JK-TK/Newdata huggingface dataset:
Image formation and Interpretation
Light rays from an object enter the cornea and are directed onto the lens through the pupil. They are refracted by the cornea and the lens. The latter brings the rays into fine focus. It makes the light rays converge so that an image is focused at a point on the retina. The image on the retina is inverted. This stimulate, the rods and cones on the retina and impulses generated are transmitted through the optic nerve to the brain. The brain interprets the image as upright. Common Eye Defects and their Correction
Short-sightedness (Myopia)
A shortsighted person cannot focus distant objects properly. Light rays from a distant object fall at a point in front of the retina. This may be due to the eyeball being too long. This defect can be corrected using spectacles with concave lenses. The lenses make the light rays diverge before they reach the eye. Long-sightedness (Hypermetropia)
A long-sighted person cannot focus near objects properly. Light rays from the object are not focused on the retina. This may be due to the eyeball being too short. This defect may be corrected by using spectacles with convex lenses which make light rays converge before they reach the eye. Astigmatism
Astigmatism refers to a condition in which the cornea or the lens is uneven, so that images are not focused properly on the retina. This defect can be corrected by wearing spectacles with special cylindrical lenses. Presbyopia is a condition in which light rays from a near object are not focused on the retina. This is caused by hardening or loss of elasticity of lense due to old age. This defect is corrected by wearing convex (converging) lenses. Structure and Functions of Parts of Human Ear
The Mammalian Ear
The mammalian ear performs two major functions:
hearing and detecting changes in the positions of the body to bring about balance and posture. The ear is divided into three sections. The Outer Ear
This consists of:
An outer flap, the pinna which is made up of cartilage. The function of the pinna is to catch and direct sounds. The external auditory canal is a tube through which sound travel. The lining of the tube secretes wax, which traps dust particles and microorganisms. The tympanum is a membrane stretching across the inner end of the external auditory canal. The tympanum vibrates when it is hit by sound waves.
The lining of the tube secretes wax, which traps dust particles and microorganisms. The tympanum is a membrane stretching across the inner end of the external auditory canal. The tympanum vibrates when it is hit by sound waves. The Middle Ear
This is a chamber containing three small bones called the ear ossic1es, the malleus, incus and stapes. The three ossic1es articulate with one another to amplify vibrations. The vibrations are transmitted from the tympanum to the oval window. At the end of the chamber is a membrane called the oval window. When the tympanum vibrates, it causes the ear ossic1es to move forwards and backwards. This causes the oval window to vibrate. The Eustachian tube connects the middle ear to the pharynx. It allows air to get in and out of the middle ear, thus equalising the pressure between the inside and the outside of the tympanum. The Inner Ear
This consists of a series of chambers filled with fluid. It comprises the cochlea and semicircular canals. Cochlea is a coiled tube that occupies a small space and accommodates a large number of sensory cells. The cells are connected to the brain through the auditory nerve. They detect vibrations which lead to hearing. Hearing
The sound waves set the tympanum vibrating and are transformed into vibrations. The vibrations are transmitted to the oval window by the three ossicles. Vibrations of the oval window cause the fluids inside the cochlea tube to vibrate. The membranes inside the cochlea have sensory cells which change the sound vibrations to nerve impulses. These are transmitted to the brain through the auditory nerve. Hearing is perceived in the brain. Balance and posture
The semi-circular canals
There are three semi-circular canals in each ear. They are situated at right angles to each other and each one is sensitive to movement in a different plane. They are filled with fluid and each has a swelling called the ampulla at one end. Inside the ampulla are sensory cells. Balance and posture are detected by these cells. Movement of the head in a given direction causes the fluid to move the hairs on sensory cells. This transmit impulses to the brain through the auditory nerve so that the movement is registered. Defects of the ear
Acute labyrinthitis
This is an inflammation of the middle ear and cochlea. It may lead to deafness.
