BIOLOGY PRACTICAL SUMMARY FOR NECTA EXAM 2023

BIOLOGY PRACTICAL POSSIBLE AREA OF CONCENTRATION TOWARD NECTA EXAM 2023

1. CLASSIFICATION OF LIVING THINGS

1.1. Kingdom Plantae
General features of kingdom Plantae

i. They are multicellular ii.

ii. They are eukaryotic with cellulose cell walls

iii. They are autotrophs

iv. They store foods as starch

v. Some reproduce sexually and others asexually

vi. They show limited movement

1.1.1.Division bryophyta

Plants in this division include mosses and liverwort

Distinctive features of division bryophyta

i. They are generally small in size

ii. They have leaf-like(thallus) and root-like(rhizoids) structures but no true leaves and roots

iii. They lack vascular tissues (xylem and phloem)

iv. They are commonly found in moist areas

v. They reproduce both sexually and asexually

vi. They show alternation of generation

Structure of Mosses (moss plant)

This consist of a stem like structure bearing spirally arranged leaf- like extensions. They are anchored to the substratum by rhizoids. The capsule is the structure where sporangia are housed.

Life cycle of moss plant

Explain how moss plant reproduce

a. Sexual reproduction

The reproductive parts of a moss plant are antheridium (male part) and archegonium (female part)

The antheridium releases motile sperms. The sperm swim in water to reach and fertilize the egg in the archegonia to form the zygote.

The zygote develops into young sporophyte plant which grows while still attached to the archegonium.

b. Asexual reproduction

When it matures, the sporophyte forms a capsule containing spores. When the spores are mature, the capsule burst open, and the spores are carried away by air.

If they land in a suitable place, the spores germinate and produce new moss plants

Advantages of moss plants

i. Mosses help to decompose dead logs.

ii. Mosses serve as pioneer plants on bare ground and help to create a suitable environment for the growth and development of other plants.

iii. Mosses retain a lot of water. They therefore help to keep the soil moist.

iv. When mosses grow on a piece of land, they hold the soil particles together and help to prevent soil erosion.

v. Mosses also provide shelter for insects and other small animals.

vi. Some birds and mammals use mosses as nesting material.

vii. Mosses are also used as cushioning material in furniture or in shipping, for example when transporting flowers.

viii. Due to their good water-holding capacity, moss plants are mixed with soil to improve the soil's moisture content.

ix. Sphagnum moss has antiseptic properties. During World War I, it was widely used as a bandage for wounded soldiers.

Disadvantages of moss plants

i. Mosses occur as weeds in gardens and other places. They are very difficult to get rid of.

ii. Mosses growing around ponds and other small water bodies can grow onto the water and cover it completely, causing the area to become marshy.

1.1.3. Division angiospermophyta

It comprises plants known as flowering plants e.g. Mango tree

General characteristics of angiospermophyta

i. Angiosperms are found in both aquatic and terrestrial environments

ii. They have well developed root system, stem and leaves

iii. Their seeds are enclosed and protected in the ovary

iv. They have well developed tissues which contain xylem and phloem

Classes of the division angiospermophyta

a. Class monocotyledonae

b. Class dicotyledonae

Class dicotyledonous

This class contains plants with seeds having two cotyledons eg. Beans, mangoes, coffee, groundnuts, sunflower plants etc.

Distinctive features of the class dicotyledonae

a) Dicot leaves have network venation

b) They stem have vascular bundles appearing in ring form

c) They have tape root system

d) Their seed embryo has two cotyledons

e) Floral parts appear in multiple of four/five

f) Dicot leaves are supported by the petioles

g) They have shorter and broader leaves

Advantages of the division Angiospermophyta

a) Angiosperms provide foods such as beans, sugarcane, cabbage etc.

b) Some species are used as medicine

c) Some provide fibres that are raw materials for textile industries. E.g. cotton

d) They prevent soil erosion

e) Make the environment attractive

Disadvantages of the division angiospermophyta

a) Some angiosperms are poisonous

b) Drugs from angiosperms may be dangerous if they are abused

c) Some angiosperms are weed plants which compete food with crops

d) Others are parasites on other plants

e) Some species can colonize water bodies and affect water bodies.

1.2. Kingdom fungi

General features of kingdom fungi

i. They are found in damp or wet places

ii. They are eukaryotic with the cell wall made up of chitin

iii. They are heterotrophs. Some are saprophytic and others are parasitic

iv. They store food as glycogen

v. They reproduce using spores

1.1.1. Phylum basidiomycota

This phylum comprises fungi such mushroom, toadstools, puffballs, bracket fungi, rust fungi and smut fungi.

Characteristics of mushrooms

i. They grow on dead and decaying matter

ii. The pileus is the cap of the mushroom containing gills

iii. The gills produce basidiospores at their tips

iv. The stalk (stem-like) of the mushroom is called stipe. It ensures that the pileus is well positioned above the soil for dispersal of spores

v. The hyphae anchor the mushroom and absorb nutrients from the decomposing matter

Adaptations of mushroom

i. They produce enzymes on the surface of their mycelium which help them to break complex food particles

ii. Possess pileus(cap) containing special hyphae called gills

iii. The gills produce basidiospores at their tips.

iv. Has stipe (stem-like part) which ensures that pileus is positioned above the soil for the dispersal of spores

v. Possess hyphae that anchors mushroom on the substrate and absorb nutrients

Economic importance of basidiomycota (mushroom)

i. They are source of food to man and other species.

ii. They can prevent the accumulation of dead matters by decomposing them.

iii. Some of them are poisonous e.g. amanita species

iv. They are used in genetic engineering and research

Observable features of basidiomycota (mushroom).

a. They have gills.

b. They have a ring.

c. Have cap (pilleus).

d. Have stalk

Habitat of basidiomycota (mushroom).

v They are living on land (terrestrial) on dead and decaying organic matter.

Mode of reproduction of basidiomycota (mushroom)

v They reproduce both asexually and sexually by spores formation.

Common name is Mushroom.

Scientific name of mushroom is Agaricus compestris.

Classification of mushroom to class level

Organism- Mushroom

Kingdom - Fungi

Phylum - Basidiomycota

Class - Agaricomycete

1.3. Kingdom Animalia

The distinguishing characteristics of kingdom animalia

i. Animals are multicellular and each cell is bound by a plasma membrane.

ii. Animals bodies are differentiated into tissues

iii. Animals are heterotrophic.

iv. Animals are capable of locomotion.

v. Animals have a nervous system

1.3.1.Phylum Annelida

The word annelid is derived from a Latin word ‘’annelus’’ which means little ring. Thus members of this phylum are known as ringed or segmented worms. Annelida is a large phylum comprising of rag worms, lugworms, earthworms and leeches

The most common species is the earth worms

General features of annelids

i. They have a lip like extension on the first segment above the mouth called prostomium

ii. Most annelids have chaetae. Chaetae is chitinous hair-like structures used for locomotion.

iii. Some annelids have well developed metameric segments through the body

iv. They have bilateral symmetrical bodies

v. Excretion takes place in convoluted tube-like structures called nephridia found in each segment

vi. They have moist outer covering called cuticle vii. They reproduce by both asexually and sexually

vii. They have closed circulatory system where by the blood flows

viii. They have a central nervous system with paired cerebral ganglia in which paired commissures around the gut lead to a double ventral nerve cord

ix. They arc eucoelomates meaning that their body cavities are lined by mesodermal tissues in both sides.

x. They have triploblastic bodies

Distinctive features of annelids

Features which distinguish annelids from other animals are as follows:

a. Most annelids have hair-like structures called chaeta or setae made up of chitin.

These are used for locomotion.

b. They have perfect metameric segments throughout the body.

Structure of earthworm

Ø An earthworm is an elongated, roughly cylindrical and metamerically segmented organism.

Ø Each segment contains body systems such as circulatory, nervous, excretory and digestive systems. It has a complete digestive system that runs through the length of its body with both mouth and anus.

Ø The circulatory system is simple and closed. The earthworm has a central and peripheral nervous systems.

Ø Earthworms are hermaphrodite meaning that each individual has both male and female reproductive organs.

Advantages of annelids

i. Some annelids improve soil aeration through burrowing and mixing up of soil layers.

Earthworms play very important role in improving soil aeration.

Hence maintaining soil. Fertility.

ii. They are used for commercial production of compost manure in the process known as vermicomposting.

iii. Some annelids are used as a bait in the fishing industry Examples of annelids used as bait include earthworms and lugworms.

iv. They are used as source of nutritious food for some fish and birds. They are rich in proteins and vitamins.

v. Some annelids are ecological decomposers. Hence, they contribute to nutrient circulation because they feed on decaying organic matter.

vi. They remove pollutants from the soil and clean the environment by transforming organic wastes during feeding.

vii. Faeces and urine of some annelids have considerable value as manure and increase soil fertility.

viii. They are used as specimens in biological studies.

ix. The excretory waste of some annelids which are in the form of cast increases sticking together of soil particles. This in turn increases water holding capacity of the soil.

Disadvantages or annelids

In some cases, annelids are harmful. The harmful effects of the annelids include the following:

i. Some annelids damage young roots of the growing plants.

ii. Leeches are harmful to mammals, reptiles and fishes because they suck blood.

iii. Earthworms can increase soil porosity and aeration which may cause water loss by seepage from the forms.

