CH 28 Protists

Protists

Diverse eukaryotic organisms not classified as fungi, plants, or animals.

(classified via exclusion)

Supergroups of Protists (5)

Major classifications of protists: Excavata, SAR, Archaeplastida, Amoebozoa, Opisthokonta.

Eukaryotes vs Prokaryotes

• presence of complex cytoskeleton

• compartmentalization (nucleus & organelles)

Proks 3.5BYA, Euks 1.5BYA

ER, nucleus & Endosymbiosis (1st & 2nd)

ER & nucleus arose from infoldings in prok. cell membrane

• 1st endosymbiosis: Big bacteria engulfed anaerobic bacteria (mitochondria)

• 2nd endosymbiosis: already developed Euk. engulfed green bacteria for plants

Evidence for Endosymbiosis

• DNA inside mitochondria & chloroplasts (circular DNA, similar to bacteria in size & character)

• Ribosomes inside mitochondria similar to bacterial ribosomes & vulnerable to antibiotics

• Chloroplast & mitochondria replicate by binary fission not mitosis (mitosis evolved in eukaryotes)

How do protists vary?

• Unicellular, colonial & multicellular groups

• Most are microscopic but some are huge

• Many forms & symmetries

• All types of nutrition

Cell Surface of Protists contain?

Protist have varied array of cell surfaces

• Plasma membrane

• Extracellular matrix (ECM) in some

• Diatoms & foraminifera-> silica shells

Cysts

• Dormant cells with resistant outer covering (analogous to endospores in proks)

• Used for disease transmission

Locomotion of protists via...?

Flagella; one or more

Cilia; shorter & more numerous than flagella

Pseudopodia ("false feet"); chief means of locomotion for amoebas; used by other protist as well

Nutrition of Protists (3)

Autotrophs

- Some photosynthetic

- Some chemoautotrophic

Heterotrophs

- Chemoorganotrophs

- Phagotrophs (ingest particulate food matter)

Mixotrophs (both phototrophic & heterotrophic)

Reproduction of Protists

Asexual Repro; typical mode, but under stress can be diff.

- mitosis, budding, schizogony

Sexual Repro; under stress (major Euk. innovation)

Budding

Asexual reproduction producing one smaller daughter cell.

Schizogony

Multiple nuclear divisions before cell division, producing many cells.

How are protist a bridge to multicellularity?

Single cells-> colonies-> true multicellularity

- Allows for specialization

(Few innovation have had as great an influence on history of life)

Excavata (supergroup)

Asymmetrical appearance w/ feeding groove "excavated" from one side

- includes phylum Diplomonads (ex. Gardia) & Euglenozoa (ex. Euglenids) & parabaslids

Gardia (of super group & phylum?)

- unicellular & 2 haploid nuclei

- lack functional mitochondria

- use cytosolic pathway (reparation genes) via horizontal gene transfer from bacteria

Protist - Excavata - Diplomonads

Diplomonads (of supergroup?)

phylum of excavata supergroup

• unicellular with multiple flagella

  • include ex. Gardia

• Lack functional mitochondria; use pathway derived from horizontal gene transfer from bacteria

Euglenozoa (of supergroup?)

phylum of excavata supergroup

• cells change shape while swimming

• Asexual

  • include ex. Euglenids (1/3 have chloroplasts & autotrophic)

  • Include ex. Euglean (2 unequal flagella & stigma for light detection)

Protist - Excavata

Euglenids (of supergroup & phylum?)

- have flagella

-contractile vacuoles & stigma

- chloroplasts & mitochondria

Protist - Excavata - Euglenozoa

SAR (supergroup)

- containts superphylums Stramenopila, Alveolata, Rhizaria

SAR: Stramenopila (of supergroup?)

Mostly single-celled, but some multicellular + very fine hairs on flagella (some species have lost hair via evolution)

• include Diatoms, Brown algae & Oomyce

Protists - SARs supergroup

Brown Algae (of supergroup & superphylum)

Conspicuous seaweeds

• multicellular & photosynthetic

• Haplodiplontic life cycle (sporophytes & gametophytes)

protist - SAR - stremenophila

Diatoms (of supergroup & superphylum)

• Photosynthetic unicellular

• unique double silica shells.

Oomycetes (of supergroup & superphylum)

Water Molds (not fungi)

• parasites/ saprobes [eat decayed matter]

(caused the Irish potato famine)

Protist- SARs - Stramenopiles

SAR: Alveolata (of supergroup?)

flattened vesicles called alveoli, may have apical complex (helps infect other cells)

• contains Dinoflagellates, Apicomplexans (ex. gondii), & Ciliates

Protists - SARs

Dinoflagellates (of supergroup & superphylum?)

• unicellular & photosynthetic

• Flagella (two that whirl around)

• bioluminescent sometimes

(red tide→ red pigmented dinoflagellates with toxins that are deadly)

protists- SAR - Alveolates

Apicomplexans (of supergroup & superphylum?)

Apical complex is a unique arrangement of organelles at one end of the cell (enables cell to invade host)

• parasites

• Plasmodium→ causes malaria; common in mosquito vector

protists- SAR - Alveolates

Ciliates (of supergroup & superphylum?)

Have large numbers of cilia in longitudinal rows or spirals around cell

• 2 nuclei (micronucleus/germline & macronucleus/function)

• 2 vacuoles (food & contractile for water)

protists- SAR - Alveolates

SAR: Rhizatia (of supergroup?)

silica shells

• contain Foraminnifera & Radiolarians

protist- SARs

Radiolarians (of supergroup & superphylum)

• Glassy exoskeletons made of silica, needle-like pseudopods.

protists- SAR - Rhizaria

Foraminifera (of supergroup & superphylum?)

Marine protists with pore-studded calcium carbonate tests.

• contribute to limestone formation

protists- SAR - Rhizaria

Archaeplastida (supergroup)

include red & green algae

Red Algar (of supergroup & phylum?)

• Red algae (have accessory pigments)

• lack flagella

• range from microscopic single celled to very large multicellular

protists - arceplastida

Green Algae (of supergroup?)

Has 2 lineages

• Chlorophyta (unusual diversity and specialization)

• charophytes (gave rise to land plants)

Protists - archaeplastida

Chlorophyta (Of supergroup & phylum?)

unusual diversity and specialization leading to multicellularity

Protists - archaeplastida - green algae

Charophytes (of supergroup & superphylum?)

Green algae lineage that gave rise to land plants.

• closest ancestor to land plants

Protists - archaeplastida - green algae

Amoebozoa (supergroup & phylum)

Move via pseudopods

• used to push organism forward & intake food

Amoeba (of supergroup & phylum?)

• Free living (found in soil & fresh water)

• some parasitic

(brain eating amoeba can cross blood-brain barrier causing inflammation and death)

Protists - amoebozoa

Opisthokonta (supergroup)

• contain choanoflagellates (closest living relatives to animals and fungi)

Chanoflagellates (of supergroup?)

• closest ancestor to animals & fungi (have matching structures to sponges)

• flagellum surrounded by funnel-shaped collar (feature in sponges)

Protists- Opisthokonta