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BLGY1124 > Evolution of Photosynthesis and Algae > Flashcards

Evolution of Photosynthesis and Algae Flashcards

1
Q

Autotroph

Definition

A

organisms that sustain themselves without eating anything derived from other organisms
producers of the biosphere
they produce organic molecules from carbon dioxide and other inorganic molecules

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2
Q

Heterotroph

Definition

A

obtain organic material from other organisms

almost all of them depend on photoautotrophs for food and oxygen

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3
Q

What do photosynthetic organisms do?

A

convert light energy into chemical energy

the chemical energy is used for carbon skeletons and synthesis of molecules etc.

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4
Q

Chloroplasts

A
  • in leaves
  • solar powered chemical factories
  • contain chlorophyll
  • light is absorbed by the chlorophyll and used to synthesise organic molecules in the chloroplast
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5
Q

Where in the chloroplast do the light reactions of photosynthesis take place?

A

thylakoid membrane

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6
Q

Where in the chloroplast do the dark reactions / the calvin cycle take place?

A

in the stroma

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7
Q

In which types of organisms does photosynthesis occur?

A
  • plants
  • algae
  • prokaryotes
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8
Q

Evolutions of chloroplasts

A

-chloroplasts are similar to early photosynthetic bacteria

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9
Q

First photosynthetic organism

A

fossil finds and chemical evidence of organisms similar to cyanobacteria 2.5bya

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10
Q

Early Evolution of Photosynthesis

A

the presumed early evolution of photosynthesis is from anoxygenic photosynthesis

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11
Q

Origin of Carbon Fixation

A

Carbon isotope data suggests carbon fixation was occurring at east 1 billion years before the first photosynthesis

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12
Q

Anoygenic Photosynthesis

A
  • metabolic complexity and diversity developed in prokaryotes
  • produce ATP, take in CO2, no O2 production
  • only one photosystem similar to PS1
  • used photosynthetic pigments similar to chlorophyll called bacteriochlorophylls
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13
Q

Examples of Anoxgenic Photosynthetic Organisms

A

green sulphur bacteria
purple bacteria
heliobacteria

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14
Q

How did the transition from anoxygenic to oxygenic photosynthesis occur?

A

-when cyanobacteria learnt to use water as an electron donor (PS2)

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15
Q

How did the transition from oxygenic photosynthetic prokaryotes to oxygenic photosynthetic eukaryotes occur?

A
  • 2.5 billion years ago
  • primary endosymbiosis event
  • a photosynthetic cyanobacterium was ingested (and not degraded) by a eukaryotic cell
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16
Q

What happened after the primary endosymbiosis event in the evolution of photosynthetic organisms?

A
  • the ancestral eukaryote led to the evolution of algae
  • diversification of algae
  • the conquest of land
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17
Q

Photosynthetic Organisms

Purple Bacteria

A

prokaryotic
anoxygenic
electron donors = H2S, S, Fe2+

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18
Q

Photosynthetic Organisms

Cyanobacteria

A

prokaryotic
oxygenic
electron donor = O2

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19
Q

Photosynthetic Organisms

Algae

A

eukaryotic
oxygenic
electron donor = O2

20
Q

Photosynthetic Organisms

Plants

A

eukaryotic
oxygenic
electron donor = O2

21
Q

Atmospheric Oxygen

A

atmospheric oxygen is of biological origin

it is released in the hydrolysis of water in PS2

22
Q

Atmospheric Oxygen Levels Over Time

A

1.5bya - O2 revolution correlates with formation of eukaryotic cells containing chloroplasts
750mya - increase in oxygen with increase in abundance of multicellular photosynthetic organisms
350mya - emergence of large vascular plants in the carboniferous leads to 30% increase spike in O2 levels

23
Q

Multicellular Photosynthetic Life on Land - Problems With Carbon Dioxide

A
  • not enough CO2 in the vicinity of chloroplasts

- stomata appear to have been a very early innovation

24
Q

Photosynthetic Mechanism - Cyanobacteria vs. Land Plant Chloroplasts

A
  • essentially unchanged
  • no fundamental changes to the light reactions
  • BUT more efficient carbon chemistry
  • evolution of C4 and CAM photosynthesis
25
Q