Advantages of earthworm in agriculture

i. Earthworms help in soil formation by barrowing process

ii. They add nutrients when they decompose or giving out waste products from their bodies

iii. They increase soil aeration. During the process of barrowing they increase soil porosity hence soil aeration

iv. Their burrows help rainwater to drain through the soil more easily and prevent water logging.

v. They drag leaves and other plants part into the soil when they feed which adds humus content of the soil.

vi. They are used by fishermen to trap fish during fishing

vii. They improve water holding capacity of the soil

Habitat of earthworm

They live in moist soil

Mode of nutrition of earthworm

They are heterotrophs (omnivorous)

Mode of reproduction of earthworm

They reproduce sexually by producing egg and sperm at the clitellum. Fertilization is external

Classification of earthworm to class level

Organism - Earthworm

Kingdom - Animalia

Phylum - Annelida

class - Oligochaeta

1.3.2.Phylum arthropoda General features of arthropods

i. They have jointed and paired appendages that may be modified in various ways to form structures such as antennae, mouthparts, legs and reproductive organs.

ii. They have segmented bodies which are organized into regions called tagmata. These regions are the head, thorax and abdomen

iii. They have a coelom that is reduced and confined to cavities of excretory organs and reproductive duct. They also have another cavity called haemocoel which is formed during their development.

iv. They have exoskeleton made up of chitin covering their body.

v. They have a ventral nervous system.

vi. They have open circulatory system which is dorsally positioned.

vii. Their body plan is bilaterally symmetrical.

viii. They have compound or simple eyes.

Distinctive features of arthropods

i. They have jointed appendages which serve different purposes such as feeding, locomotion and sensation.

ii. They have segmented bodies organized into regions called tagmata.

iii. They have an exoskeleton which is made up of a chitin. The exoskeleton is usually stiff rigid or flexible.

Classes

i. Class Arachnida

ii. Class Diplopoda

iii. Class Insecta

i. Class Arachnida

Arachnids are terrestrial arthropods consisting of animals whose bodies are divided into two regions; prosoma and opisthosoma.

In some arachnids the two region are separated by a narrow waist like constriction. The prosoma is partly or completely covered with a carapace like shield.

Members of this class lack antennae and the majority are carnivores which feed on other invertebrates or small vertebrates. Others arachnids such as ticks and some mites are ectoparasites which feeds on the blood of vertebrates.

Examples of arachnids are spiders, mites, ticks and scorpions.

Distinctive features of arachnids

Arachnids possess various unique features which distinguish them from other Arthropods. These features include:

i. They have no antennae, instead they have a pair of pedipulps which they use for defense and detection of stimuli.

ii. They have four pairs of walking legs that arc attached to the cephalothorax.

iii. They have only simple eyes used for vision while others are completely blind.

iv. Gaseous exchange in arachnids is by means of book lungs or trachea.

v. They lack mandibles

Structure of the spider

Structurally the body of a spider is divided into two main parts called cephalothorax or prosoma and opisthosoma. They have six pairs of appendages which include four pairs of legs, chelicerae (mouthparts) and pedipalps.

On the ventral part of the abdomen, there are two hardened plates covering the book lungs. The spinnerets which extrudes silk arc also found in the abdomen. They possess very small eyes which are often clustered

Economic importance of arachnids

Arachnids are both advantageous and disadvantageous to human being and other organisms as follows;
Advantages of arachnids

a. Some arachnids such as mites play an important role in the formation of humus from decomposed leaf litter and wood.

b. Many arachnids are used as food by other animals. For example, spiders arc used as source of food by frogs, lizards and birds.

c. Spiders and other arachnids teed on wide range of pests thus helping to keep the population of pests under control.

d. Silk from spiders can be harvested for production of useful products such as surgical threads and bullet-proof vests.

e. They are used in biological studies and research.

Disadvantages of arachnids

a. Some arachnids such as scorpions can sting human beings and release their venom that cause severe pains. The bite from some spiders such as the black widow Latrodectus species can cause serious health problems in children and even death.

b. Some arachnids arc parasites to mammals and other vertebrates. Examples of such arachnids are ticks and mites which usually bite humans and other animals causing pain. They can also transmit diseases.

c. Some arachnids destroy crops and other properties. Examples of such arachnids are mites that attack food crops (on farm and in storage) and timber.

Observable features of spider, and ticks

i. Have four pair of legs

ii. Have simple eyes

iii. Body divided into two regions

iv. Have poisonous sting

Adaptations of spider, and ticks

a. Have simple eyes for sight

b. Have poisonous sting for protection

c. Have legs for locomotion Habitat of spider and ticks

d. They are terrestrial organisms living in rocks, roof of the walls and in the soil

Classification of spider and ticks to class level

Organism - Spider

Kingdom - Animalia

Phylum - Arthropoda

Class - Arachnida

Tick

Kingdom - Animalia

Phylum - Arthropoda

class - Arachnida

ii. Class Diplopoda Structure of a millipede

The body of millipede is elongated, cylindrical and segmented. The body consist of a series of segments whose number varies depending on the species.

The segments contain glands that secrete a noxious chemical to repel predators.

Each trunk segment hears two pairs of walking legs with exception of the segment behind the head.

Millipedes also have a head with one pair of antennae that help them to detect stimuli from the surroundings.

The head also has one pair of mouth parts that is found in from of the head.

Most millipedes have simple eyes located above the jaws. Such millipede have ability to see. However, some millipedes have no eyes at all, so that they cannot see.

Economic importance of diplopods

Diplopods are both advantageous and disadvantageous to both plants and animals including human being.

Advantages of diplopods

i. Most diplopods are used as source of food to other animals including birds, reptiles and amphibians.

ii. They are also used in biological studies and research. Since diplopods feed on decaying plants and animal matter,

iii. They help in the recycling of nutrients in the ecosystem.

Disadvantages of diplopods

i. Some herbivorous millipedes can cause damage to crops in the field.

ii. Burrowing diplopods can cause some damage to the roots or germinating seeds.

Adaptation of millipede

i. They possess legs for locomotion

ii. Presence of exoskeleton which protect them from external injury

iii. They secrete a toxic fluid for protection from predators.

iv. They live in soil and they are brown blackish in colour gives them camouflage.

v. Have one pair of antenna for sensation

Observable features of millipede

i. Have two pairs of legs in each segment

ii. Have cylindrical body

iii. Have one pair of antennae

iv. Body divided in many segment

v. Have simple eyes

Habitat of millipede

They lives in shady moist soils rich in organic matter

Common name is millipede.

Classification of millipede to class level

Organism - Millipede

Kingdom - Animalia

Phylum - Arthropoda

Class - Diplopoda

iii. Class insecta

Members of class lnsecta are the most diverse and most abundant animals on the earth. They are found in all environments or habitats including freshwater, terrestrial and marine habitats.

Common features shared by members of the class Insecta

i. Their bodies are divided into three distinct parts: the head, thorax and abdomen.

ii. They have three pairs of walking legs.

iii. Their heads bear one pair of antennae. The antennae are used as sense organs for detection of odour molecules in the air, changes in the concentration of water vapour, sounds and for gauging air speed.

iv. Most insects have one or two pairs of wings located on second and third thoracic segment.

v. They usually have three pairs of mouthparts which arc mandibles, maxillae, and fused labium. These parts are modified in different ways in order to suit various functions such as piercing, sucking, chewing and biting. This enables insects to feed on different diets.

Examples of organisms belonging to class lnsecta include grasshoppers, butterflies, houseflies.

Cockroaches, beetles, bees, ants, wasps and termites.

Distinctive features of insects

Insects differ from other arthropods in the following ways:

i. Their bodies are divided into three main regions or tagmata, namely the head, thorax and abdomen.

ii. They have three pairs of jointed walking appendages.

iii. They have a highly developed mechanism of gaseous exchange through trachea.

iv. They have holes called spiracles located on the abdomen and joined lo the tracheal tubes which help to ensure efficient gaseous exchange

v. Majority have one or two pair of wings

vi. Few lack wings for example fleas and lice.
Structure of a g1asshopper

A typical example of an organism in the class Insecta is a grasshopper. The body of a grasshopper is elongated and segmented. It is divided into a head, thorax and abdomen

The head of the grasshopper has a pair of antenna and compound eyes. Each compound eye is made up of thousands of tiny units closely packed together.

