Evolution:Patterns of

Change over Time

BIOLOGY STANDARD

SB5. Students will evaluate the role of natural selection in the development of the theory of evolution.

• Relate natural selection to changes in organisms.

EVOLUTION

Evolution is the theory that organisms change over time, a

process by which modern organisms have descended

from ancient organisms.

GENETIC VARIATION

• Evolution is caused by genetic variation.

• Genetic variation comes from changes in DNA, which can be caused by:

–Crossing over (occurs during Prophase I of meiosis I)

–The random assortment of genes (during meiosis II)

–Mutations (in genes and chromosomes)

–Artificial selection–Natural selection

ARTIFICIAL SELECTION

• Artificial selection takes place with human control or direction.

• Examples of artificial selection

–Selective breeding

–Genetic engineering

EXAMPLE OFARTIFICIAL SELECTION

• Broccoli, cabbage, kale, cauliflower, and kohlrabi are common vegetables that were cultivated from forms of wild mustard.

• This is evolution through artificial selection.

NATURAL SELECTION

Natural selection is the process by which organisms that are

best suited to live in an environment survive, passing on their genetic traits to their

offspring.

NATURAL SELECTION

• Natural selection takes place without human control or direction.

• Over time, natural selection results in changes in the characteristics of the population.

ACTIVITIES

“Modeling Camouflage and Natural Selection”

“Modeling Natural Selection”

BEFORE DARWIN: LAMARCK’S THEORY OF

EVOLUTION

LAMARCK: USE AND DISUSE

• Any organ that is used more will grow larger & stronger

• Areas that are used less will become smaller & weaker

LARMARCK: INHERITANCE OF ACQUIRED

TRAITS• Any characteristic an organism

possesses will be passed on to its offspring.

• For example:

–Giraffes have long necks because they had to reach the

food in trees this caused their

necks to become larger

according to use and disuse.

–Giraffes with long necks then passed on these long necks to their offspring according to transmission of acquired characteristics.

Lamarck believed that the long necks of giraffes evolved as generations of giraffes

reached for ever higher leaves.

CHARLES DARWIN’S THEORY OF EVOLUTION

DARWIN’S THEORY OF EVOLUTION

• The theory of evolution was proposed by Charles Darwin after observing the plants, animals, and fossils of the Galapagos Islands.

• Darwin noticed that species varied from island to island.

ACTIVITIES

“Graphing Bird Adaptations”

“Comparing Adaptations of Birds”

SUMMARY OFDARWIN’S THEORY

1. Individual organisms in nature differ from one another. Some of this variation is inherited.

2. Organisms in nature produce more offspring than can survive, and many of those that survive do not reproduce.

3. Because more organisms are produced than can survive, members of each species must compete for limited resources.

4. Because each organism is unique, each has different advantages and disadvantages in the struggle for existence.

5. Individuals best suited for their environment survive and reproduce most successfully. The characteristics that make them best suited to their environment are passed on to offspring. Individuals whose characteristics are not as well suited to their environment die or leave fewer offspring.

6. Species change over time. Over long periods, natural selection causes changes in the characteristics of a species, such as in size and form. New species arise, and other species disappear.

7. Species alive today have descended with modifications from species that lived in the past.

8. All organisms on Earth are united into a single tree of life by common descent.

TERMS TO KNOW

HOMOLOGOUS STRUCTURES

structures which have different mature forms but develop from

the same embryonic tissue

ANALOGOUS STRUCTURES structures which look and function similarly but do not share the same evolutionary

history

Bat wings and bird wings are analogous as flight structures: their structure and

function have evolved by different routes from a flightless reptilian ancestor.

Note that a good portion of the flight surface in bats consists of a

membrane stretched between the extended bones, whereas the bones

of the bird are relatively small and do not support the flight surface.

MICROEVOLUTION

• Evolution that occurs within the species level

• Microevolution results in the creation of new species.

• New species evolve as populations become reproductively isolated from each other

EXAMPLES OF REPRODUCTIVE ISOLATION

• Behavior (behavior isolation)

• Geography (geographic isolation)

• Reproductive timing (temporal isolation)

SPECIATION

• The development of one or more species from an existing species.

• Historical example of speciation–Darwin’s finches

• Current example of speciation–Diane Dodd’s fruit fly experiment

SPECIATION CONT’D

Diane Dodd’s fruit fly experiment suggests that isolating populations in different

environments (e.g., with different food sources) can lead to the beginning of

reproductive isolation. These results are consistent with the idea that geographic isolation is an important step of some

speciation events.

MACROEVOLUTION

large scale evolutionary changes that take place over long periods of time; evolution

between different species

Macroevolution can be

represented by the

evolutionary tree.

BIOLOGY STANDARD

SB5. Students will evaluate the role of natural selection in the development of the theory of evolution.

• Trace the history of the theory.• Explain the history of life in terms of

biodiversity, ancestry, and the rates of evolution.

• Explain how fossil and biochemical evidence support the theory.

THE HISTORY OF LIFE

FOSSILS

• Fossils are the mineralized remains of animals or plants or other artifacts such as footprints.

• The totality of fossils and their placement in rock formations and sedimentary layers (strata) is known as the fossil record.

http://en.wikipedia.org/wiki/Fossil

• The fossil record provides evidence about the history of life on Earth. It also shows how different groups of organisms have changed over time.

• The fossil record reveals that fossils occur in a particular order: some only in older rock and some only in more recent rock.

• The study of fossils is called paleontology.

DATING FOSSILS

• Relative dating allows paleontologists to estimate a fossil’s age compared with that of other fossils.

