chapter 15: tracing evolutionary history macroevolution - the major changes in the history of life...

Chapter 15: Tracing Evolutionary History

Macroevolution - the major changes in the history of life on Earth

- development of new species, extinction, etc…

- origin of evolutionary novelties (feathers)

How do scientists trace (follow) macroevolution?

- fossil record

NEW AIM: How has life evolved over the past 3.5 billion years?

- Evolution on the grand scale, above the level of a single species


Geological Time Scale

- built using evidence from the sequence of fossils in rock – shows macroevolution

Time

Eras

Periods

Epochs

AIM: How has life evolved over the past 3.5 billion years?


Geological Time Scale

How do scientists decide when one era/period ends and a new one begins?

Mass Extinctions


and

Emergence of very different species

Chapter 15: Tracing Evolutionary HistoryGeological Time Scale

Cambrian Explosion

540 MY ago — rapid appearance of most major groups of complex animals



Mass Extinctions

251 MY ago — Earth's largest extinction (the P/Tr or Permian-Triassic extinction event) - killed 96% of all marine species and an estimated 70% of land species (including plants, insects, and vertebrate animals). Created the opportunity for dinosaurs to become the dominant land vertebrates…the Great Dying



Mass Extinctions

65 MY ago — (the K/T or Cretaceous –Tertiary extinction event) - about 50% of all species became extinct. Ended reign of dinosaurs and opened the way for mammals to become the dominant land vertebrates.



Mass Extinctions

The Holocene Extinction — possibly one of the fastest ever:

humanity's destruction of the biosphere could cause the extinction of one-half of all species in the next 100 years.


Chapter 15: Tracing Evolutionary HistoryHow do we determine the age of rocks and the fossils they contain?

Radiometric dating- based on measurement of radioactive isotopes

- Carbon-14 dating (14C)

* There is a somewhat fixed ratio of 14C to 12C in the atmosphere

* All living organisms should have the same ratio of 14C to 12C in our bodies

(we eat carbon from the atmosphere)* So we know the 14C to 12C ratio in living organisms

NEW AIM: How do we determine the age of rocks and the fossils they contain?




AIM: How do we determine the age of rocks and the fossils they contain?

What happens to 14C over time?




* 14C is always decaying to 14N


What happens to 14C over time?




* Ratio of 14C: 12C in a living organism is that same as the atmosphere

Assumptions:

* 14C is always decaying to 14N

So what happens when an organism dies?- no new 14C entering, but 14C is decreasing due to decay





- half life (t1/2) = 5,730 years

- So every 5730 years, half the amount of 14C remains

So if I die today, and a scientist find my bones 11,460 years from now, how much would you expect the 14C to have decreased?


By 75% (cut in half twice) or there should be about 1/4 the atmospheric 14C

How long does it take for 14C to decay?


Question:

Your measurements indicate that a fossilized skull you unearthed has a 14C-to-12C ratio about one-sixteenth that of the atmosphere. What is the approximate age of the skull?

22,920 years old





- Works well for fossils <50,000 years old

- For older fossils: Potassium-40 dating

- t1/2 = half life = 1.3 billion years

- Works well for rocks and fossils hundreds of millions of years old

LIMITATION: error factor of +/- 10% for radiometric dating


(at this point most of the 14C has broken down)


Review


1. Macroevolution

- major changes over time

2. Geological Time Scale (GTS)

- built with fossil evidence

3. Radiometric dating

- allows scientists to determine the age of rocks and fossils for a more accurate GTS (absolute dating)

4. Relative dating- Dating using the relative position of the fossil you found to the other fossils above and below it in sedimentary rock. Ex. If I find a feathered dinosaur fossil, and below it I find a non-feathered dinosaur fossil, and above it I find a bird fossil, I

can conclude that this feathered dinosaur is older than the bird, but younger than the non-feathered dino.


Phylogeny - the evolutionary history of a group of organisms

NEW AIM: How do scientists (systematists) organize life?


Phylogenetic tree (evolutionary tree) - diagram that traces evolutionary relationships as best we can

AIM: How do scientists (systematists) organize life?


Systematics- the study of biological diversity in an evolutionary context

- includes taxonomy (naming and classification of species)

- grouping species into broader taxonomic categories

Taxon - a taxonomic level (family, order, class, etc…)



Taxonomy follows phylogeny (evolutionary relationship)


Chapter 15: Tracing Evolutionary HistoryAIM: How do scientists (systematists) organize life?

A major branch in the phylogenetic tree will be a major taxon like a class, order, family, etc…

Taxonomy follows phylogeny (evolutionary relationship)


Each taxonomic level gets more and more constrained in its definition until you only have a single species.

