BIOL 2P93 Lecture Notes - Lecture 1: Cyanobacteria, Green Algae, Chlorophyta
4 May 2018
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Lecture 1: Chapter 15: Algae Part 1 03/05/2018
• Algae
o Classified in Kingdom Protista
o A group of aquatic, photosynthetic, eukaryotic organisms
o unicellular to multicellular forms
o possessing chlorophyll but lack true roots, stems, leaves which are characteristics of terrestrial plants
o 30,000-1,000,000 extant species
▪ Uncertain to # of species present
o Scientists are divided as to what algae is or what constitutes an algal species
o 15 Algal phyla (Guiry, 2012)
▪ Distinguished by physical/molecular characteristics, i.e. chlorophyll, food reserve products, cell
coverings & reproductive features
▪ Common Phyla
• Cyanophyta (Blue-Green Algae)
• Rhodophyta (Red Algae)
• Euglenophyta (Euglenoids)
• Chlorophyta (Green Algae)
• Pyrrophyta (Dinoflagellates)
• Green Algae (Chlorophyta)
o Significant as extant vascular plants derived from green algal ancestor
o Note there are heterotrophic protists
▪ Feed on organic materials from other plants/animals
• Algae can be small, but they have substantial evolutionary
importance!
• Algae: Evolutionary Importance
o Life 1st began ~3.5 bya w/ the appearance of prokaryotes
o Oldest fossils interpreted as eukaryotic algae
▪ Based on consistent size & form are those of Grypania spiralis
• ~2.1 byo
o Bangiomorpha pubescens (red algae)
▪ 1st known sexually reproducing organism
▪ Multicellular fossil from Canadian Arctic resembles modern red
algae despite occurring in rocks ~1200 mya
▪ Has unbranched filaments
▪ Oldest fossil assigned to a modern algal group
o Modern day descendants of early eukaryotic algae grow in a range
of conditions
▪ Extant algae primarily found in aquatic enviro
▪ Diverse aquatic habitats include:
• Bogs, marshes, swamps (including saline areas)
• Lakes, rivers (including saline areas)
• Hot springs
• Sewage ponds
• Dams
▪ Algae thrive in terrestrial enviro
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▪ Diverse terrestrial habitats include:
• Tropical forests, snow, mud, sand, rocks
• Animals i.e. turtles, snails, rotifers, worms, crustaceans, alligators, sloths
o Three Toed Sloths are covered in algae and its fury provides a mini ecosystem for moths
and microorganisms
▪ https://www.youtube.com/watch?v=80rHf2l6dTk
o Early green algae could organize complex, differentiate multicellular bodies
▪ Some moved onto land
• Ancestors of the Embryophytes or true plants
▪ Because most animals/plants we are familiar are multicellular/terrestrial, perhaps we dot
appreciate just how complex these phenomena are
▪ Consider that organisms spent about 1 billion years at the unicellular level of organization; among
algae true multicellularity evolved only a few times
▪ Try transitioning to having a complex photosynthetic body capable of living on land…soethig so
difficult it seems to have happened only once!
o Green Algae (Phylum Chlorophyta) have incredible development & metabolic plasticity, they are
resilient & survive disturbances
▪ Due to metabolic tolerance to ecological changes, they can live in fresh water, soil, air, inside
animals
▪ Diverse structurally & well-defined biochemically
▪ Past hypotheses on their evolution primarily based on vegetative & morphological characteristics
(Lewis & McCourt, 2004)
▪ Higher taxa now recognized on the basis of ultrastructural features
• Cellular structures visible at higher magnifications i.e. flagella or lack thereof
o Ultrastructural focus on 2 different microtubuler organizations found w/n Green algae during
cytokinesis
▪ First: Phycoplast
• Collapse of spindle apparatus after mitosis w/ microtubules oriented in the same direction as
the plane of cell division
▪ Second: Phragmoplast
• Development of persistent telophase spindle & cleave furrow, w/ microtubules oriented at
right angles to plane of cell division (Bhattacharya, and Medlin, 1998)
▪ Charophytes & land plants have phragmoplast whereas Chlorophytes have Phycoplast
• Led to the division of the Green Algae & land plants into 2 groups based on cytokinetic
character
o Green algae classification has occurred -> 2 major lineages
▪ Lineage One
• Chlorophyte algae or Chlorophyta sensu stricto
o Algae that have all characteristics that we expect from green algae
• Ancestral flagellates in Class Prasinophyceae
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