4_1 Darwin & Evolution

Who was Alfred Russell Wallace?

An English naturalist who independently & simultaneously proposed natural selection as a mechanism of evolution a year before Darwin. Unfortunately, Wallace was overshadowed by Darwin's work & findings.

What are some examples of vestigial structures?

Anatomical similar structures that are anatomically similar but are reduced in size and have no function in the organism of question. Whale hips; human tail.

In discussing evolution, what did Darwin mean by "descent with modification?"

As descent through generations occurs over time, so too does diversification. As time passes, species change. Said another way, Organisms currently living become vastly different from their ancestors.

Explain the significance of natural selection tenant "Organisms compete for resources?"

Based on the work of Thomas Malthus, Darwin reasoned that no environment could sustain the survival of all the members of a population.

Explain the significance of natural selection tenant "Organisms have inheritable variations of traits?"

Before Darwin, variations were viewed as imperfections that were not important descriptors of species. Darwin emphasized that variations were not imperfections, they could be helpful or harmful, were completely random & essential to natural selection. He felt they were essential because natural selection can only operate on variations that were already available in the population's genetic pool.

catastrophism:

Cuvier's theory that natural disasters wipe out life-forms and living organisms[in surrounding areas] migrate to fill the voided areas. He believed the reason new fossils were discovered in certain area were the result of these mass extinction& migration event and not due to the natural "succession of life."

What observations did Darwin make in regards to Galapagos island finches?

Darwin almost overlooked finches because he initially thought they resembled the main land [South American] finches. However through further inspection, he realized that finches varied by nesting site, beak size, & eating habits. For example, Darwin found finches with long pointed beaks in areas where the food was on thorn vegetation. If their beaks were not long enough, the thorns could pluck out there eyes when attempting to feed. He found large ground-dwelling finches with large beaks which were necessary to eat the large seeds.

Darwin's theory of evolution

Darwin theory of evolution is called "descent with modification." Darwin explained that organisms are related through common descent & that adaptation to different environments results in their diversity. He believed that new species arise by gradual changes that develop over time [instead of being the instant work of a creator] & proposed natural selection as the mechanism for evolutionary change. [According to the AP BIO teacher, Darwin's theory is that different species have common ancestors but each species is different from each other because it has had its traits modified to increase biological fitness to their environment.] Darwin developed his theory during his travels on the HMS Beagle noting the similarities and differences in animals in South America, the Galapagos islands, & his native land.

natural selection

Darwin's [& little known Alfred Russell Wallace] proposed mechanism of evolution that states organisms that are most biologically fit for an area will always be found in that area. Organisms that are not fit in an area will not survive. Said another way, As random genetic mutations(multiple alleles) occur in an organisms genetic code, the beneficial mutations that help that organism survive or thrive are passed on to the next generation. Overtime, these beneficial mutations or traits accumulate resulting in a different species.

What observations did Darwin make in regards to Galapagos island tortoises?

Each island seemed to have its own type of tortoise. He noticed long-necked tortoises were found in dry areas where supplies of ground vegetation were scarce. He found short-necked tortoises in regions with relatively abundant amounts of ground vegetation.

Give some examples of artificial selection...

Early humans selected specific wolves for desired trait[possibly the trait of being less wild & more controllable] and allowed these wolves to breed. After generations of selective breeding, these desired traits increased in frequency resulting in domestic dogs. In another example Russian scientist produced silver foxes that allow themselves to be petted rather than running away from humans. They did this by selecting the most docile animals to reproduce.

Discuss the informal findings of Charles Darwin's grandfather, Erasmus Darwin

Erasmus Darwin suggested the possibility of common descent based on the presence of vestigial structures. Unfortunately he offered no conclusive mechanism by which evolutionary descent could happen.

What happens during erosion & uplift?

Erosion is the act where earth is worn away by water, ice, or wind and re-deposited at some other location on earth. The loose earth[consisting of soil &/or rock] gets packed into thick layers and becomes sedimentary rock. Uplift happens when sedimentary rock is uplifted from below seal level forming land.

Why is fossil evidence the best evidence for evolution? Of what significance is it that fossils can be dated?

Fossil evidence provides tangible concrete proof that verifies the postulated theories.

What's the difference between homologous structures and analogous structures?

Homologous structures come have similar anatomical (meaning bone and or musclulature) but possible different function. Analogous structures have dissimilar anatomical features but have similar functions.

What confirms evolution?

Homology not analogy.

What is the difference between artificial & natural selection?

