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Biology
Biology
Lab and Activity
Lab and Activity
Table of Contents
Biology: Content Targets...4
Biology Process Targets...8
Guidelines for Writing a Formal Lab Report...9
Checklist: Parts of an Abstract...11
Lab 1 Super Meal Worms...13
Lab 2 Chemistry of Carbohydrates...17
Lab 3 Cut Out Lab –Fats and Proteins...24
Lab 4 Macromolecule Food Testing...31
Lab 5 Enzyme-Substrate Model Lab...33
Lab 6: Enzymes are our Friends...36
Lab 7 Salivary Amylase and Starch Digestion Lab...39
Lab 8 Temperature and Enzymes...40
Lab 9 The Incredible Edible Enzyme Lab...41
Lab 10 Radioactive half-life lab...43
Lab 11 History of Everything!...44
A reading: On the Origin of Species
...46
Lab 12 Variation in a Population...50
Lab 13 Microscope Lab...52
Lab 14 Form Function Lab...54
Lab 15 Why are cells small?...55
Sex and the Origins of Death
...61
Sex and the Origins of Death Questions:
...67
Lab 17 Cell Membrane Model...68
Lab 18 Onion Cell Plasmolysis (Elodea also)...70
Lab 19 Egg Lab...71
Lab 20 A time for Osmosis...73
An Alternative textbook on Cancer Biology...74
Lab 21 Mitosis Slide Lab...79
Lab 22 Mitosis Simulation Lab...80
Lab 23 Mitosis Flip Book...83
Lab 24 Who needs sunscreen anyway?...84
It is Not About the Bike
...86
Questions it is Not about the Bike – Lance Armstrong
...104
Lab 25 Bacteria Everywhere...105
Gram Staining Prelab Questions: Lab 26
...106
Lab 26 Gram Staining...107
The great influenza reading
...109
The Great Influenza Questions
...118
Lab 27 Murder 101 Antibiotics...119
Germs that do the body good
...122
Questions Germs That Do a Body Good questions to reading
...127
Lab 28: Why take all your Meds:...128
The killers Within
...130
The Killer Within Reading Questions
...139
Why is AIDS Worse in Africa?
...140
Questions: Why is AIDS worse in Africa?
...144
Lab 29 Fermentation...145
Lab 30 Carbon Dioxide and Respiration...147
Lab 31 Chromatography Lab...150
Lab 32 Photosynthesis and Respiration in Leaves...152
Lab 34 Isolation of DNA...154
Lab 35 DNA Building a Paper Model of DNA...155
DNA AND RNA...156
Lab 36 Gel Electrophoresis...158
Lab 37 GMO-A Transformation...161
Reading The DNA Transformation of a Bacteria Cell-Background pglo
...163
Lab 38 Fruit Flies...171
Lab 38 Testing Mendel’s Ideas...173
CHROMOSOME 9
(questions at end)
...177
Carlos and Mollie Can Have a Perfectly Healthy Baby (or can they?)
...181
Lab 40 Blood Typing-Transfusion-Good, bad not Ugly...186
Lab 41 Simulation of Meiosis...191
Lab 42: The Human Menstrual Cycle...193
Intentionally left blank...199
Lab 43 Early Embryo Slide Development: The Chicken...200
Lab 44 Starfish Slide Development...201
Lab 45 Sand Dollar’s Live Fertilization...202
Lab 46 Understanding the Gaps in Fossil Record: Whale Fossils...206
Lab 48 Why Don’t Whales Have Legs?...212
Lab 49 Interpretation of Human Fossils-Physical Anthropology...213
Lab 50 Physical Anthropology-Learning about our Early Ancestors using Skulls...215
Reading: 2% Difference
...221
Before 'Lucy,' There Was 'Ardi': Analysis Of an Early Hominid
...224
ARDI Early Hominid First Walked On Two Legs In The Woods
...225
Lab 51 Profile of a Mammal...227
Biology: Content Targets
Biochemistry
I get it
I kind of get it
I need more help
Explain how the existence of living
things is dependent on the chemical
and physical characteristics of water.
Describe how the chemistry of carbon
gives organic compounds their
characteristics.
Describe the structure and function of
carbohydrates, lipids, proteins, and
nucleic acids
Energy & Enzymes
I get it
I kind of get it
I need more help
Describe the role played by ATP in
cells.
Define activation energy and describe
its role in chemical reactions.
Describe the interaction between an
enzyme and its substrate.
Explain how temperature and pH
affect the activity of enzymes.
Describe how inhibition controls
enzyme activity.
Cells, Cell Membrane Structure
and Function
I get it
I kind of get it
I need more help
Cell Theory
Compare and contrast prokaryotic
and eukaryotic cells.
Hypothesize how the shape (form) of
a cell is related to its function.
Describe the processes of diffusion,
osmosis, active transport and
facilitated diffusion.
Demonstrate and explain the process
of plasmolysis using Elodea in lab.
Mathematically prove that cell volume
to cell surface area ratios explain why
cells are so small.
Mitosis
I get it
I kind of get it
I need more help
Specify the number of chromosomes
in a cell before and after cell division.
Relate mitosis to the uncontrolled cell
growth occurring in tumor formation.
Compare and contrast mitosis and
meiosis.
Describe the process of apoptosis and
how it is controlled
Bacteria and Viruses
I get it
I kind of get it
I need more help
1. Describe how viruses reproduce.
2. Understand the biology of HIV
3. Explain why and how bacteria are
becoming increasingly resistant to
antibiotics.
Cellular Respiration
I get it
I kind of get it
I need more help
Explain the importance of cellular
respiration in living things.
Summarize the process of glycolysis.
Summarize the processes of aerobic
respiration occurring within the
mitochondria: the Krebs Cycle and
the electron transport system
Photosynthesis
I get it
I kind of get it
I need more help
Explain the role of chlorophyll, ATP,
NADP
, and carbon dioxide in
photosynthesis.
Describe how green plants and algae
capture energy from sunlight in the
light dependent reactions.
Describe how carbohydrates are
produced during the Calvin Cycle.
DNA
I get it
I kind of get it
I need more help
Summarize the work of Watson,
Crick, Franklin, Chargaff, and Wilkins
in determining the structure of DNA.
Compare and contrast the structure
and function DNA with RNA
Explain the process of DNA
replication, transcription and
translation.
Explain the significance of a universal
genetic code.
heterozygous, homozygous,
dominant, recessive, genotype, &
phenotype
Know how multiple alleles, polygenic
and X-linked genes/traits work
Explain the relationship between
mutation and human genetic
disorders.
Understand modern the new gene
technology
Solve monohybrid, dihybrid, multiple
allele, X-linked
Evolution
I get it
I kind of get it
I need more help
Discuss how chemical evolution
proceeded from atmospheric gases to
small organic molecules to
macromolecules to protocells.
