Chapter 12, part B The Eukaryotes: Algae and Protozoa The Three-Domain System Eukarya Fungi Origin of mitochondria Bacteria Origin of chloroplasts Animals Amebae Mitochondria Slime molds Cyanobacteria Proteobacteria Chloroplasts Archaea Methanogens Plants Extreme halophiles Ciliates Green algae Dinoflagellates Diatoms Hyperthermophiles Gram-positive bacteria Euglenozoa Thermotoga Horizontal gene transfer occurred within the community of early cells. Giardia Mitochondrion degenerates Nucleoplasm grows larger Kingdom Protista - Subkingdom Algae (plant-like) • Eukaryotic – Unicellular – Filamentous – form chains of cells – Multicellular (thallic) - thallus (body) • of multicellular algae usually consists of: – branched holdfast – stem like stipes – leaf like blades. Subkingdom Algae (plant-like) • Most Algae are photoautotrophs. – Photosynthesized algae have chloroplasts (Chlorophyll α) – Fungal-like algae are chemoheterotrophs • Cellulose wall • Most algae are found in the ocean – Their location depend on: • wavelength of light • appropriate nutrients • surfaces on which to grow • Algae reproduce: – Asexually by cell division – Fragmentation – Sexually • Algae are classified according to: – rRNA – pigments – their structures Sexual reproduction of Algae • Isogamy is the form of sexual reproduction in which the gametes produced are identical in shape, size and motility. • Conjugation - less commonly – isogametes may be non-motile structures (Spirogyra sp.). • Resting filaments of alga cells. • Formation of conjugation tubes between two adjacent filaments. • Cytoplasmic contents of each cell form a compact mass, representing an isogamete. The isogametes from one filament migrate through the conjugation tubes into the adjacent filament. • Heterogamy - two different types of gametes are produced. . Figure 12.12b Chrysophyta Pyrrophyta Table 12.4 • Phylum Phaeophyta – Brown algae (kelp) : • Most phaeophytes live in salt water • Harvested for algin • Phylum Rhodophyta – Red algae • Live in salt water • Harvested for agar and carrageenan • Phylum Chlorophyta – Green algae • Gave rise to plants Figure 12.11b • Phylum Chrysophyta: – Diatoms • live in salt and fresh water – – – – – Pectin and silica cell walls (glass cell walls) Unicellular All photosynthetic Chlorophyll a and c, carotene, xanthophylls Store oil Fossilized diatoms formed oil – petroleum reserves Figure 12.13 • Phylum Pyrrophyta – Dinoflagellte • Have two flagella, • Live in salt water, • Some are bioluminescent. • Phylum Oomycota – Water molds (fungi like). • These organisms grow as cottony, mold-like filaments. • The filaments have cellulosebased cell walls, but no chitin as the walls of true fungi have. • They produce flagellated gametes (sex cells) that require an aquatic environment for dispersal. Roles of Algae in Nature • Algae are the primary producers in aquatic food chains. • Planktonic algae (phytoplankton) produce most of the molecular oxygen in the Earth’s atmosphere. • Petroleum is the fossil remains of planktonic algae. • Unicellular algae are symbionts in such animals as Tridacna – - Tridacna is a genus of large and gigantic saltwater clams . Subkingdom Protozoa (Animal-like protists) • Protozoa (in Greek proto = first and zoa = animals) - commonly show characteristics usually associated with animals – – – – Unicellular Many of them are motile, Heterotrophs Have complex cells • No cell wall (usually a pellicle ) • A cytostome (digestion) • An anal pore (excretion) – Ubiquitous throughout aqueous environments and the soil – Many protozoa are free living – Some are important as parasites and cause serious infections • can infect any human tissue, include intracellular and extracellular parasites • they spread using a variety of strategies – some produce cysts to survive outside the body – spread by insects – spread during human sexual contact – Symbiotic of multicellular animals. Protozoa life cycle • An individual protozoan is both male and female. • Two stages of parasitic protozoa – Trophozoites - actively feed and multiply are frequently – Cysts are stages with a protective membrane or thickened wall. • Protozoan cysts that must survive outside the host usually have more resistant walls than cysts that form in tissues. • Cysts convert back to trophozoite • Reproduction – Asexual reproduction • Binary fission, the most common form of reproduction, is asexual; multiple asexual division occurs in some forms. • Budding, or schizogony. – Sexual reproduction • Conjugation - During ciliate conjugation, two haploid nuclei fuse to produce a zygote. • Gametas - haploid • Reproductive cyst - oocyst Table 12.1 Protozoa classification • Protozoa have traditionally been divided on the basis of their means of locomotion, although this is no