Diatoms

Question 1

describe diatoms as living snowflakes

Answer 1

• referred to this due to the intricacy of the different forms (there is high variety and diversity in this group)

Question 2

what is the most highly diverse species we have talked about

Answer 2

diatoms

Question 3

What is a frustule

Answer 3

diatoms have this protective glass like silicon dioxide cell wall, this takes less energy to produce than a cell wall and is an anti microbial/anti-herbivore device (even if they’re eaten they come back out intact)

Question 4

What is the similarity between diatoms and chrysophytes

Answer 4

• they alll have chl a + c and fucoxanthin
• their photosynthate storage product is known as chrysolaminarin

Question 5

Describe the morphologies of diatoms

Answer 5

1. radial centric diatoms (look like perfect circles)
2. raphid and araphid diatoms (raphid is the line dividing the center) - these are bilaterally symmetrical
3. bipolar and multipolar centric diatoms

Question 6

describe pennate diatoms

Answer 6

• they are bi laterally symmetrical
• common in freshwaters and typically attached to surfaces

Question 7

describe radial centric diatoms

Answer 7

• they have disc shaped frustules and exhibit radial symmetry
• are common in marine environments

Question 8

What does the raphe of raphe pennates of the diatoms do

Answer 8

it secretes mucus to move along surfaces - so these raphe pennates are called fast moving diatoms

Question 9

what are the fast moving diatoms

Answer 9

the raphe pennates that secrete mucus

Question 10

what are the two halves of the diatoms called

Answer 10

upper = epitheca/epivalve
lower = hypotheca/hypovalve

• the epitheca is the slightly larger half

Question 11

do diatoms have pores

Answer 11

yes they have a lot of pores

Question 12

what does the raphe do

Answer 12

divides the frustules of diatoms into symmetric halves and secretes mucus

Question 13

difference between striae and costae

Answer 13

striae is the little dots on diatoms while costae is more like continuous bands (ribcage look)

Question 14

which ones are older/more recent in the diatoms: radial or pennate

Answer 14

radial = older
pennate = more recent

Question 15

describe the gamete life history of centric diatoms and pennate diatoms

Answer 15

• centric diatoms produce haploid gametes and these look similar to chrysophytes - these gametes are motile
• pennate diatoms also go into a haploid state but these gametes are not flagelllated

Question 16

what analogy is used to talk about diatoms

Answer 16

the petri dish analogy - talks about how the frustule has the epitheca and the hypotheca

Question 17

are diatoms mixotrophic

Answer 17

yes