Evolution

• The process of biological change by which descendants come to differ their ancestors.

• Evolution

• A Swedish botanist in the 1700’s who developed a classification system for the organisms known at this time

• Carolus Linnaeus

• A group of organisms so similar to one another that they can reproduce and have fertile offspring

• species

• A French naturalist of the 1700’s who suggested that species shared ancestors. He also rejected that the Earth was only 6,000 years old

• Georges Louis Leclerc de Buffon

• Born in 1731, this was a respected English doctor and poet. He proposed that all living things descended from a common ancestor and that more complex forms arose from less complex forms.

• Erasmus Darwin

• In 1809, a French naturalist who proposed that all organisms evolved toward perfection and complexity. He did not believe in extinction, but he did believe that organisms evolved.

• Jean- Baptiste Lamarck

• He proposed that changes in an environment caused an organisms behavior to change, leading to greater use or disuse of a structure or organ. The organism would pass on these changes to offspring.

• Lamarck

• The French zoologist who did not believe in evolution but did believe in extinction. He observed that each stratum, or rock layer, held specific fossils.

• Georges Cuvier

• Traces of organisms that existed in the past.• fossils

• A theory that states that natural disasters such as floods and volcanic eruptions have happened often during Earth’s long history

• catastrophism

• A Scottish geologist who proposed that the changes he observed in landforms resulted from slow changes over a long period of time

• James Hutton

• A belief that landforms change slowly over time• gradualism

• The English geologist who wrote the book Principles of Geology in the 1830’s. Charles Darwin read this book and was inspired by it.

• Charles Lyell

• An expansion of gradualism that states that the geologic processes that shape Earth are constant through time. Essentially, the processes that occur today, also happened in the past.

• Uniformitarianism

• What concepts about the Earth did Hutton and Lyell agree upon?

• That changes occur gradually.

• What are the key differences between the theories of gradualism and catastrophism?

• Gradualism emphasizes slow changes on Earth over long periods of time, while catastrophism emphasizes change through natural disasters.

• In 1831, what ship did Darwin take that enabled him to travel around the world for 5 years collecting specimens and making observations of land?

• The HMS Beagle

• The differences in the physical traits of an individual from those of other individuals in the group to which it belongs.

• variation

• Variation that occurs among members of different species.

• Interspecific variation

• Variation that occurs among individuals of the same species

• Intraspecific variation

• A feature that allows an organism to better survive in its environnment

• adaption

• What could account for fossils of marine organisms being found on top of modern day mountain ranges?

• Land that was once a marine environment could be uplifted by Earth processes and becomes terrestial.

• What accounts for the variation Darwin observed among island species?

• The islands had different environments, and the organisms had adaptations that enabled the organism to live in those environments

• The process by which humans change a species by breeding it for certain traits

• Artificial selection

• What is the selective agent in artificial selection?• humans

• The ability of a trait to be passed down from one generation to the next

• heritability

• What is the selective agent for traits in nature?• The environment

• A mechanism by which individuals that have inherited beneficial adaptations produce more offspring on average than do other individuals

• Natural Selection

• Natural limits to population growth proposed by economist Thomas Malthus

• Food, water, shelter, disease also limits growth

• All individuals of a species that live in an area• population

• An aspect of evolution by which adaptations arose over many generations

• Descent with modification

• What English naturalist independently developed a theory similar to Darwin’s?

• Alfred Russel Wallace

• The four main principles to the theory of natural selection are

• Variation• Overproduction• Adaptation• Descent with modification

• A measure of the ability to survive and produce more offspring relative to other members of the population in a given environment.

• fitness

• Natural selection acts on ________ rather than on genetic material itself.

• phenotypes

• What two ecologists observed an example of natural selection among finches on the Galapagos island?

• Peter and Rosemary Grant

• When scientists study fossils, they take into account _______, ________,and________

• Age• Location• What the environment was like when the

organism it came from was alive.

• Darwin noted that island species most closely resembled species on the nearest_________

• mainland

• The study of the distribution of organisms around the world.

