Biology Final Review > Chapter 22 - Evolution > Flashcards
Chapter 22 - Evolution Flashcards
bio
= life
geo
= the Earth
homo
= like, resembling
paleo
= ancient
taxo
= arrange
vestigi
= trace
Artificial selection
The selective breeding of domesticated plants and animals to encourage the occurrence of desirable traits.
Catastrophism
The hypothesis by Georges Cuvier that each boundary between strata corresponded in time to a catastrophe, such as a flood or drought, that had destroyed many of the species living there at that time.
Convergent evolution
A kind of evolution wherein organisms evolve structures that have similar (analogous) structures or functions in spite of their evolutionary ancestors being very dissimilar or unrelated.
Descent with modification
Darwin’s initial phrase for the general process of evolution.
Evolution
All the changes that have transformed life on Earth from its earliest beginnings to the diversity that characterizes it today.
Evolutionary adaptation
An accumulation of inherited characteristics that enhance organisms’ ability to survive and reproduce in specific environments.
Fossil
A preserved remnant or impression of an organism that lived in the past.
Gradualism
A view of Earth’s history that attributes profound change to the cumulative product of slow but continuous processes.
Homologous structures
Structures in different species that are similar because of common ancestry.
Homology
Similarity in characteristics resulting from a shared ancestry.
Natural selection
Differential success in the reproduction of different phenotypes resulting from the interaction of organisms with their environment.
Paleontology
The scientific study of fossils.
Taxonomy
A set of characteristics used to assess the similarities and differences between various species, leading to a classification scheme; the branch of biology concerned with naming and classifying the diverse forms of life.
Uniformitarianism
: Charles Lyell’s idea that geologic processes have not changed throughout Earth’s history.
Vestigial organ
A structure of marginal, if any, importance to an organism. Vestigial organs are historical remnants of structures that had important functions in ancestors.
3 major observations of life are
- Life forms share many common traits (unity)
- Life forms have many differences as well (diversity)
- Life forms are matched to their environments
The Theory of Evolution strives to
provide a biological mechanism to explain these 3 observations
Charles Darwin was a British naturalist
who presented what we now call evolutionary theory (he referred to it as “Descent with Modification”) in his groundbreaking book “The Origin of Species”
The main idea behind Darwin’s theory
is that organisms can vary in their inherited traits and not all variations are as likely as others to foster survival and therefore reproductive success
organisms that possess traits better adapted to the current environment will
survive over those that do not have those traits and will therefore pass the inherited traits on to their offspring
preferential survival of some traits over others is called natural selection
o Artificial selection occurs when humans selectively breed certain desirable traits with sometimes little regard to natural survival possibilities
Aristotle
Believed in a scala naturae or a fixed ladder of life on which organisms would not change their position (against evolution)
Linnaeus
Developed field of taxonomy or classification of all living organisms (against evolution because he believed in a divine placement of organisms in his classification system)
Cuvier
Paleontologist who believed in catastrophism in which sudden and dramatic changes in geology are responsible for the disappearance of previous species thus allowing for new species to move into areas (against evolution since didn’t take into account the slow, gradual changes which could allow for new speciation)
Hutton and Lyell
Geologists who suggested geological changes occur due to constant, slow processes and the same ones operating today have been for all of Earth’s time (uniformitarianism) (support evolution with same slow change idea and also made Darwin realize the Earth was older than previously believed which allowed for the time for the biological changes evolution required)
Lamarck
Biologist who erroneously suggested the mechanism for species changing over time was through the inheritance of acquired characteristics or use and disuse (against evolution in the sense the mechanisms he suggested were different from Darwin but supported idea that populations of organisms could change in their traits)
Wallace
Biologist who independently developed his own theory of evolution which matched Darwin’s (support evolution)
Mathus
Economist who studied the effects of overpopulation in humans and the inherent limitation of populations because of limited resources (supports evolution since it provides an explanation that only some organisms will survive if there is not enough resources for all organism, following logically that those that do survive are best adapted)
Key points about evolution and natural selection
o Only inherited traits are those that natural selection can work on
o These traits must be found in variations in the population
o Natural selection for some traits over others will change if the environmental pressures change
Homology arises when organisms have similar anatomical (homologous) structures that may have different current uses yet evolved from a common ancestor
o Comparative embryology can show homologous structures in embryos that are not evident in adult organisms
o Vestigial structures are currently in organisms but do not have a noticeable function but might have had one in an ancestor of the species
Convergent evolution of analogous structures
occur when distinct lines of organisms independently evolve similar structures based on natural selection in similar environments or pressure; does not require common ancestors
Aristotle
Greek philosopher who believed life forms were made perfect for their place in the world and stayed unchanging; developed scala naturae concept which ranked organisms like rungs on a ladder, increasing in complexity. This ranking does not support the Darwinian notion of evolutionary change in organisms.
