OBJECTIVE SHEET EVOLUTION - SD#5 2 Evolution and... · OBJECTIVE SHEET EVOLUTION 1. Describe the...
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OBJECTIVE SHEET EVOLUTION
1. Describe the contributions of Hutton,Lyell, Lamarck and Malthus to the evolutionary thought of Charles Darwin.
2. Explain Natural Selection as a
mechanism to describe how evolution occurs. Include the role of artificial selection, inherited
variation, the struggle for existence and survival of the fittest.
3. Discuss the various clues that provide evidence for evolution.
4. Define the following: descent with modification, common descent,
5. Define the following: gene, allele, segregation, independent assortment, mutation, chromosome, phenotype, genotype, dominant allele, recessive allele, incomplete/codominance, polygenic traits, diploid, haploid, homozygous, heterozygous
6. Solve single (hybrid) and double (dihybrid) factor crosses using Punnett
7. Discuss how genes and gene variation can provide us with a genetic definition of evolution.
8. Discuss how natural selection can affect the distribution of phenotypes in
any of three ways: directional, stabilizing or disruptive selection.
9. Identify how Genetic Drift can also provide a source of evolutionary change. Provide an example of the “founder effect” as an example of genetic drift.
10. Discuss the Hardy-Weinberg principle as it applies to genetic equilibrium.
What are the 5 conditions that if changed cause evolution to occur.
11. Explain how the following Isolating Mechanisms help bring about Speciation: Behavioral Isolation, Geographic isolation and Temporal Isolation.
12. Explain the role of extinction in macroevolution. Differentiate among and
give examples of Adaptive radiation, convergent evolution and co-evolution.
13. Differentiate among gradualism and punctuated equilibrium.
“There is grandeur in this view of life… from so simple a beginning endless forms most beautiful and most wonderful have been, and are being evolved.” – Charles Darwin 1859. It has been called by some the greatest idea that any human has ever had. Charles Darwin was able to unite the two most disparate features of our universe, the world of purposeless, meaningless, matter in motion and the world of meaning, purpose, and life.
A new era of biology began on November 24, 1859, the day Charles Darwin published
On the Origin of Species by Means of Natural Selection. Darwin’s book drew a
cohesive picture of life by connecting the dots among what had once seemed a
bewildering array of unrelated observations. The Origin of Species focused biologists’
attention on the great diversity of organisms—their origins and relationships, their
similarities and differences, their geographic distribution, and their adaptations to
Darwin made two major points in The Origin of Species. First, he presented evidence
that the many species of organisms presently inhabiting Earth are descendants of
ancestral species that were different from the modern species. Second, he proposed a
mechanism for this evolutionary process, which he termed natural selection.
Evolution is such a fundamental concept that its study illuminates biology at every level
from molecules to ecosystems, and it continues to transform medicine, agriculture,
biotechnology, conservation biology and many others.
The Cosmic Calendar If we were to squeeze all of time into a calendar year, you would find that humans have not been here very long. (Each day represents over 12 million years of time)
Big Bang January 1
Origin of the Milky Way Galaxy May 1
Origin of our Solar system September 9
Formation of the Earth September 14
Origin of Life on Earth ~ September 25
Formation of the oldest rocks known on Earth October 2
Date of the oldest fossils (cyano-bacteria) October 9
Invention of sex (by microorganisms ~ November 1
Oldest fossil photosynthetic plants November 12
Eukaryotes (first cells with nuclei) flourish November 15
Sunday Monday Tuesday Wednesday Thursday Friday Saturday
1 Significant oxygen develops on Earth
2 3 4 5 Extensive vulcanism and channel formation on Mars
8 9 10 11 12 13
14 15 16 First Worms
17 Precambrian end. Paleozoic/ Cambrium begin. Invertebrates flourish
18 1st oceanic plankton. Trilobites flourish
19 Ordovician 1st fish 1st vertebrates
20 Silurian 1st vascular plants which colonize land
21 Devonian 1st insects Animals colonize land
22 1st Amphibians 1st winged insects
23 Carboniferous Era 1st trees 1st reptiles
24 Permian period. 1st dinosaurs.
25 Paleozoic Era ends. Mesozoic Era begins
26 Triassic period. 1st mammals
27 Jurassic period. 1st birds.
28 Cretaceous Period 1st flowers. Dinosaurs extinct
29 Mesozoic Era ends. Cenozoic Era begins 1st whales 1st primates
30 1st evolution of frontal lobes in the brains of primates. 1st hominids. Giant mammals