Describe how continental drift
explains patterns of past and present
distribution of life forms and may
have contributed to episodes of mass
extinctions during the history of life.
Explain the Darwin-Wallace theory of
natural selection.
Discuss examples of natural selection
resulting in the adaptation of a
species to the environment
Reproduction and Development
I get it
I kind of get it
I need more help
Identify and explain the function of
the male and human female
reproductive systems.
Relate the events of the ovarian cycle
to the levels of LH, FSH, estrogen,
and progesterone.
Describe the process of fertilization,
cleavage and early development of
the embryo.
Human Evolution
I get it
I kind of get it
I need more help
Analyze the evidence for human
evolution – both physical and
molecular.
Explain how natural selection has
altered human history especially with
respect to the selective pressure of
disease.
primate.
Biology Process Targets
I can
do this
I kind of
get it.
I need
help.
Problem Solving
I can recongize multiple ways to solve a problem.
I can judge which problem solving method will be more effective.
I can identify flaws in the scientific method.
Experimental Design
I can design an experiment that will provide data to solve a problem.
I can isolate one variable in a complex system and manipulate that
variable.
I can identify controls in a complex systems experiment.
I can identify constants in an experiment.
Gathering Data
I can organize a variety of data.
I can choose the most concise and effective means of representing data.
I can balance trusting data with questioning data that does not make
sense.
I can adapt to using a wide variety of observation and measurement
tools.
I can identify and follow the necessary safety precautions to complete a
lab.
I can set up and use a variety of Lab Pro probes to collect data.
Interpretation of Data
I can create and use a graph with multiple trend lines.
I can extrapolate future trends from my data.
I can isolate descriptions of data from inferences of that data.
Communicate Results
I can use quantitative and qualitative means to support conclusions
drawn from data.
I can share results of my experiment concisely through a variety of
means to appropriate audiences.
Real World Applications
and trends in daily life.
I can connect distinct aspects of what I am learning to complex global
scientific issues.
Guidelines for Writing a Formal Lab Report
(modified from Pat Mote, Pace Academy, Atlanta, Georgia)
Title The title should be as short as possible but as long as necessary to communicate the purpose
of the lab.
Abstract
The abstract is a summary of the entire experiment including the problem and its
conclusions. It is placed at the beginning of the second page, after the title page. The
abstract should be no more than 250 words and should be composed after the rest of
the report is completed. (see also
http://goo.gl/SFd0Xz
)
Main Ingredients of an Abstract
Six Secrets for a Successful Abstract
1. The Problem
1.
Clear
2. The Subjects or Objects
2.
Accurate
3. The Methods
3.
Self-contained
4. The Findings
4.
Concise
5. The Conclusion
5.
Specific
6. The Implications
6.
Objective
Introduction
The introduction provides the context of the experiment. The introduction includes.
Please write in Paragraph form.
1. Purpose/problem: statement defining the experimental variables and/or the problem in the form
of a question.
2. Background information: identification of key scientific terms and explanation of theory.
3. Hypothesis - Framed as a testable statement of the outcome or “if … then” statement using
experimental and controlled variables. The hypothesis must be clearly stated in the
introduction.
Materials and Methods This section describes exactly what you did. It should be a narrative
description that integrates materials and procedures. Do not simply list materials and steps in
the procedure. The procedure is often the best place to start writing your report. Be sure to
include:
a. Control of variables and appropriate testing of the hypothesis
b.
Clear and concise experimental design (not copied from the text)
c.
Methods and materials
d.
Level of treatment, numbers of replications and controls
e.
Risks involved and suggest appropriate safety precautions.
a. Table of any qualitative observations
b. Data tables with variables, units and values clearly displayed
c. Graphs with clearly labeled variables on correct axes, appropriate range on axes, proper use of
lines
d. Calculations
Discussion
The discussion portion of the report is where the results are analyzed and interpreted. It should
include: Typically this is written in paragraphs.
a. Statement of rejection or support of hypothesis based on logical argument
supported by data
,
calculations, and observations
b. Explanation of results based on sound scientific principles (Why you observed the results?)
c. What is the significance of the results? (How do the results contribute to the reader’s knowledge
or understanding of the topic being researched?)
d. Alternative explanations evaluated
e. Reference to other work to support your ideas
f. Concluding statement related to known scientific models or theories
g. Further refinement in methods, analysis, etc. are suggested
Bibliography Any citations you made throughout your lab report should be written out in correct
form. See the library web pages for instructions.
Additional Comments
1. You should have enough understanding of the experiment to clearly defend your explanation,
methods and conclusions to peers and/or teachers.
2. Plagiarism in any form is unacceptable.
3. You must personally complete each lab in order to get credit for the formal lab reports. You
may not simply “borrow” data to write your report.
4. Any information you did not receive from the lab or in class must be cited with imbedding
citations and the full source reported in your bibliography.
Lab report writing tips- Always use a bibliography if you cite
What an in-text citation looks like: (note this like a footnote- it is not a quote but it is not your
words.
o
Pyridoxine-dependent epilepsy is a disease that involves seizures starting when someone is a
baby.(Pyridoxine NIH.gov )
o
Note do not use a long URL for a in text citation- this long URL goes in your bibliography.
http://ghr.nlm.nih.gov/condition=pyridoxinedependentepilepsy
Note: If your writing
includes 5 or more words directly copied from a source
- you need to
place all the words in quotes and use and in-text citation or footnote. “Prion protein (PrP)
plays a central role in Creutzfeldt–Jakob Disease (CJD) and other transmissible spongiform
encephalopathies (TSEs)” (McCormack 2002).
Please see
http://www.indiana.edu/~wts/pamphlets.shtml
for information on how to avoid
plagiarism. Note one can share ideas but you may not share words. Five words in a row
taken from another source without quotes is a sign of plagiarism
Do not use Wikipedia as a source for any cited work
. You can use Wikipedia as a
starting point to orient you to a topic, but I expect that you find primary research for your
written work. You should not use Wikipedia for any written research project.
Paraphrase that passage? Maybe but (this is what a student reads)
adapted from
http://gervaseprograms.georgetown.edu/honor/system/53377.html
“The population problem manifests itself not only in hunger, but also in the specter of urban
breakdown that arises from large population growth. Unemployed people pour into depressed cities such as Calcutta, stretching both the cities and the people to the breaking point as they fail to find work. As
population growth continues at a rapid pace, such places will become the very image of third-world debasement.”
What a student might write or turn in to a teacher
What the University says: This passage must end with a citation of Heilbroner. I have captured all of the main ideas in his paragraph. Although I have used "my own" words, for example, substituting the idea of "pouring" into a city rather than "streaming" into it, and substituting the word "debasement" for "degradation," my argument tracks along with his. I am making the same argument.
The fact that I changed some
words and eliminated others does not mean that this is my own work.