Linnaeus
Swedish scientist who founded the field of taxonomy which seeks to organize and classify all living organisms. While Linnaeus’ classification system follows well with Darwin’s eventual concept of the “Evolutionary Tree of Life”, Linnaeus himself believed in a divine creation of all living creatures rather than being directed by an evolutionary force and by their environments.
Cuvier
French geologist who developed concept of catastrophism which sought to explain new species’ appearance not by gradual change but by abrupt disruptions which caused old species to be wiped out locally and new species to fill in their places from other areas. This process does not match with Darwin’s concept of species adjusting over time to gradual change in their environments.
Hutton and Lyell
Geologists who both supported idea that Earth’s surface changes slowly from continuous forces and that those forces are still optional today (e.g. Canyon being “carved” out of landscape by action of rivers). Lyell developed concept of uniformitarianism which states these mechanisms of change are constant over time. These geological principles matched well with Darwin’s idea of slow change in organisms as well over time.
Larmarck
French scientist who was first to attempt an explanation of how organisms change over time. He proposed a “use and disuse” principle which suggested that body characteristics that are used more will become more prominent and those that are not used will become less so. One example would be working out with weights to make larger muscles. Larmarck proposed additionally that these “acquired characteristics” (and therefore not inherited) could be passed on to offspring. Unfortunately, there is no genetic basis for this type of inheritance for the actual DNA sequence.
Mathus
Economist who contented that much of mankind’s problems such as disease, famine and war stem from overpopulation and therefore limited resources. This idea led Darwin to consider the fact that most species produce more individuals than can survive which drives the concept that only those individuals best suited for their environment will live to pass on their genes.
What were some of the major observations Darwin made on his voyage on the HMS Beagle?
Darwin noticed species that were closer geographically were more similar to each other than comparing species from different areas, such as the tropics versus temperate areas. His witnessing of an earthquake in South America and the subsequent change in the geology of the land made him question again the age of the Earth and how change over time in the Earth’s surface could explain the movement of fossils from earlier times. The Galapagos Islands off the coast of South America forced him to further think about the geographic distribution of species as he noticed different species of birds and other animals between the different islands and he began to notice the specific adaptations different species had in their unique environments. These observations made him think more abou thow species might develop after they had been separated from the mainland and were able to speciate each island in possibly different ways.
Explain how adaptations and natural selection work together as the driving forces behind evolution.
Adaptations are inherited characteristics of organisms that enhance their survival and reproduction in specific environments. Natural selection is a process in which individuals that have certain inherited traits tend to survive and reproduce at higher rates than other individuals because of those traits. In a nutshell, the organisms that are best adapted to their particular environment will be the ones natural selection will “allow” to live better and reproduce more so therefore the specific genes that are responsible for the best suited adaptations will be the ones most likely passed on and be in the next generation. Over time, this leads to possible changes in the populations as those with the best traits for survival are more represented in the population. If the environment changes, even very slowly, over time natural selection will alter which adaptations are the best suited and this can lead to changes in species, even to the point of a new species emerging.
What was the signficance of Darwin’s Tree of Life to evolutionary theory?
