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Biology Year 9 Plants Year 9 Science 20121
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The Plant Kingdom All plants belong to the same kingdom (Plantae). Plants are called autotrophs, which means they make their own food through the process of photosynthesis through which they have have supplied sufficient oxygen to the atmosphere to allow all living organisms to respire. Plants have laid down the fossil fuels that provide humans with energy. Every other animal relies on plants either directly or indirectly for nutrition. Plants grow mainly on land but also can be found in the oceans and fresh water. They have been on Earth for millions of years. Plants species currently number about 260,000.
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Year 9 Science 2012 The structure and functions of parts of the plant The Shoot System Above ground (usually) Lifts the plant above the soil Main functions include: Leaves - photosynthesis Flowers - reproduction Fruit – seed dispersal Stem - food and water transport The Root System Underground (usually) Anchor the plant in the soil Main functions include: Absorb water and nutrients Transport water and nutrients Food Storage
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Year 9 Science 20124 The flat surface of the leaf called the blade helps capture maximum sunlight for photosynthesis. The leaf is attached by a stem-like petiole to the plant which branch out into veins. Inside these are xylem tubes to transport water to the leaf cells, which they require for photosynthesis and to keep the leaf cells turgid or rigid. The veins also contain phloem tubes which are able to transport the sugars (and starch which they are converted into), produced during photosynthesis, away to other parts of the plant for use and storage. The adaptations of leaves for photosynthesis
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Year 9 Science 20125 The adaptations of leaves for photosynthesis A waxy cuticle on the outside of the leaf provides a waterproof covering while remaining transparent to allow light into the leaf cells for photosynthesis. Openings (usually on the underside of the leaf) called stomata allow carbon dioxide to enter and diffuse into cells as well as allowing oxygen to move in and out. Two guard cells on either side of the stomata open and close the openings.
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How the structure of a leaf enables photosynthesis to occur effectively The cells at the top of the leaf are filled with chlorophyll, which gives leaves the green colour. The chlorophyll allows the leaf to absorb light energy which is required for photosynthesis. The spaces between cells in the spongy mesophyll allow carbon dioxide to diffuse around through the cells.
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Year 9 Science 20127 The significance of photosynthesis in making food Most living organisms depend on plants to survive. Plants convert energy from sunlight into food stored as carbohydrates through photosynthesis. Because animals cannot make their own food they must eat plants to gain nutrition. Plants produce oxygen, which is released during photosynthesis, which all organisms need for respiration.
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Light enters the leaf and is trapped by chlorophyll contained within the chloroplasts in the cells. Water is transported via xylem to the cell and the carbon dioxide enters through the stomata and diffuses to the cell. These substances react chemically within the chloroplasts, powered by the light and glucose (a sugar) is produced along with oxygen which diffuses out. The sugar leaves the leaf via the phloem. Carbon dioxide + Water +light → Glucose + Oxygen Photosynthesis transfers energy from sunlight into energy in chemicals such as glucose and starch.
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9 Starch test When a plant undergoes photosynthesis it produces glucose which is converted into starch for storage. If we want to investigate what factors are required for photosynthesis we use the starch test to enable us to reach a conclusion.
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10 Plants take up water through root hairs Water moves into the plant through root hairs. Water being drawn up the plants xylem due to transpiration decreases the pressure inside the root hair cells and this negative pressure pulls water in.
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Year 9 Science 201211 The xylem transports water and the phloem transports the products of photosynthesis Transport water around the plant Special features >Cells join into long and tube-like hollow vessels. >Cells have no end walls, so form a 'pipeline' carrying water from leaves to root. >Spirals and rings of lignin surrounding the cells strengthen the walls, to withstand pressure of water.
