science definitions form 2

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Words

Definition

Sensory organs Stimuli

Organs that detect stimuli Changes that occur in the surroundings Singular: Stimulus The ability of an organism to detect a stimulus The reaction of an organism towards a stimulus Special structures in our sensory organs that are very sensitive to stimuli with nerves attached to them. Electrical messages produced by receptors Interprets nerve impulses and decides how to body should respond by sending out nerve impulses which carry the information to the related effectors Parts of a body that carry out responses The sensory organ that gives us the sense of touch The outer layer of the skin which is made up of dead cells. It has a tough waterproof surface which acts as a protective layer against bacteria. The inner layer of the skin which consists of living cells, blood vessels, sweat glands and nerves. Sensory organ for smell Chemicals present in the air The sensory organ for taste which is sensitive to chemicals in food that gives taste to food. Found in taste buds on the surface of the tongue The sensory organs for sight, which are sensitive to light. Occurs when light bounces off the surface of on object. Light that is reflected in a regular pattern Reflected rays which are scattered in all directions. Enables us to see an object from any angle. Used at home and as rear-view mirror in vehicles Produce a wider scope of view Produce magnified images Made up of two plane mirrors to reflect and change the direction of light A tube made up of mirrors with small pieces of coloured objects. Allow light to pass through The bending of light when it passes from one transparent medium to another of a different density. An imaginary line that is perpendicular to the surface of the medium. The images produced on the retina are blurred. Images formed on the retina are blurred Sees near objects clearly but distant objects are blurred. Eye lens are too thick or eyeballs are too long. Corrected by concave lenses to diverge light. Sees distant objects clearly but near objects are blurred. Eye lenses are too thin or eyeballs are too short. Light from near object is focused behind the retina. Corrected by convex lenses to converge light.

Sense Response Receptors Nerve Impulses Brain Effectors Skin Epidermis Dermis Nose Smell Tongue Taste receptors Ears Reflection of light Regular reflection Irregular/ diffused pattern Plane mirrors Convex mirrors Concave mirrors Periscopes Kaleidoscopes Transparent media Refraction of light Normal Normal vision Defective vision Short-sightedness (myopia) Long-sightedness (hypermetropia)

Astigmatism

Caused by irregular surface of the cornea or lens, or both. Cannot see near or distant objects clearly Corrected with glasses with cylindrical lenses or by wearing special lens, or surgery.

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CassiaFany © Colour-blindness

Presbyopia

Optical illusion Stereoscopic vision Field of stereoscopic vision Monocular vision Sound Echoes Deafness Hearing aid

Stereophonic hearing Tropisms Positive tropism Negative tropism Phototropism Geotropism Hydrotropism Thigmotropism Nastic movements Seismonastic Food

Nutrition Carbohydrates Proteins Kwashiorkor Fats Vitamins Minerals Dietary fibre (Roughage) Food tests Benedict’s test

Cannot see some or all colours. Most of them cannot distinguish between red and green colours. Most sufferers are men. They are due to reduced number of cone cells on the retina/defects in them. Inherited from the mother who is a carrier for the defect and it cannot be corrected. As we grow older, our eye lenses become less elastic. The ciliary body also loses its ability to contract and relax. As a result, images for near and distant objects are blurred. Glasses with bifocal lenses can correct this defect. Occur when what we see is different from the actual situation. The brain cannot interpret the correct image that is reflected on the retina. When both eyes are used to view an object Judge position, size and distance The area where the visual fields of both eyes overlap When one eye is used to view an object A form of energy which is produced by vibrations Reflected sounds Refers to partial or total hearing loss Amplifies sounds. Consists of a microphone, an amplifier and an earphone Hearing with two ears Directional growth responses of plants to external stimuli When part of a plant grows towards the stimulus When part of a plant grows away from the stimulus. The growth movement in plants in response to light The growth movement of plants in response to gravity. The growth movement of plants in response to water The growth movement of plants in response to touch or contact. Non-directional movements of plant parts in response to external stimuli. A nastic movement in response to touch. A collection of chemicals taken into an organism for the following purposes: To provide energy for cellular activities, To provide raw materials for growth and repair of worn-out tissues. The process of making or obtaining food. Food substances consisting of carbon, hydrogen and oxygen in their molecules. Food substances that contain carbon, hydrogen, oxygen and nitrogen. Sulphur and phosphorus are present too. Insufficient protein in a child’s diet Consists of carbon, hydrogen and oxygen. Fats contain less oxygen in proportion to hydrogen. Organic compounds that are required in very small amounts for maintaining good health. Inorganic chemical elements that are needed in small amounts. Consists mainly of cellulose that is indigestible because we do not have enzymes to digest it. Are carried out to find out substances contained in food. A brick-red precipitate indicates presence of glucose.