The head also consists of three pair of mouthparts namely mandibles, They have three pairs of legs

The body of the grasshopper is covered by a rigid exoskeleton

Economic importance of insects Advantages of insects

Insects are both advantageous and disadvantageous to humans and other organisms.

i. They are used for production of various substances. For example, honey bees produce honey, wax and bee venom silk worms produce silk that can be used for commercial purpose.

ii. They are used in biological control of pests. Insects have been used effectively as predators to kill or control pests. For example, lady beetles are used to kill aphids. Aphids arc the insect pests that transmit viruses to plants.

iii. Insects such as bees and butterflies arc useful in agriculture as they act as pollinators. Many plants depend on insects for pollination.

iv. They are used in scientific research particularly in fields of physiology, genetics and evolution. The fruit flies (Drosophila melanogaster are among the insects used for this purpose.

v. Some insects are used in the production or medicine. Such insects include blister beetles that produce cantharidin which is used for treatment of urine genital diseases.

vi. Many insects are used as food, they are a good source of proteins for human beings and other animals. Examples or such insects include winged termites, edible grasshoppers, locusts, and cockroaches, larvae of beetles, butterflies and moths.

vii. Some insects are scavengers and feed on rotten or decayed materials hence helping in reducing rubbish and ensuring nutrient recycling in the ecosystem. Examples or such insects arc cockroaches.

viii. Some insects improve aeration and soil fertility. For example, termites breakdown plant tissues thus improving soil facility

Disadvantages of insects

i. Some insects such as wasps and bees can cause painful bites and stings. Stinging insects that live in colonies can cause significant injury and even death.

ii. Some insects are vectors of animal and plant diseases. For example, mosquitoes carry Plasmodium spp. which cause malaria. Tsetse flies carry Trypanosoma spp. a parasite which cause sleeping sickness to human beings. In addition, white flies carry tomato yellow leaf curl virus which cause chlorosis in plants.

iii. Some insects destroy trees and crops. Examples of such insects include locusts and the caterpillars.

iv. Some insects are ectoparasites of mammals. For examples jiggers and bedbugs which tend to suck blood from their hosts.

v. Some insects destroy human properties. Example cockroaches which spoil food. termites, beetle and carpenter bee that cat wooden furniture and moth larvae that feed on carpets and clothes.
Observable features of Housefly, Cockroach, Beetle,

Butterfly and Grasshopper

i. Have one pair of antennae

ii. Have jointed legs

iii. Have pair of wings

iv. Have compound eyes

v. Body divided into three parts

Adaptations of Housefly, Cockroach, Beetle, Butterfly and Grasshopper

i. Have antennae for sensation

ii. Have legs for locomotion

iii. Have wings for flying

iv. Have compound eyes for maximum sighting

v. Have abdomen for reproduction and respiration

Housefly

Kingdom - Animalia

Phylum - Arthropoda

Class - Insecta

Cockroach

Kingdom - Animalia

Phylum - Arthropoda

Class - Insecta

Beetle

Animalia

Arthropoda

Insecta

Butterfly

Aniamalia

Arthropoda

Insecta

1.3.3 Phylum Chordata

This phylum comprises of animals with a high degree of body organization.

Animals under this phylum possess a notochord during embryonic development that strengthens and supports the body.

In protochordates. The notochord persists throughout life, but in most vertebrates it is replaced by the vertebral column in adulthood.

General features of chordates

Chordates possess the following features:

i. They are triploblastic animals.

ii. They are coelomate animals.

iii. Their bodies are metamerically segmented and bilateral symmetry.

iv. Some are homotherms while some are piokiotherms

v. Most chordates have a ventral heart. (l) Most chordates have a closed circulatory system.

vi. Most have endoskeletons made up of bones and cartilages

vii. Some chordates have central nervous system made up of the well-developed brain and a spinal cord.

viii. They occupy both terrestrial and aquatic habitats.

ix. Some chordates are viviparous in which their young develop inside the body while others are oviparous as their young develop outside the body

x. Most chordates have a complete digestive system with two openings, the mouth and anus.

xi. Most chordates have segmented muscle blocks called myotomes, one muscle block on either side of the body.

Distinctive features of chordates

Chordates have unique features that differentiate them from other animals.

They have the following features at some stages of embryological development:

i. A notochord.

ii. Pharyngeal pouches or gill slits.

iii. Post-anal tail.

iv. A dorsal hollow tubular nerve cord.

Classes

i. Osteichthyes(bony fish)

ii. Class amphibia

iii. Class reptilia

iv. Class mammalia

v. Class aves

i. Class Osteichthyes

This class comprises of the bony fish. Their skeleton is made up of hard bones instead of cartilage.

Examples of bony fish include tuna, tilapia, Nile perch, herring, butterfly fish and catfish

Distinctive features of bony fish

The following features differentiate bony fish from other chordates:

i. They have four pairs of visceral clefts as their gill openings. These are covered by an operculum.

ii. Most of bony fish have swim or air bladder which provides them buoyancy during swimming.

iii. Most have a bony endoskeleton and their skin is covered by glands producing mucus that make them slippery.

iv. Most have symmetrical or homocercal caudal fins. This means that their caudal fins can be divided into equal parts.

v. They have terminal mouth.

Structure of a Tilapia

Tilapia fish has a laterally flattened body that tapers at both ends.

lt has a streamlined body shape that enables it to overcome water resistance during swimming.

The surface of its body is covered with overlapping scales.

In addition, tilapia has a lateral line that runs along the side of its body. The lateral line is a series or sensory organs called neuromasts that help the fish to sense vibrations and water pressure.

Economic importance of bony fish

Most bony fish have both advantages and disadvantages to humans and other animals.

Advantages of bony fish

i. Most bony fish are rich in protein, hence, they are used as food to human and other animals.

ii. They are also source of income to fishing communities. Industrially processed fish products such as bones can be transformed into usable goods such as chicken feed.

iii. Oil produced from the fish are also useful as medicine. Some bony fish are used for ornamental purpose. Additionally some bony fish are used in biological studies and research.

Disadvantages of bony fish

i. Sting from some bony fish such as stonefish can cause pain, swelling, necrosis and even death.

ii. Shocks from electric eels and electric catfish can cause injury or death due to drowning.

iii. Also, some exotic bony fish when introduced into a new habitat can cause extinction of endemic fauna due to competition and predation.

Adaptations of tilapia

i. It has tail for swimming

ii. Possess gills for gaseous exchange

iii. It has pair of eyes and nostrils for sensitivity

iv. Cycloid scales pointed backward to support movement during swimming

v. Possess swim bladder for buoyancy maintenance

Observable features of tilapia

i. Has eyes, and terminal mouth

ii. Possess tail

iii. Has gills

iv. Has cycloid scales

v. Has fins

Habitat of tilapia

They are living in water (aquatic organism) Mode of reproduction of tilapia fish Reproduce sexually by external fertilization

Classification of tilapia fish to class level

Organism - Tilapia fish

Kingdom - Animalia

Phylum - Chordata

Class - Osteichthyes

ii. Class amphibia

The term Amphibia comes from two Greek words "amphi" meaning "both" and "bios" which means "life". Therefore. Amphibia literally mean double life. This is due to the fact that amphibians live both in water and on land.

Most amphibians spend their life partly in aquatic environment and partly in terrestrial environment.

They have two pairs of pentadactyl limbs for locomotion except caecilians which are limbless.

The forelimbs of some amphibian have less musculature while the hind limbs of frogs and toads arc long with powerful muscles for jumping.

Distinctive features of amphibians

Amphibians have the following unique features that differentiate them from other chordates:

i. They have protruding eyes for wide visibility of prey.

ii. Amphibian eggs have a jelly structure which is prone to dehydration when exposed to air.

iii. During the larval stage amphibians use gills for gaseous exchange. In adult stage, amphibian use their skins when they are in water and lungs when they are on land.

iv. They have moist skin and most occupy both water and land environments.

STRUCTURE OF A FROG AND A TOAD

Economic importance of amphibians

Amphibians have both advantages and disadvantages to humans and other organisms as follows:

Advantages of amphibians

i. Some amphibians arc source of food to humans and other organisms such as snakes and birds.

ii. They are also used in biological studies and research. For example, frogs and toad are dissected in school laboratories to study various body systems.

iii. Since they eat flies, they help in eliminating disease vectors such as houseflies.

iv. In addition, some amphibians have unique features that attract researchers and tourists, hence act as the source of income. The Kihansi Spray Toad (Nectophrynoides asperginis) for example has unique biological feature of giving birth to live Youngs.

v. In the amazon basin, secretions from some amphibians are used by natives to produce toxin darts used for hunting purpose.

Disadvantages of amphibians

i. During breeding period, some amphibians such as male frogs and toads make loud noise thus annoying people living in that environment.

ii. They also contribute to water pollution by laying their eggs on the surface of water. Some frogs, toads and newts produce toxins which cause skin irritation and severe symptoms if ingested Toxins from cane toads can cause seizures, cardiac effects and even death.

Habitat of the frog

They are found normally in damp situations on grass near water, damp ditches and swimming in ponds or streams.

Common name is frog.

Scientific name of frog is Rana temporaria.

Mode of reproduction of frog

They reproduce sexually by external fertilization

iii. Class reptilia

Reptiles are among a diverse group of egg-laying vertebrates. Their bodies are covered with scales or scutes, Reptiles include animals such as crocodiles, alligators, chameleons, tortoises, snakes and lizards.

They undergo internal fertilization and their fertilized yolky eggs are laid on land. However, some reptiles such as snakes are oviparous. This means they lay eggs which remains in the mothers’ body until they are ready to hatch.

Reptiles are found in diverse habitats such as deserts, mountains, rocks, tree tops and in water. They are mostly terrestrial with few aquatic members such as crocodiles, turtles and terrapins.

They are ectothermic (poikilotherms) vertebrates, implying that their body temperature fluctuates according to the change in environmental temperature. Most reptiles have two pairs of pentadactyl limbs. Some members such us snakes and some lizards are limbless.

Distinctive features of reptiles

Reptiles possess the following distinctive features:

i. They have dry skin covered with horny scales or scutes.

ii. Their eyes are located at the front part of the head to facilitate binocular vision. Some reptiles can move each eye independently. This helps to increase their visibility hence locating their food and escaping from predators.

iii. They lay soil shelled eggs called amniotic eggs which protect the embryo from drying out. The eggs have yolk which nourishes the embryo and enables it to develop outside the water environment.

iv. All reptiles have a three-chambered heart except crocodiles which have a four-chambered heart.

v. Most have clawed feet.

