Survival of Organisms and the history of life 2014 Engel Super Science Savers™ Name________________________ Hour__ Due date 10/20/2014 The history of life starts with the Earth forming 4.6 billion years ago, the solid surface forms 4 billion years ago. Our best evidence shows life starts 3.8 billion years ago with the age of Bacteria.

In 1966, microbiologist Kwang Jeon was studying single-celled organisms called amoebae, when his amoebae communities were struck by an unexpected plague: a bacterial infection. Literally thousands of the tiny invaders named x-bacteria by Jeon, squeezed inside each amoeba cell, causing the cell to become dangerously sick. Only a few amoebae survived the epidemic. However, several months later, the few surviving amoebae and their descendants seemed to be unexpectedly healthy. Had the amoebae finally managed to fight off the x-bacterial infection? Jeon and his colleagues were surprised to find that the answer was no — the x-bacteria were still thriving inside their amoebae hosts, but they no longer made the amoebae sick. There were more surprises when Jeon used antibiotics to kill the bacteria inside an amoeba — the host amoeba also died! The amoebae could no longer live without their former attackers. Jeon discovered that this was because the bacteria make a protein that the amoebae need to survive. The nature of the relationship between the two species had changed entirely: from attack and defense to cooperation. Jeon's colonies of amoebae seem perfectly happy living with their permanent guests, the x-bacteria, inside of them. This kind of relationship — two or more different species living in close association — is called symbiosis. Evidence

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like this points to the likelihood that the "merging" of two simple organisms has also happened under natural conditions. Long ago in evolutionary history, two cells formed a symbiotic team that, over millions of years, evolved into a single organism. The result of this union was the first eukaryotic cell — the type of cell that makes up the human body. We humans owe our existence to two bacteria that teamed up in a symbiotic relationship over a billion years ago! Although Jeon watched his amoebae become infected with the x-bacteria and then evolve to depend upon them, no one was around over a billion years ago to observe the events of endosymbiosis. Why should we think that a mitochondrion used to be a free-living organism in its own right? It turns out that many lines of evidence support this idea. Most important are the many similarities between

prokaryotes (like bacteria) and mitochondria:

● Membranes — Mitochondria have their own cell membranes, just like a prokaryotic cell does.

● DNA — Each mitochondrion has its own circular DNA genome, like a bacteria's genome, but much smaller. This DNA is passed from a mitochondrion to its offspring and is separate from the "host" cell's

genome in the nucleus.

As DNA sequencing projects decode more genomes letter by letter, we are learning that eukaryotic "host" cells have a lot in common, genomically speaking, with the strangest, least-understood domain

of life: the Archaea. These prokaryotes went completely undiscovered until 1977 because they live in such extreme environments as Antarctica, the Dead Sea, deep-sea vents, hot springs,

and sewage sludge. Yet one of them may have been the first endosymbiotic host, and our own ancestor. Why have endosymbiosis and symbiosis been so important to survival of organisms? Why cooperate at all? The answer to these questions points us to one of the basic processes of survival: natural selection. As Darwin observed, organisms that are fit enough to succeed in the game of survival have a good chance of passing on their genes to the next generation. Any survival or reproductive advantage can help a species out-compete another species or simply avoid becoming extinct itself. It seems likely that the first eukaryotic cells gained a slight edge over their neighbors when the mitochondria, a rich source of energy, moved in with them. Like Kwang Jeon's x-bacteria and amoebae, the mitochondria and their hosts relied more and more on each other in order to survive. Eventually, neither could succeed alone — but as a team they produced millions of descendants, establishing a whole new branch of life.

The Father of Modern GeneticsGenetics began with a monk named Gregor Mendel working in the garden of a small monastery in what is now Slovenia. Mendel, whose parents were Austrian peasants, was born in 1822. He entered the monastery at the age of 21 and was ordained a priest 4 years later. In 1851, Mendel was sent to the University of Vienna to study science and

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mathematics. After he left the university, Mendel spent the next 14 years working at the monastery and teaching at a nearby high school. In addition to teaching, Mendel also looked after the monastery garden. He grew hundreds of pea plants. Mendel experimented with the pea plants to see if he could find a pattern in the way certain characteristics were handed down from one generation of pea plants to the next. Genetics http://dnaftb.org/dnaftb/ An animated primer of DNA and genetics basics- http://www.parentsplace.com/first9months/main.htmlBasic genetics http://www.ology.amnh.org/genetics/index.html- Smoking Hot Link! The gene scene

http://www.pbs.org/wgbh/aso/tryit/dna/# Genetic site- interactive http://www.ucmp.berkeley.edu/education/explorations/tours/intro/National science foundation site http://www.niehs.nih.gov/kids/redbug/home.htm

Mendel chose pea plants for his experiments for several reasons. Pea plants grow and reproduce quickly. So he knew that he could study many generations of pea plants in a short time. Mendel also knew that pea plants had a variety of different characteristics, or traits, that could be studied at the same time. Pea plant traits include how tall the plants grow, the color of their seeds, and the shape of their seeds. Mendel could study all of these traits (as well as other traits) in the same experiment.

In addition, pea plants could be crossed, or bred, easily. The flowers of pea plants contain stamens, or male reproductive structures. Stamens produce pollen, which contains male sex cells, or sperm cells. The flowers also

contain the female reproductive structure, called the pistil. The pistil produces the female sex cell, or egg cell. When pollen lands on top of the pistil of a flower, pollination occurs. Pollination produces seeds for the next generation of pea plants. Usually, a pea plant pollinates itself. This type of pollination is known as self-pollination. In self-pollination, pollen from the stamen of one flower lands on the pistil of the same flower or on the pistil of a different flower on the same plant. Mendel found that he could transfer pollen from the stamen of one flower to the pistil of another flower on a different plant. This type of pollination is known as cross-pollination. By using cross-pollination, Mendel was able to cross pea plants with different traits. Although Mendel did not realize it at the time, his experiments would come to be considered the beginning of the science

of genetics (juh-NEHT-ihks). For this reason, Mendel is called the Father of Genetics. Genetics is the study of heredity, or the passing on of traits from an organism to its offspring. Mendel began his experiments by first crossing two short pea plants (pea plants with short stems). He discovered that when he planted the seeds from these pea plants with short stems, only short-stemmed plants grew. In other words, members of the next generation of short-stemmed plants were also short-stemmed. This result was what he, and everyone else at that time, expected. New generations of plants always resembled the parent plants. Mendel called these short plants true-breeding plants. By true-breeding plants, Mendel meant those plants that always produce offspring with the same traits as the parents. In the experiments that followed, Mendel tried crossing two tall pea plants (pea plants with long stems). He wondered if the tall pea plants would also be true breeding. To his surprise, he found that tall pea plants would not always be true breeding. Some tall pea plants produced all tall plants. However, other tall pea plants produced mostly tall and some short pea plants. This result was different from the cross between the short pea plants, which produced only short plants. Although he could not explain his results at the time, Mendel realized that there must be two kinds of tall pea plants: true-breeding plants and plants that did not breed true.

