Curriculum Map 92 - 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.

Fimbriae Article

Fimbriae, Fibrils, Sex and Fuzzy Coats

The Limitation of Light

One of the frustrating aspects of working with bacteria is that they are so small that it is almost impossible to see anything other than their shape when looking down even the very best of optical microscopes. Even then, their refractive index is so similar to that of water that they have to be stuck to a glass slide, killed and stained before even their shape is revealed. Microscopes which can make use of polarized light (Phase contrast microscopy) can be used to see living bacteria but apart from the added ability of seeing some species happily swimming around they add little to what we can see using conventional staining techniques.

The fact that some species could move quite rapidly intrigued many early microbiologists and eventually some special staining procedures lead to the discovery of thin whip-like appendages which they called flagellae and conferred motility. This is not to say that light microscopy is not useful. It remains an essential tool in any bacteriology laboratory but it should be recognized that the information obtained, although extremely helpful in routine work, is limited.

Electron Microscopy Reveals More

The invention of the electron microscope revealed much more detail of bacteria. Compared to the fascinating structures uncovered in eukaryotic cells, bacteria, both inside and out, were pretty uninteresting. It wasn’t until the early 1960s that some interesting surface features of some bacterial species were noticed. This delay was partly due to the electron microscopy techniques in use at that time. The convention at the time was to use ultra-thin sections of tissue, far thinner than sections used for light microscopy. It seemed normal then to prepare bacteria in the same way. Using these techniques, the outer surfaces of bacteria seemed fairly barren but the technique did reveal some of the double membrane-like composition of Gram-negative bacteria.

Shadow-Casting Reveals Still More

Although thin sections of bacteria did not allow flagella to be seen in their entirety it did reveal interesting cross-sections which showed their internal structure. It also enabled detail of flagella attachment to be demonstrated. It was not until electron microscopes were used to look at whole cells rather than ultra-thin sections that more progress was made. This change required the development of new staining techniques known as shadow-casting where bacterial surfaces were sprayed with electron-dense material such as gold or carbon at an angle. This highlighted the fine surface structures in a way exactly analogous to light falling on a stone surface at an angle reveals more detail than light falling on it at right angles.

Shadows, Flagellae and Fimbriae

Once shadow-casting techniques had been developed the whip-like flagellae were the first to be examined in detail but one researcher in particular noticed the presence of previously undreamed of structures on the surface of some species. The person who first described these structures which he found on strains of Escherichia coli and Salmonella was Professor James Duguid. He called them fimbriae.

What are Fimbriae?

Fimbriae are thin, hair-like, projections made of protein sub-units. A number of different types have been described (about 7 at the last count, labeled Types I-VII) which can be distinguished by their size (length and diameter) and the type of antigens they carry. They are characteristic of some Gram-negative bacteria such as Escherichia coli and Salmonella spp and were first described back in the 1960s by JP Duguid who was the Professor of Microbiology at the University of Dundee . Later, it was discovered that these fimbriae would re-grow after they had been broken off e.g. by vigorous shaking and that this re-growth was from pre-formed protein sub-units which were stored inside the cells. Fimbriae originate in the cytoplasm of the cell and project through the cell membrane and the cell wall.

A Controversy

A short while after Duguid published his findings an American called Robert Brinton published much the same stuff and called them pili. What followed was a pretty acrimonious exchange of letters in the scientific press about what they should be called.

It was all pretty good fun but to this day our American cousins, and anybody who doesn’t know any better, call them pili whereas all right-thinking, clear-minded and fair microbiologists refer to them as fimbriae.

So What do Fimbriae Actually do?

Over the years we have learned quite a lot about fimbriae and right from the very early days it was thought that they were involved in helping the bacteria adhere to surfaces. There is now a substantial body of evidence in support of this much of it in relation to pathogenic strains of E coli.

