Chapter 15 (Darwin and Evolution)

"Misconceptions" about evolution with their stupid replies (The first two are even debated. We all agree these are false. They made these up. Dumb)

1) Evolution is the theory about how life originated -Evolutionary biologists are concerned with how the diversity of lie emerged AFTER the origin of life. The origin is not the focus of their research (but may play a small part). 2) There are no transitional fossils -Biologists do not expect that all intermediates have been preserved in the fossil record. Many species will not be fossilized because soft tissue are rarely mineralize, death must occur somewhere that favors skeletal preservation, etc. Despite this, some transitional fossils have been found. 3) Evolution proposes that life changed as a result of random events; clearly, traits are too complex to have originated "by chance" -"Chance" does not play a role in evolution. Mutations that create new variation in population occur randomly. But, the natural selection process that shapes that variation is not random. It can only act on an existing variation and is thus constrained by changes that occurred in the past. Complexity is the result of millions of years of modifications to preexisting traits. 4) Evolution is not observable or testable; thus, it is not science. -Evolution is both observable and testable. Studies have shown traits that change in response to environmental changes. Evolution has over 150 years of supporting evidence from a variety of scientific disciplines.

Natural selection concept: Organisms become adapted

Adaptations are especially noticeable when unrelated organisms living in a particular environment have similar characteristics (eg, different animals have flippers for swimming). Differential reproduction generation after generation can cause adaptive traits to increase in frequency in each succeeding generation. Natural selection is the only evolutionary process that results in adaptation to the environment.

Evidence for evolution: Biochemical evidence

All living organisms use the same biomolecules, including DNA, RNA, and ATP. Thus, these molecules were present in the first living cell or cells from which all life originated. Based on the codes of codons, scientists show that humans have genes in common with simpler organisms. Also, the amino acid sequence is similar across the tree of life. Amino acid sequences of humans and other animals differ in only a few (or just one) amino acids.

What are vestigial structures?

Anatomical structures that apparently functioned in an ancestor but have since lost most or all of their function in a descendant.

Define adaptation

Any evolved trait that helps an organism be more suited to its environment.

Who founded the science of paleontology? Who was he?

Baron Georges Cuvier (zoologist). Staunch advocate of fixity of species and special creation. His studies revealed that fossil varieties appeared suddenly in different strata within a geographic region. He said this was due to a series of local catastrophes or mass extinctions, followed by repopulation by surrounding species. Some of Cuvier's followers say there were worldwide catastrophes and God created new species to repopulate the world. This is known as catastrophism.

Natural Selection and adaptation (Darwin)

Darwin and Alfred Russel Wallace presented the idea of natural selection in 1858 to the Linnean Society. of London. Natural selection is a process based on... -Organisms exhibit variation that can be passed down from one generation to the next--that is, they have heritable variation. -Organisms compete for available resources. -Individuals within a population differ in terms of their reproductive success. Organisms become adapted to conditions as the environment changes.

Darwin's biogeography observations

Darwin explored the northern hemisphere and compared animals of South America to those with which he was familiar. He noticed that similar environments had similar-looking animals. eg, he found Patagonian cavys in the grasslands of South America instead of rabbits from Europe. He thought they were similar because they adapted to the same type of environment. Eventually, Darwin noted that similar species replaced one another. eg, greater rhea in north replaced by lesser rhea in south. Thus, Darwin said related species could be modified by environmental differences. He found this to be true through his exploration of the Galapagos islands.

Evidence for evolution: Biogeographical evidence

Darwin noted that different animals are found in different parts geographically. eg, rabbits are not in South America (instead, Patagonian cavys are) because they evolved somewhere else and had no means of reaching South America. Further, the species of finches found on the Galapagos islands were note found on the mainland. Darwin says that an ancestral population of finches from the mainland reached the islands and over time evolved into different species found on each isolated island. In the history of earth, the book says South America, Antarctica, and Australia were originally connected. Marsupials have evolved from egg-laying mammalian ancestors. Today, marsupials are endemic to South America and Australia. Australia once separated from the other landmasses and the marsupials diversified into various forms suited to the environments. Biogeographical differences provide evidence that variability in a single, ancestral population can lead to adaptation to different environments through the forces of natural selection. Competition for resources also provides some pressure which leads to diversification.

