual

Euglenozoa

Is a diverse clade that includes euglenids and kinetoplastids
Some are predatory heterotrophs, photosynthetic autotrophs, and parasites
Distinguished by a spiral or crystalline rod of unknown function inside their flagella
Euglenids have one or two flagella that emerge from a pocket at one end of the cell
Kinetoplastids have a single mitochondrion with an organized mass of DNA called a kinetoplast
Include free-living consumers of prokaryotes in freshwater, marine, and moist terrestrial ecosystems
Trypanosoma gambiense causes sleeping sickness in humans, and another pathogenic trypanosome causes Chagas' disease leading to congestive heart failure

SAR

Is a supergroup that may have originated by a secondary endosymbiosis event with a red alga
Includes the alveolates and the stramenopiles

Alveolata

Are a sub-group of SAR that have membrane-bounded sacs (alveoli) just under the plasma membrane
Function of alveoli is unknown
Includes dinoflagellates, apicomplexans, and ciliates

Dinoflagellates

Have two flagella and each cell is reinforced by cellulose plates
Are abundant components of both marine and freshwater phytoplankton
Are a diverse group of aquatic phototrophs, mixotrophs, and heterotrophs
Toxic "red tides" are caused by dinoflagellate blooms

Endosymbiosis and Protist Evolution

Endosymbiosis is the process in which a unicellular organism engulfs another cell, which becomes an endosymbiont and then organelle in the host cell
Mitochondria are believed to have evolved by endosymbiosis of an aerobic prokaryote
Plastids are believed to have evolved by endosymbiosis of a photosynthetic cyanobacterium

Introduction to Protists

Protists are diverse eukaryotic organisms varying in shape, size, and patterns, with different numbers and types of organelles.
The kingdom Protista was dismantled in the 1990s, and now protists are classified into four supergroups: Excavata, SAR, Archaeplastida, and Opisthokonta.

Characteristics of Protists

Most protists are unicellular, but some form colonies or are multicellular.
They have membrane-bound organelles and a nucleus, making them eukaryotic.
Protists have diverse nutritional strategies: photoautotrophy, heterotrophy, and mixotrophy.

Nutrition and Metabolism

Photoautotrophic protists use chloroplasts for photosynthesis.
Heterotrophic protists obtain energy by ingesting or absorbing nutrients.
Mixotrophic protists, like Euglena, switch between autotrophy and heterotrophy.
Some protists use phagocytosis or diffusion to obtain nutrients.

Reproduction

Protists can reproduce asexually or sexually using meiosis and fertilization.
Some protists, like kelp, exhibit alternation of generations, where two distinct generations are needed to complete one life cycle.

Symbiotic Relationships

Endosymbiosis is where one organism engulfs another, leading to the formation of organelles like mitochondria and chloroplasts.
Primary endosymbiosis occurs when a heterotrophic eukaryote consumes a bacterial cell, forming red or green algae.
Secondary endosymbiosis occurs when a heterotrophic eukaryote consumes an alga, forming chloroplasts in other protists.

Protist Super Groups

Protists are classified based on morphological and DNA data, including cellular walls, ribosomes, and DNA molecules.

Excavates

Excavates have unique cytoskeleton properties, modified mitochondria, and flagella different from other organisms.

Diplomonads

Diplomonads have modified mitochondria called microsomes with no electron transport chain.
They have two nuclei and multiple flagella.
They produce energy anaerobically.
Example: Giardia lamblia, a parasite found in stagnant water, causes severe diarrhea and vomiting.

Parabasalids

Parabasalids have a reduced number of mitochondria.
They are anaerobic and produce hydrogen gas as a byproduct.
Example: Trichomonas vaginalis, a sexually transmitted disease, causes burning and itching sensations in women.

Euglenozoa

Euglenozoa have rod-shaped flagella.
They have a kinetoplast (a single large mitochondrion with DNA).
Example: Trypanosoma, which causes African sleeping sickness and Jacques disease, affects red blood cells, and causes fever and fatigue.

Neuglenids

Neuglenids have a pocket at one end with one or two flagella emerging.
They are mixotrophic, able to undergo photosynthesis and ingest other creatures.
Example: Euglena, found in pond water, is oval-shaped with a curved excavated side.

