Idea Transcript
1! Revision Form 3 Biology
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Revision Biology Form 3
Topic 1: Characteristics of Living Things
movement - change place or direction respiration - the breakdown of food to release energy sensitivity - responding to stimuli growth - increasing in size or weight or both reproduction - the perpetuation of a species excretion - removing wastes from the body feeding - the process of taking in or synthesising food in an organism.
MRS GREF Topic 2: The Microscope and The Cells
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A microscope is an instrument that magnifies the image of an object. First you click the low power objective lens into its working position. Ensure that light is entering by looking through the eyepiece lens. Place the specimen on the slide. Add a drop of dye or water, lower the cover slip. 5. Lower the objective lens towards the slide by turning the focusing knobs. 6. Then turn the focusing knobs again to the opposite side to very slowly raising the lens and focusing on the specimen. 7. When you see the specimen under low power, take the observations and turn the objectitve lens to the next higher magnification. 8. When this is done, turn the objective lens to the highest power. 9. The three different powers of the objective lenses that we normally find in school microscopes are x4 , x10 and x40. The eyepiece lens usually has magnification power of x10. 10. To calculate the overall magnification we multiply the eyepiece power x the objective power. 11. We take care of the microscope by not leaving it in direct sunlight, cover it when not in use, clean the lenses using lens cleaning tissue, never touch it with water.
The Cells.
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The cell wall, vacuole and chloroplasts are only found in plant cells. The cell wall is made of cellulose. The cell wall is tough and so protects the cell and gives it a shape. The cell membrane controls what enters and leaves the cell.
Josephine Ebejer Grech B.Ed. (Hons.)
2! Revision Form 3 Biology
5. The cytoplasm is made up of 90% water with salts, proteins and other chemicals dissolved in it. It is a jelly like material that nourishes the organelles. 6. The nucleus is the biggest organelle in the cell. It controls all chemical reactions and cell division. 7. The mitochondria produce energy and respiration occurs in them. 8. The chloroplasts are full of chlorophyll. Photosynthesis occurs in them. 9. The vacuole is full of cell sap. It is a watery solution. 10. The ribosomes produce proteins. 11. The enzymes perform all the reactions in the cell.
Cell Division: 1. First the nucleus divides. cytoplasm adds, cell membrane pinches from the middle and cells separate.
Cell --> Tissue --> Organ --> System --> Organism.
Cell Specialisation is when a cell is given a particular job to do.
Topic 3: Movement of Substances.
1. Diffusion is the movement of substances from high concentration to low concentration without energy (passively). 2. Osmosis is the movement of water from dilute to high concentration without the use of energy (passively). 3. Active transport is the movement of substances against a concentration gradient with the use of energy (actively). 4. Hypertonic means more concentrated; hypotonic means less concentrated; and isotonic means equally concentrated as. 5. A visking tube is a semi- permeable membrane tube that allows small molecules go pass through it until a balanced concentration is reached on both sides. 6. The cell membrane is semi- permeable while the cell wall is fully permeable. 7. A plant cell cannot burst when placed in hypotonic solution because the cell wall protects it since it is rigid. 8. An animal cell can burst when placed in hypotonic solution as it doesn’t have a cell wall to protect it. 9. When a plant cell is placed in hypertonic solution the cell membrane becomes detatched from the cell wall. This is called plasmolysis. 10. When an animal cell is placed in a hypertonic solution it shrinks. 11. An Amoeba doesn’t burst in water because although it doesn’t have a cell wall it has a contractile vacuole. This expels extra water from the cell. 12. Rates of diffusion: the five factors that effect the rate of diffusion are: temperature, pressure, concentration in and out of cells, distance to diffuse, size of molecules. 13. Pure distilled water has the highest water potential. Water with mineral salts in it has a lower water potential.
Josephine Ebejer Grech B.Ed. (Hons.)
3! Revision Form 3 Biology
Topic 4: Classification.