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Year 9 Science 201212 Xylem cells are called tracheids (cells with narrower diameters) or vessels (cells with wider diameters). Their cell walls contain cellulose and lignin making them extremely rigid. Xylem cells contain no membranes and are considered dead. These cells overlap to create a series of pathways that water can take as it heads to the leaves. There is no single column of xylem cells carrying water. The xylem is probably the longest part of the pathway that water takes on its way to the leaves of a plant. It is also the path of least resistance, with about a billion times less resistance than cell to cell transport of water. The xylem transports water and the phloem transports the products of photosynthesis
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Year 9 Science 201213 Osmosis is the diffusion of water molecules through a partially permeable membrane Diffusion means that the net movement of particles (molecules) is from an area of high concentration to low concentration. Oxygen, Carbon Dioxide and water move across the cell membrane by diffusion.
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14 Osmosis is the diffusion of water molecules through a partially permeable membrane Osmosis is the diffusion of water only through a partially permeable membrane from where water is in higher concentration to where it is in lower concentration. (or where the solute is in higher concentration )
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The effects of solutions of different concentrations on animal and plant cells Solution type that cell is in Isotonic Concentrations are the same on both sides of the membrane and water moves equally in both directions hypertonic Concentration of water is higher in the cell and a net movement of water outside causing the cell to shrink. hypotonic Concentration of water is higher outside the cell and a net movement of water inside the cell causes swelling or breakage Animal cell Plant cell
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Year 9 Science 201216 Plants solve the water problem by having a rigid cell wall. The entering water moves through the cell wall and the cell membrane. The water is stored in a vacuole. The wall protects the cell against expansion, and the resulting pressure makes the plant rigid or turgid. When the cell membrane shrinks away from the cell wall this is called plasmolysis. The effects of solutions of different concentrations on animal and plant cells
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Year 9 Science 201217 The process of transpiration Transpiration is the process where plants lose water from their leaves. Water enters a plant through root hairs. When stomata, on the underside of leaves, are open to allow CO 2 to diffuse in and O 2 to diffuse out, water vapour evaporates and diffuses out.
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Year 9 Science 201218 The process of transpiration 1. Water enters plant through root hairs by osmosis – high to low concentration of water. 2. Attraction between water particles pulls water up the plant through the xylem. 3. Water evaporates from the leaves through transpiration.
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19 The process of transpiration
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20 The role that stomata have in the process of transpiration Stomata are normally found only on the under or shaded sides of leaves. Their function is to capture CO 2 from the atmosphere by exchanging water for carbon dioxide. The exchange is accomplished by having water directly open to air to facilitate the capture.
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Year 9 Science 2012 21 Leaves are the main site of photosynthesis. They make food from carbon dioxide and water in the presence of light. As stomata open in the presence of light, carbon dioxide will diffuse into the leaf and at the same time, water vapour will exit the leaf through the stomata to the surrounding atmosphere through the process of transpiration. Plants will lose water vapour while taking up carbon dioxide through their stomata. If this water loss is uncontrolled, plants can deplete their water reserve. Stomata prevent water loss from the stoma by closing once the leaf has sufficient carbon dioxide. The role that stomata have in the process of transpiration
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Year 9 Science 201222 The leaf structure and types of cell inside a leaf Cuticle: Waxy layer water proofing upper leaves. Upper epidermis: Upper layer of cells. No chloroplasts. Protection. Vascular Bundle: Bundle of many vessels (xylem and phloem) for transport. Xylem: Living vascular system carrying water & minerals throughout plant. Phloem: Living vascular system carrying dissolved sugars and organic compounds throughout plant. Palisade Mesophyll: Tightly packed upper layer of chloroplast containing cells. Spongy Mesophyll: Lower layer of cells. Air space: Area for gases to disperse Lower Epidermis: Lower external layer of cells in leaf. Stomata: Opening between guard cells for gas & water exchange. Guard Cells: 2 cells surrounding stomata that control rate of gas & water exchange.
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Year 9 Science 201223 The parts of the flower and the role of the flower in pollination, seed production and dispersal Plants that produce flowers are known as angiosperms. The flowers are the reproductive structures where fertilisation occurs and seeds are produced.
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Year 9 Science 201224 The reproductive parts of an insect-pollinated flower and their functioning Insect-pollinated flowers have visible, often colourful petals that surround the flower's sexual reproduction parts. The petals can "advertise" for specific pollinators through their shape, size, colour and sometimes smell. The flowers are surrounded by sepals, which are small and usually green structures that protect the flower as its developing.