Structure of lizards

A lizard is a typical example of a reptile. The body of a lizard is divided into three parts namely head, trunk and tail. Lizards have a dry scaly skin, external ear openings and most of them have clawed feet.

They also possess two pair of legs. In most species the tail is fragile and easily broken but regenerates later. They have shortened legs which help them in walking, but other lizards such as Delma species are legless.

They also possess eyes with movable eyelids. The two eyes can move independently, thus helping lizards to find food and escape from predators.

Economic importance of reptiles

Reptiles are both advantageous and disadvantageous to humans and other organisms as follows:

Advantages of reptiles

i. Reptiles are used by other animals as source of food. For example, birds eat reptiles such as snakes, lizards and chameleons.

Some reptiles such as crocodiles, turtles and snakes are a source of human food in some communities.

ii. Some reptiles also provide valuable skin used in making different products. For example, the crocodile skin is used in making belts, shoes and handbags.

iii. Since reptiles eat small insects they help to reduce harmful insects in the environment or ecosystem. For example, lizards feed on mosquitoes and cockroaches, hence reduce their population in the environment.

iv. Furthermore, some reptiles or their products are used for ornamental purposes. For example, tortoises are used for decoration in homes.

v. Tortoise shells are used to make combs, ornaments and traditional

Disadvantages of reptiles

i. Some reptiles such as crocodiles can attack livestock and humans causing serious injuries or death.

ii. A bite from venomous snakes can also cause serious health problems or death to humans and other organisms.

Class mammalia

The study of mammals is called mammology

Mammalia contains a small number of species but it is probably more successful than other animals

There are terrestrial, aquatic, and aerial mammals; oviparous, ovoviviparous and viviparous mammals.

General characteristics of mammals

1. Body covered with hair.

2. They have integument with sweat, scent, sebaceous, and mammary glands.

3. They have skull with two occipital condyles and secondary bony palate; middle ear with three ossicles (malleus, incus, stapes).

4. They have seven cervical vertebrae; pelvic bones fused

5. They have mouth with diphyodont teeth (milk, or deciduous, teeth replaced by a permanent set); teeth heterodont in most (varying in structure and function)

6. They have movable eyelids and fleshy external ears (pinnae).

7. They have circulatory system of a four chambered heart

8. They have respiratory system of lungs with alveoli

9. They have muscular diaphragm which separates thoracic and abdominal cavities

10. The brain highly developed, especially cerebrum

11. They are endothermic

12. They have separate sexes; reproductive organs of a penis, testes (usually in a scrotum),ovaries, oviducts and vagina

13. They undergo Internal fertilization; eggs develop in a uterus with placental attachment

14. The young are nourished by milk from mammary glands

Common name Rat

Classification of the rat to class level

Organism - Rat

Kingdom - Animalia

Phylum - Chordata

Class - Mammalia

Class aves

The study of birds is called ornithology

Birds are traditionally classified as members of the class Aves (from Latin word avis = bird).

The single unique feature of birds is possession of feathers. No other living vertebrate group has feathers

characteristics of bird

1. Body spindle shaped, with four divisions: head, neck, trunk, and tail

Ø Neck is long for balancing and food gathering.

2. They have four limbs but the forelimbs modified for flying

3. They have circulatory system of 4-chambered heart.

4. They are endothermic (Homoeothermic).

5. Gaseous exchange is by lungs, with thin air sacs

6. Excretory system of metanephric kidney; ureters open into cloaca; no bladder; semisolid urine;

7. Uric acid is the main nitrogenous waste.

8. Sexes are separate; testes paired, with the vas deferens opening into the cloaca; females with functional left ovary and oviduct only, copulatory organ (penis) is present only in few birds e.g. ducks, geese, and paleognathids.

9. Fertilization is internal

The similarities between birds and reptiles

1. Both have scales creates a waterproof barrier that helps prevent dehydration in dry air

2. Both lay eggs – shelled eggs on land (amniotes)

The differences between birds and reptiles

1. Birds have feathers, reptiles do not have feathers.

2. Birds have wings allowing them to fly while reptiles have lack wings

3. Reptiles are cold blooded or ectothermic; while birds are warm blooded or endothermic.

4. Birds have hollow bones making them lighter & able to fly while reptiles have solid, dense bones.

Adaptations of birds for flight

1. They have feathers which are used for flight

2. They have no teeth, urinary bladder, no penis in most birds and have only one ovary of which all of them help to reduce body weight

3. They have pneumatic (air filled) bones which help to reduce body weight

4. They have enlarged sternum where the flight muscles are attached

5. The have long neck for balance

6. They have stream lined body to reduce air resistance

QUILL FEATHER

Possible questions on the quill feather

Describe the basic anatomy and structure of a quill feather

Answer Quill feathers, also known as flight feathers, have a rigid central shaft or quill made of keratin. They feature a tapered shape with a vane on either side of the quill.

The vane is composed of barbs, which further branch into smaller structures called barbules. Interlocking barbules give the feather its shape and function.

What is the primary function of quill feathers in birds?

Answer The primary function of quill feathers, also known as flight feathers, in birds is to enable flight.

Explain how quill feathers contribute to a bird's ability to fly.

Answer These feathers are essential for a bird's ability to achieve and maintain flight.

They play a fundamental role in providing lift and thrust during wing movement, allowing birds to navigate through the air.

How do quill feathers aid in thermoregulation (temperature control) in birds?

Answer Here is how quill feathers help in thermoregulation:

i. Insulation:

Quill feathers, especially contour feathers, have a fluffy and insulating structure. They trap a layer of air close to the bird's body.

This trapped air serves as an effective insulator, reducing heat loss from the bird's warm body to the colder external environment.

ii. Regulating Body Temperature:

Birds are warm-blooded animals, meaning they can maintain a relatively constant body temperature even in varying environmental conditions.

Quill feathers assist in this process by minimizing heat exchange between the bird's body and the surrounding air. In cold weather, they help retain body heat, while in hot weather, they can prevent excessive heat absorption.

iii. Regional Adaptations:

Birds living in extreme environments have specific adaptations related to their feathers. For example, in cold climates, some species have specialized down feathers close to their bodies for maximum insulation.

In desert environments, birds may have fewer or thinner contour feathers to reduce insulation and avoid overheating.

d. Discuss any adaptations or variations in quill feathers among different bird species.

e. How do waterfowl, such as ducks and swans, utilize specialized quill feathers for buoyancy and waterproofing?

2. NUTRITION

Food Test

In this practical, you should test a solution of unknown food substances for starch, protein, reducing sugars, non- reducing sugars, and fats/oils.

Record your procedure, observation, and conclusions,

Then answer questions about nutrition and the digestive system.

i. How to Carry Out Food Tests

When performing an experiment with the aim of identifying certain food content contained in the sample solution different reagents are used specifically in certain food sample as follows

TABLE FOR THE FOOD TYPE, REAGENT USED AND REAGENT COLOUR

FOOD TESTED/FOOD TYPE	REAGENT USED	REAGENT COLOUR
Starch	Iodine solution	Brown
Reducing sugar	Benedict’s solution	Blue
Non reducing sugar	Benedict’s solution	Blue
	Dilute Hydrochloric acid (HCl)	Colourless
	Dilute sodium hydroxide (NaOH)	Colourless.
Protein	Dilute sodium hydroxide (NaOH)	Colourless.
Protein	1% Copper sulphate (CuS	Blue.
Lipids	Sudan (III) solution	Red.

A. Starch

Starch is a carbohydrate which made up by condensation of many glucose molecules.

Ø Food sources which starch is obtained include potatoes, maize, wheat, rice e.t.c

Ø The chemical reagent used to test starch is Iodine solution

Properties of starch

- They are insoluble in water.

- They are non-crystalline.

- They are macromolecules.

- They are not sweet

Uses of starch

Ø Provides the body with energy

Ø It is the food reserve in plant. It is the stored form of carbohydrate in plant

Procedures

a. Measure 2ml of the prepared starch solution in a test tube

b. Add 2 drops of iodine solution in a test tube containing the solution of starch

c. Shake it thoroughly

d. Observe the color of the mixture

e. If starch is present, the mixture will turn into blue black (dark blue)

f. If starch is absent, the mixture will retain the brown color of iodine solution

B. Lipids

Lipids are compounds of carbon, hydrogen and oxygen. They are insoluble in water

Ø There are two forms of lipids which are fats and oil. Fats are in solid form while oils are in liquid form at room temperature (250).

Ø Natural sources of lipids include sunflower, coconuts, avocado, groundnuts and fat from animal meat.

Ø The chemical regent used in testing Lipids is Sudan III solution

Ø White paper can also be used

Properties of lipids

Ø They are insoluble in water

Ø They are soluble in organic solvents such as alcohol, chloroform and ether.

Ø When oil is shaken in water, the oil breaks down into droplets which disperse in water. After few minutes water and oil separates into two layers.

Ø When water is added to a lipid that has dissolved in an organic solvent a white milky suspension is formed. This is an emulsion.

Ø When fats rubbed against paper, the paper became translucent. When the paper is dipped in ether, translucent disappears because the oil dissolves in ether.