31 End of Pliocene. Quaternary period 1st humans.
Origin of Proconsul and Ramapithecus, probable ancestors of apes and men
1st humans ~10:30 pm
Widespread use of stone tools 11:00 pm
Domestication of fire by Peking man 11:46 pm
Beginning of most recent glacial formation period 11:56 pm
Seafarers settle Australia 11:58 pm
Extensive cave painting in Europe 11:59 pm
Invention of agriculture 11:59:20 pm
Neolithic civilization, 1st cities 11:59:35 pm
1st dynasties in Sumer, Ebla and Egypt; development of astronomy
Invention of the alphabet; Akkadian empire 11:59:51 pm
Hammurabic legal codes in Babylon; Middle Kingdom in Egypt 11:59:52 pm
Bronze metallurgy; Mycenaean culture; Trojan war; Olmecs; compass
Iron metallurgy; 1st Assyrian empire; Kingdom of Israel, Carthage 11:59:54 pm
Asokan India; Ch’in Dynasty China; Periclean Athens; birth of Buddha
Euclidean geometry; Archimedean physics; Roman Empire, Ptolemaic Astronomy
Zero and decimals invented in Indian arithmetic; Rome falls; Moslem conquests
Mayan civilization; Sung dynasty China; Byzantine empire; Mongol invasion; the Crusades
Renaissance in Europe; voyages of discovery from Europe and from Ming dynasty China; emergence of Scientific method
Widespread development of science and technology; emergence of global agriculture; acquisition of the means of self-destruction of the human species; first steps in spacecraft planetary exploration and the search for extraterrestrial intelligence
Now: The first second of New Year’s Day
Reference text pgs. 369-377 There is an astounding diversity of life on our planet. Evolutionary theory accounts for this diversity. It is a collection of scientific facts, observations, and hypotheses tested over the last 150 years and has explained the differences and similarities observed with all life forms both extinct and living today. A scientific theory is a well-supported _______________ explanation of phenomena that have occurred in the ________________ world. Darwin set sail aboard the _______________________ on a trip around the world. No one knew that this voyage was one of the most important voyages in the history of science.
Starting from the British Isles, follow the route taken by Darwin to South America, the Galapagos Islands and around the southern tips of Australia and Africa, only to return to South America again before heading home to England. Find this picture in colour. If there was one thing that Darwin excelled at, it was his powers of observation. His curiosity and analytical nature were ultimately the keys to his success as a scientist. During his travels, Darwin came to view every new finding as a piece in an extraordinary puzzle: a scientific explanation for the diversity of life on this planet.
Darwin made some keen observations on his travels. He was puzzled by the distribution of life forms in the variety of habitats that he encountered along the way. The patterns of diversity posed a challenge to Darwin. Besides the living organisms encountered on his voyage, Darwin collected fossils, which are the ________________________________________. How did the fossils Darwin observed compare with the living organisms he studied? _______________________________________________________ _______________________________________________________ _______________________________________________________ Of all the Beagle’s ports of call, the one that influenced Darwin the most was a group of small islands located 1000 km west of Ecuador. These islands are called ____________________________. Although they were close together, the islands had ________________________________. Darwin was most intrigued with the three different species of land tortoises. Explain why three different islands had three different species of tortoise. _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ Darwin also noticed the strange variety of finches on the island. The different islands produced birds with a multitude of beak shapes. What interested Darwin was that a particular beak shape allowed a bird to forage for the type of seed found only on the island inhabited by that species of bird. Darwin began to hypothesize that these separate species of bird would have evolved from an original South American ancestor species after becoming isolated from one another. This was truly a revolutionary idea that would shock the world.
Summarize the contributions of the following individuals to Darwin’s thinking: James Hutton _______________________________ _______________________________ _______________________________ _______________________________ _______________________________ Charles Lyell _______________________________ _______________________________ _______________________________ _______________________________ _______________________________
How would Lamarck explain the diagram of the fiddler crab below?
What did Darwin realize when he read the book published by Thomas Malthus? _________________________________________ _________________________________________ _________________________________________
Reference text pgs. 378-386 On the Origin of Species With a myriad of thoughts, ideas, and observations, Darwin began to gather his work into a single book published in 1859 called On the Origin of Species. He then began presenting evidence that evolution has been taking place for millions of years—and continues in all living things. What event motivated Darwin to publish his idea? ____________________ _______________________________________________________ Define “artificial selection.” ___________________________________ _______________________________________________________ _______________________________________________________ Suggest a reason why Darwin would think that artificial selection is important. _______________________________________________________ _______________________________________________________
Darwin explained that members of each species compete regularly to obtain food, living space, and other necessities of life.
He called this a _____________________________________________ The ability of an organism to survive and reproduce in its specific environment is called the __________________ of that organism. An _______________ is any inherited characteristic that increases an organism’s chance of survival or increases that animal’s _____________________________. What did Darwin mean when he described certain organisms as “more fit” than others? _______________________________________________________ _______________________________________________________ _______________________________________________________
Darwin proposed that over long periods, natural selection produces organisms that have
different structures, establish different niches, or occupy different habitats. Because of
this, species today look different from their ancestors. Given enough time, the new
species can look radically different from their ancestors.
Each living species has ______________________, with changes, from other species
over time. He referred to this principle as ______________________________________
Given enough time this also implies that all living things are related to one another and
that they share a ____________________________________.
All species—living and extinct— were derived from a common ancestor. What links all
living things together is a single ____________________________________.
Evidence of Evolution
Darwin used four lines of evidence to argue that living things have been evolving on
Earth for millions of years.
**Be sure to read the Summary of Darwin’s Theory on page 386**
Geographical distribution. How can two species that look very similar to each other live in such different locations?
Homologous structures suggest a common ancestor. The limbs have different functions but a similar bone structure. Refer to the colour diagram like this in your textbook. “Evolution lies exposed in the imperfections that record a history of common descent. Why should a rat run, a bat fly, a porpoise swim, and I type this essay with structures built of the same bones unless we all inherited them from a common ancestor?”
