CLASSIFICATION OF LIVING THINGS
Classification is the sorting of organisms into different groups
based on their shared / similar features which distinguish them
from other groups. Biologists have examined and described more
than 1.8 million kinds of living organisms. There are still many
more to be discovered. Classification enables Biologists to;
1. Identify organisms.
2. Distinguish one organism from another.
3. Understand the diversity of life.
The general principle of classification is called Taxonomy or
systematic.
Aristotle (384-322 BC) a Greek philosopher was the first to make
an attempt to classify living organisms. The present classification
was proposed by Carolus Linnaeus (1707-1778), a Swedish
naturalist. His work brought about the binomial system of
nomenclature.
Hierarchy Of Classification
Kingdom
Phylum/Division
Class
Order
Family
Genus
Species
Sometimes, intermediate levels like sub and super are added. E g sub-phylum
and super-class. The largest hierarchy is the kingdom which embraces other
groups while Species is the smallest and the last link of classification.
Organisms at the species level can interbreed together to produce fertile offsprings of their kind.
The system of giving two names to an living organism which is
generally recognized by biologists world wide is called Binomial
nomenclature.
•The first name is the genus or generic name which always
start with a capital letter.
•The second name is the species or specific name which
always start with a small letter.
•They are written in italic form if typed or underlined separately if
handwritten.
Examples; Orange- Citrus sinensis
Dog- Canis domestica
Rat- Rattus rattus
Classification of maize plant
Classification
Name
Characteristics
Kingdom
Plantae
All Plants
Division
Tracheophyta
Vascular plants( having vessel for water and food conduction)
Superclass
Spermatophyta
Seed-producing plants
Class
Angiospermae
Flowering plant
Subclass
Monocotyledoneae
Flowering plant
Order
Graminales
Grasses, leaves with shealthing leaf bases
Family
Graminacae
Cereals, millets, bamboo, grasses
Genus
Zea
Maize plants, female inflorescent develops into cob
Species
mays
Cultivated maize plant
Classification of African elephant
Classification
Name
Characteristics
Kingdom
Animalia
All Animals
Phylum
Chordata
Animals with notochord
Subphylum
Vertebrata
Animals with backbone
Class
Mammalia
Animals with hair
Order
Proboscidea
Large animal with long
flexible trunk
Family
Elephantidae
Elephant found in Asia and
Africa
Genus
Loxodonta
Elephant found in Africa
with long trunk, large ears
and two finger-like lips
Species
Africana
African elephant
Classification of Human being
Classification
Name
Characteristics
Kingdom
Animalia
All Animals
Phylum
Chordata
Animals with
notochord
Subphylum
Vertebrata
Animal with
backbone
Class
Mammalia
Animal with
fur
Order
Primate
Mammals with
grasping
hands and feet
Family
Hominidae Ape-man,
primitve man
and modern
man
Genus
Homo
Primitive man
and Modern
man
Species
Sapiens
Modern man
Kingdom
Linaeus placed all living organisms into two kingdoms; Plants
and Animals. Recently, scientists have added other
kingdoms. The five kingdoms include:
i. The kingdom Monera
ii. Kingdom Protista / Protoctista
iii. Kingdom Fungi
iv. Kingdom Plantae
v. Kingdom Animalia
KingdomThe monerans are the single-celled motile or non-motile organisms. Organisms
are microscopic with procaryotic cells ( cell that lacks membrane-bound
organelles). Examples are the bacteria, nostoc and oscillatoria.
Bacteria are found everywhere: air,
water, soil and inside living organisms.
While others can produce food
themselves (Chemosynthesis), others
can decompose organic substance
(Saprophtes). Some bacteria can live in
their host and cause diseases
(Parasites).
Cyano-bacteria(Blue-green algae) are
found mainly in fresh water and in
damp places. They contain chlorophyll
not contained in chloroplast and are
regarded as the smallest plant.
