Living earth unit test (march 19th)
What's the difference between a homologous structure, and analogous structure, and a vestigial structure? Give examples of each!
A homologous structure is a body part that exhibits similar structure, but different function in different organisms. It evolved between two different species through the sharing of a common ancestor (which is why their structures are similar), but independently ended up serving different functions to suit the needs of the organism. An analogous structure is the opposite: different structure, but same function. This is a result of convergent evolution: different species developing the need for a particular function (i.e. swimming in the example below), but have different structures due to the absence of a common ancestor. A vestigial structure is a body structure that may have once been useful in our ancestor's past, but that has lost function over time. In humans, these include: wisdom teeth, tonsils, the tail bone, and the appendix.
What does it mean for an element (or isotope) to be "radioactive"? Why are some radioactive and others are not? What is radioactive dating?
A radioactive isotope is a nucleus of an atom that is unstable, usually due to an unfavorable proton to neutron ratio. In class, I described this as analogous to when a baby first learns to walk, it's hard for it to stand up and hold the weight of its own head. So generally the nucleus of a radioactive isotope will lose particles over time to try to achieve greater stability. This process is known as radioactive decay. The amount of time it takes for a substance to decay to half its original size is known as the substance's half life. In turn, half lives can be used to determine the approximate age of a fossil, geological sample, etc.
How do you calculate an allele / gene frequency? Calculate the allele frequencies for the population of frogs in the picture below:
Allele Frequency = (# of Specific Allele) / (Total # Alleles in Population) x 100 RED FROGS: 1 / 15 (6.67%) PURPLE FROGS: 2 / 15 (13.3%) GREEN FROGS: 12 / 15 (80%)
What makes an organism "biologically fit"?
Biologically fit refers to an organism's ability to survive and reproduce. Generally, that implies that it has developed the ability to adapt well to its surroundings.
Provide at least 3 examples of adaptations various organisms have developed to survive.
Cacti have developed waxy skin to be able to store water through long periods of drought. Polar bears have developed thick fur to endure cold, arctic temperatures. Several species (leopards, chameleons, geckos, squirrels, etc.) can camouflage with their environment to avoid predators (or to be able to sneak up on their prey).
The scientific name for humans, Homo sapien, is derived from the 2-word naming system known as ... ? Who developed this system?
Carl Linnaeus developed the 2-word naming system, known as Binomial Nomenclature, that we currently use to classify organisms
Who was Charles Darwin, and what did he discover on his trip around the world?
Charles Darwin was a naturalist who traveled the world aboard the HMS Beagle, gathering data and live samples about the characteristics and behavior of various species (which would later form the basis for his proposed Theory of Evolution).
In the notes, we discussed 6 different pieces of evidence that we have to support Darwin's Theory of Evolution. What are they? You should be familiar with (be able to explain) each one!
DNA Sequences, the Fossil Record, Biogeography, Comparative Anatomy / Homologous Structures, Embryology, and Vestigial Structures. See notes from 1/31, 2/1 for a description of each one.
What did Darwin notice about the finches on the Galapagos Islands, and what was the explanation for this observation?
Darwin noticed that the beaks of various finches varied from island to island, presumably to suit whatever they ate. The design, shape, and size of each beak was specialized to help each species of finch to obtain food.
State Darwin's Theory of Evolution by Natural Selection. The name of his 1859 publication in which he discussed this was famously titled ...
Darwin proposed that species change over time by adapting to their surroundings, and that those best fit will tend to survive and reproduce. He published his findings in "On the Origin of Species"
What does antibiotic resistance have to do with natural selection?
If a mutation occurs that allows a bacterium (or a strain of it) to develop antibiotic resistance, then it will be more likely to survive. In essence, this is just an example of "survival of the fittest". Think back to the Evidence for Evolution Activity (the one with the packet of pictures that we examined) or the pGLO Lab that we did - both illustrate how the acquisition of antibiotic resistance enables the bacteria to survive.
Lamarck proposed the idea of "acquired characteristics" (also referred to as "Use and Disuse"). Explain this proposal using the evolution of giraffe necks.
It was originally proposed that species "acquired characteristics" due to environmental use/disuse (as opposed to inheriting the trait). Lamarck, for example, believed that giraffes had developed long necks because the environment dictated or favored them - giraffes were able to reach higher up on trees in search of food. Please note that Lamarck's proposal of "Use and Disuse" has largely been discredited since.
Not including "Domain", what are 7 levels of classification, from LARGEST to SMALLEST?
