Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
57 Cards in this Set
- Front
- Back
|
Define Microevolution and define evolution. How are they related?
|
Microevolution: any change in the frequency of alleles in a gene pool (population) from one generation to the next
Evolution: “descent with modification” from a common ancestor, resulting in changes in the features of organisms across generations. Possible result in formation of new species or loss of others - Related because the processes which alter gene pools from one generation to the next are responsible for generating all biological diversity - including traits ect. |
|
|
5 Practical Reasons for studying Evolution (Describe 2)
|
-Agriculture
-Natural Products -Understanding ourselves -Conservation: knowledge of how organisms respond to environmental change is vital if we are to somehow protect biodiversity from human activity. E.g., How do we expect various organisms to respond to global climate change? Shrinking habitats? Introduction of exotic species? -Health Sciences: understand how to combat and prevent diseases. E.g., developing new antibiotics, new medicines to combat rapidly-evolving viruses, including HIV |
|
|
What is the well-known quote by the famous evolutionary biologist Theodosius Dobzhansky? Explain what he meant when he said it.
|
“Nothing in biology makes sense except in the light of evolution.”
-Evolution is the unifying theory of biology -Remember that a theory seeks to generate groups of potentially related hypotheses, which explain many potentially related observations -The Theory of Evolution can be used to generate hypotheses to explain the ultimate cause of ALL biological phenomena |
|
|
Explain the difference between natural selection and evolution
|
Evolution is a gradual process in which something changes into a different and usually more complex or better form whereas natural selection is the process in nature by which, according to Darwin's theory of evolution, only the organisms best adapted to their environment tend to survive and transmit their genetic characteristics in increasing numbers to succeeding generations while those less adapted tend to be eliminated.
|
|
|
What two conditions are required of populations in order for natural selection to occur? Be able to briefly explain each
|
-Competition for limited resources (e.g., food, shelter, mates, etc.)
-Variation among individuals in their ability to acquire those limited resources Then: Individuals with beneficial traits will tend to survive and reproduce more than individuals with less beneficial traits. |
|
|
What is the additional requirement for natural selection to result in evolution? Explain this.
|
-traits must be inherited. Individuals with beneficial traits will tend to survive and reproduce more than individuals with less effective traits.Those traits can be inherited from parents to offspring. Then successful parents will pass beneficial traits on to offspring. From generation to generation, individuals with beneficial traits will represent an ever greater proportion of the whole population.
|
|
|
What were the five major components (ideas) of Darwin’s theory of evolution? Be able to briefly explain any two of them.
|
-Evolution
-Common Descent -Natural Selection -Population level: Evolution is a POPULATION-LEVEL phenomenon. In other words, evolution is a change in the relative frequencies of traits in a POPULATION from generation to generation. Individuals do not evolve; populations evolve. -Gradualness: Natural selection takes a long time to change traits and create complex adaptations. This is okay because the world is very old. The gradual nature of evolutionary change has been a contentious issue in evolutionary biology. |
|
|
Describe the Hurd and Eisenberg experiment with houseflies. How did the experiment proceed, and what was the result? What does this experiment tell us about how speciation can occur, and how fast?
|
Hurd and Eisenberg put a thousand Drosophila flies into a chamber that had traps at its top and bottom. As they flew around some flies ended up in the top trap while others ended up in the bottom trap. After waiting, they then removed the flies and allowed the bottom trapped flies to mate with other bottom trapped flies. They reared the new generation of flies and released them back into the chamber and repeated the collection and mating process for 16 generations. With this, the tendency for the flies to go up or down became much stronger and it took less time for collection. They then mixed the up and down populations together and nearly all of the flies chose to mate with flies that traveled in the same direction. A preference had evolved that would reduce the flow of genes between the two populations. What this tells us is that speciation doesn’t necessarily take millions of years. All it takes is a preference for one thing or another.
|
|
|
What are four means by which evolution can occur? Briefly tell me about each one.
|
Mutation: alteration in an organism's DNA. Beneficial or “adaptive mutations are indispensable to evolution.
