11.4.2 Protists: Alveolata and Stramenopila

Question 1

Protists: Alveolata and Stramenopila

Answer 1

• It is likely that the common ancestor of the Eukaryotes was a protist.
• The Alveolata contain membrane-bound cavities called alveoli under their cell surfaces.
• Members of the candidate kingdom Stramenopila have plant-like characteristics and include diatoms, golden algae, brown algae and water molds.
• The candidate kingdom Rhodophyta is also known as the red algae.
• The green algae are very similar to plants but are currently classified in a separate candidate kingdom.

Question 2

note

Answer 2

• The transition from unicellularity to colonialism to
  multicellularity must have occurred at some point after the evolution of protists. The common ancestor of the domain Eukarya was most likely a protist.
• Remember, the word protist does not imply phylogenetic relationships. There are at least six candidate kingdoms that include protists. This tutorial covers four of these kingdoms: Alveolata, Stamenopila, Rhodophyta and the green algae.
• The candidate kingdom Alveolata includes the dinoflagellates, apicomplexans and ciliates.
• Dinoflagellates are autotrophic and contain a high
  concentration of the brownish-red pigment, xanthophyll. A harmful dinoflagellate, Pfisteria piscicida may have caused large fish kills in the mid-Atlantic states.
• The apicomplexans are characterized by an apicomplex, which is a specialized structure for burrowing into host cells. They are parasitic and a common example is Plasmodium sp., which is responsible for malaria.
• Ciliates are covered in cilia for motilitiy. A common example of a ciliate is Paramecium sp.
• The candidate kingdom Stramenopila include the diatoms, the golden algae, the brown algae and the water molds.
• Diatoms are the most common aquatic unicellular organism.
• They have beautiful glass-like shells that are made from silica.
• The golden algae contain yellow and brown pigments called carotene and xanthophyll. There are both heterotrophic and photosynthetic species of golden algae.
• The brown algae are commonly called seaweed. They are often multicellular as seen in the photograph of the brown algae, Macrocystis sp. shown on the left.
• Water molds are commonly called mildew. They have cell walls that are made of cellulose. An example is
  Saprolegnia sp.
• The candidate kingdom Rhodophyta is commonly called the red algae. They contain the red pigment phycoerythrin. They can be multicellular and their cells lack flagella.
• The green algae are quite similar to plants. There are both marine and freshwater species and they can be either unicellular or multicellular. A common example of green algae is the sea lettuce of the genus Ulva.

Question 3

Which of the following is not a member of the candidate kingdom Stramenopila?

Answer 3

• euglena

Question 4

____________________ have beautiful glass-like shells.

Answer 4

• Diatoms

Question 5

Macrocystis sp. are

Answer 5

• none of the choices is correct

Question 6

The ____________________ contain membrane-bound cavities under their cell surfaces.

Answer 6

• Alveolata

Question 7

Dinoflagellates contain high concentrations of the brownish-red pigment, ____________________.

Answer 7

• xanthophyll

Question 8

Saprolegnia sp. are

Answer 8

• water molds