(Structure of Bacterium
Draw)
Kingdom- Protista/ Protoctista
Protists are single-celled or unicellular
organisms. They are made up
eucaryotic cells (Cell with membranebound organelles)
1. Phylum Protophyta: These protists
are plant-like.They have cellulose cell
wall and organelles called chloroplast
which contains chlorophyll which help
them to make their food. Examples
Includes Chlamydomonas, Chlorella,
Diatom etc
ii. Phylum Protozoa: These protists
are animal-like. They feed on
ready-made food and have no
cellulose cell wall. Examples are
Amoeba, Paramecium ,
Plasmodium, Chlamydia etc.
Euglena viridis is a protist that shows both
plant-like and animal-like features
Structure of Chlamydomonas
Structure of Paramecium
Draw)
Draw)
Kingdom- Fungi
Fungi are multicellular organisms. They
are eucaryotes.
• General characteristics of fungi
i. They lack chloroplast in their cells
hence can’t carryout photosynthesis.
ii. They possess cell wall made of
chitin.
iii. They are non-motile except for slime
mould
iv. They are made up of branching
thread-like structure called hyphae.
v. Reproduction is sexual(Conjugation)
and asexual(spore formation).
vi. Feeding is saprophytic
(decomposition) and parasitic.
Rhizopus
(Draw)
Economic importance of Fungi
They cause food spoilage eg mould or
Rhizopus
ii. They cause diseases both in plant and
animals eg yam rust and candidacies in
female
iii. They are decomposer hence they improve
soil fertility and recycle inorganic material on
earth
iv. They are used in food industry to carryout
fermentation eg yeast
v. They are used in pharmaceutical industry for
the production of penicillin eg penicillum
notatum
vi. Some mushrooms are edible and serve as
food.
Examples of fungi are Rhizopus, Toadstood,
Penicillum, Aspergillus, Yeast, Mushrooms,
Slime mould.
Mushroom.
i.
Yeast.
Kingdom Plantae
All green plants belong to this kingdom.
General characteristics
i. Presence of chloroplast which contains chlorophyll for making it food.
ii.Presence of cellulose cell wall.
iii.They have eucaryotic cells’
iv.They are non-motile
3 Divisions of plants are known. These are;
1. Thallophyta
2. Bryophyta
3. Tracheophyta
 Thallophyta
1. They are simple microscopic plants
2. Some are unicellular eg
Chlamydomonas while others are
multicellular eg spirogyra
3. Algae are maily autotrophic plants
4. They lack stem root and leaves
Examples of simple aquatic plants like
algae.
Types of algae
i. Brown algae(Phacophyta) eg
Sargassium, They have chlorophyll
(Fucoxanthin)
ii. Green algae( Chlorophyta) eg Volvox,
spirogyra, diatom.
iii. Red algae (Rhodophyta) chlorophyll
iv. Golden yellow algae (Xanthophyta) e g
Tribonera.
Structure of Spirogyra (Draw
 Bryophyta
i. They are non-vascular plants(lacks
xylem and phloem)
ii. They grow in damp places
iii. They show alternation of generation;
sporophytic generation and
gametophytic generation.
iv. They possess chlorophyll and can
carryout photosynthesis
v. They are non-flowering plants
vi. Water is essential for their fertilisation
vii.Presence of false stem, roots and
leaves
Examples are moss and liverwort.
Tracheophyta
i. They are vascular plants ( conductiing vessel i e xylem and phloem)
ii. They have true roots, stems and leaves
iii. Presence of chlorophyll for photosynthesis
iv. Stores cellulose in their cell walls
Subdivision of Tracheophyta are;
a. Pteridophyta
b. Spermatophyta
Subdivision: Pteridophyta
i. They are multicellular and vascular green plants
ii. They are non-flowering plants
iii. They have true roots, stem and leaves
iv. They are non-seed producing plants
v. They show alternation of generation I e sporophytic (Spore-forming) and
gametophytic generation ( Gamete-producing).
