BiologybLecture 12 Paleobiol & Macroevolution

Why is Earth considered a “Goldilocks” planet?

Surface temperature and gravitation force is “just right” to facilitate life

What is the timing for of key events in the evolution of life?

Humans arrived 300,000 years ago

What is the evidence that life initially evolved ~ 3.5 billion years ago?

A high C-12:C-13 ratio in sedimentary rocks and stromatolite-like fossils

How does presence of "rusty" rocks in the geological record offered definitive evidence for the appearance of life?

These rocks contain oxidized iron, O₂ would only be found if photosynthesizing organisms were present. 

Describe the timeline of the Great Oxygen Event

Oxygen was not present until 2.5 billion years ago. Ir was produced, but mostly absorbed in oceans. At 1.5 billion years, it is mostly absorbed by land surfaces and the growing ozone layer. From there, it satured the organic and inorganic matter and started to accumulate in the atmosphere.

Explain the Panspermia hypothesis

Life forms became trapped in debris ejected into space, and survived the journey to Earth

Describe the composition of the “primordial soup” and explain what conditions permitted organic molecules to build up to high concentrations.

Organic molecules formed and accumulated to high levels in the oceans. This is because there was no atmospheric O₂ or microbes to destroy them.

Indicate how the Miller–Urey experiments provided evidence for the evolution of life on Earth

They were able to reliably generate the building blocks of complex biological molecules. This provided support for the hypothesis that life originated from nonliving matter on Earth.

Explain why an appreciation of deep time is important to understand the evolution of life

it provides the massive amount of time needed for changes like natural selection, genetic drift, and speciation to occur

Discuss how fossils form and why they provide an incomplete record of the history of life

Fossils are remnants, impressions, or traces of organisms from the past that have been preserved in the Earth’s crust.

Becoming fossilized is a rare occurrence as most organisms compose very quickly or their bodies were too soft

List the other sources of tissues and DNA from extinct organisms.

Resin, Skeletal remains, mummified tissues, permafrost cores, marine sediments

Discuss the role of cyanobacteria in the GOE

Given that photosynthesis is the only natural source of oxygen on Earth, and that the only photosynthesizers at the time were cyanobacteria, it follows that a rise in atmospheric O2 must stem from the emergence of cyanobacteria.

Indicate the four lines of evidence supporting the theory of continental drift.

1. Puzzle-piece evidence 

2. Geological evidence

3. Fossil evidence

4. Underlying mechanism

Discuss the impacts of continental drift on the evolution of life

Populations were separated and continents moved into new latitudes

Describe the impact of mass extinctions in on the history of life on Earth.

wiping out major groups of organisms, which in turn opens up new ecological niches

Describe Ötzi the Iceman

He was preserved in a glacier in the Alps about 5000 years ago after being shot by an arrow. He carried a set of “tools” that were presumably critical to his survival.

Use results from radiometric dating to determine the age of a fossil.

Over time, radioscopes degrade into more stable breakdown products. Using the ratios of both, we can determine the age of a fossil.

Late Ordovician (Time, Cause, Organisms)

440 mya, 60% of all marine invertebrates,  formation of massive glaciers caused sea level

fall

Late Devonian (Time, Cause, Organisms)

360 mya, 50% of all animals, reduced oxygen levels in the ocean, triggered by

global cooling and oceanic volcanism

Late Permian (Time, Cause, Organisms)

250 mya, 96% of marine species and 70% of terrestrial species, Multiple meteor impacts and massive emissions of carbon dioxide from volcanoes that erupted across a vast swath of Siberia.This led to global warming, aridity and ocean anoxia

Late Triassic (Time, Cause, Organisms)

200 mya, 50% of all animal families, climate change, volcanic eruptions and asteroid

impacts

Late Cretaceous (Time, Cause, Organisms)

66 mya, 75% of plant and animal species and all non avian disnosaurs, a  huge meteor struck the earth. triggered worldwide volcanic activity and ejected enormous amounts of ash into the atmosphere, blocking solar input