Biology Module Remedial Courses
Unit 1: The science of biology (1 hrs.)
1.1. The methods of science
1.2. Tools of the biologist
Unit summary
Review questions
Unit 2: Biochemical molecules (6hrs.)
2.1. Inorganic molecules
2.2. Organic Molecules
Unit summary
Review questions
Unit 3: Cell biology (7 hrs.)
3.1. Cell theory
3.2. Types of cell
3.3. Parts of the cell and its function
3.4. The cell and its environment
3.5. Cellular respiration
Unit summary
Review questions
Unit 4: Microorganisms (7 hrs.)
4.1. Introduction to microorganisms
4.2. Beneficial microorganisms
4.3 Pathogenic microorganisms
Unit summary
Review questions
Unit 5: Genetics (7 hrs.)
5.1. DNA and chromosome structure
5.2. DNA replication
5.3. Protein synthesis
5.4. Mitosis and meiosis
5.5. Mendelian inheritance
5.6. Mutations
Unit summary
Review questions
Unit 6: Evolution (2hrs.)
6.1. Theories of origin of life
6.2. Theories of mechanisms of evolution
6.3. Speciation through natural selection
6.4. Modern theories of evolution
Unit summary
Review questions
Unit 7: Biotechnology (4 hrs.)
7.1. Scope and definition
7.2. Agricultural biotechnology
7.3. Medical biotechnology
7.4. Industrial biotechnology
7.5. Environmental biotechnology
Unit summary
Review questions
Unit 8: Human biology and health (10 hrs.) 4 | P a g e
8.1. Food and nutrition
8.2. Non communicable diseases
8.3. The digestive system
8.4 The respiratory system
8.5. The circulatory system
8.6. The nervous system
8.7. Sense organs
8.8. Endocrine glands
8.9. The reproductive system
Unit summary
Review questions
Unit 9: Food making and growth in plants (4 hrs.)
9.1. Plant organs
9.2. Photosynthesis
9.3. Transport in plants
9.4. Response in plants
Unit summary
Review questions
Unit 10: Ecology and conservation of natural resources (5 hrs.)
10.1. Definitions
10.2. Cycling matter through ecosystems
10.3. Ecological succession
10.4. Biomes
10.5. Conservation and Biodiversity
10.6. Vegetation and wildlife
10.7. Global warming and air pollution
Unit summary
Review questions
Unit one: The Science of Biology
Introduction
Biology is a special branch of science that deals with living things. Biology uses the scientific methods to study the nature and functions of living things as well as the interactions with each other and with the environment of which they are parts. The sphere of Biology is unique in that it covers a highly organized form of matter. Biology is one of the most interesting subjects. It is especially important subject for everyone, since it will affect every one’s future. Many Biologists are working on problems that critically affect our lives, such as the world’s rapidly expanding population and diseases like cancer, COVID 19, and AIDS.
What opportunities exist in Biology now and in the immediate future?
There is much opportunity for researchers, particularly in developmental biology (What genes cause birth defects and can anything be done to correct the damage?). Immunology (will there be a cure for cancer, AIDS, or the common cold?
Why is Biology important to you? and your community (discuss in group)
Use the following information and helps us to
- Use and manage natural resources
- Prevent and cure diseases
- Improve the quality of our lives and the future generations
The Scientific Method
Science in general is a body of knowledge, which is systematically organized on nature, society and thought. Studies in science involve three interrelated concepts,
- Method of investigation
- Field of investigation and
- Results of investigation
The scientific method involves a series of logical steps that help to study natural processes. It is a powerful method, which can help to solve new scientific problems. Knowledge is not absolute and unchanging as it always faces the test of time. Thus, it is the knowledge that has accumulated by scientific method. We humans often ask whom we are, where we come from, how we could live in harmony with the environment. The measures that we take to provide scientific explanations to these and other similar questions constitute the scientific method. Existing scientific truth is relative and must be continually tested, evaluated and reconstructed. The scientific method is not limited to the laboratory but is a way of everyday life. It helps to investigate a crime, diagnosis of a disease, etc. These could be justified and validated following certain scientific steps:
The steps of the scientific method
Scientists use different scientific methods to solve problems and they all share the following common steps.
- Observation:
Our entire view of the natural world depends on the accurate recording of data and the organization of these data into general concepts. Observations can be made directly through the sensory systems, mainly vision, hearing, taste, smell and touch. They can also be made indirectly, through the use of special equipment such as the microscope that extends the range of perception. Preliminary observation with curiosity leads to identification of a specific problem among the many that exist in the environment. Most biological investigation starts with an observation of structure process or a behavioral pattern, that raises inquiry like why, how when etc.