This example illustrates a dangerous trap for the naive or not so naive. If you were to take the Heilbroner passage into a word processor, carefully edit out some words, rearrange the order of some others, and then use the thesaurus function to look up some good synonyms for other words (as I did for degradation), you might arrive at a passage like the one I wrote.
You may think you are writing, but you are actually
assembling. Even a passage that has been "sanitized" in this way, where the resemblance to
the original comes only in the similarity of the arguments, you still must cite the original
work.
Checklist: Parts of an Abstract
Despite the fact that an abstract is quite brief, it must do almost as much work as the multi-page
paper that follows it. In a computer architecture paper, this means that it should in most cases
include the following sections. Each section is typically a single sentence, although there is room
for creativity. In particular, the parts may be merged or spread among a set of sentences.:
Motivation:
Why do we care
about the problem and the results? If the problem isn't obviously
"interesting" it might be better to put motivation first; but if your work is incremental progress on a
problem that is widely recognized as important, then it is probably better to put the problem
statement first to indicate which piece of the larger problem you are breaking off to work on..
Problem statement:
What
problem
are you trying to solve? What is the
scope
of your work (a
generalized approach, or for a specific situation)? Be careful not to use too much jargon.
Results:
What's the answer?
Specifically, most good computer architecture papers conclude that
something is so many percent faster, cheaper, smaller, or otherwise better than something else. Put
the result there, in numbers. Avoid vague, hand-waving results such as "very", "small", or
"significant."
Conclusions:
What are the implications
of your answer? Is it going to change the world (unlikely),
be a significant "win", be a nice hack, or simply serve as a road sign indicating that this path is a
waste of time (all of the previous results are useful). Are your results
general
, potentially
generalizable, or specific to a particular case?
Lab 1 Super Meal Worms
In this lab you will try to experimentally determine the place where Darkling beetles like to live.
You will design experiments, make observations, and make inferences regarding the Darkling
beetles preferences.
Background:
The Darkling beetle (
Eleodes spp) is actually a member of the family Arthropoda
which also includes shrimp and crabs.
You are working with the larva, also known as, mealworms. Mealworms will molt up to 20 times,
and their life cycle is between 3-5 months.
Your mission
is to determine what environmental conditions darkling beetle larva prefer to live in
using a choice chamber.
The first step to any good experiment is observation. Therefore you will
Observe the Darkling beetles for 5 minutes. Make notes on their general appearance, movements
around the dish, and interactions with each other. Notice if they seem to prefer one area over
another, if they keep moving, settle down, or move sporadically. Note any behaviors that involve
two or more Darkling beetles.
Try to make your observations without disturbing the
animals in any way.
Don’t prod or poke or shake the dish, make loud sounds, or subject them
to bright lights. You want to observe their behavior, not influence or interfere with it.
List at least 3 types of conditions you can design an experiment to test using a choice chamber.
For example do Darkling beetles prefer a warm or cold environment?
1.
2.
3.
Choose one condition your group would like to test and write a hypothesis:
Lab Materials
Item
Item
Item
Item
Determine what variables need to remain constant. Why?
Potential Variables
Class Sharing:
before you start to design an experiment we will share each groups hypothesis
with the class.
Individual research groups should develop a
controlled
experiment to test their particular
variable. These will be presented to the class and approved prior to the experiment.
Describe your research group’s experimental design below
:
Materials used
Variable being tested
Hypothesis
Results of your experiment: Make a data table.
Class Results:
Variable
Results
What variable demonstrates the pattern of behavior for the beetles?
Discussion Questions:
1. What was the experimental variable? How many variables changed in each trail of the experiment?
Why is this important component of an experimental design?
2. What is a control group? What was the control group in this experiment? Why are controls a vital
part of any experiment?
3. What conclusions do you draw from your data? Does the data show where the Darkling beetle
prefers to live?
4. Obtain results from all lab groups in your class. With respect to the various environmental
conditions, which types of environment do Darkling beetles prefer? How does the data support
these conclusions? Give specific examples.
5. If you suddenly, turned a rock over and found isopods under it, what would you expect them to be
doing? If you watched the isopods for a few minutes, how would you expect to see their behavior
change?
6. If you wanted to find Darkling beetles around the school, where would the data suggest you should
look? What types of environmental conditions exist where you are looking?
Discussion:
Be sure to include the hypothesis your group tested, if your experiment supported your hypothesis,
the overall class conclusion based on data, what you would improve about your experimental
design if you did it again, and what new questions this experiment generated.
Lab 2 Chemistry of Carbohydrates
Biologists today depend on the discipline of chemistry for much of their understanding of life and life processes. Thus, a foundation in the chemistry of living things (also called biochemistry) is essential. Carbohydrates make up a large group of chemical compounds found in cells. Carbohydrates are more than just an energy source; they are also vital in cellular structures.
In this investigation you will:
a) Learn to interpret the molecular formulas of some carbohydrates.
b) Use models to learn to interpret the structural formulas of some carbohydrates.
REMEMBER: Models do not represent the actual three-dimensional shapes of the molecules. Models serve to help you learn how smaller molecules can be grouped into larger, more complex molecules.
Part A: Water
Examine the chemical formula of water: H20
1. Question: What elements make up water? Answer:
2. Question: What does the number 2 following H tell you? (in H2O)
Answer:
3. Question: Why does oxygen not have a subscript? Answer:
4. Question : How many molecules of water are represented by the formula H2O?
Answer:
5. Question: What is a molecular formula? What is the molecular formula of water?
Answer:
6. Question: What is a structural formula (draw the stick-line model of water)? Answer:
7. Question: What do the lines between O and H in the structural formula of water represent?
Answer:
Part B: Carbohydrates
Carbohydrates contain three different elements: carbon (C), hydrogen (H), and oxygen (O). There are many different types of carbohydrates. They have been placed into three groups:
monosaccharides, disaccharides, and polysaccharides.
Group 1: Monosaccharides (single molecule sugars) three examples of monosaccharides are glucose, fructose, and galactose.
Examine the structural formulas for these three sugars. (See below)
1. What 3 elements are present in glucose,
fructose, and galactose?
________________________________
2. How many atoms of carbon are present in a molecule of?
Glucose? _________________
Fructose? ________________
Galactose? ______________
3. Add subscripts to the following that indicate the proper molecular formula. Do this by counting the total number of carbon, hydrogen, and oxygen atoms in each molecule.
Glucose: C__H__O__
Fructose: C__H__O__
Galactose: C__H__O__
4.How many times larger is the number of
hydrogen atoms than oxygen atoms in a molecule of.
Glucose______, Fructose _____ Galactose __________
5. How many times larger is the number of
hydrogen atoms than oxygen atoms in a molecule of water, H2O? (what is the ratio?)
________________________________ Is the number/ratio the same for monosaccharides and for water? ________________________
Monosaccharides are sugars that are made up of only one molecule, thus, they are called single sugars. The prefix “mono” means one. The one molecule, however, can have different shapes.