Spermatophyta:
i. They are multicellular seed-producing flowering plants
ii. They are vascular plants with well developed vascular
tissues
iii. They have true root, stems and leaves
iv. Reproduction is sexual and water is not required for
reproduction
Spermatophyta are divided into two:
i. Gymnospermeae
ii. Angiospermeae
Structure of cone with naked seed
Gymnospermeae:
i. These are plants with Ved-seed.
ii. They do not bear flowers.
iii. They have true roots, stem and leaves.
iv. Seeds are borne on special structure called cone.
v. They are vascular green plants.
Examples are conifers and pines.
b
Angiospermeae:
i. They are the most complex green flowering plants
ii. They are vascular plants i.e presence of xylem and phloem
iii. They have well developed and complete flowers
iv. They are seed-producing plants with their seeds enclosed in fruits
v. They are terrestrial plants
There classes are;
i. Class: Dicotyledoneacea (Dicotyledonous)
ii. Class: Monocotyledoneacea (Monocotyledonous)
Class : Dicotyledoneacea)
i. They bear seeds with two-seed leaves or cotyledons
ii. Vascular bundle of their stem, root and leaves are arranged in a regular
pattern
iii. Their floral parts eg sepal, petals, carpel, and stamen exist in the groups of
four to five
iv. Their leaves have net venation
v. They have tap root system
Examples of dicot plants are Mangoes, beans, pawpaw, groundnut, peas etc
Monocotyledoneacea ( Monocot plant)
i. They bear seeds with one cotyledon
ii. the vascular bundles of the stem are scattered
iii. They have parallel venation in their leaves
iv. They have fibrous root system
v. Their floral parts exist in the group of three or
multiple of three
Examples are Maize, Grasses, Rice plant, coconut, etc
Kingdom: Animalia
All animals belong to this kingdom
i.
They are multicellular organisms.
ii. Feeding is heterotrophic or holozoic.
iii. They cells lack cell wall and chloroplast.
Classification of Animals based on some important Features. Animals are
classified based on
i.
Body symmetry
ii. Body cavity
iii. Body design
Also, animals are divided into two groups namely
-Invertebrata
-Vertebrata-
INVERTEBRATA
• Super Phylum Invertebrata has the following phyla:
i. Phylum Porifera
ii. Phylum Coelenterata/ Cnidaria
iii. Phylum Platyhelminthes
iv. Phylum Nematoda
v. Phylum Annelida
vi. Phylum Mollusca
vii. Phylum Arthropoda
viii. Phylum Echinodermata
Phylum:
Porifera
i. They are simple aquatic organisms.
ii. They do not move about but are attached to rocks and shells.
iii. They live in colony and their larva stage is motile
iv. They have assymetrical body e g spongy.
Vase-like
body
Openings
Phylum: Coelenterata( Cnidaria)
i. They are multicellular organisms
ii. The body is made up of two layers ie
ectoderm and endoderm
iii. They are mainly aquatic organisms
iv. Their bodies are radially symmetrical
v. They have soft jelly-like bodies
vi. They have tentacles and stinging cells
Examples are Jelly fish, Sea anemone, Coral,
Hydra
Phylum: Platyhelminthes
i. They are multicellular flat worms
ii. They are bilaterally symmetrical
iii. They don’t have body cavity or lumen
iv. The body is made up of 3 germ cells: the
ectoderm, mesoderm and endoderm
v. They are mostly parasitic in man than in
animals
Vi. They are hermaphrodites
Examples include Tapeworm, Planaria,
Liver fluke, Blood fluke.
Phylum: Nematoda
i. They have round and cylindrical body.
ii. They lack body cavity ie they have pseudocoelom body cavity
iii. They are bilaterally symmetrical
iv. Their body is made up of 3 germ cells.
v. Some are hermaphrodite
Examples are round worm, hookworm, guinea worm, filarial worm,
threadworm etc.
Phylum: Annelida
i. They have internal and external segmented bodies.
ii. The body is long and cylindrical.
iii. They have true body cavity/coelomate bodies.
iv. Some are aquatic while others are terrestrials .
v. Alimentary canal has two openings: the mouth and the anus.
vi. They are hermaphrodites.
vii.Examples are earthworm, leeches, tubeworm
Phylum: Mollusca
i.
