Kingdom Protista

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Kingdom Protista

Kingdom Protista

A very large and diverse group - comprising at least 16 phlya

A paraphyletic group - it does not contain all of the descendants

of the common ancestor of this group - some descendants are

multicellular - the fungi, plants, and animals

Many of the protists groups did not give rise to multicellular

organisms - at least 13 phyla have have remained single celled


Current classification is changing and likely to change greatly in

the near future.


Sixteen Phyla comprise the Kingdom Protista

classically grouped into 5 informal groups based on mobility and

nutrition - differs from evolutionary estimates of relatedness


Protistan Diversity

The Cell Surface

Amoebas lack a cell wall

Algae and slime molds encased in strong cell walls

Diatoms and Foraminiferans have shells of silica, calcium, debris

Locomotor Organelles

Many move by flagellar motions, or ciliary action, pseudopodial

movement - many are immobile

Nutrition

Phototrophs and Heterotrophs (phagotrophs (ingesters) and

saprobes)

Reproduction

Asexual reproduction by mitosis, fission, budding, spores

Sex by gametic meiosis, zygotic meiosis, or sporic meiosis


The Sarcodines - all can have pseudopodia

Phylum Rhizopoda - the amoebas

Phylum Actinopoda - actinopods, heliozoans

Phylum Foraminifera - forams


Phylum Rhizopoda - the amoebas

Heterotrophic

Fresh and salt water, abundant in soil, some parasitize animals

Reproduction by simple mitotic fission

No cell walls, flagella, sexual reproduction

Locomotion via pseudopodia

Pseudopodia also used for prey capture

Parasitic species may form resistant cysts

Entamoeba histolytica : Causes amoebic dysentery

Cysts resist digestion by host

Carriers exhibit no symptoms but can spread cysts

Spread through fecal contamination in food or water

may be dispersed by flies


Phylum Actinopodia - Actinopods -

silica (glass) skeletons covering most of cell

with many thin needlelike pseudopods that

project through pores


Phylum Foraminifera - Forams

Heterotrophic, marine organisms

Possess pore-studded shells called tests

tests: organic matter reinforced with inorganic

usually multichambered, often spiral shaped

material: often calcium carbonate, can use sand grains,

echinoderm plates, sponge spicules

Podia extrude through pores in test - used for swimming,

gathering material for test, feeding

White Cliffs of

Dover - chalk

formed from

deposited forams


Algae and other photosynthetic protists

Phylum Chlorophyta - green algae

Phylum Rhodophyta - red algae

Phylum Pheophyta - brown algae

Phylum Chrysophyta - golden algae

and diatoms

Phylum Pyrrophyta - dinoflagellates

Phylum Euglenophyta - euglenoids


Phylum Chlorophyta: Green Algae

Ancestors of all plants were multicellular green algae

green algae and plants use chlorophylls a and b, carotenoids

found in aquatic and semiterrestrial habitats

Unicellular and multicellular forms

Chlamydomonas is a

typical unicellular form

biflagellated

light sensitive eye-spot

zygotic meiosis with

zygospore resting stage


Some green algae are motile and

colonial like Volvox

Specialized reproductive cells give rise

to new colonies within the parent

colony

Has zygotic meiosis and zygospores

form within a parent colony.

Some green algae are

filamentous - like Spirogyra

named for its spiral

chloroplasts

Sex is through conjugation

of cells from + and - strains


Some green algae, like Ulva, form

multicellular sheets and have sporic

meiosis

Except for their ploidy,

the gametophytes and

sporophytes are very

similar


Phylum Rhodophyta - Red Algae

Most common coastal seaweeds - mostly multicellular, common in

warm waters

Chloroplasts have Chlorophyll a and phycobilins, like cyanobacteria

Absorb green, violet and blue light

Grow at greater depths than other algae

have sporic meiosis

Completely lack flagella

Body composed of interwoven filaments

An ancient group of eukaryotes

Economic importance

Some make sulfated polysaccharides like agar and carrageenan

Agar used as laboratory medium, a base for cosmetics, used in

baked goods and as a temporary preservative for meat and fish

Carrageenan used in paints, cosmetics and ice cream


Phylum Phaeophyta - Brown Algae

Mostly multicellular and marine

Conspicuous seaweeds, include kelps and Sargassum

Use chlorophylls a and c (like diatoms)

Photosynthetically productive - fast growing

Provide food for many animals

Some kelps grow up to 100 meters in length

Have sporic meiosis

sporophyte: large, conspicuous kelp-like form

gametophyte: small, filamentous form

separate male and female gametophytes


Phylum Chrysophyta - Diatoms and Golden Algae

Diatoms are photosynthetic, unicellular organisms

Double shells of silica - Resemble box with lid

Use chlorophylls a and c, and carotenoids

fossilize well - thick sediments of fossil

diatoms are called “diatomaceous earth”

