Biology II Chapter 20 Protista

Questions To Be Answered What characteristics put an organism in the protist kingdom? What are the four major groupings within this kingdom? What are the names of the main organisms and why are they important?

Chapter 20 Protozoa 20-1 Overview of Protozoa 20-2 Protozoan Diversity

Section 20-1 Overview of Protozoa Characterisitcs of Protozoa Reproduction Classification Adaptations Evolution Great Discoveries Paramecium

Characteristics of Protozoa Single-celled, microscopic Eukaryotes Able to move independently 65,000 species identified Stentor

Characteristics of Protozoa Inhabit many environments – Salt and fresh water Soil In bodies of other organisms (parasitic with complex life-cycles) Heterotrophic: obtain nutrients by ingesting small molecules or cells and digest it in a food vacuole that contains digestive enzymes.

Characteristics of Protozoa Zooplankton: a population of organisms that constitute one of the primary sources of energy in aquatic ecosystems.

Reproduction Asexual reproduction by binary fission: divides into 2 essentially identical individuals Some by multiple fission: cell division that results in a number of identical individuals

Reproduction Sexual reproduction in the form of conjugation: individuals from opposite mating strains pair and exchange genetic material.

Classification Protozoa are members of Kingdom Protista along with algae, slime molds, and water molds

Classification Research into evolutionary relationships is constantly yielding new information and altering Protistan classification

Classification Sometimes classified into 4 phyla based on means of locomotion Sarcodina (Sarcodines) – pseudopodia Ciliophora (Ciliates) – cilia Zoomastigina (Zooflagellates) – flagella Sporozoa (Sporozoans) – non-motile adults

Adaptations Many species have physiological mechanisms for monitoring conditions in their environment Eyespot: localized region of pigment that detects changes in the quantity and quality of light. Others can sense physical and chemical changes or obstacles in their environment

Adaptations Cyst: a dormant form characterized by a hardened external covering in which metabolic activity has ceased. Form in response to nutrient deficiency, drought, and decreased oxygen concentration, or pH or temperature changes. Emerge when conditions improve

Evolution First life forms 3.5 billion years ago were prokaryote (bacteria), then 1.5 billion years ago the first eukaryotic organisms evolved. Protozoa are the descendants of these early eukaryotes

Evolution Probably evolved through endosymbiosis: a process in which one prokaryote lives inside another and gradually both host and guest become dependent on one another.

Great Discoveries: The Origin of Eukaryotic Cells Lynn Margulis -Symbiosis of Cell Evolution Animation/tutorial

Mitochondria and chloroplasts are: Self-dividing Approximately the same size as prokaryotes Able to make proteins and lipids DNA within are similar to bacteria DNA rather than eukaryotic DNA Ribosomes within are more similar to those in prokaryotes in size and are sensitive to antibiotics like bacteria Synthesize protein using metabolic steps that bacteria use Chloroplast produce energy in the same way that some bacteria produce energy

Great Discoveries: The Origin of Eukaryotic Cells Kwang Jeon: infected a species of amoeba with bacteria parasite. Cultured amoebas that survived infection, producing a line of amoebas dependent on the bacteria for survival.

Protozoan Diversity Phylum Sarcodina Phylum Ciliophora Phylum Zoomastigina Phylum Sporozoa

Phylum Sarcodina 40,000 species – 100’s of species of amoebas Inhabit fresh water, salt water, soil Ex. Pelomyxa carolinensis – live on mud and rocks in shallow, slow-moving streams or ponds.

Pseudopodia Large, rounded cytoplasmic extensions (flexible cell membranes) that function in movement. Forms when the endoplasm (inner portion of cytoplasm) pushes the ectoplasm (outer portion) forward to create a blunt arm-like extension. Other pseudopodia retract and cytoplasm flows in direction of new pseudopodium

Referred to as ameboid movement: a form of cytoplasmic streaming Pseudopodia also used for feeding – engulf other Protists by phagocytosis – surrounds food with its pseudopodia and a portion of the cell membrane then pinches together and encloses the food vacuole in a process called endocytosis, then enzymes from the cytoplasm enter vacuole and digest the food. Wastes leave cell in reverse process called exocytosis.

Contractile vacuole An organelle that expels fluid from the cell. Freshwater organisms are usually hypertonic relative to their environment so water continually diffuses into them. To maintain homeostasis, it must use contractile vacuole to rid cell of excess water.