They have soft unsegmented bodies
ii. They have tentacles in their head
iii. They have muscular foot adapted for crawling or
burrowing
iv. The body is covered by a soft tissue called
mantle
v. Some have calcerous shells eg snail, while
others have no shell eg octopus
vi. Their eyes and tentacles are used for
sensitivity.
Examples are Squid, periwinkles, snails, oysters,
octopus, slug.
Phylum: Arthropoda
i. They have segmented bodies
ii. They have hard rigid exoskeleton made of chitin
iii. They have jointed appendages or jointed legs used for feeding,
movement, reproduction or sensory organs
iv. They exhibit moulting or ecdysis ie they shed their skeleton
v. Their bodies are divided into two or three segments such as
head, thorax and abdomen
vi. They are triploblastic ie 3 body layers
vii. They are billaterally symmetrical
viii.They have various means of respiration e g gills, trachea,
lungbook or body surface
Classes of Arthropods
i. Class Crustacea e g crab,
crayfish, shrimp, prawn,
lobsters
ii. Class: Insecta eg
Grasshopper, Cockroach,
housefly, butterfly
iii. Myriapoda eg Centripedes
and Millipedes
iv. Arachnida: eg Spider,
scorpion, mites, ticks
S/N
Features
Crustacea
Insecta
Arachnida
Myriapoda
1.
Body division
Two body
divisions
,Cephalothorax
and abdomen
Three body
divisions ie
head, thorax
and abdomen
Two body
divisions ie
Prosoma and
Opisthosoma
Two body
divisions
2.
Wings
Absent
Present
Absent
Absent
3.
Eyes
A pair of stalked
eyes
A pair of
compound
eyes
Eight simple
eyes
Simple eyes
4.
Antenna
Two pairs of
antennae
A pair of
antennae
None
A pair
5.
Walking leg
Five pairs of
jointed legs
Three pairs of
jointed legs
Four pairs of
jointed legs
2 pairs in each
segment
6.
Respiratory
organ
Gills
Trachea
(Spiracle)
Lung books
Trachea
(Spiracle)
Phylum: Echinodermata
i. They are mainly marine animals
ii. Echinoderms have spiny skin.
iii. Their bodies are radially symmetrical
iv. They are triploblastic animals i e they have three body layers.
v. They have neither head nor brain and no segment
vi. It has tube feet which is used for movement.
Examples are Starfish, Sea urchins, sea cucumbers and brittle
stars etc.
Phylum : Chordata
Subphylum: Vertebrata
The vertebrate are organisms with backbones. They are grouped
into 5 classes. These are:
i. Class Pisces eg fishes.
ii. Class Amphibia eg toad, frog.
iii. Class Reptilia eg lizard.
iv. Class Aves eg birds.
v. Class Mammalia eg sheep
Class PISCES
They are aquatic animals i e they can be found in marine, fresh
water, pond, lakes, rivers.
i. Their skin are covered by scales but few are without scales.
ii. They have fins which are used for movement in water.
iii. They are poikilotherms or cold-blooded animals.
iv. They have gills which are used for gaseous exchange.
v. They have lateral line system which is used for detection of
vibration and pressure in water.
vi. They have swim-bladder which enables them to maintain
buoyancy in water.
vii.Reproduction is sexual and they have external type of
fertilization
viii.They are oviparous animals I e they lay eggs in the
environment outside their body. No parental care.
Examples are Tilapia, Shark, Markerel, Salmon etc.
Class: AMPHIBIA
i. They are poikilothermic or cold-blooded
animals.
ii.They have two pairs of limbs-fore limbs and
hind limbs.
iii.They have naked or moist and glandular skin
with no external scales.
iv.They carry out gaseous exchange using gills,
lungs, skin and mouth.
v.Presence of poison glands on their skin for
defense.
vi.They have 3-chambered heart.
vii.They have sticky tongue which is protruded
and retracted quickly to capture prey.
Examples are frogs, Salamander, newt and
Toad.