Ø In mixtures of lipid and water, the lipid separates and moves to the top. When shaken with Sudan III solution, this lipid absorbs the dye of Sudan III solution, turns red, and produces a "red ring" at the top of the test tube.

Stained lipids globules will float on the top of water because they are less dense then water. This is the basis for testing lipids by using Sudan (III) solution.

Uses of lipids

Ø They are source of energy. They can be broken down during respiration process to release energy.

Ø Fat adipose tissues below the skin insulate the body against heat loss.

Ø Lipids act as a source of metabolic water when fats and oils are oxidized. This is an alternative source of water for the animal living in desert area like camel.

Ø Fats deposited around the major organs such as kidney, liver and heart protect those organs and they act as shock absorbers.

Ø They form major structural component of the cell membrane. For example phospholipid is a special type of lipid which is a major component of cell membrane.

Ø They are medium for storing fat soluble vitamins like vitamins A, D, E and K

Procedures

a. Measure 2ml of a given solution in a test tube

b. Add 3 drops of Sudan (III) solution then shake the content vigorously and let it settle for five minutes

c. Observe the color changes

d. If lipid is present a red ring will be formed on the top of the solution

e. If lipid is absent the solution will form a homogenous red mixture with Sudan (III) solution

C. Protein (Biuret test)

Proteins are long chains of amino acid. They are made up of carbon, hydrogen, oxygen, and nitrogen. Some proteins also contain Sulphur and phosphorus

Natural sources of protein are categorized into plants, animal products and fungi.

Ø Meat, fish eggs and milk are animal products

Ø Mushroom and yeast are fungi proteins

Ø Beans, coconut and ground nuts are proteins from plants Chemicals used to test protein are

Ø Sodium hydroxide solution (dil NaOH)

Ø Copper (II) Sulphate solution (1% CuSO4)

Properties of protein

Ø They are insoluble in water.

Ø They coagulate on heating. This means that small particles of protein clump together to form bigger particles when a mixture of protein and water is heated.

Ø Protein reacts with sodium hydroxide and copper sulphate to produce violet colour/ purple clour. This is called biuret test.

Note the following during testing of protein

Ø Sodium hydroxide is used to provide alkaline medium for the copper sulphate to react with nitrogen atoms of amino acids.

Ø The purple colour formed during the test of protein is the result of a complex between four nitrogen atoms in the peptide bonds and the copper (II) ion (Cu2+) of Copper sulphate solution.

Uses of protein

Ø They used for growth and repair of worn out body tissues. The protein we eat are used to make new cells which will make tissues to replace those which are worn out.

Ø They provide body protection and defence against disease. For example protein make antibodies which provide the body with immunity.

Ø They can be used to provide energy when the body lacks carbohydrate and fats. This happen during starvation and when the person falls sick.

Ø They form the structural components to various materials such as nails, hair and muscle fibres.

Ø They are required for the formation of enzymes, hormones, and haemoglobin.

Ø They play role in clotting of blood. This is because the fibrinogen which control blood clotting is protein in nature.

Ø They transport oxygen in the blood. This is because the hemoglobin which transport oxygen is protein in nature.

Procedures

a. Measure 2ml of the given solution in a test tube

b. Add 2ml of sodium hydroxide followed by 2 drops of cooper (II) sulphate drop by drop. Shake after each drop

c. Observe the color changes

d. The appearance of purple color indicates the presence of protein

e. Retention of the blue color of cooper (II) sulphate indicate the absence of protein

D. Reducing sugar

Reducing sugars are based units of all carbohydrates which are easily utilized by the body tissues.

Ø The natural sources of reducing sugar include germinating cereals like maize, millet, onion, tomato, all sweet ripening fruits, honey and milk

Ø Glucose and Maltose are example of reducing sugar

Properties of reducing sugar

Ø They are soluble in water

Ø They have sweet taste. They form sweet tasting solutions.

Ø They are crystalline. They can form crystals. - They are small molecule.

Ø They are reducing sugar. This is because the Benedict’s solution which contain copper (II) sulphate when is mixed with reducing sugar, the copper (II) ions of copper (II) sulphate will be reduced to copper (I) ions which form a brick red precipitate of copper (I) oxide.

This for form basis for testing reducing sugar.

Uses of reducing sugar

Ø It provides the body with energy. For example glucose is the most common respiratory which is oxidized during respiration to release energy.

Ø Play role in synthesis of disaccharides. For example when two molecule of glucose are combined through condensation reaction, maltose is formed.

Ø They are used is synthesis of polysaccharides such as glycogen. Glucose is particularly important in this role.

Procedures

a) Measure 2ml a solution put it in the test tube

b) Add 2ml of Benedict’s solution to the solution

c) Heat the mixture to boil

d) Observe the color change

e) If reducing sugar is present in the food sample, the mixture will experience a series of color change from blue to green to yellow then orange and finally to brick red, this depends with the quantity of reducing sugar present in the solution, brick red color indicates the presence of large quantity of reducing sugar

f) If reducing sugar is absent the solution will be of either blue or green color

E. Non-reducing sugar

Ø Non-reducing sugar is component of carbohydrate formed when two molecules of reducing sugar are condensed and release a molecule of water. Natural sources of non- reducing sugar include sugarcane, beetroot, malt and unripen fruits

Ø Chemical reagents used when testing non-reducing sugar are

· Dilute hydrochloric acid (dil HCl)

· Sodium hydroxide solution (NaOH) and

· Benedict’s solution.

Properties of non-reducing sugar

Ø They have sweet taste. They form sweet tasting solutions.

Ø They are crystalline. They can form crystals. - They are small molecule.

Ø They are called non-reducing sugar because they cannot reduce copper sulphate of Benedict’s solution.

Ø Note the following during testing of non-reducing sugar :-

Dilute hydrochloric acid is used to break down (hydrolyze) non-reducing sugars to reducing sugars/converting complex sugar to simple sugar

Sodium hydroxide is used to neutralize the dilute hydrochloric acid.

Uses of non-reducing sugar

They provide the body with energy

Procedures

a) Measure 2ml of a given solution and put in test tube

b) Add 1ml of dil hydrochloric acid, shake it then boil the mixture and cool it.

c) Add 1ml of sodium hydroxide solution to neutralize the acid

d) Add 2ml Benedict’s solution then boil the mixture

e) Observe the color change

f) If non-reducing sugar is present, the color of the mixture will pass through the series of color from blue to green to yellow and finally to brick red

g) If non-reducing sugar is absent in the solution it will retain the blue color of benedict’s solution or turn to green

HOW TO WRITE A REPORT

Principles of writing the food test report

Ø The report should be presented in a tabular form

Ø It must be written in a reported form (passive speech)

Ø Solutions and reagents must be quantified, e.g 2ml or 2 drops and not few drops or little amount of solution

Ø Commanding language like add, put should be avoided

Sample of the report for the provided solution V

Test for	Procedures	Observation	Inference
Starch	To 2ml of	The mixture	Starch was
	solution V in a	turned into blue	present
	test tube, 2	black
	drops of	The solution	Starch was
	iodine solution	retained the	absent
	were added	color of iodine
	then shaken	solution
Lipids	To 2ml of	A red ring was	Lipids was
	solution V in a	formed on the	present
	test tube 3	top of solution
	drops of	V
	Sudan (III)	Solution V	Lipids was
	solution were	retained the	absent

	added then shaken	color of Sudan (III) solution
Protein	In a test tube	The mixture	Protein was
	containing 2ml	turned in	present
	of solution V	purple
	2ml of sodium hydroxide were added followed by 2 drops of 1% Cooper (II)
		The mixture retained the blue color of cooper (II) sulphate	Protein was absent
	sulphate
	solution
	dropwise
	while shaking
	after each drop
Reducing	To 2ml of	A series of	Reducing
sugar	solution V in a	color change	sugar was
	test tube, 2ml	was observed	present
	of Benedict’s	in the mixture
	solution were	from blue to
	added then	green to yellow
	boiled	and finally to
		brick red
		The solution	Reducing
		retained the	sugar was
		blue color of	absent
		Benedict’s
		solution

Non-	To 2ml of	The series of	Non reducing
reducing	solution V in a	color change	sugar was
sugar	test tube 1ml	was observed	present
	of dil	in the mixture
	hydrochloric	form blue to
	acid was	green to yellow
	added shaken	and finally to
	then boiled	brick red
	and cooled.	The solution	Non reducing
	1ml of Sodium	retained the	sugar was
	hydroxide was	blue color of	absent
	added	Benedict’s
	followed by	solution
	2ml of
	Benedict’s
	solution and
	the mixture
	was re-boiled

ii. Preparation of solution

You can be provided with a specimen and then asked to prepare a solution by yourself then conduct the food test

Ø The procedure of preparing the solution should be included in the reported and they should be written in the reported speech (passive voice)

Ø Indicate each procedure that is taken while preparing a solution

THE HUMAN DIGESTIVE SYSTEM

The table summarizing the digestion process

Part of th e alimentar y canal (Site of action)	pH medium (optimu m pH of the substrat e)	Source of enzyme	Digestive juice (secretion)	Enzyme	Food digested	Produ cts of digest ion
Mouth	Alkalin e	Salivary gland	Saliva	Salivary amylase (ptyalin)	Starch	Malto se
Stomach	Acidic	Gastric gland	Gastric juice	Pepsin	Protein	Pepti des
Stomach	Acidic	Gastric gland	Gastric juice	Rennin	Soluble milk protein (caseino gens)	Insol uble milk protei n (casei n)
Duodenu m	Alkalin e	Pancreati c gland	Pancreatic juice	Pancreatic amylase	Starch	Malto se
				Pancreatic lipase	Lipids	Fatty acids and glyce rol
				Trypsin	Protein	Pepti des
Small intestine( ileum )	Alkalin e	Intestinal wall	Intestinal juice (Succus entericus)	Erepsin (peptidase)	Peptide s	Amin o acids
				Maltase	Maltose	Gluco se
				Sucrase	Sucrose	Gluco se and

Fruct ose

Lactase

Lactose

Gluco se and Galac

tose

Lipase

Lipids

Fatty acids and

glyce rol

Adaptations of the ileum for digestion

i. It has secretory glands which produce digestive enzymes.

ii.It is connected to the liver by the bile duct. The bile duct enables bile to reach the ileum.

iii. The ileum has mucus-secreting gland to ensure a constant supply of mucus.

