Lecture 22: History of on (and Mass )

Reading – P. 426-431, 433-444 Quiz 8 review Midterm 2 review Extra Credit Opportunities!

• 0.5% added to your overall class score if you complete the final evaluation. This is part of a trial for a new student evaluation form for UCI. Complete by 5p.m. on Fri Dec 7th.

• 0.5% added to your overall class score if you complete a survey about new ALP classrooms. I’ll send an e-mail about this later this week, including a link to the Information Sheet about the education study. Learning Outcomes

• Be aware of the theories of where life might have begun

• Be able to explain how the affected and in turn was affected by atmospheric oxygen levels

• Be aware of some of the major events in of life and a rough idea of when these events occurred in relation to each other and the age of the Earth (I won’t ask about specific dates)

• Be able to describe/explain some causes of mass extinctions

• Be able to explain the causes of current loss of and characteristics of endangered

• Be able to give examples of how the Earth system influences the biosphere and how the biosphere influences the Earth Hadean Eon (4.54 – 3.85 Gyrs) Archean Eon (3.85 – 2.5 Gyrs) Origin of life on Earth: What we know

• Life maybe developed on Earth ~3.9 billion ago • Earliest organism probably even simpler than bacteria • Unknown where/how life formed

1. ‘Primordial soup’ 2. Deep-sea hydrothermal vents

3. Organic molecules http://www.youtube.com/watch?v=D69hGvCsWgA from space (unlikely) on Earth: Archean

3.5 – 1.5 billion years ago • Simple life forms (prokaryotes = no nucleus) were only life forms on Earth for ~ 2 billion years

• O2 levels very low so organisms limited to fermentation rather than respiration to release energy - less efficient so cells were small and simple History of life on Earth: Proterozoic

1.5 – 0.6 billion years ago

• Once O2 started building up then energy restrictions could be overcome and more complex, larger could develop

~ 600 million years ago (shortly after events) • Earliest evidence of multicellular resembling jellyfish, soft corals and flatworms History of life on Earth:

~570 million years ago • explosion • Major increase in diversity • First internal and external skeletons • Why did this ‘explosion’ occur? – Sexual reproduction?

– Continued build-up of O2 allowed formation of carbonate skeletons? History of life on Earth: Phanerozoic

~500 million years ago • Life started to develop on land • For life to exist on land need: – Structural support – Ability to transfer water within the organism and keep from dehydrating – Ability to exchange gases with air instead of water – Moist environment for reproductive system Life on land:

• Evolved from green algae • Earliest plants were seedless, reproduced using spores e.g. mosses, ferns • Conifers evolved – had seeds which allowed plants to spread to more diverse habitats • Flowering plants evolved – developed flowers to attract pollinators, increasing their reproductive success Life on land: Animals • First animals to move from ocean to land probably were e.g. millipedes. Still most numerous and diverse group.

• First animals with backbones were fish. Later moved onto the land where their fins could act as limbs.

• Evolved into – limited to moist environments

• Amphibians → → and

Mudskipper – amphibious fish iClicker Question: Putting it all together Can you put the images below in order from oldest to most recent? C

A

A) B-A-C B) C-B-A C) A-C-B D) C-A-B

BB Life on Earth: Mass Extinctions • Change in the number of species = origination rate - rate • If enough species become extinct over a period of time we call this a mass extinction

The ‘Big 5’ mass extinctions Mass Extinctions: Possible Causes

What do you think could cause a mass ?

(Can you think of at least 3?) Mass Extinctions: Possible Causes 1. 2. Extensive volcanism

3. Rapid and significant Mass Extinctions: Impact events

• Tunguska, Siberia • 1908 • Approx 60m meteor/comet fragment exploded 5-10km above surface • Equivalent to 5-30 Megatons (1000 x Hiroshima bomb) • Flattened 770 square miles of forest (80 million) trees) http://www.youtube.com/watch?v=dpmXyJrs7iU Mass Extinctions: Volcanism

Red = areas of igneous rocks Yellow dots = corresponding hotspots -Tertiary Mass Extinction When: 65 million years ago What: 80-90% of total species (land and ocean) anything over 25kg didn’t survive omnivores, insectivores, carrion-eaters survived Duration: extremely rapid (tens thousands of years or less) What might have caused the mass extinction at 65 Myrs that killed the ? a) Impact event b) Extensive volcanism c) Rapid climate change d) Some combination of the above Dekkan Traps, India 500,000 km2 of basalt up to 2km thick - Mass Extinction

When: 252 million years ago What: 70% land species 96% marine species 95% of all life on Earth at that time Duration: Uncertain still but potentially several short events (10- 100kyrs) over time, took 10 million years for life to recover after , Russia 4-7 million km2 of basalt up to 4km thick in places

Lava erupted through coal beds releasing extra CO2 Global temperature rose by over 6 oC Oceans stopped circulating (no oxygen) A 6th Mass Extinction Today? • activities are resulting in loss of biodiversity mostly due to: – Hunting/over-harvesting – and (habitat loss) – Pollution – Introduced/ – Continued climate change in future decades • Background extinction rate before humans = ~ 15 per • Today, in tropical forest, extinction rate = ~ 27,000 per year iClicker Question

Which species do you think is least likely to go extinct?

A C

B D A 6th Mass Extinction Today? • Humans activities are resulting in loss of biodiversity mostly due to: – Hunting/over-harvesting – Deforestation and desertification (habitat loss) – Pollution – Introduced/invasive species – Continued climate change in future decades • Species most vulnerable to extinction are – long-lived, large, low reproduction rates (so slow recovery), require large territories and high food supplies, highly specialized Future of life?

What will life look like millions of years from now? Must consider:

• Environment – controlled by , atmosphere composition, climate i.e. likely niches and habitats • What things will be left after the current extinction event to continue to evolve? What ecological niches will be empty? • How quickly the process of evolution will change a species?

https://www.youtube.com/watch?v=w0kzMmcTS8I& list=PL019H6clyzKb-fTn4WM5ypMym0rbNKHcr On Wednesday – Biogeochemical Cycles

Reading = P. 456-461, 464-468, 473