Type I Fimbriae are Pathogenicity Factors

It’s clear these days that Type I fimbriae are involved in bacterial adhesion and the very best example are those carried by pathogenic strains of E.coli. These come in a variety of forms including plain old EnteroPathogenic E.coli (EPEC), EnteroToxigenic E.coli (ETEC), EnteroInvasive E.coli (EIEC) and VeroToxogenic E.coli (VTEC). These E.coli strains use Type I fimbriae to adhere to gut mucosal cells which is the first step in the pathogenic process. Without the fimbriae their capacity to cause disease is greatly diminished or abolished completely.

Type IV fimbriae are particularly interesting. These have also been referred to as “bundle forming pili” because of their ability to aggregate into bundles. These fimbriae are thought to be connected with the ability of EPEC strains to form microcolonies on tissue monolayers and mutants lacking this ability show reduced virulence. Type IV fimbriae have also been shown to be involved in the remarkable phenomenon of bacterial twitching motility which allows bacterial cells to crawl over a surface.

Type VII Fimbriae, Viruses and the Sex Bit

Type VII fimbriae are the conduit for DNA transfer between bacterial mating strains. As it happens they also provide a binding site for certain bacteriophages. The significance of this is a mystery but it does enable Type VII to be seen clearly because when some of the bacteriophage is added to a suspension of cells, the ‘phage coat the Type VII fimbriae. In the electron microscope picture above right you can clearly see little particles stuck on two of the fimbriae which are much longer than the rest because size does matter, at least to E.coli. In a generous attempt to resolve the fimbriae/pili argument it was proposed that Type VII fimbriae were named the “sex pilus”.

Sex Pili

The photograph above was taken using a transmission electron microscope. The Type I fimbriae are the thin projections sticking out from the surface of the cell. Some of the fimbriae have broken off indicating that they are quite brittle.

Surfaces of Streptococci

Back in the days before we knew much about fimbriae researchers looking at ultra-thin sections of the serious pathogen Streptococcus pyogenes noticed that the very outside of the cells had a fuzzy appearance. In a fit of imagination it was called “fuzzy coat”. Later, when they learned about shadow-casting whole cells they applied this technique but it did not help to resolve any particular structures like fimbriae.

S. pyogenes Fuzzy Coat

Even today we have not resolved any definite structure to the S. pyogenes “fuzzy-coat”. We do know, however, that it consists partly of a substance called “M-protein” which is a major pathogenicity factor of this species.

Negative Staining Reveals Surface Fibrils on Some Streptococci

Towards the late 1970s a rather different technique which made use of a special type of stain called a “negative stain” revealed very thin, delicate, hair-like structures on some oral streptococci such as Streptococcus sanguis and Streptococcus salivarius. Take a look at the photograph on the right. This is an electron micrograph of the surface of a Streptococcus salivarius cell and although it may not be terribly clear on this reproduction, the original shots showed two types of these thin hair-like structures, long ones and short ones. This negative-staining technique could not, by the way, reveal anything hair-like on the surface of Streptococcus pyogenes which had the fuzzy coat.

Fibrils are not Fimbriae

More research using lots of different strains of different species of oral streptococci showed these “hairs” came in all sorts of lengths and some cells carried more than one type. They were very thin and flexible. Although some fimbriae on E.coli can be very thin, “flexible” is not a term normally associated with fimbriae. To begin with these hairs were called “fibrils” and there is a fair amount of evidence to suggest they are made of protein and some evidence which suggests that some are even made of glycoprotein although glycoproteins are generally considered pretty rare beasts in bacteria. As far as fibril synthesis goes, we don’t know much. Generally speaking they are difficult to remove, probably because they are so flexible, so it’s not possible to say whether they can re-grow like fimbriae. The analogy was taken a stage further when a role in adhesion was postulated and, in fact, there is fairly good evidence to back this up, at least for the S.salivarius fibrils.

