Evolution - Lecture Three

Question 1

When and where did life arise?

Answer 1

• 4 billion years ago
• There was repeated bombardment causing water, destruction and high UV at the surface

Question 2

What was Darwin’s hypothesis on how life arose?

Answer 2

He theorized life began in a warm muddy pond on the Earth’s surface

Question 3

What theory seems more likely than Darwin’s hypothesis on how life arose?

Answer 3

Energy that fuelled the first replicating molecules might have come from proton gradients around hydrothermal vents

Question 4

What is the RNA world?

Answer 4

• The idea that before DNA based life forms, RNA were the first replicating molecules as the basis for reproduction and biochemical interaction
• However without DNA there shouldn’t be a cell, but to combat this there were tiny pores in rocks around vents
• Lipid protobionts can reproduce and metabolise, RNA can spontaneously reproduce within them

Question 5

How old is the universe, earth and life?

Answer 5

Universe = 14 billion years
Earth = 4.5 billion years
Life = 3.8 billion years

Question 6

What are some key features of eukaryotes?

Answer 6

• Have a nucleus, mitochondria, golgi bodies, sex and do phagocytosis

Question 7

What is Eukaryogenesis?

Answer 7

• The process where the defining features of a eukaryotic cell gave way to become present-day eukaryotes
• Happened once 2 billion years ago
• Probably from an archaebacterium engulfing a heterotrophic eubacterium which became a mitochondria which gave energy for complex life

Question 8

What is Eidiacaran biota?

Answer 8

• Signs of life as fossils from 570 million years ago showing how long ago life forms existed

Question 9

What are some examples of Eidiacaran biota?

Answer 9

• The spriggina, an annelid worm, anthropod
• Rangeomorphs, fern-like and fractally branched, living in the dark depths

Question 10

What is the cambrian explosion?

Answer 10

• An event causing many animals to burst onto the evolutionary scene
• Over a period of 20-30 million years
• Animal types we see now first appeared, eg arthropods, but some don’t fit into modern taxonomies

Question 11

What are some controversies about why the cambrian explosion occurred?

Answer 11

• Physiological change, where dissolved oxygen levels allowed for a more active lifestyle
• Geographical change, more seas and niches appeared
• Geochemical change, changes in sea levels leads to abundance of trace metals to make exoskeletons
• Biological change - increase in zoo plankton allows new predators to arise, increasing selection pressure