section 1.3 outline - find peoplesnyderj/biology 101 - ecology, evolution, and diversity...1 text...

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Text Readings

Chapter Reading last Week:

Chapter #1 in Audesirk, Audesirk and Byers:“An Introduction to Life on Earth”

Pg. #1-17.

Text Readings

Chapter Readings this Week:Chapters #16 - 17 in Audesirk, Audesirk and Byers:

“The Origin of Species” (Pg. 316 – 326) and“The History of Life” (Pg. #332-345)

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Quiz #1

Next TuesdayChapters #1, #16, and #17

http://www.vcld.org/pages/newsletters/01_02_fall/testtaking.htm

Defining “Life”• Dictionary definition of life is:

– “the quality that distinguishes a vital and functioning being from a dead body”

• Living things are more than the sum of their parts; life is difficult to define

• The complexity and ordered interactions of parts in living things gives rise to certain emergent properties

• 1.3 What Are the Characteristics of Living Things?– Living Things Acquire and Use

Materials and Energy– Living Things Grow– Living Things Reproduce Themselves– Living Things as a Whole Have the Capacity

to Evolve– Living Things are Made of Cells– Respond to Stimuli– must maintain relatively constant internal conditions (homeostasis)

Characteristics of Life

??

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Order

and

Complexity

Levels of Organization

? ?

???

? ???

?

What is a Species?

Earth’s Biodiversity

Insects – 750, 000 SpeciesInvertebrates, fungi, algae – 359,000 Species

Plants – 250,000 SpeciesVertebrates – 41,000 Species

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Primitive Earth

Geological Sources - 4.5 Billion Years

HydrogenGas (H2)

likely escaped early atmosphere

Carbon Monoxide (CO)Carbon Dioxide (CO2)

Nitrogen(N2)

Water Vapor(H2O)

Methane(CH4)

Ammonia(NH4)

Atmospheric Gases:

Geologic Time. . . . . . “Human Existencehas been a mereblink of an eye interms of the life of the planet”

- Carl Sagan

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Life on Earth?

• Earth formed about 4.5 billion years ago• Earliest Life 3.9 to 3.5 billion years ago during

the Precambrian Era– Oldest fossil organisms found to date are estimated

to be about 3.5 billion years old

Primitive Earth

• Stanley Miller and Harold Urey (1953)– Noted that the

atmosphere of early Earth probably contained methane, ammonia, hydrogen, and water vapor, but no oxygen

Organic Molecules

• Miller and Urey (1953)– Simulated early

Earth’s atmosphere by mixing the above gases in a flask and adding an electrical discharge to simulate lightning

• Simple organic molecules appeared after a few days

Organic Molecules

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• Similar experiments by Miller and others have produced amino acids, short proteins, nucleotides, and ATP

Organic Molecules

• The lack of both life and oxygen gas on early Earth allowed large quantities of these organic molecules to accumulate in areas protected from UV radiation (beneath rock ledges, in oceans)

Organic Molecules

• Vesicles are small, hollow spheres formed from proteins or proteins complexed with other compounds– Have been formed artificially by agitating water-

containing proteins and lipids– Have a well-defined outer boundary that separates

internal and external environments– Depending on composition, membrane may be

remarkably similar to that of a real cellhttp://cse.stanford.edu/class/sophomore-college/projects-01/cellular-automata/beginning/beginning2.html

Membrane-Like Vesicles

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• Vesicles resemble living cells– Under certain

conditions, may absorb material from the external solution, grow, and divide.

http://cse.stanford.edu/class/sophomore-college/projects-01/cellular-automata/beginning/beginning2.html


• Certain vesicles (protocells) may have been the precursors of living cells.

http://cse.stanford.edu/class/sophomore-college/projects-01/cellular-automata/beginning/beginning2.html


But Did All This Happen?

• The experiments of Miller, Urey and others showed/demonstrated that organic (carbon-bearing) molecules, along with simple membrane-like structures, would have formed on Earth.

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• Given enough time and a sufficiently large pool of reactant molecules, even extremely rare, seemingly unlikely events can occur many times.

But Did All This Happen?

