Protists Chapter 29

Question 1

List the characteristics shared by eukaryotes that distinguish them from bacteria and archaea.

Answer 1

Protists are a diverse group of organisms that includes all eukaryotes except the land plants, fungi, and animals.

Question 2

With reference to synapomorphies, explain why protists are a paraphyletic group

Answer 2

[*] No synapomorphies define the protists. There is no trait that is found in protists but no other organisms.

live surrounded by water

Question 3

Discuss how protists impact human health with a brief outline of malaria and red tides.

Answer 3

• Malaria - parasitic protist called Plasmodium. specialized for infecting host cell
• algal blooms occur when dinoflagellates, toxin-producing protists, reach high densities in an aquatic environment. impacts humans b/c concentration too much

Question 4

Explain the ecological importance of protists in aquatic food chains and the global carbon cycle.

Answer 4

1/2 CO2 is fixed by primary producers via photosynthesis - carbon sink

Without protists, most food chains in freshwater and marine habitats would collapse

Question 5

How did the advent of electron microscopy lead to major breakthroughs in understanding the diversity of protists?

Answer 5

expanded our understanding of how many of these little suckers there are

Question 6

Through morphological and DNA sequence comparisons it appears that Eukarya can be divided into two broad monophyletic groups. Name these two groups and the key feature that distinguishes between them.

Answer 6

1. the group Plantae includes the green plants
2. the group Opisthokonta includes the fungi and animals.

Question 7

What is direct sequencing and what has been discovered since it was directed at protists?

Answer 7

discovery of several new lineages of eukaryotes, tiny protists the size of bacteria.

Question 8

What four features characterized early eukaryotic cells?

Answer 8

1. single-celled organisms
2. with a nucleus and endomembrane system,
3. mitochondria
4. cytoskeleton, but no cell wall.

Question 9

Contrast the structure and motion of the eukaryote flagellum with the prokaryote flagellum.

Answer 9

1

Question 10

Discuss the evolution of the nuclear envelope.

Answer 10

The leading hypothesis for the origination of the nuclear envelope (and the endoplasmic reticulum) is that it is derived from the infoldings of the plasma membrane.

Question 11

What are the proposed steps in the evolution of the mitochondrion?

Answer 11

endosymbiosis theory proposes that mitochondria originated when a bacterial cell took up residence inside a eukaryote about 2 billion years ago.

• The eukaryotic cells used their cytoskeletal elements to surround and engulf smaller prey.
• Instead of fusing with a lysosome and being digested, an engulfed bacterium began to live inside a eukaryotic cell.
• The engulfed cell survived by absorbing carbon molecules with high potential energy from the eukaryotic cell and oxidizing them, using oxygen as a final electron acceptor.

Question 12

Describe five features of mitochondria that are consistent with the theory that mitochondria are endosymbiotic in origin.

Answer 12

1. Mitochondria are about the size of an average bacterium and replicate by fission, as do bacteria.
2. Mitochondria have their own ribosomes to manufacture their own proteins.
3. Mitochondria have double membranes, consistent with the engulfing mechanism.
4. Mitochondria have their own genomes with genes that code for the enzymes needed to replicate and transcribe their own genomes.

Question 13

Provide three examples of the diversity of composition of hard outer coverings in protists.

Answer 13

• Diatoms are surrounded by a glass-like cell wall.
• Dinoflagellates have a cell wall made up of cellulose plates parabasalids have a unique internal support rod.
• euglenids have a collection of protein strips located just under the plasma membrane.

Question 14

Multicellularity arose in many independent lineages of protists. Even some bacterial species can be said to be multicellular. In what eukaryote lineages did multicellularity independently arise?

Answer 14

1

Question 15

Differentiate between ingestive feeding and absorptive feeding in protists.

Answer 15

• Ingesting packets of food compounds by ingesting food through plasma membrane or parasitizing other organisms.
• Others Performing photosynthesis.

Question 16

Provide evidence for the endosymbiotic origin of the chloroplast in the Plantae lineage of protists.

Answer 16

• that the chloroplast, originated when a protist engulfed a cyanobacterium.
• the photosynthetic bacterium provided its eukaryotic host with oxygen and glucose in exchange for protection and access to light.
• evidence for an endosymbiotic origin for the chloroplast is even more persuasive than that for mitochondria.

