lecture 3 - the origin of plants

Question 1

How many eukaryotic groups are there?

Answer 1

8

Question 2

How many of the eukaryotic groups are capable of photosynthesis?

Answer 2

6/8

Question 3

What were the endosymbiotic events that gave rise to eukaryotes acquiring photosynthesis?

Answer 3

(A) First endosymbiotic event - bacterium engulfed by another prokaryotic host, genes transferred to host genome, and conversion of engulfed cell to organelle - mitochondrion
B) Second endosymbiotic event - eukaryotic-like cell engulfs a prokaryotic photosynthetic cyanobacterium, transfer of genes to host nucleus, conversion of engulfed cell to organelle - chloroplast

-Eukaryotes acquired photosynthesis multiple times by repeated episodes of endosymbiosis

Question 4

How did eukaryotes acquire chloroplasts and mitochondria?

Answer 4

Endosymbiosis

Question 5

What is secondary endosymbiosis?

Answer 5

an algae (a photosynthetic eukaryote) is engulfed by a non-photosynthetic host cell, transfer of genes to host nucleus, conversion of engulfed cell to organelle

Question 6

What are the 3 clades endosymbiosis in early photosynthetic eukaryotic organisms gave rise to?

Answer 6

red algae, green algae and glaucophytes

Question 7

What was the effect of endosymbiosis?

Answer 7

contributed to increase in diversity and evolution of groups of multicellular organisms

Question 8

What are the key events in the evolutionary history of plants and other organisms?

Answer 8

photosynthesis
endosymbiosis
diversification
new characters
multicellularity
further diversification

Question 9

How many eukaryotic groups is multicellularity seen in?

Answer 9

3/8

Question 10

How did complex multicellularity spread through the oceans?

Answer 10

as the oxygen content of the atmosphere and oceans increased

Question 11

How did complex multicellular organisms radiate on land?

Answer 11

later than in the oceans - happened as one line of green algae adapted photosynthesis on land

Question 12

What is the effect of new character accumulation?

Answer 12

increases biological diversity

Question 13

What did plants evolve from and how did they evolve?

Answer 13

evolved from green algae - key features of early land plants were waterproof cuticle so they didn’t dry out, stoma for gaseous exchange, and sporangia (specialised reproductive spores as it is harder to release gametes in air than water)

Question 14

What was the effect of the appearance of land plants?

Answer 14

further and massive reduction in atmospheric CO2
gradual fall in temperatures
initiated a terrestrial ecosystem
triggered the evolution of terrestrial organisms
the adaptations of early plants were dramatic because they had to adapt to an entirely new environment

Question 15

What was the effect of atmospheric levels of CO2 falling?

Answer 15

reduced global temperatures and allowed plants to evolve larger, broader leaves
this further increased levels of atmospheric O2