SECOND TERM: E-LEARNING NOTES
SUBJECT: BIOLOGY
CLASS: SS 1
SCHEME OF WORK
WEEKS
TOPICS
1. Basic Ecological concepts: (a) Ecological concepts (b)Components of an ecosystem
(c)Local biotic communities or biomes.
2. Basic Ecological concepts : (a) Major biomes of the World (b) Population studies by
sampling method (c) Ecological factor (d) simple measurement of ecological factors.
(e) Relationship between soil types and water holding effect of soil on vegetation
3. Functional Ecosystem: (a) Autotrophy and heterotrophy (b) Producers (ii)
Consumers (c) Aquatic and terrestrial habitats (d) Tropic levels (d) Food chain (e)
Food web (f) Energy Flow (g) Pyramid of energy/numbers (h) Nature of energy flow.
4. Energy Transformation in Nature: (a) Energy Loss in the ecosystem (i) Solar
radiation (ii) Energy Loss in the biosphere (iii) Measures of primary production e.g
the amount and rate of energy fixation (b)Laws of thermodynamics.
5. Relevance of Biology to Agriculture: (a) Effects of agricultural activities on
ecological systems (b) Pests and diseases of agricultural importance.
6. Relevance of Biology to Agriculture - Continued: (a) Food production and storage
(i) Ways of improving crop yield (ii) Causes of wastages (iii) Methods of preserving
and storing food (b) Population growth and food supply (c) Relationship between
availability of food and human population-effect of shortage (d) Government efforts
to increase food production e.g agriculture revolution.
7. Micro Organisms Around Us: (a) Micro organisms in air and water (i) Group of
micro- organism :bacteria, viruses ,some algae, protozoa and fungi (ii) Concept of
culturing (b)Identification of micro- organisms in (i) air (ii) pond water (iii) river
(iv)stream (c) Micro-organisms in our bodies and food (d) Carriers of micro
organisms – examples, location of microorganism in carriers and types of micro
organisms.
8. Micro-organism in action:(a)Growth of micro –organisms: ways of measuring the
growth of microorganism(b)Beneficial effects e.g. in nature, medicine and industries
(c)Harmful effects of some microbes (i)Types of disease-causing microorganism
(ii)Diseases caused by microorganisms (iii)Ways in which disease causing
microorganisms spread and are transmitted.
9. Towards better health: (a)Control of harmful microorganisms (b) Vectors
(i)definition (ii)ways of controlling vectors (c) Students’ health: Maintenance of good
health.
10. Revision.
11 . Examination.
WEEK 1
SUBJECT: BASIC ECOLOGICAL CONCEPTS
CONCEPT: 1. Ecological concepts
2. Components of an ecosystem
3. Local biotic communities or biomes
Sub – Topic 1: ECOLOGICAL CONCEPTS
Ecology is the study of living organisms in relation to their environment.
The study deals with the relationship of living organisms with one another and with the
environment in which they live. Ecology measures factors affecting the environment; it
studies the distribution of living organisms and how they depend on one another and their
non-living environment for their survival.
Ecology is divided into two
(i) Autecology which is the study of a single individual organism or a single species of
organism and their environment. E.g. the study of Tilapia fish in a particular stream.
(ii) Synecology which is the study of inter–relationships between groups of organisms or
species of organisms living together in an area. E.g. the study of all organisms in a particular
stream in relation to their environment.
Ecology Concepts
Environment: This refers to all the factors in an organism’s surroundings, living or non-living.
The factors include the place where the organism lives and the physical conditions in the
place, the food, water and air it takes in, the animals that prey on it and the disease that affect
it.
1. Habitat: This is the place where an organism lives. It is the place that is suitable to
the organism’s way of life e.g. the habitat of fish is water.
Examples of habitats include:
i.
Aquatic habitats e.g. puddles, streams, ponds, seas, oceans.
ii.
Terrestrial habitats e.g. savanna, rain, forest, desert, etc.
iii.
Arboreal habitat i.e. tree tops and tree trunks.
2. Ecological Niche: This is the functional role and the space / specific portion of
habitat occupied by a particular organism or species. E.g. a caterpillar and an
aphid may live on the same plant but occupy different positions. The caterpillar lives
on the leaves and feeds on them while the aphid lives on the young shoot / stem and
sucks sap from it. The functional role includes the organism’s behaviour, its feeding
habits and breeding habits i.e. the activities carried out while occupying the spaces in
the habitat.
3. Population: This is the total number of all organisms of the same species or kinds,
living together in a given area / habitat. E.g. the total number of Tilapia fish in a pond
constitutes the population of Tilapia fish in that habitat.
4. Community: This is made up of all the populations of living organisms that exist
together in a habitat. It is any natural occurring group of different organisms living
together and interacting in the same habitat. E.g. the community on a rotting log will
include insects like termites, ants, lizards, small birds and decomposers such as
bacteria and fungi.
5. Biosphere: This refers to all parts of the atmosphere, hydrosphere and
lithosphere where life can be found. It is the largest and highest level of biological
organization and is made up of various ecosystems.
6. Ecosystem: This is self – supporting unit that is made up of a living part and a nonliving part. It is a community of plants and animals interacting with themselves
and with the non-living factors in their environment.
EVALUATION
1. Define ecology
2. Mention four ecological concepts and explain them
Sub- Topic 2: COMPONENTS OF AN ECOSYSTEM
The living part of the ecosystem is called its biotic component while the non-living parts are
called the biotic component.
(a) Biotic component: This includes all living things/organisms in an environment. It is also
called the biotic community. It is made up of;
i.
Food producer’s e.g. autotrophs (green plants), chemosynthetic bacteria and
protophyta.
ii. Food consumer’s i.e. heterotrophs such as animals, protozoa and some bacteria.
iii. Decomposer’s i.e. saprophytes like fungi and some bacteria.
(b) Abiotic component: This consists of abiotic resources and abiotic conditions
Abiotic resources: These are what organisms need so as to stay alive. E.g. sunlight (a source
of energy) and inorganic nutrients like water, nitrogen, carbon dioxide, phosphorus etc.
Abiotic conditions: These are those factors that determine the kind of organisms that are
found in a particular ecosystem. These factors affect the behaviour, growth and breeding
patterns of organisms, they include;
(a) Climatic factors such as temperature, wind, light intensity, humidity, water currents,
turbidity, rainfall, e.t.c.
(b) Edaphic factors such as soils, rocks, topography, etc.
other factors include air, water, storms, etc.
Characteristics of an Ecosystem
(i) there is a flow of energy
(ii) there is recycling of inorganic nutrients.
The major interaction between the biotic and abiotic components involves feeding. Food
producers like plants, trap sun-light energy and nutrients (e.g. carbon dioxide, nitrogen) etc.
from the abiotic environment to make food. The energy and nutrients in the food is passed on
to heterotrophs (consumers) such as animals which feed on plants or on one another. The
animals and plants eventually die and decomposers feed on them thereby obtaining their own
energy. However in the process, the decomposers release the nutrients in the animals and
plants back into the abiotic environment (i.e. the soil). These nutrients can be re-used again
by the food producer’s. Plants also give out oxygen during photosynthesis and this is used by
animals for respiration. Animals give off carbon dioxide during respiration which plants take
up.
NB: As the energy in food is passed from one organism to another it eventually escapes into
the environment and cannot be re-used.
EVALUATION
1. Define (a) biotic factor (b) abiotic factor
2. Give two examples each of the concepts defined above
3. What characteristics make an ecosystem a self- supporting unit.
Sub – Topic 3: BIOMES
Biomes are large natural terrestrial (land) ecosystems. It is the largest community of
organisms interacting with the non-living environment. Biomes are identified by their
vegetation. Examples include forest, desert, savannas, etc. The type of vegetation is largely
determined by climatic factors especially rainfall and temperature, as such, regions in the
world which have similar climates also have similar biomes.
Local Biomes In Nigeria
This can be grouped into two major zones
(1) The forest zone
(2) Savanna zone
(1) The forest zone: This is made up of vegetations having mainly trees, they
include:
(a) Mangrove swamp: A forest of tall woody trees with aerial roots. The
rainfall is high and the soil is water logged throughout the year.
Plants here include the white and red mangroves, raffia palms and coconut.
Found in states like the Delta, Cross River, Bayelsa etc. The climate is hot and wet
throughout the year. Rainfall is heavy usually above 2500mm and the average monthly
temperature is around 26ºc for most months of the year.
(b) Tropical Rainforest: Consists of tall trees with buttress roots, with evergreen and broad
leaves. The trees exist in canopies i.e. different layers, and prevent sunlight from reaching the
forest floor, thus the vegetation on the forest floor is sparse. Epiphytes and climbers are
common features in the trees.
The climate is hot and wet throughout the year. The mean annual temperature is 27ºc while
the mean total annual rainfall is 2000mm. These forests are found in states like Oyo, Edo,
Cross River, Ogun, Ondo, Imo and Rivers State.
(2) Savanna zone: This is made up mainly of grasses and includes;
(a) Southern Guinea Savanna: Consists mainly of tall grasses, with a few tall trees with
broad leaves. The trees are scattered and deciduous. Examples include the locust beans trees,
shear-butter and isobelina.
It has a moderate rainfall of between 100-150cm per annum. They are located in Enugu, Kogi,
Benue, Kwara, Osun, Oyo, Ebonyi, and Ekiti States.
(b) Northern Guinea Savanna (Sudan Savanna): This has short but numerous grasses. The
trees are scattered, short and deciduous. The trees have thorns while others have thick barks.
The trees include acacia, date palm, baobab and silk cotton plants.
The rainfall is low, about 50-100cm per annum. They may be found in states like plateau,
Kaduna, Bauchi, Niger, Taraba, Adamawa and Kano.
(c) Sahel Savanna: It has very short and scanty grasses. There are short and tough shrubs or
trees. The plants are mainly drought resistant and scattered examples include acacia, gum
arabic and date palm.
The temperature is very high and rainfall is very low, below 50cm per annum. It may be
found in States like Bornu, Katsina, Sokoto, Yobe, Kebbi, Zamfara, Kano and Jigawa.
EVALUATION
1. What is a biome and how can it be identified?
2. Mention the two major biomes in Nigeria and the types
OBJECTIVE TEST
1. Epiphytes are usually found in (a) grassland (b) desert (c) forest (d) marsh land
2. The highest amount of rainfall is recorded in (a) Rainforest (b) Mangrove swamp
(c) savanna (d) desert
3. The Sahel savanna is found in …….. state of Nigeria (a) Akwa Ibom (b) Kogi
(c) plateau (d) Zamfara
4. Most trees in the savanna region (a) have buttress roots (b) have pneumatophores
(c) are deciduous (d) are ever green
5. Which of the following is not an abiotic factor? (a) air (b) food (c) light (d) water
WEEKEND ASSIGNMENT
Make a drawing of the map of Nigeria and outline the local biomes
SUGGESTED PRACTICAL
Make a local visit to any nearby vegetation and make a report of your observations.
WEEK 2
TOPIC: BASIC ECOLOGICAL CONCEPTS
CONTENT: 1. Major biomes of the world
2. Population studies by sampling method
3. Ecological factors
4. Simple measurement of ecological factors
5. Relationship between soil types and water holding effects of soil
on vegetation
Sub – Topic 1: MAJOR BIOMES OF THE WORLD
Zones of different biomes occur from the equator to the arctic and to the antarctic due to
differences in climate. In the equatorial and tropical areas where temperature and rainfall are
high all year round, tropical forests occur while in the cold arctic regions, treeless plains
called tundra are found.
Climates change with distance from the equator and also with height above sea level, as such
zones of different biomes occur from the equator to the poles and on a mountain side.
Examples of major biomes of the world
(1) Tropical rain forests: These consist of dense forests with many types of trees, epiphytes
and climbers. Rainfall is abundant throughout the year and an average temperature of 27ºc is
recorded throughout the year. Located around the equator e.g. around coasts of West Africa,
Amazon basin of South Africa, etc.
(2) Temperate forests: These consist of broad-leaved deciduous trees which shed their
leaves during winter. A lot of different plants grow at many levels from the ground as the
trees are not densely packed as in the tropical forest. It has a moderately wet climate and a
dry or cold season. Examples are found in North America, lowlands of North – West Europe
(e.g. France), and Britain.
(3) Coniferous forest: These consist of needle leaved, evergreen conifers e.g. pines, fires and
spruces. Only a few types of tree are found in these forests. Other plants such as shrubs, ferns
and mosses are also present. The temperature is cool and rainfall is light. There is also light
snow. Examples are found in Eurasia and North America.
(4) Temperate shrubland: Consist of drought-resistant shrubs, aromatic plants and dwarf
trees. The temperature is very high (over 30ºc), rainfall is low, the summers are hot and dry
and the winters are mild and rainy. Examples are found in North-Eastern Brazil, Australia,
and close to the Sahara in West Africa.
(5) Savanna: These are tropical grasslands with few scattered trees. It has a moderately dry
climate, a warm dry season and a hot rainy season. Examples are found in Central America,
Interior of Brazil, West Africa, East Africa, and South-East Asia.
(6) Temperate grassland: Consist of large stretches of perennial grasses growing on very
fertile soil. Examples are the steppes, prairies, plains, pampas and veld. The climate is
moderately dry with a cold winter and hot summer. Examples are Found in the interior
continents in Asia, North America, South America, (Argentina), South Africa and Australia.
(7) Desert: Consist of very sparse vegetation which are mainly succulent perennials with
deep root systems and annuals which exist mainly as seeds, germinate and grow rapidly,
flower and produce seeds during brief periods of rain. Rainfall is very low and temperature is
very high. E.g. Sahara desert (North Africa), Arabian Desert (Arabia), e.t.c.
