Chapter 27: Protists

Protists

refers to all eukaryotes that are not land plants, fungi, or animals.

• can be found everywhere there is water

• ocean, lake, oceans, puddles, humans

• Important for ecology, human health, and evolution

Primary producers

represents about half of total global carbon fixation.

• photosynthetic protists take in carbon dioxide from the atmosphere and reduce, or “fix” it

Plankton

• primary producer

• diatoms and other tiny organisms that drift in water

• the basis of food chains in freshwater and marine environments

diatoms

photosynthetic protists

Impact to human health

Irish potato famine, sleeping sickness, and malaria

• Irish potato famine caused by phytophthora infections

• Sleeping sickness is caused by Trypanosoma species

• malaria caused by plasmodium species

Choanoflagellates

first animal cells with hard external shells

• frustule, theca, lorica, and pellicle

carbon sink

a long-term reservoir of carbon

• one of two carbon sinks

  • sedimentary rocks

  • petroleum oil

How do protists obtain food/energy?

Absorption or photosynthesis

• phagocytosis

• ingestive feeding

• absorptive feeding

• photosynthesis

ingestive feeding (protists)

based on eating live or dead organisms or on scavenging bits of organic debris

Absorptive feeding (protists)

nutrients are taken up directly from the environment

common among protists

• decomposers

  • feed on dead organic matter (detritus)

• parasite

  • an absorptive species that damages its host

Photosynthesis (protists)

Protists that engage in ingestive and absorptive feeding are heterotrophs

Lineages of Eukaryotes

1. amoebozoa

2. opisthokonta

3. excavata

4. plantae

5. rhizaria

6. alveolata

7. stramenopila (heterokonta)

alteration of generations

alternation of multicellular haploid and diploid forms

• gametophyte, sporophyte

• the multicellular haploid form is called a gametophyte

  • specialized cells in this individual produce gametes by mitotic cell division

• the multicellular diploid form is called a sporophyte

  • has specialized cells that undergo meiotic cell division to produce haploid cells called spores

spores

a single haploid cell that divides mitotically to form a multicellular haploid gametophyte.

Endosymbiotic theory

Propses that mitochondria originated when a bacterial cell took up residence inside another cell about 2 billion years ago. Gave rise to all plantae subgroups

1. Host cell surrounds and engulfs bacterium.

2. bacterium lives within host cell

3. endosymbiosis

   1. host cell supplies bacterium with protection and carbon compounds bacterium supplies host cell with ATP

   2. occurs when an organism of one species lives inside the cells of an organisms of another species

   3. accounts for the origin of mitochondria

Secondary Endosymbiotic theory

Chloroplasts are found in 4 protists (chloroplasts are surrounded by more than two membranes)

Manners of Motility

1. Amoeboid

2. Flagellates and Dinoflagellates

3. Ciliates

4. Heterokonts

Harmful Algae Blooms: HABs

Three main culprits:

• Cyanobacteria, Diatoms, and Dinoflagellates

  • chemical waste (P and N)

  • thermal pollution

  • low water levels

• leads to climate change

Amnesic Shellfish Poisoning (ASP)

domoic acid, life-threatening

Ciguatera Shellfish Poisoning (CFP)

ciguatoxin, temperature reversal

List of Toxins from HABs

• Amnesic Shellfish Poisoning (ASP)

• Ciguatera Shellfish Poisoning (CFP)

• Diarrhetic Shellfish Poisoning (DSP)

• Neurotoxic Shellfish Poisoning (NSP)

• Paralytic Shellfish Positioning (PSP)

• Microcystis

Amoebozoa

• Slime molds and amoebae

• lack cell walls

• extend pseudopodia to feed and move

• Love freshwater and wet soil

• Occasionally eat brains

Excavata

• Euglenids, Diplomonids, Parabasalids

• Excavated feeding groove on one side of cell

• euglenids

  • abundant in freshwater

• giardia and trichomoniasis

Plantae

• glaucophytes, reds, green, and land plants

• primary producers in most ecosystems

• some red algae form reef like structures

Rhizaria

• Foraminiferans (Forams), actinopods, radiolarians

• single-celled with NO cell walls

• move and feed by amoeboid motion

• The presence of shells can date sediments

Alveolata

• ciliates, dinoflagellates, and apicomplexans

• unicellular, some are bioluminescent

• flattened vesicles (alveolus) within plasma membranes

• Parasites responsible for disease- Apicomplexans

Stramenopila

• Diatoms, brown algae, and water molds

• Flagella with hollows hairs (at some stage of life cycle)