Kingdom, Phylum, Class, Order, Family, Genus, Species (remember: "King Philip Came Over For Good Spaghetti")
Distinguish between natural and artificial selection.
Natural selection is Darwin's proposed mechanism of evolution: species that can adapt to their environment better will tend to survive and produce more offspring. Artificial selection ("selective breeding") involves genetically manipulating the phenotype of an organism by selecting for specific traits. This is how many household dog breeds were initially established, as we saw in the "Dogs and More Dogs" video we watched in class.
Explain the relationship between natural selection and genetic drift.
Natural selection is the process by which changes in the gene pool are a result of something SKILL-based: an organism must be well-adapted to survive and reproduce. Genetic drift, on the other hand, is when changes in the gene pool are caused by some random event, like a natural disaster, and are thus NOT based on skill at all.
In 3 - 5 sentences, explain how the following terms are connected: speciation, population, species, gene pool, reproductive isolation.
Speciation is the process by which a new species is formed. A "population" refers to ALL members of the same species living in a particular area or region. Members of the same species share the same gene pool, and are reproductively isolated, meaning they can only naturally breed with other members of the same species.
The study of classifying and naming organisms is known as ... ? What purpose does this serve?
Taxonomy is the study of classifying and naming organisms. This branch of science was established to help scientists (a) refer to a particular species by name, and (b) determine the evolutionary relationships of different species.
Describe an example of the Founder Effect and Bottleneck Effect to illustrate your understanding of how they differ.
The Founder Effect is when a small subgroup of a larger population migrates to a new area and diverges into a completely different species. An example of this that we discussed in class was the Amish Community in New England: a small group of these individuals had splintered off and only remarried and had kids with members of their community. A genetic disorder, known as polydactyly (more than 5 fingers or toes) developed within the population and to this day, is the reason why people of Amish descent are at high-risk for the disorder. The Bottleneck Effect is when a natural disaster (like an earthquake, fire, flood, etc.) wipes out a large portion of a population, causing drastic fluctuations in the gene pool. There are several examples of these in various species, from cheetahs to giant tortoises on the Galapagos.
Variation amongst members of the same species is attributed largely to what 2 factors? Explain how these factors enhance biodiversity.
Variation is a result of (1) mutations at the molecular level, and (2) gene shuffling (crossing over) during Meiosis (reproduction). Both account for the enormous range of traits and characteristics in species all across our planet! Editing the genetic code even slightly produces differing phenotypes, even in members of the same species, resulting in different appearances and different traits (such as the bird beaks in the Galapagos finches).
What is a cladogram and what does it show?
a branching diagram showing the cladistic relationship between a number of species.
Fermium-253 has a half-life of 0.334 seconds. A radioactive sample is considered to be completely decayed after 10 half-lives. How much time will elapse for this sample to be considered gone?
10 half-lives) x (0.334 seconds) = 3.34 seconds of total time will elapse.
Os-182 has a half-life of 21.5 hours. How many grams of a 10.0 gram sample would have decayed after exactly three half-lives?
10.0g 5.0g 2.5g 1.25g left over 10.0g - 1.25g = 8.75g would have decayed 1.25g would be remaining after 3 half-lives, but 8.75g of the sample would have decayed in this amount of time
100.0 grams of an isotope with a half-life of 36.0 hours is present at time zero. How much time will have elapsed when 5.00 grams remains?
100.0g 50.0g 25.0g 12.5g 6.25g 3.125g Therefore, when 5.00g remains, the substance will have undergone somewhere between 4 and 5 half lives. Since we know the half life of the substance, we can calculate approximately the total amount of time that would have elapsed: 36.0 hours x 4 half lives = 144 hours 36.0 hours x 5 half lives = 180 hours So between 144 hours - 180 hours would have passed.
After 24.0 days, 2.00 milligrams of an original 128.0 milligram sample remain. What is the half-life of the sample?
128.0mg 64.0mg 32.0mg 16.0mg 8.0mg 4.0mg 2.0mg So in 24.0 days, the sample has undergone 6 half lives. 24.0 days / 6 half-lives = 4.0 days The half-life of the sample is 4.0 days
What are the 3 Domains? What are the 6 Kingdoms?
3 Domains: Archaea, Bacteria, Eukarya 6 Kingdoms: Animals, Plants, Fungi, Protists, Archaebacteria, Eubacteria
The half-life of Zn-71 is 2.4 minutes. If one had 100.0 g at the beginning, how many grams would be left after 7.2 minutes have elapsed?
7.2 minutes / 2.4 minutes = 3 half lives 100.0g 50.0g 25.0g 12.5g would be remaining