Origin and Diversification of Eukaryotes: Protists

Eukaryotic Cells

Nucleus and membrane bound organelles

Well developed cytoskeleton – structural support that lends to asymmetric forms

May have originated more than 2.7 bya, but 1.8 bya widely accepted

3 stages of diversity documented by fossil records

Initial diversification – 1.8 – 1.3 bya

Origin of multicellularity 1.3 bya – 635 mya

Emergence of large eukaryotes 635-535 mya

endosymbiosis

Symbiotic relationship in which one organism lives inside the bosy or cell of another organism.

DNA sequence data suggest that eukaryotes are “combination” organism from Archaea and Bacteria

Endosymbiont theory – mitochondria and plastids were formerly small prokaryotes that began living within larger cells. (See page 485)

Multicellularity

Colonies – collection of cells that are connected but show little or no cellular differentiation.

Multicellular organisms with differentiated cells – Algae, plants, fungi and animals

Characteristics

Most diverse kingdom eukaryotic., 1.5 bya Primarily unicellular/multicellular, heterotrophic/autotrophic Usually asexual, some sexual Found in water, damp soil and sand, leaf litter Some are parasitic 14 phyla

Characteristics

Characteristics first seen in Protista kingdom Sexual reproduction (varies, mitosis and

meiosis – usually in harsh enviro.) Multicellularity (coordination among

specialized cells) Complex flagella and cilia (as opposed to

simple seen in bacteria)

Protist diversity

Heterotrophic protists = protozoans, slime molds, water molds, parasites

Photosynthetic protists = Algae Some are classified further by how they

move: Amoebas – pseudopodia Ciliates – cilia, ex. paramecium Flagellates – flagella, ex. Euglena

Algae – Green, Red and Brown

Strict autotrophs, some multicellular Distinguished by type of pigment they contain Red

Multicellular, warm ocean waters Red pigment can absorb light in deep water

Brown Multicellular, marine Kelp, grows along coasts, food and shelter

Green Most freshwater, uni and multicellular Contains chlorophyll a and b

Green Algae

Phylum Chlorophyta Most unicellular, can be filamentous or

colonial Chlamydomonas – unicellular green algae Spirogyra – filamentous green algae Ulva – multicellular green algae (sea lettuce) Volvox – colonial (loose association of

independent cells) green algae

Red Algae/Brown Algae

Phylum Rhodophyta Economically important –

Agar Wrappings around sushi Emulsifying agent for production of chocolate

Phylum Phaeophyta Contain chlorophylls a and c and carotinoid Kelp, rockweed – grow along shoreline Harvested for human food and fertilizers Algin – pectin-like material added to icecream

Diatoms

Phylum Chrysophyta – includes golden-brown algae and yellow-green algae

Photosynthetic, significant part of phytoplankton, Important to food chain

Double shell made out of silica, like hat box Move by excreting chemicals through Diatomaceous

earth – abrasives

holes in shell Found in oceans and lakes

Dinoflagellates

2 flagella, cellulose plates Unicellular Most are marine, make up part of the

plankton, important food source, producers Some produce powerful toxins – “red tide”

Euglena

Freshwater, unicellular with 2 flagella Some photosynthetic with chloroplasts and

has ability to ingest food as well Pellicle – protein fiber inside cell membrane,

allows for flexibility and shape change Eyespot – light sensitive organ, toward light Contractile vacuole –

expels excess water

Zooflagellates

Mostly unicellular, hetertrophic protozoans Symbiotic and parasitic forms Trypanosomes – transmitted by tsetse fly

Causes African Sleeping Sickness Giardia lamblia – cysts from contaminated

water, intestinal wall, severe diarrhea Trichomonas vaginalis – STO, infects vagina

and urethra of women, prostate of males

Amoeba

Pseudopodia – false foot, cytoplasmic extensions

Food vacuole – food enters and moves throughout cell

Contractile vacuole – regulates water Entamoeba histolytica – amoebic dysentery

Forams

marine protist that lives in sand or attaches to other organisms

Tests – porous shells Thin projections of cytoplasm extend through

pores and aid in swimming

Paramecium

Freshwater streams and ponds Unicellular, heterotrophic Cilia to move Two nucluei

Macro – cell activities, includes DNA Micro –cell reproduction, contains

chromosomes

Sporozoans – parasitic protists

Form spores during their reproductive cycle Nonmotile, spore forming, unicellular

parasites Malaria – anopheles mosquito, pg 392 Toxoplasma gondii – toxoplasmosis,

during pregnancy,

can affect fetus

Slime molds - decomposers

Cellular slime mold, small Behave like amoebas Ingest bacteria During stress, form multicellular colonies

Plasmodial slime molds Mass of cytoplasm that looks like ooze,

colorful Eat bacteria and other organic material,

phagocytes

Water Molds

Filamentous decomposers Parasitic to plants and animals in ecosystems Cell wall contains cellulose, not chitin Usually have furry growths Responsible for potato famine in Ireland,

1840’s

Beneficial protists

Commensal protists that live in digestive tracts of humans and livestock (hay, cellulose)

Plankton – food, shelter, producers Largest group of photosynthesizers Abrasives Detritivores – recycle chemicals in

environment Symbiotic relationships - coral