Science Form 2.docx

Science Form 2- Express Notes 1. a. Sensory organ: Organs to detect stimulus. b. Stimulus: Changes in environment c. The nerves carry information form receptors to spinal cord and the brain, and from brain and spinal cord to muscles and glands 2. Skin: Regulate body temperature, detects touch.

Lie very close to the skin surface to detect even a light pain Sensitive to heat and is able to detect the temperature when it is hotter than usual Lip deep within the skin and can detect forceful pressure against the skin

Detect any light touch and identify the texture of an object

Sensitive to heat and is able to detect the temperature when it is colder than usual

Application: Doctors give injections, Blind people read Braille, Mothers use back of hand to detect the temperature of the milk. Sensitivity of the skin depends on: 3. Sense of smell: Detect the chemicals in air

(a) The distance between the receptors (i.e. no. of receptors) (b) Thickness of epidermis

Structure of Nose:  Upper part of nasal cavity: has many sensory cells  Maximum exposure to the air that enters the nasal cavity

4. Sense of taste Sense of smell and sense of taste  Nasal cavity and the mouth are connected  Chemicals from the food stimulate the taste receptor move to the nasal cavity and stimulate sensory cells in the nose

5. Sense of Hearing Eustachian tube: Balance the pressure on both sides of the eardrum Semicircular canals: Help the body to maintain its balance Stereophonic Hearing: Ability to hear using both ears:  Determine the direction of sound accurately (the ear nearer to the source receives a stronger stimulus/ receives the sound earlier than the other ear- Impulses reach the brain earlier)  Brain interprets these two different impulses

Hearing Defects:  Deafness

- Partial - Total hearing loss

a. Build up of earwax in the auditory canal (Block sound waves)- Temporary hearing loss b. Punctured eardrum c. Cochlea damaged by local infections (Toxins produces- diphtheria/ scarlet fever) d. Sensory cells in cochlea- damaged by exposure to loud sound e. The ossicles in the middle ear fused together (Cannot move freely)- Total hearing loss Correcting hearing transplant a. Warm water- Remove earwax blocking the canal b. Eardrum transplant/ Surgery (Replace using membrane from other parts of the body) c. Hearing aid: The microphone with change the sound waves received into electric signals. Then, the amplifier strengthens the electric signals and changes them into sound energy 6. Sense of Sight and Light Parts help to refract light:  Cornea, lens, Vitreous humour Bright:  Pupil: Smaller (To prevent light enters) Dark:  Pupil: larger (To enable more light)

Short-sightedness  Eye lens too thick  Eyeball to long Long sightedness  Eye lens too thin  Eyeball to short 

Distanced Object:  Ciliary muscles contract  Suspensory ligaments relax Near Object:  Ciliary muscles relax  Suspensory ligaments contract

7. Tropisms: Response of plants to stimulus. a. Phototropism: Movement or growth of plants in response to light b. Geotropism: Growth movement of the tips of shoots and roots of response to gravity c. Hydrotropism: A plant’s growth response to water (*Roots to water is stronger than their response to gravity) d. Nastic movement: Responses of a plant towards touch, light and heat (Not directional, but reversible) e. Thigmotropism: A tropic response in which the stimulus is touch or contract

8. a. Nutrition: The process of providing or obtaining the food necessary for health and growth. b. Nutrients: Substances that provides nourishment essential for growth c. Digestion: the process of breaking down food by mechanical and enzymatic action in the alimentary canal into substances that can be used by the body. d. Balanced diet: A diet consisting all types of nutrients in the right amounts needed by the body e. Calorific value: Quantity of energy produced when one unit mass of food is burn completely f. Defecation: The process of removing feaces from the body g. Assimilation: The absorption and digestion of food or nutrients by the body systems 9. Biodiversity: Variety of living organisms Classification of non-flowering plants  The classification of non-flowering plants is based on  The presence of roots.  The absence of roots.  Based on their seeds - spore bearing and naked seeds.

Algae   



Algae are eukaryotic organisms that have no roots, stems, or leaves but do have chlorophyll and other pigments for carrying out photosynthesis. Algae can be multicellular or unicellular. Unicellular algae occur most frequently in water, especially in plankton. Reproduction in algae occurs in both asexual and sexual forms. Asexual reproduction occurs through the fragmentation of colonial and filamentous algae or by spore formation (as in fungi). Spore formation takes place by mitosis. Binary fission also takes place (as in bacteria). During sexual reproduction, algae form differentiated sex cells that fuse to produce a diploid zygote with two sets of chromosomes. The zygote develops into a sexual spore, which germinates when conditions are favorable to reproduce and reform the haploid organism having a single set of chromosomes. This pattern of reproduction is called alternation of generations.

Conifers    

The Conifers are cone-bearing seed plants with vascular tissue. Most are trees; some are shrubs. All living conifers are woody plants, the great majority being trees. Living conifers are all in the order Pinales. Typical examples include cedars, cypresses, firs, junipers, kauris, larches, pines, redwoods, spruces, and yews. Conifers are of great economic value, and their wood is mainly used for timber and paper making The wood of conifers is known as softwood, though yew wood is actually quite hard. The division Coniferae contains about 700 living species.

Mosses  

They belong to the kingdom of Phylum bryophyta. They are the simplest plants with the absence of true roots and vascular tissues.

   

They have simple stems, leaves and they do not produce flowers, fruits and seeds. They reproduce through spores. They are small green coloured plants, which prepares their own food. They live in damp shady places.

Ferns      

They belong to the kingdom of Phylum pteridophytae. They are the simplest plants with the presence of roots, feathery leaves and underground stems. They have vascular tissues, which helps in the transportation of water, minerals and sugars throughout the plant. They have spore producing organs, which is present at the bottom of the leaves. They are small green coloured plants, which prepares their own food. They live in damp shady places.

10. a. Habitat: A place where an organism lives, provides food, shelter from enemies, protection from bad weather and opportunity for breeding b. Species: Group of living organisms consisting of similar individuals capable of exchanging genes or interbreeding. c. Population: A group of the same species d. Community: The different population of organisms e. Ecosystem: Ecosystem consists of several communities that interact with one another and their non-living environment. 11. a. Competition a.i. Intra-specific competition a.ii. Inter-specific competition b. Prey-predator b. i. Prey: b. ii. Predator c. Symbiosis c. i. Commensalism c. ii. Mutualism c iii. Parasitism 12. Biological control: 13. a. Solute b. Solvent c. Solution 14. a. Dilute solution b. Concentrated solution c. Saturated solution 15. a. Neutralisation

b. Titration