• biogeography

• Fish , birds, reptiles, and mammals all have _____ ____ as embryo’s

• Gill slits

• What does similar features of embryo’s in different organisms suggest?

• Evolution from a distant common ancestor

• Features that are similar in structure but appear in different organisms and have different functions.

• Homologous structures

• Structures that perform a similar function but are not similar in origin

• Analogous structures

• Provide an example of a homologous structure• Human hand and bat wing

• Provide an example of an analogous structure• Insect wings, bird wings

• Underdeveloped or unused features that are remnants of organs or structures that had a function in an early ancestor.

• Vestigial structure

• What type of structure would you call the stump-like limbs of a snake?

• vestigial

• Why are structures considered critical evidence of evolution?

• They are homologous to full-size features and evidence of common ancestry among organisms that share them.

• Describe how some of the Galapagos finch species, which traditionally were seed eaters, evolved over generations to prefer insects over seeds.

• On some islands, insects might have been more abundant than seeds, or there might have been less competition for insects than for seeds. The feeding behavior must have been heritable to become common in the population over time.

• How can a bat’s wing be considered both a homologous structure and an analogous structure?

• A bat wing is homologous to the forelimbs of other vertebrates. It is analogous to the wing of an insect because the wings are structurally different even though they perform the same function.

• The study of fossils or extinct organisms.• Paleontology

• Why is the fossil record not complete?• Most living things do not form into fossils when

they die. The remains are scattered by scavengers.

• Has any fossil evidence ever been found that contradicts evolution?

• No

• What genetic evidence supports evolution?• All living things have DNA• They all make the same proteins from the same

20 amino acids.• DNA sequence comparisons can be used to show

probable evolutionary relationships between species.

• How do pseudogenes support evolution?• Pseudogenes are like vestigial structures. They

are genes that no longer function but are carried along, or remain, in DNA. This provides evidence that genes change over time.

• What type of genes control the development of specific structures?

• How does this support evolution?• Homeobox genes• They indicate a very distant common ancestor

• How may protein comparisons support evolution?• A unique set of proteins are found in specific

types of cells. DNA is coded to make proteins. Cells from different species that make the same proteins have similar DNA. This suggests that they may come from a common ancestor.

• Genetic variation is stored in a population’s ________ ______.

• Gene pool

• The combined alleles of all of the individuals in a population.

• Gene pool

• A measure of how common a certain allele is in the population.

• Allele frequency

• Genetic variation comes from two main sources:• Mutation and recombination

• A random change in the DNA of a gene.• mutation

• A process in which new allele combinations form. This happens primarily during Meiosis.

• recombination

• The crossing of two different species that share common genes.

• hybridization

• A type of distribution in which the frequency is highest near the mean value and decreases toward each extreme end of the range.

• Normal distribution

• The observable change in the allele frequencies of a population over time. This type of evolution occurs on a small scale – within a single population.

• microevolution

• Natural selection can change the distribution of a trait along one of three paths:

• Directional, stabilizing, or disruptive selection.

• A type of selection that favors phenotypes at one extreme of a trait’s range.

• Directional selection

• The intermediate phenotype is favored and becomes more common in the population.

• Stabilizing selection

• This type of selection occurs when both extreme phenotypes are favored, while individuals with intermediate phenotypes are selected against by something in nature.

• Disruptive selection

• If two similar populations do not have gene flow, what happens to them over time?

• Lack of gene flow increases the chance that the two populations will evolve into different species.

• Changes in allele frequencies due to chance.• Genetic drift

• The movement of alleles from one population to another.

• Gene flow

• Genetic drift that occurs after an event greatly reduces the size of a population.

• The bottleneck effect

• Genetic drift that occurs after a small number of individuals colonize a new area.

• Founder effect

• What model describes populations that are not evolving?

• The Hardy-Weinberg Equilibrium

• What 5 conditions are necessary for a population to stay in equilibrium? (To not evolve)

• 1. A very large population (no genetic drift)• 2. No emigration or immigration (no gene flow)• 3. No mutations (No new alleles)• 4. Random mating (no sexual selection)• 5. No natural selection (all traits must equally aid

in survival)

• What five factors lead to evolution?• 1. genetic drift• 2. gene flow• 3. mutation• 4. sexual selection• 5. natural selection

• If gene flow between two populations stops for any reason, the populations are said to be _____________.