6. Compare the structural formula of glucose to fructose? How are same? Different?
________________________________ a. Are they exactly the same in shape?
Explain._______________________________ _____________________________
b. Are they both monosaccharides? Explain.
________________________________
Group 2: Disaccharides (double molecule
sugars)
Two monosaccharaides can join together chemically to form a larger carbohydrate molecule called a double sugar, or disaccharide. The prefix “di-“means two. By chemically joining a glucose molecule with a fructose molecule, a double sugar called sucrose is produced. Use the paper models provided to illustrate this process.Cut out glucose and a fructose paper model
Attempt to join the two to make sucrose or table sugar. Think puzzle pieces
7. Do the glucose and fructose fit easily together to form a sucrose molecule? (THINK PUZZLE PIECE) ______________ Why or why not?
______________________________________
In order to join the molecules, remove an –OH end from one molecule and an-H end from another.
Cut
along the dotted lines.
8. Does removing the –H and –OH ends now allow the molecules to fit easily together?
_________________________
9. The –H and –OH ends that were removed can also fit together with each other to form a molecule. This new molecule has a molecular formula of
_____________ and is called ___________.
10. Write the molecular formula for sucrose by adding together the molecular formulas for glucose and
fructose and then subtracting water, H2O. (Use
structural formulas for this not models.)
_______________________________
Now glue the glucose and fructose molecules on your paper with the water molecule and label the disaccharide-sucrose.
Different disaccharide molecules can be made by joining other monosaccharides in different combinations. By chemically joining a glucose
molecule with another glucose molecule, a double sugar called maltose is formed.
Cut out and attempt to join the two new glucose model molecules together like puzzle pieces which makes maltose.
11. Do the molecules fit easily together to form maltose? _______________Why or Why not? _______________________________
12. What must be removed from the two glucose model molecules so that they easily fit together? _______________________________
13. Write the molecular formula for maltose (see question 10 for directions) ___________
14. How does the molecular formula for sucrose compare to that of maltose?
_______________________________
a) How many times larger is the number of hydrogen atoms than oxygen atoms in a disaccharide?
____________________
b) How many monosaccharide molecules are needed to form one sucrose molecule?
_______________________________
c) How many monosaccharide molecules are needed to form one maltose molecule?
_______________________________
d) How do the molecules of sucrose and
maltose differ? (Refer to models in order to
answer)
___________________________________
___________________________________
___________________________________
Now glue the glucose and glucose molecules on your paper with the water molecule and label the disaccharide-maltose
Group 3: Polysaccharides (many molecule sugars) just as double sugars were formed from two single sugar molecules; polysaccharides are formed when many single sugars are joined together chemically. The prefix “poly-“means many. Starch, glycogen, and cellulose are the three most common polysaccharides in Biology. They consist of long chains of glucose molecules joined together.
Construct a physical model of a starch molecule
by joining or gluing three glucose molecules. This will represent only a small part of a starch molecule because starch consists of hundreds of glucose molecules.
15. What must be removed from the glucose model molecules in order to have them easily?
The molecular formula for a polysaccharide is written as (C6H10O5)n. The nequals the number of times the
C6H10O5 group is repeated. You can see this group as the middle glucose of your model.
15a) Why is the molecular formula for glucose in the above example C6H10O5 and not C6H12O6? (Think about
what happens when they bond)
__________________________________________________________________________
16. What is the smallest number of glucose molecules that can form a polysaccharide?
________________
___________________________________________________________
__________________________________________________________________________
17. How many times larger is the number of hydrogen atoms than oxygen atoms in a polysaccharide molecule?
___________________________________________________________
_____________________________________________________________________________
Please produce a series of attached cutouts with associated water
and key molecules on a sheet of paper
You should have and label the following
1 Glucose,
1 polysaccharide with water(s)
Name ____________
Analysis
1. Name the three categories of carbohydrates studied in this investigation.
2. What three elements are present in all carbohydrates?
3. Give the names of two monosaccharide molecules studied.
4. Give the names of two disaccharide molecules studied. How are they different?
5. Give the name of the polysaccharide studied.-how many water molecules were made in making it?
6. How do all of the above carbohydrates relate to each other?
7. How many times larger is the number of hydrogen atoms than oxygen atoms in all carbohydrates?
i. In water?
8. What molecules can combine to form disaccharides?
i. polysaccharides?
9. What ends of sugars are removed when sugar molecules join to form either disaccharides or polysaccharides?
i. What molecule do these ends form when they fit together?
Lab 3 Cut Out Lab –Fats and Proteins
Part A. Fats -Answer questions 1-6 before you cut things
On a molecular basis, all fats are somewhat similar. Just as carbohydrates are composed of
monosaccharide molecules, all fats are composed of smaller
molecules. The smaller molecules in fats are glycerol and fatty
acids.
1. Are there any elements in glycerol (look on your sheet with the cutouts) that are not in
carbohydrates? Check your handout with images and cutouts.
2. What is the molecular formula of butyric acid? (Add the correct subscripts.) see cutouts
C H O
3. What is the molecular formula of caproic acid? (Add the correct subscripts)
C H O
4. Is the ratio of hydrogen atoms to oxygen atoms the same in each fatty acid? (Give specific
examples in your answer)
5. Note the end of butyric acid containing the oxygen atoms. This special end arrangement of
carbon, hydrogen, and oxygen is called a carboxyl group
Is the carboxyl group present in all fatty acids?
___________
6. A fat molecule consists of one glycerol molecule and three fatty acid molecules joined together.
Cut out the glycerol and fatty acid paper model molecules from cutout page . Remove
three
-OH ends
from the glycerol molecule and
three -H ends
from the fatty acids.
Now is it
possible
to join the molecules to form a fat?
Now
build a fat molecule? You will need to remove (and save)
the H and OH. And save the
newly made water molecules?
a.
How many fat molecules are made? _____- And why?
b.
Is it unsaturated or saturated? Are there any c-c double bonds
Glue the water molecules and the new fat molecule onto a sheet of paper.
7.
How many
water molecules are formed when one fat molecule is produced?
Part B. Proteins
Carbohydrates consist of many monosaccharides joined together while
fats consist of glycerol and fatty acid molecules joined together. Proteins also consist of smaller
molecules. These molecules are called amino acids.
1. Examine the structural formulas and corresponding paper models of the four representative
amino acids (see cut outs). Is
nitrogen
present in fats and carbohydrates?
2. What is the molecular formula of glycine? (Add the correct subscripts)
C H O N
3. What is the molecular formula of alanine? (Add the correct subscripts)
C H O N
4. Are the molecular formulas for all amino acids the same? _________________
5. What end arrangement of atoms is present in amino acids
that was also
present in fatty acids?
