Chapter 28: Protists - structure, function, diversity, evolution, impact Protists (Chapter 28) 1. More structural and functional diversity than any other

Chapter 28: Protists - structure, function, diversity, evolution, impactProtists (Chapter 28)

1. More structural and functional diversity than any other group of organisms…

2. Most are unicellular, some colonial and multicellular…

3. Most nutritionally diverse eukaryotes

C. mixotrophs – combine photosyn with hetertrophic nutrition

A. photoautotrophsB. heterotrophs

Chapter 28: Protists - structure, function, diversity, evolution, impact

Broken into three general categories based on ecological context:

1. Photosynthetic (plant-like) protists

3. Absorptive (fungus-like) protists

- algae

2. Ingestive (animal-like) protists

- protozoans

Protists


How did such incredible diversity arise?

Protists

Many species resulted from two rounds of endosymbiosis…

Chapter 28: Protists - structure, function, diversity, evolution, impactPhylogeny of protists Fig. 28.4

Phylogenetic tree showing the major clades of protists.


A complete branch of a phylogenetic tree. Above how many clades are highlighted?

What’s a clade?

Two, the blue and the red because these are complete branches. The green is not complete.


Let’s examine a handful of these clades…

Chapter 28: Protists - structure, function, diversity, evolution, impactKingdom Euglenozoa Fig. 28.8

Characterized by spiral or crystalline rod within flagella in addition to 9+2 arrangement of microtubules.

Cyrstalline structure has unknown function.


Phylum kinetoplastid

- Causes sleeping sickness

- Spread by African tsetse fly- Fatal if untreated

Ex. Genus Trypanosoma

- Evade immune system by repeatedly changing the proteins on the surface of the cell


Phylum euglenid

- Found in freshwater

- Photoautotroph if sunlight available otherwise heterotroph by absorbing nutrients from environment (mixotroph)

Ex. Euglena



Chapter 28: Protists - structure, function, diversity, evolution, impactKingdom Alveolata Fig. 28.8

Characterized by sacs below membrane called alveoli having yet unknown function


Phylum dinoflagellates

- Abundant as both marine and freshwater phytoplankton

- Bloom (explosion of growth) can cause “red tide”

Kingdom Alveolata

Phytoplankton – phyto = photosynthetic, plankton = “free-drifting”

- free-drifting photosynthetic organisms (cyanobacteria is also a large part of phytoplankton)

- Secrete toxins that bioaccumulate in molluscs making them dangerous to eat

- Have internal “plates” of cellulose giving its characteristic shape…


Phylum Ciliates

- Obviously use cilia to move and feed

- Can have more than one of each

Kingdom Alveolata

Two types of nuclei

- Large (macro) nucleus

- Smaller (micro) nucleus

Ex) Paramecium


Phylum Ciliates

- Arranged in small units each having many duplicates of a single gene

Kingdom Alveolata

Macronucleus

- Contains dozens of copies of genome

- Genes are not on chromosomes (they don’t have chromosome)

- The gene products (i.e. proteins) control daily functions like feeding, waste removal, etc…


Phylum Ciliates

- Food vacuoles fuse with lysosomes

Kingdom Alveolata

Feeding

- Mainly on bacteria, which are moved through oral groove and phagocytosed at “cell mouth” into food vacuoles.

- Undigestable material is egested when lysosomes fuse with cell membrane


Phylum Ciliates

Conjugation

Kingdom Alveolata

Reproduction

- Mostly asexually by “binary fission”

- two organisms exchange haploid micronuclei (see fig 28.12b above and use book for more detail)

- Genetic diversity, NOT REPRODUCTION




Phylum Diatom (Bacillariophytes)

Kingdom Stramenopila

- Unicellular Algae

- Protection from predators

- glass-like silica based cell wall as shown in figure

- Withstand pressures up to 1.4 million kg/m2 (pressure applied by the leg of a table with an elephant standing upon it)


Phylum Diatom (Bacillariophytes)


