Mass Extinction in Earth History HHMI Activity (c) PDF

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Walkthrough lab on Mass Extinction in Earth History....

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Name _________________________________________________ Date _________________________ Period ________

Mass Extinctions in Earth History INTRODUCTION At least five times in Earth’s past, the vast majority of plant and animal species have been annihilated in a geologic instant. What triggered these dramatic events, and what might they tell us about the fate of our world? What do we know about Earth’s past history, and what does science tell us about the coevolution of Earth’s systems and life?

Vocabulary Terms: Biodiversity: variety of life in the world or a particular habitat Mass extinction: widespread, rapid decrease in biodiversity on Earth Adaptive radiation: rapid growth and diversity of new organisms in an environment Niche: the role or fit of a species in its environment Genera: groups of related species

ENGAGE AND EXPLORE 1. Click on the following link to launch and explore the features of EarthViewer: http://media.hhmi.org/biointeractive/earthviewer_web/earthviewer.html  Click, hold, and drag to rotate the planet.  Click, hold, and drag down the horizontal silver slider on the timeline; watch what happens to the planet and the data indicators as you move backward and forward in time.  Position the silver timeline slider at 0 MYA (top of the timeline). Click on the left "play" button at the bottom of the timeline; watch what happens. When the silver bar stops at the bottom, click on the right "play" button and watch again.  Position the silver timeline slider at 0 MYA. Click on "Charts" at the bottom of the screen. Choose a chart. Now click on the left "play" button at the bottom of the timeline. Watch what happens on your chosen chart as the slider moves down the timeline.  Click "pause" before the slider reaches the bottom of the timeline. Note that your chosen chart will show a demarcation in the data for that point in time.  Close your chart in EarthViewer by clicking on the "X" in the upper right-hand corner. 2. Make sure the timeline displays 0–540 million years and then click on "View" at the bottom of the screen; turn on "Mass Extinctions." Click "View" again to minimize the menu. 3. Note the five yellow triangles that appear on the right side of the timeline. These correspond to mass extinctions.

*Adapted from hhmi BioInteractive Mass Extinctions in Earth History GATHER DATA

4. Drag the slider to the Ordovician extinction, 440 MYA (million years ago). Use the EarthViewer features (click through the Charts) to fill in the following table. For Biodiversity, you will need to move the slider carefully and record the number of marine genera present just before and just after the extinction event. Gather data in the same manner for the remaining mass extinctions. MYA (Million Years Ago)

What was Earth’s surface like? Landmasses? Proportion of land to water?

Avg. Surface Temp (◦C)

O2 (%)

CO2 (ppm)

Day Length

Luminosity

Biodiversity (# of genera just before and just after extinction)

440

Majority water, land masses spread apart on two sides

15

18

4759

21.8

96.16

1360 870

Devonian

360

Land masses combine into one larger section far more water than land

17

27.6

3474

22.2

97

1025 793

Permian

250

Over 60% water, one very large land mass

17

26.3

577

22.7

98

1200 293

200

Land forming into the continents we see today, still 6070% water.

15

20.6

1367

13

98.2

766 520

16

22.7

889

23.7

99.5

2200 1400

14.5

21

392

24

100

2470

Mass Extinction

Ordovician

Triassic

Cretaceous

65

Present

0

Land beginning to spread out evenly, still a lot of water left on the opposite side The continents today, land masses spread out evenly, distinct shapes.

a. What patterns and correlations emerge from your table? Does any of the data suggest an explanation for the occurrence of mass extinctions? The occurrence of mass extinctions is spread out somewhat evenly, around 90-year differences (varies). Otherwise there is not much that shows an explanation. This makes sense as many mass extinctions are caused by external events, such as collisions with the earth. b. Calculate the biodiversity loss in each extinction and report in terms of percent. Ordovician

Devonian

Permian

Triassic

Cretaceous

% of Biodiversity Lost

-3s6%

-22.6%

-76%

-47%

-37%

MAKE PREDICTIONS

READ THIS: Mass extinctions leave behind niches in ecosystems that can be filled by new or existing species that exhibit adaptations allowing them to survive in those spaces. This process is called adaptive radiation. For example, the fossil record shows that mammals living more than 65.5 million years ago were mostly small, rodent-like, burrowing creatures without much diversity. After the Cretaceous mass extinction, however, there was a dramatic increase in the number and types of mammals.