Class: REPTILIA
i. They are poikilothermic or cold-blooded animals.
ii. They have dry skin covered with scales.
iii. They have 2 pairs of limbs except snakes.
iv. They have lungs for gaseous exchange.
v. Reproduction is sexual and fertilization is internal.
vi. They have an incomplete developed 4-chambered
heart.
vii.They have oviparous mode of reproduction.
viii.They have homodont dentition.
Examples are lizard, wall gecko, tortoise, snakes,
crocodiles, chameleon, turtle etc
Class: AVES
i. They are homoiothermic or warm blooded animals.
ii. Entire bodies are covered with feathers except the
hind legs which are covered with scales.
iii. They have two pairs of limbs.
iv. They have wings that are used for flight.
v. They have beak without teeth that are used for
feeding.
vi. Presence of rigid and hollow bones with air sacs for
lightness in air.
vii.Exhibit oviparous mode of reproduction.
Examples: Pigeons,domestic fowl, ducks, ostrich, hawks,
sparrows
Class: MAMMALIA
i. They are homoiothermic or warm-blooded animals.
ii. Their bodies are covered with hairs.
iii. They have heterodont dentition.
iv. They have lungs for gaseous exchange
v. They have two pairs of limbs
vi. The skin contains glands like sweat gland and mammary gland
vii. Reproduction is sexual and fertiliZation is internal.
viii. Mode of reproduction is viviparous
ix. Presence of 4-chambered heart
x. Bilaterally symmetrical body
Examples are
a. Protheria- The monotremes and egg-laying mammals eg Platypus.
b. Metatheria- Pouched mammals or Marsupials(without placenta) e g
Kangaroo.
c. Eutheria- Placenta mammals eg man, horse and lion.
Viruses
A virus is extremely small and can only be seen
through an electron microscope. It does not fit into
any of the kingdoms known as it does not have a
cell structure but made up of a coiled strand of
nucleic acid (RNA or DNA) enclosed within a
protein coat.
Virus as a Living thing
i. Virus can reproduce(replicate)
ii. Its nucleic acid can be transmitted.

Virus as a non-living thing
i. Virus forms crystals outside their host cells.
ii.Virus can’t respire, feed, excrete, respond to
stimuli etc.
Dichotomous key
A dichotomous key is a series of choices statements
and clues that lead to the correct name of a given
organism; that allows the user to determine the
identity of organism such as trees, mammals,
reptiles, and fish. Dichotomous means "divided into
two parts" therefore, dichotomous keys always give
two choices in each step.
Examples are
Class Activity
THE CHEMICALS OF
LIFE
OBJECTIVES OF LESSON
By the end of the lesson, the students should be
able to;
1. list the various chemicals in organisms.
2. mention the elements that make up each.
3. state the types of carbohydrate and examples
4. mention at least 3 functions of each chemical.
Cells in the body of living organisms need chemical substances
inside them to make new cytoplasm and produce energy. Most
of these chemical substances are gotten from the food we eat
and they include water, lipids, salts, carbohydrate, proteins,
vitamins and their derivatives. Each of these are vital for their life
processes.
CARBOHYDRATES
Contain three kinds of atom which are
Carbon (C), Hydrogen (H), and Oxygen (O)
in 1:2:1. Carbohydrate can be classified into:
1. Monosaccharides: These are the
simplest kind of carbohydrates (C6H12O6).
Glucose, Fructose, galactose, ribose are
simple sugar. Although they contain many
atoms, simple sugar molecules are very
small, soluble in water and taste sweet.
2. Disaccharides are larger molecules formed if two simple
sugar join together. It is a more complex sugar and
examples include Sucrose (in sugarcane) Maltose (in malt).
They are also soluble in water and taste sweet. Eg
- Glucose + Fructose = Sucrose
-
- Glucose + galactose = Lactose
3. Polysaccharides: Polysaccharides are many simple
sugars join together to form a very large molecule in a long
chain. Examples are Cellulose of plant cell walls, Starch and
Glycogen. Most polysaccharides are insoluble and they do
not taste sweet.
FUNCTIONS OF CARBOHYDRATES
1. It provides energy for daily activities. Energy
is released by respiration.
