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Kingdoms Organisms are classified into kingdoms, which are subdivided into smaller and smaller groups. The last two groups are genus and species. These words give each species its scientific name. Plants have green leaves, have cell walls made of cellulose and can photosynthesise. This kingdom has f...

Kingdoms Organisms are classified into kingdoms, which are subdivided into smaller and smaller groups. The last two groups are genus and species. These words give each species its scientific name. Plants have green leaves, have cell walls made of cellulose and can photosynthesise. This kingdom has four main groups: flowering plants (reproduce using flowers), conifers (reproduce using cones), ferns (reproduce without flowers or cones) and mosses (no roots). Some main groups in the animal kingdom are: vertebrates (with backbones), which are divided into mammals (hair, have live young), reptiles (dry scales, lay leathery eggs), fish (slimy scales, lay jelly eggs), amphibians (moist skin, lay jelly eggs) and birds (feathers, lay hard-shelled eggs) invertebrates, including molluscs (fleshy pad to move) and arthropods (jointed limbs) o arthropods include insects (6 legs, 3-part body) and arachnids (8 legs, 2-part body). Biodiversity The range of species in an area is called biodiversity. We should preserve biodiversity because: organisms depend on one another (they are interdependent) we won’t be able to make use of organisms if they become extinct more biodiverse areas recover better from natural disasters. Asexual reproduction in plants Some plants can reproduce using asexual reproduction. This is when one parent plant is able to produce offspring (e.g. by using runners in strawberries or tubers in potatoes). Sexual reproduction in plants Reproduction produces new living things (offspring). Sexual reproduction needs two parents to produce sex cells or gametes. The gametes fuse to produce a fertilised egg cell or zygote. The zygote uses cell division to grow into an embryo, which can grow into an adult and become a parent (completing its life cycle). The offspring from sexual reproduction contain characteristics from both parents. The differences in these characteristics is inherited variation. Gametes are produced by reproductive organs. In plants, these are contained inside flowers. The pollen grains made in the anther need to be carried to the stigma of another flower. Pollen can be carried by animals (such as insects). Pollen can also be carried by the wind. The carrying of pollen from an anther to a stigma is called pollination. Once on the stigma, a pollen grain grows a pollen tube, which enters the ovule containing an egg cell. The nucleus from the male gamete inside the pollen grain joins with the nucleus inside the egg cell to form a zygote. This is called fertilisation. The zygote grows into an embryo and the ovule becomes a seed, containing the embryo and a food store. A part of the flower forms a fruit. This is used for seed dispersal, which stops the new plants competing with the parent plants for water, nutrients, light and space. Some fruits are eaten by animals and the seeds come out in their faeces (e.g. apples). Some fruits are carried on the fur of animals (e.g. burdock). Some fruits are carried by the wind (e.g. dandelion). Some fruits explode, scattering the seeds (e.g. lupins). When conditions are right, seeds germinate. The resources needed are water, oxygen and warmth (WOW). Water allows chemical reactions to start, which break down the food store and allows cells in the embryo to swell up. Oxygen is needed for respiration, to release energy from the food store. Warmth is needed to speed up the chemical reactions. The root grows first then the shoot. Finally, new leaves open and photosynthesis can start in the chloroplasts. The glucose from photosynthesis is turned into starch to be stored. The mass of material produced is biomass. Photosynthesis can be summarised as a word equation: A growing plant needs light, air, water, warmth and nutrients called mineral salts (LAWWN). The energy for growth comes from respiration, a process in which oxygen is used to release energy from glucose. It happens in the mitochondria of cells and can be summarised as: Accuracy, estimates and sampling We can take a small sample of a larger population and use it to estimate what the larger population is like. Plant populations in an area can be estimated by taking samples using a quadrat. The more samples we take the more accurate the estimate is likely to be but the longer it will take to do. I n the world of flowering plants, or angiosperms, sexual reproduction takes place within the flowers. Flowers contain reproductive organs, housing a complex set of structures essential for creating seeds. A typical flower is comprised of stamens, male structures, and pollen-containing male sex cells. The female structures, including