Protozoa

Name means “first animals”

215,000 described species. Equal to the number of described vascular plants

10 times more diverse than bacteria and viruses

Primitive: single celled or colonial– (gave rise to modern day

plants and animals); many are symbiotic

Great variety in every aspect:Feeding / energeticsLife cyclesReproductionPhysiology /

osmoregulationLocomotionMorphology

Protozoans

The Eukaryotic Cell Protists lack cellular specialization (with few exceptions)

Individual organelles carry out all physiological processes

Cell membrane Barrier to the outside environment Selective passage of molecules Plays a role in endo / exocytosis

Cytoplasm Ectoplasm – outer, stiff, portion Endoplasm – inner, fluid, portion

Internal membrane system Consists of endoplasmic reticulum (ER), Golgi

bodies, and lysosomes Compartmentalizes the cell

The Cytoskeleton Main types

Microfilaments (made of Actin)

Microtubules

Functions Maintain cell shape Locomotion – cilia,

flagella, and pseudopodia

Cell division Transport vesicles

around cell

Cilia Numerous, short projections

that beat in an oar-like fashion to produce movement

Consists of microtubule core (axoneme) enclosed in cell membrane Ring of 9 doublets, plus two

singlets, centrally located (9x2)+2 pattern

Anchored by a basal body

(9x3 pattern)

Flagella

Far fewer than cilia, but structurally identical

Long

Undulate in a whip-like fashion to produce movement

Both cilia and flagella require ATP to move

Pseudopodia Used for locomotion, food capture, and endocytosis

Actin disassembly results in a conversion of ectoplasm to endoplasm

Protozoan Physiology

Same rules apply in single celled organisms as do in metazoans

In fact, environmental effects may be more pronounced: Ectothermic Large SA : Vol Respiration is via diffusion

Important considerations Feeding and nutrition Enzyme function Osmoregulation Reproduction

Feeding and Nutrition

Heterotrophs

Photoautotrophs

Mixotrophs Can switch between

heterotrophy and autotrophy, depending on conditions

Endosymbiotic theory explains how energy producing organelles evolved

Nutrition occurs in four phases: Ingestion Digestion –mechanical

and/or chemical Absorption Elimination

Digestion typically intracellular. Food is phagocytized and a food vacuole is created. Digestive enzymes are dumped into vacuole

Osmoregulation

Many protists posses a specialized organelle known as a contractile vacuole

A collection of tubules known as the spongiome, collect ions from the cytoplasm and deliver them to the contractile vacuole

The vacuole contracts and its contents are extruded

Contractile Vacuole

Reproduction

Typically reproduce asexually

Fission – splitting of parent that results in two or multiple individuals

Budding – portion of parent splits off to form new individual

[note: hydra – not protozoan]

Though less common some species can even reproduce sexually

Conjugation two individuals fuse dissolve portions of their

cell membranes exchange genetic material

Asexual vs. Sexual

Advantages to clonal (asexual) reproduction Allows reproduction in the absence of a mate. Good for

isolated species

Allows offspring to be reproduced quickly; no energy is lost to gamete production, fertilization, or development

Perpetuates identical genotypes; beneficial if already well adapted to that environment

Disadvantage Limited genetic possibilities. Constricts the gene pool and

species could die out when the environment changes

Just for fun!

Advantages to sexual reproduction Increases genetic variability via crossing over,

independent assortment of chromosomes, and random fertilization

Result may be better environmental adaptability for certain individuals, and the species as a whole

Disadvantage Finding mates in isolated or sessile species

Protozoan Ecology

Very important ecologically

Many are photoautotrophs, and make up 40% of all primary productivity (dinoflagellates, euglenozoa)

Many make up a large component of plankton communities (foraminifera, radiolarians)

25% of the described species live as symbionts. Many of these are parasitic

Many are important players in nutrient cycles

KINGDOMS

Protista– Amoebozoa– Euglenozoa

Chromista– Dinozoa– Ampicoplexa– Others...

Phylum Ciliophora

Means: cilia bearing (know all of these 'translations'; and listing of defining characteristics!!!)