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Mendel wondered what would happen if he took pollen from a plant that produced only tall plants (a true-breeding plant) and dusted it onto the pistil of a short plant (another true-breeding plant). To identify the different generations of plants Mendel gave them different names. He called the first two parent plants the parental generation, or P generation. He called the offspring of the P generation the first filial (FIH-ee-uhl) generation, or F1 generation. (The word filial comes from the Latin word filius, which means son.) Mendel discovered that all of the plants in the F1 generation were tall. There were no short plants at all! It was as if the trait for shortness from one of the parent plants had disappeared completely. Mendel could not explain these results either.

What happened next was even more of a mystery. Mendel covered the tall plants of the F1 generation and allowed them to self-pollinate. That is, the pollen of a flower was allowed to fall onto the pistil of the same flower. Mendel expected that the tall plants would again produce only tall plants. But once again he was surprised. Mendel discovered

From the careful records he kept from all of his experiments, Mendel made several important discoveries. He observed that the tall plants of the F1 generation did not breed true. So he reasoned that these plants had to contain factors for both tallness and shortness. When both factors were present in a plant, only tallness showed. These factors which Mendel called 'characters" are now called genes. Genes are the units of heredity. From his observations, Mendel also concluded that when he crossed two true-breeding plants with opposite traits (Tallness and shortness, for example) the offspring plants showed only one of the traits (tallness). That trait seemed to be "stronger" than the other trait (shortness). The stronger trait is called the dominant trait. The "weaker" trait, or the trait that seemed to disappear, is called the recessive trait.

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Geneticists are scientists who study heredity. Symbols are used to represent different forms of a gene. A dominant form is represented by a capital letter. For example, the gene form for tallness in a pea plant is "A". A recessive form is represented by a small, or lowercase letter. Thus, shortness is "a". Every organism has two forms of the gene for each determined trait. So the symbol for a true-breeding tall plant is "AA". The symbol for a true-breeding short plant is "aa". One of the reasons Mendel chose pea plants for his experiments was that they showed a variety of different traits that could be studied at the same time. So in addition to height, or stem length, Mendel also studies seed shape, seed color, seed coat color, pod shape, pod color and flower position. For every trait studied, the results were always the same: Crossing two true breeding plants with opposite traits did not result in a mixture of traits. Only one of the traits, the dominant one appeared visible in the offspring. But in the next generation, the trait that seemed to disappear, the recessive one, reappeared yellow, but some are green. The recessive gene for green seeds reappears in the F2 generation. On organism that has genes that are alike for a particular trait, such as "YY" or "yy" is called a purebred. An organism that has genes that are different for a trait, such as "Yy" is called hybrid (HIGH bread). The plants with yellow seed in Mendel's F1 generation were hybrid plants (Yy). The plants were produced by crossing two purebred plants with opposite traits (YY and yy). Many of the plants advertised in seed catalogues are hybrids that were developed by plant breeders. Mendel's hypothesis was that each pea plant had a pair of factors, or genes, for each trait. Each parent pea plant could contribute only one gene of each pair to each plant in the next generation. In that way, each plant in the next generation also had a pair of genes for each trait, one from each of the parents. Now Mendel could account for the fact that a pea plant with green seeds can develop from a cross between parents with yellow seeds. The factor, or gene, for the green color must be present but hidden in the parents. For example, a parent with Yy genes would have yellow seeds because the dominant gene (Y) was present. But that parent would also be carrying the recessive gene (y) for green seeds. The green seed trait would be hidden in the parent but could be passed to its offspring.

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When the parent plant forms sex cells (sperm or egg), the parent gene pairs segregate, or separate. This process is known as the law of segregation. According to the law of segregation, one gene from each pair goes to each sex cell. Half of the sex cells of a hybrid pea plant with t he gene pair (Yy) have a gene for yellow seeds (y). The other half of the sex cells carries a gene for the green seed (Y). As a result of sexual reproduction, a male sperm cell (sperm) and a female sex cell (egg) unite to form a fertilized egg. Each fertilized egg contains one gene for seed color for each parent, so the gene pair for seed color is formed again.

Mendel also crossed pea plants that differed from one another by two or more traits. The result of these crosses led to the law of independent assortment. The law of independent assortment states that each gene pair for a trait is inherited independently of the gene pairs for all other traits. For example, when a tall plant with yellow seeds forms sex cells, the genes for stem length separate independently from the genes for seed color. Through the work of scientists such as Mendel, basic principles of genetics have been created. These basic ideas are traits, or characteristics, passed from one generation of organisms to the next generation. The traits of an organism are controlled by genes. Organisms inherit genes in pairs, one gene from each parent. Some genes are dominant, whereas other genes are recessive. Dominant genes hide recessive genes when an organism inherits both. Some genes are neither dominant nor recessive. The genes show incomplete dominance.

In one of Mendel's experiments, he crossed two plants that were hybrid for yellow seeds (Yy). When he examined the plants that resulted, he discovered that about one seed out of every four was green. By applying this concept of probability to his work, Mendel was able to express his observations mathematically. He could say that the probability of such a cross producing green seeds was 1/4 or 25%. Probability is the possibility or likelihood that a particular event will take place. Probability can be used to predict the results of genetics crosses.

Suppose that you are about to toss a coin. What are the chances that the coin will land heads up? If you said a 50 % chance, you are correct. What are the chances that the coin will land tails up? Again, the answer is 50%.

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Although you may not realize it, you, like Gregor Mendel, used the laws of probability to arrive at your answers. You figured out the chance or likelihood, that the coin would come up heads (or tails) on one toss.

A probability is usually written as a fraction or as a percentage. For example, the chance that a sex cell will receive a G gene from a parent with a Gg gene pair is 1/2 or 50%. In other words, you would expect one half, or 50 % percent, of the sex cells to receive a G gene. In probability, the results of one event do not affect the result of the next. Previous events do not affect future outcomes. Each event happens independently.

For example, suppose you toss a coin 10 times and it lands heads up each time. What is the probability that it will land heads up on the next toss? Because the coin landed heads up on t he previous 10 tosses, you might think that it is also likely to land heads up on the next toss. But this is not the case. The probability of the coin's landing heads up on the next toss is still 1/2 or 50 %. The results of the first 10 tosses do not influence the results of the eleventh toss.

