History of the Earth

Ch 14

Chapter 14 Vocabulary:

• 1. Fossil

• 2. Law of superposition

• 3. Radiometric dating

• 4. Spontaneous generation

• 5. Biogenesis

• 6. endosymbiont theory

SC.912.L.15.1Ch 14 Explain how the scientific theory of evolution is supported

by the fossil record, comparative anatomy, comparative embryology, biogeography,

molecular biology, and observed evolutionary change.

How Did Life Begin?

The Earth formed about 4.6 billion years ago according to evidence obtained by radiometric dating.

• The age of the rocks and the fossils in them can be determined by the position and the amount of radioactive material in the rocks.

• Law of superposition

Radiometric Dating or ½ life

½ life • Compare it to the amount of time it takes for ½ of the carbonation in this bottle to leave… if we know how much time it takes, we could calculate the age of the bottle of soda based on how much carbonation was left in the container.

Radiometric dating

• Gives a numerical age

• Places rocks and fossils in a time period

• Uses isotopes that decay at a constant rate

• Uses isotopes that decay very slowly/ have a long ½ life.

fossil• A fossil is any preserved evidence of an

organism.

• They form best in sedimentary rocks

• They can be evidence or an organism, like foot prints or actual remains.

• What do fossils tell us and how do we know how old they are?

The fossils in the bottom layer of rock are older

• Fossils show evidence of change in organisms, what types of organisms lived in each time period and that the complexity has increased over time.

• We know how old they are by relative positions and radiometric dating.

Law of superposition!

• Youngest are on the top

• Oldest are on the bottom

• unless they have been disturbed!

The geologic time scale

• is a model of the history of Earth showing the major events that occurred along the way.

• The longest units of time are eons and include the Precambrian time and Phanerozoic.

• The second largest unit of time is called an era and includes the Precambrian, Paleozoic, Mesozoic and Cenozoic.

• Each era can be divided into parts called periods and periods may be divided into the smallest parts called epochs.

• The history of the earth is broken up into a set of divisions for describing geologic time.

• the generally accepted divisions are

• eon • era • period • epoch • age

PRECAMBRIAN• SO LONG AGO…

• We know little due to deformation of rock layers.

• Large areas of Precambrian rock exposed are called shields. North America’s is called the Canadian shield.

Precambrian life• Fossils are rare • Simple organisms

with soft bodies• Volcanic activity

heat and pressure “erased” the fossil evidence.

• Stromatolites blue-green algae were common.

• 14. Sum up what events occurred in Precambrian time. Makes up almost 90% of Earth’s history, earth formed, first life appeared, autotrophs released oxygen into the atmosphere, Eukaryotes developed. At the end the first animals developed. Simple animals lived in the oceans

Paleozoic Era

Paleozoic Era: Life

• trilobites

Brachiopods are marine animals that, upon first glance, look like clams

Paleozoic• Lots of fossils

• Trilobites index fossil

• Invertebrates, worms, jellyfish, snails vertebrates appear

• Fish, amphibians

• Insects

• Reptiles

• .

• 15. Sum up the Paleozoic Era. Explosion of life! Fish, land plants and insects appeared. First tetrapods or land vertebrates appeared reptiles arrived at the end of the Paleozoic

Mesozoic Era

Mesozoic Erathe age of the reptiles

Dinosaurs and other archosaurs, such as the pterosaurs, dominated

the land biota. . .

• 17. Sum up the Mesozoic era. Mammals and dinosaurs appeared. Flowering plants, birds evolved from dinosaurs. The age of the reptiles

Impact theory

• No dinosaurs found after the cretaceous- tertiary

• What happened?

• Possible impact hypothesis

• 18. What makes scientists think a meteor hit the earth during the cretaceous time period? There is iridium found in the rock layers called the KT boundary. Iridium is found mostly in objects from space, like a meteor.

• 19. How might a meteor impact cause a mass extinction? The debris could cause global climate changes

• 20. What other major geological event occurred during the Mesozoic era? Pangaea the single land mass moved so that the continents were roughly in their current position by the end of the Mesozoic era.

Cenozoic Age of the Mammals

Cenozoic• The continents moved to their current

positions.

• Alps Himalayas formed

• Small rodents, early horse, and bats

• Ice cap formed

• Land bridges formed Ice age

• Early ancestors to humans fossils found

• 21. What is the most recent era? The Cenozoic era

• 22. What are the most dominant organisms in the Cenozoic era? Mammals

• 23. When did humans arrive on earth? at the very end of the time scale

What life do we associate as occurring during the Mesozoic era?