Phylogenetic trees are Built using:

- structural and developmental features

- molecular data- behavioral traits


Many species of Carnivores

One species of domestic cat


How are divergent and convergent evolution different?



Divergent evolution:

Occurs when a group from a population develops into a new species…

The new species will microevolve independent of each other potentially leading to similar structures with different functions called…

Homologous structures


Divergent evolution:

Homologous structures

PROBLEM: Not all likeness is inherited from a common ancestor


Ocotillo (Baja California) Allauidia (Madagascar)

Structures that are similar, but not shared with a common ancestor (arose independently) are called analogous structures.


Closer analysis of the DNA reveals that these leaves and spines are made in very different and unrelated ways…

Example:


Ocotillo (Baja California) Allauidia (Madagascar)

How do analogous structures come to exist in nature?


Closer analysis of the DNA reveals that these leaves and spines are made in very different and unrelated ways…

Example:


Convergent evolution: Different species may live in similar environments that naturally select for similar traits. Therefore, these species converge on similar traits from completely independent evolutionary events (there is no common ancestor with the trait).

Common reptilian ancestor without wings

birds batslizards mice

Wings evolve Wings evolve


The insect wing, pterodactyl wing, bird wing and bat wing are analogous structures. Why?

Examples:


Because they do not share a winged common ancestor. The wings evolved independently in each case.

Examples:


What about the bone structure of the pterodactyl, bird and bat wing?

Examples:


Examples:


**The bone structure of the bat wing and bird wing is homologous because the common ancestor of these two (reptiles) had a similar bone structure. However, the rest of the wing evolved independently. There is no winged common ancestor.


The structures of dolphins and fish are an incredible example of analogous structures. The recent ancestors of dolphins were land mammals. The fins and shape of these two groups of organisms evolved independent of each other…

Examples:


Fig. 15.14A



Fig 15.14B


Why do we think eukarya branched off archae and not eubacteria?

NEW AIM: How did life begin on Earth?

How did life begin on Earth?

Chapter 16: 16.1-16.3, 16.6, 16.10, 16.18


The Nebular Hypothesis

Chapter 16: 16.1-16.3, 16.6, 16.10, 16.18

One of many hypothesis that attempts to describe the birth of our SOLAR SYSTEM.

Initially, the mass of the solar system was spread out in a slowly rotating cloud of dust and debri called a nebula.

The nebula would have formed as the result of a supernova – a violent explosion at the end of a large stars (8x bigger than our sun) life.



Chapter 16: 16.1-16.3, 16.6, 16.10, 16.18

The cloud would have collapsed due the force of gravity (attraction of all mass to all other mass)When a large, slowly rotating mass collapses inward, it becomes a small, fast rotating mass – (think of a spinning figure skater with their arms out. What happens when they pull them in? – the law of conservation of angular momentum)

The rapid spinning would cause the mass to flatten like a disk (what happens when you throw pizza dough in the air and spin it?)



Chapter 16: 16.1-16.3, 16.6, 16.10, 16.18

The majority of the mass would still be in the center held by gravity forming the sun.

The mass in the disc would begin to clump together (accretion) and form the planets.


Earth’s Beginning

1. The great bombardment

4.6 Billion years ago

From 4.6 to 4 billion years ago the remaining mass in the vicinity of Earth was drawn in by Earth’s gravitational field.

Earth was a molten ball of rock…


2. Cooling DownThe outer surface of the planet cooled off and solidified forming the crust (current land sea floor)

There is no atmosphere yet. It is too hot; any gases would escape Earth’s gravitational field…


A. First, the Earth needed to cool enough to hold an atmosphere…

B. The atmosphere was generated by gases blowing out through the Earth’s crust…we call these…

3. Formation of the atmosphereHow did the atmosphere form?

Volcanoes

C. What was the early atmosphere composed of and how did you come up with this?


D. We hypothesize that the gases emitted by volcanoes 4 billion years ago was similar to what they continue to emit today:

- Carbon monoxide (CO)

- Carbon Dioxide (CO2)

-Nitrogen (N2)

- Water H2O

- Methane (CH4)

- Ammonia (NH3)

We still do not have any liquid water…no oceans…why?

- Hydrogen (H2)

3. Formation of the atmosphere

(This is your early atmosphere)

Too hot, all water is in the gaseous form…the oceans are in the atmosphere


A. The Earth continues to cool down…

Torrential rain

B. The water in the atmosphere begins to condense:

Lightning

4. Formation of the Oceans

C. The oceans are formed…

AIM: How did life begin on Earth?

Life appeared somewhere between the end of the great bombardment (4Bya) and the oldest known fossil (3.5Bya).