Adaptations of the ileum for absorption

i. The lining of the ileum has finger-like projections called villi. On the villi are even smaller projections called microvilli. These structures increase the surface area for the absorption of food.

ii. The ileum is very long (about six metres). It therefore has a large surface area for the absorption of soluble products of digestion.

iii. The villi have a large network of blood capillaries. These capillaries transport absorbed food to all parts of the body.

iv. The inner lining of the ileum is folded. This increases the surface area that is in contact with food.

v. The lining of the ileum is only one cell thick. Thus, the digested food diffuses through a short distance into the capillaries.

PHOTOSYNTHESIS

What is photosynthesis

It is the process whereby green plants make their own food using water, carbon dioxide and energy from the sun

Balanced chemical equation for photosynthesis

Chlorophyll

6CO2 +12H2O C6H12O6 + 6H2O + 6O2

Sunlight

Testing for starch

Plants are living things that are able to make their own food (glucose) and store it in form of starch

Iodine solution and starch form blue black color when they mix. The test for starch therefore is to add iodine solution in a leaf to see if it goes to blue black, the leaf must be treated as follows

1. Heat some water to boiling point in a beaker

2. Use forceps to dip a leaf in hot water for 30sec. this kills the cytoplasm and denatures the enzymes and make the leaf more permeable to iodine solution.

3. Remove the leaf from the leaf from the beaker

4. Push the leaf to the bottom of the test tube and cover it with alcohol (ethanol). Place the tube in hot water for alcohol to boil and dissolve out most of the chlorophyll. This makes colour change with iodine easier to see

5. Remove the leaf from the test tube and dip it once more into the hot water to soften it

6. Spread the decolorized leaf on a white tile and drop iodine solution onto it. The parts containing starch will turn into blue black and those parts with starch will stain brown colour of iodine

Sample question

You have been provided with a variegated leaf and iodine solution. Carefully follow the instruction given below

a) Heat some water in a beaker to boiling and then turn off the source of heat

b) Use forceps to dip the leaf in hot water for 1 minute

c) Then push the leaf into bottom of the test tube and cover it with ethanol.

d) Place the tube in hot water until the alcohol boils together with the leaf.

e) Remove the leaf from the test tube containing ethanol and deep it into hot water

f) Spread the decolorized leaf on a white tile and pour few drops of iodine solution on it

Questions

i. What as the aim of the experiment?

ii. Why was the leaf dipped in hot water for 1 minute?

iii. Give the reason why the leaf was boiled in ethanol.

iv. Why was the leaf dipped in hot water again?

v. Give the interpretation of the result observed when few drops of iodine solution were poured onto the decolorized leaf

vi. Mention the physiological process investigated in the experiment.

vii. Draw a well label the diagram of a leaf as it appeared before the experiment and after the iodine solution was added

Answers

i. The aim of the experiment was to test if the leaf contain starch.

ii. The leaf was dipped for 1minute in hot water so as to stop the reaction taking place in the leaf.

iii. The leaf was boiled again in methanol to dissolve the chlorophyll present in it.

iv. The leaf was then dipped in hot water so as to remove alcohol and soften it.

v. When few drops of iodine solution were poured on the decolorized leaf, blue black colour occurred in some parts of the leaf. This shows the presence of starch.

vi. The physiological process investigated in the experiment was photosynthesis

Diagram of a leaf before and after the experiment.

Before experiment After experiment

3 GROWTH

1Seed germination

Seed germination is the process by which plant grows from the seed.

Parts of the seed

The seed consists of the following parts

a. An embryo: this part consists of a radicle that develops into a shoot after germination

b. A seed coat(testa):it is a protective layer surrounding a seed

c. Cotyledons: this part grows to form the first embryonic leaves after germination. It also stores and provides food for young plants.

d. Micropyle: This is a pore through which water enters the seed during germination

e. Hilum: This is a scar that shows the seed’s point of attachment to the ovary wall.

Changes which occur during seed germination

During germination, physical and chemical changes occur in a seed. The physical changes include

Ø Swelling of the seed after absorption of water through the micropyle.

Ø The water absorbed by the seed softens the seed coat and activates enzymes in the cotyledons.

Ø This process is followed by the bursting of the seed coat and the emergence of the radicle and plumule.

Ø The radicle is the one that forms a primary root and the plumule gives rise to a shoot.

Ø The radicle continues to elongate and give rise to many side roots.

Conditions necessary for seed germination

For a seed to germinate, it requires certain conditions. These conditions include the following:

Water

Germination occurs when a seed is supplied with water. A seed absorbs water through the micropyle. Water plays an important role during seed germination. When a seed absorbs water, the embryo cells enlarge due to pressure.

Such action leads to the rapture of the seed coat. Water softens the seed coat, hence increases seed permeability. Water also activates enzymes necessary for seed germination and growth.

Oxygen gas

Oxygen gas is necessary for aerobic respiration to generate energy that is required for the growth of the embryo of a seed.

Temperature

Seeds need the optimum temperature to germinate. The seed of each plant species has its optimum temperature for germination. Temperature is essential for the activation of enzymatic reactions during respiration.

Enzymes and hormones

The viability of seeds depends on the presence of the relevant enzymes and hormones in the required amounts. These help to break seed dormancy and catalyze all metabolic activities associated with the process of germination

Types of seed germination

There are two types of seed germination

i. Epigeal germination

ii. Hypogeal germination

i. Epigeal germination

This is the type of germination in which the cotyledons of the seed are pushed above the ground.

This type of germination is seen in many dicotyledonous plants, such as pea, beans, sunflower, castor, and bean.

ii. Hypogeal germination

Hypogeal germination is a type of germination in which the cotyledons remain underground. It occurs in plants such as maize, pigeon peas, wheat, etc.

4 TRANSPORTATION OF MATERIALS IN LIVING THINGS

4.1. Osmosis

This is the movement of water molecules from a region of higher concentration to a region of lower concentration through a semi-permeable membrane.

A partially-permeable membrane is a membrane that allows small particles such as water molecules to pass through it, but not larger particles such as sugar molecules and ions from salts. Examples of semi-permeable membranes are cell membranes and a pig’s bladder.

For osmosis to take place there must be:

1. Two solutions with different concentrations; and

2. A partially permeable membrane to separate them.

Aim of the experiment: To demonstrate the process of osmosis using potato cubes

Materials: Three raw potatoes, sugar solution, water and beakers or dishes

Procedures

1. Boil one of the potatoes (boiling kills the cells).

2. Cut each potato in half and make a shallow hole in each half

3. Place each potato half in a beaker or dish that has water. The water should not cover the potato.

4. Put some sugar solution in the shallow hole in the one raw potato and the boiled potato. Leave the other potato empty. Label the set-ups (a),(b) and (c)

5. Mark the level of water in each beaker or dishes

6. Leave the setups undisturbed overnight

Observation

Effects of osmosis in living organisms

Osmosis and animal cells

Ø When animal cell is placed in hypotonic solution, it absorbs water. If it remains in the solution for a long time, it absorbs excess water and swell and finally bursts (haemolysis) due to the absence of cell wall that exert pressure of the excess water

Ø When animal cell is placed in hypertonic solution, it loses water. If it remains in the solution for a long time, it will lose more water and finally shrink and shrive (crenation).

Osmosis is important for the reabsorption of water in the colon and the kidneys. This helps to maintain the body’s water balance.

Osmosis in plant cell

Ø In an isotonic solution, plant cells neither lose nor gain water.

Ø In a hypotonic solution, plant cells absorb water, causing the cell membrane to push against the cell wall. The cell is then said to be turgid.

It does not burst because the cell membrane exerts pressure on the cell wall which restricts additional intake of water. Turgidity helps plants to maintain their shape.

Ø In a hypertonic solution, plant cells lose water. This causes the vacuole to shrink and the surface of the cell membrane to pull away from the cell wall, making the cell flaccid.

Such a cell is said to be plasmolyzed and the process is called plasmolysis

If a plasmolyzed cell is placed in a hypotonic solution, it absorbs water and becomes turgid

Osmosis is important for the absorption of water by plant roots. Opening and closing of stomata also depend on osmosis.

When guard cells absorb water the stomata open and when they lose water the stomata close.