6. Another end arrangement in all amino acids consists of a nitrogen atom and two hydrogen
atoms. This group is called an amino group. Do all structural formulas for each amino acid
have an amino group?
7.
Now cut out the four amino acids from page
. Cut along the solid lines only. Attempt to join
the amino acids. Will the protein molecule stay together? ________ How many molecules
of water are formed when four amino acids join together?
a. Now
build your protein a molecule? Any order
(Cut out the H and OH )And save the
water molecules? How many? _____- And why?
Glue the water molecules and the new
polypeptide onto a sheet of paper.
8. Dehydration means “water loss” Synthesis means “to put together”. Explain why the chemical
process responsible for building a carbohydrate, fat or protein molecule is called
dehydration
synthesis
?
9. What two types of molecules are needed to form a fat molecule?
10.What type of molecule is needed to form protein molecules?
11.How does a glycerol molecule differ from a carbohydrate molecule? (Use molecular formulas for
comparison.)
12.How might a human muscle protein molecule differ from a cow muscle protein molecule?
13.A protein consisting of six amino acids undergoes hydrolysis. How many water molecules must
be broken down and reattached to amino acid molecules during this process?
Do not Cut out
Fatty Acids (3 types)
CUT OUT THESE
Amino Acids (4 types)
Lab 4 Macromolecule Food Testing
Purpose: Can you determine if these solutions have fat, carbohydrates, or proteins.
Procedure:
Reagent Tests: Each test is compared to the control – water!
1. Benedicts: Monosaccharide
a. Add 10 drops of Benedicts to 2 mL of solution in to each test tube (2). b. Heat for 5 minutes in hot water bath- observe the four-five different color i. List the colors __________- _________ _______ ________ _____
2. Iodine: Polysaccharides
a. Add 10-20 drops of Iodine to 2 mL of the solution in to each test tube (2).
3. Biuret: Protein: CAUTION this solution contains a concentrated base (NaOH 3%). Wash area immediately if the solution comes in contact with skin.
a. Add 20-30 drops of Biuret to 2 mL of solution in to each test tube (2).
4. Paper: Fats
a. Rub the food on a piece of paper and hold it up to the light. When the solution contains fat the paper will be clear. Compare this to water.
Data:
Solution Reagent Test Results (positive or negative
compared to water)
Water
Benedicts heated Glucose (monosaccharide)
(10% solution)
Water
Iodine
Potato Starch (polysaccharide)
Water
Biuret Gelatin (Protein)
(2% solution)
Water
Paper Test Corn Oil (lipid)
Unknown Food Solutions
Unknown Hypothesis Results Hypothesis Results Hypothesis Results Hypothesis Results Water 2 ml
Unknown 1 use 2 ml
Unknown 2 use 2 ml
2ml of
2ml of
2ml of
2ml of
Discussion Questions:
1. Why did you use water as the control? explain
2. What color indicated high levels of monosaccharides when using the benedicts test?
3. What is a source of polysaccharides in your diet?
4. Name something you eat which contains all of the macromolecules you tested for today?
5. What is the fourth group of macromolecules we did not test? Can you think of a source of them in your diet?
Turn In:
Typed Data Tables
Lab 5 Enzyme-Substrate Model Lab
(aka. Penny Lab)
In this lab pennies will be used to represent substrate molecules. Your hands will represent the enzyme and your fingers will represent the active site of the enzyme.
Each group will gather baseline “enzyme” activity and then collect data for the following variables including physical handicaps (denaturation and competitive inhibitors) and facilitators (coenzymes). Class data will be compiled, graphed, and analyzed. Each group will be responsible for turning in the necessary data tables, graph, questions, and typed conclusion for this lab.
Objectives:
To study reaction rates of an enzyme-mediated reaction.
To study the effects of environmental variables on enzyme functions.
To collect, graph, and analyze data relating to the reaction.
Hypothesis:
Enzymes work by physically joining temporarily with their substrate. Their ability to process the substrate may be affected by other environmental variables.
Notes:
Although you should attempt to do this as quickly as possible, this is not a race or a competition with students from other groups. It will be class data that will be analyzed, not individual group data.
Do not return pennies to the middle after each trial. The number of pennies will be re-established to 500 with each new variable that is being tested.
Each student may use both hands to pick up pennies
For each trial count only the pennies that are in the designated area and are heads up.
Set Up:
Groups of four
Spread 500 pennies within a taped area of 2mX2m.
Create “chutes” for each group behind the tape 1 meter wide.
Designate “bank” area where pennies are to be placed heads up for each group behind their chute.
Group members should be assigned roles for gathering the substrate molecules:
o Baseline data (no limitations-2 hands)
o Competitive Inhibitor or Slight damaged enzyme (fingers taped together) o Denatured (gloves)
o Coenzyme (2 students working together – one gathering and one flipping)
One person should also be the counter/recorder.
Each trial will last fifteen seconds.
Tasks:
During each of the six trials for each variable the group member(s) involved will attempt to gather as many pennies as possible and place them heads up in the designated area.
DO NOT RETURN PENNIES TO FLOOR BETWEEN TRIALS.
Record your groups data for each trial of each variable.
As a Class: Compile Data
Follow Up:
Graph total # of pennies for each trial vs. the final time of each time period.
Type conclusion.
Analysis Questions:
1. In this activity the:
Enzyme was represented by:
Substrate was represented by:
Coenzyme or Double the Enzyme Concentration was represented by:
Competitive Inhibitor or Slight damaged enzyme was represented by
2. With the baseline data, why does the rate eventually decrease? Or why might it start to decrease?
3. What could have been added to maintain the initial rate? In the first experiment?
4. If more substrate were present during the baseline data collection, would the initial rate have been higher? Why or why not?
5. If we assume that the enzyme is represented by the hand, what happened to the active site when we taped the person’s fingers? Does this represent a competitive or non-competitive inhibitor?