Unfortunately at this point the waters got a bit muddy when some people started referring to the long fibrils as “fimbriae” and the short ones as “fibrils”. Since they are kind of like fimbriae this wasn’t so surprising but what was surprising was that they were never referred to as pili!

Streptococcal Fibrils

Some Oral Streptococci Have Tufts of Fibrils

Some strains of oral streptococci were found to carry tufts of fibrils and looked rather like punk-rockers with Mohican hairstyles. Later these were grouped together into a new species and given the rather elegant name Streptococcus cristae.

Fibril Tufts and Co-aggregation

There is evidence that these may also be involved in adhesion, this time to rod-shaped bacteria to make the structures commonly found in mature dental plaque called “corn-cob-configuration”. When bacteria of the same species stick to each other it’s known as “aggregation”. In this case the bacteria are from different species and it’s known as “CO-aggregation”.

“Corn Cobs” in Dental Plaque

And finally

You may have guessed by now that I’m a bit skeptical about using the term “fimbriae” to describe the surface structures of these oral streptococci. I prefer to describe them all as fibrils but I’ll probably end up in the minority. Sooner or later this is all going to be resolved but for the time being it’s probably best to keep the term “fimbriae” reserved for those brittle hair-like, proteinaceous surface projections of Gram-negative rods like Escherichia and Salmonella and call everything else “fibrils”.

Just remember pili are fimbriae and fibrils are different and you won’t go far wrong.

SUMMARY
1.	Fimbriae are appendages which have been seen on the surfaces of a range of Gram-negative rods such as E.coli and various species of Salmonella
2.	Fimbriae come in 7 different types (I-VII) distinguished by their length and width
3.	Fimbriae are thought to be important in adhesion and have been shown to be pathogenicity factors in pathogenic strains of E.coli.
4.	Type VII fimbriae allow DNA transfer between mating strains of certain species such as E.coli
5.	Fibrils are found on streptococci
6.	Fibrils are different from fimbriae, they are thinner and appear to be more flexible
7.	Some fibrils have been shown to function in adhesion e.g. in corn-cob-formations found in dental plaque

http://www.ncl.ac.uk/dental/oralbiol/oralenv/tutorials/fimbriae.htm

Energy in Food Writeup

Energy in Food Write Up

Introduction:

Use your lab and your textbook to locate and include the following information in your introduction.

What organisms are capable of making their own food?
What process do they use to do this?
Where do these organisms get their energy for food-making?
This energy is captured with the help of what pigment?
This energy is stored in what organic molecules?
Where exactly in the organic molecules is the energy stored and so it can be used again later? (Hint: Energized electrons form these and then energy is released again when they are broken.)
What process takes place in plants & animals to release energy?
What gas is required for the process to occur?
When foods are “burned” in our bodies, where is the energy being released from? Where did this energy originally come from?
What is the usable form of energy for our cells?
Define calorimetry and explain how it can be used to measure energy stored in chemical bonds of food.

Hypothesis:

Write a statement explaining that calorimetry can be used to detect the amount of energy stored in the chemical bonds of foods.

Materials:

In sentence form, write a statement listing the materials required for this lab.

Procedure:

In paragraph form, write the procedures for completing this lab.

Results:

Draw and fill in table 1 showing the results of burning
Draw and fill in table 2 showing your data analysis for nut calorimetry
Write out and answer the questions on the lab. Remember to write and underline the question, but do NOT underline the answer.

Conclusion: (Write in paragraph form.)

Restate your hypothesis.
Tell how were you able to measure the amount of energy in each nut
Did all three nuts contain the same amount of food energy? Explain by giving data from your experiment..
Explain why some foods contained more energy than others
Tell where this energy originally come from and how it got into the nuts
Explain any errors you might have made in lab that could have affected your results

Ecology Worksheet Bi

Ecology

Chapter 19 Ecology

1. What is ecology?

2.. What is the most significant environmental change that is taking place today?