- Stephen Jay Gould, 1982.
Ever wonder why whales and snakes have hip bones? Do chickens have teeth? Of course not, but why do they have the gene for the production of tooth dentin? Why do we have wisdom teeth (third molars) when their only purpose seems to be to crowd out our other teeth? Why do males have nipples? Why do we all have muscles attached to our ears? These and many more are vestigial structures—which are remnants of our evolutionary heritage from the past. Evolution doesn’t re-invent structures and organs from scratch, it takes those same structures and “tinkers” with them to see how successful any changes would be in a new untested environment.
Shared genes with many other mammals show our evolutionary connectedness.
Embryology Embryologists study the development of embryos from different species. There is striking similarity in the develop- ment of similar species. We understand that this similarity is due to these organisms having similar genes. Their differ- ences result from the timing that these genes turn on and off, as well as even how long they remain turned on. This similarity in genes is due to the fact that we share a common ancestor. This provides further evidence to explain how evolution occurs.
This is a human embryo at a stage of its development called a blastocyst. There is no differentiation or specialization of cells at this point of development. Similar genes in similar organisms cause certain cells to develop in predictable ways. The timing of these genes can determine the shape and make-up of these structures.
This is a tubal (ectopic) pregnancy of a human embryo at about 6 weeks of development. You can see limb-buds, eyes, and the beginnings of a backbone.
Relative and Absolute Dating of Fossils With the advancement of techniques and technologies in science, we are afforded the luxury of discovering new evidence to add to the mountain of evidence for evolution: Reference text pages 417-428 Scientists who study fossils are called _____________________________. Using fossils, paleontologists can infer a wondrous array of information about the organism such as, what they ate, what ate them, what their environment was like and even their growth rate. They group similar organisms together and arrange them in the order in which they lived—from oldest to most recent. All this information about past life is called the____________________________. The fossil record reveals a remarkable fact, fossils occur in a particular ___________. The fossil record shows that ______________________________________________
To interpret the evidence presented by fossils, scientists use two different dating techniques. Relative and absolute dating techniques are summarized below:
What assumption do paleontologists make when they use relative dating to estimate the age of fossils? _______________________________________________________ _______________________________________________________
The question about how life on Earth started is not within the scope of evolutionary theory. Scientists have gathered evidence that leaves some very telling clues as to the mystery of how life may have begun on Earth. Atoms and molecules do not form compounds in a random manner as many people might suspect. They follow strict rules as to which atoms can form bonds together under the correct conditions. There are several reasons why atoms do not assemble themselves into complex organic molecules or living cells on Earth today. One reason is that our atmosphere today contains large amounts of __________________ which would destroy most organic molecules not protected within a cell. In the 1950’s, chemists __________________ and __________________ produced amino acids which are the building blocks of protein by passing sparks through a mixture of H2, CH4, NH3, and water. Although they did NOT create_______________ they did show that experimentally under the right conditions, the building blocks of all living things could be made.
Fill in the diagram above explaining the Miller-Urey experiment.
Life’s Origins Life from non-life remains one of the largest gaps in scientific hypotheses as to how it all began. Again, biologists see very compelling clues in nature today that provide us with insight into how life may have started. Under certain conditions, large organic molecules can form tiny bubbles called ____________________________________. Although they are not cells, they do have a very simple .
Theses tiny microspheres can contain extremely high concentrations of organic material (which is the building blocks of life). The spheres even contain lipid membranes similar to cell membranes.
The RNA World You remember from the first unit that RNA is a smaller, simpler molecule than DNA. Scientists were surprised to discover that RNA can actually act like an enzyme to help it make copies of itself and forge some very simple proteins. It has been hypothesized that RNA might have existed before DNA and that this simple molecule evolved into the more complex and efficient molecule of DNA that all life forms share today.
The Endosymbiont Hypothesis Given the evidence that life presents us we can visualize how life may have started. An even greater challenge occurs when we began to wonder how simple prokaryotic cells could become the complex eukaryotic cells complete with organelles. Convincing evidence today shows us that about 2 billion years ago, prokaryotic cells began to evolve internal cell membranes. Other prokaryotic organisms entered into these cells and began living as they were surrounded by membrane. Over time, a_________________________ relationship developed. This became known as the ________________________ theory. Eukaryotic cells formed from a symbiosis among several different prokaryotic organisms living together. One prokaryotic organism could generate ATP and evolved into a __________________ while another prokaryote cell that carried out photosynthesis evolved into the _______________________ found in plant cells today.
Label the following diagram to explain the ENDOSYMBIONT HYPOTHESIS
It is interesting to note that the internal structure of chloroplasts and mitochondria look very similar to these types of prokaryotic bacteria. Chloroplasts and mitochondria continue to have their own separate and unique DNA from the rest of the DNA in your cell’s nucleus.
Genetics The Study of Heredity
It is very interesting to note that as Charles Darwin was deriving his monumental ideas on Evolution and Natural Selection, he did not know of a reason for inherited traits. Gregor Mendel (the father of modern genetics) was devising his principles of genetics at the same time.