Ecological Role: Foraminifera and Radiolarians Test: protective shell made of calcium carbonate (foraminifera) or silicon dioxide (radiolarians). Slender pseudopodia extend through opening in test. Foraminifera and Radiolarians

Radiolarians formed a type of rock called chert Existed since Precambrian times leaving an excellent fossil record. Tests of dead organisms have been sinking to the bottom of the ocean for millions and millions of years. Foraminifera have built up a calcium-rich layer of sediment that has created limestone and chalk deposits. Ex. White Cliffs of Dover, England and the Great pyramids of Egypt Radiolarians formed a type of rock called chert

Human Diseases from Sarcodina Most are free-living, some live in the intestines of humans or other animals Entamoeba histolytica (amoebic dysentery): Enters body via contaminated food and water. Lives in the large intestine and secretes enzymes that attack the intestinal lining and cause deep ulcers. Affected individuals feel intense pain and complications arise when amoebas are carried by blood to the liver and other organs.

Phylum Ciliophora 8,000 species Paramecium 8,000 species Swim by means of cilia – short, hair-like cytoplasmic projections that line the cell membrane. Example: Paramecium: abundant in ponds, slow-moving streams that contain plants and decaying organic matter

Phylum Ciliophora Zoothamnium Cilia: beat in synchronized strokes that pass waves across the cell causing the protozoan to rotate on its axis. Feed on bacteria, algae, and other small organisms found in marine and fresh water habitats.

Internal Structure Pellicle: clear, elastic layer of protein surrounds the cell membrane Oral groove: funnel-like depression lined with cilia. Beating cilia create water currents that sweep food down groove to mouth pore and gullet where food vacuole forms.

Anal pore: where waste is expelled Multinucleated: have at least one macronucleus and one micronucleus. Macronucleus contains multiple copies of DNA and is responsible for metabolic and developmental functions necessary for asexual reproduction. Micronucleus: participates in exchange of genetic info during conjugation.

Reproduction in Ciliophora Asexual reproduction by binary fission Only the micronucleus divides by mitosis. Macronucleus which has up to 500x more DNA than the micronucleus, simply elongates and splits in half. One goes into each new cell

Sexual reproduction by Conjugation Two organisms of opposite mating strains line up and join together. Macronucleus disintegrates Each diploid micronucleus undergoes meiosis, producing 4 haploid micronuclei. All but one disintegrates. Remaining micronuclei divides by mitosis producing 2 identical haploid micronuclei. Two paramecium exchange 1 micronuclei

The 2 micronuclei in each fuse to form one diploid micronucleus in each paramecium. Paramecium separate. Macronucleus forms in each from products of mitotic divisions of the micronucleus. Although genetic material was exchanged no new cells are produced. Following conjugation, each paramecium divides, producing a total of 4 genetically identical paramecia which are genetically different from either of the original paramecia.

http://www.vaxa.com/intestinal-protozoa.cfm

Phylum Zoomastigina 2500 species Trichomonas 2500 species Characterized by presence of one or more flagella: long hair-like structures that are made up of microtubules and are used for movement. rapid whipping motion pushes or pulls protozoan through water

Phylum Zoomastigina Many are free-living in ponds or lakes and feed on small organisms.

Phylum Zoomastigina Example: Giardia lamblia (giardiasis) Severe diarrhea, intestinal cramps. Several kinds of animal carry parasite and contaminate water with their feces. Trichonympha live in the gut of termites and help digest cellulose.

Human Disease of Zoomastigina Genus Trypanosoma: live in blood of fish, amphibians, reptiles, birds, and mammals. Carried from host to host by bloodsucking insects African trypanosomiasis: sleeping sickness. Transmitted by tsetse fly. Causes fever, lethargy, mental disorientation, coma Trypanosoma

Trypanosoma cruzi: Chagas’ disease. Transmitted by “kissing bug” Trypanosoma cruzi: Chagas’ disease. Transmitted by “kissing bug”. Fever and severe heart damage.

Leishmania donovani: Transmitted by sand fleas. Causes leishmaniasis. Blood disease afflicts millions of people in Africa, Asia and Latin America. Disfiguring skin sores, can be fatal.

Phylum Sporozoa 6,000 species No means of locomotion in adults Plasmodium 6,000 species No means of locomotion in adults

Phylum Sporozoa Most species are parasitic Have complex life cycles in which they develop a spore Infective form protected by a resistant coat Carried in the blood and other tissues of their hosts where they absorb nutrients and destroy host tissues.

Example: Toxoplasma gondii: Found in birds, rodents, and domestic cats. Causes toxoplasmosis. Few to no symptoms in healthy adults but can cause damage to developing fetus or newborn.

Example: Plasmodium Causes malaria. Characterized by severe chills, fever, sweating, fatigue, and great thirst. Victims die of anemia, kidney failure or brain damage. Four species infect humans. All have life cycles that involve the female Anopheles mosquito.

Treating Malaria An effective way to reduce human deaths from malaria is to control mosquito population and interrupt the parasite’s life cycle. Cured with drug derived from Cinchona tree, native to Americas. Quinine used for over 500 years. Sporozoan’s resistance to antimalarial drugs is a significant worldwide problem. Possible vaccination developed in the future.