OAK SPRING HILL COLLEGE

SECOND TERM: E-LEARNING NOTE

Session 2023/2024

SUBJECT: BIOLOGY CLASS: SS 1

SCHEME OF WORK
WEEKS TOPIC
1 Irritability

2 -3 Skeletal System

4 Mechanism of support in plants

5 Basic Ecological concept I

6-7 Basic Ecological concept II

8-9 Functioning Ecosystem

10 Energy transformation
WEEK 2-3

TOPIC: TISSUES AND SUPPORTING SYSTEMS

CONTENT:

(a) Introduction
(b) Skeleton and supporting system in animals: (i) Biological significance (importance) (ii) forms
(c) Types of skeletons
(d) Bones of the
SUB-TOPIC 1: INTRODUCTION
What would animals including you look like as well as incapable of doing without the support of
bones and cartilage? Sitting, standing, crawling, walking, swimming, flying, and more, would be
impossible.
Multicellular organisms have some form of rigid support system that give them shape that enable them to
exhibit movement of various degrees as well as withstand forces of wind and water. The framework and
the tissues that support it is known as tissue and supporting system.

Sub-topic 1: SKELETON AND SUPPORTING SYSTEM IN ANIMALS.

Skeleton is the framework which gives support and shape to an animal. This supporting framework can
be on the inside of the organism: in higher animals such as reptiles, birds and mammals, the organisms
have a skeleton which form the central core of the body. It is covered by muscles, blood vessels, nerves
and skin.
In man the various structures such as tendons, ligaments, interstitial tissues and bones make up
the skeletal and supporting system in animals.
BIOLOGICAL SIGNIFICANCE OF SKELETON
Most living organisms whether they are plants or animals, posses a form of rigid frame work called
skeleton. Skeleton consists of various tissue and supporting systems in both plants and animals. Skeleton
is biologically significant in the life of living organisms. Without skeleton, soft tissues will not have
adequate support, protection and shape. Their bodies will collapse and animals may not be able to move
parts or all of their bodies. Body movement in a complex animal is brought about by muscles which work
by pulling on some kind of support. This support is the rigid framework – skeleton- in animals to affect
work and movement. Aquatic multicellular animals need a supporting system to succeed in their hunt for
food. As a result, most complex animals have evolved supporting structures or skeletons which provide
support against gravity, but the skeletons are flexible enough to allow movement.
EVALUATION
 What is Skeleton?
 State three biological significance of skeleton in the life of living organisms.

FORMS OF SKELETON
There are three basic forms of animal skeleton: chitin, cartilage and bone. These are the main types of
materials found in the skeleton of animals.
Exoskeleton of a Goliath Beetle
CHITIN
Chitin is a tough light and flexible material that is a major component of the skeletons of arthropods. It is
a non-living substance and incapable of growth. It consists of cellulose-like carbohydrate and some
deposits of proteins and minerals. Animals with chitinous skeleton can only grow by moulting because
the exoskeleton restricts the growth and size of the organism. The skeleton of insects is composed of
chitin and a thin, waterproof layer of wax.

Arthroscopic Knee Surgery

CARTILAGE
This tissue is found in the skeletons of complex vertebrates. It consists of living cells (chondroblasts) and
carbohydrate and protein fibres. It is a tough and flexible tissue that has great tensile strength. It acts as a
shock absorber, cushioning the effect of bones moving against bones when we move.
Cartilage does not have its own blood supply but depends on the oxygen and nutrients that diffuse across
it from nearby tissues. It is usually found inside animals and can be replaced by bones as in young
embryos. It is the skeletal material found as endoskeleton of cartilaginous fish such as rays and sharks,
in human babies and in several part of adults (but in very small portions) e.g. Pinna, tip of the nose and
end of long bones.
Cartilage occurs in three forms in mammals: elastic, fibro and hyaline cartilage.
- Elastic cartilage is present in the external ear and epiglottis. It also supports the Eustachian tube
and the external ear canal.
- Fibro cartilage is tougher than hyaline cartilage and is found in the discs between the small
bones (vertebra) of the vertebral column.
 - Hyaline cartilage makes up the rings which support the trachea and bronchi and keep them open.
It covers the surfaces of movable joints and also supports the protruding part of the nose.