(8) Tundra: Consists of treeless marshy vegetation composed mainly of dwarf shrubs,
grasses, sedges, lichen and moss. The climate is clod with long icy winters and very short
summers. The average temperature is 10ºc. Examples are the coastal strip of Greenland,
Northern Canada and Alaska, Arctic seaboard of Eurasia.
(9) Mountain vegetation: Consist of evergreen rain forest occurring on the slopes of
mountains. The forests are less luxuriant than the tropical rain forest. The Afro-alpine
vegetation occurs at height above 3000m on mountains. The vegetation consist mainly of
heaths, grasses and sedges. In Africa it is found in Cameroon mountain, Kenya highland and
Kilimanjaro mountain. Temperature decrease with altitude. Rainfall is heavy on the
windward side and less on the leeward side of the mountains.
EVALUATION
1. List six biomes of the world
2. Briefly discuss two biomes of the world.
Sub – Topic 2: POPULATION STUDIES
A population is defined as the total number of organisms of the same species living together
in a given area at a particular time. In any ecosystem, the community is made up of many
populations of different species.
To study a habitat’s populations, the following are usually investigated.
1. The type of organisms in the habitat: This involves listing all the different types of
populations found in that particular habitat. This helps to determine the relationships that
exist between the different organisms in the habitat.
2. The dominant species: This refers to the species of organisms in a community which exert
a great influence on the habitat and on the other populations. Dominance may be expressed in
terms of their number, size, the portion of space occupied and contribution to the energy flow
of the habitat.
3. The characteristics of the population: This refers to;
(a) Population size: The total number of individuals of the same species in the habitat (the
total numbers of individuals in a population). A large population stands a better chance of
surviving unfavourable conditions such as fires, diseases, harsh climate changes, while a
small population can be easily wiped out. A large population also has the advantage of
increasing its vigour through breeding which invariably increases its ability to withstand
adverse conditions.
(b) Population density: This is defined as the number of individual organisms per unit area
or volume of the habitat.
Mathematically represented as;
Population density = Total population or Population size
Area of habitat.
Example: If an area of land of 100m² has an elephant grass population of 1000 plants, the
density of elephant grasses will be;
Total number of individuals
Total area
= 1000 elephant grasses
100m²
= 1OØØ elephant grasses
1ØØm²
= 10 elephant grasses / m²
Population density can be used to estimate the total number of individuals of a population i.e.
population size.
(c) Population frequency: This refers to how often the species occurs at different sites in its
habitat. It is recorded as the number of times the organism is sited (seen).
(d) Population growth rate: This refers to the total and final effect of birthrate and death
rate of organisms in the habitat.
(e) Percentage cover: This is the area of ground or space covered (or occupied) by a given
species its habitat. It is expressed in percentage.
(f) Distribution: This refers to the way in which individuals of a particular population are
arranged in a given habitat. The individuals may live in clumps, they may be evenly spaced
or randomly spaced.
Example: If the western half of the habitat contained ¾ of the elephant grasses, then,
Density = ¾ x 1000 = 75Ø = 15 grasses / m²
5Ø
Methods of studying populations
To conduct population studies the following procedure is used;
i.
Choose the habitat to be studied
ii. Choose a sampling method
iii. Identify the species in the habitat
iv.
Collect, count and record the different types of organisms present.
v. Repeat the population studies at different periods.
The following methods can be used to study specific populations;
1. Collection of plants: In a small area plants are easy to count and their distribution can be
recorded on a map or scale diagram of the area, however for larger areas quadrats or transects
are used.
(a) Quadrat Sampling: A quadrat is made of a square or rectangular piece of wire, plastic,
wood or metal frame with predetermined area. E.g. the area of a quadrat may be 25cm². A
quadrat is used to sample the number of plant species in a habitat. It is not suitable for
sampling animals because they move around so much. A quadrat is used by throwing it over
the shoulder at random several times and on each landing, the area covered/enclosed by it is
observed. The type of plant species and their number within the quadrat are recorded. From
the results, the average number of plant per m² is calculated. If the area of the habitat is
known, the total number of plants it contains can be estimated.
Permanent quadrats, with mapping grids attached can be made to study seasonal variations of
plants. These quadrats are sturdier, larger and remain permanently fixed on a marked area.
(b) Transect method: A marked tape is used in this method. The tape is marked at
convenient intervals and then stretched across the area to be studied. The plants encountered
at the interval marks are counted and recorded. This procedure is repeated a few times. In this
way, a fairly accurate estimate of the number and types of plants in the habitat are obtained.
Plants are usually collected in plastic bags and then pressed and dried in a plant press. The
dried plants are mounted on stiff paper, fixed in position with masking tape/cellotape and
labeled with both the scientific and common names.
(2) Collection of Animals: Animals are more difficult to collect than plants; however their
presence can be inferred by looking for signs of their presence such as nests, eggs, feaces,
tracks, feathers, etc and by studying the vegetation with which they are associated. To study
animals different types of nets and traps are used in capturing them. The following methods
can be used.
(a) Capture - Recapture method: In this method animals of one type in a particular area are
caught, counted and marked with ink and released. Their number is recorded as A1. The
following day another set is captured and the number recorded as A2.This second batch may
include animals which had been caught and marked the previous day, their number is
recorded as A3. The population of animals present in the area is found using the formula;
Population in area = A1 x A2
A3
This method is based on the assumptions that;
i.
Individuals do not move out of or into the ecosystem
ii. The marked individuals are randomly distributed in the population.
iii. The marked individuals are a random sample.
iv.
The initial capture and markings do not influence recapture.
v. That none of the marks have worn off during the interval between the two catches.
NB : The results obtained by this method are approximations.
(b) Collection of soil animals with quadrats: The soil animals in an area can be studied by
collecting samples of soil from several sites chosen by tossing a quadrat randomly. A 25%
sodium chloride solution is added to each soil sample and the animals are collected as they
float in the solution.
For earthworms, the sites chosen with the quadrat are irrigated with 25% formalin solution
and the earthworms are collected as they move to the surface of the soil.
EVALUATION
1. What are the major investigations carried out when studying a habitat?
2. A pond with an area of 200m² has a duckweed population of 1,500 plants. Find
(a) The population density
(b) If the western half of the habitat contained ¾ of the duckweed. What is the density of the
eastern half?
3. Explain what a Tullgren’s funnel is and what it is used for.
4. Make a list of traps used for capturing animals for study and describe how captured
animals are kept or preserved.
Factors That Affect Populations
Populations in a habitat may show changes in size or distribution. These
changes may be due to;
1. Natality (birth rate): Increase in birth rates especially during breeding periods, lead to
increase in population size while a decrease in birth rate results in a decrease in the
population.
2. Mortality (death rate): This refers to the rate at which organisms die. An increase in
death rate leads to a decrease in the population and vice versa.
3. Immigration: This is the movement of organisms from different habitats into a particular
habitat. This increases the population size of the habitat being moved into.
4. Emigration: It is the movement of organisms out of a habitat ant it leads to a decrease in
the population. Emigration may be caused by scarcity of food, unfavourable conditions,
seasonal climate changes or breeding purposes.
5.Availability of food: An abundance of food in a habitat tends to lead to an increase in the
population of organisms due to increase in birth rate (reproduction) and influx of organism
from other areas and vice versa.
6. Seasonal climate changes: Adverse climate changes may lead to a decrease in number of
organisms due to death or emigration. Favourable conditions leads to an increase in
population.
7. Natural disasters e.g. fire; flood, drought etc. may lead to a decrease in population due to
death and emigration.
(others include availability of water, availability of space, war)
Sub –Topic 3: Ecological Factors
These are factors in the environment that influence life in the ecosystem. These factors affect
the living organisms or cause changes in the habitat (aquatic or terrestrial).
These factors are grouped into two
(i) Biotic factors
(ii) Abiotic factors.
(i) Biotic factors
The biotic factors are those concerned with the effects of plants and animals on one another
in a given habitat e.g. competition, predation parasitism, etc.
(ii) Abiotic factors.
Abiotic factors include climate topographic (or physiographic) and edaptic (soil factors).
Variations in the ecological factors bring about changes in the habitat. Abiotic factors also
determine the type of biotic community found in a habitat.
Ecological Factors Affecting Terrestrial Habitats
(1) Topographic Factors: These factors are associated with the structure of the habitats e.g.
effects of hilts, valleys, plains mountains and rivers. These factors bring about variation in the
vegetation and types of animals in an area.
Topographic factors include:
(a) Altitude (elevation): This refers to height of the land above sea level. This affects the
growth of plants and the level of erosion in an area. As altitude increases, temperature falls by
approximately 1ºc per 150metres, as a result of this, mountain tops are generally cold places
cold air causes clouds to condense and fall as rain, thus the annual rainfall on mountains is
high especially on the windward side. As one ascends a mountain, the air become less dense,
there is less of it to filter the sun’s rays, so organisms at the top of mountains are exposed to
intense solar radiation.
(b) Slope: Water flows faster on a steep slope than on a gentle slope as such, run-off is
greater and less water sinks into the soil on steep slopes. Also, erosion tends to be more.
Gentle slopes are more favourable to plant growth.
(c) Exposure: This refers to the extent to which living things are not protected from climatic
factors such as rainfall, sunshine and wind. Exposure is usually high on mountains and low
within a forest. Winds tend to be stronger in exposed habitats and relative humidity is lower
than in sheltered habitats. Low degree of exposure ensures the availability of nutrients to
plants.
(2) Edaphic Factors: These are factors related to the nature of soil particles. The word
edaptic refers to the influence of soils on plants and animals. Differences in the soil of a
locality usually produce difference in vegetation since plants are dependent on the soil and
the type of plants determine the type of animals that will be found in the habitat. Edaphic
factors include:
(a) Soil Types: this could be sand, loam or clay. The type of soil determines the fertility of
the soil, its porosity and water retaining capacity.
(b) Soil Texture: The amount of sand, silt and clay in a soil affects its water retaining
capacity. Soil texture refers to the degree of fineness or coarseness of soil particles. It also
affects leaching and erosion.
(c) Soil structure: This refers to the arrangement of the various soil particles in soil. This
affects the level of soil aeration and percolation and the type and level of soil organisms in
the soil.
(d) Soil pH: The pH of soil also affects the type of plants in the habitat e.g. some plants grow
best in acid soils while others prefer alkaline conditions.
(3) Atmospheric factors (Relative Humility): This is a measure of the amount of moisture
in the air. It affects the rate of transpiration from plants and evaporation from animals. As
relative humidity falls, evaporation and transpiration rise as such organisms that live in areas
where humidity is low must prevent water loss from their body surfaces. E.g. in deserts, the
leaves of plants like the cactus are reduced to spines to prevent loss of water.
Ecological Factors That Affect Aquatic Habitats
(1) Salinity: This refers to the concentration of salts in the water. Salinity affects the
movement of water and salts across the body tissues of aquatic organisms. Salinity is low in
fresh water, high in sea water and moderate in brackish water. Aquatic organisms have to
maintain the osmotic balance between their body fluids and their aquatic surroundings in
order to survive. Those living in fresh water have adaptive features which enable them get rid
of excess water that enters their bodies; those living in sea water have body fluids with almost
the same salt concentration as the sea water while those living in brackish water have body
tissues that can tolerate wide and sudden fluctuations in salt concentration of their body fluids.
(2) Depth Of Water: As a body of water becomes deeper, the amount of light and dissolved
oxygen become less, so at the bottom of deep lakes and oceans, there may be too little light
for photosynthesis as such no green plants can grow there. Shallow bodies of water such as
ponds are usually well supplied with oxygen and light and support a lot of plants and animals.
However, these habitats are subject to evaporation and drying up in the dry seasons, the
plants and animals therefore have to develop adaptation to survive such conditions. E.g.
formation of cysts by some protozoans.
(3) Turbidity: This refers to cloudiness of water. It is caused as a result of suspended
materials in water. Light penetration is low in cloudy or muddy water and this hinders green
plants from growing at some depths.
(4) Dissolved Gases: This refers to dissolved oxygen. Oxygen concentration of water
decreases with depth. Oxygen is required by most aquatic organisms for respiration as such
organisms which live in stagnant or very deep water have to be able to tolerate low levels of
oxygen concentration. Organisms that require high oxygen concentration, usually live near
the surface of deep water or in fast-flowing rivers and streams e.g. the simulium larva lives in
fast flowing streams.
(5) Tides and Wave Action: Tidal movement refers to the regular rise and fall in the level of
the sea. Organisms which live in the intertidal zone of a seashore have to be able to tolerate
being alternately covered by sea-water and then exposed to air twice daily.
Wave action is also important both in the intertidal and splash zones of the seashore. Most
organisms in these areas are attached to the substratum or live in burrows. Some attach
themselves firmly to rocks and other immovable objects, while some others have hard body
covering to prevent evaporation of water from their bodies. Waves cause the aeration of the
surface waters of the open sea, thus enabling aquatic organisms to have sufficient supply of
dissolved gases for their needs.
(6) Speed of Flow (currents): Plants and animals are affected by the rate at which the water
flow. Some organism’s e.g. spirogyra prefer to live in slow moving stagnant water while
others e.g. Tilapia, prefer fast-flowing water. Many organisms which live in fast-flowing
rivers and streams have adaptations which serve to prevent them from being swept away from
their support by currents in water. Water currents increase aeration and the turbidity of the
water. Currents also carry warm water to colder regions and this affects the distribution of
organisms.
(7) Density: Density of water varies with the type of habitat. The density of fresh water is
about 1.00 while that of sea water is 1.028 at atmospheric pressure and 0ºc. It is easier to
move through air than water because water is more dense, as such aquatic organisms have a
streamlined shape to help them move easily through water. Some organisms that float on the
surface are sensitive to changes in density e.g. eggs of aquatic organisms sink to different
depths depending on the density of the water.
