1 DEVELOPMENT OF THE BIOSPHERE

Question 1

Black smokers formation

Answer 1

Seawater circulates into oceanic crust through cracks and fissures
Seawater comes into contact with hot rocks heated by underlying magma
Heated water rises back to seafloor, carrying dissolved minerals and metals from rocks
Mineral-rich water is expelled from vents and rapidly cools upon contact with cold seawater
Minerals precipitate and form chimney-like structures

Question 2

Ediacaran fauna

Answer 2

o Earliest evidence of soft bodied multicellular life
o Immobile, had no eyes or skeleton and fed on algae and plankton.
o Jellyfish and segmented worms, were fossilised, they became trapped in fine silt (due to tidal flats) which eventually turned into stone and as sea levels changed.

Question 3

How does black smokers provide energy?

Answer 3

• The hot water surrounding the black smokers provides chemosynthetic archaebacteria with the energy to convert methane, hydrogen sulfide and carbon dioxide into glucose and sulfuric acid

Question 4

Where does food source come from in black smokers?

Answer 4

This glucose acts as a food source and forms the basis of the food web for organisms around black smokers, as it sustains and supports a range of specialised species, like molluscs, crabs and barnacles.

Question 5

How did life start in black smokers?

Answer 5

• It is proposed that life began on the ocean floor near hydrothermal vents, as chemosynthetic archaebacteria can survive without oxygen.

Question 6

Cambrian fauna

Answer 6

• Proliferation of new hard bodied, multicellular marine organisms
• The most widespread fossil was the trilobite, it was covered by a shield like structure, had segmented legs and crawled along the sea floor.
• The rise of hard parts, like exoskeletons and shells, indicate an evolutionary need for protection from predators.

Question 7

Conquest of land by animals

Answer 7

• Amphibians had porous skin that was prone to desiccation and reproduced via external fertilisation; their jelly-like egg needed to be deposited in an aquatic environment to prevent gametes drying out
• Reptiles conquered the land by developing scaly skin that conserves water. They lay amniotic eggs with a protective shell that allows them to reproduce on land and reproducing via internal fertilisation