Zoo 110 lec final: Paleontology & Extinction

What are the different types of fossils described in lecture

1. Trace fossils

   1. footprints in sedimentary rock

2. Body Fossils

What are the different types of Body Fossils

1. Bones and Teeth

2. Shells and Exoskeletons

3. Full body

4. Fossilized Soft Tissues

5. Plants and Wood

What are some different ways organisms can be fossilized besides in sediment?

1. Amber (sap)

2. Tar pits

3. Coal

4. Permineralization*

How can soft tissues get fossilized?

1. Amber

2. Frozen

How much of all of life that’s existed on earth is now extinct?

99%

What do fossils tell us?

1. phenotypes that no longer exist in nature

2. when groups of organisms appeared and diversified

   1. In geological time

3. transitional features that help us understand evolution

   1. Traits that are in between certain groups

Why does the fossil record appear more complete in the northern hemisphere?

1. More paleontologists (historical bias), we can access them easier here

2. Currently there are a lot of cool fossils coming out of deserts

3. heightened historical interest and presence of Lagerstätten sites (we have several of these sites)

   1. Have exceptionally preserved fossils and lots of them

Why do some depositional environments preserve more complete fossils than others?

1. Some areas doesn't disturb the bones as much = preservation remains intact

2. EX:

   1. Taxa derived from caves more complete than those from fluviolacustrine (lakes/rivers) and marine deposits

How do paleontologists find old fossil localities?

1. Looking in the literature and going there! 

2. Some exceptions->

   1. on private property that people don’t want you on

   2. Could be where it is now new development/building

How do paleontologists find new fossil localities?

1. Studying geologic maps

2. Want to know the time period where your animal would have been fossilized

How do they know how old rocks are?

1. Stratigraphy

   1. Good for Conodonts

What are the first 2 common ways to prepare a fossil for study?

1. Cellulose acetate peel technique (mostly plants)

   1. Peel away tiny slices at a time

   2. Cell walls are replaced by minerals 

2. Thin sections via lapidary saw

What are the last 2 common ways to prepare a fossil for study?

1. CT scanning

   1. 3D reconstruction

   2. Dark = less dense than areas that are lighter

2. Traditional preparation

   1. Dental picks or air scribes

   2. Months of slowly picking away from the rock and not the preserved organism

what were the Big Five Mass Extinctions, and when did they happen?

1. Ordovician (443 mya-> million years ago)

2. Devonian (359 mya)

3. Permian (251 mya)

4. Triassic (200 mya)

5. Cretaceous (65 mya)

what were the effects of Ordovician Mass Extinctions?

1. 86% of species

   1. Largely marine inverts

2. Attribute this to glacial and interglacial episodes

   1. sea level rise and fall as climate changes, change in atmospheric and oceanic chemistry

what were the effects of Devonian Mass Extinctions?

1. 75% of species

   1. 95-96% of fish species 

2. global climate change, anoxic (low oxygen) deep water spreading to shallower water, ultimately we do not know the cause

   1. All freshwater species die too

What were the effects of Permian Mass Extinctions?

1. 96% of species

2. Siberian volcanism and global warming, spread of anoxic marine water, increased concentration of CO2 and Hydrogen sulfide, ocean acidification

What were the effects of Triassic Mass Extinctions?

1. 80% of species

   1. A lot are inverts and Crocs/alligators

   2. Lead to the rise of dinosaurs

2. Volcanic activity in Central Atlantic Magmatic Province (CAMP) raised atmospheric CO 2, increasing global temperatures and leading to calcification crisis in oceans

What were the effects of Cretaceous Mass Extinctions?

1. 76% of species

   1. Decline of dinosaurs

2. Bolide impact in Yucatan

   1. rapid cooling, probably combined with Deccan volcanism, ultimately a shift to global warming, eutrophication (over influx of nutrients-> algae blooms) and anoxia of the oceans

How do we recognize mass extinction events in the fossil record?

1. Change in diversity among the fossil taxa between an older and a younger rock layer, in a given area

   1. look in a rock layer for fossils and if they don’t appear in younger rock layers for years then they probably went extinct

2. Ex: K-Pg boundary

What are 2 ways extinction rates measured in living taxa?

1. Species Persistence and Extinction Probability

   1. Persistence models

2. Red List and Conservation Status

   1. provides a measure of extinction risk and tracks changes in species' conservation status over time

What are 2 other ways extinction rates measured in living taxa?

1. Time Between Extinctions

   1. Mean duration of a species according to Dave Grout was about 4 million years

2. Extinction Rates in Different Taxa

   1. Mammals and birds have higher extinction rates than invertebrates because they often have more specific ecological requirements and slower reproduction rates

   2. Marine species are most at risk due to ocean acidification, overfishing, and habitat destruction

Extinction patterns over time and their balance with origination of new lineages

1. Extinction rates tend to increase gradually as species become less adapted to changing environmental conditions

2. Extinction rates increase = origination often slows

3. after a mass extinction event, there is often a burst of origination

   1. Because we can see if a taxon is present or absent over geologic time we can get a per-capita extinction rate

Adaptive radiations and their relationship with mass extinctions

1. rapid diversification of species after mass extinctions

2. occurs when new ecological opportunities open up

what are some examples of Adaptive radiations we learned in lecture?

1. Osteichthyan and chondrichthyan diversification after the extinction of armored fishes

2. Pollinator interactions allowed flowering plants to diversify

3. Mammalian diversification after the extinction of non-avian dinosaurs

Why is the K-Pg boundary important?

1. corresponds to a mass extinction event, one of the most dramatic in Earth's history

2. led to the sudden extinction of approximately 75% of all species

   1. including the non-avian dinosaurs

Human-caused extinction

1. Some taxa locally or completely extirpated due to human activity

   1. Deforestation

   2. Hunting

   3. Introduced species

Are we in a Sixth Mass Extinction now?

1. Many scientists believe we’re in the midst of a sixth mass extinction

   1. based on high extinction rates and significant habitat loss among extant taxa

What are three primary causes for this potential Sixth Extinction?

1. Population

2. Consumption

3. Climate Change