• Dinosaurs

How do we think the extinction of the dinosaurs happened?

• giant asteroid hit earth

Humans and large mammals appeared in the Era called what?

• Cenozoic

Section 2 The Origin Of Life

• 4. Spontaneous generation

• 5. Biogenesis

• 6. endosymbiont theory

What were the conditions of early Earth like?

Hot, meteorites, volcanoes .Minerals in the oldest known rocks suggest that the earth’s atmosphere had little or no oxygen

The primordial soup model and the bubble model propose explanations of the origin of the chemicals of life.

Scientists think RNA formed before DNA or proteins formed.

• As the earth cooled from the liquid rock to the solid rock eventually the liquid water formed the oceans

Francesco Redi performed a controlled experiment with flies and

maggots to test this idea on the origin of life.

• 1668 - He disproved spontaneous generation of maggots, by demonstrating absence of maggots on meat protected from flies.

Spontaneous generation

• Some people believed that life could just develop from non life!

• In one of the first examples of a biological experiment with proper controls, Redi set up a series of flasks containing different meats, half of the flasks sealed, half open. He then repeated the experiment but, instead of sealing the flasks, covered half of them with gauze so that air could enter.

Louis Pasteur

• disproved this theory with pasteurization. He used the swan necked flask to do this

biogenesis

• Life from life!

• Replaced the spontaneous generation idea!

Scientists think that the first cells may have developed from microspheres.

The development of heredity made it possible for organisms to pass traits to subsequent generations.

Primordial soup Model of lifeor Chemical evolution

• Energy from sunlight and lightning allowed the first organic molecules to form.

Miller and UreyOparin thought the Earth’s early atmosphere provided what was needed to make the first organic molecules.

Who did an experiment to try to replicate the conditions of the early earth? Miller and Urey.6. What did they find in the mixture that they formed? Amino acids.

Miller & Urey’s experiment

Why did Miller and Urey do their experiment?

• To try to figure out how life might have originated on earth!

• Did they produce organic molecules from inorganic molecules?

• Yes!

• Did they produce life from non life?

• NO!

7. What do scientists believe was the first genetic code? RNA

Order of events

• abiotic synthesis of amino acids and other organic molecules /

• synthesis of proteins /

• Proto cells, membranes/

• development of a genetic code / RNA 1st

• evolution of cells

Complex Organisms Developed

Prokaryotes are the oldest organisms and are divided into two groups, archaebacteria and eubacteria or Archea and Bacteria

Prokaryotes likely gave rise to eukaryotes through the process of endosymbiosis.

• 8. What evidence is there of life 3.8 billion years ago on Earth? Fossilized microbes in volcanic rock.

• 9. What type of organisms were the first? Prokaryotic /archea

Endosymbiont Theory Endosymbiosis

Lynn Margulis proposed this idea to explain the origin or organelles such as the mitochondria and chloroplasts

Endosymbiosis Hypothesis

Mitochondria and chloroplasts are thought to have evolved through endosymbiosis, or the endosymbiotic theory.

Multicellularity arose many times and resulted in many different groups of multicellular organisms.

• 13. What is the endosymbiotic theory? The ancestors of eukaryotic cells lived together in association with prokaryotic cells.

• Extinctions influenced the evolution of the species alive today. After mass extinctions there were increases in biodiversity that can be observed in the fossil records.

• These mark the changes from one era to the next!

• The new niches opened up by the extinction provided opportunities for the surviving species to expand and evolve!

Life Invaded the Land

Ancient cyanobacteria produced oxygen, some of which became ozone. Ozone enabled organisms to live on land.

.

ozone

• 10. Eventually cyanobacteria could perform photosynthesis and release what? Oxygen

• 11. With a layer of ozone in place over the earth, what type of organisms evolved next? Eukaryotic

• 12. How long ago did eukaryotic cells evolve? 1.8 billion years

• Plants and fungi formed mycorrhizae and were the first multicellular organisms to live on land

fungi

Arthropods were the first animals to leave the ocean.

The first vertebrates to invade dry land were amphibians. tetrapods

The extinction of many reptile species enabled birds and mammals to become the dominant vertebrates on land.

The movement of the continents on the surface of the Earth has contributed to the geographic distribution of some species.

• The fossil record also provides an amazing amount of evidence concerning common ancestors.

• Fossilized remains of invertebrates (animals without an internal skeleton), vertebrates, and plants appear in the strata or layers of Earth's surface in the same order that the complexities of their anatomy suggest.

• The more evolutionarily distant organisms lie deeper, in the older layers, beneath the remains of the more recent organisms.

