My Classroom Material 132 - BIOLOGY JUNCTION

Food Chemistry

Introduction:

All living things are made up of one or more cells, and the cells in turn contain many kinds of molecules. In this lab we will be looking at several different macromolecules (large molecules): proteins, carbohydrates, and lipids (specifically fats). Various chemicals will be used in this laboratory to test for the presence of these molecules. Most often, you will be looking for a particular color change. If the change is observed, the test is said to be positive because it indicates that a particular molecule is present. If the color change is not observed, the test is said to be negative because it indicates that a particular molecule is not present.

You will be using these tests to determine which of the macromolecules are present in various samples of food.

In all of the procedures, you will need to include a distilled water sample as a control. Usually, a control goes through all the steps of the experiment but lacks one essential factor (the experimental variable). This missing factor allows you to observe the difference between a positive result and a negative result. If the control sample tests positive, you know your test is invalid. Some tests may also contain other controls to make sure certain additives are not contaminated with the substance for which you are testing.

Proteins:

Protein molecules are long chains of amino acids joined by peptide bonds.

Biuret reagent, which is a blue color, contains a strong solution of sodium or potassium hydroxide (NaOH or KOH) and a very small amount of very dilute copper sulfate (CuSO4) solution. The reagent changes color in the presence of proteins or peptides because the amino group (H2N-) of the protein or peptide chemically combines with the copper ions in biuret reagent.

Carbohydrates:

Carbohydrates include sugars and molecules that are chains of sugars. Glucose is a simple sugar, also known as a monosaccharide. Sucrose, or table sugar is a disaccharide, two sugar units bonded together. Starch is a polysaccharide, a long chain of glucose units.

Benedict’s reagent reacts with many sugars (both mono- and disaccharides) after being heated in a boiling water bath. Increasing concentrations of sugar give a continuum of colored products ranging from green through yellow and orange to orange red.

Iodine solution reacts with starch to produce colors ranging from a brownish to blue black.

Lipids:

Lipids are hydrophobic molecules which are insoluble in water and soluble in solvents such as alcohol and ether. Lipids include fats, oils, and cholesterol.

Lipids do not evaporate from brown paper, instead leaving an oily spot. Lipids also do not mix with water, forming a separate layer, usually on top of the water. However, some molecules mix with both water and lipids, and can be used to mix the two. These molecules are known as emulsifiers. The liver produces bile salts which act as emulsifiers in the digestive tract. Soaps and detergents also act as emulsifiers.

Summary of tests:

Biuret Reagent	Benedict’s Reagent	Iodine Solution	Brown Paper
Reacts with proteins or peptides, turns purple (protein) or pink (peptides)	Reacts with sugars, turns green through yellow to orange (green, less sugar, orange, more sugar)	Reacts with starch, turns dark brown to black	Lipids leave oily spot

Procedure:

Take some time to plan with your lab partner what tests you will do, and in what order before beginning the procedures.

There are available in the lab a variety of different types of common food. Choose at least 3 foods and test each for the presence of protein, carbohydrate (both starch and simple sugars), and fats. Be sure to plan your experiments before starting.

Form a hypothesis for each sample you have chosen to test.

Samples will need to be suspended in water for most tests. Using a mortar and pestle if necessary, break each sample to be tested into small pieces and suspend the pieces in a small amount of distilled water.

Also available are samples of each of the types of molecules for which you will be testing. Use these samples to try out the tests so that you will know what a positive result looks like.

Be sure to include a blank control (distilled water) with each test so you know what a negative result looks like. You may also include a positive control, a sample which you know contains the substance for which you are testing.

The procedures for testing for each type of molecule are given below.

Proteins and Peptides

Proteins:

Use a separate test tube for each sample to be tested, as well as one for a control.
Label each test tube.
Place about 1 mL of each sample (and control) in its test tube.
Add 5 drops of copper sulfate solution to each tube.
Add 10 drops of potassium hydroxide solution to each tube and mix.
Record the tube contents and final color in a data table.
Conclusions: which tubes contained protein?