C4

A
  • spatial separation of steps in the Calvin Cycle

- e.g. sugarcane

26
Q

CAM

A
  • crassulation acid metabolism
  • temporal separation of the steps in the Calvin Cycle
  • e.g. pineapple
27
Q

Algae - Evolutionary History

A
  • origin over 2bya
  • less than 1bya, all algae live in the ocean
  • 480mya, green algae make the transition tot land
  • eukaryotic
28
Q

Advantages of Algae Living in the Sea

A
  • protected from drying out
  • protected from UV radiation
  • protected from large fluctuations in temperature
29
Q

Macroalgae

A

seaweed (brown, red, green)
large, multicellular
rougly ressemble terrestrial plants but they aren’t related

30
Q

Microalgae

A

golden algae, dinoflagellates, euglenoids, diatoms

single celled

31
Q

Protists

A
  • algae, human parasites, omycytes
  • mostly unicellular
  • autotrophic and heterotrophic
32
Q

Green Algae

A
  • charophtes and chlorophytes
  • c.17 000 species
  • marine and freshwater
  • uni and multicellular
  • colonial - form lose ‘multicellular’ associations in some parts of life cycle
  • charophytes are the most recent common ancestor with land plats
33
Q

Red Algae

A
  • rhodophytes
  • c.5000 species
  • mainly marine
  • non motile
  • mostly unicellular but many multicellular
  • red, but still do oxygenic photosynthesis
  • most abundant large algae in tropical costal waters
34
Q

Brown Algae

A
  • phaeophytes
  • 250 genera, 2000 species
  • large, complex, multicellular
  • found in all colder seas and oceans
  • kelps - live in deep ocean
  • thallus - algal body
  • holdfast ~ roots
  • stipe ~ stem
  • blades ~ leaves
  • cell wall source = sulphated fulcans and alginate polysaccharides
  • most complex anatomy of all algae
35
Q

Algae

A
  • c. 70000 species
  • vast diversity in morphology
  • several groups of photosynthetic organisms that arose separately from non photosynthetic ancestors
  • multicellularity arose several times among algal groups
  • different cytoplasmic connections, not just plasmodesmata
36
Q

Euglenoids

A
  • 40 genera, c. 1000 species
  • unicellular
  • motile - flagella
  • mainly fresh water
37
Q

Diatoms

A
  • c. 12 000 specices
  • unicellular
  • 2 part box, highly sculpted
  • major component of phytoplankton
  • highly diverse
38
Q

Dinoflagellates

A
  • 550 genera, c. 3000 species
  • unicellular
  • planktonic
  • motile - flagella, 2 that spin to propel them through water
39
Q

Golden Algae

A
  • yellow / brown carotenoids
  • bi-flagellated
  • all are photosynthetic but some are also heterotrophic
40
Q

Similarities between green algae and land plants

A
  • cell walls containing cellulose
  • chloroplasts containing chlorophylls A and B
  • store food as starch
  • closest lineage to plants
41
Q

Chloroplasts in Green and Red Algae

A

derived from the primary endosymbiosis event 1bya

42
Q

Chloroplasts in Most Other Algae

A
  • 3-4 membranes
  • not close relatives of green plants
  • presumably acquired photosynthesis separately from red and green algae
43
Q

Secondary Endosymbiotic Event

A

a photosynthetic eukaryote was ingested by a non-photosynthetic eukaryote, resulting in a new photosynthetic eukaryote

44
Q

What are the three secondary endosymbiotic events?

A
  • engulfing of a cyanobacterium led to photosynthesis in archaeplastida
  • red alga -> chromalveolata
  • green alga -> excavata
45
Q

Classification of Organisms into Supergroups

A

Analysis of genomes led to the classification of organisms into the following groups:

  • excavata
  • SAR group (Chromalveolata and Rhizaria)
  • Archaeplastida
  • Urikanta
46
Q

Supergroups and Photosynthesis

A

There are three super groups that contain photosynthetic organisms:

  • excavata
  • chromalveolata
  • archaeplastida

BLGY1124 (8 decks)

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