In addition to the probability, a special chart called a Punnett square is used to show the possible gene combinations in a cross between two organisms. Reginald C. Punnett, and English geneticist developed this chart. Look at the Punnett Square above. It shows a cross between a male and female. The two possible genes in the male sex cells are listed along the left side. Remember, when a male sex cell (sperm) and a female sex cell (egg) join, a fertilized egg forms. Each box in the Punnett Square represents a possible gene pair in the fertilized egg forms.

CHECK FOR UNDERSTANDING

1. The male reproductive structures of pea plants are calleda. pistils b. petals c. stamens d. pollen

2. The symbol for a dominant gene is written asa. capital letter b. lower case letterc. a capital letter and a lower case letter d. two lower case letters

3. Who is called the Father of Genetics?a. Watson b. Mendel c. Washington d. Punnett

4. When Mendel crossed two short pea plants, the offspring werea. all short b. 1/2 short 1/2 tall c. all tall 3/4 tall and 1/4 short

5. Mendel studied all of the following pea traits excepta. stem length b. flower color c. seed color d. leaf color

6. Gene pair for a trait separate according to the law ofa. independent assortment b. incomplete dominancec. hybridization d. segregation

7. Which gene pair would a hybrid tall pea plant have?a. TT b. tt c. Tt d. none of these

8. The probability that a pea plant will receive a T gene from a Tt parent isa. 1/4 b. 3/4 c. 50 % d. 100 %

If the statement is true place the letter "T" in front of the statement. If the statement is false, change the underlined word to make the statement true.

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9. ___ One reason Mendel studied pea plants is that they grow and reproduce slowly.

10. ___ The pistil of the pea plant flower produces pollen.

11. ___ The process by which a plant pollinates itself is called cross-pollination.

12. ___ Mendel called plants that always produce offspring with the same traits as the parents true-breeding plants.

13. ___ Probability is usually expressed as a fraction or as a percentage.

14. ___ Scientists who study heredity are called plant breeders.

How are chromosomes passed on from parents to offspring? After all, if each parent contributed all of its chromosomes to an offspring, then the offspring would have twice as many chromosomes as its parents- twice the number of normal chromosomes. This does not happen because of a process called Meiosis (migh-oh-sihs).Cell function http://www.biology.arizona.edu/cell_bio/cell_bio.html Mitosis/Meiosis http://biologyinmotion.com/cell_division/index.html Mitosis/Meiosis http://www.ibiblio.org/virtualcell/index.htm Virtual cell http://www.eurekascience.com/ICanDoThat/

The process of Meiosis produces the sex cells, sperm or egg cells. Remember that according to the law of segregation, each of the organism's two genes for a particular trait are separated or segregated during the formation of

sex cells. This is precisely what happens during Meiosis. As a result of Meiosis, the number of chromosomes (and the genes they carry) in each sex cell is half the number of chromosomes found in the parent. When sex cells combine to form offspring, each sex cell contributes half the normal number of chromosomes. Thus, the offspring gets the normal number of chromosomes-half from each parent. The first thing that happens during meiosis is that the chromosomes in the cell double, producing eight chromosomes. The cell then divides. During the cell division, the chromosomes pairs separate and are equally distributed. So each of the two cells formed by this cell division has four chromosomes, the original number. Next, these two cells divide. Each of the resulting four cells now has two chromosomes. That is, each cell in the last group of cells produced

by meiosis has half the number of chromosomes as the original parent cell. In 1907, the American zoologist Thomas Hunt Morgan began his own studies in genetics. He experimented with tiny insects called fruit flies. You may have seen fruit flies hovering over the fruit and vegetables in a grocery store or supermarket. Morgan chose to study fruit flies for three reasons. First, fruit flies are easy to grow. Second, they produce new generations of offspring very quickly. Third, their body cells have only four pairs of chromosomes (eight chromosomes) making them easy to study. Morgan quickly discovered something strange about the fruit flies four pairs of chromosomes. In female fruit flies, the chromosomes of each pair were in the same shape. In males, however, the chromosomes of one pair were not the same shape. One chromosome of the pair was shaped like a rod and the other chromosome in the pair was shaped like a hook. Morgan called the rod-shaped chromosome the X chromosome and the hook-shaped chromosome the Y chromosome.

After performing a number of experiments and analyzing his results, Morgan discovered that the X and y chromosomes determine the sex of an organism. For this reason, the X and the Y chromosomes are called the sex chromosomes. In general, an organism (such as a fruit fly or human) that has two X chromosomes (XX) is female. An organism that has one X chromosome and one Y chromosome (XY) is a male. In 1886, the Dutch botanist Hugo

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De Vries made an accidental discovery. The results of his discovery took the science of genetics beyond the groundbreaking work of Gregor Mendel.

Devries was out walking one day when he came across a group of flowers called American evening primrose. As with Mendel's pea plants, some primrose appeared different from the others. De Vries wondered why this was so. He bred the primroses and got results similar to the results of Mendel's experiments with pea plants. He also found that every once in a while; new variations appeared among the primroses, variations that could not be explained at that time by the laws of genetics. Virtual microscope http://science.howstuffworks.com/cell.htm

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De Vries called the sudden changes he observed in the characteristics of primroses mutations. Mutations are genetic mistakes that can affect the way in which traits are inherited. The word mutation comes form the Latin word that means change. A mutation is a change in a gene or chromosome. If a gene or chromosome mutation occurs in a body cell such as a skin cell, the mutation affects only the organism that carries it. But if the mutation takes place in a sex cell, that mutation can be passed on to an offspring and that offspring then may pass it on to the next generation. Many mutations are harmful; that is they reduce an organism's chances for survival or reproduction. For example, one mutation in a gene causes a serious human blood disease called sickle cell anemia. Sickle cell anemia results in red blood cells that are shaped like a crescent moon (or a sickle, which is a farm tool used to cut grain). Red blood cells normally carry oxygen to the body cells. People who have two genes for sickle cell anemia have difficulty obtaining enough oxygen because the sickle-shaped red blood cells cannot carry oxygen to all the cells in the body. Sickle cell anemia also cause severe pain, because the sickle cells may clump together and clog tiny blood vessels. If left untreated, sickle cell anemia may even cause death. Not all mutations are harmful. Some mutations are helpful and cause desirable traits in living things. When mutations occur in crop plants, the crop may become more useful to people. A gene mutation in potatoes produced a new variety. This new variety is called Katahdin potato. This potato is resistant to diseases that attack other varieties. The new potato also looks and tastes better than other types of potatoes. Seedless navel oranges are also the result of mutations. These oranges are sweeter and juicier than ordinary oranges with seeds. Genetic disease http://biologyinmotion.com/evol/index.html

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chromosomes may result in certain genetic disorders. Some of these disorders can be detected by examining persons' chromosomes.