- Defining or identifying the problem or asking question:
Scientific experiments are carried out based on a specific problem or question. First such a problem has to be identified before proceeding to the next steps. Observations are made and facts gathered leading to the definition and elaboration of the problem or question more precisely. A scientist’s natural reaction is to ask question about it. What will happen? Why is it so? How does it take place? etc.
- Gathering information and forming a hypothesis:
The information gathered could be qualitative describing color, taste, etc. or quantitative involving the measurement of an amount of quantity. Observations provide the raw material, which leads to the formulation of a hypothesis. Hypothesis could be defined as a suggested explanation of certain observed phenomena/problem. Scientific hypothesis need to be tested since they are assumptions of tentative explanations. On the other hand, a hypothesis is a tentative theory characterized as:
- An intelligent guess
- Gradual accumulation of indirect evidence
- It may have number of predictions
- It consists of interconnected statements that give a possible solution to a problem
New observations that support the hypothesis will strengthen it, whereas new observations that contradict with the hypothesis may result in its being modified or even rejected.
Inductive and deductive reasoning
Induction and deduction are patterns of thought often recognized in the creation of a hypothesis. Inductive logic proceeds from the specific to the general whereas deductive logic proceeds from the general to the specific. Consider the following examples for better understanding of the difference b/n inductive and deductive reasoning.
Deductive reasoning: Example
- All animals are mortal (major premises)
- Dogs are animals (minor premises). Therefore, Dogs are mortal
Inductive reasoning: Example
- Apple x – tastes sweet
- Apple y – tastes sweet
- Apple z – tastes sweet etc.
Conclusion: All apples are sweet.
- Testing hypothesis / Experimentation
- Hypothesis testing often involves experimentation
- A hypothesis that has with stood many such tests and has been shown to allow prediction to be made is known as theory. A theory may generate such confidence through its predictive ability to be known as a law.
4.1. Scientific experiment
In most hypotheses there are a number of factors which may influence the observation. These are called experimental variables. The 3 general categories of variables are:
i. The independent variables – are the conditions or events under experimentation or testing. It can be changed systematically in an experiment. Example: In an experiment in which seedlings are grown at different temperatures. Temperature is the independent variable.
ii. The dependent variables – are variables that can possibly change because of the presence of or changes in the independent variables. e.g. the rate of growth (fast or slow) of seedlings at different temperatures.
iii. The controlled variables – are conditions that could affect the outcome of an experiment but that do not do so because they are held constant. e.g. in an investigation of the effect of light on plants the control will be a plant kept in the dark.
The usual way of testing hypothesis is by performing a carefully planned experiment. Such a carefully planned experiment consists of two components
- Experimental group (treated group)
- Control group (un treated group)
A controlled experiment tests only one factor at a time keeping the rest of the factors constant. Example: “Germinating seeds produce C02 during respiration” There will be two set ups
- A set up with a test tube containing germinating seeds connected to another test tube containing water
- Similar set up but with the test tube with non-germinating seeds (control)
The experiment will turn limewater into milky color due to release of C02 during respiration by germinating seeds, but in (ii) the limewater will not turn milky. Now a comparison of (i) with (ii) leads to a conclusion that C02 evolve during respiration.
- Recording Analysis and interpretation of Data
Results are recorded carefully and systematically and usually organized in the form of data tables, charts or graphs in addition to verbal explanations. Analysis of data means studying the organized material in order to discover the essential facts.
Here are four helpful modes that help you to analyze the data gathered:
- Choose clear tables or figures for presenting the data
- Examine carefully the statement of the problem
- Further discuss with others about the problem
- Treat the data using various statistical calculations to check similarities and differences.
The stage of interpretation after analysis is essential to state what the results show. Hence, interpretation needs a careful logical and critical examination of the results obtained after analysis.
- Drawing conclusions
Conclusions or generalizations require careful and objective analysis of the data gathered.
- Theory, principles, fact and law
When a given hypothesis has been tried (tested) many times by independent investigations and found to be acceptable it is no longer a hypothesis, but it becomes a theory.
- a theory is a hypothesis tested to be true
- a theory is open to tests, revision and tentative acceptance or rejection. e.g. A theory of evolution has changed over a period of time
- At times discoveries are made much earlier but take the form of a theory after subsequent findings only. E.g. Robert Hooke discovered cell in 1665 but cell theory was formulated by schleiden and schwann in 1838 – 1839.
