IQ 1 - How did today's biosphere originate and develop?

Question 1

What is the story of the development of life?

Answer 1

Panspermia → Amino acids (the building blocks of life) have been found in asteroids, and the early Earth was bombarded with asteroids as it had no atmosphere. Therefore amino acids could have arrived to Earth this way

Spontaneous generation/Urey-Miller → The conditions of the early atmosphere actually produce amino acids all on their own

The Archaea and chemosynthesis → prokaryotic (single celled) microorganisms first began creating their own food

Photosynthesis and oxygenation → cyanobacteria (found in stromatolites) began photosynthesising, and releasing oxygen which subsequently turned the atmosphere oxic

Complexity, sex and size → Development of first Eukaryotic (multicellular) cells - bigger, more complicated organism
→ development of first multicellular organisms

Ediacaran Period → first soft-bodied organisms develop

Cambrian Explosion → development of hard bodies, ‘explosion’ of life

Conquest of land → Plants moved onto land first, and developed waxy cuticles to maintain moisture, strong and more developed root systems (vascular systems) to stay upright and obtain nutrients, and developed internal fertilisation (seeds cones)
→ Animals move onto land to avoid predators/competition and enjoy new food sources (plants), developed water-tight skin to stop drying out, developed internal fertilisation, hard eggs and internal embryo development, developed skeleton to counter gravity

Question 2

Describe the Urey-Miller experiment and its significance.

Answer 2

Urey and Miller simulated the conditions of the early atmosphere and within this environment amino acids were generated ‘spontaneously’.

The significance of this experiment is that it proved that the building blocks can spontaneously appear within the conditions of the early atmosphere.

Question 3

Explain the significance of Cyanobacteria and how Banded Iron Formations are formed

Answer 3

Cyanobacteria begin to photosynthesize and oxygen is released into the atmosphere. This is significant because it began to create an oxic atmosphere, without which life as we know it couldn’t exist.
This oxygen reacted to iron in the ocean and created the heavier iron oxide (rust) that sunk to the ocean floor creating layers of iron rich and iron poor material, over time these layers built up to form BIF’s

Question 4

What is the significance of BIFS?

Answer 4

BIFS allow us to tell when the oxygenation of the atmosphere by cyanobacteria first began, how long it occurred for – they start to tell part of the story of how our modern atmosphere was formed.

Question 5

Why is there much more fossil evidence after the beginning of the Cambrian period compared to before?

Answer 5

Before the Cambrian, during the Ediacaran, multicellular organisms only had soft-bodies, and did not fossilise very well.
The cambrian ‘explosion’ marks a period in which hard-bodies were developed. This enabled much more diversity in the biosphere, as hard bodies allow more creatures to survive.
However hard-bodies also fossilise a lot easier than soft bodies, and thus there is much more evidence in the fossil record of hard-bodied organisms after the Cambrian period.
Note: this does not necessarily mean that there was more life overall, just that it left more of a mark for us to find.

Question 6

Why was it impossible for life to move out of the ocean and onto land until around 530ma?

Answer 6

Life had only developed soft bodies and would have dried up in the sun if gone onto land, at around 530 Ma, the cambrian era began and life developed hard bodies and began to fossilize.
Also, without a protective layer in the atmosphere (ozone) to shield the earth from radiation, it was impossible for life to move out of the ocean (the ocean naturally protects against radiation).
Ozone is created when there is enough oxygen (its made of 3 oxygen atoms), and so oxygen had to oversaturate the oceans and then spread into the air before an ozone layer could be created.

Question 7

What are the difficulties that PLANTS had to overcome to move onto land (explain the difficulties and how they overcame them).

Answer 7

Avoid drying out/retaining moisture: waxy cuticle coating their leaves

Obtaining resources: Developed root system with vascular tubes to transport water from roots to leaves.

Staying upright/support: Strengthening vascular tubes with the chemical ligin - stronger root systems

Reproduction/fertilisation: developed methods for fertilisation that can survive dry conditions until the the ideal conditions arise e.g. seeds, cones

Question 8

What are the difficulties that ANIMALS had to overcome to move onto land (explain the difficulties and how they overcame them).

Answer 8

Staying upright/gravity: Developed supportive skeletons and hard bodies

Breathe air: developed lungs that were kept moist internally

Water loss/drying out: Water proof skin or exoskeleton

Reproduction (external fertilisation and eggs drying out): developed internal fertilisation, developed waterproof shells for eggs (reptiles) or internal development of embryo.