1. Charles Darwin wrote the theory of evolution in a book called “The Origin of Species”. 2. A small organism has a bigger surface area to volume ratio and therefore it doesn’t need organs and systems but diffusion and osmosis through the cell membrane are enough. 3. Viruses are on the borderline between living and non-living. 4. The head of virus is called a capsid. 5. A capsid is made up of the substance protein. 6. In a capsid there is DNA or RNA that is the genetic material. 7. In a capsid there are no jelly like material called cytoplasm and no organelles. 8. A bacteriophage is a virus that attacks only bacteria and not humans or animals. 9. Reproduction of a virus: A virus approaches a cell; Virus injects its genetic material in the cell; the genetic material replicates inside the cell using the cell’s resources; every genetic material builds up the capsids and viral structures; the new viruses burst the cell and invade other cells. 10. Example of viral diseases are A.I.D.S., Influenza and meningitis. 11. We study 5 kingdoms of living things. These are bacteria (Monera), protista, fungi, plants, and animals. 12. Monera (bacteria) include unicellular prokaryotic organisms. 13. Protista include unicellular eukaryotic organisms. 14. Fungi include organisms that have hyphae instead of cells. 15. Plants include multicellular organisms that contain chlorophyll. 16. Animals include multicellular organisms that are heterotrophic. 17. Autotrophic means produce their own food using carbon dioxide, water, light and chlorophyll. 18. Heterotrophic means have to take in food ready made. 19. Kingdom Protista is sub-divided into two phyla. Phylum Protophyta includes photosynthetic unicellular organisms like Chlorella. Phylum Protozoans includes unicellular non-photosynthetic organisms like Amoeba. 20. Kingdom Bacteria include organisms that don’t have a proper nucleus but only contain one circular strand of DNA free floating in the cytoplasm. 21. Kingdom Fungi form mycelium that is a network of hyphae. 22. Kingdom Plants is subdivided into 4 phyla. Phylum Bryophytes includes the mosses: phylum Pteridiophytes includes the ferns; phylum Gymnosperms includes the conifers and phylum Angiosperms includes the flowering plants. 23. Mosses have a body called thallus because there is no differentiation in the cells. 24. Ferns reproduce by sori on the underside of each leaf. 25. Conifers produce cones that bear naked seeds. 26. Flowering plants bear flowers that are the reproductive organs. 27. Monocots are angiosperms with fibrous root system and parallel veins in their leaves. The flowers have petals in threes. 28. Dicots are angiosperms with tap root system and branching veins in their leaves. The flowers have petals in fours or fives.
Josephine Ebejer Grech B.Ed. (Hons.)
4! Revision Form 3 Biology 29. Wind pollinated flowers have small, unconspicuous flowers that need the wind to pollinate them. Their pollen is light and smooth. 30. Insect pollinated flowers have large petals that are scented and conspicuous that need the insects to pollinate them. They look up to the sky and are not hanging down. Their pollen is sticky or has hooks to grip to the body of the insect. 31. Kingdom Animals is sub-divided into 8 phyla. 32. Phylum Coelenterates / Cnidarians includes soft bodied organisms with a single opening and with stinging cells called nematocysts. Example jellyfish. 33. Phylum Platyhelminthes / Flatworms includes flat long segmented worm example tapeworm. 34. Phylum Nematodes / Roundworms includes long round not segmented worms like the Ascaris. 35. Phylum Annelids / Segmented worms includes long round segmented woms like the earthworms. 36. Phylum Molluscs includes soft bodied animals that can have an internal, external o no shell at all. An example of a mollusc is a octopus / squid / snail / slug. 37. Phylum Arthropods includes organisms with an external exoskeleton and jointed appendages. This phylum includes 4 classes. Class Insects includes arthropods with 6 legs example fly. Class Arachnids inclues arthropods with 8 legs example spider. Class Crustaceans includes arthropods with more than 8 but less than 20 legs like the woodlouse. Class Myriapods includes millipedes and centipedes that have more than 20 pairs of legs. 38. Phylum Echinodems includes invertebrates with spines on their surface example sea urchins. 39. Phylum Vertebrates includes organisms with a backbone and inner skeleton. This phylum includes 5 classes that are Fish, Amphibians, Reptiles, Birds and Mammals. Fish have scales and gills, fins and air bladder for buoyancy while swimming. Amphibians have a moist skin through which they can breathe like the frog. Reptiles have a scaly skin and are ectotherms (cold blooded). Mammals have mammary glands and are endotherms (warm blooded). Birds have feathers and beak. 40. Yeast is a unicellular fungus that reproduces by budding. 41. Yeast performs anaerobic respiration also known as alcoholic fermentation. The equation is sugar ---------> alcohol + carbon dioxide + energy. 42. Kingdom --> Phylum --> Class --> Order --> Family --> Genus --> species. 43. In a Biological Nomenclature the genus is written first starting with a capital letter and the species name is written next starting with a small letter. Both words must be italics or underlined separately.
Plant Structure and Function
1. In a plant the palisade mesophyll layer contains cells that are rich in chloroplasts. The spongy mesophyll cells are spaced apart to allow diffusion of gases. The upper and lower epidermis provide shape to the leaf. The guard cells form the stomata that are tiny holes. The vascular bundle contains the xylem that carries
Josephine Ebejer Grech B.Ed. (Hons.)