Some move by secretions from shell

Asexual reproduction separates shell halves

each half produces new shell within old

one - become smaller with each division

Have gametic meiosis - cells are diploid

and produce sperm or eggs by meiosis

Golden Algae - use yellow and brown carotenoid pigments, and

xanthophyll accessory pigments

Unicellular, two flagella, often colonial, common in freshwater

Form resistant cysts when ponds dry out in summer


Phylum Pyrrhophyta - Dinoflagellates

Unicellular, photosynthetic, mostly marine, some bioluminescent

Distinctive flagella and coat

two flagella beat in grooves

coat composed of cellulose plates

Most use chlorophyll a & c and carotenoids

Some are symbiotic with animals

sea anemones, mollusks and corals

in corals - called “zooxanthellae”,

required for formation of coral reefs

Some forms cause “red tide”

large blooms result in red colored water

release toxins that kill fish and shellfish

consumption of poisoned fish can kill

Reproduce primarily asexually by longitudinal cell division with

nuclear mitosis - like fungi


Phylum Euglenophyta - Euglenoids

Mostly fresh water organisms

Group has characteristics of plants and animals

Some specimens are photosynthetic

use chlorophylls a and b, and carotenoids

Others lack chloroplasts and are heterotrophic

Some can transform from autotrophs to

heterotrophs and back, depending on

presence of light and food

Reproduction via nuclear mitosis and cell

division

No sexual reproduction known


Euglena is typical

Thin flexible pellicle lies within cell membrane - composed of

interlocking strips of protein

have two flagella - both

with bases in reservoir -

one is very small

Contractile vacuoles collect

and pump out excess

water at reservoir

have light sensitive stigma

paramylon granules are

for food storage


Heterotrophs with flagella or cilia -

Phylum Sarcomastigophora - Zoomastigotes

Unicellular, heterotrophic, highly variable in form

Possess one to thousands of flagella

Some free-living, some parasitic

Some reproduce asexually only

One group alternates between amoeboid and

flagellated stages

Some trypanosomes are human pathogens

cause sleeping sickness, East Coast fever,

Chagas' disease

many spread by insects, such as tsetse flies

Some inhabit guts of wood-eating insects

have enzymes capable of digesting cellulose

Choanoflagellates are similar to feeding cells of

sponges and are likely ancestors of all animals


Hiker's Diarrhea:

Caused by Giardia lamblia, found world-wide

Occurs in water, infects wild and domesticated animals, and

humans

Lives in small intestine of host

Spreads as cysts in feces, can survive for months in cool water

May appear in city water supplies

Resistant to treatment with chlorine and iodine, requires boiling

water to kill


Phylum Ciliophora - The Ciliates

Unicellular, heterotrophic, with many cilia

Coordinated beating provides motility

Outer pellicle is tough but flexible

Two types of nuclei

micronuclei - diploid - reserved for sex

macronuclei - polyploid - for normal

cellular metabolism

Specialized vacuoles ingest food and contractile

vacuoles regulate water balance

Food enters through gullet (cytostome) and

passes into vacuoles where it is digested


Asexual reproduction by transverse

fission

Sexual reproduction by conjugation

Two different mating types

exchange haploid micronuclei

Macronucleus in each individual

disintegrates

Multiple rounds of chromosomal

replications in micronuclei

reconstitutes macronucleus


Phylum Apicomplexa - Sporozoans

Nonmotile, spore-forming animal parasites

Have an “apical complex” at one end of cell - with fibrils,

microtubules, and vacuoles - used to enter host cells

Have complex life cycles with

sexual and asexual phases

Exhibit alternation of haploid and

diploid generations

Fusion of gametes produces a

thick-walled cyst, the oocyst

Meiotic divisions in oocyst

produce infective haploid

spores, sporozoites


Plasmodium causes malaria

Gametocytes

become

gametes in

gut of

mosquito

syngamy

forms zygote

and oocyst

meiosis in

oocyst forms

sporozoites


Malaria

estimated that 500 million infected, 200 million humans die

each year, most infected children die

symptoms include chills, fever, sweating, enlarged spleen,

confusion, thirst - repeating every 48 to 72 hours

Victims die of anemia, kidney failure, brain damage

Effects can be reduced with drugs

Focus is on eradication of malaria through elimination of

mosquito carriers

Vaccines against malaria may be available in near future


Slime Molds

Phylum Acrasiomycota - Cellular

Slime Molds

Phylum Myxomycota -Plasmodial

Slime Molds

Phylum Oomycota - water molds,

rusts, mildew


Phylum Acrasiomycota - Cellular Slime Molds

Once thought to be related to fungi

most closely related to amoebas

Common in fresh water, damp soil, rotting vegetation

Usually found as free

living amoebas

Sometimes cells aggregate

into motile slug

Slug transforms into

sorocarp,

within sorocarp some

amoebas fuse sexually

forming diploid

macrocysts

meiosis occurs in macrocysts - spores released form new amoebas


Phylum Myxomycota -Plasmodial Slime Molds

Consist of streaming multinucleate plasmodium

feeding phase may be yellow, orange or other color

Cytoplasm exhibits conspicuous streaming

Engulf and digest bacteria, yeast, bits of organic matter

forms sporangium under adverse conditions


Phylum Oomycota - water molds, rusts, mildew

Live in freshwater or soil, many are plant or animal parasites

Cell walls are composed of cellulose or similar polymers

Body consists of filamentous hyphae

Hyphae are diploid (unlike fungi) and produce gametes by meiosis

Exhibit normal mitosis (unlike fungi)

have unique life cycle


Diploid spores produced asexually in sporangium

Sex: female gametangium called oogonium with one to eight eggs

male gametangium called antheridium with many sperm

Fusion produces zygote that becomes thick-walled oospore

oospore germinates and forms new hypha

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