Genetic Drift: Chance alteration of gene frequencies in a population. Most strongly affects small populations. Can occur when populations are reduced to small numbers or when a few individuals from a pop migrate to a new isolated location and start a new population. Gene Flow: Sexual selection: Occurs when some members of a pop mate more often than other members. Natural selection: Some ind. will be more successful than others in surviving and hence reproducing, owing to traits that give them a better “fit” with their environment. The alleles of those who reproduce more will increase in frequency in a pop. |
|
|
Define natural selection. List four different kinds of traits on which natural selection can act (hint: I gave detailed examples that showed selection on four different kinds of traits in lecture). Explain any one example in a little detail.
|
The favoring of some individuals over others due to traits that they exhibit. These “agents” of selection can be food, predators, weather, parasites, and or habitats. Selection acts on individuals, “sees” phenotypes, and occurs within a generation.
-Peppered Moth: SELECTION ON PHYSICAL APPEARANCE. INDUSTRIAL MELANISM Moth originally mostly peppered morph. Thought to be camouflaged on lichen-covered trees. Eaten by birds. Industrial revolution in England killed lichens and darkened tree trunks with soot. Rare black morph became more common. Since environmental cleanup, peppered form has become more common again. -Common Mussel: SELECTION ON A GENE AT A CELLULAR LEVEL -Darwin’s Finches: SELECTION ON COLLECTION OF ENERGY SOURCE -3 Spined Stickleback: SELECTION ON REPRODUCTION (EGG SIZE) |
|
|
Define fitness.
|
Fitness: the contribution an individual (or genotype) makes to the gene pool of the next generation, relative to the contribution of other individuals. We define fitness not by the characteristics of the individual organism at present, but instead what it leaves behind in offspring.
|
|
|
The equation R = h2 * S neatly summarizes evolution via natural selection. What does each term mean, and how do they relate?
|
R=response to selection (how much the pop. changes genetically) R=Evolution
h^2 = the heritability (the degree of genetic control of the trait) S= selection differential (the strength of selection on the phenotype) For evolution to occur, you must have a selection differential higher than zero and the trait must be heritable. Knowing the strength of selection and the heritability of the trait we are able to predict evolution. |
|
|
What is convergent evolution?
|
Convergent evolution describes the independent evolution of similar features in species of different lineages. Traits that are similar do not mean that species are related: bird wings vs. bat wings
|
|
|
What is the difference between continuous and discrete phenotypic variation? Give an example of each kind.
|
Discrete phenotypic variation is when a trait only exhibits a few different categories. Ex: WHITE OR RED FLOWER
Continuous phenotypic variation is when individuals of a population cannot be readily separated into a small number of distinct (= discrete) categories, we say that the variation is continuous (aka, quantitative). Ex: HEIGHT IN HUMANS |
|
|
Define sexual selection. What are the two kinds of sexual selection? Give an example of each.
|
Sexual selection is natural selection for mating success.
-Intrasexual selection (competition among members of the same sex) EX: fights, displays instead of fights ELK -Intersexual selection (mate choice)EX:often results in selection for male color, behavior, etc. DUCKS CHOOSE MOST COLORFUL OR BEST DANCE |
|
|
Why are females the choosier sex? What is “honest advertising”?
|
Females are the choosier sex because females generally have fewer opportunities to mate, so must be more “careful” in their choices in order to produce the healthiest and best offspring.
|
|
|
Explain how evolution can help us understand why some people can digest milk, while others cannot do so
|
Evolution can help us understand this because the ability of people to tolerate lactose as an adult is the result of human natural selection over the past few millennia. Typically, when young mammals are weaned they stop producing lactase, but once humans began domesticating cattle their diets became rich in dairy. It soon became favorable to have the gene for lactase (LCT). In Europe, this gene is most common in NW Europe where cattle herding originated and rarest in SE Europe (the furthest point from this origin)
|
|
|
Natural selection may be the most important cause of evolution, but it is not the only cause. What three other processes can cause evolution? Describe each of these.
|
Genetic Drift: Chance alteration of gene frequencies in a population. Most strongly affects small populations. Can occur when populations are reduced to small numbers or when a few individuals from a pop migrate to a new isolated location and start a new population.