A karyotype is a picture of chromosomes in a nucleus that shows the size, number and share of all the chromosomes in an organism. The presence of such a group of three chromosomes is called trisomy. When a person has an extra chromosome in the twenty-first pair, a condition called trisomy-21 results. Trisomy-21 is

also known as Down syndrome. People with Down syndrome may have various physical problems and some degree of mental retardation. However, many people with Down syndrome lead normal, active lives

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and often make valuable contributions to society. Is there a way of knowing before a child is born as to whether he or she will have Down syndrome or another inherited disorder? One method of diagnosing a genetic disorder such as Down syndrome is called amniocentesis. Amniocentesis involves the removal of a small amount of fluid from the sac that surrounds a baby while it is still inside its mother's body. This fluid contains some of the baby's cells. Using a microscope, the doctor can examine the chromosomes in these cells. In this way, doctors can discover whether or not an unborn child had Down syndrome. Down syndrome or trisomy 21 is the most frequent genetic cause of mild to moderate mental retardation and associated medical problems and occurs in one out of 800 live births, in all races and economic groups. Down syndrome (extra chromosome 21). This is also known as mongolism or trisomy 21. Symptoms are decreased muscle tone, asymmetrical skull, slanting eyes and mental retardation. Down syndrome is a chromosomal disorder caused by an error in cell division. A new test that gives faster results than amniocentesis is now

sometimes used an alternative. This test requires the removal of cells from the membrane surrounding the developing baby. Parents who are concerned that they might pass a genetic disorder on to heir children should consult a genetic counselor. At present, there are no cures for genetic disorders. However, doctors and scientist are working to develop possible cures. In early 1983, scientists discovered a

chemical that could slightly change the structure of the gene that caused sickle cell anemia. Changing the structure of the sickle cell gene could help people with sickle cell anemia to carry larger amounts of oxygen throughout their bodies.

Sex-linked TraitsSome human traits occur more often in one sex than in the other. Usually, the genes for these traits are

carried on the X chromosome, which is a sex chromosome. Traits that are carried on the X chromosome are called sex-linked traits because they are passed form parent to child on a sex chromosome. Unlike X chromosomes, Y-chromosomes carry few, if any additional genes. (The maleness gene is one of the few genes carried on the Y chromosome.) So any gene- even a recessive one- carried on an X chromosome will produce a trait in a male who inherits the gene. There is no matching gene on the Y chromosome to mask or hide the gene on the X chromosome. The situation is not the same for the female, however. DO you know why? Females have two X chromosomes; a recessive gene on one X chromosome can be masked or hidden by a dominant gene on the other X chromosome. As a result, females are less likely than males to inherit sex-linked traits.White blood cell simulation- Game http://www.niehs.nih.gov/kids/minesearch/minesearch.htmlDust mite simulation –Game http://www.time.com/time/covers/1101010723/timeline.html Human body site http://www.kumc.edu/instruction/medicine/anatomy/histoweb/ Human systems http://bugscope.beckman.uiuc.edu/diversions/ Bugs in a scanning electron http://gslc.genetics.utah.edu/ -Hot link

An example of a disorder caused by a sex-linked recessive trait is hemophilia. Hemophilia is an inherited disease in which the blood clots abnormally slowly or not at all. Hemophilia is also called "bleeder's disease'. For a person who has hemophilia, even a small cut or bruise can be extremely dangerous. People who have hemophilia often have to receive regular blood transfusions. In the 1980's, people who had hemophilia and others who received blood transfusions (for example during surgery) were in danger of contracting AIDS from contaminated blood. Now, however, the blood supply is routinely screened for the presence of the AIDS virus. According to Greek mythology, when curious Pandora opened a forbidden box

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she set loose all the miseries and evils known to the world. One of them was undoubtedly the virus the very name of which is Latin for slime, poison and stench!

PedigreesA pedigree (often called a "family tree") shows the relationship among the individuals in a family. A

pedigree like the one on the next page can also be used tot trace the inheritance of a particular trait in a family. The trait recorded in a pedigree could be an ordinary trait, such as hair color or a disorder, such as hemophilia.

The human pedigree on the next page traces the pattern of inheritance of hemophilia in the royal families of Europe beginning with Queen Victoria of England. By studying the pattern of inheritance revealed in the pedigree, it is possible to determine whether a trait is dominant or recessive, as well as whether it is sex linked.

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Color blindness is another sex-linked recessive trait. A person who is colorblind cannot see the differences between certain colors, such as red and green. Difficulty in distinguishing between the colors red and green is the most common type of color blindness. More males than females are color blind. A colorblind female must inherit two recessive genes for colorblindness, one from each parent. But a colorblind male needs to inherit only one recessive gene. Almost 10% of human males experience color vision deficiency (compared with 0.4% of females). The most common form of these abnormalities is characterized by an inability to distinguish between red and green hues.

Why is this so? Remember that males do not have a matching gene on the Y chromosome that could mask the recessive gene on the X chromosome. Some of the traits that seem to be sex-linked are actually not caused by genes located on the X chromosome. For example, baldness is much more common in men than in women. SO you might think that baldness is a sex-linked trait. However, male-pattern baldness is a sex-influenced trait. A sex-influenced trait is a trait that is expressed differently in males than it is in females. It is called male-pattern baldness because men who inherit one gene for baldness and one gene for normal hair have a tendency to be bald, whereas women do not. Scientists are not totally sure how a person's sex influences the expression of certain genes, but they think that male sex hormones may play a role such as testosterone.

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SELECTIVE EVOLUTIONMore than 12,000 years ago, people living in the part of the world now called Iraq, discovered that

wild wheat could be used as food. Through a process of trial and error, these early farmers were able to select and grow wheat that had larger and more nutritious grains than the original wild wheat. People have been breeding plants and animals to produce certain desired traits ever since. This process is called selective breeding.

Selective breeding is the crossing of plants or animals that have desirable characteristics to produce offspring with those desirable characteristics. Through selective breeding, modern plant and animal breeders are able to produce organisms that are larger in size, provide more food, or are resistant to certain disease. For example, leaner cattle produce low-fat beef that is more healthful than the beef from fatter cattle. What other examples of selective breeding are you familiar with?

