Protists

Question 1

Endosymbiosis

Answer 1

Occurs when one type of single cell organism lives within the cell(s) of another organism
Theory: mitochondria and chloroplasts - once prokaryotic cells - were engulfed by early anaerobic eukaryotic cells and incorporated into them

Question 2

Evidence of Endosymbiosis

Answer 2

1. Mitochondria & chloroplasts each have two membranes
2. Mitochondria & chloroplasts have their own internal chromosomes –> reproduce through binary fission

Question 3

Why are they important?

Answer 3

• Some perform photosynthesis (especially in the ocean)
• Seaweed is common in toothpaste, cosmetics, paints, foods (as additives too - agar & carrageenan)
• Nori on sushi is made of porphyra, a protist
• Many are parasites and live in/on other organisms
• Some cause diseases (ex. malaria, sleeping sickness, “Beaver Fever”)

Question 4

Animal-like Protists

Answer 4

Heterotrophs, unicellular, no cell walls, very motile (ex. amoebas, paramecium, euglena)

Question 5

Plant-like Protists

Answer 5

Autotrophs, have cell walls (ex. algae, volvox)

Question 6

Fungi-like Protists

Answer 6

Heterotrophs, live under rotting logs (ex. slime molds)

Question 7

General Characteristics

Answer 7

Huge range in size and can be unicellular or multicellular –> Some have:
- More than one nucleus
- Special vacuoles to expel water
- “Gullet”: mouth for food
- Cilia or flagellum for moving

Question 8

Reproduction

Answer 8

Can be asexual: binary fission
Can be sexual: conjugation (e.g. paramecia exchange micronuclei) –> multicellular protists like algae actually have male “sperm” cells and female “egg” cells (like plants)