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CassiaFany © Iodine test Millon’s test Emulsion test Diet Balanced diet Calorific/ Energy value Calorimeter Digestion Physical digestion Chemical digestion Enzymes Digestive enzymes Carbohydrases

Proteases

Hydrochloric acid

Lipases Bolus Peristalsis Gastric juices Chyme Bile

Absorption Villi Defecation Constipation Biological diversity/ biodiversity Classification of organisms Kingdoms

A blue-black colour indicates the presence of starch. A red coagulation indicates the presence of proteins A milky solution indicates the presence of fats. Refers to the food we eat A diet that contains all the seven classes of food in the right amounts. To indicate the energy content of food To measure the energy value of food The process of breaking down large food molecules into smaller soluble molecules that can be readily absorbed by the body. The mechanical breakdown of food by the chewing action of the teeth and the churning action of the stomach. Involves the use of enzymes to break down food substances. Protein substances which act as a catalyst and generally speed up the chemical reactions in our body. Enzymes that break down food substances in the gut Catalyses the breakdown of carbohydrates E.g. Salivary amylase : Starch-maltose Pancreatic amylase : Starch-maltose Maltase : Maltose-glucose Catalyses the breakdown of proteins E.g. Proteases : Proteins-polypeptides/peptones-amino acids Hydrochloric acid Secreted by gastric juice in the gastric glands which: - Kills microorganisms - Provides acidic medium for action of proteases - Stops action of salivary amylase - Converts inactive forms of proteases to active forms Catalyses the breakdown fats and oils E.g. Lipase ; Fats-fatty acids and glycerol Food which is shaped into a round lump by our tongue A wave-like action which is caused by the contraction and relaxation of muscles in the oesophagus. Contain proteases and hydrochloric acid Food which is converted into a semi-fluid liquid A brownish-green liquid, which is produced by the liver, which contains bile salts and bile pigments, which is stored in the gall bladder and released into the duodenum through a tube called the bile duct. The movement of digested food through the walls of the small intestine into the blood capillaries. Increase the surface in contact with digested food. (Singular: Villus) The voiding of faeces through the anus caused by peristaltic contraction of the rectum, aided by contraction of the abdominal muscles. Faeces which become very hard and dry. Refers to the wide variety of organisms on Earth. The sorting of organisms into groups The present classification system divides organisms into five major groups called

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Vertebrates Invertebrates Classes Cold-blooded External fertilisation Internal fertilisation Warm-blooded Flowering plants Non-flowering plants Monocotyledons

Dicotyledons

Herbaceous plants Fibrous roots Tap root Algae Mosses Ferns Conifers

kingdoms: animals, plants, fungi, bacteria and very simple organisms. Animals with backbones Animals without backbones Vertebrates are classified into five smaller groups called classes, which are fish, amphibians, reptiles, birds and mammals. Body temperature changes according to the surrounding temperature. Eggs are fertilised outside the female’s body Eggs are fertilised in the female’s body Body temperature remains constant. Plants that produce flowers Plants that do not produce flowers Flowering plants with one cotyledon in their seeds. Have fibrous roots and parallel veins. Most are herbaceous plants Flowering plants with two cotyledons in their seeds. Have a tap root and network-like veins. Many have woody stems. Plants with non-woody stems Almost the same in length and branch in all directions A main root that grows directly downwards. Many fine lateral roots grow from it. Do not have true stems, roots or leaves. Live in water. Have simple stems and tiny leaves but no true roots. Reproduce through spores produced in capsules. Have stems, leaves and roots. Reproduce through spores produced in capsules on the underside of the leaves. Have stems, roots and needle-like leaves. Reproduce through seeds produced in cones.

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