lecture 7- algae

Question 1

What are the characteristics of algae?

Answer 1

Eukaryotic
(Does not include the prokaryotic cyanobacteria, formerly called blue-green algae)
Contain a chloroplast
Perform photosynthesis
Contain chlorophyll a
Polyphyletic (no common ancestor)
Unicellular, colonial, filamentous, complex multicellular
Microscopic and macroscopic

Question 2

Describe algal size and cell arrangement

Answer 2

huge size range

Microscopic
Unicellular and colonial
As small as 0.8 µm (Ostreococcus tauri - the smallest free-living eukaryote)
Some are motile

Macroscopic
Multicellular: filamentous and complex
Brown algae can grow up to 0.5 metres/day and reach lengths of 80 m

Question 3

What environments are algae found in?

Answer 3

Fresh and marine waters
Found growing on/in rocks (endoliths), soils, plants and animals
Snow, ice and hot springs
Extremophiles
E.g. Acidophiles, thermophiles, cryophiles, halophiles, metallotolerant
Symbiotic – found growing inside/alongside other organisms

Question 4

Describe green algae

Answer 4

Archaeplastida super group
Primary endosymbionts
Most are near oblique autotrophs
Using photosynthesis to provide energy or can only catabolise simple substrates such as acetate
Symmetrical flagella (common for green and red algae)
Swims forward in a “breast stroke” manner
structurally diverse

Question 5

Describe red algae

Answer 5

Archaeplastida super group
Primary endosymbionts
Pigment phycoerythrin gives them a red pigment (not all red algae have this pigment)
Absorbs light efficiently in the green and blue
Unicellular, filamentous and multicellular
Coralline algae
Calcify their fronds and can become the foundation of coral reefs
Uses
Porphyra is used to wrap sushi
Produce valuable polymers called sulfated polygalactans that can be used to make agar and agarose used in molecular biology procedures

Question 6

What are coccolithophores and why do they calcify?

Answer 6

Unicellular calcifying marine algae
Secondary endosymbionts
Belong to a currently unclassified super group known as the “orphans”
calcify because:
Accelerated photosynthesis
Photodamage protection
Armour against attack
Viral/bacteria
Grazing
Ballast to modify position in water column

Question 7

What are diatoms?

Answer 7

Class Bacillariophyceae within the Stramenopile super group
Heterokonts have two dissimilar flagella
Unicellular
Secondary endosymbiont
Mainly found in saltwater but freshwater species are known
Major primary producer in the oceans
Account for 20% of global CO2 fixation: More than all of the world’s tropical rain forests
Estimated ~100,000 extant (living) species

Question 8

Describe diatom structure

Answer 8

Diatoms have silica cell walls called frustules
Bipartite silica (SiO2) shell called a frustule
Intricate pores in frustule to allow exchange of surrounding medium
Silicate frustules protect diatoms from grazing by amphipods and infection from viruses
Two main groups: centrics (radial symmetry) and pennates (bilateral symmetry)

Question 9

Describe the life cycle of a centric diatom

Answer 9

Each daughter cell receives one half of a frustule
A new frustule half is formed within the parental half
Results in a decline in size!
Meiosis and gamete formation

Question 10

Describe brown algae

Answer 10

Stramenopile super group
Multicellular
No vascular system (xylem/phloem) like plants
Gas bladder for buoyancy
Holdfast to tether to solid surface
Support important communities in marine ecosystems
Uses:
Fertilisers
Have alginic acid (alginate) in their cell walls which is used as a thickening agent in the food industry
Several edible species

Question 11

How can algae be used for biofuels?

Answer 11

Fast growing
Can be genetically engineered
Produces high levels of lipids

However, technical problems scaling from lab to field
Difficult to harvest products
High energy costs
Contamination
Cost effectiveness dependent on oil prices

Question 12

What are dinoflagellates?

Answer 12

Alveolate super group
Highly motile with two flagella
Secondary or tertiary endosymbionts
Amoured-plate appearance due to alveolar plates composed of cellulose
Many have horn like appendages to deter predators and to increase range of nutrient uptake
Photoheterotrophs
Predate on other plankton by engulfing them using a specially adapted pseudopod (phagotrophy)
Red tides
Due to production of a pigment called carotenoid
Produce toxins
Know as “dinotoxins” sveral which are neurotoxins that can be absorbed by shellfish that when consumed can be poisonous
Responsible for bioluminescence
Flow-agitated bioluminescence
Deterrent for predators by causing a a startled response
Attracts prey of predators
Oxidation of luciferin by luciferase releases energy as light