Sometimes breeders produce desired traits in the offspring by combining two or more different traits from the parents. To do this, breeders use a technique called hybridization. Hybridization is the crossing of two genetically different but related species of organisms. When the organisms are crossed, a hybrid is produced. (Recall that a hybrid is an organism that has two different genes for a particular trait.)Genetic information wealth http://www.ncbi.nlm.nih.gov/books/bv.fcgi?call=bv.View..ShowTOC&rid=gnd.TOC&depth=2 Evolution demonstrations http://www.pbs.org/wgbh/evolution/sex/guppy/index.html Evolution demonstrations http://www.pbs.org/wgbh/evolution/darwin/origin/index.html Darwin and evolution http://www.literature.org/authors/darwin-charles/the-origin-of-species/ Fossils http://www.pfizerfunzone.com/funzone/discovery/index.html

A hybrid organism is bred to have the best traits of both parents. For example, a mule is a hybrid that combines the traits of two different species, horses and donkeys. A mule is the offspring of a female horse and a male donkey. Some hybrids are produced naturally. Ancient wild wheat, for example, was a hybrid that formed naturally from the crossing of one species of wild wheat with a species of wild goat grass. The result was a wheat plant with nutritious grains that could be made into bread. Early farmers were able to preserve this new hybrid wheat by selecting some of the best grains and planting them for the next harvest. In some ways, hybrid offspring may have traits that are better than those of either parent. The hybrid offspring may be stronger or healthier than its parents. Such offspring

are said to have hybrid vigor. The word vigor means strength or health. Mules, for example, have more endurance than horses and are stronger than donkeys. One disadvantage of hybridization however, is that the hybrid offspring is usually sterile, or unable to reproduce. Darwin's origin of the species http://www.nationaldinosaurmuseum.com.au/dinoinfo/index.htm Evolution http://www.pbs.org/wgbh/evolution/

Another selective-breeding technique is called inbreeding. Inbreeding is the opposite of hybridization. Inbreeding involves crossing plants or animals that have the same or similar sets of genes, rather than different genes. Inbred plants or animals have genes that are very similar to their parent's genes. One purpose of inbreeding is to keep various breeds of animals, such as horses, pure. Purebred animals tend to keep and pass on

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their desirable traits. For example, a purebred racehorse that has won many races may be able to pass on its speed and strength to its offspring.Human Evolution http://www.talkorigins.org/faqs/homs/species.html Human examples of fossils http://www.mnh.si.edu/anthro/humanorigins/ha/a_tree.htmlHuman evolutionary paths http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookHumEvol.htm Human Evolution l http://www.poignance.com/java/life.htmlCellular evolution http://www.niehs.nih.gov/kids/illusions.htm Geologic timeline web site http://www.kathimitchell.com/cells.html- Super Hot link http://www.kidinfo.com/Health/Human_Body.html

Unfortunately, inbreeding reduces an offspring's chances of inheriting new gene combinations. In other words, inbreeding produces organisms that are genetically similar. This similarity or lack of genetic difference, in inbred plants and animals may cause the organisms to be susceptible to certain diseases or changing environmental conditions. For example, almost all cheetahs are genetically identical. If all cheetahs have nearly the same genes, they are all susceptible to the same diseases. As a result, wild cheetahs might eventually become extinct, or die off. The variation on a theme is the strength of t he idea of sexual reproduction. This ability to create slightly different copies that may be able to cope with challenges may allow a species to survive an event.CHECK FOR UNDERSTANDING

22. What is selective breeding?___________________________________________________23. How is inbreeding different from hybridization?_______________________________________________________________________________________24. What is one advantage of inbreeding?_______________________________________________________________________________________25. What is one disadvantage to inbreeding?_______________________________________________________________________________________26. What are the symbols for a male and a female who do not carry a trait on a pedigree?_______________________________________________________________________________________27. Why are sex linked traits expressed more in males than in females?_______________________________________________________________________________________28. What are the symbols for a male and a female who do carry a trait on a pedigree?_______________________________________________________________________________________29. The first man to really do work with genetics and come up with some of the basic laws of genetics was

a. Charles Darwin b. Gregor Mendelc. a female monk d. Albert Einstein

30. Gregor Mendel worked with this type of plant that was easy to grow and easy to breed. What type of plant did he work with?

a. roses b. beans c. peas d. corn

31. Which of the following words best describes the passing on of traits from an organism to its offspring?a. dominate traits b. Chromosomesc. recessive traits d. heredity

32. If your father is pure dominate for the recessive trait baldness, how would you write the genotype for it? a. Bb b. bB c. BB d. bb

33. Which of the following traits would best represent a trait for pure recessive tallness?a. Tt b. tt c. TT d. tT

34. If you were to write a hybrid trait for shortness, how would you go about writing this?a. SS b. ss c. sS d. Ss

35. According to t he make up of sex-linked traits, who is more likely to inherit genetic disease?16

a. malesb. both males and females have an equal chance of inheriting genetic diseasesc. femalesd. neither males or females can inherit genetic diseases.

36. If you father had the hybrid trait for hair whirl (Hh), what are the chances of you receiving the dominant H gene?

a. 1/4 b. 50% c. 1/3 d. 25%

37. Which of the following answers best defines what a pedigree is in genetics?a. a type of dog foodb. the genetic make-up of an offspringc. a graphic record of genetic background of a certain familyd. a family bush

What your parents never knew…….In the star unit we discovered the evolution of stars. By using the physics of light production we

discovered with a spectra scope, the formation of heavy atoms from lighter atoms. When his theory first came to light in the 1500's Galileo nearly lost his life for suggesting evolution in the universe. However, the Catholic religion has become more understanding as the evidence has piled up into mountain ranges of data. Evolution in biology is a more recent discovery (1900's) based on technology and our understanding of chemistry, math and physics. It was not until September of 1998 that the Pope agreed that the evidence for biological evolution was now truly overwhelming and threw the support of the Catholic Church behind it. Several years later the church forgave Galileo for stating the heavens were not perfect and unchanging. The Catholic Church’s position now is that the Sun is the center of our solar system.

In stellar evolution we discovered light elements such as hydrogen are fused into helium, carbon, oxygen and other elements as these super massive stars exert huge pressure and temperature in the explosion of the star called a super nova.

Nuclear investigations that created atomic and hydrogen bombs allowed the understanding and practical investigations of the forces that hold the nucleus of the atom together and drive the process of nuclear fusion in stars. Chemical experiments and stellar evolution theories have allowed scientists to discover how atoms bond. Discovery, if not complete understanding of the octet rule allowed scientist to predict when and where atoms would bond to complete their outer valence shell.

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The stage was now set for the next evolution in human understanding. Mendel had identified the units of inheritance and called them genes. Charles Darwin had published the Theory of natural selection, which showed possible ways these traits could be passed from one generation to the next as the situation changed or one trait was found to offer some advantages to survival or reproduction. Chemists and biologists now wanted to understand the mystery of these units of inheritance, or genes.

Chemical EvolutionAs early as the 1920's, the Soviet biochemist A.I. Oparin thought that organic molecules could be made from the inorganic parts of the primitive atmosphere in the presence of an energy source, such as lightning or sunlight. In 1953 Stanley Miller provided support for Oparian's ideas through and ingenious experiment.