5! Revision Form 3 Biology
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water and phloem that carries the products of photosynthesis. The upper epidermis is covered with a waxy cuticle that prevents excessive water loss. Carbon dioxide enters the leaves from the stomata and oxygen produced leave the leaf from the same stomata. The loss of water from the plant is known as transpiration. The roots anchor the plant in the soil. The leaves have a large surface area and are full of chlorophyll to perform photosynthesis. The stalk holds the leaves and flowers above the soil. Xerophytes are plants with special adaptations to live in dry places such as a desert. They have thick waxy cuticle, sunken stomata, rolled up leaves, reduced leaves, spines on the leaves (cactus), swollen leaves or stems to hold water, etc.
Topic 5: Increasing in Numbers.
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Vegetative reproduction means asexual reproduction in plants. Asexual means only one parent is needed. Sexual means two different sex cells are needed. Asexual reproduction produces clones and sexual reproduction produces variation. 5. Examples of vegetative reproduction are stolons, rhizomes, bulbs, corms, tubers, and artificial propagation like cuttings and grafting. 6. Other organisms reproduce asexually. Amoeba reproduces by binary fission; yeast reproduces by budding; fungi reproduce asexually by spores. 7. A flower is the reproductive organ of an angiosperm. 8. The carpel is the female part of the flower and the stamen is the male part of the flower. 9. A carpel includes the ovary, style and stigma. Inside the ovary there are the ovules that are the female gametes (sex cells). 10. A stamen includes the filament and anther. In the anther there are the pollen that are the male sex cells (gametes). 11. Pollination is the transfer of pollen from the anther to a stigma. 12. Self pollination when pollination occurs on the same flower. 13. Cross pollination is when pollination occurs on different flowers of different plants. 14. Fertilisation occurs after pollination if the pollen grain grows a pollen tube from the stigma, into the style and into the ovary, and the pollen nucleus travels down the pollen tube to the micropyle (hole) of the ovule and finally the two nuclei fuse together. 15. After fertilisation the ovule becomes the seed; the ovary becomes the seeds wall; the receptacle becomes the endosperm. 16. When a dormant seed is watered, the water enters the testa through the micropyle (small hole). 17. Epigeal germination means that remains of the seed come out of the soil after that the plant grows.
Josephine Ebejer Grech B.Ed. (Hons.)
6! Revision Form 3 Biology 18. Hypogeal germination means that the remains of the seed remain buried under the soil after that the plant grows.
Topic 6: Conditions Supporting Life.
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Abiotic factors means non-living factors. Biotic factors means living factors. Examples of abiotic factors are light, gravity and water. 4 factors that affect the rate of transpiration are: light, heat, wind and humidity. 5. Directional responses of plants to stimuli are called tropisms. 6. The closing of flowers during night and opening during day is called nastic response. 7. Responses according to day length are called photoperiodism. 8. Directional response according to light is called phototropism. 9. Directional response according to gravity is called geotropism. 10. Response towards light is called positive phototropism. 11. Response away from light is called negative phototropism. 12. Response towards gravity is called positive geotropism. 13. Response away from gravity is called negative geotropism. 14. Auxins are growth regulating substances in tissues which cause rapid extension of cells in the region of the shoot behind the tip. 15. A clinostat is an electic turntable that rotates four times every hour. 16. A relationship between 2 organisms where both benefit is called mutualism. 17. A relationship between 2 organisms where one benefits and one is unaffected is called commensialism. 18. A relationship between 2 organisms where one benefits and one is harmed is called parasitism. 19. Flower gives nectar to a bee and bee gives pollination to the flower. This relationship is called mutualism. 20. A tapeworm getting food and shelter from a human and the human gets malnourishment form the tapeworm. This is parasitism. 21. Ants eat the dropped bread of a girl. commensialism 22. Nitrogen fixing bacteria get shelter from the plant and the plant gets nitrates from the nitrogen fixing bacteria. mutualism 23. Beneficial bacteria in the gut of herbivores digest some of the cellulose and provide the cow with sugars. mutualism 24. The Plasmodium causes the disease Malaria to humans, and while the humans become harmed, the Plasmodium has food and shelter. parasite 25. The mosquito Anopheles carries the Plasmodium to the human being. The mosquito acts as a vector. 26. The Plasmodium is carried in the blood of the human to the liver where it multiplies. 27. The human suffers intermittent fever and chills and this disease is known as Malaria.
Josephine Ebejer Grech B.Ed. (Hons.)
7! Revision Form 3 Biology Topic 7: Soil.
1. Soil is made up of gravel, sand, silt, clay and organic material. On the topsoil there is a lot of humus. In the sub-soil there are a lot of roots. Many organisms live in the soil like the subsoil that burrows in the soil to areate it and fertilise it. Sandy soil drains water quickly. Clay soil retains a lot of water. Loamy soil is the best soil.
Josephine Ebejer Grech B.Ed. (Hons.)