This transmit impulses to the brain through the auditory nerve so that the movement is registered. Defects of the ear
Acute labyrinthitis
This is an inflammation of the middle ear and cochlea. It may lead to deafness. It can be treated by using certain drugs but sometimes an operation may be necessary. Tinnitis:
This is a sensation of noises in the ear. It is caused among others by accumulation of wax in the ear or use of certain drugs e.g. quinine. Treatment is by removal of wax, stopping use of the causative drug. Vertigo - Giddiness
This is disorientation of body in space - one of the causes is dilation of endolymph. Corrections: Use of appropriate drugs. Deafness. This is inability to hear. It is presented in various degrees in various individuals, some have partial hearing, others are completely deaf. This may be as a result of:
Chronic infection of cochlea. Lack of sensory cells. Excess wax in external auditory canal. Fusion of ear ossicles. Otitis Media
This is the inflammation of middle ear due to build-up of fluid. It is marked by the swelling of tissues surrounding the Eustachian tube due to infection or severe congestion. A strong negative pressure creates a vacuum in the middle ear. Treatment - use of antibiotics or surgery. Practical Activities
To investigate tactic response
Tactic response in fly maggots are investigated using choice chambers(s). Responses to various stimuli are observed e.g. to chemical substances - chemotaxis. On one side of choice chambers is placed beef/fish that has been dried in the sun. On the opposite chambers is placed rotting meat/fish. Ten maggots are placed at the center and choice chamber is covered. After 10 minutes the number of maggots at each end is counted. Most of the maggots have moved to the chamber with rotting meat. Tropisms
Maize or been seeds are soaked and germinated, to the stage when radical and coleoptile/plumule just appear . (about 5 days for beans and seven days for maize). Seedlings with straight radic1es and plumules are used .. Geotropism
The seedlings are placed horizontally on the medium (Soil or vermiculite or saw dust or sand). Observations are done after three days and results recorded.
Seedlings with straight radic1es and plumules are used .. Geotropism
The seedlings are placed horizontally on the medium (Soil or vermiculite or saw dust or sand). Observations are done after three days and results recorded. Phototropism
A potted plant or a young seedling planted in a beaker is kept next to a window which is the only source of light in the laboratory. Alternatively, a dark box may be used. Observations are made after 3-5 days and results recorded. The shoots grow bending towards the same light. Etiolation
Young seedlings are placed in a dark box. It is kept moist but not exposed to light. After two weeks the seedlings are removed and observations made to note the following:
Colour of leaves is yellow. Size of leaves is small
Length of internodes is long
Length of stem elongated long and thin. Other seedlings that were grown in light are observed (as control) and similar measurements taken. They are green in colour with larger leaves, shorter internodes and the stem is shorter and thicker. Those in the dark have smaller yellow leaves, long thing stems with long internodes. (etiolated). Experiment to Determine Distance of the Blind Spot
Students should work in pairs so that one takes measurements while the other observes. A cross and a dot are marked on a white paper . The two points are 6-9 cm apart. The paper is held 50 cm away from the face. Closing the left eye, the paper is slowly moved towards the face as the right eye is fixed on the cross. At 50 cm distance the cross and the dot are seen clearly. As-the paper is moved closer to the face, the dot disappears. The distance at which the dot disappears is measured. This is the distance of the blind spot. When the light rays from the dot are focused on the blind spot it disappears hence the dot is not seen. The Knee Jerk Experiment
Students work in pairs, one student sits on the table, high stool or bench with one leg crossed over the other. The other student chops the crossed knee just below the knee cap with the edge of palm or wooden ruler. It is observed that the crossed knee jerks. This is a spinal reflex. END
Support and Movement in Plants and Animals
Necessity for support and movement
Movement is a characteristic of all living organisms. It enables animals and plants to adjust to their environment.
This is a spinal reflex. END
Support and Movement in Plants and Animals
Necessity for support and movement
Movement is a characteristic of all living organisms. It enables animals and plants to adjust to their environment. Most animals move from place to place but some are sessile (i.e. fixed to the substratum). Majority of plants move only certain parts. However, though not easily observed all living protoplasm shows movement of one type or another. Necessity for support and movement in plants
They enable plants to be held upright to trap maximum light for photosynthesis and gaseous exchange. To hold flowers and fruits in appropriate position for pollination and dispersal respectively. To enable plants to grow to great heights and withstand forces of environment e.g. strong winds. Movement of male gametes to effect fertilisation and ensure perpetuation of a species. Plant parts move in response to certain stimuli in the environment of tropisms. Tissue distribution in Monocotyledonous and Dicotyledonous plants
Vascular bundles are the main support tissues in plants. In monocotyledonous stem they are scattered all over the stem. while in dicotyledonous stem they are found in a ring or rings. In monocots the xylem and phloem alternate around with pith in the centre. In dicots of the xylem forms a star in the centre - there is no pith. Phloem is found in between the arms of xylem. Dicotyledonous plants have cambium which brings about secondary growth resulting in thickening of the stem and root hence providing support. Secondary xylem becomes wood, providing more support to the plant. Role of support tissues in young and old plant
Plants are held upright by strengthening tissues ;
parenchyma,
collenchyma,
sclerenchyma
xylem tissue. Parenchyma and collenchyma are the main support tissues in young plants. Parenchyma –
They are found below the epidermis. They form the bulk of packing tissue within the plant between other tissues . They are tightly packed and turgid they provide support. Collenchyma –
Their cell walls have additional cellulose deposited in the corners. This provides them with extra mechanical strength. Sclerenchyma –
Their cells are dead due to large deposits of lignin on the primary cell wall.