Gene Flow: Immigration or Emmigration Mutation: alteration in an organism's DNA. Beneficial or “adaptive mutations are indispensable to evolution. |
|
|
What are the two forms of genetic drift? How are they different?
|
Bottleneck: Population bottlenecks occur when a population’s size is reduced for at least one generation. Because genetic drift acts more quickly to reduce genetic variation in small populations, undergoing a bottleneck can reduce a population’s genetic variation by a lot, even if the bottleneck doesn’t last for very many generations. Reduced genetic variation means that the population may not be able to adapt to new selection pressures, such as climatic change or a shift in available resources, because the genetic variation that selection would act on may have already drifted out of the population.
Founder’s effect: A founder effect occurs when a new colony is started by a few members of the original population. This small population size means that the colony may have reduced genetic variation from the original population and/or a non-random sample of the genes in the original population. |
|
|
Why is genetic drift such a concern to conservation biologists?
|
Is progressively more important as population size is reduced (i.e., causes
greater changes in small populations) • Can alter allele/genotype frequencies rapidly and dramatically • Can cause total loss of alleles, thus reducing overall genetic diversity • As a result, is important in conservation |
|
|
Define gene flow.
|
The movement of alleles into or out of a population.
Alleles can be transferred through the movement of individuals, or by movement of gametes (for example, pollen) –Migrant individuals must reproduce in the receiving population -Gene flow tends to reduce differences between populations over time – Alleles removed by selection are reintroduced |
|
|
Why can’t evolution via natural selection produce perfect organisms?
|
-Evolution is limited by historical constraints. Why are there no four-legged birds?
-Adaptations are often compromises (remember the idea of trade-offs?) -Natural selection is not the only “player” in the game...drift (a chance phenomenon) also is important, as is mutation -Selection can only act on existing variation... what is in the population NOW. Alleles do not appear or disappear “on demand” |
|
|
Describe Peter Buri’s experiment with the bw/bw75 alleles in fruit flies. What evolutionary mechanism was he investigating?
|
Buri put heterozygous flies into 107 flasks, each containing eight males and eight females. The flies mated and produced a new generation of flies. From each batch Buri chose eight males to and eight females to breed again. Buri did this for 19 generations. The flies did not follow the Hardy-Weinberg equilibrium and instead in certain populations one allele or the other disappeared entirely. In others, the populations ended up falling between the two extremes. He was investigating genetic drift....he used extremely small populations.
|
|
|
Name four of the different types of mutations scientists recognize. Be able to explain 2 in detail.
|
-point mutation: a single base changes from one nucleotide to another (aka a substitution)
-Insertion: a segment of DNA is inserted into the middle of an existing sequence. The insertion may be as short as a single base or as long as thousands of bases (including entire genes) -deletion: a segment of DNA may be deleted accidentally. A small portion of a gene may disappear, or an entire set of genes may be removed. -duplication: a segment of DNA is copied a second time. A small duplication can produce an extra copy of a region inside a gene. Entire genes can be duplicated. |
|
|
Briefly explain why the mitochondrion (we have 1,000’s in every cell) can be considered to be a complex adaptation.
|
An ancient anaerobic eucaryotic cell could not use oxygen to produce energy. The cell that it ate was not as complex but it was aerobic and therefore knew how to digest it’s food completely. When it got eaten, something about the cell membrane caused it to resist the digestive enzyme of the larger cell. The duplication of the mitochondria happens by itself when a cell begins to divide.
The mitochondria has it’s own DNA. Because the small cell is now safe and surrounded by lots of food, mutations that turn off some food digesting enzymes is okay. Eventually the small cell loses its ability to live outside of the big cell. Once this happens, mutations that favor cooperation are strongly favored. Can now get 18 times more energy out of food. |
|
|
Explain how gene duplication can produce new feature in an organism. You may use a sketch to explain gene duplication itself if you wish, but your answer must tell me how a new feature can arise due to the gene duplication).
|
One copy continues to be a G-protein coupled receptor and the other becomes a new feature because it has no job to do.