Reproduction

- Sexual reproduction is not common, but does occur

- Usually asexually by mitosis

- Estimated 100,000 species

Diversity

- Major component of phytoplankton in oceans and lakes


Phylum Golden Algae (chrysophytes)


(chrysos = golden)

- Freshwater and marine plankton

- Contain yellow/brown cartenoid pigments

- All obviously photosynthetic, some species mixotrophs

- Most unicellular, but some, as shown, are colonial

Dinobryon


Phylum Brown Algae (phaeophytes – guess what phaeo means…)


- All are multicellular and most are marine (salt water – ocean)

- Largest and most complex algae (its what you call seaweed)

- Common along temperate costs like ours

Kelp


Phylum Brown Algae


- The body of the seaweed that is plant-like

Thallus Kelp

- Basically, the holdfast, stipe (stem-like) and blades (leaf-like) (see above)

- root-like structure at base solely for anchoring, not absorption like roots of plants

Holdfast

Sea palm (Postelsia)

Chapter 28: Protists - structure, function, diversity, evolution, impactPhylum Brown Algae


This is important to understand because as you might guess, since plants evolved from multicellular algae, they also do this.

Life-cycle: Alternation of Generations

- The two generations are structurally different as opposed to being isomorphic

Heteromorphic

Laminaria (a brown algae)



Chapter 28: Protists - structure, function, diversity, evolution, impactKingdom Cercozoans and Radiolarians

- Amoeba with threadlike pseudopods

- Amoeba is a general term for a protist that uses pseudopodia to move and feed. There is no one clade or kingdom that consists of amoebas

Chapter 28: Protists - structure, function, diversity, evolution, impactKingdom Cercozoans and Radiolarians

Foraminiferans (Forams) Radiolarian

- Named for porous shells called tests

- Foramen means “little hole”

- Organic molecules hardened with CaCO3

- Pseudopodia extend through pores of shell and fx in test formation, swimming and feeding

- Pseudopodia called axopodia

- Tests made of silica

Both of these phyla consist of amoebas because…



Chapter 28: Protists - structure, function, diversity, evolution, impactKingdom Amoebozoans

- Amoeba with lobe shaped rather than threadlike pseudopods belong to this clade:

Now this amoeba belongs to the above kingdom…


Phyla: Gymnamoeba

Phagocytosis of a ciliate:


Phyla: Slime Molds (mycetozoans)

Two major types:

Were once thought to be fungus hence the name, but molecular evidence has revealed convergent evolution

1. Plasmodial Slime Molds

2. Cellular Slime Molds

They in part by their life cycles…



Plasmodial Slime Mold Life Cycle



Cellular Slime Mold Life Cycle



Chapter 28: Protists - structure, function, diversity, evolution, impactKingdom Rhodophyta

Rhodo = red

Red Algae

Red due to pigment known as phycoerythrin, which masks chlorophyll

Most large and multicellular, living in tropical waters

Alternation of Generations

Chapter 28: Protists - structure, function, diversity, evolution, impactKingdom Chlorophyta

Chloro = green

Green Algae

Much like plants, systematics has shown close relationship b/w green algae and plants as you would expect…

Two groups

1. Chlorophytes

- More than 7,000 species, most in fresh water- Simplest are unicellular

- These are the ones that live in mutualism with fungus to form lichen

Watermelon snow showing the incredible diversity of chlorophytes

- Chlorophytes and Charophyceans

*Charophyceans and most related to land plants and are discussed at beginning of Ch. 29 with plants


Chloro = green

Green Algae

Larger size and complexity arose via:

1. Colony formation (ex. Volvox) and multicellular filament formation.

2. Repeated division of nuclei without cytoplasmic division (ex. Caulerpa)

3. True multicellular forms with cell division and differentiation (Ex. Ulva)


Chloro = green

Green Algae

Complicated life cycle of asexual and sexual stages:

Syngamy = fusion of gametes, aka fertilization/conception


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Chapter 28: Protists - structure, function, diversity, evolution, impact Protists (Chapter 28) 1. More structural and functional diversity than any other