Question 9

What were the advantages of moving onto land for BOTH plants and animals?

Answer 9

Plants: the availability of a sunlight rich space which lacked competing organisms would have been the main advantage

→ first the plants move onto land, and now there is a new untapped food source/habitat for animals

Animals: began to move onto land to enjoy the food sources provided by plants as well as the lack of competition and predators

Question 10

What is one of the earliest plants that we know inhabited land. Describe it’s features.

Answer 10

One of the earliest land plants for which we have good fossils is called cooksonia from the Silurian period 420 Ma years ago.

It was covered with waxy cuticles to prevent water loss and had small pores in its stems to allow for gases to get in and out.

It evolved the ability to produce seeds (in cones) which could survive in dry conditions.

Question 11

Why were amphibians an essential step for animal progression onto land?

Answer 11

Amphibians can live close to and around land whilst still being water dwellers. They thus have the ability to move around on land whilst living and reproducing in the water. This means they were an important intermediary between the land dwelling animals we see today, as they were the first animals to begin developing the ability to move around on land without fully developing some of the features we see today (internal fertilisation, hard eggs etc). → they were the first ‘step’

Question 12

What features do reptiles have that enables them to survive better on land compared to amphibians?

Answer 12

• Dry, watertight skin
• Internal fertilisation
• Eggs with watertight shell
• Ways to control body temperature

Question 13

When was the Cambrian explosion?

Answer 13

542Ma

Question 14

What was the first Mass extinction? When did it happen? How many species died?

Answer 14

Ordovician, 444Ma, 86% of species lost

Question 15

What are the 4 types of fossils

Answer 15

True form fossils, Trace fossils, Mold fossils and Cast fossils

Question 16

What are true form fossils?

Answer 16

These fossils are made of an actual plant or animal. The hard parts of the body like the bones or stems were trapped in rock and effectively preserved. The soft parts of the body like the skin and muscle usually decompose before fossilization can occur.

Question 17

What are trace fossils?

Answer 17

Geological records of the activities and behaviors of past life. These fossils are different from body fossils that preserve the actual remains of a body such as shells or bones.

Question 18

What are mold fossils?

Answer 18

Mold fossils are hollow impressions left by a plant or animal. The surrounding mud and sediment hardens around the dead organism and only an imprint of it remains after decomposition.

Question 19

What are cast fossils?

Answer 19

Cast fossils occur when mold fossils are filled in with minerals that harden over time, creating a fossilized replica of the original organism. Water seeps through the rock surrounding the mold fossil, leaving behind minerals which fill the mold.

Question 20

What caused the Ordovician Extinction

Answer 20

Just as the first complex animals were settling into Earth’s oceans, oxygen levels fell dramatically and wiped many of them out.

Question 21

What was the second mass extinction? When did it happen? How many species died?

Answer 21

Devonian Extinction, 375Ma, 75% of species lost

Question 22

What were Trilobites?

Answer 22

Trilobites were the most diverse and
abundant of the animals that appeared
in the Cambrian explosion 542 million
years ago. Their great success was
helped by their spiky armour and
multifaceted eyes. They survived the first
great extinction but were nearly wiped
out in the second.

Question 23

What caused the Devonian extinction?

Answer 23

Lack of oxygen in the oceans, quick cooling of air temperatures, volcanic eruptions and/or meteor strikes

Question 24

What was the third extinction? When did it happen? How many species died?

Answer 24

Permian extinction (great dying), 252Ma, 96% of species lost

Question 25

What caused the Permian extinction?

Answer 25

possibly asteroid strikes, volcanic activity, climate change, and microbes

Question 26

What was the fourth extinction? When did it happen? How many species died?

Answer 26

Triassic extinction, 200Ma, 75% of species lost

Question 27

What caused the Triassic extinction?

Answer 27

Major volcanic activity with basalt flooding, global climate change, and changing pH (acidity) and sea levels of the oceans

Question 28

What was the fifth extinction? When did it happen? How many species died?

Answer 28

Cretaceous extinction, 66Ma, 76% of species lost

Question 29

What caused the Cretaceous extinction?

Answer 29

Extreme asteroid or meteor impact

Question 30

When was the Rodinia supercontinent?

Answer 30

1.1 - 0.7Bya

Question 31

When did Pangea exist?

Answer 31

230 - 280Ma