Principles of Evolution - Mass Instruction

Principles of Evolution Chapter 10 What is evolution? The Simpsons Evolve

What is evolution? Evolution is the process of biological change by which descendants differ from their ancestors. A species is a group of organisms so

similar to one another that they can reproduce and have fertile offspring. All of these organisms are related by a common ancestor! QuickTime and a TIFF (Uncompressed) decompressor

are needed to see this picture. QuickTime and a TIFF (Uncompressed) decompressor are needed to see this picture. Early Ideas About Evolution Carolus

Linnaeus Developed a classification system to group organisms based on their similarities The system reflects evolutionary relationships

Early Ideas About Evolution Georges Louis Leclerc de Buffon Proposed that species shared ancestors instead of arising separately Suggested that the Earth is very old

Early Ideas About Evolution Erasmus Darwin Proposed that all living things descended from a common ancestor

Proposed that more complex forms of life arose from less complex forms Early Ideas About Evolution Jean-Baptiste Lamarck

Proposed that all organisms evolve toward perfection and complexity Proposed that changes in the environment lead to changes in an organism, which could be passed on to the offspring Geologic Change In

early debates, the Earth was believed to be only about 6,000 years old Geologic Change Fossils are traces of organisms that

existed in the past It was discovered that each stratum (rock layer) had its own type of fossils Fossils in the deepest strata were much different than the ones in the topmost strata Geologic Change

Catastophism states that natural disasters shaped landforms. These changes caused species to

become extinct Geologic Change Gradualism states that landforms change very slowly

over a long period of time Species adapted to the environmental changes slowly Geologic Change

Uniformitarianism states that the geologic processes that shape the Earth are uniform through time Suggests that

changes are both gradual and ongoing Video Break! Theory of Evolution in 3.5 Minutes Re-route, Put after nat sel

Charles Darwin In 1831, Darwin set sail from England to South America The Galpagos Islands off the Eastern coast of South America is where Darwin

began observing variations. Variation is the difference in physical traits between individuals of the same group. Darwins Observations Darwin observed differences between

the species on nearby islands. Most notable were Darwins Finches Darwins Finches Finches with strong, thick beaks lived in areas where hard

shelled nuts were available to eat Darwins Finches Finches with slender beaks lived in areas

where insects and soft fruits were available to eat. Darwins Finches Darwins Finches

Darwins Finches Darwins Observations These observations led to the idea that species may be able to adapt to their environment

An adaptation is a feature that allows an organism to better survive in its environment Adaptations can lead to genetic change in a population over time Darwins Fossil Observations He

found fossils that looked similar to living organisms and thought they must be related somehow Natural Selection

Darwin conducted research for over 20 years to further develop his theory of evolution He began observing the work of farmers and animal breeders and even began breeding his own pigeons

After much research, he came up with the theory of natural selection to explain how evolution occurs Natural Selection Heritability is the ability of a trait to be

passed down from one generation to the next Artificial selection is a process by which humans change a species by breeding it for certain traits Ex: dog breeding Natural Selection

Natural Selection Darwin realized that if breeders can select for desirable traits, they can also select against undesirable ones If humans are the selective agent in

artificial selection, then the environment is the selective agent in natural selection Natural Selection Natural selection is a mechanism by which

individuals that have inherited beneficial adaptations produce more offspring on average than do other individuals Traits are passed on only if they are advantageous to the organism in the current environment More offspring = passing on genes

Natural Selection Darwin had observed in the Galpagos that some individuals in a given population had variations that were particularly advantageous in their environment

He realized that these adaptations occurred over many generations Descent with Modification Natural Selection Natural selection can act only on traits

that already exist. Natural Selection - 4 Main Principles Variation - Heritable differences in the population are the basis for natural selection

Overproduction - Having many offspring raises the chance that some will survive and pass on your traits Natural Selection - 4 Main Principles

Adaptation - Certain traits may allow an individual to better survive in its environment. They are naturally selected to survive and produce more offspring and pass on those useful traits. Descent with Modification - Over time, natural selection results in species with adaptations

that are well suited for survival and reproduction in the environment Natural Selection As long as the environmental conditions continue to remain beneficial to the trait,

the trait will continue to be passed from generation to generation If the environment changes, the traits that were originally beneficial may no longer be favorable 1977 Island Drought Natural Selection Example

Peppered moth is a species of moth from Europe They are either white colored or black Originally, the majority of peppered moths were white, which was effective camouflage against the light-colored

tree bark Natural Selection Example Effective camouflage = better survival = that trait was passed on from generation to generation

The black moths stood out against the light tree bark, and were more easily spotted by predators Natural Selection Example During the Industrial Revolution, the

lichens on the tree bark died, causing the trees to now have dark bark White moths began to die off, while the black ones flourished Natural Selection Fitness

- A measure of the ability to survive and produce more offspring relative to other members of the population in a given environment Survival of the fittest

Many people think that natural selection leads to the most complex or most perfect individuals ever, and that less fit individuals are wiped out or considered more simple In reality, the individuals that are most fit are only most fit for the current environmental conditions. These conditions can change at any time.

Less fit individuals are not necessarily wiped out--they have to compete more and may reproduce less offspring. Finally, organisms do not seek to become more complex. If a certain set of adaptations is beneficial for the environment, they will continue to be passed down, no matter how simple they seem Evidence for Evolution - Fossils

Fossils in deeper layers of rock are older than fossils in shallower layers Fossil sequences suggested descent with modification Transitional fossils

Evidence for Evolution - Fossils Transitional fossils between whales and mammals - see pg 300

Evidence for Evolution - Geography Darwin found that the finches on the Galpagos islands were similar, but had different adaptations Local adaptations All shared a common ancestor from the

mainland Evidence for Evolution - Embryology The embryos of many vertebrates are very similar Gill slits, tails

Suggests a common ancestor Evidence for Evolution - Anatomy Homologous structures are features that are similar in structure, but differ in function in different species

Suggests a common ancestor Common example: forelimb of tetrapod vertebrates Evidence for Evolution - Anatomy Vestigial structures are remnants of

organs or structures that had a use in an earlier ancestor, but do not anymore Ostrich wings Snake leg bones Human appendix Can suggest adaptation or a common ancestor Evidence for Evolution - DNA

DNA can be analyzed and compared between organisms The more similar the DNA, the more closely related they are Evidence for Evolution - Protein Comparison

All living things have DNA and make mostly the same proteins made from the same amino acids Unique proteins in specialized cells can be compared across species

Evidence for Evolution - Protein Comparison Proteins of lightsensitive cells in the brain of this ancient marine worm are very similar to the cells in the

vertebrate eye Shows common ancestry

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