Conclusion (How long did it take for life to develop?):

<500 million years for life to appear!!Fig. 16.1C

End of the great bombardment


So how did life begin?

What is required for there to be life as we know it?

ORGANIC MOLECULES (monomers)


1920s- Oparin and Haldane first proposed that the Early conditions on Earth were sufficient to generate organic molecules.

Haldane Oparin


How would you test this hypothesis?

Haldane Oparin


1953- Stanley Miller- 23 year old grad student in the laboratory of Harry Urey at the University of Chicago


Fig. 16.3B

After one week:

Found organic compounds

- amino acids (abundant)

Since then:

Most of 20 amino acidsSugarsNitrogenous basesATP!!Lipids

Miller-Urey Experiment = early Earth simulation


Fig. 16.3B

Conclusion:

Conditions on early Earth were sufficient to produce the organic molecules of life (monomers)

Does that mean you have life?

Absolutely NOT

Then how do we think life began?


Fig. 16.6B

Coacervates Liposome

- Both are microscopic spheres filled with fluid (not alive)1. Selectively permeable membranes2. Can grow by absorbing molecules3. Divide when they reach a certain size


Fig. 16.6B


The Oil Slick Hypothesis -There are many different ideas of which the oil slick hypothesis is ONLY one.

1. If phospholipids or phospholipid like molecules did form, they would have made countless liposomes in the early oceans…


Fig. 16.6B


2. What would have been present within each liposome?

A RANDOM assortment of organic molecules


Fig. 16.6B


3. What would need to happen for one of these liposomes to be considered life?

It would need to divide into two on its own and pass along the information to do this.. It doesn’t have to do it well because… it would have no competition.


Fig. 16.6B


4. You have countless numbers of random liposomes filled with organic molecules in the oceans for 500,000 years. Is it possible for just one to randomly be able to divide on its own?

NEW AIM: In what sequence did the nutritional classifications arise?

REVIEW 16.10

That first cell…what kind of cell do you think it was in terms of nutritional class? And what do you think the order of appearance of nutritional classes is on Earth?

AIM: In what sequence did the nutritional classifications arise?

Which type of organisms would you hypothesize to be the first on the planet?

a. Aerobic heterotrophb. Aerobic autotrophc. Anaerobic heterotrophd. Anaerobic autotrophe. None of the Above



The Heterotroph Hypothesis

Little CO2 in the atmosphere of early Earth.


Little if any O2 in the atmosphere of early Earth.

Plenty of organic material to eat






In order to use light, organized macromolecules are required, but how did they organize the molecules to begin with?

Why else would a photosynthetic organism not be logical?

What type of organism would you predict to be next?


Perfect for Anaerobic photoautotrophs (photosynthesis)

Anaerobic Heterotrophs added CO2 to the atmosphere (fermentation)

Organic food would eventually run low

(New environment, new selective pressures)


Organized macromolecular structures exist now

(remember: still no molecular oxygen in atmosphere)

Why not aerobic photoautotrophs?

Anaerobic chemoheterotrophs (fermentation)


A. Autotrophs (predominantly cyanobacteria aka blue-green algae (IT’S NOT ALGAE)) will release O2 into the atmosphere

O2 is poisonous to most anaerobic heterotrophs Natural selection for aerobic heterotrophs and autotrophs

?Q. How would photosynthetic autotrophs alter the environment?


Anaerobic photoautotrophs (photosynthesis)

Anaerobic heterotrophs (fermentation)



Aerobic heterotrophs and autotrophs (cellular respiration)

- This theory says NOTHING about how the first organism came to be.


- These are all prokaryotic at this point…

(like free-living chloroplasts)

(like free-living mitochondria)

Anaerobic heterotrophs (fermentation)



Aerobic heterotrophs and autotrophs (cellular respiration)


(anaerobic) (anaerobic) (aerobic) (endosymbiotic theory)


- Anaerobic heterotrophs (fermentation)

Review

- Anaerobic photoautotrophs (photosynthesis)- Aerobic heterotrophs and autotrophs (cellular respiration)

4. Heterotrophic hypothesis

2. Miller-Urey Experiment

- formation of organic molecules/ primordial soup3. The First Cell

- Coacervates and Liposomes

1. Early Earth- Nebular Hypothesis- Great Bombardment- Early Earth conditions

- endosymbiotic theory


Go back and re-memorize the phyla as well as this phylogenetic tree showing the order of emergence of each phyla.

chapter 15: tracing evolutionary history macroevolution - the major changes in the history of life...

Documents

history of life

mass extinctions aim

land species

new species

c ratio

grand scale

different species

single species