Joint Damage Caused by Arthritis

BONE
Bone is the main skeletal structure found in vertebrates. It consists of living bone cells (osteocytes),
protein fibres (collagen) and minerals, mainly calcium phosphate and calcium carbonate. The minerals,
are mainly calcium phosphate and calcium carbonate. Minerals are non-living matter and make up two-
thirds of the mass of a bone. As a result, bone is a stronger and more rigid tissue than cartilage. Bones
have their own blood supply to nourish them.
In a young vertebrate embryo, the skeleton is made up of cartilage. As the embryo grows, bone cells
replace cartilage cells. This causes the cartilage tissue to harden into bone through the addition of
minerals. This process is known as ossification.
The long bones such as humerus, femur, and tibia, consist of a hard outer layer called shaft and a spongy
and hallow cavity filled with bone marrow. The middle part, in the hollow is occupied by the yellow
marrow and it consists of fat cells. Red marrow fills the spongy spaces in the two ends. A layer of hyaline
cartilage covers their articulating surfaces. The numerous tiny openings in the bones allow circulation of
blood and sensitivity.
Differences between a bone and a cartilage
Bone Cartilage
Made up of living cells surrounded by made up mainly of living cells.
non-living cells
Made up mainly of minerals Not made up of minerals.
Made up of a hard substance Made up of soft substances
Inflexible particularly in adults Very flexibe or elastic
Never replaced by cartilage Can be replaced by bone

TYPES OF SKELETON
Skeletal tissue differs as observed in invertebrates and vertebrates. The types are as follows:
 1. Hydrostatic skeleton: this is the simplest type of skeleton. It depends on turgor pressure of its
body fluid.
A typical example of an organism with this type of skeleton is Earthworm. The muscle in the
body wall works against its fluid. The walls of each of the body segment have two sets of
muscles. One set is longitudinal, while the other is circular. By contracting and relaxing
antagonistically, movement is affected in the organism and a form of shape is affected.

Earthworm
2 Exoskeleton: anthropods like these, spiders, insects, have hard cuticle of chitin and some hardening
m. ineral salt like phosphates and carbonates of calcium. The outermost layer is of this cuticle is
usually covered with a thin layer of wax that keeps the organism waterproof. This outer head
covering is the skeleton is outside the visceral of the organism, it is known as an exoskeleton. Shells
of molluses of snail are also Exoskeletons.
3. Endoskeleton: this term describes the skeleton of higher animals i.e. vertebrates such as Man, birds etc.
This skeleton is inside the body of the animal and it is covered by tissues and muscles. This type of
skeleton is made up of bones and cartilage. The muscles are attached to the skeleton by tendons.
Questions
What are vertebrates?
Differentiate between Endoskeleton and Exoskeleton

VERTEBRATE SKELETONS
The skeletons of vertebrates are made up of bones and cartilage. They are Endoskeleton. All the bones
are joined together to allow movement. Vertebrate skeleton has a central spinal column. This column is a
flexible stack of bones called vertebrae. All vertebrates’ skeletons are built on the same plan. The
vertebrate skeleton is divisible into two parts.
(a) Axial skeleton: it consists of the skull, spinal column (vertebrae) and Ribs.
(b) Appendicular skeleton: this consists of the limbs (fore-limbs-hands and hind limbs-legs) in Man,
Shoulder (Pectoral girdles) Hip bone (Pelvic girdle).

SUGGESTED PRACTICAL:
1. Illustrate skeletal support using clay and plasticine.
2. Practical examination of samples of: Arthropods such as spider, cockroach, millipede.
3. Examine an intact mammalian skeleton. Identify and name the main parts of the skeleton.
4. Students to draw and label the fore-limb.

AXIAL SKELETON
HUMAN SKULL: The human Head consists of several flat bones which form the skull. The skull is
hollow and houses and protect the soft tissues of the brain. The upper and lower jaws are also part of the
human skull. The jaws contain the teeth. The skull also have socket and cavities which contains and
protect the delicate sense organs the like the eyes and ears.
Diagram of the adult human skull (side view)
The skull is the topmost part of the body. It pivots on the top of the backbone on the first two vertebrae
called atlas and axis respectively.