Ecological Factors Common To All Habitats
The ecological factors that affect both the terrestrial and aquatic habitats are mainly climatic
e.g. temperature, rainfall, relative humidity, wind, high intensity hydrogen ion concentration
(pH) and pressure. Of these factors temperature and rainfall determine the type of vegetation
in a region.
(1) Temperature: This refers to degree of hotness or coldness. Variation in temperature
results in hot or cold climate. It affects the terrestrial habitat more than the aquatic habitat. In
the terrestrial habitat temperature varies with season, while in the aquatic habitat it decreases
with depth.
A rise in temperature usually results in a higher rate of transpiration in plants and higher rate
of metabolism in most animals (except homoiotherms). Most living organisms are killed by
high temperatures and it reduces the performance of some. Low temperatures lead to
inactivity or dormancy. In some organisms (e.g. tadpoles, insect larvae and bacteria) a rise in
temperature results in faster rate of growth and shorter length of life-cycle. A higher rate of
evaporation of water from the soil, ponds and lakes and a lower relative humidity are also
observed.
Too high or too low temperature inhibits the growth and life activities of living things.
However most organisms have various adaptive features that allow them to live at low or
high temperatures e.g. Bears living in the arctic regions have very thick furs.
(2) Rainfall: Rain is the main source of water to most organisms. It also supplies water to soil
on which land plants depends. It is also the major source of water in rivers, ponds, lakes,
oceans etc. The amount of rainfall in an area has a major effect on the type of vegetation
found there. Low amount of rainfall usually causes drought on land and drying up of
freshwater habitats (which leads to death of animals). Too much rain causes floods and
destruction of vegetation through erosion.
Rainfall increases relative humidity and also increases turbidity of streams, rivers and lakes.
Rainfall is necessary for seed germination. It helps to dissolve nutrients in the soil thus
making them available to plants. It is also necessary for the vegetative growth of most crops
e.g. flowering and proper development of groundnut pods.
Rain water may form puddles and small pools which provide temporary habitats for mosquito
larvae, algae and tadpoles. It is also necessary for the start of new termite colonies.
(3) Light: Light is necessary for photosynthesis in green plants. It affects the productivity of
crops and facilitates flowering and fruiting in some plants. Light is the ultimate source of
energy for all organisms. Light affects the activities of animals e.g. some animals are active
during the day (butterfly) while others are active at night (cockroaches). The ultra-violet rays
of the sun enable animals to manufacture vitamin D.
(4) Wind: Winds are important because they cause water currents and waves thus mixing
water and making food available in aquatic habitat, Winds carry rain bearing clouds. They
also determine a season e.g. In Nigeria, the S/W wind is responsible for the rainy season
while the N/E wind brings the harmattan. Wind has drying effects (on land) and so it
increases the rate of transpiration in plants. In an area exposed to strong winds only
xerophytes can grow there. Winds also aid pollination of flowers and dispersal of seeds and
fruits. Winds increase the rate of evaporation from the soil and in savanna and desert areas it
is a major cause of soil erosion. Winds also play an important role in the establishment of
insects in a given area.
(5) Pressure: Atmospheric pressure decreases from the depths of the ocean upwards to the
higher attitude of the atmosphere. Plants and animals have special adaptations to a particular
level of pressure to enable them survive. For instance in the oceans, the pressure increases by
1.03kg/m² every 10m, so organisms found at depths of about 400m live in conditions of
enormous pressure but are well adapted to such conditions and will not survive at levels with
lower pressure.
(6) Hydrogen ion Concentration (pH): This refers to the acidity or alkalinity of the soil or
water in a habitat. pH affects the types of plants and animals in a habitat. E.g. some plants
grow best in acidic conditions while others can only grow in alkaline conditions. In aquatic
habitats pH varies with the salinity of the water. Freshwater is neutral while sea water is
fairly alkaline (pH 8.5). Organisms like the freshwater mollusks (Mytilus) are usually absent
in water with a pH less than 6 (i.e. acidic water).
Biotic Factors Affecting the Ecosystem
Biotic factors refer to the effects of plants and animals on themselves or one another. The
biotic factors include:
(1) Parasitism: One organism called the parasite lives in or on another organism called the
host. The parasite benefits while the host suffers harm or may die.
(2) Competition: This may occur between organisms of the same species or different species.
Competition may be for food, space, mates, etc. One of the organisms will eventually over
come the other.
(3) Commensalism: This involves two organisms living together. One of the organisms (the
commensal) benefits from the association while the other organism neither benefits nor is
harmed.
(4) Predation: This involves an organism (called the predator), killing / feeding on another
organism (the prey).
(5) Trampling: Grazing animals trample on plants and invertebrates.
(6) Pollination of flowers by insects (this aids continuity and increase).
(7) Aeration of the soil by some animals e.g. earthworms, termites, etc.
(8) Support provided to climbing plants by trees or bigger plants.
(9) Shade provided by trees, etc.
Evaluation
1. State five ecological factors that (a) affect terrestrial habitats (b) affect aquatic habitats (c)
are common to both habitats
2. Discuss two of each set of factors mentioned above.
Sub – Topic 4: SIMPLE MEASUREMENT OF ECOLOGICAL FACTORS
(1) Temperature: This is measured using a mercury thermometer read in degree celcius (ºc).
At least two readings are taken in a particular area of the habitat being studied to ensure
accuracy. A soil thermometer is used for soil temperature, a maximum-minimum
thermometer for recording the highest and lowest temperature of the day, and a waxed bulb
thermometer for temperature of water at different depths in a pond, stream, etc. The waxed
bulb thermometer is usually tied to a string knotted at regular intervals to indicate depth.
Outdoor thermometer
Thermometers
(2) Rainfall: This is measured with a rain gauge. This can be made from a tin can, a plastic
funnel and a 50ml measuring cylinder. The amount of rainfall is calculated in millimeters,
with the formula
d
D²x h = rainfall for a period where;
d = diameter of mouth of funnel
h = height of rainwater in the cylinder
D = diameter of collecting cylinder
Usually, the height of the water in the cylinder indicates the amount of rainfall after every
storm.
(3) Relative Humidity: Is measured using a wet and dry bulb hygrometer, or a pocket
hygrometer. The pocket hygrometer is exposed to air and the reading taken after the lever
arm has stabilized. The wet and dry bulb hygrometer is swung in air for 30seconds and the
reading on the thermometers taken and converted to relative humidity units using a table of
conversion. The hygrometer may also be kept in a Stevenson’s screen.
(4) Wind: Wind has both speed and direction. Wind direction is measured / indicated by a
wind vane while wind speed is measured with an anemometer (recorded in ms‫־‬¹).
(5) Light Intensity: Is measured by a light meter or photometer. The readings on the meter
are expressed in lux units. The greater the intensity of light, the higher the readings on the
meter and vice-versa.
(6) Pressure: Atmospheric pressure is measured with a barometer. It is measured in millibars
(or millimeters of mercury, mmHg). The readings are taken directly from a scale.
Aneroid barometer
Mercury barometer
(7) Water Depth: Is measured with a meter rule or a marked and weighted line knotted at
one meter intervals. The meter rule is attached to a weighted line to ensure that it is vertical in
water.
(8) Water Flow: To measure the speed of flow of a water body, the distance (m) covered per
unit times by a float is taken. The float may be a weight tube and the distance covered has to
be pre-determined. Speed of the current is calculated in meters per second. A simple waterspeed meter can be used to compare the speed of water flow at different positions in a stream
(9) Turbidity: Is measured by slowly sinking a weighted white disc called a secchi disc into
the water, noting the depth at which it just cannot be seen anymore. This is not a real
measurement of turbidity but a useful method of comparing the turbidity of different aquatic
habitats, different sites of the same habitats, or at different times.
(10) Slope: Is measured with a simple slope gauge constructed with a meter rule to which a
protractor is attached. The angle readings on the protractor are read and recorded. Small
angles indicate a steep slope.
(11) Height: The height of objects like tall trees is measured using the principle of similar
triangles.
EVALUATION
State five ecological factors and describe how they are measured.
Sub – Topic 5: RELATIONSHIP BETWEEN SOIL TYPES AND WATER HOLDING
EFFECTS OF SOIL ON VEGETATION
Soil is the uppermost layer of the earth’s crust which provides support and nutrient for plants
growth and habitat for some animals. The soil is a complete mixture of mineral matter,
humus, air and living organisms. Soil is classified on the basis of the size of the particles
present in it. Soil particles vary in size and chemical composition, depending on the types of
rock from which they were formed and how they were weathered. Those soils with a high
proportion of sand are known as sandy soils; those with a high proportion of clay and silt are
called clayey soils and those with nearly equal amount of sand, clay and silt are known as
loamy soils. The proportions of these particles in the soil have an important effect on their
properties and on the types of plants found on them.
Types of Soil
(1) Sandy Soil: This contains 80% sand and gravel and 20% of the other types of particles
taken together. Large coarse particles of sand and gravel predominate.
(2) Clay Soil: This contains more fine clay (60%) and silt particles.
(3) Loamy Soil: This contains a mixture of both clay and sand with some humus in roughly
equal proportion. Loamy soils are the most fertile and the humus in it gives it a mellow tilth
i.e. the size of the soil particles and the air spaces between the particles are the most suitable
for cultivation.
Effects of Soil On Vegetation
Soil factors play an important role in determining the vegetation of a region. Soils account for
the variation in type of plants that are found in regions with similar climates. To support a
rich growth of plants, soil must have the following characteristic;
(i) A rich humus content
(ii) A rich mineral content
(iii) A good water-holding capacity; this is determined by the amount of humus and clay in it.
(iv) Good soil porosity; determined by the humus, sand content and soil texture.
Sandy soil is low in plant nutrient and so it supports scanty vegetation or grassland. Clay soil
has a little more amount of plants nutrients than sandy soils and thus can support light
vegetation such as shrubs. Loamy soil is very fertile and can support luxuriant vegetations
such as a forest.
Water-Holding Capacity of Soil
Water holding capacity of soil refers to the ability of the soil to retain water. The amount of
water retained by any soil depends or the size of the particles, the humus content, aeration,
temperature and presence of microbes. Clay and humus retain a higher amount of the water
than sand. In clay soil, most of the water is held firmly to the surface of the soil particles
(hygroscopic water) and this is not usually available to plants. In sandy soil very little
amount of water is retained as most of it drains off. Loamy soil is able to retain more water
within its particles. This is called capillary water and is available for plants use.
SUGGESTED PRACTICALS
1. Experiment to Determine The Water Retaining Capacity of Soil Types
Title of experiment: To compare the porosity and water holding capacity of three soil types
Materials required: Three measuring cylinders of 100cm³, cotton wool, three funnels, water,
dry sand, dry clay, dry loam, stop clock, balance.
Method: Stand the three funnels in the three measuring cylinders and block the funnels with
cotton wool.
- Place an equal weight of dry sand, dry clay and dry loam in the three funnels respectively.
- Pour 50ml of water onto each sample at the same time and allow to drain.
- Allow the set up to stand for an hour or until the water has stopped dripping through each
funnel.
- Read the level of water in the measuring cylinder.
Calculations:
(a) Rate of drainage / porosity is calculated from the amount of water collected in the
measuring cylinder. The more the water, the more porous the soil sample. Usually porosity is
highest in sandy soil because it has large pore spaces and large particle sizes, followed by
loamy soil and then clay soil which has the least drainage because of its tiny pore spaces and
fine particles .
(b) Water holding / retaining capacity is calculated as follows;
Volume of water added to soil = 50ml
Volume of water collected in cylinder = xml
Volume of water retained in the soil = (50-x) ml
The percentage of water retained in each of the soil samples will be
(50-x) x 100 = Y%
50
Observation: It is observed that water drained out from the sandy soil faster than the loamy
soil and finally the clay soil. It was also observed that clayey soil retained more water than
loamy soil and least retained by the sandy soil.
Conclusion: Sandy soil is more porous than loam which is more porous than clay. Clayey soil
retained more water than the loamy soil and the sandy soil retained the least amount of water.
2. Experment To Compare The Capillary Action Of Soil Types
-Take three wide glass tubes and plug each at one end with cotton wool.
- Nearly fill the tubes with the three soil samples separately.
- Clamp the tubes upright in a trough of water,
- Allow the set-up to remain for 3-6 hours
- Observe every 30mins.
Observation: It will be observed that at the early stage of the rise of water in the three tubes, it
was faster in sandy soil than the clay and loamy soil samples, however by the end of the
experiment the water had risen to the highest levels in loam, followed by clay but remained at
a low level in the sandy soil.
Conclusion: Loamy and clayey soils have greater capillary actions due to their tiny pore
spaces. The presence of organic matter in loam also enhanced its capillary. The sandy soil
had poor capillary action because of its large pore spaces and large particles.
EVALUATION
1. List the three major soil types.
2. Discuss the constituents of the soil types mentioned.
3. Compare the water holding capacities of the three soil types.
WEEKEND ASSIGNMENT
OBJECTIVE TEST
1. The distribution of plants in a rain forest is governed mainly by ……..(a) amount of
sunliught (b) rainfall pattern (c) soil type (d) vegetation
2. The turbidity of a water body can be measured using (a) hygrometer (b) light meter (c)
rain guage (d) secchi disc
3. The number of organisms of a particular species is termed ………(a) community (b)
ecosystem (c) synecology (d) population
4. All these are ecological factors affecting all habitats except ……(a) humidity (b) rainfall
(c) temperature (d) wind
5. Which of the following world biomes is strictly mountain vegetation? (a) Afro-alpine (b)
deciduous forest (c) Mangrove (d) savanna.
ESSAY QUESTION
(1) Describe how the height of a forest tree can be measured.
(2) In a table outline the properties/characteristics of the three major soil types (at least ten
properties)
(3) Make large well labeled drawings of a maximum and minimum thermometer; a rain
gauge, a wind vane, an anemometer, a light meter, a secchi disc, a barometer and a slope
gauge.