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Year 9 Science 201225 The reproductive parts of an insect-pollinated flower and their functioning The female part of the flower is called the pistil. The pollen from a male part of a flower is brought to the stigma by a pollinator. This process is called pollination. The pollen travels down the style into the ovary to join with an egg cell inside the ovules in a process called fertilisation. The male part of a flower is called the stamen. The pollen is produced in the anther which is held up by the filament. The pollen is collected by a pollinator. The pollen contains male gametes which will later fuse with the female gametes in the ovule during fertilisation.
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Year 9 Science 201226 The reproductive parts of an insect-pollinated flower and their functioning Insect-pollinated Flowers often contain nectar, a sweet sugar produced by the plant, to attract an insect. As the insect reaches into the flower for the nectar it may be brushed with pollen from the anther. If the insect moves to another flower it may brush the pollen against the stigma and therefore pollinate the flower. Flowers ripen their male and female parts of the flower at different times to prevent self pollination.
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Year 9 Science 201227 The differences in structure between insect-and wind-pollinated flowers Wind pollinated flowers are often small and green with no scent. Male anthers protrude out from the flower to allow the wind to pick up the pollen and disperse it away from the plant. Male and female parts develop at different times. Insect pollinated flowers are easily seen and often contain scent and nectar to attract the insects. The male parts are adapted so they make contact with the insect as it feeds from the flower.
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Year 9 Science 201228 Examples of insect-pollinated flowers
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Year 9 Science 201229 Examples of wind-pollinated flowers
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Year 9 Science 201230 Summary of pollination in plants 1.The male parts of the flower are the anther and filament 2.The female parts of the flower are the stigma, style and ovary 3.Male gametes are found in Pollen Produced in the Anther 4.Pollen needs to be moved to the female part called the Stigma of the same species of plant to reproduce 5.This process is called Pollination 6.Pollination can be helped by Wind Or Animal 7.An example of wind pollination is grass plants 8.A wind pollinated flower is most likely to look like - small, green, unscented 9.An example of animal pollination is a rose plant pollinated by insects 10.An animal pollinated flower is most likely to look like – colourful, with large petals, perhaps with a scent
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Year 9 Science 201231 Fertilisation in flowering plants 1.Pollen from either the same plant (self-pollination) or another plant (cross- pollination) needs to arrive on the flowers stigma 2.The pollen sends a tube down the style to reach the ovule, and the male gametes (there are two in every pollen grain) enter the ovule to fertilise the egg (female gamete) 3.One male gamete joins with one female gamete to form a zygote and the plant is fertilised. (The fertilised ovule develops into a seed)
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The differences between pollination and fertilisation in flowering plants Pollination just refers to pollen landing on the female stigma of the plant. This can either be with a pollinator or wind. Fertilisation refers to the sperm cell (that was in the pollen grain) joining with the egg cell to form a single cell (zygote). Pollination does not always lead to fertilisation
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Year 9 Science 2012 The formation of seed and fruit from ovule and ovary Once the flower has been fertilised by pollen the ovary grows to form the fruit. The ovules become the seeds. The outer part of the ovule grows into the seed coat. The zygote grows into the young plant – or embryo A fruit may have one or more seeds. The petals, sepals and other parts of the flower start to die and fall off.
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Year 9 Science 201234 Seed dispersal How are seeds dispersed? By animals By the wind Self dispersal
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Year 9 Science 201235 The conditions needed for germination of seeds Seeds will remain dormant until they receive water warmth light oxygen Then they will germinate. Other types of seeds may also require >fire to burn seed coat >soaking in water >scratched seed coat >being digested by animals Before they germinate
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Year 9 Science 201236 The structure of a seed The seed consists of the seed coat or the testa which surrounds the cotyledons or the food storage area. The embryo consists of the radicle which is the embryonic root and the hypocotyl which forms the first shoots and leaves of the plant. A small pore in the seed may be seen called the micropyle. This is where the pollen originally entered the ovule.
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