Lecture 14

Chapter 12, part B
The Eukaryotes: Algae and
The Three-Domain System
Origin of mitochondria
Origin of chloroplasts
Slime molds
Horizontal gene transfer
occurred within the
community of early cells.
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
(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)
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
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
Many of them are motile,
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
• 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
• Trichomonas vaginalis (no cyst stage)
Figure 12.17b-d
Phylum Microspora
No mitochondria
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
• 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
• 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
Intracellular parasites
Complex life cycle with both sexual and asexual stages.
Different stages often develop in different host species.
– Malaria
• The sexual stage occurs in the salivary glands of the Anopheles mosquito
• Asexual reproduction - in the blood of the mammalian host.
– 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
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
• Usually found in soil, lawns, and on the forest floor, commonly on
deciduous logs.
Slime mold
• Phylum Myxomycota
– “Acellular” slime molds (Physarium )
• 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
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
• Compare and contrast cellular slime molds and
plasmodial slime molds.
• Define arthropod vector.