5. Propose an explanation for why small rodents were able to survive the Cretaceous mass extinction. Small rodents were able to feed on the larger dead animals and they do not require as much food. This was important because the asteroid made debris fly into the air and block sunlight for large periods of time, which made food scarce. Additionally, small rodents could easily find shelter if necessary.

6. Return to EarthViewer. Move the slider down to "Cretaceous extinction" and click on the link. Read the information about this extinction. a. What caused the Cretaceous extinction? What effects did it have on the Earth? A 10-km-long asteroid cause the Cretaceous extinction. Because of the impact many animals died, and the aftereffects were lack of sunlight and changes in global climate. This temporarily reduced the biodiversity of the earth.

b. How did the extinction of the dinosaurs allow the adaptive radiation of mammals to occur? The extinction of the dinosaurs opened new niches, which allowed species that were able to stay alive during the extinction to thrive and flourish after. This is possible because the resources the dinosaurs once used was now available to different species.

c. Click “Charts” and display the Biodiversity chart during the Cretaceous mass extinction. What evidence do you see from this chart that large scale adaptive radiation occurred following the five mass extinctions? Observing the chart, it is visible that there is a decline in biodiversity and a sudden bounce. This rebound, which eventually crosses peak biodiversity (before the extinction), is the evidence for adaptive radiation. The chart displays that new species filled in gaps in the ecosystem. This pattern is visible in all mass extinctions.

d. Predict what would have happened if all the early mammals living 66 million years ago had died out in the Cretaceous mass extinction. If all the mammals died, they would be replaced by other animals such as insects, birds, and fish. We would simply have more of those than mammals, but there would still be life and biodiversity on earth.

7. Return to EarthViewer. Move the slider down to "Permian extinction" and click on the link. Read the information about this extinction. a. The information tells you that "it is thought that massive eruptions of Siberian volcanoes caused catastrophic global warming, ocean acidification, and widespread lack of oxygen in the oceans." Predict what kinds of evidence might have led scientists to this conclusion. What kind of evidence would suggest the existence of volcanoes? What kinds of evidence might suggest global warming, ocean acidification, or lack of oxygen in the oceans? Discuss your predictions with your table partner and record your ideas in the space below. By looking at fossils in different layers in the ground and analyzing patterns it is possible to see what caused their death. The composition of the rocks around it can also hint at what occurred. This might have led to the conclusion that there was ocean acidification and volcanoes. Also, a lot of these topics are tied to each other, so the occurrence of one suggests the occurrence of another.

b. What percent of species were estimated to have gone extinct during the Permian extinction? Ninety-six percent of species were estimated to have gone extinct during the Permian extinction. c. Following the Permian extinction, adaptive radiation of early reptiles occurred, which led to the Age of the Dinosaurs. Why do you think reptiles were able to survive for the most part? Predict what adaptations or advantages they may have had, considering the environmental conditions during this time. Reptiles live on land, which saved them from ocean acidification. Reptiles are also cold blooded, the global climate change would have gave them a very large advantage, as they were adapted to survive in heat and the cold-bloodedness allowed them to spend energy on growing larger and other things.

8. Many biologists propose that we are currently in a sixth major extinction. If this is true, this mass extinction event may be the first caused by one of the Earth’s inhabitants—humans. a. What human actions do you think may be the cause of the increased rate of extinction today? The destruction of habitats, hunting of animals, and the effects on the global climate may be the cause of the increased rate of extinction today.

b. What data could you collect that would support the idea that we are currently at the start of the sixth mass extinction? I would need to collect the biodiversity chart, if there is a sharp decline it is possible to conclude that we are at the start of a sixth mass extinction.

c. Considering your answers to the previous questions, what would you predict to be the long-term result of a sixth mass extinction? Eventually, the niche would be refilled by other animals and the biodiversity of earth would increase to even higher numbers....