In natural selection the environment[& not humans] provide the selective force. The numerically predominant species is not pre-determined, it is determined by the variations which allow the organisms to survive. In artificial selection, humans select which organisms reproduce in order to acquire offspring with the desired trait(s).

uniformitarianism

John Hutton's theory that the earth was subject to slow but continuous geological processes [of erosion & uplifting]that occur at a uniform rate. Hutton's theory is in direct contrast to the catastrophism theory & was influencial to the ideas of Wallace & Darwin.

What were Jean-Babtiste de Lamarck's contribution to evolutionary thought?

Lamarck was the first to identify a mechanism for descent with modification. He believed in the theory of "inheritance of acquired characteristics" and that modification was caused by adaption to an environment. Lamarck correctly concluded that more complex organisms descend from less complex ones. However, he mistakenly believed that this increasing complexity was the result of a "desire for perfection" which be believed was inherent to all living things. •

inheritance of acquired characteristics

Lamarck's belief that organisms adapted to their environment during their lifetime and passed on these adaptations to the next generation. He used the giraffe as an example. Lamarck believed that giraffes started out as horses and when the food supply of grass dwindled began eating leaves in trees. In one generation, he believed giraffes would stretch their necks to reach these leaves and this stretching of the neck "characteristic" would be passed from generation to generation.

What were Carlos Linnaeus' beliefs & contributions to taxonomy?

Linnaeus believed [like most pre-Darwinian philosophers] in special creation, fixity of species & scala naturae. He devoted his life to determining the ideal characteristics of each species so that he could rank species by increasing complexity as described in "scala naturae." Linnaeus contributions to taxonomy are as follows: [1] He developed the binomial system of nomenclature(a version is still used today); [2] Linnaeus also created a system for classifying plants;

What examples of natural selection are being witnessed today in the Galapagos' islands?

Peter & Rosemary Grant are observing beak size changes with rainfall. During wet seasons, the offspring have smaller beaks while during drier seasons offspring have larger beaks.

Give two examples of natural selection?

The beak length of the scarlet honeycreeper was reduced when the bird switched to its favorite source of nectar, labelloids, disappeared. Another common example of natural selection is industrial melanism. Prior to the industrial revolution, light colored moths were more common (90%) than dark colored moths (10%). With the advent of industry & increase in pollution, the number of dark colored moths exceeded 70%. After legislation to reduce pollution, the percentage of dark colored moths reduced to 16%.

What anatomical evidence support the common descent hypothesis? How do we know that evolution has actually happened?

The existence of homologous & vestigial structures provide evidence in support of the common descent hypothesis. In different organisms, the vertebrate forelimbs are used for flight (birds and bats), swimming (whales and seals), running (horses), & climbing (arboreal lizards). Despite their dissimilar functions, the vertebrate forelimbs of each organism contain the same sets of bones & are organized in similar ways. The most plausible explanation for this unity is that these organisms evolved from a common ancestor. These homologous structures provide proof for common descent...Vestigial structures are anatomical features that are fully developed in one group of organisms but are reduced and may have no function in similar groups. The presence of vestigial structures can be explained by the common descent hypothesis. Vestigial structures occur because organisms inherit their anatomy from their ancestors; they are traces of an organism's evolutionary history.

How do transitional fossils support the hypothesis of common descent? Give an example.

The identification of transitional fossils are a clear indicators that over time species have changed. As is the case of the intermediate between dinosaurs and birds, Archeopteryx, this transitional fossil supports the hypothesis. •

What was the "pre-Darwinian" world view?

The pre-Darwinian world view can be characterized by the following ideas: [1] the earth is young [2] each species is specially created & does not change over time. [3] any variations in species are imperfections from a perfectly-adapted version.

Give two examples of transitional fossils. [1] Archeopteryx: an intermediate between reptiles & birds; [2] Ambulocetus natans: a whale with legs

What is the biogeography hypothesis behind the idea of common descent is true? When forms are related, they evolved in one locale and then spread to accessible regions. Therefore, a different mix of plants and animals would be expected whenever geography separates continents, islands, seas, and so on.

What restrictions apply to natural selection?

[1] Because the environment is always changing, there is no perfectly-adapted organism. [2] Natural selection can only utilize variations that are randomly provided. Therefore, there is no directedness or anticipation of future needs; [3] Extinction occurs when previous adaptations are no longer suitable to a changed environment

What are the tenants for natural selection?

[1] In a species population, there are inheritable variations in traits; (ex green & brown colored beetles) [2] A population produces more offspring than the environment can support. Said another way, the environment does not support unlimited population growth. (Ex. beetles will be eaten by birds when spotted.) [3] Some individuals have favorable traits that enable them to survive and reproduce more often. (Ex. brown beetles are rarely spotted by predators while green beetles are spotted often. Brown beetles will reproduce more often) Darwin called this ability differential reproductive success.(we call it biological fitness) [4] Natural selection results in an increased proportion of individuals with the favored trait(s) in future generation. (ex. Future generations contain many more brown beetles than green).

transitional fossils

[1] any fossilized remains of a life form that exhibits traits common to both an ancesterol group & their derived descendant group [2](book definition) transitional fossils are common ancestor for two different groups of organisms; or they are closely related to the common ancestor for these two groups.