Characteristics appear to be repeated from generation to generation. The passing of traits from parents to offspring is called heredity. Your biological traits are controlled by genes located on chromosomes that are found in every cell of your body. You inherited half of your 46 chromosomes from your mother and the other 23 from your father. Essential Terminology 1. Chromosomes, Chromatids, Centromere and Homologous chromosomes A chromosome is a long DNA molecule containing many genes. In eukaryotes, it is associated with protein. During metaphase, the chromosomal material has duplicated itself and the two new halves are called “sister chromatids”. They are joined at the centromere and the centromere is attached to the spindle. A homologous chromosome is the matching chromosome inherited from the second parent.
It is important to note that if the top paternal and maternal strands are both called individual chromosomes, then when they duplicate below to form sister chromatids, each of the new duplicated paternal and maternal double strands are now considered to be only a single chromosome.
Homologous chromosomes contain the same genes. For example, the gene for eye colour would be found on both the paternal and the maternal chromosome. That’s what homologous means—there are two chromosomes that have the same genes, one from mother and the other from father. An important point to remember is that even though there are two copies of a single gene, they may be different versions of that gene. We call these different versions of the same gene alleles. There might be the allele for green eyes, blue eyes or brown eyes present on a chromosome but it’s still the gene for eye colour. Which allele an offspring inherits is completely random.
2. Genes Genes are units of nucleotide base pairs located on the chromosome, which provide instructions to a cell to produce a specific trait. You have about 20,00 genes (i.e. the gene for hair colour). Many genes can interact with other genes to produce various effects. 3. Alleles Alleles are two or more alternate forms of a gene. (i.e. an allele for black hair or blonde hair are forms of the gene for hair colour). 4. Dominant genes (alleles These genes (or alleles) determine the expression (the way you look) of the genetic trait. We represent dominant alleles with capital letters. 5. Recessive genes (alleles) These alleles are masked by the dominant alleles and are not expressed (do not show up). We represent recessive alleles with lower case letters. 6. Genotype Genotype refers to the genes (represented by letter combinations) of a trait for an organism. eg. BB or Bb 7. Phenotype Phenotype refers to the physical appearance of the traits in an organism. It tells us how the genotype actually looks like. i.e. Blue eyes, green eyes, curly hair. 8. Homozygous Homozygous refers to a genotype in which both genes of a pair are identical (i.e. RR, aa) 9. Heterozygous Heterozygous refers to a genotype in which the gene pairs are different (i.e. Rr, Aa) 10. Incomplete dominance When two alleles interact and are equally dominant, they produce a new phenotype, which is a blending of the two traits. (i.e. a red flower makes a pink flower when crossed with a white flower.) 11. Codominance Both genes are expressed at the same time producing a mottled effect. (eg. Red and white flowers make flowers with red and white specks)
All of your body cells contain a full complement of 46 chromosomes. (23 pairs) These cells are referred to as somatic cells. The male sperm cell or the female ova (egg) are called gamete cells and are the only cells to contain only ½ of this number. A gene for a particular trait can be found on one of your chromosomes. Different versions of the same gene are called alleles. Chromosomes come in pairs with matching alleles for a gene (one from mom and one from dad). During the formation of gametes (sperm or egg) the chromosomes that have similar alleles will segregate (separate). This ensures that each gamete cell has only one copy of the allele for that trait. Due to this segregation, a male’s sperm cell may contain the allele for blue eyes while another of his sperm cells may carry the allele for brown eyes. Both gametes carry the gene for eye colour and both gametes have only one allele (form) of the gene. When fertilization is complete, the first somatic cell is created. This cell is called a zygote. The zygote has 46 chromosomes in 23 pairs. Monohybrid Crosses
Go and observe the Chart called “GENETICS II” at the front of the class. The Law of Segregation is crucial to understanding how organisms can inherit alleles. The Law of Segregation states that This law ensures that each haploid cell (sperm or egg) has one copy of every gene (alleles). Together they form the first diploid cell in the offspring, which has two copies of every gene. Genetic crosses that involve the study of only one trait, such as seed colour, are called one-factor crosses because we are working out the possible genetics for only one factor. Use the letter from the chart below for the expression of the dominant and recessive alleles for the genes controlling these traits.
TRAIT DOMINANT ALLELE RECESSIVE ALLELE Pod shape Smooth (N) Constricted (n) Pod Colour Green (G) Yellow (g)
Flower Position Axial (A) Terminal (a) Plant height Tall (T) Short (t)
For each of the following problems, use the Punnett square and the chart on page 22 to answer the following Example: A plant that is heterozygous for green pods is crossed with a plant that has yellow pods. What are the probably genotypic and phenotypic ratios in the offspring? Answer: draw a Punnett square and use the letter combinations in the above chart:
G g g Gg gg
With the Punnett square complete, you can now determine the phenotypes of the offspring: Since green (G) is dominant over yellow (g), plants that have G in their genotypes have green pods. Only plants with genotype gg have yellow pods. In this example, 1 out of 2 of the offspring have green pods and 1 out of 2 have yellow pods. In this example, the genotypic ratio is 2 Gg: 2 gg or simply reduced to 1:1. The phenotypic ratio is 2 green: 2 yellow or simply again 1:1. Always reduce the ratios to their simplest form. For each of the following problems draw a Punnett square and check your work up at the front desk: 1. Nn x NN
Genotypic ratio: Phenotypic ratio:
2. Aa x aa
Genotypic ratio: Phenotypic ratio:
3. Tt x Tt
Genotypic ratio: Phenotypic ratio:
4. Show a cross for two plants that are heterozygous for green pods.
Genotypic ratio: Phenotypic ratio:
5. Cross a plant that is heterozygous for axial flowers with a plant that has
Genotypic ratio: Phenotypic ratio:
6. Cross a homozygous tall plant with a short plant.
Genotypic ratio: Phenotypic ratio:
7. Cross a plant that is heterozygous for smooth pods with a plant that has
Genotypic ratio: Phenotypic ratio:
8. When a tall plant is crossed with a short plant, some of the offspring are short.
What are the genotypes of the parents and the F1 generation? What is the phenotypic ratio of the F1?
9. ¾ of the plants produced by a cross between two unknown pea plants have
axial flowers and ¼ have terminal flowers. What are the parent plant genotypes?
10. What cross would result in ½ of the offspring having green pods and ½ of the
offspring having yellow pods?
Dihybrid Crosses Crosses that involve two traits, such as pod colour and pod shape, are called dihybrid crosses or sometimes (two-factor crosses). Predicting the outcome of these crosses requires basically the same procedure as that for single factor crosses. Keep in mind that in dihybrid crosses, the genes controlling the two different traits are located on nonhomologous chromosomes. During meiosis, nonhomologous chromosomes assort independently. This means that each of the chromosomes of any pair of homologous chromosomes has an equal probability of ending up in a gamete with either chromosome from any other pair of homologous chromosomes. The genes that are located on nonhomologous chromosomes also assort independently as you can see below: Because of independent assortment, a plant that is heterozygous for two traits (genotype AaBb) will produce equal numbers of four types of gametes – AB, Ab,aB, and ab. In the example that follows, we will predict the results of a cross between two plants that are heterozygous for both pod colour and pod shape. Example: What are the genotypic and phenotypic ratios in the F1 resulting from a cross between two pea plants that are heterozygous for pod colour and pod shape? What is the phenotype of the parents in this cross? Answer: choose letters to represent the alleles in the cross and write the letters of the parent genotypes. GgNn x GgNn Determine the possible gametes that the parents can produce. Independently assorted, there would be four possible types… GN, Gn, gN, and gn. Enter the possible gametes at the top and side of a Punnett square and complete the F1 generation.
GgNn x GgNn
The phenotypic ratio is 9:3:3:1.There are 9 green smooth to 3 green constricted to 3 yellow smooth to 1 yellow constricted. In mice, the ability to run normally is a dominant trait. Mice with this trait are called running mice (R). The recessive trait causes mice to run in circles only. Mice with this trait are called waltzing mice (r). Hair colour is also inherited in mice. Black hair (B) is dominant over brown hair (b). For each of the following problems, draw a Punnett square to answer the following: 1. Cross a heterozygous running, heterozygous black mouse with a homozygous running, homozygous black mouse. Identify the phenotypic ratio.
2. Cross a homozygous running, homozygous black mouse with a heterozygous running, brown mouse. Identify the phenotypic ratio.
3. Cross a waltzing brown mouse with a waltzing brown mouse. Identify the phenotypic ratio.
4. Cross a homozygous running, heterozygous black mouse with a waltzing brown mouse. Identify the phenotypic ratio.
5. Cross a heterozygous running, brown mouse with a heterozygous running, homozygous black mouse. Identify the phenotypic ratio.
Many genes have more than two alleles and are called multiple alleles. This does not mean that an individual can have more than two alleles. It only means that more than two possible alleles exist in a population. Many traits are produced by the interaction of several genes. Traits controlled by two or more genes are said to be polygenic traits, which means “having many genes.” Human skin colour comes about partly due to the fact that there are four different genes controlling this trait. Use text reference page312
When many genes are involved, regulating them is especially important in shaping the way a complex organism develops. Each of the ____________ types found in the adult develops from the same fertilized egg cell. Cells don’t just grow and divide during embryonic development; they also undergo __________________ which means they become specialized in structure and function. A series of genes known as ______________ genes control the differentiation of cells and tissues in the embryo. Any change in the hox genes can completely change the organs that develop in a particular part of the body. It was even learned years later that hox genes are interchangeable with two different organisms.
Evolution of Populations Reference text pages: 393-409 How Common is Genetic Variation? We know that many genes have at least two forms or alleles. Most fishes, reptiles and mammals are typically heterozygous for between 4 and 8 % of their genes. A gene pool is considered _____________________________________ ___________________________________________. The ______________________________________ of an allele is the number of times that the allele occurs in a gene pool compared to with the number of times other alleles for the same gene occur. Gene pools are important to evolutionary theory, because evolution involves ____________________________________________. In genetic terms, evolution is ___________________________________ ___________________________________________________ Heritable variation comes from two main sources: 1. ______________________________ 2. ______________________________ Heritable variation can be expressed in a variety of ways. The number of phenotypes for a given trait depends on how many genes control the trait. When more than a single gene controls a trait, it is called a polygenic trait. Human height is an example of a polygenic trait. Because there are many alleles controlling height, there are many different genotypes and phenotypes.