WEEK 3
TOPIC: FUNCTIONAL ECOSYSTEM
CONTENT: (a) Autotrophy and Heterotrophy (i) Producers (ii) Consumers (iii) Aquatic and
Terrestrial
In this topic, the question a wise student will ask is; what is ecosystem? First of all, the word
‘eco’ simply means ecology so, it is ecological system. Let us consider this illustration, in a
freshwater habitat where you have aquatic plant such as spirogyra, animals such as tilapia,
frogs and toads. All this living things interact with the non- living environment which
includes the water where they are, the atmosphere, and the soil beneath it. These living things
in the environment together with the non-living environment constitute an ecological system
or ecosystem. Therefore, an ecosystem is defined as the interrelationship between the
living things and their non-living environment
COMPONENTS OF AN ECOSYSTEM:
In an ecosystem, there are two major parts; the biotic or living and abiotic or non-living part.
Then from the functional point of view, we have three kinds as producers, consumers, and
decomposers. The producers are always green plants; the consumers are the animals, while
the decomposers are the saprophytes.
Under the consumers we have the following:
1.
2.
3.
4.
Primary consumers, e.g. grasshopper, rat etc.
Secondary consumers, e.g. cat, lizard etc.
Tertiary consumer, e.g. hawks, snakes.
Omnivores, e.g. man, domestic fowl.
Decomposers are organisms which feed on the carcasses of dead producers and consumers
and in the process bring about the decay of such carcasses. Large decomposers such as
insects and earthworms are called macro decomposers, whereas small decomposers, such as
certain bacteria and fungi are known as micro decomposers.
SOME PRODUCTS OF DECOMPOSITION
In the process of decomposition, dead organic matter is broken down physically and
chemically, and this is done in stages. Now, the product of this decomposition is inorganic
compounds like carbon (iv) oxide, ammonium, ammonium compound as well as salts of
elements present in the organic matter. Some gaseous products such as carbon (iv) oxide,
ammonia and hydrogen sulphide can be identified as organic matter decomposes.
Intermediate products of decomposition include sugars, and complex organic compound
derived from protein.
ROLE OF DECOMPOSERS
The role of decomposers is the recycling conversion of materials of dead organic
materials into inorganic materials which are available to the producers in the ecosystem.
Coral Reef in the Red Sea
Coral reefs represent the most complex aquatic ecosystem found on Earth. Although coral reefs can be found
between 30 degrees north and south latitude, the greatest concentration is found between 4 degrees north and south
latitude in the western portions of all major oceans. There are two broad categories of coral reefs: shelf reefs and
oceanic reefs. Shelf reefs include fringing reefs, platform reefs, bank reefs, and barrier reefs and are located on the
continental shelf, while oceanic reefs are found off the continental shelf growing around the margins of volcanic
islands. Coral reefs support greater numbers of fish and invertebrate species than any other ecosystem in the ocean.
EVALUATION
1. Define the term ecosystem.
2. List the two major parts of the ecological system
3. Outline four classes of consumer with on example each.
4. Write the two types of decomposers.
OBJECTIVE TEST:
1. A domestic fowl belong to (a) omnivores (b) quaternary consumer (c) primary
consumer (d) secondary consumer (e) tertiary consumer.
2. Some gaseous products of decomposition include all of these except (a) ammonium
Chloride (b) carbon (iv) oxide (c) ammonium (d) hydrogen sulphide (e) hydrogen
oxide.
ASSIGNMENT
i. Write short notes on (a) autotrophs (b) Heterotrophs.
ii. Sketch the organogram of the ecosystem
iii. Find out the group of consumers the Carnivores belong.
iv. Give an instance in writing to show how living things interact with their non living
environment.
SUGGESTED PRACTICAL
Carry out an activity to show that heat is released during decomposition.
SUB-TOPIC: FOOD CHAIN, FOOD WEBS AND TROPHICAL LEVELS
As living and non-living things interact, energy is transferred from one level to the other. The
ecosystem actually operates as a movement where all organisms depend on the primary
producers, the green plants.
I. FOOD CHAIN
Food chain is the transfer of food energy from producers (green plants) to a series of
organisms in a habitat. In the arrangement of the food chain, the natural rule is that it must
start from a producer or an autotroph. Some examples of food chain are below:
1. Grass
Grasshopper
Lizard
Snake.
2. Plankton
Tilapia
Water snake.
3. Dead wood
Termite
Frog
Hawk.
Note: that each level of competition in the food chain is called a trophic level. Looking at
example 1, it represents the terrestrial habitat.
II. FOOD WEB: considering food chain energy pathway, you will observe that it is a single
energy pathway. In the actual sense, such simple food chains as shown above rarely exist
within a community because consumers rarely depend on only one type of food. Often a
particular food item is eaten by more than one consumer. Therefore, a network of
interrelated food chains forms what is called a food web.
III. TROPHIC LEVEL
Now, what is this trophic level? These are stages at which the energy is found as it moves
through the various organisms or levels of transfer in the ecosystem. Hence, trophic level
refers to the part of food chain.
IV. FOOD PYRAMID
Food pyramid is a representation of food chain in the food producers from the base and
carnivores from the apex.
V. PYRAMID OF NUMBERS:
This is the progressive drop in the population at each higher or successive trophic level of the
food chain or the relative decrease in number or organisms in a food chain as one ascends the
higher trophic levels.
VI. PYRAMID OF BIOMASS: The pyramid of Biomass (or standing crop) indicates, by
weight, the total mass of individuals or organisms at each trophic levels.
a pyramid of biomass
VII. PYRAMID OF ENERGY: This is the progressive drop or decrease in the total
available energy at each higher trophic level or the progressive diminution of energy in
the feeding chain as one ascends the higher trophic levels.
Differences btw pyramid of numbers and pyramid of energy
Pyramid of Numbers
Pyramid of Energy
Size of organism is not recognized, only This is based on a common unit of energy
numbers are counted
joule
Shape is not constant, it might be inverted Shape is constant
e.g. grasshoppers feeding on a large tree.
NON-CYCLIC NATURE OF CHEMICAL ENERGY TRANSFER
The energy flow in an ecosystem is not cyclic because being an energy pyramid, it moves
from the producers at the bottom of the pyramid up to a point where it cannot be used by
living things anymore. It is either used by the organisms in the ecosystem or it is lost to the
atmosphere. For example, energy stored in cow = energy stored in grass – (energy for cow’s
activities + energy lost to the atmosphere).
NUTRIENT MOVEMENT
Nutrient movement refers to the chemical energy in form of carbohydrates, fats, protein, and
other nutrients are distributed among producers, consumers and decomposers. It just about
how nutrients flow from one energy level to the other in the ecosystem.
ENERGY FLOW
Under this topic, we shall consider the following: Food pyramid, Pyramid of Numbers,
Pyramid of biomass, and Pyramid of Energy. In any natural community, the number of
individuals at the lower part of the food chain or web is greater than those above. Producers
are therefore greater than primary consumers, and secondary consumers less in number than
the primary consumers. This number reduces till the terminal group of organism is reached
which have no predators depending on them for food. When these numbers are
diagrammatically represented, a pyramid of numbers is obtained.
EVALUATION
1. Explain the following with a typical example: Food Chain, Food Web, and trophic
level.
2. Why is the energy flow in the ecosystem not cyclic.
3. What is nutrient movement?
4. Write a short note on energy flow.
5. State two the differences between pyramid of numbers and the pyramid of energy.
GENERAL EVALUATION
1. In aquatic habitat, one of these is a primary producer (a) plankton (b) grass (c) tilapia
(d) shark (e) Amoeba
2. Which of the following organisms feed directly on green plants? (a)decomposer (b)
secondary consumer (c) producer (d) primary consumer (e) tertiary consumer.
3. Trophic levels refers to the part of (a) biosphere (b) hydrosphere (c) a habitat (d) a
food web (e) a food chain.
WEEKEND ASSIGNMENT
1a. Define the term (i) consumers (ii) producers.
b. Classify the following organisms: cow, bacteria, green plants, herbivores, fungi, and man
into producer, primary, secondary and tertiary consumer.
2. Sketch a diagram of typical food web
WEEK 4
DATE: ………………………
TOPIC: ENERGY TRANSFORMATION IN NATURE
CONTENT:
1. Energy Loss in the Ecosystem (i) Solar radiation (ii) Energy Loss in the Biosphere
(iii) Measure of primary production e.g. the amount and rate of energy fixation
2. Laws of thermodynamics.
Sub-Topic 1: ENERGY LOSS IN THE ECOSYSTEM
You remember that energy exists in various forms, and various forms are interconvertible and
as such one form of energy can be transformed into one another form. In nature, energy
transformations are brought about by living organisms. Their activities cause energy to flow
through ecosystems unidirectionally. Now, how does energy get lost in the ecosystem?
Solar Energy: Only about 2% of solar energy is used by green plants while the rest is lost to
the earth’s surface. Thus, energy is a limited factor in the production of autotrophs.
Energy Transformation in Nature
When primary consumer, the herbivores feed on the producers, the green plants, the
secondary consumers, the carnivores in turn feed on the herbivores; the energy transferring
efficiency in each stage is about 5-20% while the rest is lost to the atmosphere.
Energy Laws: Energy transformations in nature are governed by the laws of
thermodynamics.
The first law of thermodynamics states that when one form of energy is converted into
another, the total quantity of energy is constant (there is no net loss or gain in energy) that is
to say that energy is neither created nor destroyed. Hence, in the process of burning, chemical
energy of wood changes into heat and light. In a motor vehicle, energy in form of fuel
changes into mechanical energy. So, energy can only be converted from one form to the other.
Second Law Of Thermodynamics: The law states that when one form of energy is
converted into another, a proportion of it is converted into heat. The second law of
thermodynamics is sometimes known as the entropy law; entropy being a measure of disorder
in terms of unavailable energy in a closed thermodynamic system.
How the Laws are Used to Explain Energy Flow across the Trophic Level
Pyramid of energy
1. According to the first law, energy is transferred into a variety of other forms in the
successive trophic level but the sum total is constant.
2. Using the second law, we observe that during energy transformation in the successive
trophic levels, a proportion of it is converted into heat which is lost, hence the
progressive drop in energy in successive trophic levels and also the pyramidal shape
of feeding relationship.
Food Chain
1. In accordance with first law, chemical energy stored in plants, can be converted into
light energy in glow- worm which in turn is converted into electrical energy in fire-fly
and when eaten by man, it is converted into mechanical energy in muscular
contraction without any loss or gain.
2. The second law shows that when energy flows through a food chain, only a small
proportion of the energy taken up by each link is transferred to the next step. This is
because at each transfer, most of the energy is lost as heat.
According to the second law:
1. In the flow of energy from herbivore to carnivore, there is loss of usable energy. This
loss of energy means that les life can be maintained at highest trophic level.
2. The energy travels from one organism to another with a loss of energy each time it
enters another organism. The various organisms represent trophic levels or stages of
energy flow.
EVALUATION
1. State the laws of thermodynamics
2. Explain the term entropy law.
3. How does law of thermodynamics apply to pyramid of energy?
GENERAL EVALUATION
1. The first law of thermodynamics states that (a) energy is gained but not lost (b) there is
no net gain or loss of energy (c) energy is converted only once (d) the conversion of
energy is specific and non directional (e) energy is loss through enthalpy.
2. Only about ---percent of solar energy is used by green plants (a) 10% (b) 20% (c) 2% (d)
5% (e) 80%
WEEKEND ASSIGNMENT
1. Explain what happens when heat is lost in a food chain.
2. Explain various ways through which energy flow from the producer to you.
WEEK 5
SUB TOPIC 2: EFFECTS OF AGRICULTURAL ACTIVITIES ON ECOLOGICAL
SYSTEMS.
Agricultural activities involve both growing of crops as well as rearing of farm animals.
Ecological system refers to the interrelationship between living organisms and their
environments. The natural dynamic balance between plant and animal communities in the
ecosystem is often disturbed by agricultural activities such as burning and tillage. Bush
burning
Roadside Market in Bulgaria
People buy red peppers and other vegetables at a farmers’ market in a suburb of Sofia, the capital of Bulgaria.
Although privatization of Bulgaria’s economy has been slow, most farmland once controlled by the state is now
owned by independent farmers.
In many places, some areas used for cropping is always set on fire before the cropping season.
The ash produced by the burnt rubbish increases the alkaline content of the soil. This replaces
the acidity of the soil in most tropical African soil. In contrast, burning exposes the soil
surface to erosion by wind and rain, reduces the humus content of soil, destroys microorganisms of the soil, kills small animals such as insects and earthworms, and destroys other
important plants and animals. As a result, the balance of the ecosystem is disturbed by bush
burning.
Pesticides
The use of pesticides in some cases disturbs the dynamic balance of the ecosystem in some
unexpected ways. Insecticides affect both beneficial and harmful insects. DDT is a very
stable compound; instead of being excreted by animals, it is stored in their body fats when
such fat is oxidized during respiration in some animals, harmful quantities of DDT may be
librated into the blood.
Effects of different types of farming have effects both desirable and undesirable on ecological
systems.
Different kinds of farming have effects both desirable and undesirable on ecological systems.
These effects are explained below.
(a) Shifting cultivation: the method is possible where population is small and where land
is abundant. Ecologically, large population with small land results in overuse which
inturn leads to total loss of soil fertility.
(b) Crop rotation: crops grown are rotated in success seasons. The method gives better
yield for respective crops because different crop make different demand of mineral
elements of the soil.
(c) Mixed farming: this involves keeping livestock and growing plants side by side. As
the product of crops is being used as food to feed livestock, the remains (faeces) of
the livestock can also be used as manure for the farm crops.
EVALUATION
1. List three agricultural activities that disturb ecological system.
2. State four effects of bush burning on ecological system.
3. Name three farming methods and explaining how one of them affects the
ecological system.