STARNUM AND RIBS:

The sternum and twelve pairs of ribs form the Rib Cage. The ribs articulate with thoracic vertebrae at the
back, curve to the front and get attached to the sternum by the means of elastic cartilage. First ten pairs
of ribs are attached to the sternum. The other two pairs are not attached and are referred to as floating
ribs. The rib cage houses and protects vital organs such as the heart, lungs and other contents of the
thorax as well as help in breathing.
VERTEBRAL COLUMN: (BACK BONE)
The vertebral column is made up of 33 bones. These bones of the column are built on the same plan. All
33 small irregular bones are joined to form a strong fairly flexible S - shaped rod in the middle of the
body. Each vertebra has a hole through which the spinal cord pass from the skull to the coccyx hence it
is called Vertebral Column .
Atlas: The first vertebrae of the column is called atlas
Diagram of atlas vertebrae
Atlas and Axis
The second vertebra of the column is called Axis. Axis has a projection called Ondotoid process. It
projects upward into a space in the Axis. This peg-like projection allows pivoting and rotation
movements of the skull.
Diagram of Axis Vertebrae
The 33 bones are divisible into five sections:
Cervical vertebrae 7 - Neck
Thoracic vertebrae 12 - chest
Lumbar vertebrae 5 - waist area
Sacral vertebrae 4 - fused bones
Cervical vertebrae are 7 in number. They are the bones of the neck region, the first two of which are the
Atlas and Axis which are structurally different from the remaining 5.
Diagram of a Typical Cervical
Lumber vertebra: these are 7 in number. They are lower back and carry most of the weight of the body.
They have a large centrum.
Diagram of Lumber vertebra
Sacra vertebra: these are 5 bones fused together. Together, they are called sacrum. They connect the
pelvic girdle to the backbone.
Coccyx: they are the bones of the tail. They are 4 small fused bones which ends the vertebral column.
Function of the vertebral Column
It supplies the thorax and the abdomen.
It houses and protects the spinal cord.
Vertebra all have holes through which spinal nerves pass to all parts of the body.
Intervertebral discs located between vertebrae permits smooth movement between the vertebrae well as
absorb shocks of landing as the animal moves.
JOINTS
A joint is a place where two separate bones meet in order to effect different movements which is one of
the functions of the skeletal system. Joints are held in place by tough ligaments.
Parts of Joint
A typical joint has two separate bones. Each ends with a “cap-like” layer of cartilage and synovial fluid
encased in a capsule. The cartilage and fluid keeps the friction-free.
Movable Joints
Types of Joints
There are two main types of joints
1. Immovable: fixed joint as in the cranium.
2. Movable: they do not permit movement of bones in the /skull cranium. On the basis of the
function of the joint or degree of movement possible, movable joints include:
(i) Hinged joints: found at the knees, elbows and fingers. This type of joint allows movement in
one plane.
(ii) Gliding Joints: found at the wrist and ankles. The bones glide over each other, permitting
movements in several planes. This movement permits fine dexterity movements such as
writing, knitting, moulding etc.
(iii) Ball and socket Joint: this is located at the shoulder and hip. Movement at this joint is in many
places.

FUNCTIONS OF SKELETON IN ANIMALS

1. It gives the animal shape.
2. It supports and protects soft tissues and organs e.g. brain, heart; the weight of the body e.g.
lumbar vertebrae.
3. It brings about movement. It provides surfaces for attachment of muscles which pull on the bones
by contracting and relaxing to effect mouth.
4. Red blood cells are produced in the marrow of long bones of the skeleton.
5. It also stores mineral salts.
 6.