• Geologists are able to date rock strata with reasonable accuracy, and the age of a layer always correlates with the fossils discovered there.

• In other words, there would never be a stratum dating back 400 million years that contained fossils of mastodons, which evolved much later.

•Chapter 15 Evolution

Chapter 15 Vocabulary:

• 1. Natural selection. • 2 artificial selection • 3. Evolution • 4. Homologous structure • 5. Vestigial structure • 6. Analogous structure • 7. Camouflage • 8. Mimicry • 9. Fitness • 10. Hardy Weinberg principle • 11. Genetic drift

3. Evolution

• CHANGE!

• Biologists use it to mean cumulative changes in organisms through time.

• Like the bacteria that as a population becomes resistant to the antibiotics….

artificial selection

• The process of directed breeding to produce offspring with desired traits.

Natural selection.• Nature selects the traits best suited for survival based on

the following criteria:• 1. organisms in a population are naturally different from

each other.• 2. the differences are inherited from their parents and can

be passed on to their offspring.• 3. Populations tend to overproduce, there is not enough

food or resources for the number produced leading to competition

• 4. Some of the variations provide an advantage to the ability to survive and reproduce more offspring compared to the others with out that variation.

• Natural selection is a way in which evolution can take place.

• It is an attempt to explain how the changes Darwin observed might have happened.

• Wallace and Darwin both wrote essays with almost the exact same conclusion.

The Theory of Evolution by Natural Selection

● Based on years of observations during a trip Darwin wrote a book On the Origin of Species.

Darwin’s trip

● Darwin was influenced by Thomas Malthus, who wrote that populations tend to grow as much as the environment allows.

Populations grow rapidly if there is enough food and space. But usually there are limits!

4. Homologous structure

• Anatomically similar structures inherited from a common ancestor. They may not perform the same function but have a common origin or structure internally..

Homologous structures

5. Vestigial structure

• Structures that are reduced in size and form, but are similar in structure to functioning structures in other organisms.

• Examples:

• Though their ancestors ceased to walk on four legs many millions of years ago, snakes still possess vestigial hind limbs as well as reduced hip and thigh bones.

6. Analogous structure

• Superficially similar features.

• Such as wings of an insect and of a bird…no relationship in the structure exists!

camouflageThe adaptation that allows an organism to blend in with their environment.

8. Mimicry • One species evolves to look like another.

9. Fitness • A measure of the relative

contribution that an individual trait makes to the next generation.

• This is usually the number of reproductively viable offspring an organism makes in the next generation.

• Better fit means better able to survive and reproduce

● Darwin proposed that natural selection favors individuals that are best able to survive and reproduce.

● Under certain conditions, change within a species can lead to new species.

Evidence of Evolution

● Evidence of orderly change can be seen when fossils are arranged according to their age.

● ● Similarities of structures in different vertebrates provide evidence that all vertebrates share a common ancestor.

• In some cases widely divergent organisms possess a common structure, adapted to their individual needs over countless generations yet reflective of a shared ancestor. A fascinating example of this is the pentadactyl limb, a five-digit appendage common to mammals and found, in modified form, among birds. The cat's paw, the dolphin's flipper, the bat's wing, and the human hand are all versions of the same original, an indication of a common four-footed ancestor that likewise had limbs with five digits at the end.

• The embryonic forms of animals also reflect common traits and shared evolutionary forebears. This is why most mammals look remarkably similar in early stages of development. In some cases animals in fetal form will manifest vestigial features reflective of what were once functional traits of their ancestors.

Differences in amino acid sequences and DNA

sequences are greater between species that are

more distantly related than between species that are

more closely related.

• Comparing DNA sequences is one way Biologists determine how closely related organisms are.

SC.912.L.15.14

• ch 15 Discuss mechanisms of evolutionary change other than natural selection such as genetic drift and gene flow.

• There are several ways that evolution can occur besides natural selection.

• Now that scientists understand genes they can explain these much better.

• Population genetics is one.

10. Hardy Weinberg principle

• 1. Hardy Weinberg states that unless there are outside forces a population will stay in what?

• Genetic equilibrium

P2 + 2pq + q2 = 1

• p is the dominant allele

• q is the recessive allele,

• P2 = homozygous dominant• q2= homozygous recessive

• and 2pq is the heterozygous genotype.

Gene pool

Hardy Weinberg requirements

• No genetic drift,

• No gene flow

• no mutations

• Mating must be random

• No natural selection

11. Genetic drift • Any change in the allelic frequencies in a

population that results from chance.