Miller placed a mixture resembling the probable primitive atmosphere (methane, ammonia, hydrogen and water) in a closed reaction vessel at 80°C. He then exposed it to electrical spark discharges for a week or more. At the end of this period, Miller discovered that a variety of amino acids and other organic acids had been produced. A number of scientists have conducted similar experiments since the mid-1950s and have shown that a wide variety of biological molecules can be made using several energy sources. Ultraviolet light or

electrical discharges (like lightning, which acted on the Earth's primitive atmosphere) can cause these molecules.

These results agree with Oparin's original proposal that early oceans might have contained huge number of organic molecules. Indeed, the early oceans might have resembled a very dilute "soup" or "broth". The formation of this "soup" constitutes the first phase of what has been called chemical evolution.

The next stage of chemical evolution would have involved the joining of molecular building blocks to yield polymers such as polypeptides, polynucleotides, and polysaccharides. It has also been suggested that the molecules became concentrated on the surfaces of clay particles. This concentrating effect would help polymer formation.

When such hot liquids are cooled, form small, cell-like structures. These microspheres show cell-like behavior. www.cnn.com/TECH/space/ 9904/01/life.extremes/

Eventually, in one-way or another, chemical or biological evolution began with the formation of the first true cells. These must have been living at the expense of organic molecules available in the "soup" that surrounded them. Eventually, as nutrients were eaten, the first autotrophs capable of eating CO2 would have arisen. But these first life forms were not photosynthetic organisms. They ate chemicals and gained energy from breaking bonds between chemicals and minerals. Some of these life forms still exist at the bottom of deep oceans near thermal vents.

DNADNA stands for deoxyribonucleic acid. The two scientists who discovered DNA were the American biologist James Watson and the British physicists Francis Crick. In 1962, Watson and Crick shared the Nobel Prize for the physiology or medicine for their work on the structure of DNA.

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The DNA molecule is the basic substance of heredity. DNA stores and passes on genetic information from one generation to the next. Many scientists believe that the discovery of thee structure of DNA was the most important biological breakthrough of the twentieth century. Several scientists were involved in the research on the structure of the DNA molecule.

The British scientist Rosalind Franklin managed to gather large amounts of DNA fibers. Using models, they were able to come up with a structure for DNA that matched the pattern in Rosalind Franklin's X-ray photographs. Finding the structure of DNA allowed scientists to crack the genetic code.

Watson and Crick's discovery showed that chromosomes are made up of long strands of DNA molecules. It is the DNA molecules in chromosomes that make up the

genes. So DNA actually controls the production of the proteins and determines all the traits passed from parents to their offspring. You may be wondering why Rosalind Franklin, whose research played and important part in unlocking the structure of DNA, did not share the 1962 Nobel Prize with Watson and Crick. The reason Franklin is that Franklin died in 1958, and Nobel Prizes are given only to living scientists.

A DNA molecule looks like a twisted ladder, or spiral staircase. The sides of the ladder are made of sugar molecules and phosphate groups (containing the elements hydrogen, phosphorus and oxygen). Pairs of substances called nitrogen bases form the steps, or rungs of the ladders. Nitrogen bases are molecules that contain the element nitrogen, as well as other elements. There are four different nitrogen bases in DNA. They

are adenine, guanine, Cytosine and Thiamine. The capital letters A, G, C and T are used to represent the four different bases.

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The two bases that make up each rung of the DNA ladder are combined in very specific ways. The American biochemist Erwin Chargaff had found that in any sample of DNA, the amount of Adenine is always equal to the amount of Thiamine. The same is true for Guanine and Cytosine. Using these clues Watson and Crick reasoned that in the DNA ladder, Adenine always pairs with Thiamine and Guanine always pairs with Cytosine.

A DNA ladder may contain hundreds or even thousands of rungs. So the DNA molecule that makes up a single chromosome may have hundreds or thousands of pairs of nitrogen bases. In addition to discovering DNA's structure, Watson and Crick reasoned that the order of the nitrogen bases on the DNA molecule determines the particular gene on the chromosome.

That is why DNA is said to carry the genetic code. The genetic code is actually the order of nitrogen bases on the DNA molecule, for example, ACGGTTCAAG. Because a DNA molecule can have many hundreds of bases arranged in any order, the number of different genes is almost limitless. Different genes produce different proteins. That is why living things on earth can display such a wide variety of traits. Changing the order of only one pair of nitrogen bases in a DNA molecule can result in a new gene that determines a completely different trait. The sequences ATTCGG and TATCGG, for example, differ in the order of only two letters. Yet this small difference might be enough to change the genetic code and thereby produces two totally different proteins, resulting in different traits.

In fact, most mutations are actually just a change in the order of bases in a particular gene. As an organism grows and develops, the number of body cells must increase. In order for the total number of cells to increase and for the organism to grow, each cell must be reproduce.

A cell reproduces by dividing into two new cells. Each new cell, called a daughter cell, is identical to the parent cell. As a result, each body cell in an organism contains all the genetic information that determines the organism's traits.

For a parent cell to produce two identical daughter cells, the exact contents of its nucleus must be transferred into the nucleus of each new cell. In other words, the genetic code in the parent cell must be passed on to each daughter cell. Before a body cell can divide into two daughter cells, the DNA in the nucleus

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must be duplicated, or copies, so that each new cell gets the same DNA as the original parent cell. How does this happen?

The process in which DNA molecules form exact duplicates is called replication. During the first step in replication, the DNA molecule separates, or unzips. Separation takes place between the two nitrogen bases that form each of the rungs of the DNA ladder. At the end of the first step in replication, the DNA ladder has split into tow halves, or strands. In the next step, free nitrogen bases that are floating in the nucleus begin to pair up with the nitrogen bases on each strand of the DNA ladder. Remember that Adenine (A) always

attaches to Thiamine (T) and Guanine (G) always attaches to Cytosine (C). Once the new bases are attached, two new DNA molecules are formed.

Each new DNA molecule is and exact duplicate of the original DNA molecule. In other words, each new DNA molecule contains the same genetic code as the original DNA molecule and can transfer this code to the new daughter cell. Recall that genes are made of long strands of DNA. The main function of genes is to control the making of proteins. Proteins are what the body needs for building and repairing cells. Most of the cells that control the body's vital functions are also made of and controlled by proteins. For example, hormones such as insulin are proteins that act as the body's chemical messengers. Enzymes, such as pepsin, are proteins that speed up chemical reactions in the body. These and other proteins are made in the cytoplasm of cells. The cytoplasm is the material outside the cell nucleus.

