Lecture 14, Chapter 18, Plant Diversity Biol 3601
Algae
· Importance
· Charactersitics
· Endosymbiosis
· Diversity – continue on Thursday
Planktonic algae and cyanobacteria are the base of aquatic food chains
· Freshwater food web
o Dinophyta
o Bacillariophyta
o Chlorophyta
o Chrysophyta
· Marine food web
o Dinophyta
o Bacillariophyta
o Cryptophyta
Kelp is harvested by people
· Top 3’ harvested
· Grows back quickly (6“ a day)
· 150,000 tons per year harvested off coast of CA
· Uses:
o Food
o Fertilizer
o Thickening agent, algin, 35% of kelp dry weight
Why is this sexy car paired with a unicellular algae?
· Fuel-cell engines combine H2 and O2 to produce H2O liberating energy in the process
· H2 obtained from natural gas
· From algae in the future?
· When starved of O2 and sulfur, C. reinhartdtii produces H2 at high levels for several days
o Chlorophyceae
o Chalmydomonas reinhartdtii
§ Page 399
What is algae?
· In “Kingdom” Protista
· Not a phylogenetic group
· Groups of eukaryotes that are:
o Unique
o More closely related to:
§ Animals
§ Fungi
§ Plants
§ Book covers “plant like”
§ algae
Protista is a bogus kingdom
· “Algae“ is a term of convenience
· Classification must change to describe natural groups
· Best hypothesis based on the synthesis of many gene trees
· Five “supergroups”
· Keeling 2004 on web page
Why is algal evolution so complex?
· The story is not so complicated over here
· Plante is a product of 1° endosymbiosis
Primary endosymbiosis
· Two membranes around chloroplast
o Bacterial cell membrane
o Residual membrane from phagocytosis
§ Fig. 18.1
Lineages that are products of primary endosymbiosis
Secondary endosymbiosis
· 3 (or 4) membranes around chloroplast
o Bacterial cell membrane
o Membrane from 1st phagocytosis
o Membrane from 2nd phagocytosis
o Plasma membrane of algal endosymbiont
§ Fig. 18.1
· Third membrane
o Called “chloroplast ER”
o Food vacuole of primitive heterotroph associated with ER (studded w/ ribosomes)
o Space between 2nd and 3rd is acidic allowing higher concentration of CO2
o Increased photosynthetic efficiency?
How do we discern relationships?
· Photosynthetic pigments
· Number of membranes around the chloroplast
· Molecular phylogenies
10 phyla of algae you need to know
· Artificial division for convenience
· Members of
o Excavates
o Chromalveoates
o Plante
· All have chlorophyll a
· Other chlorophylls and accessory pigments differ
· Different endosymbiotic histories
o Table 18.1
· Three classes of green algae
o Chlorophyceae
o Ulvophyceae
o Charophyceae
Euglenophyta -Euglenoids
· 800 species
· Most live in fresh water but near muddy bottoms
· Elaborate single cells
· Helical bands of protein under plasma membrane contract and allow directional movement
· No sex L
· Reproduce by cell division
o Fig. 18.2
Dinophyta – dinoflagellates
· 3000 marine and fresh water species
· Hard cellulose plates on exterior give characteristic shape
· Two flagella in grooves cause spinning
· ˝ or photo-synthetic or mixotrophic
· Some have green algae endosym-bionts
o Fig. 18.3