Normal distribution graph. This graph shows the various heights for a population of people. 5’8” is the average height for this population and coincidently has the greatest number of individuals. We would expect less numbers of really short and really tall individuals.
Evolution as Genetic Change Evolution in a population can occur in two main ways: 1. Natural Selection Natural Selection can act to affect phenotypes in a population in three distinct ways:
Directional Selection text reference pg. 398
Directional Selection above occurs when individuals at one end of the curve have higher “fitness” than individuals in the middle or at the other end. The graph above on the left shows a “Normal Distribution Graph” for beak size in seed-eating finches. The Environment favors average sized beaks due to the fact that most of the seeds are of average size. There are very few small seeds and very few large seeds, so it is not surprising to see that the graph shows that there are also not a lot of finches with small or large beaks. When a food shortage occurs causing the supply of small seeds to run very low we expect Directional Selection to occur in the population of finches. The range of phenotypes will shift in the direction of greatest fitness in a population over time as the graph on the top right shows. Describe the kind of environment needed for the finches to experience Directional Selection of this kind: _______________________________________________________ _______________________________________________________
Stabilizing Selection text reference pg. 399
Stabilizing Selection occurs when individuals near the centre of the curve (average phenotypes) have higher fitness than individuals at either end of the curve.
An example of Stabilizing Selection can be found when observing human birth weights. If the fitness of phenotypes at both ends of the curve were to decrease even more, how would it affect the shape of the curve above? _______________________________________________________ If medical advances could prevent problems for high birth weight babies but not for low weight birth babies, how might the curve change then? _______________________________________________________ What kind of “Selection” might this represent then? __________________________________
Disruptive Selection occurs when individuals at both ends of the curve have higher fitness than individuals near the middle of the curve. In this example, average-sized seeds become less common, and larger and smaller seeds become more common. This has an effect on the size of the beaks that begin to show up in the population over time. As a result, the bird population splits into two subgroups specializing in eating different-sized seeds. What do you think might happen if these two separate groups remained “split” for hundreds of generations and then they were re-introduced to each other? _______________________________________________________ _______________________________________________________ _______________________________________________________
2. Genetic Drift This is evolution by ____________________. When a small sample of individuals separate from the original population, they might begin their own population in a new location with their own different allele frequency from the original population. This is commonly referred to as the .
The Hardy-Weinberg Principle To help biologists understand how evolution works, it is often useful to ask if there are any conditions under which evolution will NOT occur. The Hardy-Weinberg principle states that ________________________ _________________________ will remain constant unless one or more factors cause a change. When allele frequencies remain constant, a state of __________________ is reached and the population will NOT evolve. Five conditions are required to maintain genetic equilibrium from generation to generation:
The Process of Speciation Reference text pg. 404-410 This is a summary of the process of Speciation. Fill in the missing ovals after reading the reference pages from your text.
Developmental Genes and Body Plans Reference text pg. 440 Biologists have long suspected that changes in genes during embryological development could produce drastic transformations in body plans of organisms. By turning on and off the “master control genes” called hox genes we have seen various changes occur. If one gene called “wingless” is turned on in an insect body segment, that segment grows no wings. This is interesting because some ancient insects had wing-like structures on all body segments. Modern insects today have wings on only one or two segments. Small changes in the timing of cell differentiation and gene expression can make the difference between chimpanzee brains and human brains!
The process of Speciation occurs over long periods of time. It has been directly observed and studied by the now famous study of the Galapagos finches by Peter and Rosemary Grant. There are many other incidences of documented observable change.
This is an example of Adaptive Radiation (which is sometimes called Divergent Evolution)
Macroevolution Reference text pgs.435-440 Biologist will often use the term macroevolution to refer to large-scale evolutionary patterns and processes that occur over long periods of time. Six topics in macroevolution are extinction, adaptive radiation, convergent evolution, coevolution, punctuated equilibrium and changes in developmental genes. Fill in the following chart summarizing five of the six major topics in macroevolution
What is the difference between Punctuated Equilibrium and Gradualism? _______________________________________________________ _______________________________________________________
_______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________
OBJECTIVE SHEET TAXONOMY 1. Construct and use dichotomous keys to identify organisms.
2. Define “scientific name” and the binomial system of nomenclature. 3. Name and describe the general characteristics of each of the five most
common Kingdoms. 4. Describe how biologists group organisms based on Phylogeny (lines of
evolutionary descent). 5. Construct a cladogram based on derived characteristics. 6. Discus how similarities in DNA and RNA as well as the use of Molecular
Clocks aids in the development of more accurate Phylogenies. 7. Explain the Modern classification of Organisms by identifying the
characteristics of the Three-Domain System. 8. Classify a human being using Taxons
Above is a cladogram showing the evolutionary relationships of dinosaurs leading to modern day birds. Constructing a cladogram helps biologists organize
the fossil record to show their evolutionary relationships to modern day organisms.
Reference pgs. 447-450 A scientific discipline known as _____________________ allows scientists to classify organisms and assign them a universally accepted name. Advantages of Classification By organizing life into groups, biologists can communicate with each other around the world. The advantages of classification include:
1. Biologists can study the diversity of life with Biological meaning. 2. A name can be recognized by all scientists regardless of language barriers. 3. Newly discovered organisms can be understood better by making
comparisons to existing groups. These comparisons can shed light on the evolutionary ancestory of the organism.