3. What is the sixth mass extinction?

4. What is the ozone layer, what does it do for earth, & what is happening to this layer & why?

5. Explain the green house effect.

6. List in order the ecological levels of organization.

7. What is the biosphere, tell where it extends, & tell why it is so important?

8. Define ecosystems & give an example.

9. What is a community?

10. What is a population?

11. What is the simplest ecological level of organization?

12. Use figure 19-6 on page 364 & explain how Lyme disease affects organisms in an ecosystem.

13. What are biotic factors & list them?

14. What are abiotic factors & list them?

15. Are abiotic factors constant? Explain by giving an example.

16.Organisms are able to survive within a _____________ range of environmental conditions.

17. Graphing the range of conditions an organism can survive is called a __________________ Curve.

18.When organisms adjust their tolerance to abiotic factors, the process is called ___________.

19. Explain how dormancy & migration help organisms escape unsuitable environmental conditions.

20. Define niche

Chapter 20 Populations

21. What is meant by population size?

22. What is meant by population density?

23. Name the 4 processes that determine whether a population will grow, shrink, or remain the same size.

24. What are immigration & emigration & how do they affect population size?

25. What are limiting factors & give some examples?

26. What affect does inbreeding have on small populations?

Chapter 21 Community Ecology

27. Interactions among species are called ____________.

28. List the 5 types of symbioses.

29. Define predator & prey & give an example.

30. What is mimicry & give an example?

31. Define these terms — parasitism, parasite, host, ectoparasites, & endoparasites.

32. When niches overlap, _________________________ results so more than one species are using the limited resources.

33. What are mutualism & commensalism?

34. Define succession.

35. Name & describe the 2 types of succession.

36. What are pioneer species & why are they important?

37. What is a climax community?

Chapter 22 Ecosystems

38. What are producers & what is another name they may be called?

39. What is biomass, why is it important, how does it accumulate, & what is its rate of accumulation called?

40. What is gross primary productivity?

41. All heterotrophs would be ______________________.

42. Define & give an example of each of these consumers — herbivore, carnivore, omnivore, detritivores, & decomposer.

43. Whenever one organism eats another, ________________ is transferred.

44. What are trophic levels?

45. All _______________ belong to the first trophic level, _______________ belong to the
Second trophic level, and the _______________ of herbivores belong to the third trophic level.

46. How many trophic levels do most ecosystems contain?

47. What is a food chain & what always begins the chain?

48. Write an example of a food chain.

49. What is a food web?

50. Draw a diagram of a food web that has at least 4 food chains.

51. Approximately __________ percent of the total energy consumed at one trophic level is incorporated into the organisms in the next level.

52. In terms of energy passage, why will there be many more producers than herbivores and fewer large carnivores than small carnivores?

53. What are biogeochemical cycles, why are they important, & name three?

54. Draw & explain the water cycle. Be sure to color your diagram!

55. List & define the 3 important processes in the water cycle.

56. What is groundwater?

57. What 2 processes form the basis for the carbon cycle?

58. Draw & explain the carbon cycle. Be sure to color your diagram!

59. What purpose do decomposers have in the carbon cycle?

60. Why do organisms need nitrogen?

61. Draw & explain the nitrogen cycle. Be sure to color your diagram!

62. Organisms such as ________________ convert _________________ gas into compounds
Called __________________ during the process known as________________________.

63. Bodies of dead organisms contain mainly in _________________ & _________________.

64. Wastes such as __________________ & _______________ also contain nitrogen that must be recycled.

65. ________________ recycle nitrogen from dead organisms & wastes by changing it into
______________________. The process is called ________________________.

66. Explain nitrification & denitrification.

67. Plants can absorb ____________________ from the soil, but animals obtain nitrogen from
their ___________________.

68. Define biome.

69. List the 7 major biomes.

70. Why don’t mountains belong to any one biome?

71. What is a tundra, where are they found, & tell organisms that would be found tree?

72. What is permafrost & how does it control plant life in the tundra?

73. What are taigas, where would they be found, & what type of vegetation dominates this area?

74. Plants & animals in the taiga must be adapted for long __________________, short
_________________, & ________________________ soil.