2. Used to build body parts like exoskeleton /
chitin.
3. Serves as building block of most nutrients.
4. Mucus which serves as lubricant in the body
is composed of carbohydrate.
LIPIDS
Fats and oil are examples of lipids. Fats is solid and oil liquid at room
temperature. They contain 3 different atoms – carbon, hydrogen and
little oxygen. The molecule is made up of four smaller molecules
joined together (One glycerol and three fatty acid molecules). Lipid is
Insoluble in water.
FUNCTIONS OF FATS
• Fats as secondary source of energy, even more that carbohydrate.
• Supply essential fatty acids and glycerol to the body
• Provides fat soluble Vitamins
• Serves as insulators in the body.
• It maintains body temperature in the body.
WATER
Water is made up of Hydrogen and Oxygen atoms. 80% of the
human body is made up of water. Water is necessary for most
metabolic reactions that occur in body serving as an important
solvent.
• Water is useful because if the cells dry out, their reactions will
stop and the organism dies.
• Water is needed to dissolve enzyme and nutrients in the
alimentary canal for digestion to take place.
• Water help to get rid of waste product from body.
• Water is the constituent of blood plasma needed to transport
useful substances round the body.
PROTEIN
Protein contains carbon, hydrogen, oxygen, nitrogen and
sulfur. Protein molecules are made of long chains of smaller
molecules; amino acids joined end to end. There are 20
different amino acid and some are soluble in water such as
hemoglobin while some are insoluble like keratin found in
hair and fingernails.
FUNCTION OF PROTEIN
1. Used for making new cells and tissues /body building.
2. For growth
3. For repairing damaged body parts; worn-out cells and tissues.
4. Used for antibody production.
5. Used for enzymes and hormones production.
6. Supply amino acids to the body
FUNCTIONS OF PROTEIN
• Some protein are soluble in water example
hemoglobin.
• Insoluble protein – keratin, hair and
fingernails.
• Used for making new cells.
• Used for growing and repairing damaged body
parts.
• Used for antibody production.
DNA
DNA stands for deoxyribonucleic acid. It is a
chemical that are inherited from parent
organisms to makes up genes and
chromosomes.
DNA is made up of two long strands twisted
together to form spiral called helix and held
together by a weak hydrogen bond.
Each strand has four series of bases arranged
along it. They are Adenine, Thiamine, Guanine
and Cytosine. The sequence of the bases
provide code to made protein and determine
how our cells, tissues and organ develop.
A=T
G=C
NUTRITION
One of the main characteristics of living things is their ability to
feed. This is called nutrition. Both plants and animals feed.
TYPES OF NUTRITION
There are two types of nutrition namely’
1. AUTOTROPHIC NUTRITION: This occurs in organisms which can
manufacture their own food. They are plants and can also be called
autotrophs. Most autotrophs can manufacture their own foods through two
processes namely
a. Photosynthesis.
b. Chemosynthesis
2. HETEROTROPHIC NUTRITION: This occurs in organisms which cannot
manufacture their own food but depend directl or indirectly on plants for
food. All animals are autotrophs and can also be called consumers.
PLANT NUTRITION
PHOTOSYNTHESIS
Photosynthesis is defined as the process by which
green plants manufacture their food using carbon
dioxide and water in the presence of sunlight trapped
by chlorophyll. The food manufacture is an organic
compounds while water and carbon dioxide are
inorganic compounds. It is an endothermic reaction
and can also be said to be holophytic mode of
nutrition. Spirogyra, maize plants, nostoc and other
flowering plants are common examples.
The equation representation of photosynthesis is;
.
6CO2 + 6H2O
C6H12O6 + 6O2
(Carbondioxide)
(Water)
(Glucose)
(Oxygen )
STAGES OF PHOTOSYNTHESIS
1. LIGHT STAGE/REACTION: This reaction occurs during the
day or in the presence of light. The chlorophyll in the green
plant absorb sun energy. The solar energy is used to split
water into hydrogen ions and hydroxyl ions in a process
called photolysis. The hydroxyl ions is further converted into
water and oxygen released by reduction process.
