Lecture 4/5: Protists

Question 1

Antoni van Leeuwenhoek

Answer 1

• developed hand held microscope
• allowed to view entire new biosphere previously hidden
• viewed a diverse group of unicellular organisms

Question 2

What are protists classified as?

Answer 2

eukaryotes (mostly single-celled)

Question 3

What do eukaryotes have that prokaryotes (archaea and bacteria) don’t?

Answer 3

A nucleus enclosed within the nuclear membrane

Question 4

Is it true that some protists are more closely related to plants/fungi/animals than other protists?

Answer 4

Yes, True

Question 5

Biologists now only use the term protists to refer to…

Answer 5

eukaryotes that aren’t plants/fungi/animals

Question 6

What’s the diversity of protists?

Answer 6

• very difficult to give key traits to protists, b/c so diverse
• most are unicellular but still some colonial/multicellular species
• single celled protist are considered the simplest eukaryotes, yet their internal cellular level are very complex

Question 7

What are some styles of acquiring nutrition that protists use? (Photoautotrophs, Heterotrophs, Mixotrophs)

Answer 7

PHOTOAUTOTROPHS:
-> use photosynthesis
HETEROTROPHS:
-> absorb organic molecules, ingest larger food particles
MIXOTROPHS:
-> use both photosynthesis and heterotrophic nutrition

Question 8

Photosynthesis rundown / eqn

Answer 8

• organism uses light energy to convert carbon dioxide and water into carbohydrates and oxygen
• needed for carbon fixation
  CO2 + H2O + light energy -> carbohydrate + O2

Question 9

Explain Carbon fixation

Answer 9

process of when carbon dioxide is converted into sugars

Question 10

Have protists always been able to photosynthesize?

Answer 10

No, they developed it. It is a process that has been passed around organisms during the diversification of eukaryotes

Question 11

What bacteria was the first to use oxygenic photosynthesis?

Answer 11

cyanobacteria

Question 12

Explain endosymbiotic theory (simple)

Answer 12

• theory explains how eukaryotes evolved
• suggesting that some of the cell’s organelles (mitochondria and chloroplasts) were once free-living
• but then, these organelles were swallowed/entered into larger cells
• instead of being digested, they underwent symbiosis, where the organelle provided energy and the host cell provided protection
• over millions of years these bacteria became permanent parts of the cell
• supported by the fact that mito and chloro have their own DNA and reproduce independently within the cell

Question 13

Protists live in almost any environment that contains…

Answer 13

liquid water

Question 14

What eukaryotic organism shares traits from both plants and animals?

Answer 14

Euglenoids

Question 15

Where could I find a Euglenoid?

Answer 15

fresh water ponds, soil, ditches (can only see with a microscope)

Question 16

What do euglenoids feed on?

Answer 16

bacteria or algae, make their own food by photosynthesis, or absorb nutrients from the water by osmosis

Question 17

What is a unikonta?

Answer 17

• supergroup of eukaryotes that includes a range of protists, animals and fungi
• ‘unikonta’ meaning one flagellum
• many are amoebas (any organisms that moves/feeds by extending out its plasma membrane, aka false foot)
• separated into 2 groups

Question 18

What are the ‘false foot’ by ameoba also known as?

Answer 18

pseudopods

Question 19

What are the two groups that unikonta is split into?

Answer 19

1. Amoebazoans: contains only protists
2. Opisthokonts: includes fungi/animal kingdoms

Question 20

What are the 3 taxa that comprise Archaeplastida (another supergroup of eukaryotes)?

Answer 20

1. Chloroplastida (green algae/land plants)
2. Rhodophyta (red algae)
3. Glaucophyta

Question 21

Why are rhodophyta (red algae) red?

Answer 21

b/c of the presence of the pigment phycoerythrin. it reflects red light and absorbs blue light

Question 22

Why is the red pigment helpful for red algae?

Answer 22

b/c blue light penetrates water to a greater depth than light of longer wavelengths, and these pigments allow the algae to photosynthesize and live at somewhat greater depths than most other algae

Question 23

Which group of algae is the most diverse?

Answer 23

green algae (more than 7000 species)

Question 24

What does paraphyletic mean?

Answer 24

(of a group of organisms) descended from a common evolutionary ancestor or ancestral group, but not including all the descendant groups.

Question 25

what’s a major difference between green algae and plants?

Answer 25

green algae are mostly aquatic organisms (live in water environments)

Question 26

why the term “algae”?

Answer 26

refers to ‘simple, photosynthetic’ organisms that live in water

Question 27

what type of protists are crucial in marine food webs? why?

Answer 27

photosynthetic protists, they are the base of the food chain and thus produce food for other organisms

Question 28

what are photosynthetic protists also known as?

Answer 28

‘marine producers’

Question 29

What impacts marine protists negatively (specifically their growth)?

Answer 29

rise in temperature