• isolated

• This type of isolation occurs when members of different populations can no longer mate successfully with one another.

• Reproductive Isolation

• The best environments for any type of fossilization include _________, _________, and areas where sediment is continuously deposited, such as __________, ___________, and ______________.

• Wetlands, bogs • river mouths, lakebeds, and floodplains.

• What processes may make a fossil?• Permineralization• Natural casts• Trace fossils• Amber preserved fossils• Preserved remains

• This type of fossilization occurs when minerals carried by water are deposited around a hard structure. They may also replace the hard structure itself.

• permineralization

• This type of fossil records the activity of an organism. They include nests, burrows, imprints of leaves, and footprints.

• Trace fossils

• This type of fossil contains organisms that became trapped in tree resin that hardens into amber after the tree gets buried underground.

• Amber-preserved fossils

• Many fossils form in _________ ______, which is made by many layers of small rock particles.

• Sedimentary rock

• Why are so few complete fossils discovered?• Specific conditions and events are required for

fossilization to occur. Only a tiny fraction meet these criteria. Rock cycling also destroys many fossils.

• This method of dating estimates the time during which an organism lived by comparing the placement of fossils of that organism with the placement of fossils in other layers of rock.

• Relative dating

• A dating technique that uses the natural decay rate of unstable isotopes found in materials in order to calculate the age of that material.

• Radiometric dating

• Atoms of an element that have the same number of protons but a different number of neutrons.

• isotopes

• What are the three naturally occurring isotopes of carbon? Describe them.

• C-12, C-13, C-14• They all have six protons. They differ by their

number of neutrons. Carbon twelve has 6 neutrons, carbon thirteen has seven, and carbon fourteen has eight neutrons.

• What are the three isotopes of hydrogen? Name and describe them.

• Protium has one proton and no neutrons• Deuterium has one proton and one neutron• Tritium has one proton and two neutrons

• As an isotope for an element decays, it may break down to form a different __________.

• element

• The decay rate for many radioactive isotopes has been measured and is expressed as the isotope’s ___________.

• Half-life

• What effect do environmental conditions such as temperature and pressure have on an element’s half-life?

• None

• C-14 decays into ____________.• N-14 in roughly 5730 years.

• Living organisms absorb carbon through eating and breathing. Carbon 14 is constantly being resupplied. What happens to carbon fourteen when an organism dies?

• The intake of carbon stops but the decay of carbon-14 continues.

• How do scientists determine the ago of the Earth?• Meteorites formed in the solar system at about

the same time as the Earth. Uranium to lead isotope ratios consistently estimate the age of the solar system, and therefore the Earth, to be 4.5 billion years old.

• Why is a uranium isotope often used rather than C-14 in radiometric dating to determine the age of the Earth?

• Carbon has a very short half life. Uranium has a half-life that may be used to measure in billions of years.

• Explain the difference between relative dating and absolute dating.

• Both relative dating and absolute dating are used to find how old a site or fossil is. Relative dating does not give specific dates, but dates a sample in context with other samples. Absolute dating gives a specific age of a sample within a margin of error.

• When mountains form, the order of rock layers can be disturbed. How could radiometric dating be used to sort out the relative ages of such rock layers?

• Disturbed rock strata may not be ordered sequentially. Radiometric dating of different layers can sort out the absolute ages of the rocks and determine the correct sequence of the strata.

• Fossils of organisms that existed only during specific spans of time over large geographic areas. They provide an additional tool to determine the age of fossils or the strata in which they are found.

• Index fossils

• What characteristics must an index fossil have?• Common, easy to identify, found widely around

the world, and only existed for a relatively brief time.

• A representation of the history of the Earth that marks major changes or events that have occurred.

• The Geologic Time Scale

• What are the three basic units of time used by the Geologic Time Scale?

• Eras, Periods, and Epochs.