• In radioactive dating, scientists calculate the age of a sample based on the amount of

remaining radioactive isotopes it contains.

• Scientists use the half-life of radioactive isotopes to date fossils.

HALF-LIFE

• A half-life is the length of time required for half the radioactive atoms in a sample to decay.

• Radioactive isotope with a short half-life: carbon-14 (5730 years)–Used to date younger fossils

• Radioactive isotope with a long half-life: potassium-40 (60,000 years)–Used to date older fossils

GEOLOGIC TIME SCALE

In the geologic time scale, time is divided the eon, era, period, and epoch.

• Remember that macroevolution is the large scale evolutionary change that takes place over long periods of time.

• The events of macroevolution are reflected in the geologic time scale.

EVOLUTION OF LIFE

• Early Earth was hot; atmosphere contained poisonous gases.

• Earth cooled and oceans condensed.

• Simple organic molecules may have formed in the oceans.

• Small sequences of RNA may have formed and replicated.

• First prokaryotes may have formed when RNA or DNA was enclosed in microspheres.

• Later prokaryotes were photosynthetic and produced oxygen.

• An oxygenated atmosphere capped by the ozone layer protected Earth.

• First eukaryotes may have been communities of prokaryotes. (endosymbiosis)

• Multicellular eukaryotes evolved.• Sexual reproduction increased

genetic variability, hastening evolution.

The Atmosphere of Early Earth

• Earth’s early atmosphere probably contained hydrogen cyanide, carbon dioxide, carbon monoxide, nitrogen, hydrogen sulfide, and water.

• Thunderstorms predominated.• Primitive oceans were brown from

dissolved iron deposits.

Could organic molecules have evolved under the conditions of early Earth?

• In the 1950s, Stanley Miller and Harold Urey tried to answer this question.

• A flask was filled with hydrogen, methane, ammonia, and water to represent the conditions of early Earth.

• The flask was sealed to eliminate the possibility of contamination by microorganisms (bacteria, viruses, and fungi).

• Electric sparks were passed through the mixture to simulate the lightning strikes of the early atmosphere.

• Over a few days, several amino acids (the building blocks for proteins) began to accumulate.

• Miller and Urey’s experiments suggested how mixtures of organic compounds could have arisen from simpler compounds present in early Earth.

• Later experiments found that the Miller/Urey simulation was not accurate.

• However, similar experiments based on current knowledge of Earth’s early atmosphere have also produced organic compounds.

BIOLOGY STANDARD

SB5. Students will evaluate the role of natural selection in the development of the theory of evolution.

• Explain the history of life in terms of biodiversity, ancestry, and the rates of evolution.

• Explain how fossil and biochemical evidence support the theory.

PATTERNS OF MACROEVOLUTION

• Five of the six patterns of macroevolution are –mass extinctions–adaptive radiation–convergent evolution–punctuated equilibrium–gradualism

MASS EXTINCTION

• Extinction is the dying out of a species.

• Mass extinction is the widespread destruction of a species caused by many factors.

ACTIVITY

Reading a Geologic Time Scale

The Mass Extinction of the Dinosaurs: The Asteroid-

Impact Hypothesis

Luis and Walter Alvarez

Luis, along with his son Walter, proposed the asteroid-impact hypothesis.

• At the end of the Cretaceous period, the dinosaurs, along with many species of aquatic and terrestrial organisms, became extinct.

• In 1980, Luis Alvarez, along with his son Walter, proposed the asteroid-impact hypothesis.

• The asteroid-impact hypothesis suggests that a huge asteroid hit the Earth, sending so much dust into the atmosphere.

• This dust blocked the sun, which caused a change in the Earth’s climate.

• This change in climate led to the mass extinction.

• Alvarez and Alvarez noted that sediments from the end of the Cretaceous period contained high concentrations of iridium.

• Iridium is rare in the Earth’s crust, but it is abundant in asteroids and other extraterrestrial bodies.

• Quartz crystals, deformed by a powerful force, were also found in sediments of this time period.

• Further evidence for this hypothesis was provided by the possible site of impact, the Chicxulub crater located on the Yucatan Peninsula in southern Mexico.

• The crater dates from the end of the Cretaceous period and is (180 km) 110 miles across.

The Chicxulub of the Yucatan Peninsula

ADAPTIVE RADIATION• A single species or a small group of

species has evolved into several different forms that live in different ways.

• Examples

–Darwin’s finches

–The extinction of dinosaurs cleared the way for the adaptive radiation of many species of mammals.

• Figure legend: Adaptive Radiation. New groups come from a common ancestor. These new groups are suddenly able to exploit new habitats. If these groups eventually become reproductively isolated, they may become new species.

CONVERGENT EVOLUTION

The process by which

unrelated organisms come to

resemble each other.

PUNCTUATED EQUILIBRIUM

• After long stable periods (equilibrium), new species are produced by shorter periods of rapid change.

• Evolution is believed to occur at different rates for different organisms at different times.

GRADUALISM

Gradualism is evolution that occurs over a long period of time when adaptive changes accumulate slowly and steadily over time in a population.

Gradualism vs. Punctuated Equilibrium

Selection

Define:a.Stabilizing selectionb.Disruptive selectionc.Directional selection

BIOLOGY STANDARD

SB5. Students will evaluate the role of natural selection in the development of the theory of evolution.

• Recognize the role of evolution to biological resistance (pesticide and antibiotic resistance).

EVOLUTION AND PESTICIDE

RESISTANCE

Destruction of Natural Enemies

Development of Resistance