The new duplicate gene takes on new function. When the DNA is copied often there are hic-ups, and it gets duplicated. Mutations that change its function in a different way. |
|
|
What general type of ancestral protein did snake venom evolve? What was the function of this ancestral protein? What two major evolutionary steps led to the numerous types of snake venom we see today?
|
Beta-defensins...snakes evolved a beta defensins gene where it got turned on in other places other than the skin. It was expressed in the pancreas for fighting bacteria. Eventually beta defensins evolve into crotamine venom that is expressed only in venom glands in snakes. Having venom was a key innovation that lead
|
|
|
What is unusual about the left recurrent laryngeal nerve in vertebrate animals? Why is the nerve longer in humans than in fish, and why is it enormously long in giraffes?
|
7 neck vertebrae...all has to be coordinated. As things elongated, if we want to have a nerve that goes to the voice box, the left nerve has to take a path under the aortic artery elongated in humans. In giraffes, the heart got further and further and so did the aortic loop. The left nerve has to grow very long because of developmental constraints.
|
|
|
What is speciation? What is a species, according to the Biological Species Concept?
|
Biologists do not all have one single commonly decided definition but....is is the evolutionary process by which new biological species arise, and is the process by which diversity is generated.
Species (: a pop or group of pop whose members have the potential to interbreed in nature, and if they do, they produce viable fertile offspring. They are unable to produce viable fertile offspring if they mate with members of another species. Species are genetically distinct. Chromosomes need to be able to match. This definitions emphasises the genetic distinctness of species typified by reproductive incompatibility. |
|
|
How are the biological, phylogenetic, and evolutionary species concepts related?
|
biological: must produce viable fertile offspring
phylogenetic: a diagnosable cluster of individuals within which there is a parental pattern of ancestry and descent beyond and which exhibits a pattern of phylogenetic ancestry and descent among units of like kind. evolutionary: this is both of the previous two put together combines the genealogical basis of the phylogenetic species concept with the genetic basis of the biological species concept. An evolutionary species is a lineage of interbreeding organisms reproductively isolated from other lineages, that has a beginning and end, and a distinct evolutionary trajectory. |
|
|
What are the two patterns of speciation, and how are they different? Which is the one that generates biodiversity (more species than you started with)?
|
anagenesis: a gradual change within a single lineage so that eventually the descendents are considered to be a different species. (any change that adopts a new mutation) Probably more common than cladogenesis. At some point the ancestor may look nothing like the current species. Ex: a single type of horse evolving over time but is still same horse
cladogenesis: speciation via splitting of an ancestral lineage (a clade... set of living species plus their living ancestor. nested circles) Ex: the older species goes extinct while new one come about CLADOGENESIS GENERATES BIODIVERSITY |
|
|
Peripatric speciation is often called “founder effect” speciation. Why is this? Why does peripatric speciation often proceed very rapidly?
|
peripatric = orig. pop. and then a small number of ind. get isolated or migrate to new habitat....you get subset of orig. pop. living in new place. This is special because natural selection is different and these individuals will get shaped differently. You will also get intense genetic drift. This produces a new species very quickly because of.... new mutation, new selection, and genetic drift. They are “founding” a new place and a new species.
|
|
|
Explain how Dr. Mark Kirkpatrick used molecular genetic methods to determine whether allopatric or sympatric speciation caused the distribution of “gold” and “silver” cichlids he observed in some African lakes.
|
Nicaragua. Found in a whole set of lakes, two species of fish (gold and silver). They are diff. species, they don’t interbreed, but very similar. You see that because this is allopatric....large lake dried up into smaller lakes. OR one form in both big lakes....then sympatric speciation in all the little one. THIS IS WHAT HAPPENED. In all cases the closest genetic matches are the gold and silver within one lake = sympatric ONE BIG LAKE COLONIZED MANY SMALL LAKES, IN ALL LITTLE LAKES ONE FORM CREATED NEW SPECIES. THE CREATION OF TWO SPECIES FROM ONE IN THE SAME ENVIRONMENT.
|
|
|
What is the “function” of isolating mechanisms? What is the difference between pre-zygotic and post-zygotic isolating mechanisms? Could you explain one example of each?