Collenchyma –
Their cell walls have additional cellulose deposited in the corners. This provides them with extra mechanical strength. Sclerenchyma –
Their cells are dead due to large deposits of lignin on the primary cell wall. The lignified wall is thick and inner lumen is small, hence provide support. Sclerenchyma fibres are arranged in elongated and in longitudinal sheets giving extra support. They are found in mature plants. Xylem –
Has two types of specialised cells. Vessels and tracheids. Vessels are thick-walled tubes with lignin deposited in them. They give support and strength to the plant. Tracheids are spindle-shaped cells arranged with ends overlapping. Their walls are lignified. They help to support and strengthen the plant. Plants with weak stems obtain their support in the following ways. Some use thorn or spines to adhere to other plants or objects. Some have twinning stems which grow around objects which they come into contact with. Others use tendrils for support. Tendrils are parts of a stem or leaf that have become modified for twinning around objects when they gain support. In passion fruit and pumpkin, parts of lateral branches are modified to form tendrils. In the morning glory, the leaf is modified into a tendril. Support and Movement in Animals
Necessity for support and movement in animals. Animals move from place to place:
In search of food. To escape from predators. To escape from hostile environment. To look for mates and breeding grounds. The skeleton, which is a support structure helps to maintain the shape of the body. Movement is effected by action of muscles that are attached to the skeleton. Types and Functions of Skeletons
Two main types will be considered. These are exoskeleton and endoskeleton. Exoskeleton
Exoskeleton is hard outer covering of arthropods made up of mainly chitin. Which is secreted by epidermal cells and hardens on secretion. It is strengthened by addition of other substances e.g. tannins and proteins to become hard and rigid. On the joints such as those in the legs the exoskeleton is thin and flexible to allow for movement. Functions of Exoskeleton
Provide support. Attachment of muscles for movement. Protection of delicate organs and tissues. Prevention of water loss. Endoskeleton:
It forms an internal body framework. This is a type of skeleton characteristic of all vertebrates.
Prevention of water loss. Endoskeleton:
It forms an internal body framework. This is a type of skeleton characteristic of all vertebrates. The endoskeleton is made of cartilage, bone or both. It is made up of living tissues and grows steadily as animal grows. Muscles are attached on the skeleton. The muscles are connected to bones by ligaments. Functions
The functions of endoskeleton include support, protection and movement. Locomotion in a finned fish e.g. tilapia. Most of the fishes are streamlined and have backward directed fins to reduce resistance due to water. External features-of Tilapia
Scales tapers towards the back and overlap forwards to provide a smooth surface for a streamlined body. The head is not flexible. This helps the fish to maintain forward thrust. Slimy mucous enables the fish to escape predators and protects the scales from getting wet. The pectoral and pelvic fins are used mainly for steering, ensuring that the fish is balanced. They assist the fish to change direction. The dorsal and anal fins keep the fish upright preventing it from rolling sideways. The caudal or tail fin has a large surface area, and displaces a lot of water when moved sideways creating forward movement of the fish. In order to change position in water the fish uses the swim bladder. When filled with air the relative density of the body is lowered and the fish moves up in the water. When air is expelled, the relative density rises and the fish sinks to a lower level. Swimming action in fish is brought about by contraction of muscle blocks (myotomes). These muscles are antagonistic when those on the left contract, those on the right relax. The muscles are attached to the transverse processes on the vertebra. The vertebra are flexible to allow sideways movement. Mammalian skeleton
The mammalian skeleton is divided into two:
Axial and appendicular. Axial skeleton is made up of the skull and the vertebral column. Appendicular skeleton is made up of the pelvic and pectoral girdles and limbs (hind limb and forelimbs). The Axial Skeleton
This consists of the ;
skull,
the sternum,
ribs,
the vertebral column. The Skull
The skull is made up of cranium and facial bones. The cranium; encloses and protects the brain. It is made up of many bones joined together by immovable joints. The facial bones consists of the upper and lower jaws.
