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Protist diversity

With the advent of DNA sequencing, the relationships among protist groups and between protist groups and other eukaryotes are beginning to become clearer. Many relationships that were based on morphological similarities are being replaced by new relationships based on genetic similarities. Protists that exhibit similar morphological features may have evolved analogous structures because of similar selective pressures—rather than because of recent common ancestry. This phenomenon is called convergent evolution. It is one reason why protist classification is so challenging. The emerging classification scheme groups the entire domain Eukaryota into six “supergroups” that contain all of the protists as well as animals, plants, and fungi ( [link] ); these include the Excavata    , Chromalveolata    , Rhizaria    , Archaeplastida    , Amoebozoa    , and Opisthokonta    . The supergroups are believed to be monophyletic; all organisms within each supergroup are believed to have evolved from a single common ancestor, and thus all members are most closely related to each other than to organisms outside that group. There is still evidence lacking for the monophyly of some groups.

The chart shows the relationships of the eukaryotic supergroups, which all arose from a common eukaryotic ancestor. The six groups are Excavata, Chromalveolata, Rhizaria, Archaeplastida, Amoebozoa, and Opisthokonta. Excavata includes the kingdoms diplomads, parabasalids, and euglenozoans. Chromalveola includes the kingdoms dinoflagellates, apicomplexans, and ciliates, all within the alveolate lineage, and the diatoms, golden algae, brown algae, and oomyctes, all within the stramenopile lineage. Rhizaria includes cercozoans, forams, and radiolarians. Archaeplastida includes red algae and two kingdoms of green algae, chlorophytes and charophytes, and land plants. Amoebozoa includes slime molds, gymnamoebas, and entamoebas. Opisthokonta includes nucleariids, fungi, choanoflagellates, and animals.
Protists appear in all six eukaryotic supergroups.

Human pathogens

Many protists are pathogenic parasites that must infect other organisms to survive and propagate. Protist parasites include the causative agents of malaria, African sleeping sickness, and waterborne gastroenteritis in humans. Other protist pathogens prey on plants, effecting massive destruction of food crops.

Plasmodium Species

Members of the genus Plasmodium must infect a mosquito and a vertebrate to complete their life cycle. In vertebrates, the parasite develops in liver cells and goes on to infect red blood cells, bursting from and destroying the blood cells with each asexual replication cycle ( [link] ). Of the four Plasmodium species known to infect humans, P . falciparum accounts for 50 percent of all malaria cases and is the primary cause of disease-related fatalities in tropical regions of the world. In 2010, it was estimated that malaria caused between 0.5 and 1 million deaths, mostly in African children. During the course of malaria, P . falciparum can infect and destroy more than one-half of a human’s circulating blood cells, leading to severe anemia. In response to waste products released as the parasites burst from infected blood cells, the host immune system mounts a massive inflammatory response with delirium-inducing fever episodes, as parasites destroy red blood cells, spilling parasite waste into the blood stream. P . falciparum is transmitted to humans by the African malaria mosquito, Anopheles gambiae . Techniques to kill, sterilize, or avoid exposure to this highly aggressive mosquito species are crucial to malaria control.

The light micrograph shows round red blood cells, each about 8 microns across, infected with ring-shaped P. falciparum.
This light micrograph shows a 100× magnification of red blood cells infected with P . falciparum (seen as purple). (credit: modification of work by Michael Zahniser; scale-bar data from Matt Russell)

Concept in action

This movie depicts the pathogenesis of Plasmodium falciparum , the causative agent of malaria.

Questions & Answers

difference between DNA and RNA
Eyitayo Reply
what determines the aeration level in the soil
Shola Reply
what is homeostasis?
Sarita Reply
What is biology
Don Reply
Biology z the study of life
GOLDEN
what's biology
buran
biology is the study of living nd none living organism
Chinaza
Biology is the study of life
Quadri
yes Sir
Said
what's cell biology
Prince
biology is the study of life
Raheal
what is asexual reproduction,?
Awoi Reply
A type of reproduction which does not involve the fusion of gametes or a change in the number of chromosomes
Serena
Reproduction without sex... In which form a single organism or cell makes a copy of itself.
Serena
Please explain the concept of mitosis and meiosis
Serena
I guess you could use it for study buddies and brushing up on what you need to
Serena
what is mitosis
Klp
Asexual reproduction?
Serena
why pepsin and trypsin released in active form?
Yacqub
mitosis is the type cell division in which two daughter cells have same no. of chormosomes
syed
Hi
Don
chromosome number remains the same in mitosis
mc
Ello
Henry
Hii
Nikky
Yrr help me.
Nikky
Physical chemistry..... Koi h jo mujhe physical chem ki notes send kr ske
Nikky
what is asexual reproduction
Targbe
what makes golgi body in plants
Abdulkareem Reply
name the membrane of the plants
Abdulkareem
how can turners syndrome be corrected before birth
Balinda
which animal survive from being preyed just because of being humble, slow, and not aggressive
Balinda
During organs transplantation, the organs cannot be taken from just anybody since the graft would be rejected sooner or later due to
Liter Reply
Non-MHC compatibility on the organ and an attack from the patient's immune system.
Eric
what makes golgi body in plants
Abdulkareem
why trypsin and pepsin released in active form
Yacqub
what is integument system
Joy Reply
Cellular respiration
Lucy Reply
what are the characteristics of living things
Ruth Reply
Movement Respiration Nutrition/Feeding Irritability/Sensitivity Growth Excretion Reproduction Deat/Life span
Hashim
What makes children from the same father and mother sometimes don't look alike?
Hashim
identification of problems
Nana Reply
what happens in the process of raising the human arms
Nana
what is biology
Brandi Reply
first step in scientific method
Brandi
In an investigation the pancreatic duct of a mammal was blocked.It was found that the blood sugar regulation remained normal while food digestion was impaired.Explain
Mac Reply
To begin with, obstruction of pancreatic duct will alter the blood sugar level as the juices responsible for glucose regulation will be rendered inconsequential. This will in turn affect the rate of digestion and absorbtion of digested food substances by the Villus .
Muktar
characteristics of algae
OMIME Reply
Algae are eukaryotic organisms. Algae do not have roots and stems. Algae have chlorophyll and helps in carrying out photosynthesis.
Aditi
Cell wall is the rigid layer enclosed by membranes of plants and prokayortic cell, it maintains the shape of the cell and serve as a protective barrier.
chizoba Reply
ECOLOGY: is a branch of biology that studies the interactions among organisms and their biophysical environment, which includes both biotic and abiotic components. 
chizoba
via nutrient cycles and energy flows. For instance, the energy from the sun is captured by plants through photosynthesis. Photosynthesis is a biological process through which plants manufacture their own food with the aid of light from the sun and frc sources (e.g. cabon dioxide and water)
chizoba

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Source:  OpenStax, Concepts of biology. OpenStax CNX. Feb 29, 2016 Download for free at http://cnx.org/content/col11487/1.9
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