75. List some typical animals of the taiga.

76. What characterizes a temperate deciduous forest?

77. Deciduous forests have 4 pronounced ____________________ with _________________
summers, _______________________ winters, and__________________________ than the
taiga.

78. Grasses dominate what biome?

79. Why aren’t there more trees on grassland?

80. What are grasslands called in each of these areas —– North America, Asia, South America, & southern Africa?

81. Describe the soil of grasslands. Because of the soil condition, how is much of the grassland used?

82.What type of animals would be found on grassland?

83. What periodically occurs across grasslands & why doesn’t it kill the grasses?

84. Approximately how much rainfall do deserts receive each year?

85. Are deserts always hot? Explain.

86. What adaptation must desert vegetation make to survive?

87. What types of adaptations must desert animals make to conserve water?

88. What are savannas & where are the best known savannas found?

89. Describe temperature & rainfall on savannas?

90. Name some herbivores & carnivores found on a savanna.

91. Describe the rainy season on a savanna & tell what special problem this poses for the animals & plants there?

92. What are tropical rain forests & where are they located?

93. Rain forests have stable, year-round ______________________ & abundant ____________.

94. Plants in the rainforest must constantly compete for what?

95. Explain the canopy & epiphytes in a rainforest.

96. Describe the plant & animal life in a rainforest.

97. Tropical rainforests are more commonly called _____________________.

98.Oceans cover what percent of the earth’s surface?

99. Draw, label, & color the zones found in the ocean (see figure 22-16). Define each term labeled on your drawing.

100. What are intertidal organisms exposed to & name some intertidal organisms.

101. Which zone in the ocean is the most productive & why?

102. What small organisms are found in the neritic zone & why are they important?

103. In tropical areas, what forms in the neritic zone & why are they important?

104. Which ocean zone has fewer species & why?

105. Where does most of the earth’s photosynthesis take place?

106. Animals in the aphotic zone feed on what?

107. Organisms living deep in the ocean must cope with what 2 problems? Give some examples of deep ocean animals & explain how they adapt to their environmental problems.

108. What are volcanic vents, when were they discovered, & describe the organisms found there?

109. What are estuaries & what special problem do estuary organisms face?

110. What characterizes freshwater zones & give several examples?

111. Name & describe the 2 categories into which ecologists divide lakes 7 ponds?

112. Define a river & describe organisms found there?

Chapter 23 Environmental Science

113. Where do upwellings occur & how are they helpful?

114. Describe the event known as El Nino & tell its effect.

115. Describe chlorofluorocarbons effect on the ozone layer & tell why we should be concerned?

116. Define biodiversity.

117. Define conservation biology & use migratory birds to explain an example of this new discipline?

118. Sometimes species are reintroduced into areas. Use the Gray wolf & describe its reintroduction in the United States.

119. Where are the Everglades located & what is being done to restore them?

BACK

Earthworm Facts

earthworm facts

How long do worms live?
How many young are produced per year?
Do earthworms have eyes?
How do earthworms breathe?
Can earthworms smell?
Do worms have eyes?
What do earthworms eat and how much can they eat in one day?
Can earthworms freeze?
What is the “bump” in the middle of the earthworm?
How can you determine if an earthworm is sexually mature?
Can earthworms lose their clitellum?
How do earthworms mate?
How are cocoons produced?
How long does it take worms to hatch?
How many young worms are produced per y ear?
How long does it take earthworms to mature?
Can different species of worms mate creating a hybrid worm?
How long do earthworms live?
How do earthworms move?
What characteristics are used to identify earthworms?
What enemies do earthworms have?
Can earthworms regenerate themselves?
How can you distinguish the head of an earthworm from the tail?
How do earthworms obtain their food?
How big do earthworms get?