• A segment of the geologic time scale that lasts for tens to hundreds of millions of years and consists of two or more periods.

• Eras

• The most commonly used units of time on the geologic time scale, lasting tens of millions of years. Each is associated with a particular type of rock system.

• Period

• The smallest units of geologic time and last several million years.

• Epochs

• Paleozoic means _____________.• Mesozoic means _____________.• Cenozoic means _____________.

• Ancient life• Middle life• Recent life

• Within the eras, the boundaries between many of the geologic periods are defined by ____ ________.

• Mass extinctions.

• The largest adaptive radiations tend to follow ____ __________.

• Mass extinctions

• Why do adaptive radiations often occur after mass extinctions?

• Mass extinctions create the opportunity for organisms to disperse across a wider range of habitats or environments. Over generations, populations evolve adaptations to the conditions of these environments.

• The most common index fossils are shells of invertebrates. Give two reasons why this is so.

• Invertebrates have been common throughout much of Earth’s history, and some had shells that are more easily fossilized than soft parts. Many shelled invertebrates lived in the ocean, where the conditions for preservation are better.

• Scientists have inferred that there have been at least five mass extinctions in Earth’s history. How would fossil evidence support this inference?

• Abrupt changes in the fossil record support this inference, where species found in older rock layers are not found in younger rock layers. Less species diversity in a younger layer may also indicate a mass extinction. After catastrophic events, there may also be boundary layers of changed sedimentation.

• French physicist Henri Becquerel discovered radioactivity in 1896, after geologists had developed the geologic time scale. How did Becquerel’s discovery help later geologists as they refined the time scale?

• Prior to Becquerel’s discovery, geologists relied exclusively on the relative dating of rock layers. Discovering radioactivity led to the development of radiometric dating, which offers absolute ages, rather than just the relative ages of rock layers.

• Scientists disagree over details of the origin of the Earth. What two key points do they agree on?

• 1. Earth is billions of years old.• 2. the conditions of our planet and its

atmosphere today are very different from an early earth.

• What gases made up the Earth’s atmosphere 3 billion years ago?

• Ammonia, water vapor, methane, and carbon dioxide.

• Roughly how long ago did oxygen become abundant in the atmosphere?

• 2 billion years ago

• What two hypotheses propose to explain how life began on earth?

• The Miller-Urey experiment and the Meteorite hypothesis

• What was the significance of the Miller-Urey experiment?

• In 1953, Miller and Urey passed electricity through gases and produced organic molecules such as amino acids and nucleotides.

• How is the Meteorite hypothesis different from the Miller-Urey experiment?

• In 1969, a meteorite fell in Australia from space. It contained more than 90 amino acids. This suggests that life could have formed in space, or on Earth.

• Describe the iron-sulfide bubble hypothesis.• In the 1990’s, biologists William Martin and

Michael Russell noted that hot iron sulfide rising from below the ocean floor combines with the cooler ocean water to form chimney-like structures made of many compartments. The walls of those compartments acted as the first cell membranes.

• Describe the lipid membrane hypothesis.• Lipid molecules spontaneously form membrane-

enclosed spheres, called liposomes. In 1992 biochemist Harold Morowitz tested the idea that at some point liposomes were formed with a double, or bilayer, lipid membrane. The liposomes then formed around organic molecules.

• A hypothesis that has gained much support in recent years proposes that ________, rather than DNA, was the genetic material that stored information in living things on early Earth.

• RNA

• _______ can copy itself, chop itself into pieces, and from these pieces make even more _______.

• RNA, RNA

• Unlike RNA, DNA needs _______ to replicate itself.

• enzymes

• What evidence supports the hypothesis that RNA was the genetic material that stored information in living things on an early Earth?

• 1. short chains of RNA will form from inorganic materials in a test tube.

• 2. If zinc is added as a catalyst, longer chains will grow.

• 3. RNA will fold into different shapes depending upon its sequence of nucleotides. This means it can perform more functions than DNA.