• Types of genetic drift• Founder effect: an extreme example of genetic drift

when a small group moves away from a population. The group carries a small sample of the larger groups alleles, if variations are present, they may start to show up more in the small sub set.

• Bottleneck: when a population declines to a very small number and then rebounds the genes in the small group are what are carried on.

Genetic drift

• It will randomly alter gene pools of small populations more than large ones!!!!

• Think Amish ! Extra fingers or toes!• Polydactyly -- extra fingers or sometimes toes -- is one symptom of

Ellis-van Creveld syndrome. The syndrome is commonly found among the Old Order Amish of Pennsylvania, a population that experiences the "founder effect." Genetically inherited diseases like Ellis-van Creveld are more concentrated among the Amish because they marry within their own community, which prevents new genetic variation from entering the population. Children are therefore more likely to inherit two copies of the particular recessive genes that lead to genetic disease.

Gene flow

• Only isolated populations have no gene flow! This is very rare.

Non random Mating

• Most organism mate with others near them. This can lead to inbreeding and can change the allelic frequencies.

mutations

• Most mutations are random and will cause changes in the allelic frequencies so this will keep a population out of genetic equilibrium!

• Natural selection is one mechanism of evolution.

• How it happens…

Natural selection

• Most organisms are not equally adapted to their environment, so natural selection will occur.

• There are different types of Natural selection.

• Stabilizing selection is the most common and removes the extremes.

• Directional selection selects one phenotype over another.

• Disruptive selection selects the extreme.

• Sexual selection is based on the ability to attract a mate.

Examples of Evolution

● Individuals that have traits that enable them to survive in a given environment can reproduce and pass those traits to their offspring.

●The moth example is directional selection

Industrial Melanism and the Pepper Moth

• Both natural selection and mutation play a role in industrial melanism, a phenomenon whereby the processes of evolution can be witnessed within the scale of a human lifetime.

• Industrial melanism is the high level of occurrence of dark, or melanic, individuals from a particular species (usually insects) within a geographic region noted for its high levels of dark-colored industrial pollution.

• With so much pollution in the air, trees tend to be darkened, and thus a dark moth stands a much greater chance of surviving, because predators will be less able to see it.

• At the same time, there is a mutation that produces dark-colored moths, and in this particular situation, these melanic varieties are selected naturally.

• On the other hand, in a relatively unpolluted region, the lighter-colored individuals of the same species tend to have the advantage, and therefore natural selection does not favor the mutation.

• The best-known example of industrial melanism occurred in a species known as the pepper moth, or Biston betularia, which usually lives on trees covered with lichen.

• Prior to the beginnings of the Industrial Revolution in England during the late eighteenth century, the proportion of light-colored pepper moths was much higher than that of dark-colored ones, both of which were members of the same species differentiated only by appearance

• As the Industrial Revolution got into full swing during the 1800s, factory smokestacks put so much soot into the air in some parts of England that it killed the lichen on the trees, and by the 1950s, most pepper moths were dark-colored.

• It was at that point that Bernard Kettlewell (1907-1979), a British geneticist and entomologist (a scientist who studies insects), formed the hypothesis that the pepper moths' coloration protected them from predators, namely birds.

• Kettlewell therefore reasoned that, before pollution appeared in mass quantities, light-colored moths had been the ones best equipped to protect themselves because they were camouflaged against the lichen on the trees.

• After the beginnings of the Industrial Revolution, however, the presence of soot on the trees meant that light-colored moths would stand out, and therefore it was best for a moth to be dark in color.

• This in turn meant that natural selection had favored the dark moths

• In making his hypothesis, Kettlewell predicted that he would find more dark moths than light moths in polluted areas, and more light than dark ones in places that were unpolluted by factory soot.

• As it turned out, dark moths outnumbered light moths two-to-one in industrialized areas, while the ratios were reversed in unpolluted regions, confirming his predictions.

• To further test his hypothesis, Kettlewell set up hidden cameras pointed at trees in both polluted and unpolluted areas.

• The resulting films showed birds preying on light moths in the polluted region, and dark moths in the unpolluted one—again, fitting Kettlewell's predictions

Directional selection!

Types of selection other than Natural selection●

adaptive radiation• One common ancestor gives rise to many species based on the

environments. A good example would be the birds of the Galapagos Islands

allopatric speciation• In allopatric speciation, an

ancestral population is geographically isolated, resulting in the evolution of separate species largely due to genetic drift. The additive effect of differences due to genetic drift can eventually result in behavioral isolation (refusal to mate) if the two groups were to meet again in the future. If they refused to interbreed, they would be considered separate species.