8000 described ciliates (fresh and salt water)

Have some degree of anterior – posterior polarity

Have two nuclei (macro: cellular; micro: repro)

Paramecium

Paramecium changes directions upon colliding with something solid Known as avoidance

reaction Result of Ca2+ and K+

release from alveoli Depolarization, similar to

an action potential

Specialized structures:

Trichocysts – long shafts that are thought to defend against predators

Toxicysts – longs shafts with toxin that are used for prey capture

Mucocysts – release mucus and creates sticky surface for prey capture or protective cysts

Ciliates have two types of nuclei Macronucleus – genes are actively transcribed Micronucleus – master copy of genome; inactive except during

cell division

Reproduction: conjunction

Phylum Dinoflagellata Dinozoa = Dinoflagellates

4000 marine and freshwater species

Posses chloroplasts Important 1° producers

Red-brown to gold-brown in color, due to photosynthetic pigments

Chloroplasts acquired through endosymbiosis

Contribute to planktonic bioluminescence

Some are endoparasites of protozoa, crustaceans, and fish

Certain genera responsible for “red tides.” May result in massive die-offs of shellfish and fish Harms animals who eat contaminated organisms

Posses a sulcus and two flagella

Have a skeleton known as a theca (or test)

Reproduce via binary fission, or may encyst (dormant stage)

Mostly parasitic (the cause of malaria)

Posses an apical complex Attaches to or penetrates

host cell Cone contains digestive

enzymes

Phylum Apicomplexa

Plasmodium – cause of malaria

Four species of Plasmodium that cause malaria #1 human parasite

300 million worldwide infected each year

1% die each year

Anopheles mosquito is the vector (DDT used to kill mosquitos)

Complex life cycle (two hosts) Sporozoite – motile, infective stage possessing apical complex

Merozoite – motile, reinfective stage, also has apical complex

Gametocytes – reproductive stage. Male and female gametocytes pair up and release gametes (sexual reproduction)

Spore – gametes pair to form zygotes, and a protective capsule is secreted

Complicated life cycle

Human | Mosquito

Sporozoites Injected into blood by mosquito Attack liver cells

Merozoites Derived from sporozoites Reinfect liver cells or move to red

blood cells (RBCs) Reinfect RBCs, in pulses

Cyclical merozoite release correlates with cyclical nature of malaria symptoms Chills Fever Fatigue due to loss of

hemoglobin Serious damage due to the

blocking of capillaries by infected (less pliable) RBCs

Amoebozoans

Three main groups of amoeboid protozoans Phylum Amoebozoa Phylum Foraminifera Phylum Radiozoa

Amoebozoans

Posses pseudopodia for locomotion and prey capture (heterotrophs)

Have a complex cytoskeleton

Marine, freshwater, and terrestrial species

Same type of cells found elsewhere in the animal kingdom Archeocytes of sponges Mammalian white blood cells (WBCs)

Diversity of pseudopodia Lobopodia – wide and

rounded Filopodia – slender and

may be branched

Freshwater species have one to several contractile vacuoles No need in marine

species

Some like Entomoeba histolytica are parasitic Causes dysentery

Phylum Amoebozoa

Phylums: Foraminifera & Radiozoa

Test (or shells) from both can be important contributors to marine sediments

Phylum Foraminifera

The forams

Mostly marine

Numerous reticulopodia (special filopodia) branch and interconnect to form reticulopodial network

May be benthic or planktonic, and there are structural differences between the tests of the two types Planktonic tests are more

fragile Also have spines to

increase surface area, and thus buoyancy

Foram tests (CaCO3) create natural wonders in the form of chalk and limestone

Pink sands of Bermuda White Cliffs of Dover in

England

Phylum Radiozoa

Marine

Mostly planktonic

Siliceous, spherical test

Large, up to 20cm in some colonial species

Planktonic

Spherical with a perforated test

Posses many axopodia Long, stiff, needle-like

pseudopodia

Have microtubule support rods

Can attach and retract

Used for flotation, locomotion, and hunting

Phylum Euglenozoa Elongate and

autotrophic

Free-living

Solitary

Reproduction is clonal, and occurs via longitudinal binary fission