Read Our Q&A About Earthworm Facts

Q. How long do dew worms live?

A. Dew worms can live for approximately six and a half years.

Q. How many young are produced per year?

A. It is estimated that sexually mature dew worms (about one year old) produce about two cocoons per year with 1-2 young each (more research under field and laboratory conditions required).

Q. Do earthworms have eyes?

A. They do not have eyes but they do possess light- and touch-sensitive organs (receptor cells) to distinguish differences in light intensity and to feel vibrations in the ground.

Q. How do earthworms breathe?

A. Earthworms respire through their skin, and therefore require humid conditions to prevent drying out. They coat themselves in mucus to enable the passage of dissolved oxygen into their bloodstream.

Q. Can earthworms smell?

A. Worms have specialized chemoreceptors or sense organs (“taste receptors”) which react to chemical stimuli. These sense organs are located on the anterior part of the worm.

Q. What do earthworms eat and how much can they eat in one day?

A. Earthworms derive their nutrition from many forms of organic matter in soil, things like decaying roots and leaves, and living organisms such as nematodes, protozoans, rotifers, bacteria, fungi. They will also feed on the decomposing remains of other animals. They can consume, in just one day, up to one third of their own body weight.

Q. Can earthworms freeze?

A. Like all invertebrates their body processes or metabolism slow down with falling temperatures. They will hibernate at near freezing temperature. If frozen they will die. They react to advancing colder winter weather by burrowing deep (up to two meters) in the soil to avoid the extreme cold.

Q. What is the “bump” in the middle of the earthworm?

A. The bump is the clitellum, the saddle shaped swollen area 1/3 of the way back containing the gland cells which secrete a slimy material (mucus) to form the cocoon which will hold the worm embryos.

Q. How can you determine if an earthworm is sexually mature?

A. If the worm has a clitellum, it is sexually mature.

Q. Can earthworms lose their clitellum?

A. The answer is yes! During periods of drought, when soils dry up, some species of earthworms do in fact temporarily lose all secondary sexual characters such as the clitellum. When conditions become favorable, it comes back. The clitellum can also disappear at the onset of old age or senescence.

Q. How do earthworms mate?

A. Earthworms are hermaphroditic meaning each worm has organs of both sexes. The male gonopores are usually within the first 12-15 segments, and the female gonopores are further back, close to the clitellum (the swollen area in adult worms). One worm has to find another worm and they mate juxtaposing opposite gonadal openings exchanging packets of sperm, called spermatophores. Some species also appear to be either parthenogenetic (females producing all females, “virgin birth”) or may be able to self-fertilize.

Q. How are cocoons produced?

A. The clitellum produces a mucous sheath and nutritive material, and as the sheath slides forward, it picks up ova from the earthworm’s ovaries then packets of sperm that had been transferred to the worm from another worm during mating. As the sheath slides off the worm’s head, the ends are sealed to form the cocoon. Initially, the cocoon is quite soft but soon after it is deposited in the soil it becomes slightly amber in color, leather-like and very resistant to drying and damage.

Dendrobaena rubidus cocoons (relative to a pin head).

The ova within each cocoon are fertilized, and the resulting embryos grow inside the sealed unit, much like a chick developing inside an egg. When the embryos have consumed all the nutritive material, they completely fill the lemon shaped cocoon and are ready to hatch out one end.

Q. How long does it take worms to hatch?

A. Young worms hatch from their cocoons in three weeks to five months as the gestation period varies for different species of worms. Conditions like temperature and soil moisture factor in here…if conditions are not great then hatching is delayed.

Q. How many young worms are produced per year?

A. Earthworms can produce between 3 and 80 cocoons per year depending on the species. The deeper-dwelling species don’t have to produce as many cocoons because they are protected much better from predation than surface dwelling species which tend to produce many more cocoons. The number of fertilized ova or eggs within each cocoon ranges from one to twenty. This depends on the species and also factors such as nutrition of the adults laying them and environmental conditions with soil moisture being most important. Usually, though, only few to several young worms will ever successfully emerge from each cocoon.