4. Classification allows biologists to get a more complete picture of how life evolved on the planet and how this affects the current trends of life on the today’s planet.
LINNAEUS’S HIERARCHIAL CLASSIFICATION Carolus Linnaeus (1707-1778) devised a system to put into the diversity of life. He started the science of taxonomy. First he assigned each species a scientific name composed of two names = binomial nomenclature. Each name is made up of the genus and species name in Latin. Sometimes a third name is included to give credit to the discoverer. Secondly, he adopted a filing system for grouping species into a hierarchy of increasingly general categories. Although, he used only three categories (one in bold), we commonly use all the ones below: KINGDOM
The purpose of taxonomy (the identification and classification of species) is to: Sort out closely related organisms and assign them to separate species, describing the characteristics that distinguish one species from another. Each taxonomic category from Kingdom all the way to species is called a
The Kingdom taxon contains the greatest number of organisms as it is the least specific while the species taxon is the most specific. The “Species” designation is the only taxon that occurs “naturally”. Organisms decide for themselves whom they want to reproduce to make offspring with under natural conditions.
The Old Five Kingdom System A five kingdom classification system was introduced in which all living things can fit into, based on their complexity and the methods by which their nutritional needs are met. KINGDOM CHARACTERISTICS _______________________________________________________ Monera Bacteria and Cyanobacteria- All monerans are single-celled. Unlike other cells, the monerans lack a nucleus, and other organelles. They are all prokaryotic. Protista Ameba, Euglena, Paramecia – Protists are mainly unicellular organisms that have a membrane-bound nucleus and many other organelles. Some are colonial and multicellular. All protists are eukaryotic. Fungi Mushrooms, water mole, bread mold – fungi are non-motile and cannot photosynthesize. They are heterotrophic as they absorb nutrients from a living or non-living source. Fungi differ from plants in the way the cell wall is made, in their method of reproduction, and even in their body structure. Plantae Includes the mosses, ferns, grasses, shrubs, flowering plants
and trees – most photosynthesize and contain chloroplasts. All plant cells have a membrane-enclosed nucleus and cell walls that contain a substance called cellulose.
Animalia All members of the animal kingdom are multicellular. The
cells have a discrete nucleus that contains chromosomes. Most animals can move and depend on organic materials for food. Excluding the very simple species, most animals reproduce by means of gametes called egg and sperm cells.
_______________________________________________________ Archetista Viruses – although not living and acellular, the structure of
viruses can evolve to produce drastic changes. Viruses have a protein coat surrounding either DNA or RNA.
This sixth kingdom is sometimes used for convenience. Linnaeus’s system is still used today but it has its limitations. Using Linnaeus’s system of taxons, taxonomists have always tried to group organisms according to biologically important characteristics. But which similarities and differences are most important? Linnaeus’s system has limitations and problems although it is still widely used in biology today.
Phylogeny By using Darwin’s ideas about descent with modification, taxonomists can now group organisms into categories that represent lines of evolutionary descent, or phylogeny, not just physical similarities.
A phylogeny is a description of the history of descent of a group of organisms from their common ancestor. Groups of evolutionarily related species are represented as related branches in a phylogenetic tree, or a cladogram. A group of species that consists of all the evolutionary descendants of a common ancestor is called a clade. Named clades and species are called taxa.
How do biologists use phylogenetic trees?
A derived trait is one that differs from its form in the common ancestor of a lineage. A node on a tree indicates a derived feature. Biologists can use phylogenetic trees to reconstruct ancestral states. Phylogenetic trees may include estimates of times of divergence of lineages, as determined by a molecular clock analysis.
Phylogenetic trees are used to reconstruct the past and understand the origin of traits. Phylogenetic trees are used to make appropriate evolutionary comparisons among living organisms. They can sometimes be used to even predict future evolution. A phylogenetic tree is divided into the following types of groups:
The cladogram below shows the phylogenetic relationships among 6 species labeled (A-F). Use the three groups to match its position on the cladogram.
Well known Paraphyletic Groups: The class Reptilia as traditionally defined, are paraphyletic because it excludes birds (class Aves) and mammals (class Mammalia). Using Linneaus’ system, the three taxa are classes of equal rank. However, mammals hail from the mammal-like reptiles and birds are descended from the dinosaurs (a group of Diapsida), both of which are classified as reptiles. Reptiles would be monophyletic if they were defined to include Mammalia and Aves. The prokaryotes (single-celled life forms without cell nuclei), are paraphyletic because they exclude the eukaryotes, a descendant group. Bacteria and Archaea are prokaryotes, but archaea and eukaryotes share a common ancestor that is not ancestral to the bacteria.
