Lecture 3- A Brief History Of Life On Earth

Question 1

What are the 6 kingdoms of life on earth

Answer 1

• archaea, eubacteria, protists, fungi, plantae,animalia

Question 2

Out o f the six kingdoms, which are eukaryotes

Answer 2

Protists, plantae, animal, fungi

Question 3

Out of the six kingdoms, which are prokaryotes

Answer 3

Archaea, eubacteria

Question 4

Describe archaea

Answer 4

Prokaryotes lacking peptidoglycan cell walls

Eg. Methanogen

Question 5

Describe eubacteria

Answer 5

-Prokaryotes with peptidoglycan cell walls

Eg. Cyanobacteria, pathogens

Question 6

Describe protists

Answer 6

Eukaryotic singular celled organisms. Are either heterotrophic or photosynthetic

Question 7

Describe fungi

Answer 7

Eukaryotic mostly multicellular organisms (except yeast). Heterotrophic and commonly non motile with chitin cell walls

Question 8

Describe plantae

Answer 8

Eukaryotic multi cellular, non motile organisms

-photosynthetic (eg. Tree)

Question 9

Describe anamalia

Answer 9

Eukaryotic, multicellular, motile, heterotrophic

Question 10

Which as the four eukaryotes are motile?

Answer 10

Anamalia and some fungi

Question 11

What is the key difference between archaea and eubacteria?

Answer 11

The presence of a peptidogloycan cell wall

Question 12

How old is the earth?

Answer 12

4.5 billion years

Question 13

Describe atmospheric conditions on the early earth

Answer 13

Extremely hostile, reducing atmosphere that allowed for the formation of carbon rich compounds and provided little protection against UV rays. This was incompatible to most life

Question 14

What was the first types life to evolve when??

Answer 14

Prokaryotes 3.8 billion years ago. They dominated life from 3. 8- 2 billion years ago

Question 15

When did Cyanobacteria first begin evolving?

Answer 15

3. 5 billion years ago

Question 16

What impact did Cyanobacteria evolution have on atmospheric composition?

Answer 16

They raised Oz concentration (as they are photosynthetic) about 2.4 billion years ago in the great oxygenation event

Question 17

What happened to the oxygen released by Cyanobacteria (what did it form)

Answer 17

Free oxygen immedi ally dissolved into surrounding waters, and when its concentration within these waters was sufficient, it precipitated out as iron oxide. This accumulated in sediment in alternating with chert, forming banded iron formations

Question 18

What happens when the oceans became supersaturated with oxygen

Answer 18

It began to gas out and changed atmospheric composition

Question 19

When did the great oxygenation event occur?

Answer 19

It began with the evolution of Cyanobacteria around 2.7 billion years ago, but peaked 2.4 billion years ago

Question 20

What was the first evidence of life on earth?

Answer 20

Stromatolites found in Australia. Stromatolites from when Cyanobacteria colonies group together, so provided the first evidence for life on earth

Question 21

What were the impacts of the great oxygenation event?

Answer 21

Raised atmospheric oxygen levels over billions of years, formed the ozone layer which protects the earth from harmful UV rays, made conditions more favourable to many forms of life

Question 22

What impact did the great oxygenation event have on the already present prokaryote populations (besides Cyanobacteria)

Answer 22

In pure form, oxygen attacks chemical bonds and can inhibit enzyme growth and damage cells. This was toxic to many prokaryotes, causing a large die off

Question 23

How did organisms react to the great oxygenation event?

Answer 23

They had to adapt their physiology quickly in order to survive, such as evolving to use respiration as their main source of energy

Question 24

When did Eukayotes first evolve?

Answer 24

Between 1.5 and 2.1 billion years ago, although there is evidence of them existing in 2.7 billion year old shale

Question 25

How do eukaryotes differ from prokaryotes?

Answer 25

They have an endoplasmic recticulum,membranes,nulcelus,chloroplast,mitochondria and a well developed nuclear envelope. In contrast, prokaryotes lack membrane bound organelles and store dna in plasmids

Question 26

Which three forms of life are thought to have diverged from a com ancestor?

Answer 26

Modern eukaryotes, archaea bacteria and eubacteria are all thought to have evolved from a common ancestor prokaryotes

Question 27

How are eukaryotes thought to have evolved?

Answer 27

Via endosymbiosis

Question 28

How does endosymbiosis occur(simply)

Answer 28

A prokaryote would’ve engulfed a smaller cell (called an endosymbiont) and instead of dissolving it, this smaller life form would become an organelle performing functions within the host. The two would become one organism over time

Question 29

What endosymbiont formed modern day eukaryote mitochondria?

Answer 29

Aerobic heterotrophic prokaryote

Question 30

What organism is thought to have formed chloroplast in modern day eukaryotes?

Answer 30

Cyanobacteria

Question 31

What is the evidence that mitochondria and chloroplast formed organelles via endosymbiosis?

Answer 31

They are similar to bacteria in size and replicate by splitting in half. They also have dna for some of their components that replicates when the cell divides and genes are transcribed in the organelle- NOT the nucleus.

Question 32

Why did endosymbiosis occur?

Answer 32

Due to the great oxygenation event, the world became aerobic around 2.4 billion years ago. An anaerobic prokaryote would’ve benefitted from a symbiotic relationship with an aerobic prokaryotes, as it would’ve had the ability to carry out OXIDATIVE METABOLISM. The acquisition of Cyanobacteria would’ve given the prokaryote nutritional independence

Question 33

What feature do aerobic prokaryotes have that an anaerobic prokaryote would’ve required in order to survive in an aerobic world?

Answer 33

An oxidative metabolism

Question 34

When does the first evidence of multicelluarly date to?

Answer 34

1.8 billion years ago

Question 35

When did large and diverse multicellular organisms evolve?

Answer 35

600 million years ago

Question 36

How did diverse multicellular organism evolve?

Answer 36

Single called eukaryotes living in close proximity lead to the development of specialised cells and sexual reproduction. Sexual reproduction cause GENETIC VARIATION, and increased rates of evolution.

Question 37

What are the edicaran biota?

Answer 37

The first group of complex, multicellular organism. They lived 630-541 million years ago

Question 38

How does sexual reproduction lead to genetic variation?

Answer 38

Gamete fusion allows for genetic recombination, variation occurs, selection acts on it and evolution follows

Question 39

What were the next eukaryotes to evolve (after multicellular ones)

Answer 39

Jellyfish and worms, around 600 ma

Question 40

What important event occurred 35g-325ma?

Answer 40

The Cambrian explosion

Question 41

When was there a large increase in eukaryote diversity?why?

Answer 41

570 ms, as it was the end of an ice age (conditions became more favourable )

Question 42

When did plants and fungi colonise land?

Answer 42

500 ma

Question 43

Give the dates of the five mass extinctions, and how much life was lost

Answer 43

Ordovician Silurian mass extinction: 440 ma. 50% of animal families
Devonian Carboniferous: 355 ma. 30% animal families
Permian Triassic. Approx 250 ma. 60% animal. 95% marine
Triassic Jurassic. 205ma. 35% all Life
Cretaceous tertiary. 65ma. 50% animal families

Question 44

What is adaptive radiation?

Answer 44

After mass extinction events, many ecological niches that were previously occupied become available. Surviving species diversify rapidly to fill these niches

Question 45

How long did it take for marine species to recover after the Permian Triassic mass extinction?

Answer 45

10. Million years

Question 46

When did mammals undergo adaptive radiation? Why?

Answer 46

After the Cretaceous tertiary mass extinction, as they no longer had to compete for resources with dinosaurs.