the stigma, style, and ovary, receive pollen and produce female sex cells. Adorned with vibrant colours, petals attract pollinators, while sepals protect the flower bud. Parts of a Flower carpel filament anther petals sepal stamens stem style stigma ovule ovary Let’s take a closer look at the reproductive system of a typical flowering plant. The key parts that we need to know about are: Sepals: They protect the flower plant that hasn’t yet opened. Petals: The pretty part that attracts insects. Stamens: These are the male parts of the flower, which are made up of the anther and are held up on the filaments. Anthers: These produce male gametes (a human male gamete is the sperm, and a female is the egg), in the form of pollen. Sexual Reproduction in Flowering Plants Notes The journey of reproduction begins with pollination, the transfer of pollen between plants of the same species. This pivotal process can occur through wind or water, but it is often facilitated by pollinators such as insects, birds, and mammals. Flowers, with their specialised adaptations like large colourful petals, enticing scents, and sweet nectar, attract these pollinators, underscoring their vital role in producing food crops, such as maize, for human sustenance. As we know, pollen grains need to move from the anther of one flower to the stigma of another for pollination to happen. Insects pollinate some plants, and others rely on the wind. Let’s examine these different types of pollination and how insect - and wind-pollinated plants differ from one another. Insects land on plants to search for food. In doing this, pollen sticks to them, and as they travel to the next plant for food, the pollen that is stuck to their body gets transferred onto the stigma. Our key pollinators include a variety of bees, flies and beetles. Without the important preservation of these insects, our food supplies will be under serious threat. Plants that rely on insect pollination have distinct characteristics to ensure that bees, flies and beetles are attracted to the plant and can successfully carry the pollen. Pollination Stigma: The female part of the flower that collects the pollen grains. Ovary: Another female part of the flower that produces female gametes in the form of ovules. Nectary: Sometimes present in plants to produce a sugary substance that aims to attract insects. What are the different types of pollination? These include: brightly coloured petals; scented nectar; sticky or spiky pollen grains; firmly attached internal anthers for insects to brush against; an internal, sticky stigma which pollen grains stick to when that all important insect brushes past. These adaptations include: Dull leaves, as the wind doesn’t need attracting! No scent or nectar, as there are no insects to be fed. More pollen than insect-pollinated plants, as the vast majority of it doesn’t make its way to other plants. Lightweight, smooth pollen grains that are easily carried by the wind. Dandelions are an excellent example of this. External, loose anthers that easily release pollen grains. External, feathery stigma that is designed to catch as much pollen as possible. Pollination Wind pollination is a bit different. In this process, air currents carry pollen from one plant to another. Plants that rely on wind pollination also have a set of characteristics that make them perfect for relying on air currents to spread pollen and fertilise. 2. Wind pollination Birds: Certain bird species, such as hummingbirds, play a crucial role in pollination by transferring pollen from one flower to another as they feed on nectar. Bats: In some regions, bats are important pollinators, especially of night-blooming plants. They transfer pollen as they feed on nectar. Water: Some aquatic plants rely on water for pollination. The pollen is released into the water, and currents carry it to reach the female reproductive organs of other plants. Mammals: Larger mammals, such as some rodents and primates, may inadvertently transfer pollen as they move through plants. However, this is less common compared to other methods. Gravity: Some plants rely on gravity for pollination. The pollen falls from the male reproductive parts to the female parts within the same flower or between neighbouring flowers on the same plant. Mechanical: Certain plants use mechanical means for pollination. For example, some plants have specialised structures that physically launch or catapult pollen to reach neighbouring flowers. 