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Transcript of Natural Selection
4.2.1 - The Work of Lamarck & Wallace
4.2.2 Developing the Theory of Evolution by Natural Selection
George-Louis Leclerc, Comte de Buffon (1706 - 1788
Buffon is a French Naturalist who challenged the belief that life was unchanging. In his book Histoire Naturelle, his book on the natural world, he noted the similarities between humans and apes, and speculated that they might have a common ancestor. He also said the Earth was older than 6000yrs. old, which was a common belief at the time.
4.3.2 Finches of the Galápagos Islands:
4.3.1 Biological Barriers
Two distinct species of ant live in the same national park. Little is known about their natural history, but they have been observed working during the day and resting at night in similar habitats. These species look different, and scientists have discovered that they produce different pheromones.
In this scenario there are prezygotic barriers. Behavioural isolation would be the leading mechanism that prevents the fusion of the egg and the sperm so that no zygote can form. The differences in pheromones between the two species would be a leading challenge for the two species interbreeding. The definition of pheromones is “naturally occurring odorless substances the fertile body excretes externally, conveying an airborne signal that provides information to, and triggers responses from, the opposite sex of the same species”. If the two species have pheromones that do not attract each other, than there are behavioral differences that are biological barriers.
Bats in the genus Myotis look identical and have always been classified as one species, even though behavioral differences have been observed. Recently, scientists using molecular biology techniques have discovered that there are many different and genetically distinct species within the genus. In one case, two genetically distinct species of Myotis were found sharing the same roots over a period of years.
In this scenario there are prezygotic barriers. These two species of bats also experience behavioural isolation that are biological barriers of the two slightly different species of bats. Because these barriers come up before zygotes form, it is considered prezygotic barriers.
Several species of frogs of the genus Rana can live in the same pond. Sometimes hybrid zygotes form, but these fail to develop.
This scenario is an example of postzygotic barriers. Reduced hybrid viability is the leading barrier in this example. Reduced hybrid viability is the genetic incompatibility between the two species that may abort the development of the embryo at an early stage. Specific to this example, sometimes hybrid zygotes form from the separate species of frogs, making it postzygotic. And due to the fact they fail to develop, these species experience reduced hybrid viability barriers.
. What is the role of the environment in the passage written by Lamarck?
The role of the environment has an effect on the shape and organization of animals, and when the environment changes, organisms re-shape and organize correspondingly. A new environment can new habits to some animals, which can lead to new habits. Then, only part of the environment will be used, and in some cases, part of the environment will no longer be necessary.
2. What is the role of the environment in the passage written by Wallace?
The role of the environment affects the typical form of species, some definite effects, however slight. many thing can affect a species and can change the appearance, habitat, power, external organs, and procuring food. The population does change over time as Wallace believes and may affect the population of some species and how the traits of the species change over time.
3. Based on the passage presented here, do you consider Lamarck’s observations to be scientific? Explain your answer.
Based on Lamarck’s observations I do believe that they are scientific many things do affect the environment and the species among it. Lamarck’s observations and conclusion about the environment and how it affects the shape and organisms of animals is scientific because you need to watch the behavior and affects the environment has on species and organisms. Also how Lamarck believed that the offspring can inherit the traits that their parents portrayed, I personally do believe that this is scientific and is based on DNA and genes.
George Cuvier (1969-1832)
Cuvier was a French Naturalist who was largely credited in developing paleontology. (Paleontology is the study of ancient life through the examination of fossils). Curvier studied each stratum (layer of rock) and noted the unique differences of characteristics of the species. He also realized that the deeper (older) you go, the more dissimilar the species are to modern species. In looking from stratum to stratum, he noted that some species appeared while others disappeared over time. This lead to the realization that species could go extinct. To prove his work, he proposed that Earth had gone through many natural disasters, such as floods and volcanic activity. disappeared over time. This lead to the realization that species could go extinct. To prove his work, he proposed that Earth had gone through many natural disasters, such as floods and volcanic activity.
4.2.3 - Answering Darwin's Questions:
Darwin used the answers to questions based on his observations to formulate his theory of natural selection? What were the two main ideas expressed in his publication
On the Origin of Species
His two main ideas were:
1. Present forms of life have arisen by descent and modification from an ancestral species.
2. The mechanism for modification is natural selection working for long periods of time.
4.2.5 Geological Time Scale:
Alfred Russel Wallace (1823-1913)
Wallace, a British Naturalist believed that species changed over time, but was unclear how populations changed. To understand this, he took a key point from Thomas Malthus’s essay called, “the Essay on the Principles of a Population.” This key point suggested that organisms reproduce more offspring than the environment could support, and eventually these numbers were reduced by disease and starvation. With this, Darwin theorized that individuals with certain trait (behavioral, physical, etc.) that helped them survive were more likely more to be passed onto their offspring. He reasoned that competition between species would select for individuals with certain characteristics, and against others, which increased the chances of survival and reproduction.