• Why may RNA have been replaced by DNA?• RNA does not catalyze reactions as well as

proteins.• It does not store as much information as DNA.• Natural selection may have preferred DNA over

RNA because it is more stable and less likely to either make a miscopy or mutate.

• Explain the phrase….the RNA world.• There are several hypotheses about how RNA

could have led to life. Laboratory experiments in which RNA molecules survive and self-replicate support the idea of early cells being based on RNA.

• RNA is hypothesized to be the earliest form of genetic material because it can store information, catalyze its own replication, and catalyze other reactions. Which two of these functions can DNA not do? Which two can proteins not do?

• DNA cannot catalyze its own replication or catalyze other reactions. Proteins cannot store information or catalyze their own replication.

• Single celled organisms changed Earth’s early surface by depositing _____________.

• minerals

• How did the single celled organisms of an early Earth change the atmosphere?

• They gave off oxygen as a by-product of photosynthesis.

• The first prokaryotes would have been _______, living without oxygen.

• anaerobic

• Scientists have found evidence that _______ ________ evolved more than 3.5 billion years ago.

• Photosynthetic life

• Domed, rocky structures made of layers of cyanobacteria and sediment.

• stromatolites

• How are stromatolites evidence of Earth’s early life?

• Stromatolite fossils can be as old as 3.5 billion years, which means that we know of at least one life form (cyanobacteria) that was alive at that time. Also, cyanobacteria, being photosynthetic, may have helped pave the way for aerobic life forms.

• The fossil record shows that eukaryotic organisms had evolved by ___ ________ years ago.

• 1.5 billion

• Eukaryotic cells were all _________ on an early earth.

• aerobic

• All cells in multicellular organisms today are _________.

• eukaryotic

• In the 1970’s, Biologist Lynn Margulis of the University of Massachusetts proposed the theory of _______________, which is a relationship in which one organism lives within the body of another, and both benefit.

• endosymbiosis

• This theory suggests that early mitochondria and chloroplasts were once simple prokaryotic cells that were taken up by larger prokaryotes around 1.5 billion years ago.

• endosymbiosis

• What differentiates other organelles from mitochondria and chloroplasts?

• They have their own DNA and ribosomes.

• How does sexual reproduction increase diversity among living things?

• Through gamete production and crossing-over, sexual reproduction provides genetic variation.

• How does sexual reproduction increase the chances that some individuals will survive changed environmental conditions?

• In a sexually reproductive population, there is more mixing and combining of traits than in an asexual population. Rather than depending on mutation alone to create a trait that can be advantageous, recombination of alleles can yield new traits relatively quickly, possibly allowing a population to adopt to new environmental conditions more rapidly.

• For photosynthetic organisms to become more common than those that get energy from eating organic molecules, what environmental conditions must have changed?

• In order for photosynthetic organisms to evolve and thrive, there must have been increased levels of sunlight and plenty of carbon dioxide in the atmosphere and oceans.

• According to the theory of endosymbiosis, mitochondria were once independent organisms. Do you think it’s possible that mitochondria might now be able to exist independently if removed from a cell? Describe how you could investigate this.

• Mitochondria would survive on their own if they were in a nutrient rich environment. One test would be to try to raise excised mitochondria in a cell culture, with normal eukaryotic cells as a control.

• Why would it have been advantageous to be multicellular rather than unicellular?

• Cells that cooperate could compete more effectively for energy. Increased dependence on neighboring cells would have led the cells to function as a colony.

• Multicellular organisms first appeared during the ___________ era.

• Paleozoic

• The __________ era began 248 million years ago and ended 65 million years ago. This age was called the age of reptiles because the dinosaurs roamed Earth during this era.

• Mesozoic

• What are the three periods into which the Mesozoic is divided?

• The triassic, the jurassic, and the cretaceous

• The earliest ancestors of modern humans evolved near the end of the _________. However, Homo sapiens, anatomically modern humans, did not appear until about _______ years ago.

• Tertiary, 100,000

• The oldest living primate group are the _________.

• Prosimians

• _____________, the humanlike primates, are further subdivided into the New World Monkeys, Old World Monkeys, and hominoids.

• Anthropoids