3. Other ways pollination can take place Pollination is the initial step in the reproductive process of flowering plants. It involves the transfer of pollen from the male structures (stamens) to the female structures (stigma) of the same plant species. Upon reaching the stigma, pollen grains initiate the formation of a pollen tube. This tube traverses the style, connecting the stigma to the ovule within the ovary. The pollen tube serves as a conduit for transporting two male sex cells toward the ovule. Within the ovule, situated in the embryo sac, one of the male sex cells fertilises the egg. This fertilisation event is critical as it initiates the formation of a seed, which has the potential to grow into a new plant under suitable conditions. Simultaneously, the other male sex cell unites with two cells within the embryo sac. This process leads to the development of endosperm, a starchy substance that serves as a nutritional source for the growing seed. The collaborative effort ensures the seed has the necessary energy for germination. As fertilisation finishes, the ovary undergoes a transformation, enlarging and evolving into a fruit. The fruit provides protection and support for the developing seeds, serving as a protective enclosure until they are ready for dispersal. Fertilisation Step 1: Pollination Stage 2: Pollen's Journey to the Ovule Stage 3: Fertilisation at the Ovule Stage 4: Dual Role of the Second Male Cell - Endosperm Development Stage 5: Ovary's Transformation into Fruit Seeds are protected inside fruits, which have ingenious adaptations for seed dispersal. Whether through wind, water, or the assistance of animals, seeds and fruits embark on diverse journeys, scattering the potential for new life across the landscape. Seed dispersal is an important stage in plants' life cycles. It assists the spread of seeds to new locations for germination and growth. This process is essential for the survival and spread of plant species in diverse environments. Seed dispersal plays a crucial role in the distribution and survival of plant species, enabling them to colonise new habitats, avoid competition with parent plants, and respond to changing environmental conditions. There are different ways that seeds are dispersed, each adapted to suit different plant species and environments. 1. Wind Dispersal Seeds equipped with adaptations like wings, parachutes, or tufts of hairs can be carried by the wind. Examples include dandelion seeds, maple seeds, and many types of grass. 2. Water Dispersal Seeds can float on water, facilitating dispersal through rivers, streams, or ocean currents. Coconut seeds, for instance, can float and are dispersed by ocean currents. 3. Animal Dispersal Seeds may attach themselves to the fur, feathers, or bodies of animals and be transported to new locations. Some seeds have adaptations like hooks or burrs that cling to the fur of passing animals. Fruits consumed by animals may have seeds that are later deposited in a different location through animal droppings. Examples include acorns dispersed by squirrels and berries consumed by birds. 4. Explosive Mechanisms Certain plants have developed mechanisms to forcefully eject their seeds into the surrounding environment. For example, the seed pods of touch-me-not plants (Impatiens) burst open when touched, scattering the seeds. Seed Dispersal 5. Ant Dispersal Some plants form symbiotic relationships with ants, which carry seeds back to their nests. The ants consume a part of the seed's outer coating, and the remaining seed is left in the nest, often in nutrient-rich conditions conducive to germination. Trillium and bloodroot are examples of plants that use this type of seed dispersal. Dalton’s atomic theory Dalton’s theory stated that: All matter is made up of tiny particles called atoms. Atoms are indestructible, and cannot be created, or destroyed. The atoms in an element are all identical. In compounds, each atom of an element is always joined to a fixed number of atoms of the other elements. During chemical reactions, atoms rearrange, to make new substances. For example: Atoms of an element Atoms in a compound Chemical reactions Some signs of a chemical reaction include such as a colour change, a gas being produced, a solid forming in a solution and an increase/decrease in temperature. The word equation for the reaction in the diagram above is: hydrogen + chlorine → hydrogen chloride REACTANTS PRODUCT No atoms are lost or gained so the mass of the reactants is equal to the mass of the products. Changes of state A change of state is a physical change. No atoms are lost or gained during a physical change and so the mass of the substance stays the same. Elements and symbols Examples: nitrogen = N lithium = Li sulfur = S copper = Cu chlorine = Cl iron = Fe The symbols for the elements used today have been agreed by scientists in all countries. They are either a single or double letter. The first letter is always a capital letter. Formulae Metals and non-metals The properties of a substance are what it looks like or what it does. There are two types: chemical properties (e.g. flammability, pH, reaction with acid) physical properties (e.g. melting point, boiling point, density). Periodic table Mendeleev originally ordered the elements in the periodic table by their masses. Today, the elements are in order of atomic number (the number of