When a theory has proved invariable under all circumstances, or such variations are systematic and predictable, then it may be accepted as a fact, principle or law. This happens by further experimentation or observation as the case may be another highest level of scientific concept is modeling. A model is a mental map formed by deliberate analogy with a more familiar concept. Models are used in science to simplify ideas or certain aspects of a phenomenon.
e.g. – The key and lock model of enzyme action
– The crick and Watson model of DNA structure
8. Evaluation
For valid conclusions many rounds of the same experiment need to be undertaken. i.e. each experiment should be done again and again until consistent results are obtained. This phase of a scientific experimentation is known as evaluation.
9.Reporting and publishing results
Communication is an important component of the scientific method. The knowledge generated in a field of science has to reach the scientific community. The proper channels of communication for scientists and researchers are scientific journals, conference proceedings, bulletins and other publication series. Communication through reporting also avoids repetition of the same work.
Figure 1. Summary of scientific method (The way How it proceeds).
1.2. The Basic tools of a Biologist
Biological information is gathered through observations and experiments, conducted in the laboratory and in the field. Practical interactions with biological objects and processes are important in making the theoretical knowledge more concrete and meaningful. Many techniques and tools or instrument are used in Biology. For convenience, they can be divided into tools used in the laboratory and tools used in the open fields. Hence, in this unit you study and use many of the tools of the biologist as described below and then the microscope is studied in detail.
Activity 12: Study on the basic tools of a biologist
Materials:
| Laboratory tools/instrument | Field tools/instrument |
| 1.Dissecting kit (forceps, scalped mounting needle, scissors, dropper, brush) | 1. Plant press, plastic bags, envelops |
| 2. Mortar and pestle | 2. Insect net |
| 3. Pipette | 3. Secateurs |
| 4. Microscope (Slides, cover slips) | 4. Auger |
| 5. Hand lens | 5. Meter |
| 6. Petri-dish | 6. Altimeter |
| 7. Rulers | 7. GIS*/GPS** |
| 8. Centrifuge, water-bath over | 8. Traps, Cages |
| 9. Glassware, aquarium | 9. Digger |
| 10. Balance, test tubes | |
| 11. Calculators | |
| 12. Computer |
* GIS (Geographical information system) is a software package for visual display of spatial data and computations based on the data and
** GPS (Geographical positioning system) is an equipment used to find a location.
The Microscope
A microscope is a precision device used to show objects that are too small to be seen at all with the naked human eye. Most cells are microscopic in size. Without microscopes, very little would have been known about cells. The microscope is the most important tool used in biological sciences. A microscopy is an old technique used in biology and it is still very important instrument. Advancements in biology are partly due to the invention and improvement modernization of the microscope.
After the invention of the first simple and crude type of microscope by Anthony van Leeuwenhoek advancements were made in the field of microscopy. By the end of the 19th century a light microscope was made, which used light as a source of energy to enlarge the image of an object and improve its vision. The best light microscope can magnify structures (increase in size of the image) up to 1500 times (x 1500) their original or normal size. At this high magnification, the image becomes less clear because the lenses cannot distinguish b/n small structures lying close together. The power of the microscope to scatter the image and show more details is known as the resolving power of the microscope.
Microscopes could be categorized into the following major groups depending on their complexity.
A. Simple microscope
The hand lens is an example of a simple microscope. It consists of a biconvex lens in a supporting frame. It is used to observe the external form of objects, and not the details of their internal structures. The magnification power of the common hand lens is usually between x 10 and x 20. The first microscopes were made of a single lens and hence were simple microscopes.
B. Compound microscope
This is a microscope with magnifying powers of two convex lenses, the eye piece (ocular lens) and the objective lens are used to produce a magnified image of small objects. The compound microscope uses light rays coming from a certain source (open light or an electric bulb), it is known as a light microscope. It uses to investigate internal structure of objects. Compound light microscopes are important to biologists because they allow them to observe many kinds of cells & single celled organisms while they are still alive. That is, an organism does not have to be filled to be observed under a compound microscope. There are limits to what we can see with the compound light microscope. As we increase the magnifying power of a light microscope, we see more and more detail – up to a certain point. Beyond that point, called the limit of resolution, objects get blurry & details are lost. For standard light microscopes, the limit of resolution is about 0.2 micrometers (A typical cell is about 10 micrometers across).
C. Electron microscope
Although light microscopes are very useful, their limits of resolution restrict their useful ness for studying very small objects such as viruses & individual molecule.