Allopatric speciation

• A physical barrier divides one population into two or more populations

• when the Colorado River cut open the Grand Canyon, separating groups of squirrels who lived in the high-altitude pine forest. Eventually, populations ceased to interbreed, and today the Kaibab squirrel of the northern rim and the Abert squirrel of the south are separate species.

sympatric speciation• Sympatric speciation involves speciation without a geographic

barrier. • One example of sympatric speciation is polyploidy, found more often

in plants. • Polyploidy occurs when a failure of meiosis increases the number

of chromosome sets to 3N or more. At this point, the two "cousin" species can no longer mate with each other.

directional selection,

• When one extreme phenotype is favored by natural selection, the distribution of the phenotype shifts in that direction.

disruptive selection• Selection that favors the

extremes of a population trait is DISRUPTIVE SELECTION.

An example of this would be the size of clams.  Predators find it harder to locate smaller clams and are unable to pry open larger clams.  Predators favor clams of a medium size.

genetic driftGenetic drift - random events due to small

population size. Random events have little effect on large populations. Consider a population of 1 million almond trees with a frequency of r at 10%. If a severe ice storm wiped out half, leaving 500,000, it is very likely that the r allele would still be present in the population. However, suppose the initial population size of almond trees were 10 (with the same frequency of r at 10%). It is likely that the same ice storm could wipe the r allele out of the small population.

founder effect and bottle neck

• Reduction in genetic variability makes these species vulnerable to disease and environmental changes!

gradualismGradualism is the slow change from one form

to another.

• The opposite of gradualism is:

• Punctuated equilibrium which implies long periods without appreciable change and short periods of rapid evolution. Volcanic eruptions and meteor impacts affecting evolution on Earth could cause these changes.

sexual selection• Sexual selection may produce elaborate

characteristics, for example the feathers of a male peacock or the ornamental plumage of male birds of paradise. Other organisms such as elephant seals fight over territories.

stabilizing selection

Stabilizing selection occurs when the intermediate, or most common, phenotype is favored. 

This type of selection tends to narrow the variation in the phenotype over time. 

This is the most common type of selection because it is associated with the adaptation of an organism to the environment.

Speciation begins as a population adapts to its environment.

● Reproductive isolation keeps newly forming species from breeding with one another.

Speciation:

• the formation of a new species by splitting of an existing species.

Write the term or phrase that best completes each statement. Use these choices: adaptive radiation, allopatric speciation, directional selection, disruptive selection, founder effect, genetic drift, gradualism, sexual selection, stabilizing selection, sympatric speciation

1. ________________________ is a change in allelic frequencies in a population that is due to chance.

2. ________________________ removed individuals with average trait values, creating two populations with extreme traits.

3. The most common form of selection, ___________________________, removes organisms with extreme expressions of a trait.

4. When a small sample of the main population settles in a location separated from the main populations, the ___________________________ can occur.

5. In _________________________, a species evolves into a new species without any barriers that separate the populations.

6. __________________________ will shift populations toward a beneficial but extreme trait value.

7. In __________________________, a population is divided by a barrier, each population evolves separately, and eventually the two populations cannot successful interbreed.

8. __________________________ is a change in the size or frequency of a trait based on competition for mates.

9. One species will sometimes diversify in a relatively short time into a number of different species in a pattern called ________________________________.

10.The idea that evolution occurred in small steps over millions of years in a speciation model is currently known as ________________________________. 

Write the term or phrase that best completes each statement. Use these choices: adaptive radiation, allopatric speciation, directional selection, disruptive selection, founder effect, genetic drift, gradualism, sexual selection, stabilizing selection, sympatric speciation

1. genetic drift is a change in allelic frequencies in a population that is due to chance.

2. disruptive selection removed individuals with average trait values, creating two populations with extreme traits.

3. The most common form of selection, stabilizing selection, removes organisms with extreme expressions of a trait.

4. When a small sample of the main population settles in a location separated from the main populations, the founder effect can occur.

5. In sympatric speciation , a species evolves into a new species without any barriers that separate the populations.

6. directional selection will shift populations toward a beneficial but extreme trait value.

7. In allopatric speciation , a population is divided by a barrier, each population evolves separately, and eventually the two populations cannot successful interbreed.

8. sexual selection is a change in the size or frequency of a trait based on competition for mates.

9. One species will sometimes diversify in a relatively short time into a number of different species in a pattern called adaptive radiation.

10. The idea that evolution occurred in small steps over millions of years in a speciation model is currently known as gradualism .