6. Why does an enzyme not work as well if its active site is changed?
7. What environmental factors affect enzyme shape?
8. What affect did denaturing (like gloves) have upon the reaction rate?
9. How might chemicals affect you if they acted like the glove (denatured) during your bodily chemical reactions?
11. What is the role of enzymes in your body?
Data Table for Individual Group Substrate Molecule Collection
Time Period (s) Normal RxnBaseline (# of pennies)
Slight damaged enzyme Taped (# of pennies)
Denatured Damaged Enzyme
(# of pennies)
Coenzyme or Double the Concentration of enzyme
(# of pennies)
0-15 15-30 30-45 45-60 60-75 75-90
Class Data
TimePeriod Baseline Slight damagedenzyme Taped (# of pennies)
Denatured Damaged Enzyme
glove
Co- Enzyme or Double the Concentration of
enzyme
(sec) #
select Total # select# Total # select# Total # select# Total #
0-15 15-30 30-45 45-60 60-75 75-90
#select = total number picked up by the entire class
Total # = total number picked up at the end of that interval (this is what you will graph vs. the final time of that time period)
Turn in:
1) Data tables2) Graphs: Create a multiple line line-graph of the total number for each condition of the class data. 3) Answers to the questions
Lab 6: Enzymes are our Friends
Introduction
Enzymes are biological molecules that act as catalysts for chemical reactions that take place in our body. A catalyst is a molecule that speeds up a chemical reaction by allowing reactions to take place that usually occur very slowly. There are thousands of different kinds of enzymes in our bodies, and most of us are familiar with the enzymes that help us digest our food. Another enzyme that may not be so common is one called catalase. Catalase is an enzyme found in all of our body cells. The job that catalase performs is to break down Hydrogen Peroxide. Hydrogen Peroxide (H2O2) is a substance that is produced by all of our cells, but it is also toxic to our cells. In
order to stay alive, our cells produce the enzyme catalase to break down the poisonous hydrogen peroxide. The equation for this process is as follows:
2H
2O
2+ catalase
2H
2O + O
2+ catalase
Substrate enzyme product product
You have seen this equation take place when you pour hydrogen peroxide on your cuts. When hydrogen peroxide is poured onto a cut, the catalase in the skin cells breaks down the hydrogen peroxide and you see bubbles of oxygen being released. The oxygen produced helps to kill bacteria that may have entered the skin through the cut.
Catalase is also found in other animal cells, such as chicken liver cells. Today we are going to test the enzyme found in liver with hydrogen peroxide. We are also going to test to see if catalase is found in plant cells as well. During the lab we will see if enzyme activity is affected by changes in the environment, such as heat and acidity.
Purpose
The purpose of this lab is to test the effects of pH and heat on enzyme function.
Materials
Four test tubes optional 2 eye droppers (one for water and one for catalase) Test tube rack
1 250 ml beaker
4 ml of catalyze extract-class supply potato extract
Test tube tongs Boiling water bath Dropper bottle of HCl Dropper bottle of NaOH pH paper (10 strips) ruler
How would you rate these reactions? (measure from top of liquid to top of bubbles)
A B C D
Procedure
Gather all the supplies follow the directions below.***You will be performing ten different tests: Five using liver/catalase, and Five using potato extract. You might do an optional set with liver extract.
Control Test Tube- save for comparison
1.
Pour 1 ml of water into test tube
2.
Add 2 ml of hydrogen peroxide to the test tube
3.
Measure the height of the bubbles in the reaction
4.
Record the results in the data table
Catalase Tests Test One = Test Tube #1
1.
Pour 1 ml of catalase extract into test tube #2 (or potato juice/liver juice)
2.
Add 2 ml of hydrogen peroxide to the test tube
3.
Measure the height of the bubbles in the reaction
4.
Record the results in the data table
DO NOT THROW OUT YOUR SAMPLE!!! (#1a) You still need it!
5.
Now add another 2 ml of hydrogen peroxide to the test tube that you just finished with
6.
Record the results in the data table
7.
Measure the height of the bubbles in the reaction
8.
Record the results in the data table-rinse test tube out and dry it
Test Two Boiling water=Test Tube #2
1.
Pour 1 ml of catalase extract into test tube #2 (or potato juice/liver extract)
2.
Place the test tube into the boiling water bath for 5 minutes
3.
Remove the test tube from the bath
4.
Add 2 ml of hydrogen peroxide to the test tube
5.
Measure the height of the bubbles in the reaction
6.
Record the results in the data table
Test Three Acid = Test Tube #3
1.
Pour 1 ml of catalase extract into test tube #3 (or potato juice/liver extract)
2.
Take the pH of the extract with the pH paper
3.
Record the pH in the data table
4.
Add 15 drops of HCl to the tube
5.
Take the pH of the extract with the pH paper and record the pH in the table
6.
Add 2 ml of hydrogen peroxide to the tube
7.
Measure the height of the bubbles in the reaction. Record the results in the data table
Test Four Base= Test Tube #4
1.
Pour 1 ml of catalase extract into test tube #4 (or potato juice/liver extract)
2.
Take the pH of the extract with pH paper and record the pH in the table
3.
Repeat test #3, but with NaOH instead of HCl. (15 drops)
4.
Add 2 ml of hydrogen peroxide to the tube
Potato Juice /Liver tests
Repeat each of the above tests, but replace the catalase extract with potato and or liver extract
(5mL rather than 1mL). Be sure to record all data in the table. Note the liver is optional!
Data Table
Classify your results as: measure bubble height. Tests
Control Test Tube Control
Reactions Catalase Potato Liver (optional)
Test #1-do enzymes work?
What happens? #1
Test #1A reused
enzymes?-how do you know? #1a
Test #2-after boiling
water-Enzy work? #2
Test #3-HCl and Enzymes #3
Test #4 NaOH and
Enzymes #4
pH Observations Catalase Potato Liver (optional)
Initial pH of test tube #3
before HCl pH
pH after 15 drops test tube
#3 after HCl ph
Initial pH of test tube #4
before NaOH pH
pH after 15 drops of test
tube #4 after NaOH ph
Analysis-Use data to make your conclusion
1. How do the results between the different tests of the catalase compare with those of the potato?
2. Where is catalase found in nature? Why do you think this is so?
3. Did pH affect the reaction of the enzyme? Why do you think this is so?
4. Did the potato contain catalase? How do you know this?
Turn In:
Typed Data Table
Typed Answers to the discussion questions-Explain each experiment: control, reused enzymes,
Lab 7 Salivary Amylase and Starch Digestion Lab
DESCRIPTION
The ability of the enzyme amylase, found in human saliva, to break down
starch molecules will be demonstrated in this lab. The activity of the enzyme in various
solutions will also be demonstrated.
We will test for starch with Iodine- does the starch change to glucose?+starch test=?______
1 ml
MATERIALS
t
est tubes-3
starch
plastic pipette
Rubber bands
Dropper bottles Iodine Solution Dropper bottles of 1.0 M HCl
PROCEDURE
A. Obtain a sample of saliva (6-8 ml). This can be done by chewing a clean rubber band and
drooling into a beaker.
1. Place 2 ml of water and 1.0 ml of starch (no bubbles) in test tubes-label
(starch/water-control) -no Saliva in this tube
2. Place 2 ml of salvia(no bubbles) in another test tubes-label (saliva/starch)
3. Place 2 ml of salvia(no bubbles) in a test tubes and then add 10 drops of 1.0M HCl to
one of the saliva tubes-label (HCL/saliva/starch).
B. Allow the tubes to stand for approximately 15 minutes. It is even better to warm them in
your hand during this period. (why?)