ASSIGNMENT
State three advantages and disadvantages each of the following:
i. Shifting cultivation
ii. Crop rotation
iii. Mixed farming
iv. Mixed cropping
v. Pastoral farming
vi. Mono cropping
vii. Bush fallowing
SUB-TOPIC 3: PESTS AND DISEASES OF AGRICULTURAL IMPORTANCE
Pests are insects or animals which cause damage to farm, animals, plants, food and crop.
Some pests attack crops and animals in the farm. A disease is a departure from normal state
of health, expressing remarkable symptoms or outward visible signs. Both pests and diseases
reduce the quality and quantity of crop and animal yield or even kill them.
PLANT AND PESTS
The most devastating pests of crops are insects e.g. grasshoppers, locusts and caterpillars.
Other plant, pest includes nematodes, rodents and birds. Insects and rodents always destroy
stored crops like cocoa, coffee, groundnuts and yam. Pests cause plant diseases. Specific
plant pests include the following:
i. Caspid bugs of cocoa: they feed on leaves, stems and pods. The pest is more
prevalent in dry season. Caspids are controlled by spraying with Aldrex 40, BHC,
Dieldrin and Gamalin 20.
ii. Cotton stainer bugs are commom in cotton growing are. They are tiny, red-coloured
insects which pierce the young bolls and seeds in the open bolls and suck the sap.
iii.
iv.
These insects transmit viral, fungal and bacterial diseases from one plant to another.
The fungus causes the boll to rot internally and stain the ling.
Yam beetles can destroy a whole yam crop plantain within a year. The pests are
controlled in Nigeria by treating yam setts and seeds with Aldrin just before planting.
Other pests of yam are eel-worm which feed on tuber rodents and wild animals which
destroy the tubers.
Pests of cassava are grasshoppers that feed on the leaves and young shoots, some
rodents that feed on cassava tubers and stems and untethered goats and sheep can eat
up all the leaves and stems of cassava.
Control of plant pests
Pest control is aimed at protecting crops from damage and getting rid of the pest population.
Control measure of plant pest can b applied through the following methods:
-
Physical method e.g. handpicking of pests and deterrents such as bird scares on small farm
area with low infestation.
Cultural method: modifying farm practices to discourage pest multiplication.
Chemical method i.e. use of pesticides.
Biological method e.g. introduction of predators.
Sterilising male technique.
Natural Pest Control
Ladybird beetles, or ladybugs, have had their name since the Middle Ages, when people looked upon
them as a gift from the Virgin Mary because of their miraculous eating habits. As both larvae and adults,
ladybugs feed on aphids and other agricultural pests. Many gardeners buy ladybugs at garden stores and
release them in their gardens to stave off aphids
PESTS OF ANIMALS
Animals or livestock pests are often parasitic on their victims. Livestock pests are either
ectoparasites or endoparasites.
i.
ii.
Ectoparasites: some of them are vectors of diseases e.g. ticks vectors of tick fever and heart
water disease of cattle, sheep and goats. Other ectparasites of livestock are lice, nites, fleas
and flies.
Endoparasites: these include flat worm (e.g. tapeworm and liver fluke) or round worm (e.g.
Ascaris, Hookworms) or protozoa e.g. Trypanosome and coccidian which cause coccidiosis.
Endoparasites injure the tissue or organs in which they live. They cause wasting, stunting and
death of livestock when they occur in large numbers.
Control of Endoparasites
Two main effective ways of controlling endoparasites are:
i.
The use of appropriate drugs as directed by the veterinary department.
ii.
Proper management to ensure that domestic livestock does not come in contact with the
parasitic eggs or larvae.
SOME DISEASES OF PLANTS
Diseases of plants are commonly caused by fungi, bacteria and virus. The table below
Table: Summary of the causes, symptoms and control.
DISEASE
CAUSATIVE
HOST
MAJOR
ORGANISM
SYMPTOMS
Anthracnose
Fungi
Black pod
Fungi
Brown spot
Fungi
Bacterial wilt
Bacteria
Mosaic
Virus
Cocoa, coffee, Brown,
water
cotton and oil soaked patches
palm
on leaves and
pods
Cocoa
Dark brown, or
black rot on pod,
damage to fruit
and seed walls
Maize
Purplish-brown
spots on leaves.
Entire plant may
break up.
Banana,
Leaf wild and
plantain,
defoliating. Wilt
cassava, tobacco of entire plant
and groundnut
Cassava
and Leaf-mottling
tobacco
with dark green
and
greenish
yellow patterns
CONTROL
MEASURES
Use
fungicides
of
Spraying with
fungicides, farm
sanitation
Avoid planting
on infected spots
Use of clean
planting
material, good
sanitation
Use of resistant
varieties
SOME DISEASES OF ANIMAL
The common diseases which affect domestic animals could be grouped as follows:
i.
ii.
iii.
iv.
v.
Bacterial diseases e.g. black quarter, anthrax, foot rot, fowl pox, tuberculosis and contagious
abortion.
Fungi disease e.g. ringworm
Nutritional disease e.g. rickets, milk fever, ketosis, bloat and osteoporosis.
Protozoan diseases e.g. coccidiosis, tick fever and trypanosomiasis (sleeping sickness)
Viral diseases e.g. foot and mouth diseases, foul cholera, Newcastle disease, pleuropheumonia,
rinderpest and typhoid fever.
Table: Selected Domestic Animal disease
DISEASE
CAUSATIVE
HOST
ORGANISM
Coccidiosis
Protozoan
Cattle,
foul,
sheep, and goat
Anthrax
Bacteria
MAJOR
SYMPTOMS
Bloody diarrhea,
weakness,
emaciation and
death
CONTROL
MEASURES
Good sanitation.
Avoid
overcrowding.
Disinfected
sulphamethazine.
Cattle, goat, pig Premature birth, Vaccination of
and sheep
still-birth,
young animals
Newcastle
Virus
Ringworm
Fungus
Rabies
Virus
retention
of
afterbirth
and
sterility
Poultry
Yellowish
droppings, comb
turns
purple.
Coughing,
gasping
and
death
Cattle
and Lesions at the
horses
base of hairs.
Hairs fall off
and itching
Cats, cattle , Excitement,
dogs,
horses, tendency
to
sheep and pigs
attack, paralysis
in coordination
and death
before age of
breeding. Good
sanitation.
No
effective
cure. Kill off
infected
bird.
Disinfected pens.
Consult
a
veterinary officer
Use fungicides
to wash lesions.
Use antibiotics
as oral treatment
No
effective
treatment.
Control
by
vaccination and
avoiding
exposure
to
infection.
EVALUATION
State three general effects of pest and diseases on crops and animal.
Name two plant pest and how they can be effectively controlled.
State two main effective ways controlling endoparasites of livestock.
Use a table to describe the causative organism, the host, the major symptoms and control
measures of the following diseases:
(a) Mosaic (b) black pod (c) coccidiosis (d) ringworm.
1.
2.
3.
4.
GENERAL EVALUATION
OBJECTIVE QUESTIONS
1. The following are examples of cereals except (a) maize (b) rice (c) millet (d) bean
2. Which of the following does not belong to the major four divisions of plant kingdom
(a)
thallophyta (b) tracheophyta (c) pteridophyta (d) bryophyte
3. Which of the following pest control method involves the use of pest enemies? (a) cultural
method (b) biological method (c) physical method (d) chemical method
4. Which of the following is affected by black pod diseases? (a) oil palm (b) cocoa (c) rubber (d)
cowpea
5. Which of the following diseases is caused by a virus? (a) mosaic (b) brown spot (c) black pod
(d) anthracnose
ESSAY QUESTIONS
1. (a) List any four main divisions of the plant kingdom.
(b) List any ten classifications of plants based on the nature and uses of their products, giving two
examples in each group.
2. (a) In a tabular form state any five differences between monocotyledons and dicotyledons.
(a) Discuss any five agricultural practices that have harmful and beneficial effects on these plants
stating their effects on these plants and how they can be controlled.
3. Mention any four pests of named plants and how they can be controlled.
4. (a) List any five groups of animal diseases and give one example each.
(b)Briefly discuss the effects of bush burning on a piece of farm land.
5. (a) State four ways of controlling plant pests and discuss any two of them.
(b) Use a table to explain the causative organism, host, major symptoms and control
measures of the following diseases (i) coccidiosis (ii) Newcastle (iii) anthracnose
(iv) brown spot.
WEEKEND ASSIGNMENT:
List five environmental factors that affect the production of crops and identify any way by
which farm crops are wasted.
WEEK 6
SUBJECT: BIOLOGY
CLASS: SS1
RELEVANCE OF BIOLOGY TO AGRICULTURE
CONTENT:
1. Food production and storage
(a) Ways of improving crop yield
(b) Causes of wastage
(c) Methods of persevering and storing food.
2. Population growth and food supply
3. Relationship between availability of food and human population (effects of
storage).
4. Government efforts to increase food production (e.) agricultural revolution.
SUB-TOPIC 1: FOOD PRODUCTION AND STORAGE
The primary aim of agriculture is to provide adequate food for an ever increasing human
population. The issue of food production, preservation, storage and wastage has been
challenging to both the agriculturist and the government.
Adequate food production makes food available for teaming population to be well fed. It also
earns the country foreign exchange through exportation of food crops. One the other hand,
food shortage will increase death rate and cause migration of people to where food is
available. There will be competition among organism which in turn leads to starvation and
cannibalism. Natality or birth rate will be affected through avoidance of marriage.
(a) WAYS OF IMPROVING CROP YIELD
Crop yield can be improved through the following ways:
(i) Breeding high yielding crops that are resistant to plant and animal disease.
(ii) Using fertilizers and organic manure to maintain soil structure and fertility and ensure high
crop yield.
(iii) Using effective method of farming such as irrigation, tillage and draining systems.
(iv) Combating weeds by using herbicides instead of cutlasses and hoes.
(v) Plant protection from pests and disease to improve yield.
(vi) Putting more land under use by motivating and formulation policies that will get more
people to be involved in farming.
(vii) Practicing mechanised farming to obtain high yield. Tractors and modern farm implement to
be adopted instead of manual farming.
(viii) Conservation of land to keep and maintain soil fertility. Soil erosion should be prevented,
bush burning should be avoided while mulching and crop rotation should be encouraged.
(ix) Use of correct agricultural practices such as removing weeds regularly, giving adequate
spacing and planting at the right time will improve crop yield.
(b) CAUSES OF WASTAGE
Reasons why crops are wasted annually on farms include the following:
i.
ii.
iii.
iv.
v.
vi.
vii.
viii.
Late harvesting of crops: some crops are over ripe, rot and fall off due to lateness in
harvesting.
Bad harvesting techniques and incomplete harvesting. Harvest should be invested on and
used. Man may skip maize harvest and such maize may be wasted.
Delay in transporting crops which make some drops to rot.
Lack of good storage facilities; good barns and storage facilities should be made available. If
harvested crops are not properly stored wastage will occur.
Infections of farm produce by fungi, insects and vermin due to inefficient storage method.
The decay of some stored crops caused moisture, especially when they are not properly
stored e.g. groundnut, maize and rice.
Lack of good roads and good means of transportation for carrying farm to the market or
urban centres.
Poor method of preservation of some farm produce like tomatoes, carrots, vegetable and
other perishable crops.
METHODS OF PRESERVING AND STORING FOOD
The methods commonly used in preservation and storage of foods include the following:
i.
ii.
iii.
iv.
v.
vi.
vii.
Drying: food items such as meat and fish can be dried to preserve food and prevent damage.
Drying remove water from food and prevent growth of organism that can cause decay.
Salting: common salt is added to fish and meat. Salt kills the bacteria by high osmosis
pressure.
Refrigerating/ freezing: keeping food at low temperature prevents bacteria growth. Meat,
fish and vegetables are preserves in this way.
Smoking: this removes water from food and prevents growth of microbes on food. Microbes
are killed by poisonous substances such as phenols, present in the smoke.
Canning: if the food is sealed and air excluded, growth of micro organisms will be
impossible. High temperature kills the microbes and kills the microbes and keeps the food.
Chemicals: the application of preservatives and protective chemicals on the food keep pests
away and also prevents bacteria and fungi from growing on the food, thereby preventing
decay.
Pasteurisation: it is special method of preserving milk. Milk is pasteurised by heating to 72%
for 15 seconds and then cooled rapidly. This destroys micro organisms, thereby preventing
the milk from becoming sour very quickly.
Other methods of food preservation are fermentation and radiation.
Pest Control or Pollution?
Pest control has become a difficult issue for farmers because of its potential environmental impact. Although the
insecticide being sprayed on this potato field will eliminate a generation of Colorado potato beetles, it may also
contaminate local food and water sources.
EVALUATION
1.
2.
3.
4.
List three dangers of inadequate food supply to the population.
State four ways of improving crop yield.
State five causes of crop wastage
List seven method of food preservation
SUB-TOPIC 2: POPULATION GROWTH AND FOOD SUPPLY
Population can be defined as the total number of organism of the same species living in a habitat over
a period of time. Food supply affects population growth both positively and negatively, based on
availability or unavailability of food in a habitat.
If food is adequately available organism will be well fed, give birth to new ones; death rate reduces
and population rises. When there is inadequate supply of food, the organism is malnourished, there is
competition for the limited food, birth rate reduces, death rate increases and there is a decline in
population of the organism. The number of organism migrating out of the habitat increases and
cannibalism may set in.
Factors affecting population growth include the following:
i.
Reproduction (birth rate)
ii. Migration (movement of organism)
iii. Death (death rate)
iv.
Availability of food
v. Availability of space
vi.
Availability of water
vii. Natural disaster
viii. Famine
ix.
War
Experiment to demonstrate effect of food on population
Aim: to show the effect of food on mice population.