Q. How long does it take earthworms to mature?

A. Worms mature in 10 – 55 weeks depending on the species.

Q. Can different species of worms mate creating a hybrid worm?

A. No, this does not usually occur; hybrids can usually only occur between very closely related species and their offspring would likely be infertile.

Q. How long do earthworms live?

A. Earthworm longevity is species dependent. Various specialists report that certain species have the potential to live 4-8 years. In protected culture conditions (no predators, ideal conditions) individuals of Allolobophora longa have been kept up to 10 1/4 years, Eisenia foetida for 4½ years and Lumbricus terrestris for 6 years.

Worms continue to grow once they reach sexual maturity but once at this stage there is a much slower increase in weight until the disappearance of the clitellum indicates the onset of old age or senescence. During this period there is a slow decline in weight until the death of the worm.

Q. How do earthworms move?

A. Earthworms have bristles or setae in groups around or under their body. The bristles, paired in groups on each segment, can be moved in and out to grip the ground or the walls of a burrow. Worms travel through underground tunnels or move about on the soil surface by using their bristles as anchors pushing themselves forward or backward using strong stretching and contracting muscles.

Q. What characteristics are used to identify earthworms?

A. The external body characters used in identifying different species of earthworms are: the segmental position of the clitellum on the body, body length, body shape (cylindrical or flattened), number of body segments, type and position of body bristles or setae, the description of the tongue-like lobe, the prostomium, projecting forward above the mouth, type of peristomium or first body segment, external position and morphology of genital apertures or opening and type of glandular swellings on the clitellum. The shape and the relationship of various internal organs are also used to identify some species of worms.

Q. What enemies do earthworms have?

A. Snakes, birds, moles, toads and even foxes are known to eat earthworms. Beetles, centipedes, leeches, slugs and flatworms also feed on earthworms. Some types of mites parasitize earthworm cocoons and the cluster fly (Pollenia rudis) parasitizes worms of the species Eisenia rosea.

Q. Can earthworms regenerate themselves?

A. Yes, but only the front or head end of the earthworm will survive and the amputated tail portion will die. This remaining front portion must also be long enough to contain the clitellum and at least 10 segments behind the clitellum. This makes up about half the length of the worm. The new posterior segments grown will be slightly smaller in diameter than the original segments and sometimes a bit lighter in color.

Q. How can you distinguish the head of an earthworm from the tail?

A. The head of the worm is always located on the end of the worm closest to the clitellum and has some differentiated structures if you can view with magnification. Even though worms can move both frontward and backward they tend to travel forward more. Place a worm on a rough piece of paper and observe which direction it travels. They usually extend their “head” first when crawling.

Q. How do earthworms obtain their food?

A. Earthworms possess very strong mouth muscles – they do not have teeth. Dew worms or nightcrawlers often surface at night to pull fallen leaves down into their burrow. When the leaf decomposes or softens a little they pull small bits off at a time to munch on. They also “swallow” soil as they burrow and extract nutrients from it.

Q. How big do earthworms get?

A. Size depends on the species of worm, it’s age, diet and environmental conditions like moisture, temperature and soil conditions. Lumbricus terrestris (Nightcrawler, Dew worm) is one of North America’s largest and ranges in size from 9-30 cm with a diameter of 6-10 mm. The largest L. terrestris we’ve collected was close to 30 cm long (stretched out), weighed 11.2 g and was collected in a no-till, soybean field in Ontario up near Georgian Bay, Ontario.

The largest tropical species (Glossoscolex and Megascolides) are up to 120 cm long and the largest in the world are some Australian forms which may reach 300 cm in length. Bimastos parvus (American bark worm) is quite small at less than 2 cm long.

BACK