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bad, Biology (Evolutionary trees (An evolutionary tree or a phylogeny is a…

- - - - Ferns and their relatives
      - About 13,000 species
      - These plants reproduce using spores
      - These plants do not produce seeds
    - - Such as the conifers
      - About 1,000 species
      - These plants use seeds which are held in cone like structures
    - - Mosses, liverworts and hornworts
      - About 20,000 species
      - These plants do not have phloem or xylem
      - These plants reproduce using spores When the spores germinate, they produce motile male gametes (like very simple sperm) and so they are restricted to wet habitats
      - These plants do not produce seeds
    - - Flowering plants
      - About 300,000 species
  - - - Seed plants reproduce using pollen rather than dispersing spores, and the embryo that forms is contained within a seed
    - - Most plant species are flowering plants in which the seeds are held in the ovary, which becomes the fruit
    - - Specialised xylem and phloem which conduct water, mineral ions or sugars and amino acids throughout the plant
- - - - All living eukaryotic cells contain mitochondria. Cells which have a high demand for energy, such as muscle cells, have large numbers of mitochondria. Some of the reactions of respiration take place in mitochondria.
      - Since bacteria don't possess mitochondria, all of the reactions of respiration must take place in the cytoplasm.
    - - Cell walls have large holes in them, so it is not a barrier to water or dissolved substances. It is freely permeable.
      - The cell wall is a layer of non-living material that is found outside the cell membrane of some cells. In plants, it is made of cellulose (a carbohydrate made from glucose), in fungal cells it is made from chitin and in bacteria it is made from peptidoglycan (a mixture of carbohydrates and amino acids).
      - The cell wall is a tough layer that helps the cell keep its shape and why it is plants have a fixed shape; animal cells, which lack a cell wall, can be more variable in shape. The contents of a plant cell (vacuole and cytoplasm) push out against the cell wall which give the plant support.
    - - All cells, Prokaryotes and eukaryotes, contain ribosomes. These are too small d be seen with a light microscope, but are present in the cytoplasm. Proteins are made on ribosomes.
    - - Cells of the green parts of plants have chloroplasts. Like mitochondria, chloroplasts are enclosed by a membrane that separates their contents from the rest of the cytoplasm. Chloroplasts absorb light energy to make food in the form of sugars such as glucose in the process of photosynthesis. Chloroplasts are green because they contain a green pigment called chlorophyll. Plant cells that aren't green such as root cells lack chloroplasts.
      - Since bacteria don't possess chloroplasts, all of the reactions of photosynthesis must take place in the cytoplasm.
    - - Eukaryotic cells contain a membrane-bound nucleus. A few cells such as red blood cells or mature xylem cells (which lacks any cytoplasm and are dead ) lack a nucleus. The nucleus controls the activities of the cell. This is done through the DNA which determines which protein a cell can make.
      - In eukaryotes the DNA is packaged into several linear chromosomes. Human cells contain 46 chromosomes, although other species have different numbers of chromosomes. The DNA in chromosomes is arranged into sections called genes; one gene codes for one specific protein. Although chromosomes vary in length, they can contain several hundred to a few thousand genes each.
    - - Plant and fungal cells contain a large permanent vacuole. This is a membrane-bound compartment that is used for storage of molecules such as dissolved sugars, mineral ions, pigments (e.g. in petals). The watery contents of the vacuole is known as cell sap. Although similar structures can be found in animal cells (we refer to these as vesicles), they are small and temporary.
    - - The cytoplasm is a gelatinous material predominantly made up of water with many substances dissolved in it. Other structures described below such as the nucleus, ribosomes and mitochondria are found in the cytoplasm. Many chemical reactions of the cell happen in the cytoplasm.
    - - Capsule
        
        Not always present, this is a layer of protective slime surrounding the cell wall.
      - Flagellum
        
        Not always present, this allows bacteria to move. In bacteria it acts as a kind of motor, rotating the long flagellum and propelling it through water.
      - Plasmids
        
