Biology 2 Chapter 25

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53 terms · The History of Life on Earth

What are the four main stages that led to the formation of living cells?

1. The abiotic synthesis of small organic molecules, such as amino acids and nucleotides. Proof- Meteriorites.
2. The joining of these small molecules into macromolecules, including proteins and nucleic acids. Ex. proof- Dipping amino acid solutions in hot sand, clay, or rock, producing amino acid polymers.
3. The packaging of these molecules into "probionts" droplets with membranes that maintained an internal chemistry different from that of their surroundings. May exhibit some properties of life, including simple reporudcing and metabolism and maintaining separate environment from outside. An example is a lipsosme that can form when lipids and other organic molecules are added to water
4. Origin of self-replicating molecules that eventually made inheritance possible.

Hypothesized that Earth's early atmosphere was a reducing (electron adding) environment, which which organic compounds could have formed from simple molecules

Chemist--Oparin and sciencist Haldane, 1920 independently

Examples of macroevolutionary change

1. Origin of key biochemical processes such as photosynthesis.
2. Emergence of the first terrestrial vertebrates
3. Long-term impact of mass extinction on the diversity of life.

No fossil evidence exists for the origin of life, T or F.

True. Nothing. Have to use experimentation to try to hypothesize what happened. Earth formed around 4.6 billion years ago, condensing from a vast cloud of dust and rocks that surrounded the young sun. Inhabitable phase ended around 3.9 billion years ago. Earth consisted of various compounds released by volcanic eruptions, including nitrogen and its oxides, carbon dioxide, methane, ammonia, hydrogen, and hydrogen sulfide.

Earth was truly reducing, T or F?

False. New studies show that there were likely pockets around submerged volcanoes and deep-sea vents. There was probably not enough methane and ammonia to be reduced in rest of areas. Early atmosphere was primarily made of nitrogen and carbon dioxide and was neither reducing nor oxidizing. Chemical composition of meteorites supports Miller and Urey's hypothesis.

Milley and Urey's experiment

Reproduced and synthesized similar amino acids found in organisms today, along with other organic compounds. Chemical composition of meteorites supports Miller and Urey's hypothesis.

Two key properties of life

1. Accurate replication
2. Metabolism

* Neither can exist without the other.

Example of protobiont

Liposomes, lipids or other organic molecules added to water.

First genetic material was likely RNA, T or F?

True. RNA can replicate faster and are more stable in certain environments with fewer errors in replication.

What happened to probionts

Gained self-replicationg, catalytic RNA that could grow, split, and pass its RNA molecules to its daughters. Natural Selection would occur. This could have formed DNA as it is more stable, less fragile and replicates more accurately than RNA.

Key Features of Fossil Record

1. An incomplete chronicle of evolutionary changes.
2. Many organisms did not die in the right place at the right time to be preserved by fossils. Those that were may have been destroyed. Only a small fraction survived.
3. Bias for species that existed for a long time, wer abundat, and widespread in certain kinds of environments, and had hard shells, skelotons, or other parts that facilitated their fossilation.

**Even though limitations it is remarkably detailed account of biological change over the vast scale of geologic time.

Radiometric dating

One of the most common techniques to determine "absolute" (given in years not relative terms such as before or after). Bases on the decay of radioactive isotopes.


The time it takes for 50% of the parent isotope to decay.

Radioactive isotope is not affected by temperature, pressure, or other such environmental factors, T or F?

True. That is what makes it so effective.

Ex. of how radiometric dating works

Carbon-12 stays same in organism. Carbon 14 converts to nitrogen. Measure the ratio of carbon-14 to carbon-12. Works for fossils up to 75,000.00

Cannot measure old fossils but can guess through certain methods, T or F?

True. You cannot because no long term half lifes like uranium-238 and moreover the sedimentary rocks tend to be composed of sediments of differing ages. Can measure layers volcanic rock and guess.

Also can use measurements of magnetism since formation of volcanic and sedimentary rocks align with earth's magnetic field.

Unique features of mammals fossils

1. Lower jaw is composed of one bone. (dentary) (several other in other organisms).
2. Lower and upper jaws hinge between a different set of bones in mammals.
3. Three unique bones that transmit sound in the middle ear (hammer, anvil, and stirrup). Ohters only have stirrup.
4. Teeth are differentiated into incisors for trearing, canines for peiercing and muultipointed premolars and molars (for grinding). In contrast other tetrapods a row of undifferentiated single pointed teeth.


Mammal ancestor with single-pointed teeth, multiple bones in the lower jaw and single-pointed teeth. Synapsid (300mya); therapsid (280mya) Early cynodont (260mya), latter cynodont (220 mya), very late cynodont)

What are the three eons of Earth's history and their corresponding years, along with unique features?

1. Archaean 4.6 billion to 2.5 billion. prokaryotes, oxygen increases in 2,700 billion
2. Proterozoic- 2.5 to around 550 million, eukaryotic cells appear, diverse algae and invertebrae are formed.

(Archaean and proterozoic represent first 4 billion years).

3. Phanerozoic- 550 million to present. Formation of plants, reptiles, mammals, birds, humans, primate groups.*****Most of the time that animals have existed on earth. All the phyla were available by this time.

*Boundaries determined by major extinction events seen in the fossil record, when many life forms disappeared and were replaced by evolved survivors.

Early evidence of life

3.5bya. Found in stromatolites (layeered rocks that form when certa in prokaryotes bing thin films of sediment together. Early evidence suggests 3.9 possibly.

*Early prokaryotes were only form of life from 3.5 bya to 2.1 billion years ago.