longer believed to represent genuine relationships: • Flagellates – flagella - long hairlike projections • Amoeboids – ameboid movement by pseudopods, which means "false foot" • Ciliates – Cilia - tiny hairlike projections • Sporozoans • Apicomplexa • Myxozoa • Microsporidia Phylum Archaeozoa • Chemoheterotrophs • No mitochondria, mitosome • Multiple flagella • Giardia lamblia – intestinal parasite of humans and other animals. • Phylogenetic studies suggest that the first eukaryotic cells may have been similar to Giardia and other archaezoans. • Trichomonas vaginalis (no cyst stage) Figure 12.17b-d Phylum Microspora • • • • No mitochondria Nonmotile Spore formation Obligate Intracellular parasites – Nosema • Diarrhea • Kerato-conjunctivitis Phylum Euglenozoa • Flagellates: The flagellates are motile by means of whip-like structures called flagella, attached to the surface of the cell. • Photoautotrophs – Intermediate between algae and protozoa – No cell wall – pellicle instead – Eye spot • Chlorophyll α • Euglenoids Euglena • Chemoheterotrophs – Naegleria • Flagellated and amoeboid forms, meningoencephalitis – Trypanosoma • Undulating membrane, parasitic in humans and other mammals, in which they cause a tropical fever known as sleeping sickness. • transmitted through the bite of the tsetse fly (vector). – Leishmania • Flagellated form in sand fly vector, ovoid form in vertebrate host Phylum Amoebozoa • Amebas: The amebas are motile by means of pseudopodia, or “false feet.” – Pseudopodia are projections of the cytoplasm and plasma membrane that form on the edge of the ameba. The cytoplasm flows into the pseudopod, moving the ameba forward • Ameba proteus– It lives in fresh water, where it feeds Amoeba proteus on other protozoa and bacteria • Entamoeba – – This is a parasitic ameba that causes severe gastrointestinal disease in humans. – Comes by drinking contaminated water. – In the intestine, the cysts break open and release actively growing cells called trophozoites. • Acanthamoeba Figure 12.18a Phylum Ciliophora (ciliates) • They are motile by means of cilia. - Paramecium – Cilia are short, hair-like structures that cover the surface of the ciliate cell. – The beat back and forth in unison, propelling the cell rapidly through the water. • Complex cells – Balantidium coli is the only human parasite Figure 12.20 Phylum of Apicomplexa • • • • • Nonmotile Intracellular parasites Complex life cycle with both sexual and asexual stages. Different stages often develop in different host species. Plasmodium – Malaria • The sexual stage occurs in the salivary glands of the Anopheles mosquito • Asexual reproduction - in the blood of the mammalian host. • • • • Babesia Cryptosporidium Cyclospora Toxoplasma: – This parasite is transmitted to humans via the oral route, by eating contaminated beef or from contact with cat feces. The Life Cycle of Plasmodium vivax 2 3 8 7 6 Figure 12.18 Slime Molds • Slime molds have been found all over the world • Have both fungal and amoeba-like qualities • Feed on microorganisms that live in any type of dead plant material. • Usually found in soil, lawns, and on the forest floor, commonly on deciduous logs. Slime mold Slime • Phylum Myxomycota – “Acellular” slime molds (Physarium ) Molds • The body form of this organism during most of its life is a multinucleated mass of cytoplasm (called a plasmodium, a type of coenocytium). • At certain times, especially when growth conditions are unfavorable, it can form stalks, called sporangia, that grow from the plasmodium. • Spores form at the end of the sporangia and are released into the environment, where they may encounter more favorable growth conditions. Slime Molds • Phylum Dictyostelida and Phylum Acrasid • Cellular slime molds. – Consist of ameba-like cells each containing a single nucleus. – Chemical signals from the cells can cause them to aggregate into a mass that resembles a plasmodium, although the individual nuclei remain separated by their plasma membranes. – Some cells become spores Arthropods as Vectors • Jointed-legged animals, including ticks and insects, belong to the Phylum Arthropoda. • Arthropods that carry diseases are called vectors. – Mechanical transmission – Biological transmission • Microbe multiplies in vector – Definitive host • Microbe’s sexual reproduction in vector • Elimination of vector borne diseases is best done by the control or eradication of the vectors. Figure 12.33 Learning objectives • • • • List the defining characteristics of algae. List the outstanding characteristics of the phyla of algae List the defining characteristics of protozoa. Describe the outstanding characteristics of phyla of protozoa • Compare and contrast cellular slime molds and plasmodial slime molds. • Define arthropod vector.