Discuss examples of the biogeography hypothesis of common descent.

[1]In the history of the Earth, South America, Antarctica, and Australia were originally connected. Marsupials (pouched mammals) evolved from their egg-laying mammalian ancestors during this time period. Today marsupials are found in both South America and Australia. When Australia separated and drifted away, the marsupials diversified into many different forms suited to the Australian environments. They were free to do so because there were few, if any, placental mammals with which to compete in Australia. In South America, where there are placental mammals, marsupials are not as diverse. [2]In another example, Darwin noted that South America lacked rabbits even though the environment was suitable for them. He concluded that rabbits evolved elsewhere and had no means of reaching South America. [3] Cacti & spurges are different species but are known to be related because both are succulent, spiny, flowering plants adapted for hot & dry environments. However you will only find Cacti in North America & spurges in Africa because they evolved on separate continents.

What were pre-Darwinian naturalist George Louis Leclerc's contributions to taxonomy?

[1]Leclerc wrote a 44-volume history of all known plants & animals. [2] He provided evidence [prior to Darwin] of descent with modification [or evolution]. Despite these findings, Leclerc still professed to believe in special creation & fixity of species. [3] He also speculated on the factors that cause descent with modification. He suggested that factors such as environment, migration, geographic isolation, and struggle for survival are what cause species to change over time.

What overall observations did Darwin make in regards to animals & plants (a) in South America? (b) the Galapagos Islands?

[a] As he sailed southward along the eastern coast of South America, he noticed that similar species replaced one another as one moves from city to city. [b]When he visited the Galapagos Islands, he found further evidence of his South American observation. He noticed that island species were different from the mainland [South American] species & were also different from island-to-island.

special creation

a pre-Darwinian belief that each species had an "ideal" structure, function & place in the "scala naturae"[sequential ladder of life];

What is scala naturae & the philosophy behind it?

a pre-Darwinian ranking system describing the complexity of life; The scala naturae is a "sequential ladder of life" where the simplest & most material beings are at the lowest rung of the ladder while more complex and spiritual were on the highest. In this view, humans occupied the highest rung.

adaptation

a trait that helps an organism be more suited to an environment; adaptations result from natural selection & are especially recognizable when unrelated organisms display similar characteristics; For example, manatees, penguins & sea turtles all have flippers which help them move through water.

adaptive radiation

an evolutionary process by which new species are formed from a common ancestor as a result of natural selection selecting for specific mutations(or allele).

vestigial structures

structures or organs believed to have been functional in an ancestor but are not functional &/or reduced in a descendant; Discuss George Cuvier's contributions to the history of evolutionary thought [1] Cuvier was a pre-Darwinian zoologist who used comparative anatomy to develop a system for classifying animals. [2] He founded the science of paleontology and used fossil bones to deduce the anatomy of animals; [3] Unfortunately, Cuvier was so blinded by his belief in fixity of species & special creation that he developed a theory (called catastrophism) which explained away fossil evidence showing the succession in life-forms;

biologically fit:

the ability to survive to reproductive age and reproduce. Ex. Butterflies have small mouth parts due to evolution. At one point butterflies could eat but because they are so brightly colored [in order to attract a mate] they also attracted predators which would prey on them before they could reproduce. Butterflies that stopping to eat would get eaten before they had a chance to reproduce. It became evolutionary superior to not waste time eating so in order to maximize their opportunity to reproduce. As a result, having small mouth parts made the butterfly biologically fit. Fitness can also be described as a measure of an organism's reproductive success relative to other members of an environment. Since organisms vary anatomically, physiologically & the challenges of a local environment vary what determines fitness also varies. Black western diamondbacks are more likely to survive on lava flows while lighter-colored rattlesnakes are more likely to survive on desert soil.

evolution [or law of evolution]:

the idea that species change over time. Generally speaking, evolution explains the unity & diversity of life. It first shows how living things share similar characteristics due to a common ancestry and then how species adapt to different environments to produce diversity.

fossils

the remains or traces of animals, plants, & organisms from past life. Fossils include skeletons, shells, seeds, insects trapped in amber & imprints of leaves.

taxonomy

the science of classifying organisms;

fixity of species

the set of beliefs derived from the ideas of Plato, Aristotle and Carolus Linnaeus which held that species have remained unchanged since their appearance on earth;