WHAT CAN KEEP TWO SPECIES APART |
prezygotic: things that prevent interbreeding before physical mating occurs
habitat isolation: if they use different habitats they can’t breed (physically separated...most common type) temporal isolation: mating at different times (salmon) mating behavior: female preference. males dance, subtle differences (like in spiders) mechanical isolation: if a bee can’t get to the pollen it can’t transfer it. Why species typically chose one flower to focus on. (lock and key...dragonfly) gametic isolation: physical receptor in eggs and sperm postzygotic: when fertilization actually produces an embryo reduced hybrid viability: might be alive but is less viable or is fine but can’t reproduce itself (horse +donkey = mule) first gen. hybrids are fertile but when they mate their offspring is messed up (corn) |
|
|
Explain each of the three possible outcomes of hybridization when two populations, long separated, come back into contact.
|
reinforcement: when they have become just different enough, if they come back together the differences are strong enough that they choose not to reproduce together. Still compatable but they don’t want to have children. This reinforces the speciation.
fusion:They can also collapse back into one big gene pool. stability:Can remain. Not collapsing, but also not joining back together. THESE ALL DEPEND ON WHAT TRAITS HAVE BEEN MOST ALTERED. |
|
|
Briefly describe how humans got to have the three, small bones in our middle ear that help us to have such excellent hearing
|
Evolution does not produce innovations from scratch, it works on what already exists. The bones we use to hear once helped our ancestors bite. Bones of the middle ear started out as part of the lower jaw. In early synapsis, the foremost bone in the jaw (the dentary) held many teeth and the bones in the rear formed a hinge against the back of the skull. In the mammal lineage the dentary gradually became larger (favored by nat. sel. because they provided more strength than a group of smaller bones) Eventually the dentary became the sole bone of the jaw making direct contact with the back of the skull. Bones of the lower jaw then were co-opted into the network of bones in the ear. They served as levers that amplified faint high frequency sounds. This chain of bones later became free of attatchment.
|
|
|
Explain mutant paper
|
EVERYONE IS UNIQUE...when you are born, you are born with at least 60 new mutations that are specific to only you that you get from your parents. The results also
reveal that human genomes, like all genomes, are changed by the forces of mutation: our DNA is altered by differences in its code from that of our parents. Mutations that occur in sperm or egg cells will be 'new' mutations not seen in our parents. We know now that, in some families, most mutations might arise from the mother, in others most will arise from the father. This is a surprise: many people expected that in all families most mutations would come from the father, due to the additional number of times that the genome needs to be copied to make a sperm, as opposed to an egg." |
|
|
Explain how DNA data, fossil data, and data on the movement of the continents together gives a full picture of the evolutionary history of marsupials
|
-Scientists used mobile elements (DNA with the capacity to make copies of themselves) to produce a phylogeny of marsupials. The found that some mobile elements were shared uniquely by some species of marsupials but not by others. The pattern they uncovered was a nested hierarchy in which mobile elements revealed clades within clades.
-By using fossils to reconstruct the phylogeny they’ve been able to incorporate extinct species that have left no DNA behind. These studies support the hypothesis that marsupials moved from south america to australia and provide a more detailed route. Marsupial-like animals were living in china by 150 million yrs ago. They then dispersed into N. America, which at the time was linked to asia. Many new lineages of marsupials evolved in N. America over the next 55 million yers. From N. Amer. some marsupials dispersed to Europe. Eventually all of these Northern Hemisphere marsupials died out. Another set of N. American marsupials dispersed to s. america. From S. America this branch dispersed into antarctica and australia (which were both attached to S. Amer at the time) |
|
|
Explain the wonderfully neat evolutionary relationship of sharpshooters & Sulcia & Baumannia.
|
Sulcia and baumannia have evolved small genomes. Baumannia has lost all of its synthesizing amino acids except for histidine. The main service Baumannia provides for it’s sharp shooter host is synthesizing vitamins and other nutrients. Sucia, on the other hand, has retained all of its genes for amino acids - except for histidine. Together the two bacteria species can provide a sharpshooter with all of the amino acids it needs to stay alive. These two microbes have not oly coevolved with their insect host, but they have also coevolved with each other.
|
|
|
Define the term “clade”. If I showed you a diagram like one of those below, could you tell me if the colored part was a clade or not?
|
A clade is a grouping that includes a common ancestor and all the descendants (living and extinct) of that ancestor. Imagine clipping a single branch of the phylogeny—all of the organisms on that pruned branch make up a clade. YES
|
|
|
With respect to evolution, define homologies. Define analogies.