Carbohydrates: Sugars and starch

Starch

Use a separate test tube for each sample to be tested, as well as one (or two) for a control.
Label each test tube.
Place about 1 mL of each sample (and control) in its test tube.
Add 5 drops of iodine solution to each tube and mix.
Record the tube contents and final color in a data table.
Conclusions: which tubes contained starch?

Sugar

Use a separate test tube for each sample to be tested, as well as one (or two) for a control.
Label each test tube.
Place about 1 mL of each sample (and control) in its test tube.
Add about 2 mL of Benedict’s reagent to each tube and mix.
Heat the tubes in a boiling water bath for 5-10 minutes.
Record the tube contents and final color in a data table.
Conclusions: which tubes contained sugar?

Lipids

Place a small sample of the material to be tested on a square of brown paper.
Place a small drop of water on the square of brown paper.
Compare the drop of water to the sample.
Wait at least 5 minutes. Evaluate which substance impregnates the paper and which is subject to evaporation. Record your results.
Conclusions: which sample contained lipids?

Conclusion Questions:

Why do experimental procedures include control samples?
How would you test an unknown solution for each of the following:
1. Sugars
2. Fat
3. Starch
4. Protein
Assume that you have tested an unknown sample with both biuret solution and Benedict’s solution and that both tests result in a blue color. What have you learned?
What purpose is served when a test is done using water instead of a sample substance?
Compare your results.

Lab report:

Lab reports must include the following:

A Title to the lab. A Purpose: What was studied in this lab, and why did we study it?
Procedure: a brief description of each type of test, what constitutes a positive test and what constitutes a negative test.
All data tables.
For each food sample, state your hypothesis and your conclusions. Did your results confirm or refute your hypothesis?
Answers to questions.
A brief analysis of what worked in this lab and what didn’t work, and why.

Evolution PPT Questions

Evolution
ppt Questions

History of Evolutionary Thought

1. What were Aristotle’s early ideas about life on Earth?

2. How long did these ideas last?

3. What was Linnaeus first to do?

4. What language is used for scientific naming?

5. What are the two words called in a scientific name?

6. This naming system is known as ____________ ______________.

7. Name the contribution that each of these men made to Darwin’s ideas on evolution:

a. Charles Lyell

b. George Cuvier

c. Thomas Malthus

d. James Hutton

e. Lamarck

f. Wallace

8. Which was published first – the Origin 0f Species by Darwin or Gregor Mendel’s papers on inheritance?

9. What was the name of George Cuvier’s theory on evolution?

10. What did Cuvier study in Paris and what did he find?

11. What did Cuvier decide was responsible for the disappearance of some species?

12. James ___________ was a Scottish _________ who studied fossils of _____________ in the Paris Museum.

13. Hutton’s ideas were known as _____________.

14. Briefly state Hutton’s idea on geological change.

15. Lyell proposed the theory of _________________.

16. Describe uniformitarianism.

17. How old did Lyell propose that the Earth was? How old did most people at this time believe the Earth was?

18. How did reading Lyell’s book help darwin on his voyage on the Beagle?

19. Lamarck was one of the first scientists to understand that change occurs over ___________.

20. Lamarck believed that changes were adaptations to the ____________ that organisms _____________ in their lifetime and that he thought could be passed on to _______________.

21. Explain Lamarck’s idea of the Law of Use and Disuse.

22. Lamarck’s theory of acquiring or losing traits by using or not using them led to his theory of evolution called the _____________ of ______________ _____________.

23. According to this theory new ___________ could arise over time.

24. According to Lamarck, if a blacksmith built up his muscles then he would have what type of sons?

25. According to Lamarck, if a giraffe stretched its neck reaching for leaves, what would its offspring look like?

26. What did Lamarck NOT know that made his theory incorrect?

27. Are genes changed by life activities?

Darwin the Naturalist

28. In what year and at what age did Darwin become the naturalist for the ship the HMS Beagle?

29. How long was the Beagle voyage around the world?

30. As Darwin sailed around the coast of __________ __________, he collected many different types of plants and animals on the mainland and on the islands.