Darwin's findings on the Galapagos islands

Darwin noticed that the animals on the islands were slightly different from the mainland and even varied from island to island. eg, each island had a different type of tortoise (long vs short necks), which he said was because of the difference in vegetation among islands. Another major find was the finches. Darwin had Gould identify them. Gould said they were "a series of ground finches... and entirely new group." There were big differences in beak size. He wondered if these different species of finches could have descended from a mainland finch species. He thought they came from South America and new species of finches arose because of the geographic distance of the islands isolated populations long enough for them to evolve independently. In the end, Darwin believed these animals came from the mainland and adapted to the various island environments.

Natural selection concept: Heritable variation

Darwin said variation is required for the process of natural selection to operate. He suspected a mechanism of inheritance but he didn't know it was genes at the time. Random mutations have been known to be the source of new genetic variation within a population. Genetic variation can be harmful, neutral (no effect), or helpful to survive and reproduce. Harmful variation is eliminated from a population because individuals with the mutations do not survive or reproduce. Natural selection ignores neutral variation, but it can still survive in population. Helpful variation will increase reproductive success. Natural selection acts on heritable variation already present within a population's gene pool, and the selection process is random (i.e. no goal of "improvement").

Evidence for evolution: anatomical evidence

Darwin showed how descent from a common ancestor was able to explain anatomical similarities among organisms. Vertebrate forelimbs are used for different things, but they all have the same sets of bones organized in similar ways. The best explanation to Darwin was that the common ancestor had the same basic forelimb body plan. This plan was then modified independently in all descendants. Vestigial structures occur because organisms inherit their anatomy from their ancestors, so their anatomy carries traces of their evolutionary history. At some point in development, all vertebrates have a postanal tail and exhibit paired pharyngeal pouches supported by cartilaginous arches. Later, these serve different functions.

Evidence for evolution: Fossil succession

Fossils are remains or traces of past life. They include trails, footprints, burrows, worm casts, etc. Transitional fossils bear a resemblance to two groups that in the present are classified separately. They represent intermediate forms of life in transition from one form to the other. In 2004, scientists discovered fossilized remains of Tiktaalik roseae ("fishpod"). It is said to be the transitional form between fish and four-legged animals, the tetrapods. Other transitional fossils include archaeopteryx, sinornis, confuciusornis, iberomesornis, ambulocetus natans, pakicetus, and rodhocetus.

What were Charles Lyell's contributions to science?

He made Hutton's theory popular. He proposed the theory of uniformitarianism, which states that the natural processes witnessed today are the same processes that occurred in the past. This is based on Hutton's view that extreme geologic changes can be explained by slow, natural processes, given enough time. Lyell and Darwin thus believed that the earth must be very old.

Darwin's observations of change over time

He observed marine shells high in the Andes Mountains, which made him think the earth was very old. From this, he thought there would have been enough time for descent with modification to occur. Thus, living forms could be descended from extinct forms known only from the fossil record. So, species are not fixed; they change over time.

How did Thomas Malthus influence Darwin?

He proposed that the size of human populations is limited only by the quantity of resources, such as food, water, and shelter, available to support it. He said famine, war, etc. were the result of populations overstretching their resources. Darwin applied this to animal populations--animals tend to reproduce more than can survive, and competition for limited resources in the environment is the element that determines survival. Thus, Darwin used Malthus' principle to formulate natural selection.

What were James Hutton's contributions to science?

He proposed the theory of slow, uniform geological change. He said the earth is subject to slow but continuous cycles of rock formation and erosion, not shaped by sudden catastrophes. He said erosion makes dirt, which is washed into rivers and carried by oceans and converted into sedimentary rock. This often contains fossils and is later uplifted from below sea level to form land during geological upheavals.

How was Jean-Baptiste de Lamarck and why was he important?