particles called protons in an atom). Elements with similar properties are in the same vertical group. The periodic table allows us to spot trends and patterns in these groups and across the rows (periods). Metal and non-metal oxides Many elements burn in air/oxygen to form oxides; e.g.: calcium + oxygen calcium oxide carbon + oxygen carbon dioxide metal oxides tend to form alkaline solutions. non-metal oxides tend to form acidic solutions. Metal oxides are bases and react with acids in neutralisation reactions: acid + base → salt + water e.g. hydrochloric acid + magnesium oxide → magnesium chloride + water sulfuric acid + copper oxide → copper sulfate + water Key Words Elements An element is a substance that cannot be broken down into other substances. The smallest part of an element that can exist is an atom. Each element is represented by a symbol. The first letter of the symbol is always capitalised, any following letters are lower case. The symbols for the elements are arranged on the periodic table. Mixtures A mixture is a substance consisting of two or more substances not chemically combined together. You can have mixtures of elements, mixtures of compounds or mixtures containing both. In a particle diagram of a mixture, not all of the molecules shown will be touching each other or be joined by sticks representing the bonds. Compounds vs Mixtures Compounds A compound is a substance made when two or more elements are chemically bonded together. A compound can be represented by a diagram. The atoms are shown touching each other or joined by a stick that represents a bond. Water is a compound made from one oxygen atom and two hydrogen atoms. Its formula is H2O. Compound Formulae The formula of a compound tells you: which elements the compound is made from. how many atoms of each element there are. Carbon dioxide has the formula CO2. C is the symbol for carbon. There are no subscript numbers after the C, so we know there is only one atom of carbon in the compound. O is the symbol for oxygen. There is a subscript 2 after the O, so we know there are two atoms of oxygen in the compound. atom The smallest part of an element that can exist. bond An attraction between atoms or molecules that enables the formation of chemical compounds. chemical formula A series of chemical symbols showing the number of atoms of each element in a compound. chemical reaction A process that involves rearrangement of atoms to produce new substances. chemical symbol A letter or series of letters used to represent an element, e.g. C for carbon, Na for sodium. compound A substance made up of two or more different elements chemically bonded together. element A substance made of only one type of atom. group A column of the periodic table that contains elements with similar chemical properties. metal An element or substance which is typically shiny, malleable and ductile. It typically conducts heat and electricity well. mixture A substance consisting of two or more substances not chemically combined together. non-metal An element or substance that is not a metal. period A row on the periodic table. trend The general direction in which a set of data changes, i.e. increasing or decreasing. Compounds Mixtures The different elements are chemically joined together. The different substances are not chemically joined together. The substance has different properties to the elements it is made from. Each substance keeps its own properties. The elements can only be separated using chemical reactions. Each substance can be separated easily using separating techniques like filtration, distillation, evaporation and chromatography. You cannot vary the amount of each element. So, the compound water always has one oxygen atom and two hydrogen atoms per molecule. You can vary the amount of each substance. So, you can add a teaspoon of salt to water, or a cup of salt to water, and it would still be a mixture of salt water. CO2 atomic mass element symbol element name atomic number CO2 mixture of elements mixture of compounds mixture of elements and compounds Key Words The Periodic Table Elements are arranged into groups based on their properties. Those with similar properties are found in the same group. Metals are found on the left of the stepped line, and non-metals on the right. However, some elements, particularly those close to the line have properties of both. Properties of Metals shiny good conductor of heat good conductor of electricity sonorous oxides form alkaline solutions high density malleable ductile Properties of Halogens some solids, a liquid and some gases at room temperature (melting and boiling points increase moving down the group) very reactive (reactivity decreases moving down the group) poor conductors of heat and electricity solids are brittle low density Properties of Noble Gases gases at room temperature (the melting and boiling points increase as you move down the group) unreactive (however