|
homologies: characters in different organisms that are similar because they were inherited from a common ancestor that also had that character.
analogies: traits that have separate evolutionary origins, but are superficially similar because they evolved to serve the same function. Analogies are the result of convergent evolution. |
|
|
Explain why bat wings and bird wings could be either homologous characters or analogous characters, depending on how you look at it.
|
Interestingly, though bird and bat wings are analogous as wings, as forelimbs they are homologous. Birds and bats did not inherit wings from a common ancestor with wings, but they did inherit forelimbs from a common ancestor with forelimbs.
|
|
|
Originally, the group of organisms that includes turtles, snakes, lizards, crocodiles and most dinosaurs was given the evolutionary name “reptiles”, because they all appeared to be descended from the first reptile to live on earth. Explain what birds have to do with how we now think of the term “reptile”.
|
The group known as the “reptiles” does not form a clade, as shown as shown in the figure on the
right. That means that either “reptile” is not a valid phylogenetic grouping or we have to start thinking of birds as reptiles. |
|
|
Why are birds considered to be dinosaurs?
|
Birds are, in fact, dinosaurs because they are part of the same clade called Dinosauria. Dinosaurs are a common ancestor of dinosaurs.
|
|
|
You study fossils, and you discover a new type that you think is transitional between two types of organisms. How would you convince others of this
|
ransitional fossil: Fossils that show intermediate characteristics (features that are intermediate in nature to those of organisms that existed both prior to them and after them) are called transitional fossils. Transitional fossils are inextricably linked to the idea of biological evolution.
-I would show them the exact transitional phases within the fossil. Within two species next to each other on the phylogeny. We must also know where in time these species exist. “you can consider everything to be a transitional organism.” |
|
|
When animals moved from the water onto the land, there were at least four challenges they faced. List these four challenges, and discuss any one in a little detail.
|
1. must withstand the effects of gravity (fish hover because of their swim bladder in water and “defy gravity” this doesn’t work on land)
2. Must be able to breathe air (gills do not work on land) 3. Must minimize water loss (desiccation) (dry out on land, are transparent to water) 4. Must adjust senses so they are suited for air instead of water. (eyes nor ears work the same on land as they do in water) |
|
|
In fish, the head and trunk are fused, but in amphibians they are not. What difference does this make for the animal, and how might it have been an advantage to an animal living in a shallow swamp?
|
Less mobile, they can’t swim very fast. A certain amount of water is required for fish to “swim like a fish”. Most fish that live in swamps are very sedentary. It becomes evolutionarily favorable to lay still for periods of time, less fin movement.
If the head and trunk are fused, to look around, it would have to move its entire body. This is less efficient. It also then can have a different placement of eyes thus aiding visibility with even less movement. With a neck you can view your environment without drawing attention to oneself by moving or muddying the water. |
|
|
At least four major body changes occurred during the fish-to-amphibian transition. List these, and briefly describe any one of them.
|
-LIMBS (Wrists, feet, and digits)
-HEAD FLATTENED OTHER WAY: head is not flattened side to side and instead flattened the other way (puts eyes closer together and gives binocular vision) -NECKS: loss of gill protecting bones to give rise to necks. -CHANGE OF GIRDLE STRUCTURE (disconnect the hips and shoulders from head) |
|
|
Critics of evolution frequently make statements like: “Science claims that fish evolved into amphibians, but they can’t show us a transitional fossil demonstrating this.” When they say this, they usually are talking about modern fish and amphibians. Why is this statement wrong? In your answer, use a diagram with arrows to show what they are saying, then add more arrows to your diagram to show why they are wrong.
|
Modern fish and modern amphibians are not directly related. They both came from a common ancestor.
arrows straight across is wrong. |
|
|
The first convincing “bird” fossil, Archaeopteryx, is actually misnamed. What four pieces of evidence indicate that this fossil was probably not a bird, but something transitional between reptiles and birds (probably actually closer to reptiles than birds, in fact)?
