Chapter 28: The Protists

Objectives

1. Most Eukaryotic Organisms are Multicellular

2. Realize Protista is Paraphyletic and no longer one single kingdom

3. Will understand Endosybiosis

4. Understand the variety of protists

5. Understand some ecological relationships of protists

Basics structures and functions of Protists-Recently found to be Paraphyletic – Diverse - Some protists are more closely related to plants, fungi, and animals then they are to other protists

-Exceptions to almost all characters

-Most are unicellular

-Many contain specialized organelles (Contractile vacuoule)

-Mixed nutritional means. (Photo, Hetero, and Mixo)

-Asexual and Sexual reproduction (3 basic types)

-Contain membrane bound organelles

Endosymbiosis-Evidence suggests Eukaryotic cells arose by endosymbiosis

-Mitochondria were thought to have been the first endosybiont

-Cyanobacteria were thought to be the next – Photosynthesis

-Secondary endosymbiosis is when a Eukaryotic cell engulfs another Eukaryotic cell.

p. 576

Current Understanding of Eukaryotic Organisms

1. 5 super groups of Eukaryotic organisms

2. Some protists are more closely related to animals then other protists.

3. Changes have come about due to better understanding of DNA, Cellular Components, and Cellular Chemistry

Excavata-Made up of three monophyletic groups

1. Diplomonads

2. Parabasalids

3. Euglenozoans

-Most have flagella – extensions of microtubules

-Diplomonads and Parabasalids have highly reduced mitochondria – No electron transport chain and can’t use Oxygen.

-Euglena are mixotrophs

Chromaveolates-Most diverse group of protists

-Thought to be monophyletic (DNA evidence)

-Origin was secondary endosymbiosis with a red algae

-Group includes:

1. Dinoflagellates (Red Tide)

2. Apicomplexan (Malaria)

3. Ciliates (Cilia – Paramecium)

4. Stramenophiles (Diatoms)

5. Golden Algae (Yellow/brown Caratenoid pigments)

(Some are multicellular)

6. Oomycetes (Water molds)

Rhizaria-Ameobas are not monophyletic

-Ameobas that belong to the Rhizaria group have thread like pseudopodia

Archaeplastida: Red and Green Algae-Group contains land plants

-Algae protists are the closest relative to plants

-Chloroplatasts are similar to land plants

-Use of Alternation of Generation much like land plants (p. 592)

Unikonta -Group contains both Animals and Fungi

-Includes Slime molds

-Other closely related protists are discussed in the animal chapter.

-Molecular and DNA evidence is the reason for going away from the protista kingdom