This geological time scale shows when organisms first appear in the fossil record
4.2.6 Homologous Vs. Analogous Structures:
Charles Darwin, a British naturalist, believed that species changed over time, but was unclear how populations changed. Darwin sailed around on a boat for 2 years, collecting information and observations for his work. To understand this, he took a key point from Thomas Malthus’s essay called, “the Essay on the Principles of a Population.” This key point suggested that organisms reproduce more offspring than the environment could support, and eventually these numbers were reduced by disease and starvation. With this, Darwin theorized that individuals with certain trait (behavioral, physical, etc.) that helped them survive were more likely more to be passed onto their offspring. He reasoned that competition between species would select for individuals with certain characteristics, and against others, which increased the chances of survival and reproduction. Darwin called this Natural selection. Two main points outlined in his book, “On the Origin of Species by the Means of Natural Selection” are:
Present forms of life have arise by descent and modification from ancient species
The mechanism for modification is natural selection over a period of time
Darwin proposed that life comes from the unknown, but over time, species change their characteristics and adaptation which helps them survive and reproduce.
1. Use Different colors or shading to identify the bones that have common structural arrangement in the fiver vertebrates.
are those that have similar structural elements and origin but may have a different function. The limbs shown below have similar structures such as number of bones, muscles, ligaments, tendons and blood vessels. These structural elements are arranged to be best suited for different functions; walking, flying, swimming, etc.
Charles Lyell (1797-1875)
Charles Lyell was a Scottish geologist who rejected the ideas of revolution. He proposed that geological process operate at the same rate in the past as they do today. he reasoned that if geological process were slow and continuous, not catastrophic, than Earth might be older than 6000 yrs. old. He theorized that slow subtle changes that happen over a long period of time could result in substantial changes.
Jean-Baptiste Lamarck (1744-1829)
French Naturalist Jean-Baptiste Lamarck wrote a book, philosophie zoologique, which outlined his ideas about species changing over time. He compared fossils of species over time (bottom to top) and come up with a “decent line.” He believed that species evolved until they reach a level of complex perfection. With this, he came up the inheritance of acquired characters. This means that the characteristics that an organism acquires in its lifetime (ie. muscles) could be passed off to its offspring. Lamarck hypothesized that characteristic could be passed from one generation to the next. Most importantly, he noted that an organism's adaptation to its environment could be passed on to its offspring.
process whereby the characteristics of a population of organisms changes over time because individuals with certain heritable traits survive specific local environmental conditions and, through reproduction, pass on their traits to their offspring
4.2.10 Summarizing Evidence for the Theory of Evolution:
Hypothesized evolutionary relationships for finches from the Galapagos Islands. The ancestral population initially gave rise to four lineages of finches. As time passed, different lineages began to become geographically and reproductively isolated from each other. For example, the birds that are now called the warbler finches developed beaks that were more slender than the beaks of their ancestor to specialize in eating insects.
Suppose that there is a shipwreck, and two populations of the same species of rabbits arrive on two different islands in the ocean. The following scenarios illustrate how the two populations could be affected by their isolation.
One Island has predators that eat rabbits and the other does not. How might natural selection change the two rabbit population after several generations?
On Island one, where no predators are present, the rabbits would thrive in numbers and would overpopulate the island, eventually becoming an extremely invasive species. However the island with predators would force the numbers of the rabbits to regulate at a constant level of reproduction and being consumed, but initially the rabbits would either have to learn to adapt to the predators and speciation could take place in order to help the rabbit population survive and adapt accordingly, and if they do not adapt they will be eradicated by their predators.
The food available to the rabbits is different on one island than it is on the other. How might natural selection change the two rabbit population with regard to their food requirement after several generations?
As the rabbits on both islands learn to survive and adapt to their new habitats, the generations after them are majorly affected through natural selection. They would change their eating habits and learn what foods are poisonous and which to stay away from. As well there overall behavior could change and as the years pass each adaptation and survival technique is linked through natural selection to the future generations of rabbits. Since each island has different food availability both rabbit populations would need to create new techniques in order to obtain their food, and to help their population thrive.
Describe an alternate explanation for the process that Lamarck describes.
Lamarck shows observations saying how the environment affects the DNA and gen Lamarck shows observations saying how the environment affects the DNA and genes on species and organisms, also Lamarck believed that the offspring can inherit the traits that their parents acquired.
5. Research Darwin’s on the origin species (1859). Read and summarize a small section of the text that supports Wallace’s viewpoint. Name the chapter and section that you read and include a relevant passage.Section 4.2 Page 124 and 126
Charles Darwin believed that species and organisms changed over time as did Alfred Russel Wallace. Both British naturalists were unclear on the idea of how populations changed over time. Both naturalists looked at some key points from Thomas Malthus’s essay called, “The Essay on the Principles of a Population” which suggested that organisms would reproduce more offspring than the environment could support, and would eventually the number of species and organisms in a habitat reduced by disease and starvation. Another similarity between the two naturalists is they both believe that the offspring could inherit traits their parents had acquired. (behavior, physical etc.)
Suppose that the climate of one island is hot, but the climate of the other is cold. How might the two rabbit populations become adapted to the different climates?
