This document provides an overview of algae and its importance for Earth's atmosphere. It discusses how algae evolved oxygenic photosynthesis over 3 billion years ago which introduced oxygen into the atmosphere. It also describes how algae have played a key role in regulating carbon dioxide and oxygen levels in the atmosphere over time, influencing the evolution of life on Earth. The document outlines the major groups of algae and provides examples of important algae types, their structures, and impacts like red tides.

1. Algae: Overview and Importance for Earth’s Atmosphere

2. Earth’s Atmosphere: Not Much of It
Mass Atmosphere = 5.2 x 1018 kg
Mass Oceans = 1.4 x 1021 kg
Mass Earth = 6.0 x 1024 kg
Live Biomass = 1 x 1015kg
Carbon Dioxide = 3 x 1015 kg
Trunover Time for carbon dioxide =
5 years in atmosphere, centuries
in oceans

3. Carbon dioxide cycles between low values in summer and
higher values in winter in the Northern Hemisphere due to
seasonal differences in photosynthesis.
Annual input from fossil fuels and deforestation: 3 x 1013 kg
carbon dioxide. Half accumulates in the atmosphere, rest is
absorbed in oceans, leading to acidification.
Pre-industrial carbon dioxide level was 280 ppm, now 380 ppm.

4. Early Earth Atmosphere:
No Oxygen
Lots of Carbon Dioxide,
Methane, Water Vapor, Hydrogen

5. Cyanobacteria and Oxygenic Photosynthesis
About 3 Billion Years Ago. Water is the electron
donor. CO2 + H2O  CH2O + O2

6. Oxygenic photosynthesis is
complicated. It requires two
photosystems and is thought to
have arisen only once in the
course of evolution.

7. Modern Stromatolites Fossil Stromatolite (2.5
Billion Years Old)
Banded Iron Formation
Oxygen Was A Poison to Early
Life Forms on Earth. Took about 1
billion years before oceans and
atmosphere were fully oxygenated

8. Oxygen in the air allowed the evolution of eucaryotes and aerobic
respiration, finally leading to the world’s life forms present today.

9. Ozone in the upper atmosphere (derived from O2) protects against the splitting
H2O to H and OH, with H escaping to space.
Earth has lost about 25% of its water while water is nearly all gone on Venus and
Mars.
Oxygen also produced the ozone shield which protects water in the upper
atmosphere from boiling away as hydrogen

10. Greenhouse
Gasses:
Water Vapor
Carbon Dioxide*
Methane*
Nitrous Oxide*
*Increasing Due
To Human
Activity

11. Evolution of the modern algae orders.
60 Ma
1500 Ma

12. 600 Ma to
present –
evolution of
animal
kingdom

13. SNOWBALL
EARTH
1st - 2200 MYA
2nd – 850 MYA

14. Plate tectonics provides a resupply
of carbon dioxide to the atmosphere

15. Diatoms Grasses
50 MYA Diatoms and Grasses Reduce Carbon Dioxide to Very Low Levels

16. Evolution and impacts of algae on the atmosphere continue today…

17. In this course we emphasize the ecology and biology of the
algae rather than the taxonomy. Main groups we will cover:
Cyanobacteria (blue-green algae)
Green Algae
Red Algae
Brown algae – brown seaweeds, kelps, diatoms
Dinoflagellates
Coccolithophores
Others

18. Cyanobacteria Cell Structure

19. Nostoc filaments with N2-fixing heterocysts
Nostoc colony

20. Ceramium – filamentous red seaweed

21. Porphyridium – Unicellular Bangean Red Algae

22. Chlamydomonas

23. Ulva
Enteromorpha
Monostroma

24. Diatoms
Heterokont in sexual stage

26. Desmokont Dinokont
Dinoflagellates
Prorocentrum Lingulodinium

27. Red Tides

28. Coccolithophores
Haptophytes
w/ two smooth
flagella and
a coiled hapto-
nema
Emiliania huxleyi
Ca + 2HCO3 ---> CaCO3 + H2O + CO2