Osmosis in unicellular organisms

Unicellular organisms that live in fresh water, for example amoeba and euglena, are hypertonic to their surrounding so water enters the organisms by osmosis.

These organisms have a contractile vacuole. The contractile vacuole collects the excess water and removes it from the cell. This prevents the cell from bursting.

4.2. Diffusion

Experiment: Demonstrating Diffusion using Potassium Permanganate Crystals

Materials:

i. Glass beaker or clear glass container

ii. Potassium permanganate crystals

iii. Water

iv. Stirring rod or glass rod

v. Stopwatch or timer

vi. Paper or cardboard

Procedure:

1. Fill the glass beaker or container with water, about two- thirds full.

2. Add a few potassium permanganate crystals to the water. The crystals will slowly dissolve, turning the water purple.

3. Use the stirring rod to gently stir the water and potassium permanganate mixture.

4. After stirring, observe the initial distribution of the purple color in the water.

Questions to Explore:

1. What happens when potassium permanganate crystals are added to water?

2. Why does the water turn purple when potassium permanganate is added?

3. Describe the initial distribution of the purple color in the water after stirring.

4. What do you think will happen to the purple color in the water over time? Why?

5. How does the purple color spread throughout the water? What process is responsible for this movement?

6. What do you notice about the movement of the purple color particles in the water? Is it uniform, or does it show any specific pattern?

7. How can you explain the process responsible for the spreading of the purple color in the water?

8. Does the movement of the purple color particles depend on the presence of an external force, like stirring? Why or why not?

9. What factors do you think can affect the rate of color spreading in the water? How can you design an experiment to test this?

10. Can you compare the diffusion process observed here to any natural processes you know of? How are they similar or different?

Factors affecting the rate of Diffusion

i. Concentration gradient; A huge difference between the concentration of the molecules in two regions leads to a faster rate of diffusion

ii. Surface area to volume ration; the higher the ratio the greater the rate of diffusion

iii. Temperature; increase in temperature increases the rate of diffusion and decrease in temperature decreases the rate of diffusion

iv. Thickness of the membrane; thin membrane enhances the higher rate of diffusion than the thick membrane

v. Size of molecules; small and light molecules diffuses faster than large and heavy molecules

Some important processes that involve diffusion are;

Ø gaseous exchange in the lungs of animals and in the leaves of plants,

Ø absorption of digested food in the ileum,

Ø remove of water materials from cells

Ø absorption of nutrients and oxygen into cells.

5. REPRODUCTION

5.1. Reproduction in flowering plants

Flowering plants or angiosperms reproduce sexually, Flowering plants have specialized structures called the flowers, which is used for the reproduction process.

HIBISCUS FLOWER

A flower comprises of the following parts PEDICEL

It is a flower stalk attached to the plant. It is where flower develops. If it is branched so as to bear many flowers each branch is called radical.

RECEPTACLE

It is the top of the flower stalk ‘pedicel to which other parts are attached.

CALYX/SEPAL

It is the outermost ring of floral leaves. Are usually great and protect the inner floral structure when the flower is not open. Some species of plants have flowers with rings of sepals. The outermost ring is called the epicalyx

COROLLA

This is a ring of petals on a flower. In some plants the petals are brightly colored. They may fuse to form corolla tube.

STAMEN

This is the male reproductive organs. It consists of filament on top with a head of filament called anther The anther contains pollen grains inside. In the hibiscus flower there are many stamens and filaments which join to forma stamina tube, which is connected to the receptacle.

CARPEL

This is the female reproductive organ, it consists of three parts called ovary, style and stigma - Ovary contains eggs/ stigma.

- Style is a tube connected to the ovary.

Dissection of a Flower

Identify the relevant flower by assessing the floral parts and location of the following in the whole flower:

Ø sepals forming the calyx;

Ø receptacle is the swollen part below the calyx;

Ø flower stalk (pedicel);

Ø petals that form a corolla;

Ø stamens with anthers and filaments; and pistil with stigma, style and ovary.

(a) Dissection to half flower

(i) Count the number of sepals, petals and stigma.

(ii) Cut the flower longitudinally into half and separate it into two halves.

(iii) Use the hand lens to observe the sepals, styles, petals, stamen, stigma, ovary and the ovules.

(b) Dissection to display carpel

(i) Use forceps to cut and make a small opening between the two sepals, then use hand to peel the calyx completely from the flower.

(ii) Detach the petals by pulling each one downwards towards the receptacle until the entire corolla is removed from the flower.

(iii) Use forceps to cut and make a small opening at the base of the staminal tube, then expose the ovary with your finger nails by pilling off the staminal tube of the flower around the ovary.

(iv) Use needle to cut at the base of the staminal tube, then extend the incision to the base of the stigma. Care must be taken not to damage the ovary and the style under it.

(v) Repeat the cuttings as much as possible, and then pull apart the strands to completely remove the staminal tube from the flower.

(vi) Look at the flower you will see stigma, style and ovary collectively known as the carpel.

(vii) Observe the ovary, stigma, and style of your flower with a magnifying glass.

(c) Dissection to display stamen

(i) Use forceps to cut and make a small opening between the two sepals, then use hand to peel the calyx completely from the flower.

(ii) Detach the petals by pulling each one downwards towards the receptacle until the entire corolla is removed from the flower.

(iii) Detach the filament and use the hand lens to observe anther and filament.

5. MOVEMENT

Rib Bone:

Distinctive characteristics of rib bones

1. Curved Shape: They possess a unique curved or arc-shaped structure.

2. Pairs: They are typically found in pairs on both sides of the vertebral column.

3. Articulation Points: They have articulation points at one end for attachment to the thoracic vertebrae and costal cartilages at the other end, often connected to the sternum or adjacent ribs.

4. Flat and Thin: They are flat and relatively thin bones, in contrast to cylindrical long bones.

5. Ridges and Grooves: They display ridges and grooves on their outer surface, which serve as muscle attachment sites.

6. Size and Length: They are relatively long bones compared to some others in the skeleton.

7. Position in the Skeleton: They are located in the thoracic region, extending from the spine to the anterior chest.

8. Countable Pairs:They exist in pairs, with humans typically having 12 pairs (24 ribs in total).

Functions of Rib Bones:

1. Protection: Rib bones protect vital organs in the chest cavity, including the heart and lungs, from external impacts.

2. Support: They provide structural support to the chest, helping maintain its shape and integrity.

3. Attachment for Muscles: Rib bones serve as attachment points for various muscles, including those involved in breathing and chest movement.

4. Respiratory Muscle Attachment: Muscles such as the intercostal muscles attach to the ribs and play a direct role in expanding and contracting the chest during breathing.

5. Movement Facilitation: They assist in the flexibility and mobility of the chest wall during inhalation and exhalation.

6. Contribution to Posture: Rib bones contribute to maintaining an upright posture and stability of the upper body.

Contribution of the rib bone to Respiratory Processes:

1. Expansion of Chest: During inhalation, the contraction of the diaphragm and intercostal muscles causes the rib cage to expand, elevating the rib bones.

2. Increased Thoracic Volume: The upward and outward movement of rib bones increases the volume of the thoracic cavity.

3. Pressure Changes: As thoracic volume increases, the pressure inside the chest decreases, creating a pressure gradient for air to flow into the lungs.

4. Lung Expansion: The expansion of rib bones allows the lungs to expand as well, drawing air into the alveoli.

5. Exhalation: During exhalation, the relaxation of the muscles lowers the rib cage, reducing thoracic volume and increasing pressure, leading to the expulsion of air from the lungs.

6. Efficient Breathing: The coordinated movement of rib bones and associated muscles ensures efficient inhalation and exhalation, facilitating the exchange of oxygen and carbon dioxide in the respiratory process.

Articulation:

Describe how rib bones articulate with the thoracic vertebrae and the sternum.

Thoracic Vertebrae Articulation:

Ø The posterior or dorsal end of each rib bone articulates with a corresponding thoracic vertebrae in the vertebral column.

Ø There are 12 pairs of ribs in humans, and each rib bone attaches to the vertebral column at a specific thoracic vertebra. For example, the first rib attaches to the first thoracic vertebra (T1), the second rib to the second thoracic vertebra (T2), and so on.

Ø The articulation point on the rib bone includes the head of the rib, which has facets that fit into the costal facets on the vertebral bodies and transverse processes of the thoracic vertebrae.

Ø These articulations allow for the flexibility and mobility of the rib cage during respiration.

Sternum Articulation:

Ø The anterior or ventral end of most rib bones articulates with the sternum (breastbone).

Ø The attachment to the sternum is via costal cartilages, which are flexible cartilaginous extensions at the anterior end of each rib.

Ø The first seven pairs of ribs (true ribs) have direct cartilaginous connections to the sternum, making them "vertebrosternal" ribs. The cartilages of these ribs connect directly to the sternum.

Ø The next three pairs (false ribs) have indirect connections to the sternum, with their cartilages either attaching to the cartilage of the rib just above or joining together before attaching to the sternum.

Ø The last two pairs (floating ribs) have no direct attachment to the sternum and terminate freely in the abdominal muscles.

Types of Ribs:

Explain the differences between true ribs, false ribs, and floating ribs, and how they are numbered.

True Ribs, False Ribs, and Floating Ribs differ in their attachment to the sternum and how they are numbered:

True Ribs

a. Attach directly to the sternum via individual costal cartilages.

b. Numbered as the first seven pairs (ribs 1-7).

c. Provide structural support and protection to the chest cavity.