In the 1920s, physicists in Germany realized that electromagnets could bend streams of in much the same way that glass lenses bend beams of light.This is a more powerful type of microscope. It uses a beam of electrons instead of light with a greater resolving power unlike the light microscope. The two types of electron microscopes are known as:
1. Transmission electron microscope (TEM): shine a beam of electrons at a specimen and then magnify the specimen onto a fluorescent scram. It reveals the inner most details of the cell interior.
2. Scanning electron microscope (SEM): beam of electrons that scans back & forth across the surface of specimen are picked up by detectors that provide the information to from an image on a TV screen. SEM allow us to study the surface of objects in their dimensional detail. The limitation of electron microscope is that living cells must be killed before they can be observed.
D. Other Types of microscopes
i. Dissecting microscope
This is designed to enable small objects to be dissected or manipulated while viewed under a moderate degree of magnification. In its simplest form, it consists of a stage above which is mounted a single lens magnifying about x 10. A dissecting microscope is binocular, which has two oculars. It is made easier to make manipulation under the microscope easier. This type of microscope is intended for use in manipulative biological work, and for the examination of relatively large objects such as insects.
ii. Phase contrast microscope
In recent years the use of this type of microscope became popular with research workers. This microscope is especially important in studying fine structures in living cells.
iii. Interference microscope
It Works with the same principle as phase contrast microscope. But, increases in contrast as a result of interference between light waves. The interference microscope however, enables smaller differences in contrast to be detected and also gives color effects.
Parts of the compound microscope
Study the diagram (Figure 2) below of the standard compound microscope and identify each of the parts with their functions described in Table (3.2)
Figure 2. Parts of the compound microscope
Table 3. Parts and Functions of a compound microscope:
| Part | Position and Function |
| Arm ( limb)(2) | Supports the body tube and is the part with which you can grip to carry the microscope. |
| Base (foot)(15) | Gives a firm and steady support to the microscope |
| Ocular (eye piece lens) (1) | A lenses system of the microscope with a magnification power 7 x6, x or x 10. This lens is often un attached to the other parts, hence can fall down if not properly kept. |
| Objective Lens(6) | The lens, closed to the object placed on the stage, have several alternative lenses that are switched one at a time. The objective lens x10, gives the smallest image the middle power (40x), gives intermediate size and the high power (x100) gives the largest magnification. The oil immersion lens (x400), operates with the addition of oil, giving even larger magnification. |
| Nose piece(4) | The revolving part to which the objective lenses are attached. |
| Body tube | This may be monocular or binocular, where the eyepiece and objective lenses are supported, at a known distance and angle. The lower and of the tube possess a revolving nosepiece on which the objective lenses are screwed. |
| Stage(9) | This is a broad flat surface with a circular opening at its center that serve as a passage for light from the condenser to the objectives. The stage is also used to support the glass slide that holds the object. |
| Knobs(10) | These are used to move the stage up and down in order to bring the specimen into focus. The focusing knobs may be located near the base or the upper arm depending on the type of the microscope |
| Coarse adjustment | Moves the body tube or stage up and down, depending on the design of the microscope, to approximate the right position so that the specimen is in focus. |
| Fine adjustment | This is used to move the stage or body tube up and down to exactly the right position, so that the specimen is in focus. It uses to get fine focus with the low power objective and for all the high power and oil immersion objectives |
| Iris diaphragm(11) | This is controlled by a lever than can be moved back and forth. It is used to regulate how much light and lamp heat goes through the specimen. |
| Condenser(12) | This is a lens located above the diaphragm, which concentrates the light before it passes thought the specimen. |
| Mirror | Collects light and directs it to the condenser |
| Stage clip(5) | This is located on the stage and hold the glass slide in position( place) |
Resolution and magnification principle of a microscope
The ability to distinguish between two separate objects is known as resolution. If two separated objects cannot be resolved, they will be seen as one object. Resolution is not the same as magnification which is simple enlargement of the specimen for a better observation.
Illustrative example:
If you take a photograph and keep on magnifying or enlarging it, magnification can be increased, but the resolution of the photograph stays the same when the limit of resolution is reached. We enlarge photographs in order to see them move clearly, but if we go too far, the picture breaks up into separate blurred dots. The resolution of an electron microscope is about 0.5nm (nanometer) in practice and that of the light microscope is 200nm. The shorter wavelengths of electrons have greater resolving power than those of light because there is an inverse relation between wavelength and resolving power. Light microscopes are important for getting an overall view of cells or tissues, and the preparation procedure of the objective much quicker and easier. They can also be used to view living material, which is not possible with an electron microscope. A compound microscope may have two or three objective lenses and one or more eyepiece lenses. The total magnification using any combination of these lenses is simply obtained by multiplying the magnification power of the eyepiece lens by that of the objective lens.
