Protists

1
Protists
2
What is a protist?

• All (some say the first) eukaryotes
• They are a very diverse group
• Most are unicellular
• Many are multicellular
• Many are microscopic
• A single cell can be 1 meter long
• Autotrophs and heterotrophs
• Sexual and asexual reproduction

3
Classification

• Based on what the organism is not!!!
• If you are eukaryotic and not a fungus, plant or
  animal
• Then you are a protist
• Active field of systematics, cladistics and
  taxonomy

4
Evolution again

• Evolution of eukaryotes
• Appearance of internal membranes
• Appearance of symbiosis (mutualism)
• Re-read section 3-4

5
Evolution of sexual reproduction

• Chromosome shuffling during meiosis
• Crossing over during meiosis
• Leads to increase in genetic variation
• Remember all this???

6
Autotrophic Protists

• Algae
• Perform 40 of the photosynthesis on earth
• Red algae, green algae, brown algae
• More later in Chapter 24

7
Heterotrophic Protists

• Commonly called protozoans
• Most are uniclellular
• Can be predators, decomposers or parasites

8
Four Phyla of Protozoans

• Based on how they move
• Use flagella (Flagellates, Zoomastigina)
• Example Trichonympha in Termite gut
• Example Typanosoma causes African sleeping
  sickness
• Illustration on page 536

9
Four Phyla of Protozoans

• Based on how they move
• Use pseudopods, false feet (Sarcodines,
  Sarcodina)
• Example Ameba
• Example Forams (Foraminifera)
• Illustration on page 537

10
Four Phyla of Protozoans

• Based on how they move
• Use cilia short hairs (Ciliates, Ciliophora)
• Example Paramecium
• Ciliates have
• Micronucleus and macronucleus
• Contractile vacuole (osmosis)
• Gullet, anal pore, trichocysts
• Binary fission normally, conjugation when
  stressed
• Illustration on page 538

11
Four Phyla of Protozoans

• Based on how they move
• Use nothing, i.e., dont move (Sporozoans,
  Sporozoa)
• Example Plasmodium
• Causes malaria, uses two hosts
• Mosquitoes and birds or mammals

12
Fungus-like Protists

• Slime molds
• Life mostly as solitary creatures, looks
  ameba-like
• In stress attracts others to form a giant mass
• Produces fruiting body cells
• Produces spores and disperse the spores in the
  wind

13
Protist Reproduction

• No generic life cycles
• Most use sexual reproductive strategies
• Algae show alternation of generations
• One generation is diploid (sporophyte)
• Next generation is haploid (gametophyte)
• Next generation is diploid and so on