SAR Clade

Consists of stramenopiles, alveolates, and rhizarians, and is monophyletic, meaning it has a single common ancestor
Originated from a common endosymbiotic event involving a red alga and a heterotrophic eukaryote

Alveolates

Characterized by the presence of alveoli, membrane-bound air pockets that trap respiratory gases
Include dinoflagellates, apicomplexans, and ciliates
Dinoflagellates can cause red tides and produce toxins that can cause gastrointestinal poisoning in humans
Apicomplexans include parasites like Plasmodium, which causes malaria, and have a complex life cycle involving multiple hosts
Ciliates have rows of cilia and can reproduce sexually or asexually

Dinoflagellates

Characterized by the presence of two whip-like flagella
Found in freshwater and marine environments
Can be photoautotrophic, heterotrophic, or mixotrophic
Responsible for red tides and can produce toxins that can cause gastrointestinal poisoning in humans

Apicomplexans

Include parasites like Plasmodium, which causes malaria
Have a complex life cycle involving multiple hosts
Can change surface proteins to evade host immune system, making vaccine development challenging
Transmitted through mosquitoes

Ciliates

Characterized by the presence of rows of cilia
Can reproduce sexually or asexually through binary fission
Have a micronucleus and a macronucleus, involved in conjugation and genetic exchange
Paramecium is an example of a ciliate with a complex life cycle involving conjugation and nuclear exchange

Stramenopiles

Characterized by the presence of a hairy flagellum
Include diatoms, golden algae, brown algae, and oomycetes
Can be photoautotrophic or heterotrophic
Have diverse strategies for obtaining energy and nutrients

Diatoms

Characterized by the presence of a silica test or frustule
Found in freshwater and marine environments
Primary producers, playing a key role in aquatic food chains
Have a unique life cycle involving asexual reproduction through binary fission

Golden Algae

Characterized by the presence of flagella and a yellowish pigment
Can be photoautotrophic or mixotrophic
Can be unicellular or colonial
Have a complex life cycle involving sexual reproduction

Brown Algae

Characterized by the presence of a brown pigment
Found in marine environments
Complex multicellular organisms that can resemble plants
Have a unique life cycle involving alternation of generations, with a diploid sporophyte stage and a haploid gametophyte stage.

Brown Algae

Brown algae are multicellular protists with plant-like structures, including holdfast, stipe, blades, and bladders.
Holdfast is a root-like structure that anchors the algae to rocks or substrate, but does not absorb nutrients.
Stipe is a stem-like structure that holds up the algae.
Blades are leaf-like structures that hold photosynthetic cells.
Bladders are bubble-like structures that help the algae float upright towards the water's surface.
Brown algae undergo alternation of generations, where diploid sporophytes produce haploid spores that develop into gametophytes.
Gametophytes produce gametes that fuse to form a zygote, which develops into a sporophyte.
Sporophytes produce spores through meiosis, which develop into gametophytes.
Brown algae belong to the stramenopile group, characterized by having two flagella, one smooth and one hairy.

Red Algae

Red algae are multicellular protists that obtain their color from an abundance of phycocyanin, which reflects red light.
Phycocyanin can also make the algae appear bluish, purple, or green.
Some edible varieties of red algae, such as nori, are used in sushi rolls.
Most red algae are multicellular, with a few exceptions being single-celled.

Green Algae

Green algae are multicellular protists that live mainly in freshwater, with a few species found in oceans.
They are characterized by their filamentous shape, such as in Spirulina and Chlorella.
Volvox is a type of green algae studied in biology labs, characterized by its flagellated cells and multicellular structure.
Sea lettuce (Ulva) is a type of green algae found in oceans, characterized by its flat, broad, and smooth blades.
Caulerpa is another type of green algae found in oceans.
Green algae are important contributors to the food chain, providing energy for organisms like fish, snails, and sea urchins.

Amoeboid Protists

Amoeboid protists move using pseudopodia or extensions of their cytoplasm and are a diverse group.

Characteristics of Ryze Area Protists

Ryze area is a subgroup of SAR (superphylum) protists.
The name "Ryze" means "root" in Greek, referring to their long, thin cytoplasmic extensions used for locomotion and capturing prey.
Examples of Ryze area protists include:
- Foraminifera, which have a protective structure called a test made of calcium carbonate with perforations that allow pseudopodia to move out.
- Radialarians, which have tests made of silica, with intricate patterns and shapes, and use pseudopodia for locomotion and capturing food.