31. Where are the Galapagos Islands and how were they formed?

32. What did Darwin discover about the animals on each type of island

33. How did the island species of finches and tortoises compare with those on the islands?

34. How did the necks of the tortoises compare with each other?

35. The island finches resembled a finch on the ___________.

36. Was the available food and habitat the same on all the islands? Explain.

37. What was different about the finches and why?

Darwin’s Observations & Conclusions

38. List three observations Darwin made on his travels that led him to propose his revolutionary idea about the way life changes over time.

39. Give an example of the uneven distribution of species noted by darwin.

40. Darwin collected both ___________ organisms and ____________ of organisms.

41. Give 2 examples of fossils collected by Darwin in which the species were no longer in existence.

42. Give a definition for evolution.

43. Left unchecked, what did Darwin predict would happen to the number od individuals in a population?

44. In nature, what tends to happen to the size of populations over time?

45. Competition among members of a population occur due to a limited number of ____________ _______________.

46. Only a ___________ of the offspring produced survive to the next generation.

47. The struggle for environmental resources is commonly called _____________ of the ____________.

48. How do individuals in population compare with each other?

49. Variation in a population is ______________.

50. Which organisms in a population are most likely to live offspring to pass on their traits?

51. This process is known as _____________ ___________ and was proposed by Charles ___________.

52. State Darwin’s theory of natural selection.

53. New ____________ evolve according to natural selection.

Ideas that Shaped Darwin’s Thinking

54. _____________ was an economist in 1798 that influenced Darwin’s thinking.

55. Malthus observed what about the birth rate of babies?

56. Malthus knew population size was limited by what?

57. According to Malthus, a high birth rate and limited resources caused what to happen?

58. List several things that organisms struggle for in the environment.

59. What did Malthus say would happen if the population size continued to groww unchecked?

60. The __________ rate should increase to balance the __________ of a population and the limited _____________ in the environment.

61. Did Darwin see this occurring in nature?

62. Most organisms produce ____________ offspring than can survive causing many to ________.

Darwin’s Theory of Evolution

63. Darwin proposed that organisms descended from what?

64. Over time, according to Darwin organisms __________ their form causing evolution of new ____________.

65. ___________ __________ is the driving force for evolution.

66. During the struggle for survival, which organisms survive to pass on their traits?

Origin of Species

67.How long after he returned to England did Darwin publish his book about evolution?

68. Why did Darwin wait so long to publish his ideas?

69. Darwin’s theory of evolution challenged both the ____________ and _____________ ideas at that time.

70. What made Darwin publish his book?

71. _______________ independently developed the same theory as Darwin.

72. Both Darwin and Wallace believed that __________ changed over time due to a _____________ for existence.

73. Both Darwin’s and Wallace’s papers were presented to the ____________ ______________ in July of __________.

74. How long after this did it take Darwin to finish writing his book?

75. Before Darwin, it was thought that species were perfectly made and _______________.

76. What group of people had been observing and using variations in organisms for a long time?

77. How were farmers using variation?

78. This process is called _____________ ______________ instead of natural selection that occurs in nature.

79. Artificial selection involves ____________ desired traits in stock or crops and __________ them to pass on the trait.

Controversy

80. Define these terms:

a. struggle for existence

b. survival of the fittest

c. descent with modification

d. Fitness

e. adaptation

81.What are the two types of adaptations?

82. Give some examples of physical adaptations.

83. Give some examples of behavioral adaptations.

84. What happens to organisms with LOW fitness?

85. How did changes in the Galapagos finches make them more FIT to survive?

86. Natural selection takes place over a _________ period of time.

87. Natural selection can be observed as changes in _______ structure, ecological _________, and ____________.

88. Do species today look them same as their ancestors?

89. Living species descended with changes from other __________ over periods of time.

90. What was a major problem in Darwin’s Theory?

91. The work of what scientists solved the problem of how variations were passed to offspring?

92. What is the complete title of Darwin’s book?

Theory of Evolution Today

93. List three main things used today to show how organisms are related.

94. Give two examples of evolution that has occurred today in a much shorter period of time.

95. Define macroevolution.

96. Define microevolution.

97. Darwin argued that Earth was ____________ of years old instead of thousands of years old.

98. One of the main pieces of evidence to support this ancient age of the Earth came from ___________ collected by Darwin.