The rabbits inhabiting the colder island would have to adapt their physical attributes, such as the increase of thickness of their fur, over generations to ensure the survival of their population. The animals on the cooler island would also need to create warm shelter for themselves, for example in deeper burrows, and also adapt to hibernation during harsh weather and winters. The rabbits on the warmer island would also need to adapt their physical attributes, but reduce the thickness of their fur, in order to ensure the population of rabbits over generations to stay cool and their body temperature constant. The rabbits living on the warmer island would also need to adapt their shelter patterns, for example shaded cool burrows, and would need to know the best ways to access water.
If, after several generations, individuals from the two populations were transported to the same habitat, do you think they could mate and produce viable offspring? Why or Why not?
I do not believe that after several generations these two individuals from different populations would be able to reproduce. This is for starters because their mating habits would have evolved over time in order to adapt to their surroundings and both individuals would not know the others mating habits. As well the two rabbits would aesthetically look different to each other, and if each rabbit didn’t recognize the other as the same species, then they may use survival techniques and try to harm one another. If the two individuals from different population did mate, I don’t think the offspring would survive due to the fact that is would be a mashup of both populations, and would have separate genetic makeup than either population of rabbits and wouldn't be able to survive in either habitat completely.
Teddy Graham Lab:
1. Describe what is happening to the genotype and allele frequencies in the population of Teddy Grahams?
With an initial base population of 10 bears as the population increases the recessive trait being the happy bears decrease in numbers, and the dominant trait is evident in the population due to predation. At the end of the lab the recessive trait was completely eradicated from the population and the dominant trait (sad bears) were left standing.
2. What would you expect to happen if you continued the selection process for additional generations?
If the selection process was experienced in additional generations than it can be expected that the additional generations would end up with more sad bears than happy bears, because when we select bears to eat we pick the sweeter tasting ones, which are the happy bears, and eating a recessive trait makes it more rare in a population.
3. How would the frequencies change if you were to now select for the sad bears?
The ratios of the allele frequencies would reverse, for example in F2 the ratio is 4:10, four happy bears to ten sad bears, but if we were selecting for sad bears the ratio would be 10:4. We were initially selecting for the recessive trait so the ratio was smaller, but in reverse we would be selecting for the dominant trait and the ratio would become larger larger.
4. Why doesn’t the recessive allele disappear from the population? How is it protected?
The recessive allele does not disappear from the population because there is always the chance of the recessive allele. The dominant allele can remain in a population in a heterozygous form where the dominant form would mask the recessive. Sometimes the heterozygous form of the trait provides some protection. (i.e. Sickle cell anemia.)
In the Natural Selection Teddy Graham Lab through recorded data we observed the relationship between dominant and recessive traits, and the process of natural selection was explored. In both selections we followed directions according to the procedure. We ensured that the correct amount of bears were removed and also that the math was correct before proceeding onto the next part of the procedure. The past discussed steps were what we had done right in the lab. In selection two,the population was faced with the problem of eradication involving the happy bears. The steps outlined by the procedure for part two of the lab resulted in the remaining amount of teddy bears from the dominant trait carriers (sad bears) to continue while the recessive trait carriers(happy bears) numbers quickly dissipated in the population. For the first selection we did not have this problem, but as half the bag of teddy grahams was gone there was fewer traits (happy and sad bears) to randomly select. This lab was a helpful representation that showed how dominant and recessive traits are represented in a “real life” situation, or in a simulated population experiment.
Alfred Russel Wallace (1823 - 1913)
Wallace, a British Naturalist, believed that species changed over time, but was unclear how populations changed. To understand this, he took a key point from Thomas Malthus’s essay called, “the Essay on the Principles of a Population.” This key point suggested that organisms reproduce more offspring than the environment could support, and eventually these numbers were reduced by disease and starvation. With this, Darwin theorized that individuals with certain trait (behavioural, physical, etc.) that helped them survive were more likely more to be passed onto their offspring. He reasoned that competition between species would select for individuals with certain characteristics, and against others, which increased the chances of survival and reproduction.
change in allele frequencies due to chance events in small breeding population
1. Color or shade structures that have a similar function in each organism
in organisms are body parts in different species that have a similar function, but have evolved separately. The organism above have no common evolutionary origin, but have body parts that perform similar functions to each other.
4.2.1 - Contd.
Three type of natural selection:
: the extremes are selected against
One extreme value is selected for
the extremes are both selected for
is a model of evolution which theorizes that most speciation is slow, uniform and gradual.
Allopatric speciation (geographic speciation):
is speciation that occurs when biological populations of the same species becomes isolated from each other to an extent that prevents or interferes with genetic interchange.
: model that suggests that evolutionary history consists of long periods of stasis (stable equilibrium), punctuated by periods of divergence
competition for limited resources among members of different species
competition between members of the same population for a limited resource
subtle changes over time that can be observed
substantial changes over time
4.2.3 - Answering Darwin's Questions:
Science 20 textbook: Inquire into Biology
Justin, Nick, Darcey, Carly & Brydie