Method: some mice or rodents are kept it two cages. Those in cage 1 are provided with a lot of food
and water at the beginning of the experiment. Those in the second cage are supplied with enough food
and water continually. The mice left for some time.
Observation: the number of mice continues to increase in the cage with food continuous supplies of
food. The population of mice in the cage with food supplied only once will increase for a while when
there is no food most of them start to die.
Conclusion: the population of mice tends to increase when there is plenty of food, while their
population tends to decrease when there is no food.
EVALUATION
i.
Define population.
ii. State three factors that influence population of an habitat
iii. List three effects of inadequate food supply on population
iv.
Describe an experiment that shows the effect of food supply on population.
SUB-TOPIC 3: RELATIONSHIP BETWEEN AVALABLE FOOD AND HUMAN
POPULATION
Malthusian hypothesis that human population increases by geometric progression while food
increases in arithmetic progression, is an indication that relationship exists between population and
food supply. At a point therefore, population will outgrow the supply of food and population growth
will stop at one point. Malnutrition, hunger and possibly death will follow to reduce the population to
the level the food can cater for.
Starving Children in Niger
Due to climate, drought, poor agricultural planning, political instability, war, and the mismanagement of natural
resources, there were about 820 million undernourished people in the developing world in 2006. Only a small
percentage of hunger deaths are caused by starvation. Most hunger-related deaths are the result of chronic
malnutrition, which weakens the body's ability to fight diseases. In 2003, almost 16,000 children were dying from
hunger-related causes each day.
EFFECTS OF FOOD STORAGE
Naturally, some crops are meant to grow in wet season while some few are grown in the dry
season. If there is no good storage facilities, distribution of food across the season will be
difficult; as there would be a period of plenty of food and another period of food shortage. To
strike a balance, storage facilities will make equitable distribution of food and food will be
available in required quantities at all seasons. Advantages of food storage include the
following:
i.
Provision of employment opportunities i.e. to workers in processing industries.
ii. Provision of adequate food supply during period of war and natural disaster.
iii. Stabilisation of food prices at all season. Equitable distribution of food will prevent
unnecessary high demand for food at any time which may lead to like in prices of
food.
iv.
It ensures economic use of food by preventing spoilage at time of plenty and adequate
supply of food at off-harvest period.
v. Provision of foreign exchange to improve the economy of the nation. Food can be
used as aids to countries in need as love and donations.
EVALUATION
1. Name five crops that are produced during the wet season but are scarce during the dry
season.
2. State two needs for food storage.
3. State four importance of food storage.
Agriculture in Iraq
Agriculture, an important part of the Iraqi economy, became even more essential after the United Nations (UN)
imposed trade sanctions on the country in 1990, following Iraq’s invasion of Kuwait. Iraqi farmers grow grains,
dates, grapes, figs, and other crops, while nomadic and seminomadic Iraqi herders raise livestock. Yet before the
UN trade embargo, Iraq had imported approximately 70 percent of its food. This photograph shows an Iraqi
farmer bagging grain.
SUB-TOPIC 4: GOVERNMENT EFFORTS TO INCREASE FOOD PRODUCTION
Many African countries has embarked on gigantic agricultural development programmes that
failed
Because of undefined government policies, absence of planning, lack of skilled and
experienced personnel and inadequate provision of funds by the government.
In Nigeria, huge finance invested in various governments’ agricultural programmes (such as
Operation Feed the Nation and Green Revolution) was grossly mismanaged. Gross financial
management has also crippled many of the River Basin Authorities established by the Federal
Government to boost agricultural production.
Factors that adversely affect food production include:
i.
Unfavourable climatic conditions e.g. drought;
ii. Lack of improved varieties of plant and livestock.
iii. Conservative attitude of local farmers
iv.
Inability of many farmers to use modern farming techniques and;
v. Outbreaks of insect pest and diseases.
Government should do the following to aid crop production
i.
Provision of irrigation system to supply water for planting at all season.
ii. Provision of modern farming equipment to replace manual clearing equipment used
by farmer.
iii. Provision of good roads and other infrastructure that can aid food production,
movement and storage.
iv.
Fertilizer should be made available at reasonable cost to farmers to improve soil
fertility and boost crop production.
v. Training of local farmers in modern day farming to improve their skills.
EVALUATION:
i.
List three agricultural programme established by the government to boast food
production.
ii. State three factors that hinders food production.
iii. State four ways by which the government can improve food in Nigeria.
GENERAL EVALUATION
OBJECTIVE TEST
1. Which of the following factors does not affect population growth? (a) food supply (b) games
and sport (c) reproduction (d) migration
2. Food can be preserve through all except (a) fermentation (b) washing (c) pasteurisation (d)
radiation.
3. Which of the following does not cause food wastage? (a) storage (b) pest (c) diseases (d)
delayed harvesting
4. Which of the following is not an outcome of inadequate food supply to a population(a)
migration (b)competition (c) population growth (d) cannibalism
5. Which of the following factors does not have adverse effect on food production? (a)
unfavourable climate condition (b) outbreak of pest and diseases (c) irrigation system (d)
good road network
ESSAY QUESTIONS
1. (a)List ten method of food preservation.
(b)Discuss any two methods of food preservation.
2. (a)State any five environmental factors that affect crop production.
(c) State any five ways by which farm crops are wasted.
3. (a) list three major consequences of food shortage in the world growing population.
(a) Describe an experiment to show the effects of food supply on population
4. (a) State five causes of crop wastage.
(b) State four ways of improving crop yield and discuss any one of them.
5. (a) Name three agricultural programmes aimed at increasing food production.
(b) State five ways by which government can improve food production in Nigeria.
WEEK 7
BIOLOGY
CLASS: SS1
DATE----------------
TOPIC: MICRO ORGANISM AROUND US
CONTENT:
1. Micro organism in air and water.
(i) Group of micro organisms: bacteria, viruses, some algae, protozoa, fungi.
(ii) Concept of culturing
2. Identification of micro-organism in (i) Air (ii) pond water (iii) river (iv)concept of culturing
3. Micro-organisms in our bodies and food.
4. Carriers of micro organisms – examples, location of the micro-organism in carriers and types
of micro organism.
SUB-TOPIC 1: MICRO ORGANISMS IN AIR AND WATER.
Introduction: Micro-organisms are very tiny living organisms are also known as microbes.
T-Lymphocyte Infected With HIV
Human immunodeficiency virus (HIV) is the cause of acquired immunodeficiency syndrome
(AIDS). By infecting CD4 T-lymphocytes, a type of white blood cell, HIV weakens the
immune system and leaves the infected individual open to deadly infections. The viruses gain
access to a T-lymphocyte by attaching to CD4 proteins on the outer surface of the cell
membrane.
MICROBES
Anthony Van Leeuwenhoek (1632 – 1733) was the first scientist to discover microbes with
his newly invented microscope.
Micro-organisms are dreaded as disease causing agents (germs). However, many microbes
are of great benefits to man e.g. saprophytic microbes that bring about decay of organic
matter. Those microbes that affect man negatively are mainly the parasitic ones which are
called pathogem.
Micro organism are found everywhere- in the air, water, siol, in our own food, on our food on
surfaces of object, and on inside living organisms, on our bodies, inside of our bodies and on
our clothes in shut, anywhere everywhere.
1. Groups of micro organisms:
Microbes are very many and are grouped as follows:
I.
Bacteria
II.
Viruses
III.
Some algae
IV.
Protozoa
V.
Some fungi
Most microbes are unicellular but some fungi and algae are multi-cellular. Several microbes
survive adverse conditions of temperature or humidity by forming spaces the within the cell.
On the return of favourable condition of the spores are released carried in the air and on
landing on suitable substrate grow and produce more spores.
Hepatitis B Virus
The hepatitis B virus (HBV) causes inflammation of the liver. The virus is recognizable
under magnification by the round, infectious “Dane particles” accompanied by tube-shaped,
empty viral envelopes. Symptoms of hepatitis B infection include jaundice and a flulike
illness, while chronic infection can lead to serious problems such as cirrhosis and cancer of
the liver.
I. BACTERIA
Bacteria can be seeing with the use of light microscope. It has a simple structure. It is
unicellular. It is a prokaryotic cell i.e it does not have a true nucleus. Heredity materials are
contained in a strand of DNA (Deoxyribose nucleic acid) inside the cell.
Bacteria can be described based on the following:
i.
Oxygen requirement
ii.
Shapes
iii.
Gram’s staining technique
i. Based on oxygen requirement.
(a) Aerobic Bacteria: This group of Bacteria uses oxygen in respiration e.g. vibrio cholerae.
(b) Obligate anaerobes: This group of bacteria do not utilize oxygen in respiration e.g.
putrifying bacteria.
(c) Facultative anaerobes: These are bacteria that can exist in two states i.e. they can use
oxygen and they can also do without oxygen.
ii. Based on shape.
(a)
(b)
(c)
(d)
(e)
Cocci:- This group are round in shape.
Bacilli:- They have rod-like shape.
Spirillae:- These are spiral in shape.
Vibrios:- They are comma shaped.
Flagellated Spirochaetes:- A number of bacteria have whip-like structure called flagella that
effect their movement.
Drawings Modern Biology Pg 170
iii. Based on Gram’s staining technique.
(a) Gram positive bacteria: retains the purple/violet stain in its peptidoglycan (a large
structural molecule found in the bacteria cell wall)
(b) Gram negative bacteria: loses or do not retain the purple stain in the cells
Bacteria can be the cause of a number of plant and animal diseases.
a) Plant diseases caused by bacteria e.g. web blight in cowpeas, black arm in cotton
etc.
b) Animal diseases caused by bacteria- leprosy, lockjaw, cholera etc.
II. VIRUSES
They are unicellular in nature, without nucleus, cytoplasm and cell membrane. Smaller
than bacteria and can only be seen under electron microscope. Virus lack life. Thus it
cannot respire nor carry out metabolism. They can only survive inside living cells.
Types of viruses
Viruses can be grouped based on:
(a)
Type of nucleic acid (DNA/RNA)
(b)
Nature of Protein coat
(a) Based on type nucleic acid
i. Adenovirus, Herpesvirus (DNA)
ii. Picornavirus, Togavirus, Orthomyxovirus, Paramyxovirus, Coronavirus (RNA)
(b) Based on nature of Protein coat
i. Adenovirus, Herpesvirus, Picornavirus, Togavirus (Icosahedral in nature – i.e
a polygon with 20 faces and 12 corners)
ii. Orthomyxovirus, Paramyxovirus, Coronavirus (helical in nature)
III. ALGAE
They are mainly free-living microscopic plants. They survive in a wide range of habits such as
wet soil, fresh water, sea etc. they have chlorophyll to a number of other pigments giving rise to
green algae, brown algae, blue/green algae etc. examples of algae are: Sprirogyra, volvox, chlamy
domonas,nostoc, Diatoms etc.
IV. PROTOZOA
These are unicellular microscopic animals. They are found in damp soil and water. Some of them
are parasitic while others live freely in their habit. Examples of parasitic protozoa are:
Trypanosome, plasmodium etc. examples of free-living Protozoa are: Amoeba, Paramecium etc.
parasitic protozoans are pathogens that cause disease like Malaria, sleeping sickness, Bilharziasis
etc.
V. FUNGI:
These are non-green simple plants. They feed Saprophytically or parasitically. Saprophytic fungi
such as mucor, yeast, penicilium are useful to man. Parasitic fungi do cause diseases which are
unpleasant to man. Example of animal diseases caused by fungi is: Ringworm, Athelet’s foot,
mouth thrush, candidioses etc. plant diseases caused by parasitic fungi are: mildews, spots, wild,
blights and Rots.
Anatomy of a Simple Bacterium
Bacteria cells typically are surrounded by a rigid, protective cell wall. The cell membrane, also called the plasma membrane,
regulates passage of materials into and out of the cytoplasm, the semi-fluid that fills the cell. The DNA, located in the nucleoid
region, contains the genetic information for the cell. Ribosomes carry out protein synthesis. Many baceteria contain a pilus
(plural pili), a structure that extends out of the cell to transfer DNA to another bacterium. The flagellum, found in numerous
species, is used for locomotion. Some bacteria contain a plasmid, a small chromososme with extra genes. Others have a capsule,
a sticky substance external to the cell wall that protects bacteria from attack by white blood cells. Mesosomes were formerly
thought to be structures with unknown functions, but now are know to be artifacts created when cells are prepared for viewing
with electron microscopes.
CONCEPT OF CULTURING
Culturing is a technique of growing micro-organisms in the laboratory for the studying the
microbes.
The process has to do with:
i. Preparing a sterile medium
ii. Inoculating
iii. Incubating
iv. Examining micro-organism in the medium.
While bacteria, fungi and algae can be grown in test tubes and Petri dishes in culture media,
viruses cannot be grown. They can only grow and multiple inside living cells of an organism.
Through Tissue culture, living tissues and cells of multi-cellular organism are cultured in
appropriate media and studied. To carry out studies involving viruses, are cultured in the
laboratory by injecting the virus into the fertilized Bird egg e.g. egg of duck.
On the culture medium, micro-organisms occur as colonies. Colonies of micro-organism do
clump together in large number of organism of the same kind. Colour, appearance other
characteristics of the colonies enable the investigator to identify and differentiate microbes in
a culture medium.
EVALUATION
1a. What are Micro-organism?
b. List the important groups, giving examples of each group.
2a. Expalin the concept of culturing.
b. What steps will you take in preparing a culture solution and state precautions in preparing
it.
c. Identify sources of samples for culturing.
ASSIGNMENT
1. Read up Identification of Micro-organisms in the Air, Pond water, Rivers and Streams and
Micro-organism in our bodies and food.
2. Read more on concept of culture. Modern Biology Pg 166-170 and
(a) outline different types of culture.