False Ribs

a. Indirectly attach to the sternum via shared or connecting cartilages.

b. Include pairs 8-10 (ribs 8-10).

c. Ribs 8-9 have their cartilages attached to the cartilage of the rib just above.

d. Rib 10 has its cartilage that attaches to the cartilage of the rib just above and often joins with rib 9's cartilage.

e. Offer less direct support to the sternum but contribute to chest wall integrity.

Floating Ribs

a. Lack direct attachment to the sternum.

b. Comprise the last two pairs, ribs 11 and 12.

c. Their costal cartilages do not connect to the sternum or to other ribs.

d. Provide minimal structural support but protect the kidneys and flank area.

Tibia and Fibula:

Differentiation:

How can you distinguish between the tibia and fibula when examining these bones?
Tibia:

a. Larger and stronger of the two leg bones.

b. Located on the inner side (medial) of the lower leg.

c. Proximal (upper) end forms the medial condyle, which articulates with the femur.

d. Distal (lower) end forms the medial malleolus, which is the inner ankle bone.

e. Weight-bearing bone of the lower leg.

Fibula:

a. Slimmer and more delicate compared to the tibia.

b. Located on the outer side (lateral) of the lower leg.

c. Proximal end articulates with the tibia but doesn't bear significant weight.

d. Distal end forms the lateral malleolus, which is the outer ankle bone.

e. Serves as an attachment point for muscles and ligaments but doesn't bear as much weight as the tibia.

Articulation:

Describe how the tibia articulates with the femur at the knee joint and with the fibula.

The tibia articulates with the femur at the knee joint and with the fibula at two distinct joints, the proximal and distal tibiofibular joints:

Tibia Articulation with the Fibula:

Proximal Tibiofibular Joint:

a. At the proximal (upper) end of the tibia and fibula, there is a synovial joint known as the proximal tibiofibular joint.

b. Here, the head of the fibula articulates with a facet on the lateral aspect of the tibia.

c. The joint provides minimal movement and serves mainly for stability.

Distal Tibiofibular Joint (Syndesmosis)

a. The distal (lower) ends of the tibia and fibula are connected by strong ligaments, forming a fibrous joint called the distal tibiofibular joint or syndesmosis.

b. Unlike the proximal joint, the distal tibiofibular joint allows for little to no movement and primarily serves as a point of stability.

c. This joint is crucial for maintaining the alignment of the tibia and fibula in the lower leg and for stability of the ankle joint.

Femur:

This is a long bone on the upper part of the hind limb (on the thigh region)

· The head of femur fits in the pelvic girdle to form hip joint

· It articulates with tibia at lower end to form knee joint

· It provides surface for the attachment of leg muscles and it supports the thigh.

Functions of femur

(i) Femur provides the surface area for the attachment of leg muscles

(ii) It provides the site for articulation with the pelvic girdle

(iii) It supports the thigh.

Adaptations of Femur

(i) It is long to provide the surface area for attachment of thigh muscles

(ii) It has a rounded head which articulates with acetabulum of pelvic girdle to allow flexible movement of the leg

(iii) It has condyles for articulation with patella to allow movement in one plane.

Articulation:

Briefly explain the femur articulation

The femur, the thigh bone, articulates with two major joints in the human body:

1. Hip Joint

Ø The proximal (upper) end of the femur articulates with the acetabulum, which is a concave socket in the hip bone (part of the pelvis).

Ø This ball-and-socket joint allows for a wide range of motion, including flexion (bending the hip), extension (straightening the hip), abduction (moving the thigh away from the midline), adduction (moving the thigh toward the midline), and rotation of the thigh.

Ø The articulation between the femoral head and the acetabulum is stabilized by ligaments and muscles, providing both mobility and stability to the hip joint.

2. Knee Joint

Ø The distal (lower) end of the femur articulates with the tibia and patella (kneecap) to form the knee joint.

Ø This hinge joint allows primarily for flexion (bending) and extension (straightening) of the lower leg. The patella articulates with the femur and aids in extending the knee.

Ø The femoral condyles, located at the distal end of the femur, fit into corresponding tibial condyles to create the knee joint.

Ø Ligaments, including the anterior and posterior cruciate ligaments and the medial and lateral collateral ligaments, provide stability to the knee joint.

Radius and Ulna:

Differentiation:

How can you distinguish between the radius and ulna when examining these bones?

You can distinguish between the radius and ulna when examining these bones by considering the following features:

Radius:

Ø Location: The radius is located on the lateral (thumb) side of the forearm when the palm is facing upward

Ø Shape: It is relatively straight and slender in shape.

Ø Length: The radius is usually shorter than the ulna.

Ø Proximal End: The proximal (upper) end of the radius has a round head that articulates with the capitulum of the humerus, forming the radiocarpal joint (wrist joint).

Ø Styloid Process: The distal (lower) end of the radius has a pointed styloid process that extends toward the wrist and provides stability to the joint.

Ø Articulation with Ulna: The radius articulates with the ulna at the proximal and distal radioulnar joints, allowing for rotational movements of the forearm.

Ulna:

Ø Location: The ulna is located on the medial (pinky finger) side of the forearm when the palm is facing upward.

Ø Shape: It has a more pronounced curvature, with a longer shaft compared to the radius.

Ø Length: The ulna is usually longer than the radius.

Ø Proximal End:The proximal (upper) end of the ulna has an olecranon process, which forms the bony prominence at the back of the elbow joint. This process fits into the olecranon fossa of the humerus, allowing for the extension of the forearm.

Ø Styloid Process: The distal (lower) end of the ulna has a slightly curved styloid process that contributes to the stability of the wrist joint.

Ø Articulation with Radius:

The ulna articulates with the radius at the proximal and distal radioulnar joints, facilitating forearm rotation.

Functions of Radius and Ulna

(i) They support the carpals, metacarpals and phalanges.

(ii) They provide the surface for attachment of muscles of the arm

Adaptations of Radius and Ulna

(i) They are long to provide the large surface area for attachment of the muscles of the forearm

(ii) Ulna has olecranon process with sigmoid notch for articulation with the trochlea of the humerus to form a hinge joint at the elbow.

(iii) Distal articulating surface is lined with cartilage for articulation with carpals.

Thoracic vertebrae

Ø Are found in the chest region, they are 12 vertebrae. The thoracic vertebrae with the ribs and sternum form the thoracic cage.

Ø The main role of the thoracic cage is to protect the heart, lungs and major blood vessels also plays major role on breath movement

Distinctive Features of Thoracic Vertebrae

(i) They have a long neural spine, usually pointing backwards

(ii) They have circular-shaped neural canals

Functions of Thoracic Vertebrae

Ø They support the ribs by providing articulation.

Adaptations of Thoracic Vertebrae

(i) They have long neural spine which provide large surface area for attachment of back muscles

(ii) They have strong centrum for support of body weight and support vertebral column for attachment with ribs

(iii) They have facets for articulation with the ribs

(iv) They have pre- and post-zygapophysis for articulation with adjacent vertebrae

(v) They have wide neural canal for passage of spinal cord.

Humerus

Humerus is a long bone of the upper arm.

- It has a rounded head which articulates with the glenoid cavity of the scapula forming a ball and socket joint.

- It has two rounded projections near the head called the Greater and Lesser tuberosities.

- Between the greater and lesser tuberosities, there is a depression called Bicipital groove.

- Its lower end articulates with the Radius and Ulna to form a hinge joint at the elbow.

Adaptations of Humerus

(i) Humerus has bicipital groove through which tendons of the biceps muscles pass.

(ii) It is long to provide large surface area for attachment of biceps and triceps muscles

(iii) It has trochlea at the lower end for articulation with forearm to form a hinge joint at the elbow which allows movement in one plane.

Question

1. You have been provided with mammal’s bone A, B, C and S, T, U of fore limb and hind limb. Examine carefully and answer the following questions.

a) Identify each bone A, B, C and S, T, U by their names

b) Mention the bones which are of fore limb and hind limb

c) Give the main function of the bones S, T and U

d) How each bone S, T and U adapted to its function?

e) Name the various joints formed between bone A, B and C

f) Using diagrams show the structures of various bones that you have observed.

g) What are the structural differences between bone B and C?

h) Give any four bones in which red blood cells are formed.

i) What is the name of the softy and fatty tissue inside of the bone S, T and U?

j) What is the name and functions of long protrusion at the end of bone C?

2. You have been provided with bone bones X and Y observe carefully and answer the following questions

a) Give the name of bones provided

b) Give the function of bone X

c) What are the adaptations of bone X to its function?

d) Draw a well labelled diagram of bones X and give the functions of the labelled parts

e) How many pieces of bone Y comprises in the body of mammals?

f) There are three types of bone Y in mammals name them with their meaning

g) Why bone why also known as thoracic ribcage?

h) What are the main functions of bone Y?

ELIMU TZ

BIOLOGY PRACTICAL SUMMARY FOR NECTA EXAM 2023

THE HUMAN DIGESTIVE SYSTEM

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ELIMU TZ

BIOLOGY PRACTICAL SUMMARY FOR NECTA EXAM 2023

THE HUMAN DIGESTIVE SYSTEM

Posted by Elimutz

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Search This Blog

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NECTA FORM SIX RESULTS 2024

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