C. Then add 1-2 drops of iodine solution to each-record color change.
D. All substances can be poured down the sink.
TT’s=
1
2
3
4
xxxxx-no spit
Spit-Amylase-2.0 ml
Spit-Amylase-2.0
ml
Spit-Amylase-2.0
ml
Water 2.0 ml
No water
HCL 10
drops-wait 3 minutes
before starch is
added
NaOH 10
drops-wait 3 minutes
before starch is
added
1.0 ml Starch
1.0 ml Starch
1.0 ml Starch
1.0 ml Starch
Iodine after 15 min Iodine after 15 min Iodine after 15 min Iodine after 15 min If no black color, then the
enzyme reaction worked or Enzy rxn failed and we see black-lots of starch left over
What happened and why?
1. What is the enzyme?_____________ the substrate__________________
2. Explain your results. What happened and why?
3. Which test tube(s) were the control
Lab 8 Temperature and Enzymes
Student Inquiry
Your mission is to design an experiment that shows how enzymes are affected by temperature but not boiling hot temperatures! You will have the following materials available to you and one class day to work. You should use all the knowledge we have learned about enzymes to design and carry out your experiment. In your group please make sure to design an experiment that meets all the requirements of a good
scientific lab (control/replications?). Good Luck!
Materials available to you (you may use what you need):
Potato Juice or Liver Juice
Hydrogen Peroxide
Water: Room Temp(20
oC) 0
oC
35
oC 45
oC 55
oC
Small Test Tubes and Rack
Graduated Cylinder
Mortar and Pestle
ruler
Anything else you need?
Turn In:
Title
Introduction: including background on temp of enzymes-cite your research
Hypothesis
Materials and Procedures
Result table & graph-and 1 sentence summary of your data
Discussion - what happened and why?
o
Use your numbers if you collected quantitative data
o Please see http://www.indiana.edu/~wts/pamphlets.shtml for information on how to avoid plagiarism. Note one can share ideas but you may not share words. Five words in a row taken from another source without quotes is a sign of plagiarism
o Do not use Wikipedia as a source for any cited work. You can use Wikipedia as a starting point to orient you to a topic, but I expect that you find primary research for your written work. You should not use Wikipedia for any written research project.
Draw your experimental set up here!
Lab 9 The Incredible Edible Enzyme Lab
(Take Home Lab)
Procedure
You are expected to perform this lab at home and turn in the items listed below. You may work in pairs if you would like. (Split up parts of the lab and report results to each other) YOU MUST OBTAIN A PARENT’S SIGNATURE STATING THAT YOU PERFORMED THE LAB!!
Lab Investigation
You need to purchase:
2 packs of the same kind (flavor) of jello
FRESH pineapple (bags usually by fruit section, or whole pineapple –
o you can also try a fresh kiwi fruit)
Canned pineapple
Set-up #1 (lab partner #1)
1. Make a bowl of plain jello (no fruit)
2. Make a bowl of jello with junks of fresh pineapple in it
Set-up #2 (lab partner #2)
1. Make a bowl of plain jello (no fruit)
2. Make a bowl of jello with canned pineapple in it
If you are working alone:
Make three bowls of jello… one plain, one with fresh pineapple, one with canned pineapple.
Pineapple Lab Expectations
General Info to be included in the analysis section:
Discuss how the enzyme affects the set up of the gelatin; be sure to include specifics about how enzymes work. A diagram of what is going on would be very helpful.
Discuss why there is a difference between the canned pineapple and the fresh pineapple. This should include information about what happens to pineapple during the canning process and how this relates to the results that you saw.
Set up of Lab report: This should be typed, in 12 pt font, and double-spaced.
a. Title: The lab is titled.
b. Introduction: A paragraph introducing the reader to the concepts of the lab. Pretend that they have not been sitting through this class for the past 2 weeks. Introduce what an enzyme is, what it does, how it functions. Diagrams are helpful.
c. Purpose: A one-sentence statement that describes the purpose of this lab. ex. The purpose of this lab is to witness an enzyme in action.
d. Materials: List of materials used
e. Procedure: List of the procedure used. This should include the specifics of how you made the gelatin. There should be a separate procedure for each bowl made.
f. Data: Either digital pictures or drawings of what happened. There should be no descriptive words, only labels on the pictures.
i. A table of the findings is provided. Simple chart will due.
g. Analysis: Paragraph that describes why you saw the results.
See Above for details.
Turn in:
Lab Report
Lab report writing tips- Always use a bibliography if you cite
What an in-text citation looks like: (note this like a footnote- it is not a quote but it is not
your words.
o
Pyridoxine-dependent epilepsy is a disease that involves seizures starting when someone
is a baby.(Pyridoxine NIH.gov )
o
Note do not use a long URL for a in text citation- this long URL goes in your bibliography.
http://ghr.nlm.nih.gov/condition=pyridoxinedependentepilepsy
Note: If your writing
includes 5 or more words directly copied from a source
- you
need to place all the words in quotes and use and in-text citation or footnote. “Prion
protein (PrP) plays a central role in Creutzfeldt–Jakob Disease (CJD) and other
transmissible spongiform encephalopathies (TSEs)” (McCormack 2002).
As a good guideline for your writing in any subject, a paragraph should have less than
25% quoted material. That means 75% of a paragraph should be written in your own
words
.
Also, anytime you use a quote in your writing, you need to analyze or discuss it
Please see
http://www.indiana.edu/~wts/pamphlets.shtml
for information on how to avoid
plagiarism. Note one can share ideas but you may not share words. Five words in a
row taken from another source without quotes is a sign of plagiarism
Lab 10 Radioactive half-life lab
Goal: To see radioactive dating in action.
Procedure:
Put 100 coins in a cup/beaker, shake, dump out coins, separate heads from tails. Count the heads and return them to cup (they are radioactive carbon 14). Record the # of heads on graph. Repeat until all coins are tails and you have none left. Use the graph to answer the following questions.
Assume radioactive Carbon has a half life of 6000 years. Start the graph with 100 heads-time 0. (line graph)
Conclusion:
connect dots with smooth line. Use the graph to answer the questions1.
What happened and why?
2.
If you found an object with 20 molecules of C
*14, what could you conclude? (see graph)?
a. How old?
3.
If you found an object with 3 molecules of C
*14, what could you conclude? (see graph)
a. Get class data on years- why same or different or inconsistent?
4.
Why can’t (or can you) you determine if an object is 100,000 years old using C
*14data.
Cite some specific data to support your argument. Is there a limit to using C
*14data
Lab 11 History of Everything!
See also http://www.lifethroughtime.com/ click start the journey/ view the slide show
Purpose: Your mission to make a make a timeline in order to gain a better understanding of the relative time of evolutionary events.
Procedure:
1. Cut a piece of adding machine paper one meter long
2. Using a pencil divide one side into 12 equal parts and label each box with the moths of a year. 3. Divide the other side into 31 equal parts and label each box 1-31. This will represent the month of
December.