(b) state importance of tissue culture.
SUB-TOPIC 2: IDENTIFICATION OF MICRO-ORGANISMS IN AIR, POND
WATER, RIVER, STREAM
i. Micro-organisms in our bodies and food.
ii. Carries of Micro-organisms, examples, location of the Micro-organisms in carries.
iii. Types of micro-organisms.
MICRO-ORGANISMS IN THE AIR
Micro-organisms commonly found in the air are: Bacteria, Virus and Fungi. These microbes
do not grow in the air but are present as spores in dust and water droplets in the air. These
spores are light and easily dispersed by air movement. When these spores land on suitable
substrate, they germinate, multiply and produce more spores. Micro-organisms found in the
air and examples:
a.
b.
c.
Bacteria: Examples – Pneumococci, Staphylococci, Streptococci, Bacillus anthracis, which
causes anthrax in herbivores.
Virus: examples – Influenza, Polio virus, common cold virus, measles virus.
Fungi: Examples – Sacromyces (yeast), Rhizopus nigricans (bread mould), Penicillium (bluegreen mould) Aspergillus etc.
Bacterial Cultures
Colonies of the bacteria known as Escherichia coli (larger, pink) and Proteus vulgaris
(smaller, brown) grow side by side in this petri dish culture. Under normal
circumstances both of these bacteria harmlessly inhabit the human intestines and aid in
digestion, but can become pathogenic and cause infections, such as urinary tract
infections. Scientists and doctors grow cultures of bacteria and study their
characteristics in order to learn about bacterial diseases and disease prevention.
MICRO ORGANISMS IN WATER
Micro organisms found in water are commonly known as plankton. Aquatic environment,
unlike atmosphere are rich in organic and inorganic nutrients. They can be found in all types
of water habitat viz: wells, ponds, lakes, streams, rivers and seas.
All microbes found in water can be grouped into three as follows:
i.
ii.
iii.
Natural water micro-organisms: these are microbes that are naturally found in aquatic habitats.
Soil micro organism ( washed into the surrounding water bodies during heavy rains)
Sewage micro-organisms

Spirochete
Bacteria, included within the kingdom Prokaryotae, are single-celled organisms
lacking a well-defined internal cellular organization. The bacterium
Leptospirilla ichterohemorrhagiae, pictured here, exhibits the spirochete, or
spiral, structure characteristic of many of the 1600 species of bacteria.
MICRO ORGANISMS IN WATER AND THEIR EXAMPLES:
1. Bacteria: examples – aquatic species of coccus, Baccillus, Pseudomonas, Azobacter,
Thiobacillus, Sarcinina, spirillum, Micrococcus, Vibro and Spirochaeta. These bacteria are
either heterotrophic, autotrophic and chemotrophic.
2. Blue – green algae: examples; oscillatoria, nostoc, anabaena,
3. Protists: these are autotrophic diatoms e.g. chlamydomonas, cholera and some species of
euglena as well as heterotrophic amoeba and paramecium.
4. Algae: these are located close to the shore of where they form thick green floating mesh e.g.
spirogyra, volvox etc. Algae arte major part of primary producers in the aquatic habitat since
they contain chlorophyll and can photosynthesis.
MICRO-ORGANISMS IN OUR BODIES
Various parts of human body such as the skin, hair, mouths, nose, ears, under the nails, our
teeth etc to different micro-organisms as well as serve as entrance for these micro-organisms
into our bodies.
Millions of micro-organisms living inside and outside the human body. These microbes are
non-pathogenic. They are regarded as the normal micro flora which plays importance role in
the body.
This normal micro flora prevents pathogen from invading the body as well as secretes certain
substances that inhibits or kills some other pathogens. Weakened immune systems ,
indiscriminate use of antibiotics, unhygienic practices like smoking and intake of alcohol
malnutrition, stress etc could make non-pathogen to become pathogenic harmful to the body
as the normal micro flora become disturbed.
Pathogens harm the body by using up the hosts’ nutrients thereby starving the tissue of the
host.
Through their actions they damage tissues of the affected part of the host as well as produce
toxins that negatively affect the functioning of particular organs or body systems of the
individual.
Anthrax Bacteria
An electron micrograph shows a cluster of bacteria, Bacillus anthracis, in a capillary of
a lung. The bacteria cause anthrax, a disease in humans and animals that can result in
death. Anthrax can be cured when treated early with antibiotics.
ENTRY OF MICRO ORGANISMS INTO OUR BODY
Micro-organisms enter the human body through;
i.
ii.
iii.
iv.
v.
Buccal cavity: the food we eat and the water we drink. Such pathogen cause air borne
infection like tuberculosis cause by mycobacterium tuberculosis
The nose: Air we breathe in, into the respiratory system such virus normally cause cold.
Damages skin: cuts or bruises on the skin into the blood stream Telamus. fungi infection,
leading to ringworm on the head, foot etc.
Oesophagus: contaminated food or drinking water.
Direct contact: skin surface e.g. fungal infections which result in ringworm of the head and
foot.
MICRO ORGANISMS IN FOOD
The physical and chemical properties of any food determine the type of micro-organisms that
will grow and reproduce. When micro-organisms or their spores get in contact with food,
such food gets contaminated and when consumed man can have adverse effect on the
individual.
CAREER OF MICRO-ORGANISM
Apart from the various means through which microbes get into our body already discussed,
there are certain organisms that carry micro-organisms that can affect man negatively about.
These organisms are called Careers are usually insects and mammals. The hairy nature of the
insect body traps the microbes and gets carried from place to place. The natural habitats of
these insects include latrines, food stores, dung hills and other similar places where microbes
abound. The careers pick up the pathogens and bring them to exposed human food. As they
land on these exposed food to feed on them, the microbes are transferred to the food which
could be eaten by man and consequently bring about infection and diseases. These careers are
called Vectors. The pathogen neither grow nor affect them adversely hence, they are called
Vectors. Vectors are primary to the pathogen while man is the secondary Host.
EVALUATION
1. What are careers? Give two examples.
2. State the habitat of the career named above.
Streptococcus Bacteria
This scanning electron micrograph shows disease-causing Streptococcus bacteria,
commonly found in the human mouth, throat, respiratory tract, bloodstream, and
wounds. Often airborne in hospitals, schools, and other public places, Streptococcus
bacteria are responsible for infections such as strep throat, scarlet fever, and some types
of pneumonia.
LOCATION OF MICRO-ORGANISMS IN CAREERS
Organisms that carry micro-organisms are called Vectors. Diseases caused by career do not
affect the vector that carries them.
The micro-organism found in vector lives in them temporarily for the purpose of developing
to the stage where they can effectively infect man. Thus the pathogens have two hosts. This
phenomenon is killed alternation of hosts. The vector is the primary host while man is the
secondary host of the pathogen. Mosquitoes, Tsetse fly are examples of vectors of
microorganism do not develop inside the housefly. Instead the body of the housefly’s body
“collects” micro-organisms as it parches on exposed human food to feed on it, the microbes
(bacteria) falls off its body onto the food which causes disease unto man when contaminated
food is eaten.
Though biting and sucking man’s blood, Anopheles Mosquito transmits a protozoan –
plasmodium into mans blood causing disease – malaria. The pathogen is in the gut of the
insect and as it feeds on the blood of man, it deposits it into man.
EVALUATION
1.
2.
3.
4.
5.
Define the following terms: (i)natural microflora (ii) pathogen (iii) careers (iV) vectors
Name and describe the two methods by which pathogens are carried from place to place.
List the important groups of micro-organisms and give one example from the group.
What is culture?
Outline the steps you will take in preparing a culture solution.
GENERAL EVALUATION
(Objectives)
1. One of the micro-organisms cannot exist on its own (a) bacterium (b) an algae (c) a virus (d)
fungus (e) protozoa
2. Which of the following can be grown only in a tissue culture? (a) a virus (b) a bacteria (c) an
algae (d) a fungus (e) a protozoan.
3. Which of the following statements is false? (a) micro-organisms exists in water and air (b)
micro-organisms exist inside very small organisms (c) micro-organisms exists inside bodies
(d) hand lens can be used to observe and study micro-organisms (e) housefly are expanded of
vectors
4. Micro-organisms are important in recycling nutrients because; (a) they are capable of
multiplying by space of formation (b) many of them are parasites (c)they are many and are
found everywhere (d) they are capable of breaking dead organic material (e) they can multiply
very quickly
5. Facultative bacteria are ----- (a) unable to survive in aerobic environment (b) unable to
survive in anaerobic environment (c) can only survive in aerobic environment (d) can survive
in both aerobic and anaerobic environment (e) none of the above
ESSAY QUESTIONS
1a.
what do you understand by micro-organisms?
b.
Describe how micro-organisms enter our bodies with examples and steps preventing
them.
c.
list the groups of micro-organism with examples.
2a.
List micro-organisms found in water with examples.
b.
micro-organism in 2a can be grouped into 3, name these groups with short
explanations.
c.
A group of aquatic micro organisms are known as primary producers explain.
3a.
what is culture?
b.
What steps are entails in preparing a culture solution
c.
Outline precautions to observe in preparing a culture solution.
4a.
Describe an experiment to show that atmospheric Air contains micor-organisms.
b.
What are the functions of natural normal micrflora in and on human body?
c.
List two insects and three mammalian vectors, stating the following for each organism:
(i) micro-organisms (ii) Disease caused (iii) possible control of spread
5a.
Define the following terms: (a) natural microflora (ii) pathogen (iii) careers (iv)
vectors
b.
Write short notes on the importance of micro-organism to man in the area of (i)
medicine (ii) agriculture
SUGGESTED PRACTICALS:
1. Preparation of culture solution
2. Examine the presence of microbes in Air, water, saliva, under nail.
3. Classification of bacteria using different criteria
WEEK 8
TOPIC: MICRO-ORGANISMS IN ACTION
CONTENT:
1. Growth of micro-organisms: ways of measuring the growth of microorganisms.
2. Beneficial effects in nature, medicine and industries.
3. Harmful effects of some microbes
Sub – Topic 1:MICRO-ORGANISMS IN ACTION
Micro-organisms are very small living things which are normally not visible to the naked eye
but can be seen with the help of a microscope.
TYPES OF MICRO-ORGANISMS
Micro-organisms include;
(i) All Viruses e.g. Polio virus, Smallpox virus, etc.
(ii) All bacteria e.g. Salmonella, Clostridium, Treponema, Escherichia coli, etc.
(iii) All protozoans e.g. Plasmodium, Trypanosoma, etc.
(iv) Some fungi e.g. Rhizopus (mould) and Yeast (e.g. Saccharomycetes).
(v) Somealgaee.g. diatoms, dinoflagelletes, etc..
(vi)Blue - green algae e.g. Nostoc
Micro-organisms live everywhere, in water, air, soil, inside and outside of plants and animals
including human beings. There are many more microorganisms than visible plants and
animals in the world. They may have beneficial or harmful effects. Micro-organisms that
cause disease are referred to as pathogens and are usually parasitic.
Anthrax Bacteria
An electron micrograph shows a cluster of bacteria, Bacillus anthracis, in a capillary of a lung.
The bacteria cause anthrax, a disease in humans and animals that can result in death. Anthrax
can be cured when treated early with antibiotics.
Growth of Microorganisms
Culturing is the growing of micro-organisms in prepared media in the laboratory. The
prepared medium is called the ‘culture medium’. Bacteria, fungi and algae grow easily in
test-tubes, flasks or Petri dishes of culture media. Virus on the other hand, can only grow and
multiply inside living cells, so they cannot be grown in a culture medium.
Micro-organisms are able to increase in size and multiply in number of cells. The growth of
micro-organisms is measured based on increase in population size rather than increase in cell
size. Under favourable conditions (food, adequate temperature and humidity) microorganisms reproduce asexually by binary fission. Generation time varies from species to
species e.g. rapidly growing specie like Escherichiacoli can divide every 30minutes.
Two methods are used to measure the growth of micro-organisms;
(i) First Method: This involves inoculating a bacterial sample into a nutrient broth. As the
bacterial population increases, the clear liquid medium becomes cloudy / turbid. Increase in
turbidity indicates an increase in number of bacterial cells. Turbidity can be measured using a
spectrophotometer. Thus by measuring the turbidity of a bacterial culture in nutrient broth at
regular intervals, the growth of a bacterial population can be measured.
(ii) Second Method: This involves taking small samples of bacteria from a nutrient broth at
regular intervals of time and diluting the samples several times. Each diluted sample is then
inoculated onto a nutrient agar medium in a petri dish and incubated. The number of colonies
formed in each petri dish is counted and this indicates the number of living bacterial cells in
the diluted sample. From this, the actual number of bacteria in the original sample can be
calculated.
EVALUATION
1. Mention five microorganisms
2. How is the growth of microorganisms measured?
3. Describe two ways of growing microbes in the laboratory.
Bacterium Showing Flagella
Although many forms of bacteria are not capable of independent movement, species such as
the Salmonella bacterium pictured here can move by means of fine threadlike projections
called flagella. The arrangement of flagella across the surface of the bacterium differs from
species to species; they can be present at the ends of the bacterium or all across the body
surface. Forward movement is accomplished either by a tumbling motion or in a forward
manner without tumbling.
Sub – Topic 2: BENEFICIAL EFFECTS
(i) Bacteria in the large intestine of man synthesize the vitamin K that is needed.
(ii) Yeasts are used in baking and preparation of alcoholic drinks. Yeasts are an important
source of vitamin B.
(iii) Some bacteria are used in curdling of milk, brewing of wine and in butter and cheese
making.
(iv) It is used in the production of antibiotics e.g. penicillin from the mould called
penicillium.
(v) Saprophytic micro-organisms decompose sewage into harmless inorganic compounds.
(vi) Most decomposers are micro-organisms and they help to maintain soil fertility.