Time Randomness

– The First Cells in Earth’s Oceans Were Prokaryotes, Cells that Lack a Membrane-bound Nucleus.

– Some Organisms Evolvedthe Ability to Capture theSun’s Energy.

– Photosynthesis Increased the Amount of Free Oxygen in the Atmosphere.

The First Organisms

– Aerobic Metabolism Arose in Response.

– Some Organisms Acquired Membrane-Enclosed Organelles in a process known as endosymbiosis.

The First Organisms

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Prokaryotic Cells

• Two cell types seen among all living things– Prokaryotic (“before nucleus” in Greek)

• Only 1-2 micrometers in diameter• Lacking organelles or a nucleus

Prokaryotic and Eukaryotic Cells

– Eukaryotic (“true nucleus” in Greek)• Larger than prokaryotic cells• Contain a variety of organelles, including a nucleus

Prokaryotic and Eukaryotic Cells

• Cell types named after presence or absence of a nucleus– The nucleus is a membrane-enclosed sac containing

the cell’s genetic material

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Capturing the Sun’s Energy

• Photosynthesis requires sunlight, CO2, and hydrogen.– Earliest source of hydrogen believed to be

hydrogen sulfide.– Eventually, water replaced hydrogen sulfide as the

source of hydrogen and photosynthesis became water-based.

Stromatolites – Ancient Bacteria(“Stroma” – bed, “lithos” – rock)

- Unicellular

- 3.5 Billion years old

- Formerly known as“Blue-green Algae”

- Photosynthesis bythe bacteria depletedO2 in the surroundingwater, leaving CalciumCarbonate (CaCo3

-)as a precipitate (layer)

(O2 given off as a waste product in the atmosphere)

The Great “Oxidation”Event

• Water-based photosynthesis resulted in the release of oxygen gas as a by-product.

• Initially, oxygen combined with iron in the Earth’s crust to form iron oxide.

• Chemical analysis of rocks suggests that significant levels of atmospheric oxygen first appeared about 2.2 billion years ago.

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• The accumulation of oxygen in Earth’s atmosphere probably:– Exterminated many

anaerobic organisms.– Provided the

environmental pressure for the evolution of aerobic metabolism.

Aerobic Metabolism

• The evolution of aerobic metabolism

was significant because aerobic

organisms can harvest more energy per food

molecule than anaerobic organisms.

Aerobic Metabolism

Membrane-Enclosed Organelles

• The first eukaryotes (cells that possess membrane-bound organelles) appeared about 1.7 billion years ago

• Several organelles (mitochondria, chloroplasts, centrioles) may have arisen when primitive cells engulfed certain types of bacteria (the endosymbiont hypothesis)

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Geologic Time

Geologic Time. . . . . . . .

Precambrian Era(“Oldest Life”)

4.6 bya – 570 mya

Paleozoic Era(“Ancient Life”)

570 mya – 245 mya

Mesozoic Era(“Middle Life”)

245 mya – 65 mya

Cenozoic Era(“Recent Life”)

65 mya - present

Holocene Epoch20,000 ya – Present

Pleistocene Epoch1.8 mya – 20,000 ya


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Geologic Time. . . . . . . .Holocene and Anthropocene Epochs

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Carboniferous – Paleozoic Era

Triassic – Mesozoic Era

Cretaceous – Mesozoic Era

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Time scale: The Precambrian Era“Oldest Life”

• 4.6 by to 575 mya• Unicellular life (3.5 bya)• Oxygen accumulation in the atmosphere

(2.5 bya)• Oldest animal fossils (700 mya)• Diverse invertebrate fauna, first vertebrates

(610 mya)

• Cambrian Periodthe origin of most modern animal phyla 543 to 490 million years ago (called the “Cambrian Explosion”)

• 570-510 mya

Time Scale: The Paleozoic Era“Ancient Life”

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• Silurian Period– Diverse jawless

fishes– First jawed fishes– Vascular plants

and arthropods colonize land

– 440-410 my


• Devonian Period– Diverse bony fishes– First amphibians and

insects– 409-363 mya


• Carboniferous Period– Extensive forests of vascular

plants– First reptiles– Amphibians dominant– 363-290 mya


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• Permian Period (290 – 245 mya)– Extinction of many marine and

terrestrial organisms– Diversification of reptiles– Origin of reptile-like mammals– Origin of most modern insect orders