|
-toothed beak (reptilian character)
-wing claw (reptilian character) -airfoil wing with contour feathers (avian character) -long tail with many vertebrae (reptilian character) Almost all of its many traits are things in common with reptiles, not birds. 18 out of 20 traits are more reptilian. |
|
|
In 1871, Charles Darwin published his second major book. What was the title? What was it about? What prediction did Darwin make in his book? What anatomical feature of humans might have given Darwin a clue?
|
THE DESCENT OF MAN. Argued that the similarities between primates and humans were evidence that they have a common ancestor. They are both large bodied, have big brains for their bodies, and have a vestige of a tail. He argued therefore that apes were our closest primate relatives. The human lineage branched off from the ancestors of chimpanzees about 7 million years ago.
|
|
|
Describe the Miller-Urey experiment and tell how it supported the idea that life evolved very soon after the earth formed.
|
In 1953 Simulated the early atmosphere of the earth in a flask. Took hydrogen oxygen water methane ammonia and electricity. The electricity can get bonds to form. Most amino acids, simple sugars, and nucleotides and other small molecules that are precursors to monomers of macromolecules ( needed for life to form) spontaneously formed.
|
|
|
About half a billion years after life began, a group called the cyanobacteria evolved a very useful ability. What was this ability? What by-product of this ability helped make the environment of the earth suitable for animals to evolve? Explain how it did so.
|
Cyanobacteria evolves photosynthesis 3 billion years ago....there were modest levels of oxygen in atmosphere by 2.3 billion years ago. The earth “waited” to get more and more oxygen as a byproduct of the cyanobacteria’s photosynthesis. For this process produces oxygen as a bi-product. Oxygen greatly increased 700 million yrs. ago. Oxygen reached current levels in the cambrian period.
|
|
|
What type of organism first colonized land? What particular “type” of these organisms were the first ones of their kind to make it onto land? What would their distribution on land have been like?
|
PLANTS first life on land (439-409 mya) simple plants like mosses descended from algae. They were really simple. Mosses are almost not plants because they are so simple. FERNS were the first “vasular plants” (400 mya).
-Huge forests covered the planets. Probably covered almost everything. (carboniferous period) |
|
|
What is the “Cambrian explosion”, and when did it occur? Why could the “explosion” occur when it did in the history of life on earth (give three reasons)? Where are Cambrian fossils particularly abundant?
|
(9:20pm...if the history of the planet was only a day)
CAMBRIAN EXPLOSION: huge burst of biodiversity and life....ended with a mass extinction. According to the fossil record, nearly all major groups of animals that currently exist (and most that are now extinct) originated in about a 10-30 million year period (530 mya) CAUSES: 1. large increase in oxygen allows for aerobic respiration and thus the evolution of many complex organisms (must wait until plants fill air with oxygen) 2. calcium carbonate (CaCO3) was more abundant, and that is an important component in the shells of many organisms....having shells and skeletons may have allowed animals to evolve larger sizes and/or more complexity. 3. ozone: must have lots of oxygen in the atmosphere so that it can be turned into (O3) ozone....this blocks ultraviolet rays from causing organisms harm. 4. by this time you had the ancestral animals in the oceans, they were complex....genetically ready to take advantage of the oxygen and had enough diversity to rapidly evolve. ---China’s fossils are become important but ROCKY MOUNTAINS IN WESTERN CANADA are best. Burgess shales....(560 mya) in oceans but rose up into the mountains. Has fossils of very bizarre looking extinct animals. |
|
|
Since the Cambrian explosion, life on earth has been repeatedly affected by two alternating features. What are these? What is thought to have caused the mass extinction at the end of the Cretaceous period (the one that zapped the dinosaurs)?
|
Mass Extinctions and EXPLOSIONS. THESE are a natural part of life. There have been 6 mass extinction events in geological history. Biodiversity after “recovery” is always different than biodiversity before.
K-T EXTINCTION: Meteor impact near the yucatan peninsula. The earth cooled rapidly and dinosaurs went extinct...unable to regulate body temperature as well as others. |
|
|
Number the organisms on the list below in the order in which they evolved. Give me the approximate time each evolved (in millions of years ago):
|
1. The first animal (640 mya...first definite fossil but probably earlier)
2. Land plants (425-405 mya) 3. The first amphibian (405-345 mya) 4. Insects (345-280 mya) 5. Birds (181-135 mya) |