Chlorophyll
4H+ + 4OH-
4H2O
Sunlight
4(OH-)
2H2O + 4O2
2. DARK STAGE/REACTION: This reaction occurs at night or in
the absence of light. The carbon dioxide reacts with the
hydrogen ions from the light stage to form their food
(glucose).
6CO2 + 4H+
6C6H12O6 + 6H2O
Materials and Conditions Necessary for Photosynthesis
1. Carbon (iv) oxide – This is derived from the
atmosphere and it diffuses into the intercellular spaces
through the stomata of the leaves.
2. Water - Water is derived from the soil.
3. Mineral Salts – Mineral salts are derived from the soil.
4. Sunlight – This is obtained from solar energy. The light
from the sun is trapped by the chlorophyll of the
leaves.
5. Optimum Temperature – This is derived partly from
Solar energy and partly from chemical reactions witin
the leaves during which heat is generated.
6. Chlorophyll – Green coloring found in pallisade and
spongy mesophyll of the leaves where food is
synthesized within the plant.
Structure of the leaf
Photosynthesis occurs in the leaves. CO2 enters the
leaf through tiny openings on its surfaces called
stomata and water enters the root then pass
through the xylem to the leaf. The glucose is
converted to sucrose and moved via the phloem to
the stem and root.
1.Epidermis: Tightly packed layer that secretes waxy cuticle.
2.Cuticle: It prevents water loss from the leaves.
3.Palisade mesophyll: Tightly packed layer containing many
chloroplast for photosynthesis.
4.Spongy mesophyll: Loosely packed layer containing fewer
chloroplast for photosynthesis.
4. Air space: Hold gases (Oxygen and carbondioxise)
5. Stomata: Openings surrounded by guard cells for
gaseous exchange.
Chemosynthesis
Chemosynthesis is the process by which non-green plants and
certain organisms like bacteria, use chemical energy derived
from inorganic materials to produce their food (carbohydrates).
The inorganic materials include ; Carbodioxie, ammonia, water
or nitrite.
Nitrosomonas and Nitrobacter are common examples of
chemosynthetic bacteria.
ANIMAL NUTRITION
All living organisms need food for their survival and daily
activities. Plants can manufacture their own food through
a process called photosynthesis, hence they are called
autotrophs. On the other hand, animals cannot
manufacture their own food as they depend on plants
directly or indirectly for their food, hence they are called
heterotrophs. Animals sometimes are classified
according to the type of food they eat. On this basis, they
are classified into three groups, namely:
1. Carnivorous animals: These animals feed only on flesh
or other animals, e.g Dog, Lion, Lizard, Snake, Cat etc.
2. Herbivorous animals: These animals feed on plants,
e.g. goat, sheep, rabbit etc.
3. Omnivorous animals: These animals feed on both
plants and animals, e.g. man, pig etc.
Classes And Sources Of Food
1. Carbohydrates:
2. Carbohydrates are mainly energy giving
food and may be classified as
monosaccharides, disaccharides, or
polysaccharides depending on the
number of monomer (sugar) units they
contain. They constitute a large part of
foods.
Sources: Rice, noodles, bread, plantain,
pasta, yam and other grain based
products.
2. Protein
Breaking down existing protein, some glucose can be
produced internally; the remaining amino acids are
discarded, primarily as urea in urine.
Sources of protein are Beans, Milk, Eggs, Meat, Nuts
etc.
3. Fats and oil
Fats may be classified as saturated or unsaturated depending
on the detailed structure of the fatty acids involved. Fats is
solid at room temperature while oil is liquid at room
temperature.
• Trans fats are a type of unsaturated fat with trans-isomer
bonds; these are rare in nature and in foods from natural
sources; they are typically created in an industrial process
called (partial) hydrogenation.
Sources of Fats and oil: Butter, egg yoke, lard, fatty meat,
margarine, vegetable oil, palm oil etc.
4. Vitamins
Vitamins are recognized as essential nutrients, necessary in
the diet for good health. Human body has some capacity to
produce certain vitamins useful for survival and health while
others are derived from food.