99. Fossils are found in what type of rock layers?

100. Animals on different continents living in similar habitats show similar _______________.

101. All ____________ have similar bon structures known as ______________ structures.

102. Homologous structures have the same structure but different ______________.

103. Give 3 examples of homologous structures in vertebrates.

104. __________ structures seem to have no important function.

105. Give an example of a vestigial structure in humans.

106. What is an embryo?

107. How does the embryonic development of different vertebrates compare to each other?

Food Testing

Chemical Tests for Nutrients in Food

INTRODUCTION:

Cells are made up of small molecules like water; ions such as sodium and magnesium, and large organic molecules. There are four important types of large organic molecule in living organisms — proteins, carbohydrates (sugars & starches), lipids (fats), and nucleic acids. Proteins, carbohydrates, and fats serve as nutrients in the food that we eat.

In this experiment you will evaluate the nutrient content of unidentified food samples. You will use chemical reagents to test the unknown for specific nutrients. By comparing the color change a reagent produces in the unknown with the change it produces in the known nutrient, you can estimate the amount of that nutrient. Use small samples.

MATERIALS:

400-ml beaker
Hot plate
8 test tubes
Test tube rack
4 medicine droppers
Glass stirring rod
Tongs
Several unknown food substances
Glucose
Cornstarch
Non-fat dry milk
Lard
Distilled water
Benedict’s solution
Iodine-potassium iodide solution
10% aqueous sodium hydroxide solution
0.5% Copper sulfate solution
Sudan III solution

PROCEDURE:

Monosaccharide (simple sugar) test

1. Fill a 400-ml beaker to about 300 ml with water and heat on the hot plate.

Be sure to label all test tubes.

2. Place pea-sized portions of glucose and the unknown substance you are testing in separate test tubes. Add about 2.5 ml of distilled water and 10 drops of Benedict’s solution to each test tube. Mix with a stirring rod, or holding the tube between the thumb and index finger of one hand, thump it with the middle finger of the other hand to mix.

REMEMBER: If you use a stirring rod, wash it after every use, so you won’t contaminate one solution with another.

3. When the water boils, use tongs to place the test tubes in the water bath. Leave the test tubes in the water bath for 10 minutes.

Do not let the water bath boil hard. Control the boiling by turning the hot plate on and off as needed.

4. Remove the test tubes with tongs and place the tubes in a test tube rack. Unplug the hot plate to cool. When the tubes cool, an orange or red precipitate will form if large amounts of glucose are present. Small amounts of glucose will form a yellow or green precipitate. Record your observations in the DATA TABLE.

Polysaccharide complex sugar) test

5. Place cornstarch in a clean test tube and some of the unknown substance in another. Use a clean dropper to add 10 drops of iodine-potassium iodide solution to each test tube. Observe the results and record in the DATA TABLE.

Protein test

6. Place non-fat dry milk in a clean test tube and some of the unknown in another. With a clean dropper slowly add an amount of sodium hydroxide solution about equal to the amount of the milk sample, and mix carefully. Then add 10 drops of copper sulfate solution one drop at a time. Mix gently between drops. Observe the results and record in the DATA TABLE.

7. Repeat step 6 with the unknown substance.

Lipid test

8. Place a small piece of lard in a clean test tube and some of the unknown in another. Use a clean dropper to add 10 drops of Sudan III solution to each test tube. Mix well, observe and record your results in the DATA TABLE.

DATA TABLE:

Monosaccharide test		Polysaccharide test
Mark your results in the appropriate boxes. Indicate relative amount by H for high, M for medium, L for low, or 0 for none.
SUBSTANCE:	RELATIVE AMOUNT:	SUBSTANCE:	RELATIVE AMOUNT:
Unknown	Unknown
Glucose	Corn starch

Protein test		Lipid test
SUBSTANCE:	RELATIVE AMOUNT:	SUBSTANCE:	RELATIVE AMOUNT:
Unknown	Unknown
Non-fat dry milk	Lard

CONCLUSIONS:

Question 1 . What is the main nutrient in the unknown?