• Permian Period (290 – 245 mya)– Single continent Pangaea


• Triassic Period (245 – 208 mya)– Gymnosperms dominate landscape– 1st dinosaurs, mammals, and birds– Pangaea began to break into Gondwana and Laurasia

Time Scale: The Mesozoic Era“Middle Life”

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• Jurassic Period– Gymnosperms continue

to dominate landscape– 1st dinosaurs dominate– W. Laurasia (N.

America separate from southern continents)

– 208-145 mya


• Cretaceous Period (145 – 65 mya)– Angiosperms appear– Many extinctions including dinosaurs– Continents all separate except for Bering Strait


• The Tertiary Period, Paleocene Epoch– Major radiation of mammals and birds– Major radiation of pollinating insects– 65-57 mya

Time Scale: The Cenozoic Era“Recent Life”

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• Eocene Epoch (57 – 35 mya)– Angiosperms dominance increases– Origins of most modern mammal

orders


• Oligocene Epoch (35 – 23 mya)– Origins of many primate groups

including apes


• Pliocene Epoch (4 – 1.8 mya)– Ape-like ancestors of humans appear – N.A. and S.A. connect– Fauna similar over Northern Continents


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• Pleistocene Epoch– Ice ages (WIKN) – Humans appear – 1.8 my to 10,000 yr

http://www.museum.state.il.us/exhibits/ice_ages/images/loopglac.gif


Scientists Need a Clear Definition of Species– Species Are Groups of Interbreeding Populations.– Appearance Can Be Misleading.

What is a Species?

Clear Definition of Species Needed

• In Pre-Darwinian times, the term “species”referred to different kinds of organisms

• Species were classified initially based upon appearance.

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Species

• Today a species is defined as a group of actually or potentially interbreeding natural populations, which are reproductively isolated from other such groups (biological species concept)

Reproductive Isolation

• Reproductive isolation occurs when members of one population are unable to interbreed with members of another

• For most species, two or more isolating mechanisms interact to prevent the formation of fertile offspring

• How Is Reproductive Isolation Between Species Maintained?– Premating Isolating Mechanisms Prevent Mating

Between Species– Postmating Isolating Mechanisms Limit Hybrid

Offspring

Reproductive Isolation

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Isolating Mechanisms

• Isolating mechanisms prevent interbreeding and maintain reproductive isolation– Premating isolating mechanisms prevent mating

between species– Postmating isolating mechanisms prevent the

formation of viable, fertile offspring after mating has occurred

Premating Isolating Mechanisms

• Premating isolating mechanisms include:– Geographical isolation– Ecological isolation– Temporal isolation– Behavioral isolation– Mechanical incompatibility


• Geographical isolation occurs when populations cannot mate because of physical barriers– In nature, lions do not mate with tigers

• Lions live in Africa• Tigers live in India

• Ecological isolation occurs when species can’t mate because they occupy different habitats

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• Temporal isolation occurs when species can’t mate because they breed at different times

• Behavioral isolation occurs when species can’t mate because they have different courtship and mating rituals

• Mechanical incompatibility occurs when species cannot mate because their reproductive structures are incompatible

In Conclusion….

Major Points:

• Miller – Urey Experiments• Anaerobic Environment• Prokaryotes/Eukaryotes• Oxidation Event• Geologic Time Eras, Periods, and Epochs

In Conclusion….

Major Points:

• Earth - 4.5 billion years ago (bya)• Earliest Life 3.9 to 3.5 (bya)• Oldest fossil organisms 3.5 billion years old• Geologic time subdivided according to major

geologic and biologic events

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In Conclusion….

Major Points:

• Species – reproductive isolation• Pre- and post-mating isolating mechanisms.

Next Time……

Categorizing Life (Taxonomy) through Geologic Time

section 1.3 outline - find peoplesnyderj/biology 101 - ecology, evolution, and diversity...1 text...

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