The cranium; encloses and protects the brain. It is made up of many bones joined together by immovable joints. The facial bones consists of the upper and lower jaws. At the posterior end of the cranium are two smooth rounded protuberances, the occipital condyles. These condyles articulate with the atlas vertebra to form a hinge joint, which permits the nodding of the head. Sternum and ribs –
They form the rib-cage. The rib-cage encloses the thoracic cavity protecting delicate organs such as the heart and lungs. The ribs articulate with the vertebral column at the back and the sternum at the front. The Vertebral Column
The vertebral column is made up of bones called vertebrae placed end to end. The vertebrae articulate with one another at the articulating facets. In between one vertebra and another is the cartilaginous material called intervertebal disc. The discs act as shock absorbers and allow for slight movement. Each vertebra consists of a centrum and a neural arch which projects into a neural spine. The neural canal is the cavity enclosed by the centrum and the neural arch. The spinal cord is located inside the canal. The neural spine and other projections e.g. transverse processes serve as points of attachment of muscles. Type and number of vertebrae in human and rabbit
Cervical Vertebrae
These are found in the neck region of a mammal. The distinguishing feature is a pair of verte-braterial canals in the neural arch, through which the blood vessels of the neck pass. Another feature is the structure of the transverse processes. They are flattened out and are known as cervical ribs. The fIrst cervical vertebra is known as the Atlas. It has a large neural canal and no centrum. The second cervical vertebra, is called axis. The other five cervical vertebrae have no specific names. They have the same structure. The cervical vertebrae possess numerous processes for muscle attachment. Thoracic Vertebrae
Each thoracic vertebra has a large centrum ,a large neural canal, neural arch and a long neural spine that projects upwards and backward. There is a pair of prezygapophyses and postzygapophyses for articulation with other vertebra . They have a pair of short transverse process. The thoracic vertebra also articulates with pair of ribs at tubercular and capitular facets.
There is a pair of prezygapophyses and postzygapophyses for articulation with other vertebra . They have a pair of short transverse process. The thoracic vertebra also articulates with pair of ribs at tubercular and capitular facets. Lumbar Vertebrae
Each lumbar vertebra has a large, thick centrum for support of the body. It has a neural spine that projects upwards and forwards. There is a pair of large transverse process that are directed forwards. Above the prezygapophyses lies a pair of processes called metapophyses,
Below postzygapophyses lies the anapophyses. Metapophyses and anapophysis serve for attachment pf muscles of the abdomen. In some mammals, there may be another process on lower side of centrum called hypapophysis also for muscle attachment. Sacral Vertebrae
The sacral vertebrae are fused together to form a rigid bony structure, the sacrum. The centrum of each vertebra is large, but the neural canal is narrow. The neural spine is reduced to a small notch. The transverse processes of the first sacral vertebra are large and wing-like
They are firmly attached to the upper part of the pelvic girdle. Caudal Vertebrae
Human beings have only four of these vertebrae which are fused together to form coccyx. Animals with long tails have many caudal vertebrae. A typical caudal vertebra appears as a solid rectangular mass of bone. The entire bone consists of the centrum only. Appendicular Skeleton
The appendicular skeleton consist of the limbs and their girdles. Bones of Fore-limbs
Pectoral girdle
Pectoral girdle is made of scapula, coracoid and clavicle. A cavity known as glenoid cavity occurs at the apex of the scapula. The humerus of the fore limb fits into this cavity. The clavice is a curved bone connecting the scapular to the sternum. Humerus
Humerus is found in the upper arm. It articulates with the scapula at the glenoid cavity of the pectoral girdle and forms a ball and socket joint. Ulna and radius
These are two bones found in the forearm.
Humerus
Humerus is found in the upper arm. It articulates with the scapula at the glenoid cavity of the pectoral girdle and forms a ball and socket joint. Ulna and radius
These are two bones found in the forearm. The ulna has a projection called olecranon process and a sigmoid notch which articulates with the humerus. Bones of hind limb
Pelvic Girdle
The pelvic girdle consists of two halves fused at the pubic symphysis. Each half is made up of three fused bones:
the ilium,
ischium
pubis. Each half has cup-shaped cavity for the acetabulum for articulation with the head of the femur. Between the ischium and pubis is an opening obturator foramen where spinal nerves, blood vessels and a tough inflexible connective tissues pass. The ilium, ischium and pubis are fused to form the innominate bone. The Femur
The femur is the long bone joining the pelvic girdle and the knee. The head of the femur articulates with acetabulum forming the ball and socket joint at the hip. The femur has a long shaft. At the distal end it has condyles that articulate with the tibia to form a hinge joint at the knee. The patella covers the knee joint and prevents the upward movement of the lower leg. Tibia and Fibula
The tibia is a large bone, and the fibula a smaller bone is fused to it on the distal part. In humans the tibia and fibula are clearly distinguishable. Joints and Movement
Ajoint is a connection between two or more bones. Joints provide articulation between bones making movement possible. However some joints do not allow any movement e.g. the joints, between bones of the skull. Movable joints are of three main types:
Gliding joint
e.g., joints which occur between the vertebrae wrists and ankles. The ends of the bones that make the joint are covered with cartilage. The bones are held together by tough ligaments. Synovial joint
The joint is enclosed by fibrous capsule lined by synovial membrane which secretes synovial fluid into the synovial cavity. The synovial fluid lubricates the joint. They are called synovial joints. They include hinge joint and ball and socket joint. Hinge joint
e.g.