Question 2. What are the controls in this investigation?

Evolution Study Guide BI

Evolution Study Guide

What idea was used to explain the appearance of maggots on rotting meat?

Explain how Redi tested the hypothesis of spontaneous generation.

What did Pasteur do in his experiments on spontaneous generation that other scientists before him had not done?

What is the estimated age of the earth?

If the half-life of a radioactive isotope is 4000 years, how much will be left in a fossil after 4000 years? after 8000 years?

Does the half-life of a radioactive isotope change?

How can the age of a fossil be determined?

Which of these gases was thought by Oparin to be part of the early Earth’s atmosphere — carbon dioxide, ozone, oxygen , &/or ammonia?

Why did Miller & Urey not use oxygen in their experiment?

What organic compound did Miller & Urey make in their experiment?

Miller & Urey’s experiments were designed to show that life on Earth might have originated from what type of molecules?

Was RNA or DNA probably the first genetic molecule?

Can RNA undergo natural selection & cause evolution or change?

Do scientists think DNA or RNA was made first?

What layer protects the Earth from harmful ultraviolet rays of light?

Give 3 examples of different types of fossils.

Describe several ways in which fossils can be formed.

On what islands did Darwin conduct much of his research?

Darwin’s finches that had various types of beaks probably shared what in common with each other?

The process by which a population becomes better suited to its environment is known as what?

According to Darwin, evolution is the result of _____________ ___________.

If organisms are well suited to their environment, what will be true of their ability to reproduce?

Limited resources and a growing population results in ___________ among organisms.

Give an example of homologous structures found in the wing of a bat & the forearm of a human.

The human tailbone is an example of a __________ structure.

The beak of a bird & the beak of a giant squid have the same function and would be examples of _____________ structures.

When two or more species change in response to each other, the process is known as _____________.

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Frog Dissection

Frog Dissection
Pictures: Modern Biology, Holt

Background:
As members of the class Amphibia, frogs may live some of their adult lives on land, but they must return to water to reproduce. Eggs are laid and fertilized in water. On the outside of the frog’s head are two external nares, or nostrils; two tympani, or eardrums; and two eyes, each of which has three lids. The third lid, called the nictitating membrane, is transparent. Inside the mouth are two internal nares, or openings into the nostrils; two vomerine teeth in the middle of the roof of the mouth; and two maxillary teeth at the sides of the mouth. Also inside the mouth behind the tongue is the pharynx, or throat.

In the pharynx, there are several openings: one into the esophagus, the tube into which food is swallowed; one into the glottis, through which air enters the larynx, or voice box; and two into the Eustachian tubes, which connect the pharynx to the ear. The digestive system consists of the organs of the digestive tract, or food tube, and the digestive glands. From the esophagus, swallowed food moves into the stomach and then into the small intestine. Bile is a digestive juice made by the liver and stored in the gallbladder. Bile flows into a tube called the common bile duct, into which pancreatic juice, a digestive juice from the pancreas, also flows. The contents of the common bile duct flow into the small intestine, where most of the digestion and absorption of food into the bloodstream takes place.

Indigestible materials pass through the large intestine and then into the cloaca, the common exit chamber of the digestive, excretory, and reproductive systems. The respiratory system consists of the nostrils and the larynx, which opens into two lungs, hollow sacs with thin walls. The walls of the lungs are filled with capillaries, which are microscopic blood vessels through which materials pass into and out of the blood. The circulatory system consists of the heart, blood vessels, and blood. The heart has two receiving chambers, or atria, and one sending chamber, or ventricle. Blood is carried to the heart in vessels called veins. Veins from different parts of the body enter the right and left atria. Blood from both atria goes into the ventricle and then is pumped into the arteries, which are blood vessels that carry blood away from the heart.