(Vitamin D is the exception: it can alternatively be
synthesized in the skin, in the presence of UVB radiation.)
• Excess of some vitamins is also dangerous to health
(notably vitamin A), and for at least one vitamin, B6, toxicity
begins at levels not far above the required amount.
• There are two types of vitamins which are;
1. Water – soluble Vitamins: These are vitamins that
dissolved in water. They include Vit B and C.
2. Fat – soluble Vitamins: These are vitamins that
dissolved in fat. They include Vit A, D, E and K.
5. Minerals
Dietary minerals are the chemical elements required by living
organisms in small quantity to promote health. Mineral elements are
grouped into 2 namely;
1. Macronutrients/ Major elements: These are elements or minerals
needed in large amount. They include; Potassium, oxygen, iron,
phosphorus, Nitrogen, calcium, hydrogen, magnesium, sulphur,
carbon
2. Micronutrients/ Minor or trace elements: These are elements or
minerals needed in small amount in the body. They include; Zinc,
copper, Molybdenum, Manganese and silicon.
Sources are sea foods, dairy food, table salt, liver, milk, kidney
• On the other hand, minerals are often artificially added to the diet
as supplements; the most famous is likely iodine in iodized salt which
prevents goiter .
6. Water
About 70% of the non-fat mass of the human body is made of
water. To function properly, the body requires between one and
seven liters of water per day to avoid dehydration; the precise
amount depends on the level of activity, temperature, humidity,
and other factors. Water aids digestion and is needed by the
body to also wash away toxic materials.
Sources of water: Fruits, drinking water, soft drinks etc.
Others include roughages or fibres
Dietary fiber consists mainly of cellulose, a large carbohydrate polymer that
is indigestible because humans do not have the required enzymes to
disassemble it. There are two subcategories: soluble and insoluble fibre.
Whole grains, fruits (especially plums, prunes figs, and vegetables are
good sources of dietary fibre.
• Fibre is important to digestive health and is thought to reduce the risk of
colon cancer.
- It can help in alleviating both constipation and diarrhea.
- Fiber provides bulk to the intestinal contents, and
- Insoluble fiber stimulates peristalsis (the rhythmic muscular contractions of
the intestines which moves along the digestive tract).
• Some soluble fibers produce a solution of high viscosity which slows the
movement of food through the intestines.
• Fiber, help lessen insulin thereby controlling sugar level.
Balanced Diet
Balanced diet is a diet containing all the six classes of food
substances required by an organism or man in the correct proportion
or right amount . Balanced diet is also refers to as adequate diet. The
balance diet must contain the six food nutrients such as
carbohydrates, proteins, fats and oil, minerals, vitamins and water in
their correct proportion.
Importance of Balanced Diet
Balanced diet is important to the body in the following ways:
1. Balanced diet makes us healthy and by so doing, makes us to be
resistance to diseases.
2. It encourages growth and normal development of the body.
3. It also provides energy required for normal activities.
4. Balanced diet prevents malnutrit
ion, deficiency diseases.
Lack of some food substances, e.g protein in a diet can cause a
nutritional disease called kwashiokor in children which is
characterized by a very big head, narrow neck, big, swollen and shiny
stomach, flat buttock, and very slender and narrow legs.
Digestive Enzymes
An enzyme is an organic catalyst usually proteinous in nature, which
promotes or speeds up chemical changes in living cells but are not
themselves used up in the process. Enzymes accelerate metabolic
reactions without changing in the process.
• Characteristics
1. All enzymes are proteins in nature.
2. Enzymes are usually involved in reversible reactions.
3. Enzymes are affected by the pH (acidity or alkalinity) of their
surrounding. They are destroyed by strong acids or alkali.
4. Enzymes accelerate the rate of chemical reaction.
5. Each enzyme is specific in action, i.e., an enzyme or a group of
enzymes deals with only one process..
It is clear that all digestive enzymes belong to the class called
hydrolases. the class, hydrolases generally refer to enzymes that
break up various bonds (i.e. breaking large molecules into smaller
particles) in the presence of water.