Read page 452 in your text. List the ways that barnacles and limpets are different from each other. _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ List several reasons why we think that barnacles and crabs share a more recent common ancestor than the ancestor that barnacles share with limpets? _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ The table below right shows the ancestral and derived states of 5 traits (a through e) for 6 species. For each box in the cladogram, write in a number (1-6) to indicate where that species should be positioned in the cladogram. Note: circles in the cladogram show where specific derived traits appeared. (-) = ancestral state, (+) = derived state
Found within the genetic code of all organisms is DNA. This provides us with an excellent way of comparing organisms at their most basic level – their genes. Scientists can sequence or “read” the information coded in DNA and can compare the genetic similarities amongst organisms to trace the history of their genes over millions of years. The more similar the DNA sequences of two species, the more recently they shared a common ancestor, and the more they are related in evolutionary terms. A cladogram helps biologists understand how one lineage branched from another in the course of evolution.
Molecular clocks allow biologists to make more accurate phylogenetic trees. Simple mutations occur all the time causing slight changes in the DNA structure. Some mutations have positive or negative effects on the phenotype of an organism. Many mutations have no effect at all. These neutral mutations accumulate in the DNA of different species at about the same rate. Comparing such DNA sequences in two species can reveal how dissimilar the genes are and thus provide an indication of how long ago the two species shared a common ancestor. Some genes accumulate mutations faster than others so biologists can time different kinds of evolutionary events, each of which “ticks” at a different rate. What evidence indicates that Species C is more closely related to Species B than to Species A? _____________________________________ _____________________________________
Reference pgs. 458-461 The Three-Domain System Using the molecular clock model, scientists have grouped modern organisms according to how long they have been evolving independently. The modern day method of classification includes a new taxon called a domain. The three domains are the domain Bacteria, domain Archaea, and domain Eukarya. List the characteristics that distinguish members of the domain Bacteria from members of the domain Archaea. _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ Fill in the missing parts of the chart below as you study the features of each domain:
Complete the summary of “Living Things” below:
Use the colour diagram in your text pg.460-61 to indicate the name of each Domain in the diagram. You may want to use colour to hi-lite each domain.
ACROSS 1. eventually exposes recessive genes to the environment for 3. red hair, blue eyes, etc. 4. kingdom with prokaryotic members 8. many different phyla are grouped into one ________ 10. individuals that can interbreed belong to the same _________ 11. an alternate form of a gene, (B or b) 12. to change with time 13. similar looking structure, but suggest evolution along different lineage. 14. according to Lamarck, these can be passed on. 19. wing of a bird and the arm of a person are said to be __________ 21. tried to support Oparin’s hypothesis 22. kingdom characterized by being non photosynthetic and getting nutrition by absorption 23. many different genus may belong to the same ___________ 24. traits that are present before they are useful.
DOWN 2. believed that variations are the raw material for evolution 3 a random change in DNA that turns out to be helpful 5 type of evolution that results in birds and bats having wings (put “N” and “V” in the same box) 6 most always results in a well adapted individual reflected in its offspring 7 governs one trait 9 appendix, coccyx, dentin in chickens are said to be ___________ 15 Bbtt x BBTt 16 a questionable scientific name 17 a trait that must be present in a homozygous condition to show up 18 the science of classification 20 kingdom characterized by nutrition by ingestion, multicellular and eukaryotic
Why You Are Homo sapiens
1. At present there are six generally recognized kingdoms of organisms and three domains. Since human cells have discrete nuclei surrounded by a nuclear membrane, you belong to the domain Eukarya. Your cells lack chloroplasts and cell walls , and you are a multicellular heterotroph, with highly differentiated tissues and organ systems. That makes you a member of the kingdom Animalia.
2. What kind of animal are you? You possess a spinal column composed of bony vertebrae that has
largely replaced a cartilaginous rod you had as an embryo, the notochord. At that time you also had structures that had you been a fish would have developed into gill slits. You have a dorsal nerve cord and brain. These traits mark you out as a chordate and a vertebrate that is, you belong to the phylum Chordata (because you either have or have had a notochord) and to the subphylum Vertebrata (because you have vertebrae that replaced the softer notochord)
3. Among the vertebrates there are several classes: cartilaginous fish, bony fish, jawless fish, amphibia,
reptiles, mammals and birds. You are homeothermic (warm blooded) and so must be either a bird or a mammal. Lacking feathers and having teeth and (if you are female) the potential for nursing your young you are of the class Mammalia. If you are male, do not be concerned; even if you cannot nurse, having hair is enough.
4. A number of orders exist within the classes. The Insectivores, for instance, include the moles and
shrews, the Chiroptera are the bats, and the Carnivora include dogs, cats, and ferrets among others. Your opposablethumbs, frontally directed eyes, flat fingernails, and other characteristics identify you as the order Primate, along with monkeys, apes and tarsiers.
5. Primates include a number of families. You and the New World monkeys (Western hemisphere) are obviously very different – they have prehensile tails, for instance, which you and all Old World monkeys (Eastern hemisphere) and apes lack: indeed, you and the apes lack tails altogether. Your posture is upright, you have long legs and short arms, and not much body hair. You are blessed with your very own family with no other occupants: family Hominidae.
6. Within the Hominidae, anthropologists distinguish several species, all but one of which are known
only as fossils. Australopithecus is one of these. If you are alive, you do not belong to any of those extinct genera, but to the genus Homo.
7. Again, the genus Homo has only one living species called sapiens. Since many taxonomists insist
that the species name always includes the genus name, (binomial nomenclature) please think of yourself as Homo sapiens.