The urinary system consists of the frog’s kidneys, ureters, bladder, and cloaca. The kidneys are organs that excrete urine. Connected to each kidney is a ureter, a tube through which urine passes into the urinary bladder, a sac that stores urine until it passes out of the body through the cloaca. The organs of the male reproductive system are the testes, sperm ducts, and cloaca. Those of the female system are the ovaries, oviducts, uteri, and cloaca. The testes produce sperm, or male sex cells, which move through sperm ducts, tubes that carry sperm into the cloaca, from which the sperm move outside the body. The ovaries produce eggs, or female sex cells, which move through oviducts into the uteri, then through the cloaca outside the body.

The central nervous system of the frog consists of the brain, which is enclosed in the skull, and the spinal cord, which is enclosed in the backbone. Nerves branch out from the spinal cord. The frog’s skeletal and muscular systems consist of its framework of bones and joints, to which nearly all the voluntary muscles of the body are attached. Voluntary muscles, which are those over which the frog has control, occur in pairs of flexors and extensors. When a flexor of a leg or other body part contracts, that part is bent. When the extensor of that body part contracts, the part straightens.

Objectives:
• Describe the appearance of various organs found in the frog.
• Name the organs that make up various systems of the frog.

Purpose:
In this lab, you will dissect a frog in order to observe the external and internal structures of frog anatomy.

Materials:
• safety goggles, gloves, and a lab apron
• forceps
• preserved frog
• dissecting pins (6–10)
• dissecting tray and paper towels
• plastic storage bag and twist tie
• scissors
• marking pen
• dissecting needle

Procedure:

Put on safety goggles, gloves, and a lab apron.
Place a frog on a dissection tray. To determine the frog’s sex, look at the hand digits, or fingers, on its forelegs. A male frog usually has thick pads on its “thumbs,” which is one external difference between the sexes, as shown in the diagram below. Male frogs are also usually smaller than female frogs. Observe several frogs to see the difference between males and females.

Use the diagram below to locate and identify the external features of the head. Find the mouth, external nares, tympani, eyes, and nictitating membranes.

Turn the frog on its back and pin down the legs. Cut the hinges of the mouth and open it wide. Use the diagram below to locate and identify the structures inside the mouth. Use a probe to help find each part: the vomerine teeth, the maxillary teeth, the internal nares, the tongue, the openings to the Eustachian tubes, the esophagus, the pharynx, and the slit-like glottis.

Look for the opening to the frog’s cloaca, located between the hind legs. Use forceps to lift the skin and use scissors to cut along the center of the body from the cloaca to the lip. Turn back the skin, cut toward the side at each leg, and pin the skin flat. The diagram above shows how to make these cuts
Lift and cut through the muscles and breast bone to open up the body cavity. If your frog is a female, the abdominal cavity may be filled with dark-colored eggs. If so, remove the eggs on one side so you can see the organs underlying them.
Use the diagram below to locate and identify the organs of the digestive system: esophagus, stomach, small intestine, large intestine, cloaca, liver, gallbladder, and pancreas.

Again refer to the diagram below to identify the parts of the circulatory and respiratory systems that are in the chest cavity. Find the left atrium, right atrium, and ventricle of the heart. Find an artery attached to the heart and another artery near the backbone. Find a vein near one of the shoulders. Find the two lungs.

Use a probe and scissors to lift and remove the intestines and liver. Use the diagram on the next page to identify the parts of the urinary and reproductive systems. Remove the peritoneal membrane, which is connective tissue that lies on top of the red kidneys. Observe the yellow fat bodies that are attached to the kidneys. Find the ureters; the urinary bladder; the testes and sperm ducts in the male; and the ovaries, oviducts, and uteri in the female.

Remove the kidneys and look for threadlike spinal nerves that extend from the spinal cord. Dissect a thigh, and trace one nerve into a leg muscle. Note the size and texture of the leg muscles.
Dispose of your materials according to the directions from your teacher.
Clean up your work area and wash your hands before leaving the lab.

Click here for worksheet

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