(vii) Some bacteria living in the rumen of ruminants like sheep, goat, cattle help to digest
cellulose in their food (grasses / vegetation).
(viii) Micro-organisms help in maintaining some cycles in nature e.g. the nitrogen cycle and
carbon cycle. They also help in recycling phosphates and sulphate.
EVALUATION
Name two beneficial microorganisms and state their benefits to man.
Sub-Topic 3: HARMFUL EFFECTS OF MICRO-ORGANISMS
(1) Most diseases in animals and plants are caused by micro-organisms especially bacteria,
viruses and protozoans.
(2) Huge amounts of food are spoiled annually by saprophytic fungi and bacteria.
(3) They also cause deterioration / damage to materials such as paper, wood, cotton, leather,
etc.
(4) Micro-organisms can also cause the death of plants and animals.
Cholera Bacterium
An electron micrograph shows the bacterium Vibrio cholerae, which can cause cholera, a
serious infectious disease in humans. The bacterium produces a toxin that causes the small
intestine to secrete large amounts of fluid, leading to diarrhea, vomiting, muscle cramps, and
sometimes death. A vaccine made from dead bacteria offers partial protection.
Disease-Causing Micro-Organisms
Micro-organisms are spread through the following;
(i) Air: Dust and water droplets in our air contain micro-organisms such as polio virus,
measles virus, pox virus, common cold virus, Pneumococci
(a bacteria), Pencillium (a fungus), etc.
(ii) Water: Bacteria found in water include Bacillus, Pseudomonas, Vibrio, Azotobacter,
Coliform micro-organisms (e.g. Escherichia coli, Vibrocholerae, Salmonellatyphi), etc. Bluegreen algae found in water include Nostoc,Anabaena and Oscillatoria.Protists in water
include Chlamydomonas, Euglena,Amoeba, etc. Algae include Spirogyra, Volvox. Fungi
include moulds and mildews.
(iii) Food: Most micro-organisms in food get in through faeces, dirty utensils and equipment,
unhygienic habits and vectors like flies and cockroaches. Examples are Shigellasp,
Salmonellaenteriditis, Aspergillusflavus, etc.
(iv) Animal vectors or carriers.
(v) Personal or direct skin contact with a sufferer.
Disease-causing micro-organisms can enter the body through body openings like the mouth,
nose or reproductive opening, through wounds, through bites of other animals and through
blood transfusions.
Some important diseases, their causative micro-organisms, mode of transmission, host and
symptoms are outlined in the following tables.
AIR-BORNE DISEASES
Causative
Disease
organism
1) Common cold
Virus
2) Chicken pox
3) Measles
4)Pneumonia
5)Tuberculosis
6) Meningitis
Mode
of
transmission
Host
Airborne
Man
Major symptoms
High fever, headache
running nose.
Pox virus
Airborne
Man
Itchy skin rash
Paramyxo- virus
Airborne
and Children
High fever, skin rashes,
close contact
headache, head cold,
cough, body pain.
Bacteria
Air
Man,
High fever, difficult
birds, pigs, breathing and cough
cows
Myco
bacterium Airborne, food
Man, cow Persistent dry cough and
tuberculosis
profuse sweating at
(bacterium)
night.
Meningococcus
Airborne
Man
High fever, headache,
(Bacterium)
vomiting and stiffness
of the neck.
Streptococcus Bacteria
This scanning electron micrograph shows disease-causing Streptococcus bacteria, commonly
found in the human mouth, throat, respiratory tract, bloodstream, and wounds. Often airborne
in hospitals, schools, and other public places, Streptococcus bacteria are responsible for
infections such as strep throat, scarlet fever, and some types of pneumonia.
FOOD AND WATER BORNE DISEASES
Disease
Causative
Mode
of Host
Major symptoms
organism
transmission
1) Typhoid
Salmonella
Contaminated food Man
High
temperature,
typhi (bacteria)
and water
followed by bloody
diarrhea
2) Cholera
Vibrocholerae
Food and water
Man
Vomiting and diarrhea
(bacterium)
3) Food poisoning Salmonella
sp. Infected
meat, Man
Diarrhea and
(bacteria)
Poultry, eggs, milk
Vomiting
and contaminated
food
4)
Amoebic Entamoebahistolytica Contaminated food Man
Abdominal pain, and
dysentery
(protozoan)
and water
Diarrhea
5) Poliomyelitis Picornavirus (virus)
Infected food and Children
High fever, headache
(infantile
water,
direct
nausea,
fits
and
paralysis)
contact
stiffness of limbs
Spirochete
Bacteria, included within the kingdom Prokaryotae, are single-celled organisms lacking a
well-defined internal cellular organization. The bacterium Leptospirillaichterohemorrhagiae,
pictured here, exhibits the spirochete, or spiral, structure characteristic of many of the 1600
species of bacteria.
VECTOR-BORNE DISEASES
1) Malaria
Plasmodium sp. (protozoan)
2) Sleeping sickness Trypanosomagambiense
(Trypanosomiasis)
(protozoan)
Bite
of Man
infected
female
Anopheles
mosquito
Tsetse fly bite Man
and
domestic
animals
3) Yellow fever
Arbovirus
Bite
infected
Aedes
mosquito
of Man
4) Plague
Bacterium
Bite
infected
flea
of Man
Rat
5)
River
blindness Onchocercavolvolus
(onchocerciasis)
Bite
of Man
infected black
fly
High
shivering
sweating
feve
an
Fever, headach
sluggishness,
drowsiness an
un- controllab
sleep
High
feve
headache,
backache
followed by lo
body temperatur
and jaundice
Shivering feve
cough
an
difficult
breathing
Severe headach
high fever an
gradual blindnes
DISEASE SPREAD BY CONTACTS
1) Tineaversicolor
Dermatophytes
Direct
contact
2) Athlete’s foot
Fungi
3) Gonorrhea
Neisseria
gonorrhoea
(bacterium)
4) Syphilis
Treponemapallidum Sexual
(bacterium)
intercourse
5) AIDS
Human
immunodeficiency
virus. HIV
skin Man
Direct
skin Man
contact
Sexual
Man
intercourse
Man
Sexual
Man
intercourse,
blood
transfusion,
infected sharp
instruments,
mothers
to
unborn child
Yellow patches on
chest, neck, face and
back
Itching,
smelly
patches between toes
Inflamed
urethra
burning
sensation
during urination and
thick
yellowish
discharge in male. In
females there may be
pain during urination,
redness around the
urinary opening and
vaginal discharge.
A small painless sore
or chancre on the
penis or vulva. Mild
fever, skin rashes,
mouth ulcers and
aches in lymph node
regions. It may lead
to abortion, attack
the brain and cause
blindness
and
insanity
Susceptibility to all
microbial infections,
high fever, less of
weight,
chronic
diarrhoea,
skin
rashes, wasting away
of muscles.
EVALUATION
Mention two disease causing microbes, state the diseases caused, the host, the mode of
transmission and the symptoms of the disease.
OBVJECTIVE TEST.
1. The growth phase in bacteria in which bacterial cells divide steadily at a constant rate is
called .……… phase. (a) decline (b) dividing (c) exponential (d) stationary
2. Which of the following microbes causes cholera ? (a) Bacterium (b) Fungus (c) Protozoan
(d) Virus
3. Which of the following diseases is caused by a protozoan? (a) Cholera (b) Gonorrhea (c)
Malaria (d) Measles
4. A disease characterized by high fever loss of weight, chronic diarrhea, skin rashes and
wasting away and final death is (a) AIDS (b) gonorrhea (c) staphylococcus (d) syphilis
ASSIGNMENT
1. How do microorganisms gain access into the body?
2. Describe the stages involved in the growth of inoculated microorganisms (graphical
illustration is important.
3(a) What is a venereal disease?
(b) Mention four venereal diseases
(c) Outline five ways of controlling venereal diseases.
4. Read up on towards better health.
WEEK 9
TOPIC: TOWARDS BETTER HEALTH
CONTENT: 1. Control of harmful microorganisms
2. Vectors (i) definition (ii) ways of controlling vectors
3. Student’s health: maintenance of good health
Sub – Topic 1: TOWARDS BETTER HEALTH: CONTROL OF HARMFUL MICROORGANISMS
Better health can be achieved basically by controlling disease-causing micro-organisms and
their animal vectors and also by improving health facilities.
Harmful microorganisms can be controlled by;
(1) Use of high temperature e.g. sterilization by boiling, autoclaving or heating of food,
water and other products to kill micro-organisms.
(2) Use of drugs / antibiotics e.g. chloroquine kills plasmodium parasites.
(3) Use of antiseptics which kill or inhibit the growth of pathogenic micro-organisms.
(4) By immunization or vaccination against diseases such as measles, tuberculosis, polio,
etc.
(5) Covering of food and water always to prevent contact with vectors.
(6) Destruction of vectors such as mosquitoes, flies, rats, etc.
(7) Use of disinfectants e.g. Lysol, carbonic acid, etc.
(8) Use of salt; this inhibits the growth of microbial cells and prevents their multiplication.
Salt can be used to preserve food and wash cuts and wounds to prevent infection.
(9) Dehydration inhibits the growth of microbes; food can be preserved by drying. Drying in
the sun can be used to kill micro-organisms in bedding blankets and clothes.
(10) Promoting health education.
(11) Quarantine services.
(12) Personal hygiene such as regular bathing, brushing of teeth, washing of hands before
meal and after defecating, etc.
(13) Maintaining good health: This helps us to resist most pathogenic micro-organisms.
(14) Use of ultra-violet radiation to kill bacteria
EVALUATION
1. List six ways by which you can control harmful microorganisms
2. Explain 4 ways by which one can maintain good health.
Sub –Topic 2: VECTORS
Non-living agents that carry micro-organisms from one place to another include air, water
and food.
Living agents that carry micro-organisms from place to place are animals. These animals that
carry pathogenic (disease causing) micro-organisms are known as vectors.
Examples of vectors are cockroaches, fleas, mosquitoes, tsetse-flies, black flies, house flies,
bed-bugs, ticks, rats, dogs, cats, etc. Vectors may transmit micro-organisms from place to
place or person to person either mechanically or biologically.
(a) Mechanical Method: The vectors carry pathogens on various parts of their bodies e.g.
legs, wings, mouthparts, hairs, etc. The pathogens do not grow or multiply on the body of the
vectors. Pathogens carried in this way include Salmonellatyphi, Vibrocholerae and
Entamoebahistolytica.
(b) Biological Method: The vector in this case becomes infected with the pathogen when it
feeds on the body fluid of an infected person or animal. The pathogen develops and
multiplies in the body of the vector which then infects a healthy person when it goes to feed.
Thus part of the pathogen’s life cycle takes place in the body of the vector. Examples of such
vectors and the pathogen they carry are;
(i) Anopheles mosquito (female) carries plasmodium (protozoan) that causes malaria.
(ii) Tsetse fly carries Trypanosome (protozoan) which causes sleeping sickness
(Trypanosomiasis).
(iii) Aedes mosquito carries a virus that causes yellow fever / dengue fever.
Tapeworm; an endoparasite
Blood fluke; an endoparasite
Tick; an ectoparasite
Life cycle of human blood fluke
Control of Vectors
Vectors can be controlled by;
(i) Killing the vectors e.g. by spraying with insecticides, use of traps and poisons for rats, etc.
(ii) Use of larvicides to kill larval stages.
(iii) Clearing bushes around houses.
(iv) Destruction of breeding spots e.g. stagnant water should be drained to prevent
mosquitoes from breeding.
(v) Use of drugs to kill the micro-organism in the host.
(vi) Keeping the environment clean etc.
EVALUATION
1. Define the term ‘vector’
2. Enumerate four vectors, the pathogens they carry and the diseases caused by these
pathogens
3. State three ways by which vectors can be controlled
SUB-TOPIC 3:STUDENT’S HEALTH: MAINTENANCE OF GOOD HEALTH
Maintaining the health of students and the people in a community is the responsibility of the
individuals, the community, the government and health organization. Ways of maintaining
good public health include;
1. Proper observance of personal hygiene. Keep yourself and your environment clean.
2. Proper refuse disposal e.g. burning in incinerators, burying in sanitary landfills, etc.
3. Proper sewage disposal e.g. use of pit toilets and water-closet toilets.
4. Protection of water supply by boiling, filtration, addition of chlorine, storage in clean
containers, etc.
5. Protection of food by keeping them in clean containers, boiling or cooking properly
before eating, washing of fruits, vegetables and hands before eating, etc.
6. Health organizations such as United Nations Children’s Education Fund (UNCICEF),
World Health Organization (WHO), International Red Cross Society, etc. help to
maintain the health of people in a country through their corporate activities.
OBJECTIVE TEST
1. Whichof these is not a vector? (a) Black fly (b) Dog (c) Snake (d) House fly
2. Deficiency of proteins the diet of young children will result in a disease called……….
(a) Kwashiorkor (b) marasmus (c) night blindness (d) river blindness
3. Which of these is not one of the uses of bacteria? (a) Production of amino-acids (b)
manufacture of lactic acid (c) Production of vinegar (d) leavening agent
4. The health organization that is saddled with the responsibility of providing for the
emergency needs of children in devastated areas is …..(a) International Red Cross Society (b)
Nigerian Medical association (c) United Nations Children’s Fund {UNICEF} (d) World
Health Organization.
5. A way of providing good health in a community is……….(a) healthy living (b) control of
diseases (c) sewage disposal (d) all of the above
ASSIGNMENT
1. Malaria is one of the most common diseases in the tropics. Explain clearly, how a bite
from a mosquito can cause malaria.
2. Describe the functions of the following health organizations
(a) World Health Organization.
(b) United Nation Children’s Fund (UNICEF)
(c) International Red Cross
3. Read on marine habitat.
WEEK 11------------------------Revision
WEEK 12------------------------Examination