Evolution of Algae PDF

Evolution of Algae Dr.R.D.A.Gunasekara Department of Botany University of Ruhuna  The first organisms that developed oxygenic photosynthesis are thought to have been the anoxygenic ancestors of cyanobacteria (Allen & Martin, 2007) Estimates based on geol...

Evolution of Algae Dr.R.D.A.Gunasekara Department of Botany University of Ruhuna  The first organisms that developed oxygenic photosynthesis are thought to have been the anoxygenic ancestors of cyanobacteria (Allen & Martin, 2007) Estimates based on geological and geochemical evidence and molecular phylogenetic analyses calibrated with the fossil record agree on a minimum age of 2.3 billion years ago (Tomitani, Knoll, Cavanaugh, & Ohno, 2006)  With oxygen becoming gradually available as a very potent electron acceptor, the path lay open for aerobic organisms to evolve. Aerobes soon managed to maintain much more productive ecosystems and formed more complex organisms in the planet. The rising atmospheric oxygen is thought to have directly triggered cellular 2 H2O + COcompartmentalization  and 2 eukaryogenesis. O + CH O + 2 2 H2 O  Origin of Plastids: Primary Endosymbiosis Even though there is still considerable debate regarding the precise mechanisms and sequence of events that resulted in the first eukaryotic cell (de Duve, 2007; Embley & Martin, 2006; Martin & Muller, 1998; Poole & Neumann, 2011; Roger, 1999). There is a general consensus that photosynthetic eukaryotes emerged from a heterotrophic eukaryote which engulfed a cyanobacterium. eukaryote engulfed a cyanobacterium Ingestion of a cyanobacterium Incorporation of the cyanobacterium as a chloroplast  The cyanobacterium was gradually enslaved and integrated into the cellular machinery as a new organelle: the plastid. This event has been termed primary endosymbiosis. In this way the green algae like complex organisms origin Three extant groups of photosynthetic eukaryotes have primary plastids:the green plants, red algae and the glaucophytes. Together they make up the Archaeplastida.  Following the origin of Archaeplastida, photosynthesis spread widely among diverse eukaryotic groups via secondary and tertiary endosymbiotic events (Archibald, 2009; Gould et al., 2008; Keeling, 2010). In that way brown and red algae origin Evolutionary tree  Cyanobacteria (Blue Green Algae) they are photosynthesis Prokaryotes they are ancient life forms known as bacteria what are prokaryotes? no nucleus no chloroplasts no mitochondria dividing cell  What are the different between the Prokaryotes and Eukaryotes/ algae? Prokaryotes Eukaryotes nuclear materials not nuclear materials in contained within nucleus nucleus no chromosome or nuclear chromosome are formed membrane and surrounded by nuclear membrane no mitochondria or mitochondria in most plastids cells, plastids in plants and some flagellates ribosomes small ribosomes small (70 S Type) (80 S Type)  What are the different between the Prokaryotes and Eukaryotes? Prokaryotes Eukaryotes nuclear materials not nuclear materials in contained within nucleus nucleus no chromosome or nuclear chromosomes are formed membrane and surrounded by nuclear membrane no mitochondria or mitochondria in most plastids cells, plastids in plants and some flagellates ribosomes small ribosomes small (70 S Type) (80 S Type)  What are the different between the Prokaryotes and Eukaryotes? Prokaryotes Eukaryotes nuclear materials not nuclear materials in contained within nucleus nucleus no chromosome or nuclear chromosomes are formed membrane and surrounded by nuclear membrane no mitochondria or mitochondria in most plastids cells, plastids in plants and some flagellates ribosomes small ribosomes small (70 S Type) (80 S Type)  What are the different between the Prokaryotes and Eukaryotes? Prokaryotes Eukaryotes nuclear materials not nuclear materials in contained within nucleus nucleus no chromosome or nuclear chromosomes are formed membrane and surrounded by nuclear membrane no mitochondria or mitochondria in most plastids cells, plastids in plants and some flagellates ribosomes small ribosomes small (70 S Type) (80 S Type) Prokaryotes Eukaryotes cell wall usually contains Peptidoglycan absent peptidoglycan nuclear division not by nuclear division usually chromosome or nuclear by mitosis or meiosis membrane sexual reproduction is no sexual reproduction but common this process in some bacteria flagellum has flagellum, when present characteristic 9+2 does nt have 9+2 structue structure (9 outer & 2 inner) some can fix nitrogen non can fix nitrogen e.g.-bacteria & blue green e.g.-All other plants and algae animal Prokaryotes Eukaryotes cell wall usually contains Peptidoglycan absent peptidoglycan nuclear division not by nuclear division usually chromosome or nuclear by mitosis or meiosis membrane no sexual reproduction but sexual reproduction is this process in some common bacteria flagellum has flagellum, when present characteristic 9+2 does nt have 9+2 structue structure (9 outer & 2 inner) some can fix nitrogen non can fix nitrogen e.g.-bacteria & blue green e.g.-All other plants and algae animal Prokaryotes Eukaryotes cell wall usually contains Peptidoglycan absent peptidoglycan nuclear division not by nuclear division usually chromosome or nuclear by mitosis or meiosis membrane no sexual reproduction but sexual reproduction is this process in some common bacteria flagellum has flagellum, when present characteristic 9+2 does nt have 9+2 structue structure (9 outer & 2 inner) some can fix nitrogen non can fix nitrogen e.g.-bacteria & blue green e.g.-all other plants and algae animal Prokaryotes Eukaryotes cell wall usually contains Peptidoglycan absent peptidoglycan nuclear division not by nuclear division usually chromosome or nuclear by mitosis or meiosis membrane no sexual reproduction but sexual reproduction is this process in some common bacteria flagellum has flagellum, when present characteristic 9+2 does nt have 9+2 structue structure (9 outer & 2 inner) some can fix nitrogen non can fix nitrogen e.g.-bacteria & blue green e.g.-All other plants and algae animal Prokaryotes Eukaryotes cell wall usually contains Peptidoglycan absent peptidoglycan nuclear division not by nuclear division usually chromosome or nuclear by mitosis or meiosis membrane no sexual reproduction but sexual reproduction is this process in some common bacteria flagellum has flagellum, when present characteristic 9+2 does nt have 9+2 structue structure (9 outer & 2 inner) some can fix nitrogen non can fix nitrogen e.g.-bacteria & blue green e.g.-All other plants and algae animal Common characteristic features of the algae Algae diversity range from tiny unicellular microalgae to giant seaweeds which can grow over 50 m. The are defined as unicellular or multicellular photosynthetic organisms. Algae do not possess specialized root, stem, nor vascular bundles. They lack diploid embryo stage. They lack sterile tissue around its reproductive structures. Zygote development is by mitosis or meiosis but not via embryo formation Rhodophyta ( Red Algae)  General characteristic features Abundant & diverse in warm tropical and subtropical areas. Some common in temperate and polar seas. Hot springs algae – some unicellular forms. Critical role in coral reef building (encrusting, calcified corallines), consolidation role. Carbonate deposits from overlaid red algae with calcium carbonate in cell walls – global role in carbon storage. Deepest growing photosynthetic eukaryote (>210 m, Bahamas). Some parasitic forms – on macro algae (even other reds). 6,000 spp. – 97% marine, 3% freshwater,