Pelvis
The human pelvis consists of the hipbone on the sides and front, and the sacrum and coccyx
behind. The pelvis supports the spinal column and rests on the lower limbs.
PECTORAL AND PELVIC GIRDLES
Pectoral girdle: in humans the pectoral girdle holds the upper limbs or arms to the axial skeleton. It
consists mainly of four separate bones: two large flat triangular shoulder blades or scapulae are attached
to the vertebral column by muscles. Each scapula has a depression called glenoid cavity into which the
head of the upper arm bone or humerus fits to form the shoulder joint. The clavicles are attached to a
scapula at one end and to the sternum at the other end. The pectoral girdle is not rigid. It enables the arm
and shoulders to fairly freely.
Pelvic Girdle: in humans, the pelvic girdle or hips consists of two bones, the right and left pelvis. These
are joined to the sacrum at the back and held together by fibro cartilage at the back and held together by
fibro cartilage at the facets in front, to form a complete, rigid girdle. On the outer edge of the pelvis is a
deep cavity, the acetabulum, into which the head of the thigh bone or femur fits to form the hip joint. The
pelvic girdle is designed to receive the weight of the upper body and persists on to the legs (if you are
standing), or to the surface on which you are sitting. The rigid structure of the girdle restricts the
movements of the hips and legs.
FORE AND HIND LIMB
The fore and hind limbs of all terrestrial vertebrates are built on a basic penladactly plan. It consists of a
long bone, followed by a pair of long bone placed side by side, a set of nine small bones in three rows,
five thin long bones and finally five digits.
Forelimb consists of the following:
 Humerus which has a rounded head for articulation with the glenoid cavity of the scapula;
 Radius and ulna lie side by side as the long bones of the forearm, they articulate with the deeply
grooved lower end of the humerus.
 Carpals are the nine small irregular bones of the wrist that are arranged in three rows.
 Metacarpals are the fire finger bones and
 Digits are the five long tiny bones that are made up of small bones called phalanges.
The hind limb consists of the following:
 Femur has a round head which fits into the acebulum of the pelvic girdle. It is the longest bone in
the body.
 Tibia and fibula, the latter is smaller than the former.
 Fibula, a small bone which is joined to the tibia at its distal end;
 Patella or kneel cap is a small round bone in front of the knee joint.
 Tarsals are the ankle bones.
 Metatarsals are the foot bones.
 Digits are the toes.

EVALUATION
 Name two bones of the pectoral girdle.
 Name three bones each of the (a) fore-limb (b) hind limb.
 Define a joint. Give two examples each of (a) hinge joint (b) ball and socket joint.

WEEK 4

TOPIC: MECHANISM OF SUPPORT IN PLANT

CONTENT (a) Different types of supporting tissues (b) Functions of supporting tissues in plants.
Types of supporting tissues
Plants have various types of supporting tissues that make them up. Like animals, these tissues help them
to stand some meters above the ground without falling. They have definite shape, strength, rigidity and to
resists external force like wind and water.
Tissues that give support to plant are simple, having one type of cell. This includes, parenchyma,
collenchymas, sclerenchyma, and complex tissue i.e. with two or more types of cells e.g., xylem, phloem,
and epidermis.
PARENCHYMA
These are the first cells formed from the meristerm. Other tissues are derived from parenchyma. They
possess thin wall and are found in the cortex of stems, leaf mesophylls, and flesh of fruits.

COLLENCHYMA
Collenchymas cells are found beneath the epidermis in stems and petioles and around the veins in dicot
leaves. Collenchymas have flexible cell walls that allow elongation of plants. It gives rigidity, hardness,
and support to the plant.
SCLERENCHYMA
This is made up of cells impregnated with lignin that gives the plant hardness, rigidity and mechanical
support. It has thick secondary walls. Cells occurs in fibre cells and stone cells.
XYLEM OR WOOD
It is the tissue that conducts water and mineral from the soil to the plant and vessels. Xylem has other
supporting tissues in form of fibres of fibre and wood parenchyma.
PHLEOM
This is the thin walled and lies externally in each vascular bundle. It has three types of cells; sieves,
companion cells and phloem parenchyma.
CORTEX: It surrounds the vascular bundles. Cortex is a tissue of parenchyma cells.

EPIDERMIS
This is the outer most layers of cells of plants. It forms the protective skin of the stem, leaves, flowers
and fruits. It is made up of single layer of cells. It secrets waxy substances known as cutin, that forms
layer of cuticle which prevents excess water loss and mechanical damage to plants.
Nectarine Tree
FUNCTION OF SUPPORTING TISSUES IN PLANT
1. It gives definite shape to the plant.

Epidermis, the outmost skin determines the structure of the plant and how it
looks.
2. Strength: Collenchyma cells, sclerenchyma cells , xylem vessles and turgid
parenchyma cells have been identified as tissues that strengthen the plants; walls
are thickened to provide strength to plant.

3. Rigidity ;

Supporting tissues gives rigidity that plant needs to withstand blows from
outside.
4. Resilience and Flexibility

By the help of supporting tissues, plant sway in the direction of the wind,
breezes, and water without being moved.
EVALUATION
1. List four plant tissues and discuss any one of your choice.

2. Mention three cells of the phloem tissue

3. State three functions supporting tissues in plants.

GENERAL EVALUATION
1. One of these is not a plant tissue (a) Bark (b) Collenchyma (c) Parenchyma (d ) phloem (e)
sclerenchyma.

