Algae Flashcards
(43 cards)
1
Q
Diazotrophic means:
A
Nitrogen fixing
2
Q
What type of cyanobacteria are nitrogen fixing?
A
- All heterocystous, some non-heterocystous
3
Q
What are heterocysts?
A
- Specialised cells that create an anoxic environment for the operation of nitrogenase, which is sensitive to oxygen
- Organisms living in anaerobic conditions can fix nitrogen without them
4
Q
Define: endosymbiosis
A
Where a single celled protist engulfs and retains a foreign photosynthetic cell, reducing it to a plastid
5
Q
What is the theory for how algae evolved?
A
- A cyanobacteria was engulfed by a phagocytic organism within a food vesicle, but was unable to digest it due to a mutation
- It provided beneficial metabolites to the host, the host provided a sheltered environment, and this composite organism could ecological niches without other photosynthetic organisms
- Cyanobacteria reduced to a plastid
- This occurred once, giving rise to the proto-alga that is the root of all plastids
6
Q
Dinoflagellates are a result of:
A
Tertiary endosymbiosis
7
Q
Brown seaweeds are a result of:
A
Secondary endosymbiosis of both red and green alga
8
Q
What is a diplont life cycle and which algae have it?
A
- Main phase is diploid, only zygotes are haploid
- All diatoms, some brown seaweed (order Fucales)
9
Q
What is a haplont life cycle and which algae have it?
A
- Main phase is haploid, fertilization produces a diploid zygote (planozygote) which acts as a resting stage in coastal sediments
- Under suitable environmental conditions the planozygote will emerge and undergo meiosis to give the haploid phase
- Seen in phylum Dinophyta (dinoflagellates)
10
Q
Explain the life cycle of Ulva
A
- Haplo-diplont, isomorphic alternation of generations
- Free living sporophyte and male/female gametophyte are identical, only sporophyte spores have 4 flagella and gametophyte spores have 2.
11
Q
Explain the life cycle of giant kelp
A
- Haplo-diplont, heteromorphic alternation of generations
- Sporophyte grows up to 60m tall in coastal waters, gametophyte grows as microscopic filaments on the rock surface
12
Q
Explain the life cycle of rhodophytes
A
- Triphasic
- Free living tetrasporophytes release 1n tetraspores
- Spores develop into free living male and female gametophytes, sperm is released, while egg is immotile
- Fertilized egg develops into a carposporophyte, which grows on the gametophyte and releases 2n carpospores
- Carpospores develop into tetrasporophyte
13
Q
Planktonic algae are:
A
Free floating in the water column
14
Q
Benthic algae are:
A
Attached to rock
15
Q
Where do diatoms live?
A
Surface water of coasts/oceans/lakes, vast majority are marine
16
Q
What are the two types of diatoms?
A
- Pennate diatoms - pen-like shape, pores arranged symetrically along longitudinal axis, live on a substrate (benthic), move and lay down mucus
- Centric diatoms - pores arranged in a radial pattern rather than a longitudinal pattern, planktonic, found in chains in the open ocean
17
Q
Explain what a frustule is, its features, and its role in reproduction
A
- Glass box created as a “shell” for diatoms, impregnated with silica
- Composed of a larger epitheca and smaller hypotheca
- Contains pores called areolae to allow essential gases + nutrients in and out
- The two halves split apart during asexual reproduction and a new hypotheca forms
- When they become too small they undergo sexual reproduction via a diplont life cycle
18
Q
What are the external features of dinoflagellates?
A
- No cell wall, instead covered in proteinaceous thecal plates
- Composed of an epitheca and hypotheca, which are separated by a cingulum/girdle that goes around the cell body
- A transverse flagellum is located in the cingulum
- A longitudinal flagella is located in a groove called the sulcus
- These two flagella work like helicopter propellors to give it vertical and horizontal movement
19
Q
Where dinoflagellates live?