Most atmospheric oxygen gas is of biological origin, producing the water-slitting temp, Tu or F

True. O2 gradually increased from 2.7bya. Rising increased in CO2 likely killed many prokaryotic groups. Rise probably brought about by rise in atmospheric 02 levels) Gradual rise is likely due to atmospheric 02 levels.

Eukaryotic plants

2.1 bya.


Mitochondria and plastics were formerly small prokaryotes that began living within larger cells.

Serial endosymbiosis

Supposes that mitochrondria evolved before plastids through the siequence of endosymbiotric world. Probably gained entrance as an undigested prey or internal parasytic.

mit and plasids are similar to prokaryotic ribosomes than they are to cystoplastic ribosomes in eukaryotic cells.


What are the three eons of Earth's history and their corresponding years, along with unique features?

1. Archaean 4.6 billion to 2.5 billion. prokaryotes, oxygen increases in 2,700 billion
2. Proterozoic- 2.5 to around 550 million, eukaryotic cells appear, diverse algae and invertebrae are formed.

(Archaean and proterozoic represent first 4 billion years).

3. Phanerozoic- 550 million to present. Formation of plants, reptiles, mammals, birds, humans, primate groups

What are the three eras of the Phanerozoic eons and characteristics of each era?

3. Phanerozoic- 550 million to present. Formation of plants, reptiles, mammals, birds, humans, primate groups
What are the three eras of the Phanerozoic eons and characteristics of each era?
1. Paleozoic- Vascular plants appear, marine algea, repitile, bony fishes
2. Mesozoic- Age of reptiles, dinosaures, flowering plants, cone bearing plants, gymnospears
3. Cenozoic- mammals, birds, pollinating insects, angiosperm, primates, humans, ice ages
When and what was the first sign of life?
3.5 billion years ago- Stromatolites- layered rocks that form when certain prokaryotes bind thin films of sediment together. Early prokaryotes lasted from 3.5 billion to 2.1 billion.

Earliest multicellular eukaryotes

1.5 bya. Oldest fossil algae 1.2 billion years ago. Small algae. 750-580 mya
Snowball effect- Most life would ahve been confined to areas near deep=sea vents and hot prings or to equatoral region s of the ocean that lacked ice cover.

Most atmospheric oxygen is biological in origin, T or F?

T. First O2 would have precipitated to iron oxide.

What is the evidence for endosymbiosis?

1. homologous membranes to plasma membranes
2. Replicate similar to that of some prokaryotes.
3. Single, circular DNA like chromosomes of bacteria.
4. Size, nucleotide sequence, and sensitivity to certain antibiotics, more like prokaryotic ribosomes.

Oldest known fossils of multicellular eukaryotes is?

Small algae that lived about 1.2 billion years ago. Larger ones did not appear until around 565 million years ago.

What caused growth of multicellular eukaryotes?

Thawing from ice-age.

What was the Cambrian explosion?

Many phyla of living animals appear suddenly in fossibls formed early in the Cambrian period (535-525).

What three living animal phyla appeared?

. Cnidaria (sea anenomes)
2. Porifera (sponge)
3. Mollusca (molluscs)

Prior to this all large animals were soft-bodied and mostly herbivors. This change brought the carnivor.

Many animal phyla originated before Cambrian explosion, T or F?

T, DNA suggests this hypothesis.

When did colonization of land occur by larger forms of life (fungi, plants, animals)

00 million years ago. Before this photosynthetic prokaryotes coated damp terrestrial surfaces over 1 billion years ago.

Arthropods (insects and spiders) are most widespread and diverse land animals that are tetrapod.


A new supercontinenct will again form 250 mil years from now.

Yes. Wild.

Interior of Pangina

Cold and dry, probably an even more severe environment than that of Central Asia today.

Affects of continental drift

1. Alters haitats. Pan
2. Climate Change
3. Continental drift also promotes allopatric speciation on a grand scale.

Mass entinctions are sominated by the fossle record past over 500 milliion years.


Permian mass extibnction

Defines the borders between Paleozoic and Mesozoiceras claimed about 96% of themarine animals species. Mass extinction occurred in 5 million years. Volc eruption and oxygen change.

Cretaceous mass extinction

65.5 million years ago. Boundary between the Mesozoic and Cenozoic. This event distinguised more than hlaf of all marine species and eliminated many families of terrestrial plants and animals, including most dinosaurs. Ev. Thin layer having iridium


5-10 million yeras for diversity of life to recover to previousl evels.
Can provide more predators and eliminate species, along with ecosystems.

Adaptive radiations

Periods of evoluationary change in which groups of organisms form many new species whose adaptations allow them to fill different niches. Occurred after each mass entinction.

Mammals and exinction

1. 180 million years ago originated and then after death of dinosaurs around 65 mya expanded a gon.

Examples of increase in diversity from radiations

1. Rise of phytosynthetic prokaryotes
2. Evolution of large predators in Cambrian explosion,
3. Following colonization of land by insects, plants, and tetrpods.

Regional adaptative radiations

Ex. Hawaiin archipelago. most species found no where else in world.


Evolutionary change in the rate or timing of developmental events


body features that were juvenile structures in an ancestral species now contained in that adults. Ex. Salamander containing some larvae features.

Homeotic genes

Master regulatory genes. Paires of wings, pairs of legs. Hox gene. Develop into structure approriate for particular location.

Gene to produce complex animals existed 30 million years before cambrian eplosion

True. Adaptive evolution of new and existing genes may have played a key role in shaping the great diversity of life.

Fraces Jocobs view

Not right, n goal. Evoluation of eye took place through series of incremental modifications benefiteing the eyes owners at every stage. Evolution and environment always changing.

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