2. The first cells formed from the meristem are called (a) Xylem (b) Cortex (c) Epidermis (d)
Collenchyma (e) Parenchyma.

3. One of these forms the protective skin of the stem (a) Wood (b) Epidermis (c) Phloem (d) Cortex
(e) Cambium layer.

ESSAY TEST
Write short note to explain the following:
a. Xylem or Wood.

b. Sclerenchyma.

c. Parenchyma.

d. Collenchyma.

WEEKEND ASSIGNMENT
1. Sketch an annotated diagram of the cross section of the stem.

2. Mention five other parts of plants apart from the supporting tissue.

WEEK 5

TOPIC: BASIC ECOLOGICAL CONCEPTS I

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.

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:
Aquatic habitats e.g. puddles, streams, ponds, seas, oceans.
Terrestrial habitats e.g. savanna, rain, forest, desert, etc.
Arboreal habitat i.e. tree tops and tree trunks.
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.

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.

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.

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.

Ecosystem: This is self – supporting unit that is made up of a living part and a non-living 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;
Food producer’s e.g. autotrophs (green plants), chemosynthetic bacteria and protophyta.
Food consumer’s i.e. heterotrophs such as animals, protozoa and some bacteria.
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.
(c) other factors like air, water, storms, etc.

Characteristics of An Ecosystem
The characteristics which make an ecosystem a functional unit/a self–supporting unit are
(i) a flow of energy
(ii) a 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. Theenergy and nutrients in the food is passed on to
heterotrophs (consumers) suchas animals which feed on plants or on one another. The animals and plants
eventually die and decomposers feed on them thereby obtaining their ownenergy. However in the
process, the decomposers release the nutrients in theanimals and plants back into the abiotic environment
(i.e. the soil). Thesenutrients can be re-used again by the food producer’s. Plants also give outoxygen
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

WEEKEND ASSIGNMENT
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

ESSAY QUESTIONS
Make a drawing of the map of Nigeria and outline the local biomes

WEEK 6-7
TOPIC: BASIC ECOLOGICAL CONCEPTS II
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 temperatureis 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;
-Choose the habitat to be studied
-Choose a sampling method
-Identify the species in the habitat
-Collect, count and record the different types of organisms present.
-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 quadrates 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; Individuals do not move out of or into the ecosystem
The marked individuals are randomly distributed in the population.
The marked individuals are a random sample.
The initial capture and markings do not influence recapture.
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.

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. 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. 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) 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 ms¹‫)־‬.

(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 water-speed 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.

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 8-9

TOPIC: FUNCTIONAL ECOSYSTEM

CONTENT:
1. (a) Autotrophy and Heterotrophy (i) Producers (ii) Consumers (iii) Aquatic
and Terrestrial.
2. Food Chain, Food web and Tropic level.

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: Autotrophs and Heterotrophs.
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.
Now, under the consumers we have the following:
1. Primary consumers, e.g. grasshopper, rat etc.
2. Secondary consumers, e.g. cat, lizard etc.
3. Tertiary consumer, e.g. hawks, snakes.
4. 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

EVALUATION
1. Define the term ecosystem.
2. List the two major parts of the ecological system

GENERAL EVALUATION
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.

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.
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.
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.
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.
(DIAGRAM OF FOOD WEB)

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.
Food Pyramid
Food pyramid is a representation of food chain in the food producers from the base and carnivores from
the apex.

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.
Pyramid Of Biomass: The pyramid of Biomass (or standing crop) indicates, by weight, the total mass of
individuals or organisms at each trophic levels.
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.

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.
ESSAY TEST
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.
WEEKEND ASSIGNMENT
Sketch the diagrams of the pyramid of numbers, pyramid of biomass in a grassland, and pyramid of
energy.

WEEK 10

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.
Heat Loss from a House
A thermograph shows the large amount of heat lost through a house’s windows during winter. Replacing
conventional windows with double- or triple-paned windows cuts down the amount of heat that can
escape from the house; this conserves energy and reduces heating bills.
Energy Flow
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%

ESSAY QUESTIONS
1. Use the laws of thermodynamics to explain food chain.
2. How does the second law apply to energy flow.

WEEKEND ASSIGNMENT
1. Explain what happens when heat is lost in a food chain.

WEEKEND ACTIVITIES
Explain various ways through which energy flow from the producer to you.