Question 17

Primary endosymbiosis is responsible for the chloroplasts in the Plantae lineage of eukaryotes. However, photosynthetic organelles also are found in some lineages of Excavata and Rhizaria; as well as in the Alveolata and Stramenopila. Explain the process of secondary endosymbiosis that is responsible for the existence of chloroplasts in these lineages.

Answer 17

Secondary endosymbiosis occurs when an organism engulfs a photosynthetic eukaryotic cell and retains its chloroplasts as intracellular symbionts. The chloroplasts from secondary endosymbiosis are surrounded by four membranes instead of two.

Question 18

Describe three types of cellular motion in the protists.

Answer 18

• Amoeboid motion is a sliding movement observed in some protists that is accomplished by streaming of pseudopodia
• The other major mode of locomotion involves swimming via flagella or cilia.

Question 19

Which Protists display these key features? Small sacs under plasma membrane, unicellular

Answer 19

Alveolata

Question 20

Which Protists display these key features? Flagella covered with hairs, unicellular to multicellular

Answer 20

Stramenopila

Question 21

Which Protists display these key features? Excavated feeding groove, lost or reduced mitochondria

Answer 21

Excavates

Question 22

Which Protists display these key features? Lack cell walls, engulf food, pseudopodia

Answer 22

Amoebozoa

Question 23

Which type of Protist is the following example from? Red Algae: aquatic phototrophs, absorb blue and green light Green Algae: aquatic phototrophs, absorb red light

Answer 23

Plantae

Question 24

Which type of Protist is the following example from? Amoebas: aquatic, unicellular Cellular Slime Moulds Plasmodial Slime Moulds: decomposers in forests

Answer 24

Amoebozoa

Question 25

Which type of Protist is the following example from? Oomycota: filamentous detritivores, parasites, example Phytophthora Diatoms: unicellular phototrophs, silica cell wall Brown Algae: multicellular phototrophs, example kelp

Answer 25

Stramenopila

Question 26

Which type of Protist is the following example from? Diplomonadida: aquatic, example: Giardia sp. Euglenida: unicellular phototrophs and heterotrophs

Answer 26

Excavata

Question 27

Which type of Protist is the following example from? Cilata: unicellular, covered with cilia, example Paramecium Dinoflagellata: cause red tides Apicomplexa: malaria parasite Plasmodium

Answer 27

Aveolata: Ciliata

Question 28

morphological features as __________________—shared, derived traits that are used to distinguish major monophyletic groups.

Answer 28

synapomorphies

Question 29

______________ have unusual flagella covered with hollow hair-like structures.

Answer 29

Stramenopiles

Question 30

Based on diagnostic morphological characteristics the group ____________ includes the fungi and animals

Answer 30

Opisthokonta

Question 31

Based on diagnostic morphological characteristics the group _________ includes the green plants

Answer 31

Plantae

Question 32

____________________ occurs when an organism engulfs a photosynthetic eukaryotic cell and retains its chloroplasts as intracellular symbionts.

Answer 32

Secondary endosymbiosis

Question 33

The multicellular haploid form is called a _______________, because specialized cells in this form produce gametes by mitosis.

Answer 33

gametophyte

Question 34

The multicellular diploid form is a _____________, because it has specialized cells that undergo meiosis to produce haploid cells called spores.

Answer 34

sporophyte

Question 35

A ______ is a single cell that develops into an adult organism but is not a product of fusion by gametes.

Answer 35

spore

Question 36

Protists are a paraphyletic grouping that includes all eukaryotes except ____________________________

Answer 36

the land plants, fungi, and animals.

Question 37

What key morphological innovations occurred as protists diversified

Answer 37

• the nuclear envelope,
• multicellularity
• an array of structures that function in support and protection.
• the mitochondrion and chloroplast arose by endosymbiosis.

Question 38

Can Protists reproduce both sexually and asexually?

Answer 38

yes

Question 39

___________ occurs when individuals of two different species live in physical contact

Answer 39

Symbiosis

Question 40

______________ occurs when an organism of one species lives inside an organism of another species.

Answer 40

Endosymbiosis