The production of protein is called synthesis. (The word synthesis means to put together.) Proteins are long molecules that are made up of chains of smaller molecules called amino acids. Amino acids are the building blocks of proteins. There are 20 different amino acids that join together to form protein molecules. It is the job of the DNA molecules in chromosomes to control the order in which these 20 amino acids are put together to make a protein molecule. How does DNA do this?

Protein synthesis takes place in the cytoplasm of a cell, outside the nucleus. The chromosomes containing DNA are found only inside the nucleus. The first thing that is needed in protein synthesis is a messenger to carry the genetic code from the DNA inside the nucleus to the cytoplasm outside the nucleus. This genetic messenger is called ribonucleic acid or RNA. RNA is similar to DNA, but with some

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differences. Unlike a DNA molecule, which looks like a twisted ladder, and RNA molecule looks like a ladder split in half vertically

Genetic EngineeringAt one time most hybrid plants and animals were produced through selective-breeding techniques.

Today, genetic engineering may soon be the primary method of producing hybrids. Genetic engineering is the may soon be the primary method of producing hybrids. Genetic engineering is the process in which genes, or pieces of DNA, from one organism are transferred into another organism. In one form of genetic engineering, parts of and organisms DNA are joined to the DNA of

another organism. The new piece of combined DNA is called recombinant DNA. Pieces of recombinant DNA contain DNA from two different organisms. Usually, DNA is transferred from a complex organism (such as a human) into a simpler one (such as a bacterium or a yeast cell). Bacteria and yeast cells reproduce, copies of the recombinant DNA are passed on from one generation to the next. In each generation, the human DNA causes the bacteria or the yeast cells to produce human protein. Scientists use special techniques to make recombinant DNA. Refer to the diagram to the right as you read the description that follows. Some of the bacterium E. coli is in the form of a ring called plasmid. You might think of plasmid as a circle of string. Using special techniques, scientist first removes a plasmid from a bacterium and cuts it open. They then remove a piece of DNA from a human cell. Think of this human DNA as a short piece of string. The scientists then tie this piece of human DNA to the cut end of the bacterial DNA. The bacterial DNA again forms a closed ring. The bacterial DNA ring now contains a human gene that directs the production of a human protein. Finally, the scientists put the recombinant DNA back into the bacterial cell. What do you think happens next? The bacterial cell and its offspring now produce the human protein coded for the human DNA. In this way, large amounts of human protein can be produced outside the human body.

CHECK FOR UNDERSTANDING

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38. Crossing two genetically different plants or animals is calleda. inbreeding b. hybridizationc. genetic engineering d. crossbreeding

39. The word vigor in the term hybrid vigor meansa. offspring b. strength c. weakness d. trait

40. Purebred plants and animals are produced througha. inbreeding b. hybridizationc. genetic engineering d. recombinant DNA

41. Inserting genes from one organism into another is an example ofa. hybridization b. inbreedingc. crossbreeding d. genetic engineering

42. To make recombinant DNA, human DNA is usually transferred into yeast cells ora. mouse cells b. viruses c. bacteria d. plant cells

43. Inbreeding produces organisms that are geneticallya. different b. identical c. similar d. opposite

44. Genetic engineering can be used to producea. insulin b. human growth hormone c. interferon d. all of these

45. The human protein needed to treat diabetes mellitus isa. human growth hormone b. interferonc. insulin d. hemoglobin

The Chromosome TheoryThe work of Gregor Mendel provided many early solutions to the riddle of genetics. But Mendel did

not have all the answers. For example, he did not know where the hereditary factors, or genes, are located in the cell. The first clue came in 1882 when the German biologist Walther Fleming discovered chromosomes. Chromosomes are rod shaped structures that are found in the nucleus of every cell in an organism. Walter Sutton, an American graduate student who in 1902 was doing research on chromosomes, provided the next clue.

While observing grasshopper chromosomes, Sutton discovered where the genes in a cell are located. Mitosis is the process by which an organism gets larger by adding more cells, or replacing cells that have died.

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Grasshoppers have 24 chromosomes, arranged in 12 pairs. This means that every body cell in a grasshopper contains 24 chromosomes. Sutton observed that each of a grasshopper's sex cells (sperm or egg) contained 12 chromosomes, or half the number in body cells. Sutton also observed what happened when a male sex cell (sperm with 12 chromosomes) and a female sex cell (egg with 12 chromosomes) joined. The fertilized egg that was formed had 24 chromosomes, the original number, arranged in 12 pairs. In other words, the grasshopper offspring had exactly the same number of chromosomes as each of its parents.

From his work, Sutton concluded that chromosomes carried Mendel's hereditary factors, or genes, from one generation to the next. In other words, genes are located on chromosomes.

Sutton's idea that genes are found on chromosomes came to be known as the chromosome theory of heredity. According to the chromosome theory, genes are carried from parents to their offspring on chromosomes. How amazing it now seems that Mendel was able to do all of his work without even knowing about chromosomes! Today, scientists know that chromosomes play an essential role in heredity. Chromosomes control all the traits of an organism. How do they perform this complex task? The main function of chromosomes is to control the production of substances called proteins. All organisms are made up primarily of proteins. Proteins determine the size, shape, and other physical characteristics of an organism. In other words, proteins determine the traits of an organism.

The sex chromosomes

The shape of the 23rd pair of chromosomes was not the same for males and females. One chromosome of the pair was shaped like a rod, and the other chromosome of the pair was shaped like a hook. Morgan called the rod-shaped chromosome the X chromosome and the hook-shaped chromosome the Y chromosome. After performing a number of experiments and analyzing his results, Morgan discovered that the X and Y-chromosomes determine the sex of an organism. For this reason, the X and Y-chromosomes are called sex chromosomes. In general, an organism (such as a fruit fly or a human) that has two X chromosomes (XX) is a female. An organism that has one X chromosome and one Y chromosome (XY) is a male. In 1886, the Dutch botanist Hugo De Vries (duh-vREEz) made an accidental discovery. The results of his discovery would take the science of genetics beyond the groundbreaking work of Gregor Mendel. De Vries was out walking one day when he came across a group of flowers called American evening primroses. As with Mendel's pea plants, some primroses appeared very different from others. De Vries wondered why this was so. He bred the primroses and got results similar to the results of Mendel's

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experiments with pea plants. But he also found that every once in a while; new variations appeared among the primroses—variations that could not be explained by the laws of genetics at that time. De Vries called the sudden changes he observed in the characteristics of primroses mutations. Mutations are genetic mistakes that can affect the way in which traits are inherited. The word mutation comes from a Latin word that means change. A mutation is a change in a gene or chromosome. If a gene or chromosome mutation occurs in a body cell such as a skin cell, the mutation affects only the organism that carries it. But if a mutation takes place in a sex cell, that mutation can be passed on to an offspring and that offspring then may pass it on to the next generation.