He was the first biologist to offer a testable hypothesis that explained how evolution occurs via adaptation to the environment. In contrast to Cuvier's view, Lamarck observed the fossils in strata and said more complex organisms are descended from less complex organisms. He said (wrongly) that this is due to a natural motivating force--a striving for perfection--that is inherent in all living organisms. Lamarck proposed the idea of inheritance of acquired characteristics--that the environment can produce physical changes in an organism during its lifetime that are inheritable. His most famous example was the long neck of giraffes. Their necks grew longer as they stretched to reach higher food and they passed that on to the nest generation. This hypothesis has never been supported by experimentation.

What is Darwin famous for?

His theory of evolution by natural selection

Evolutionary evidence from developmental biology (PowerPoint)

Homeobox or Hox genes: •Orchestrate the development of the body plan of all animals •All animals share a Hox gene common ancestor. •The number and type of Hox genes vary among animal groups. •The variation in Hox genes is responsible for the wide range of body plans seen in animals. •Example: Changes in the timing and duration of expression of Hox genes controlling the number and type of vertebrae can produce the spinal column of a chicken or the longer spinal column of a snake. •Simple changes in gene control have profound effects on the phenotype.

Describe the beginning of Darwin's adventure of making up stupid theories

In December 1831, 22 year-old Darwin set sail on the HMS Beagle. He served as the ship's naturalist--to collect and record the geological and biological diversity he saw during the voyage. Before this, he believed in the fixity of species (species have remained unchanged since the time of creation). But, the voyage and his geological discoveries led him to forming the idea of that species arise and change.

Evidence for evolution: Developmental biology

It appears that life's vast diversity has come about by a set of regulatory genes that control the activity of other genes involved in development. eg, Hox (homeobox) genes orchestrate the development of the body plan in animals. All animals share a hox gene common ancestor, but the number and type of hox genes vary among animal groups. This variation in hox gene is responsible for the wide range of body plans seen in animals.

Define extant

Organisms that are still in existence

Describe the ideas of Plato and Aristotle

Plato: Every species on Earth has a perfect, or "essential," form and species variation is imperfection of this essential form. Aristotle: Organisms vary in complexity and can be arranged based on their order of increasing complexity.

Natural selection concept: Organisms differ in reproductive success

Some organisms have favorable traits that enable them to compete for limited resources. Individuals with favorable traits acquire more resources and devote more time to reproduction. Darwin called the ability to have more offspring "differential reproductive success." The most fit individuals capture a larger amount of resources and convert them into a larger number of viable offspring. Fitness is influenced by different factors for different populations. eg, background matching helps an animal both capture prey and avoid being captured. Thus, it leads to survival and increased fitness. Natural selection occurs because certain members of a population have a variation that allows them to survive and reproduce to a greater extent than other members.

Natural selection concept: Organisms compete for resources

Stems from Malthus' idea of limited resources in human populations. Darwin said insufficient resources would be available to support a growing population. eg, take two elephants who make six elephants and the rates continue. Population of elephants would be millions after a few hundred years. No environment has enough resources to sustain that. This overproduction potential of a species is often referred to as the geometric ratio of increase.

Define homologous (in terms of anatomical structure)

Structures that are anatomically similar because they are inherited from a common ancestor. These (not analogous structures) are evidence for common ancestry.

Define analogous

Structures that serve the same function but originated independently in different groups of organisms that do not share a common ancestor. eg, wings of birds and insects are analogous.

Define evolution

The process that proposes that genetic change occurs in a species over time, which leads to their genetic and phenotypic differences. This process is due to natural forces.

Define fitness

The reproductive success of an individual relative to the other members of the population.

Define artificial selection

The type of human-controlled breeding to increase the frequency of desired traits. This is only possible because the original population exhibits a variety of traits.

Define biogeography

study of the distribution of organisms around the world

Artificial selection (PowerPoint)

•A breeder chooses which traits to perpetuate and selects the plants and animals that will reproduce. All dogs are descended from the gray wolf. •They began to be domesticated between 18,800 and 32,000 years ago. •The process of diversification led to extreme phenotypic differences. •The wolves under domestication were separated from other wolves. •Each human tribe selected for whatever traits appealed to them.

