Biology 106 Lecture Topic # 18: Diversity- Protista

I. Protist Diversity

A. Three of the most important events in the evolution of life occurred in Protists.

1. Origin of eukaryotic cell, 2. Evolution of multicellularity, 3. Sexual reproduction

B. Characteristics of Protists

1. Most diverse of all Eukaryotic Kingdoms

2. Most are small, single-celled organisms

3. Independent origins of multicellularity

4. over 60,000 Protists described

C. Symbiosis and the Origin of Eukaryotes

1. Mitochondria acquired early in history of Eukaryotes

a. perhaps from organism similar to bacteria

2. Chloroplasts

a. 3 different biochemical types each from a different kind of bacteria

b. each ancestral protist independently incorporated one of the three types

i. red algae derived from _________________________

ii. brown algae derived from ______________________

iii. green algae derived from ______________________

D. Multicellularity

1. true multicellularity only in Eukaryotes

2. allows novel adaptations to environment through division of labor.

E. Alternation between syngamy and meiosis

1. Zygotic Meiosis

- zygote only diploid stage of life cycle

- all other stages of life cycle haploid

- simplest life cycle of Protists

ex.

2. Sporic Meiosis

- alternation of generations

- multicellular diploid phase that produces haploid spores through meiosis

- multicellular haploid phase that produces haploid gametes through mitosis

- gametes fuse to form diploid zygote

ex.

F. Classification of Protists - Difficult!

1. Cellular Slime Molds -once thought related to fungi, - NOW most closely related to amoebas, - important w/r studying development of multicellularity and communication.

 

2. Green Algae - ancestors of all land plants, - about 7000 species, - unicellular & multicellular, - aquatic & semiterrestrial habitat, - colonial organisms, sheet like algae, - sporic meiosis - alt. of generations, ex.,__________________________________________________

 

3. Brown Algae - mostly multicellular marine organisms, - high degree of differentiation in specialized structures, ex._______________________________ - chlorophyll A and C, derived from heliobacterium, - well dev. alt. of generations (sporic meiosis)

 

4. Apicomplexa -2,400 species, - nonmotile, spore forming animal parasites, - exhibit organelles, - complex life cycles with sexual and asexual phases,ex.,____________________

 

5. Zoomastigina- 1,500 species, - unicellular, heterotrophic, highly variable, - most asexual, but some produce gametes & sexual reproduction, - 1-1000's flagella, - free living & parasitic forms, - many cause human disease, ex. _______________________________, spread by insects, - choanoflagellates likely ancestors of ALL animals.

 

6. Ciliates (Ciliaphora) - about 9000 species, any have cilia included here; two types of nuclei: (1) Macronucleus, (2) Micronuclei; can exhibit conjugation, ex. _____________.