Darwin thought of the history life best represented as a “tree” with earlier ancestral organisms situation at the base or trunk of the tree and then new species branching out so that the tips of the branches indicated the more recent, modern species. Each fork of the tree represented the mores recent common ancestor to all organisms branching out from that ancestor. By following the speciation through the branches of the tree, one can trace how evolution directed the formation of new species. This evolutionary tree of life matched with Linneaus’ classification system although Lineaus based his system more on phyisical resemblances and not evolution.
How does variation in a population and differential survival rate contribute to evolution?
Darwin realized that in order for natural selection to take place, organisms needed to be genetically different from each other or at the very least, there needed to be the potential for genetic variation. We know now much of that variation comes from possibility of mixing DNA during events such as crossing over during meiosis or random mutations but in the end, whatever the cause of the variation, there are genetic differences between organisms in populations. Species are not just clones of each other with identical DNA. Once there is genetic difference, that may cause some organisms to survive better than others and therefore their genomes passed on more frequently to more offspring. The second part, the differential survival rate, is important because it sets up the pressure for some organisms to survive and others not to survive. Organisms generally produce more offspring than can possibly survive based on the available resources such as food or shelter. That forces those that have a better chance at surviving—whether having better skills at finding the limited resources or somehow ensuring that their offspring survive while others don’t, will be selected for. If there was always plenty of resources, all organisms, regardless of their adaptations would pass on their genes and therefore natural selection would not have a driving force.
Discuss how antibiotic resistant bacterial species is evidence of evolution.
A common misconception about evolution is that you can not study the process over a shorter time frame so you need to depend on fossil evidence and other data that is not as direct as watching evolution happen more quickly. However when you study species such as bacteria that can reproduce very quickly and therefore go through many more generations in a relatively short period of time, scientists can witness evolution “first hand” so to speak. In the case of antibiotic resistance in bacteria such as MRSA, what we are seeing is the ability of some bacteria to have a natural resistent to the antibiotics that would normally kill them. Let’s say for the sake of argument, the original population of bacteria has 1 million cells and 999,999 of them died with exposed to an antibiotic. But just one of those bacterial cells had a random mutation that made it not be effected by the antibiotic for some reason so it lived. It will therefore pass on its genes to its offspring and they would also survive if they also have this “resistence gene”. Even if other populations of bacteria nearby did not have the gene to protect them and therefore also died with exposure, over time (and with bacteria, that time scale is rapidly sped up since they can reproduce so quickly and in vast quantities), many of the bacterial cells in the population could end up having the resistence to the antibiotic.
What is the significance of homology and vestigial structures in evolutionary theory?
Homology is the existence of certain traits between species is evidence that those species had a common ancestor. The classic example is the forelimb of mammals. All mammals share a common arrangement of bones from their shoulder region to the tips of their digits. The basic structure is all the same whether you are a human or a whale so the theory is some common ancestor had that arrangement of bones. But evolution over time has allowed for the bones to have different functions that were driven by the different environments the mammals lived it. So for humans, the forelimb is used for carrying as humans evolved on land and the need to carry tools or weapons or other human activity strengthened the selection for arms to function in that way. For a whale, who is not lifting anything, the forelimb evolved into a more effective “paddle” to help it swim through the water better. When you look at the eventual structures being very similar in all these types of mammals, it is less likely they all evolved independently and more likely they evolved from a common ancestor. Vestigial structures are anatomical features that serve no current day purpose to an organism for its survival. Typically these structures once had a function in an earlier ancestor of an organism but that function was lost over time. Other organisms that share a common ancestor may or may not have lost the function so the structures may be still functional in current times.
What is convergent evolution and how does it relate to evolutionary theory?
Convergent evolution occurs when 2 or more species that do NOT share a recent common ancestor each evolve the same particular trait in response to their shared type of environment or ecological niche. For example, the protein that codes for “antifreeze” in the blood of aquatic fish that live in the Artic and Antarctic both evolved independently and did not come from a common ancestor. The fact such a trait evolved twice lends credibility to the fact it is a trait that is well matched to the cold environments in both locations and this adaptation gives organisms that possess it a selective advantage.