Characteristics of Uniconta Protists

Uniconta is a clade that includes protists, animals, and fungi.
The common ancestor to all these organisms is still unknown to scientists.
Examples of Uniconta protists include:
- Slime molds, which can be:
  - Acellular, with many cells without plasma membranes and multiple nuclei, forming a sporangium and releasing spores.
  - Cellular, with each amoeba having its own nucleus and plasma membrane, forming aggregates that migrate and feed before reproducing.

Other Amoeboid Protists

Tubulinians (formerly Gemmaceae) are amoebas that move using cytoplasmic streaming, with lobe-like pseudopodia, and are heterotrophic, feeding on other protists, algae, and bacteria.
Entamoebas are amoebas that can be parasites of the gastrointestinal system of mammals, including humans, and can cause severe diseases like amoebic dysentery.

Brown Algae

Brown algae are the largest and most complex algae, consisting of multicellular species commonly called “seaweeds”.
Giant seaweeds called kelps live in deep parts of the ocean, with a rootlike holdfast that anchors the algae, a stemlike stipe that supports leaflike blades.
Brown algae exhibit analogous structures with plants, showing similarities between the two groups.

Alternation of Generations

The life cycle of brown algae involves the alternation of multicellular haploid and diploid forms.
Sporophyte (2n) produces unicellular zoospores (n) through meiosis, which develop into heteromorphic male and female multicellular gametophytes (n).
Fertilization occurs between gametophytes, resulting in a zygote that grows into a new sporophyte.

Alveolates

Alveolates are a group of organisms characterized by membrane-enclosed sacs (alveoli) just under the plasma membrane.
Alveolates include Dinoflagellates, Apicomplexans, and Ciliates.

Dinoflagellates

Dinoflagellates have two flagella twisted around the cell and are reinforced by cellulose plates.
They are components of both marine and freshwater phytoplankton, consisting of phototrophs, mixotrophs, and heterotrophs.
Dinoflagellates can cause Toxic “red tides”.

Apicomplexans

Apicomplexans are parasites of animals, with some causing serious human diseases.
They are spread as infectious cells called sporozoites, which have an apex containing a complex of organelles specialized for penetrating host cells and tissues.
Apicomplexans have an organelle called Apicoplast, which has a circular genome similar to chloroplast genome.
Apicoplasts' enzymes are a possible malaria drug target.

Life Cycle of Apicomplexan Plasmodium (Malaria)

The life cycle involves two hosts: humans and Anopheles mosquitoes.
Sporozoites (n) are injected into humans through mosquito bites, infecting liver cells and dividing into merozoites (n).
Merozoites infect red blood cells, causing symptoms in humans.
Some merozoites form gametocytes (n), which are then taken up by mosquitoes, where fertilization occurs, and a zygote (2n) forms.
The zygote develops into an oocyst, releasing thousands of sporozoites (n) via meiosis, which migrate to the mosquito's salivary gland.

Ciliates

Ciliates use cilia to move and feed, and have two types of nuclei: large macronuclei and small micronuclei.
Genetic variation in ciliates results from conjugation, where two individuals exchange haploid micronuclei.

Protists as Symbionts

Protist symbionts can benefit their hosts, such as dinoflagellates that nourish coral polyps, which build reefs.
Wood-digesting protists can digest cellulose in the gut of termites.
Some protists are parasitic, causing diseases in hosts, such as:
- Plasmodium, which causes malaria.
- Pfiesteria shumwayae, a dinoflagellate that causes fish kills (red tides).
- Phytophthora ramorum, which causes sudden oak death.
- P.infestans, which causes potato blight, contributing to the Irish famine of the 19th century.

Protists as Producers

Many protists are important producers that obtain energy from the sun.
In aquatic environments, photosynthetic protists and prokaryotes are the main producers, upon which other organisms depend for food.
Photosynthetic protists in aquatic environments are limited by nutrients.
Adding limiting nutrients can cause protist populations to explode, such as when fertilizers used in fields are washed into oceans.
An increase in sea surface temperature has led to a decline in the biomass of photosynthetic protists.
The growth of phytoplankton communities relies on nutrients delivered from the ocean bottom through the process of upwelling.
Warm surface water acts as a barrier to upwelling, affecting phytoplankton growth.

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Description

Learn about apicomplexans, parasites that cause serious human diseases, their life cycle, and how they spread through hosts. Includes information on Plasmodium and malaria.