Inbreeding for traits Another selective-breeding technique is called inbreeding. Inbreeding is the opposite of hybridization. Inbreeding involves crossing plants or animals that have the same or similar sets of genes, rather than different genes. Inbred plants or animals have genes that are very similar to their parents' genes. One purpose of inbreeding is to keep various breeds of animals, such as horses, pure. Purebred animals tend to keep and pass on their desirable traits. For example, a purebred racehorse that has won many races may be

able to pass on its speed and strength to its offspring.

www.pbs.org/.../tryit/ evolution/footprints.html

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Unfortunately, inbreeding reduces an offspring's chances of inheriting new gene combinations. In other words, inbreeding produces organisms that are genetically similar. This similarity, or lack of genetic difference, in inbred plants and animals may cause the organisms to have certain diseases or not adapt to changing environmental conditions. For example, almost all cheetahs are genetically identical. If all cheetahs have nearly the same genes, they could all catch or have the same diseases. As a result, wild cheetahs might eventually become extinct, or die off. The variation on a theme is the strength of the idea of sexual reproduction. This ability to create slightly different copies that may be able to cope with challenges may

allow a species to survive an event.

Darwin’s theory of evolution by natural selection is a cornerstone of current biological understanding.   The evidence for biological evolution is found in the geological (fossil) record. The evidence for biological evolution is found in the common features of living and extinct organisms. The evidence for biological evolution is found in past and present day animal breeding (artificial selection). In the modern world: pesticide resistance, antibiotic resistance, gene therapy, and evolution in natural populations. Homologous structures: tetra pod limbs, Vestigial structures: pelvic girdle of snakes, comparative embryology: pharyngeal slits, comparative molecular biology: cytochrome c, blood proteins, salt levels in body fluids, comparative anatomy and morphology, homologous structures: the same body parts, modified in different ways in different

lines of descent from a common ancestor. Example: the forelimb of an alligator, the wing of a bird, the arm of a monkey, and the wing of a bat. Why should moles, bats, whales, dogs, and humans among others possess forelimbs based on the same bones that have been adapted in each case unless inherited from a common ancestor? Tails have a widely varied role in mammal bodies. They appear essential for monkeys, but the small, wispy tail in a large elephant seems useless. Tails are absent in adult apes and humans, except they appear in early embryos and are residual in the coccyx at the end of the vertebra. In some human babies with a mutant tail are clipped at birth.

Vestigial Structures

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In all animals there are vestigial structures of one form or another. In humans, for example, there are at least four complete organs with no function. The appendix, ungula, tonsils and coccyx are all useless now. The reason for this is that adaptations, which are required in one species, may no longer needed when the species evolves into a new form. Humans also have wisdom teeth, ear muscles, tonsils, nictating eye membrane, appendix, male nipples and body hair. Unless their presence gives some specific and large disadvantage in the new life forms, the vestigial organ may remain for a very long time. The earlier stage is a clue to an evolutionary path.The frigate, a non-aquatic bird, does not benefit from the webbing on its feet. In flightless birds the number of usable limbs is reduced from four to two with the presence of two non-functional limbs. Penguins possess hollow bones although they do not have the same need for minimal body weight as flying birds. Otherwise fully aquatic animals such as sea snakes, dolphins, and whales must rise to the surface to breathe air. Modern whales exhibit several non-functional vestigial traits. Fetuses of baleen whales bear teeth that are absorbed as the fetus matures; adult baleen whales do not have teeth.Paleontologists proposed that whales had evolved from land mammals with legs, and therefore, in an example of its predictive power, the theory of evolution forecast that legs would be found on fossilized whales. In recent years the evolution of whales from now extinct land mammals has become well documented through newly found fossils from the Eocene epoch, about 50 million years ago (Wong 2002). The fossilized whales contain well-defined feet and legs. In modern adult whales, the front legs have evolved into flippers and the rear legs have become so small that no visible appendages appear. Hindlimbs still appear in the fetuses of some modern whales but disappear by adulthood. Externally invisible, vestigial diminished pelvic bones occur in modern adult whales. The idea of evolution accounts for these useless vestigial elements as left-overs in the development of whales from land mammals.

Fossils Much of the fossil evidence that what we know about macro evolutionary patterns comes from the study of fossils. There are many problems with life forms turning into fossils, first the life form must die in the correct deposition environment, have the right size, hard body parts and not become erased during later geological cycles. Fossils are recognizable physical evidence of ancient life found in sedimentary rocks. Some kinds of organisms and some parts of organisms are more likely to fossilize than others. Some environments or habitats are more likely to fossilization than others.  Fossilization of a life form is a low probability event. Just think of all the places you could die where you would not be turned into a fossil!

Interpretation of the fossil record* *There are always exceptions!

• The older the rock layers, the older the fossils! • The oldest terrestrial rocks do not contain fossils. • The oldest fossil bearing rocks are about 3.85 billion years old and contain fossils of prokaryotes.

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• The oldest fossil eukaryotes are found in rocks about 1.2 billion years old. • The oldest multicellular organisms are found in rocks about 700 million years • The oldest vertebrates: 525 million • The oldest tetra pods: 380 million • The oldest mammals: 320 million • The oldest primates: 55 million • Oldest Homo sp. (H. erectus): 2.2- 5 million • Oldest H. sapiens: 0.25-2 million

Check for understanding46.German biologist Walther Fleming discovered a. chromosomes b. adenine c. cytosine d. guanine

47.Mitosis is the process by which an organism gets larger by adding more cells, or replacing cells that have a. moved away. b. grown c. died. d. flown away

48.According to the chromosome theory, genes are carried from parents to their offspring on a. Vacuoles. b. Mitochondria c. chromosomes. d. Golgi complex.

49. The main function of chromosomes is to control the production of substances called a. genes. b. populations. c. proteins. d. Deoxyribose sugars.

50. Morgan discovered that the X and Y-chromosomes determine the sex of an a. organism. b. population. c. chromosome d. cell

51. The word mutation comes from a Latin word that means a. weirdo b. creepy c. change. d. odd.

52. The variation on a theme is the strength of the idea of a. asexual reproduction. b. numbers. c. sexual reproduction. d. multiplication. 53. Vestigial structures are organs or tissues with no function, such as a(n) _________. a. head b. arm c. appendix d. flipper

54. The Theory of evolution forecast that legs would be found on fossilized a. people b. snakes c. whales. d. all of these.

55. Fossils are recognizable physical evidence of ancient life found in _______________rocks.a. igneous b. sedimentary c. metamorphic d. fossilized

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