Evidence for Evolution: Biochemical evidence (PowerPoint)

•All living organisms: •Use the same basic biochemical molecules •Utilize same DNA triplet code •Utilize same 20 amino acids in their proteins •DNA base-sequence differences: •When very similar, suggest recent common descent When more different, suggest more ancient common descent

Evidence for evolution: Biogeography (PowerPoint)

•Biogeography is the study of the range and distribution of plants and animals throughout the world. •Biogeographical distributions are consistent with the hypothesis that related forms of life evolved in one locale and then spread to accessible regions. •A different mix of plants and animals would be expected whenever geography separates continents, islands, seas, etc. •Marsupials (mammals in which females have an external body pouch where there young complete development) evolved from egg-laying mammal ancestors. •Today they are endemic to South America and Australia. •When Australia separated and drifted away from other landmasses, the marsupials diversified into many different forms.

Evidence for evolution: Fossils (PowerPoint)

•Fossils are the remains and traces of past life. Traces include trails, footprints, or preserved droppings. •Fossils record the history of life from the past. •They document a succession of life forms from the simple to the more complex. •Sometimes the fossil record is complete enough to show descent from an ancestor. Transitional fossils are a common ancestor for two different groups of organisms. •They allow us to trace the descent of organisms.

Misconceptions of evolution (PowerPoint)

•It is a theory about how life originated. -Evolutionists are concerned with how the diversity of life emerged following its origins. •There are no transitional fossils. -Biologists don't expect all transitional fossils to have been preserved, but have unearthed many transitional fossils. •Evolution proposes that life changed due to random events. -Chance is only part of the story; mutation occurs randomly but natural selection isn't random. •Evolution is not observable or testable. It is not science. -Evolution is both observable and testable.

Natural selection and adaptation (PowerPoint)

•Members of a population have heritable variations. •More individuals are produced in each generation than the environment can support. •Organisms compete for available resources. •Some individuals have adaptive characteristics. •Favorable traits that result in increased survival and reproduction which causes organisms within a population to differ in their reproductive success. •Natural selection can result in a population adapted to conditions in the local environment as the environment changes. •An increasing proportion of succeeding generations will have favorable characteristics. Fitness is the relative reproductive success of an individual. •The most-fit individuals in a population capture a disproportionate share of resources. •Interactions with the environment determine which individuals reproduce the most. •Example: Among western diamondback rattlesnakes (Crotalus atrox) living in a dark environment, the most fit are black; but among those living in a light environment, the most fit are light. Background matching helps an animal avoid being captured Adaptation: •Change that helps a species become more suited to its environment •Product of natural selection

Nature of Science reading: The tree of life project (PowerPoint)

•The Tree of Life Project is a collaborative effort to determine how all of life is related and descended from a common ancestor. •It contains hundreds of species from all domains of life and is growing. •It provides support for Darwin's theory of evolution by natural selection.

Darwin's theory of evolution: Galapagos finds (PowerPoint)

•Tortoises •Darwin observed that tortoise neck length varied from island to island. •He proposed that speciation on islands correlated with a difference in vegetation. •Finches •Darwin observed many different species of finches on various islands. •Significant variety in beaks •Ground-dwelling finches have beaks adapted to eating seeds and tree-dwelling finches have beaks sized according to their insect prey. •He speculated that they could have descended from a mainland finch species. Each of the 13 species of Galápagos finches has a beak adapted to a particular way of life. •A heavy beak is suited to a diet of large seeds. •The beak of the warbler-finch is suited to feeding on insects. •A longer, somewhat decurved beak and the split tongue of the cactus-finch are suited to probing a cactus for seeds.

Evidence for Evolution: Anatomy (PowerPoint)

•Vertebrate forelimbs: •Homologous structures - all contain the same sets of organized bones in similar ways. •Yet they are modified extensively to meet various adaptive needs. •Darwin interpreted this as support for a hypothesis of common descent. •Embryological development •All vertebrate embryos have: •A post-anal tail •Paired pharyngeal (throat) pouches supported by cartilaginous arches Homologous Structures: •Anatomically similar because they are inherited from a common ancestor •May be functionally similar or not Analogous Structures: •Serve the same function •Are not constructed similarly •Do not share a common ancestor Vestigial Structures: •Fully developed anatomical structures in one group of organisms •Reduced or obsolete function in similar groups