A
- Restricted to coastal systems because their haplont life cycle has a resting cyst phase in marine sediments
- Form dense blooms
- Undergo daily vertical migration to the surface during daylight, to deeper water at night for a greater nitrogen supply (nitrogen is a limiting nutrient)
20
Q
What are kleptochloroplasts?
A
Chloroplasts stolen from other algae by dinoflagellates that begin life with no chloroplasts
21
Q
What causes bioluminescence?
A
- Molecule called luciferin, found in Noctiluca scintillans, set into action by motion of waves breaking or a potential predator
- Hypothesized that this acts as an alarm to attract other animals that will attack dinoflagellate predators
22
Q
What pigments and cell wall polysaccharides are found in red seaweeds?
A
- Chlorophyll a and phyco-billiproteins
- Agar and carrageenan
23
Q
What is the role of agar and carrageenan in rhodophytes?
A
Make the seaweed thallus flexible to withstand waves
24
Q
What is in the walls of coralline algae?
A
Calcium carbonate
25
How old are red seaweeds?
Fossil evidence from 1.2 bya
26
How many species of red seaweed are there?
6,500-10,000, 65% of all seaweeds
27
How old are brown seaweeds?
23-25 mya, much more recently than red/green
28
What pigments and cell wall polysaccharides are found in brown seaweeds?
- Chlorophyll a, beta carotene, fucoxanthin
- Alginate
29
What are some commercial uses of red seaweeds?
- Agar for agar plates or gelatin substitute, carrageenan as a food stabiliser e.g. icecream, toothpaste
- Neither can be synthesized artificially
30
What are some commercial uses of brown seaweed?
- Alginate is useful for absorption in wound dressings, also in dentistry for moulding around teeth
- Grown as food in Japan, Korea, China
31
What pigments and cell wall polysaccharides are found in green seaweeds?
- Chlorophyll a and b
- Cellulose
32
What is the smell produced by rotting brown seaweed?
Dimethyl sulphur
33
What role do brown seaweeds play in the environment?
- Kelp are ecosystem engineers that create habitat
- Provide important spawning grounds for marine organisms
- Play a large role in coast l systems by supplying the detrital food web, being ground up by sand and eaten by filter feeding shellfish
34
Where are chlorophytes often found in great abundance?
- Large blooms form in eutrophic (nutrient enriched) coastal regions due to farming and urbanisation
- Ulva in particular can form rafts metres deep, and likes to grow around sewerage outflows / stormwater drains
35
What is codium?
- A single celled coenocytic algae, the largest single celled organism
- Can repair itself in 15 minutes if damaged
36
Give an overview of the morphological features of seaweeds
- Thallus, a vegetative body that lacks distinct parts, can range from blade-like to filamentous
- Holdfast attaches to rock surface
- Stipe raises photosynthetic parts closer to the surface for maximum PS in many red and brown seaweeds
- Green seaweeds are morphologically simpler than red + brown
- Brown seaweeds in order Fucales and Laminariales have bladders/pneumatocysts to keep the thallus upright for light harvesting
37
Do red seaweed have flagellae at any stage?
No
38
Do green seaweed have flagellae at any stage?
Yes, microscopic stages have flagellae
39
Do brown seaweed have flagellae at any stage?
Yes, brown seaweed and diatom microscopic stages have one long hairy flagellum and one short smooth flagellum, Heterokont = different flagella
40
What is marine snow?
- Sinking particles made of dead/dying phytoplankton, primarily diatoms
- Diatoms have sticky glue-like structures that aggregate into clumps, become heavy, and start to sink in the water column
- Very important for the ocean's biological carbon pump
- Important source of carbon for bacteria, which consume all the sugars
- As it reaches the deep ocean, the remainder is recalcitrant and takes milennia to start to degrade
41
Diatoms are a result of:
Secondary endosymbiosis
42
Chlorophytes are a result of:
Primary endosymbiosis
43
Rhodophytes are a result of:
Primary endosymbiosis