reactivity increases slightly as you move down the group) poor conductors of heat and electricity low density Properties of Alkali Metals  solids at room temperature (melting and boiling points decrease moving down the group) very reactive (reactivity increases moving down the group) good conductors of heat and electricity soft shiny when cut low density Properties of Non-Metals dull poor conductor of heat poor conductor of electricity not sonorous oxides form acidic solutions low density brittle boiling point The temperature at which a substance changes from liquid to gas (evaporates). It is also the temperature at which a substance changes from gas to liquid (condenses). brittle Hard but easily broken. conduction The transfer of heat or electricity through a material. density The mass of a substance divided by its volume. The more dense a substance is, the heavier it feels for its size. displacement reaction A reaction in which a more reactive substance displaces a less reactive substance. ductile Can be stretched into wires. dull Not shiny. magnetic material A material that can be attracted by a magnet or made into a magnet. malleable Can be hammered or pressed into different shapes. melting point The temperature at which a substance changes from solid to liquid (melts). It is also the temperature at which a substance changes from liquid to solid (freezes). reactivity A measure of how easily a substance reacts with another substance. shiny A surface which reflects light. sonorous Makes a ringing sound when dropped. unreactive A substance which does not react Fluids Fluids are liquids or gases. The particle model The particle model can explain the properties of solids, liquids and gases. Solids Liquids Gases Properties fixed volume fixed shape fixed volume take shape of container expand to fill container take shape of container Particle diagram Particles are close together are held in fixed positions by strong forces are close together are held by fairly strong forces can move around are far apart  are held by very weak forces can move around Density Density is the mass of a certain volume of something, and it can be calculated using this formula: density =mass/volume The units for density are g/cm3 or kg/m3. Changes of state Substances can change state when they are heated or cooled. The three states of matter are solid, liquid and gas. A liquid evaporates from its surface. When it is boiling, bubbles of gas form within the liquid. The melting point and the freezing point of a substance are the same temperature. The temperature of a substance does not change while it is melting, even if it is still being heated. Changing density Substances expand when they are heated. The particles in a solid vibrate more and take up more space. The particles in liquids and gases move around faster and take up more space. When a material expands its density decreases. Substances contract when they cool down, as the particles have less energy and do not move as much. This reduces the volume and increases the density. When a liquid freezes and becomes a solid its density increases a lot. Ice is unusual, because it is less dense than liquid water. This is why ice floats on water. Pressure in fluids Both gases and liquids are fluids. Fluids can flow. Pressure in fluids acts in all directions. The particles in fluids are moving all the time and hitting the walls of containers and other things they come into contact with. The force of the collisions causes pressure, which acts in all directions. The pressure of gas in a container can be increased by: putting more particles into the container (so there will be more collisions with the container walls each second). heating the gas (so the particles move faster, hitting the walls harder and more often).  reducing the volume of the container (so the particles do not have as far to go between the walls and so collide with the walls more often). As you go deeper into the sea, pressure increases because there is more water above you pressing down. If you climb a high mountain, the air pressure on you will get less, because there is less air above you pressing down. Floating and sinking You can decide if something will float by working out its density, and the density of the fluid. If the density of the object is less than the density of the fluid, it will float. The density of water is 1 g/cm3 , so objects with densities less than 1 g/cm3 will float in water. Drag Drag is another name for air resistance or water resistance. The amount of drag on something can be reduced by giving it a smooth surface and a streamlined shape. The drag increases as the speed increases, so cars use up more fuel per kilometre when they are travelling fast. Drag is caused by particles in the fluid hitting the moving object, and by the force needed for the object to push the fluid out of the way. The particles transfer energy to the object, which is why objects