tjBCNetwork! Peter Kim Chapter 22 Descent with Modification w/ explanation of Transformation Lab Overview: We all know about Charles Darwin and his controversial work On the Origin of Species, but many other scientists before postulated theories about how different species of animals and plants came into being. Darwin was also influenced by the works of others such as Jean-Baptiste Lamarck. Darwin introduced terms such as natural selection, evolutionary adaptation, and descent with modification. • • • • • • • • Evolution - defined as a change over time in the genetic composition of a population Remember that it is a population, or in some cases a species. Individuals never evolve. This is where biology starts to overlap more with the humanities rather than the sciences. Darwin’s “radical” views at the time directly challenged the church and its beliefs in creation, or that each species had been made by a god. This creationist belief was espoused by the first of our scientists, a guy named Carolus Linnaeus. He was a Swedish physician and botanist who developed a system for classifying species, and he founded the branch of biology known as taxonomy. He also devised the binomial naming system (Ex. Drosophila melanogaster or the common fruit fly) Darwin used the Linnaeus system, but turned it into a tool for explaining a concept. What was ironic was that Linnaeus developed this classification system to “glorify god.” Certain rocks such as limestone or sandstone are known to be banded, or composed of different “layers”. These layers are called strata (singular stratum). These are important tjBCNetwork! Peter Kim because within these layers are fossils, remains or traces of organisms from the past. • • • • • • • • These fossils are older and older in successively deeper layers within the rock. Seismic activity or erosion can cause older layers to be seen and reveal fossils, like dinosaur bones or arrowheads. Paleontology, or the study of fossils, was developed by George Cuvier, a French scientist, who observed in sedimentary rock that from one stratum to the next, some species disappear, and other new species appear. He inferred that extinctions are part of life. He didn’t agree with the gradual evolutionary view, so he put forth the idea of catastrophism, that the strata were separated by catastrophes like floods, droughts, or wildfires. Another theory at the time was that of gradualism, that change can take place over continuous but slow changes that accumulate. This idea was put forth by Scottish geologist James Hutton. A key idea here is that his theory could be explained by current gradual mechanisms. Charles Lyell, the leading geologist in the era when Darwin was around, took gradualism and put it in a broader theory, that of uniformitarianism. Lyell that those same gradual changes that happened in the past happened at the same rate as the processes today. One of the few people who put forth an idea of how life evolves, French biologist Jean- Baptiste Lamarck had two principles. tjBCNetwork! • • • • • • • • • • • • • • Peter Kim The first, on use and disuse, stated that anything that was not essential to the organism’s survival (e.g. was not used), it would be lost in the organism’s evolution. The second, inheritance of acquired characteristics, stated that any modifications that occurred over an organism’s lifetime could be inherited by its offspring. Lamarck also thought that organism’s had an innate drive to become more complex. Darwin disagreed in favoring his idea of natural selection, but he also believed in the misconception of inheritance of acquired characteristics. Remember, acquired characteristics can NOT be passed on. Think about it, if that was true, and you somehow learned to walk the entire time on your hands, your offspring would also walk on their hands from birth. We begin with Charles Darwin, here’s the laydown. Born in Shrewsbury, England Always fascinated with nature as a boy His father sent him to the University of Edinburgh to study medicine. Darwin could not stand to see surgery being done and was always nauseous, especially since there was no general anesthesia back then So he decided to attend Cambridge University to become a clergyman. While studying under Reverend John Henslow, a botany professor, he recieved his B.A. Henslow recommended Darwin to Robert FitzRoy, who was preparing a journey around the world on the HMS Beagle Darwin spent much time collecting animal samples and studying the various flora and fauna of South America, because the ship’s job was to plot the coastline An important observation he made was that animals and plants in certain climates in South America more closely tjBCNetwork! • • • • • • • • • • • • • • • • Peter Kim resembled other animals in different climates in South America than areas with the same climate in places like Europe While on board the ship, Darwin read Charles Lyell’s Principles of Geology, of which he found examples and samples that reinforced those views Finally the most influential stop Darwin made was at the Galapagos Islands The observations he made about the animals there being found nowhere else served as an example for his theory While on this trip, Darwin corresponded with many other scientists such as Lyell and Henslow By 1844, Darwin finished writing his essay on the origin of species and natural selection. However he did not want to publish it, since he knew it would cause an uproar Lyell, however, urged him to publish it before someone else came to the same conclusions This came true. In June 1858, Darwin received a manuscript from a British naturalist named Alfred Russel Wallace Darwin then sent the manuscript to Lyell, who presented it to the Linnean society, and finished his paper and published it a year later Wallace, however, was in such awe of Darwin that he agreed that Darwin was the main architect of the theory of natural selection Darwin called his view of life descent with modification, a term he used instead of evolution These are the main point: Observation: Population growth is exponential if unchecked Observation: Populations however remain stable Observation: Resources are limited Observation: Members of a population vary, no two individuals are alike (except twins) Observation: Much of this variation is heritable tjBCNetwork! • • • • • • • • • • Peter Kim Inference: Production of more individuals leads to competition for various resources, such as food and mates Inference: Survival depends on inherited traits. Those who inherit traits that allow them to better compete for resources leave more offspring Inference: This unequal ability leads to a gradual change in the genetic composition of a population Artificial selection - Taking plants or animals with desired traits and breeding them to create the desired individuals Example is wild mustard, when humans picked larger flowers and stems, larger flower clusters, larger terminal buds, larger lateral buds, larger leaves, or larger stems, they got from the mustard, broccoli, cauliflower, cabbage, brussel sprouts, kale, and kohlrabi respectively. This shows that humans can induce natural selection artificially to create new species for use. Another example is maize, or corn. In genetic terms this is a complete failure, as the cob is completely surrounded by the sheath and would rot if not harvested by humans. In other words, it completely depends upon humans. Natural selection is the differential success in reproduction among individuals that vary in their heritable traits. These reproductive differences emerge as each individual interacts with its environment Over time, natural selection can increase the adaptation of organisms to their environment If an environment changes over time, or if individuals of a particular species move to a new environment, natural selection may result in adaptation to these new conditions, or maybe it could give rise to new species Homology is the fact that all organisms have similar bones in the body, etc., an explanation for how we are all descended from the same ancestor tjBCNetwork! • • • • Peter Kim Vestigial organs are remnants of our previous evolution, such as out tailbone, a reminder that our ancestor had tails The final key terms are biogeography and endemic Biogeography describes the fact that certain similar species exist in similar ranges climates, and parts of the world Endemic refers to where a certain species is localized to.