4. In each box draw a description of what happened in evolutionary time as described below.
5. Your drawings should be accurate (don’t draw a fish for an invertebrate), creative, neat, and labeled correctly.
The big bang occurred between 10-20 billion years ago and earth was created 4.6 billion years ago. Since understanding these extraordinary lengths of time is difficult one method to better comprehend evolution is to think of events relative a calendar year. If the big bang was in Jan here is the order of events relative to a 12 month calendar:
January 1st: Big Bang
May 1st: Origin of the Milky Way Galaxy
September 9th: Origin of Solar System
September 14th: Formation of the Earth
September 25th: Origin of Life on Earth
October 9th: Date of oldest fossil
November 1st: Invention of Sex (in
micro-organisms)
November 12th: Older photosynthetic plant
November 15th: First cells with nuclei
Too much happens in the month of December using the scale we used in the first time line. In the second time line (on the back of your paper) the 31 divisions represent the days in the month of December. Place the items listed below with their proper day. Make illustrations for this time line too. The purpose of the illustrations is to teach you the vocabulary and also to recognize the overall sequence of evolution.
December
1st Sign oxygen in the atmosphere begins
to develop on earth 5th Formation of Mars
16th First Worms
17th Invertebrates flourish
18th First oceanic plankton
19th First Vertebrates (Fish)
20th Plants begin to colonize land
21st First insects colonize land
22nd First Amphibians
Turn In:
Time Line: Remember your time line will be graded on Neatness, Creativity, and Biological Accuracy. Have Fun!! Check
out this:
http://www.johnkyrk.com/evolution.htm
l
23rd First Reptiles
24th First Dinosaurs (which are reptiles of
course)
26th First Mammals
27th First Birds
28th First flowers and dinosaurs become
extinct
29th First Primates
30th Giant mammals flourish
A reading: On the Origin of Species
From PBS – evolution library
When on board H.M.S. Beagle, as naturalist, I was much struck with certain facts in the distribution of the inhabitants of South America, and in the geological relations of the present to the past inhabitants of that continent. These facts seemed to me to throw some light on the origin of species -- that mystery of mysteries, as it has been called by one of our greatest philosophers. On my return home, it occurred to me, in 1837 that something might perhaps be made out on this question by patiently accumulating and reflecting on all sorts of facts which could possibly have any bearing on it. After five years work I allowed
myself to speculate on the subject, and drew up some short notes; these I enlarged in 1844 into a sketch of the conclusions, which then seemed to me probable; from that period to the present day I have steadily pursued the same object. I hope that I may be excused for entering on these personal details, as I give them to show that I have not been hasty in coming to a decision.
My work is now nearly finished; but as it will take me two or three more years to complete it, and as my health is far from strong, I have been urged to publish this Abstract. I have more especially been induced to do this, as Mr. Wallace, who is now studying the natural history of the Malay archipelago, has arrived at almost exactly the same general conclusions that I have on the origin of species. Last year he sent to me a memoir on this subject, with a request that I would forward it to Sir Charles Lyell, who sent it to the Linnean Society, and it is published in the third volume of the Journal of that Society. Sir C. Lyell and Dr. Hooker, who both knew of my work -- the latter having read my sketch of 1844 -- honored me by thinking it advisable to publish, with Mr. Wallace's excellent memoir, some brief extracts from my manuscripts.
In considering the Origin of Species, it is quite conceivable that a naturalist, reflecting on the mutual affinities of organic beings, on their embryological relations, their geographical distribution, geological succession, and other such facts, might come to the conclusion that each species had not been independently created, but had descended, like varieties, from other species. Nevertheless, such a conclusion, even if well founded, would be unsatisfactory, until it could be shown how the innumerable species inhabiting this world have been modified, so as to acquire that perfection of structure and co adaptation which most justly excites our admiration. Naturalists continually refer to external conditions, such as climate, food, etc., as the only possible cause of variation. In one very limited sense, as we shall here after see, this may be true; but it is preposterous to attribute to mere external conditions, the structure, for instance, of the woodpecker, with its feet, tail, beak, and tongue, so admirable adapted to catch insects under the bark of trees. In the case of the mistletoe, which draws its nourishment from certain trees, which has seeds that must be transported by certain birds, and which has flowers with separate sexes absolutely requiring the agency of certain insects to bring pollen from one flower to the other, it is equally preposterous to account for the structure of this parasite, with its relations to several distinct organic beings, by the effects of external conditions, or of habit, or of the volition of the plant itself.
The author of the 'Vestiges of Creation' would, I presume, say that, after a certain unknown number of generations, some bird had given birth to a woodpecker, and some plant to the mistletoe, and that these had been produced perfect as we now see them; but this assumption seems to me to be no explanation, for it leaves the case of the co adaptations of organic beings to each other and to their physical condition of life, untouched and unexplained.
obscure problem. Nor have I been disappointed; in this and in all other perplexing cases I have
invariable found that our knowledge, imperfect though it be, of variation under domestication, afforded the best and safest clue. I may venture to express my conviction of the high value of such studies, although they have been very commonly neglected by naturalists.
No one ought to feel surprise at much remaining as yet unexplained in regard to the origin of species and varieties, if he makes due allowance for our profound ignorance in regard to the mutual relations of all the beings which live around us. Who can explain why one species ranges widely and is very numerous, and why another allied species has a narrow range and is rare? Yet these relations are of the highest importance, for they determine the present welfare, and, as I believe, the future success and modification of every inhabitant of this world. Still less do we know of the mutual relations of the innumerable inhabitants of the world during the many past geological epochs in its history. Although much remains obscure, and will long remain obscure, I can entertain no doubt, after the most deliberate study and dispassionate judgment of which I am capable, that the view which most naturalists entertain, and which I formerly entertained -- namely, that each species has been independently created -- is erroneous. I am fully convinced that species are not immutable; but that those belonging to what are called the same genera are lineal descendants of some other and generally extinct species, in the same manner as the acknowledged varieties of any one species are the descendants of that species.
Furthermore, I am convinced that Natural Selection has been the main but not exclusive means of modification.
On the Origin of Species by Means of Natural Selection. London. 1859.
Complex Relations
This text is excerpted from Charles Darwin's On the Origin of Species by Means of Natural Selection. Drawing on research and personal observation, Darwin examines the "mutual relations of all organic beings." Through his study of competition and cooperation among plant and animal species shaped by environmental factors, Darwin describes the forces that drive evolution.
I am tempted to give one more instance showing how plants and animals, most remote in the scale of nature, are bound together by a web of complex relations. I shall hereafter have occasion to show that the exotic Lobelia fulgens, in this part of England, is never visited by insects, and
In the case of every species, many different checks, acting at different periods of life, and during different seasons or years, probably come into play; someone check or some few being generally the most potent, but all concurring in determining the average number or even the existence of the species. In some cases it can be shown that widely-different checks act on the same species i
