Lecture 2: Conquering the World

Question 1

What was around in the ‘Early Life’?

Answer 1

Bacteria
Energy from sun
Photosynthesis
Hydrogen sulphide from volcanoes
Hydrogen from water
Production of oxygen

Question 2

What are cyanobacteria?

Answer 2

Blue-green algae, prokaryotes, photosynthetic, unicellular and multicellular

Question 3

Brief timeline of the Earth

Answer 3

4,600 mya: Earth formed
1,200 mya: cyanobacteria and protists on land
500 mya: small plants and fungi colonise land
385 mya: tall plants appear

Question 4

Name a few challenges for organisms that abandoned life under water

Answer 4

-Desiccation of body tissues, requiring waterproof coating
Wax cuticle formed on plant, retaining water

-Respiration of gaseous exygen
Pores on leaves, stomata on vascular leaf where cells control open
and closing of pores

-Mechanical support
Cellulose and main constituent of cell walls & fibres
Lignin binds cells, fibres, vessels = wood
Hemicellulose adds strength to cell walls

-Transport water and nutrients
Stele: central cylinder, inside cortex, composed of vascular tissue
and associated tissues in roots and stems

-Reduce need for water for reproduction
Spore and seed walls protect from desiccation and UV light