        A small, extra loop of DNA. Plasmids may contain extra genes and they are used extensively in genetic engineering to transfer new genes into bacteria. Bacteria may have one or several plasmids.
    - - This is a thin layer that forms a boundary between the cytoplasm and the outside. It is mostly made up of lipids and proteins. The basic structure of the cell surface membrane is the same in both prokaryotes and eukaryotes. Cell membranes are selectively permeable. This means that the cell is able to control what substances can enter or leave the cell.
  - - - Eukaryotic cells make up all organisms other than bacteria - i.e. plants, animal, fungi and the protoctista. They contain an extensive set of membrane-bound compartments, notably the nucleus, mitochondria and in photosynthetic cells chloroplasts. Structures in a cell that carry out a particular function such as chloroplasts, mitochondria and ribosomes are known as organelles.
    - - They are only found in bacteria and contain fewer components. In particular, prokaryote lack a membrane-bound nucleus, in which the DNA is packed into chromosomes. Prokaryotic cells tend to be much smaller than eukaryotic cells with a few exceptions.
- - - - Plasmodium
      - Paramecium
      - Amoeba
- - - - There are various types, but all vary the amount of light passing through the specimen. The diaphragm is just below the stage.
    - - Sometimes a bulb, sometimes just a mirror.
    - - One for fine and one for coarse focus.; you should always focus with both hands to avoid straining the mechanism.
    - - Where the specimen (slide) goes. There are usually clips of some description to hold it in place.
    - - Tis is the one you look down; the school microscopes have a 10x one.
    - - Works in combination with the eyepiece to magnify the image; there may be several to chose from on a rotating turret. The school microscopes have a 4x, 10x and 40x lens.
  - - - millimeters (mm)
      - micrometers (μm)
      - meters (m)
- - - - DNA is an example of a nucleic acid. The other type of nucleic acid found in organisms is RNA (ribonucleic acid).
      - Viruses, although not living organisms, also contain a nucleic acid - some have DNA whereas others have RNA. When a virus infects a cell, it injects its DNA or RNA into the cell, and the infected cell then uses it to make more copies of the virus proteins.
      - DNA is the molecule which provides instructions for how a cell is built and functions. In simple terms, the DNA molecule is a molecular code which determines which proteins are synthesised by the cell. The precise type of DNA that a cell contains determines which organism the cell belongs to; in other words, the DNA in the nucleus of a frog cell is different from the DNA in the nucleus of a human cell.
      - All living organisms contain DNA (deoxyribonucleic acid) in their cells. In Prokaryotes (bacteria), the DNA is a single loop located in the cytoplasm. In Eukaryotes, the DNA is packaged using proteins into multiple linear strands called chromosomes.
  - - - Organisms can grow by either enlarging cells by increasing the volume of cytoplasm by cell division, which will increase the number of cells in the organism.
      - Multicellular organisms carry out both kinds of growth whereas when single-celled organisms divide the two individual daughter cells are considered different organisms.
    - - Reproduction is a feature of all organisms. Most organisms reproduce sexually which leads to offspring that are variable. Some organisms may reproduce asexually, in which case the offspring are genetically identical to each other and to the parent offspring.
    - - Sensitivity is the ability to respond to changes in their surroundings. In large multicellular organisms this is either through nervous systems or by using hormones (chemical messengers carried in the bloodstream). In plants, responses usually take the form of changes in the pattern of growth, and are regulated by chemicals.
      - In unicellular organisms, sensitivity is usually confined to moving in response to stimuli such as light or to chemicals.
    - - Excretion is the removal of waste products from an organism. The key part of this definition is that the substances excrete were produced by the organism. Examples include getting rid of carbon dioxide (a waste product from aerobic respiration), and urea (from the breakdown of excess proteins). Excretory products need to be removed from the cell or from the organism as they are often toxic at high concentrations.
      - Note that excretion is different from egestion. Egestion is the removal from the body of undigested food in the form of faeces. The cellulose cell walls of plants is a large component of faeces; humans are unable to digest cellulose and so this passes through the digestive system unchanged.
    - - Respiration is the release of energy (usually I the firm of the molecule called ATP (Adenosine Triphosphate)) through the oxidation of an energy source (such as glucose).
      - Note that this kind of 'cellular' respiration is not respiration in the sense of breathing (taking air into the lungs), although the oxygen we breathe is used in cellular respiration. In prokaryotes like bacteria, respiration takes place in the cytoplasm but in eukaryotes respiration takes place in specialised organelles called mitochondria.
      - Aerobic respiration requires oxygen; anaerobic respiration can occur in the absence of oxygen and is carried out by some bacteria, some fungi and to a very limited extent by human muscles. This is similar to the process by which lactobacillus produces lactic acid used in the process of making yoghurt.
      - Plants carry out respiration just like animals (and therefore use up oxygen) as well as carrying out photosynthesis (which produces oxygen)
    - - Nutrition is the obtaining of chemicals for either use in respiration to release energy or for use in the building of new molecules with which to construct new cells.
      - A cell or an organism may be described as carrying out heterotrophic or autotrophic nutrition. Heterotrophic organisms use pre-existing food molecules which they may digest and use. Animals are examples of heterotrophs. Autotrophic organisms synthesise food molecules from simpler molecules. All photosynthetic organisms are autotrophic - they use carbon dioxide and water to synthesise simple sugars such as glucose.
      - The most common nutrients you will encounter are glucose (a simple sugar) that is the main substance used in respiration and amino acids which are used to synthesise proteins.
    - - Nonetheless, we do consider movement one of the characteristics of life since all cells are able to move components around inside the cytoplasm, even if this is not immediately visible to the naked eye.
      - Some plants have the ability to move tissues or organs, such as the opening and closing of stomata, and Venus fly traps can rapidly close their traps. Both of these are reversible, and so considered movement. The way in which plants 'bend' towards the light, however, is in fact a growth response and irreversible, and so not considered movement.
      - Many animals have the ability to move in the sense of locomotion (moving the whole organism from one place to place), although of course plants and some animals such as corals are fixed in one place.
    - - Homeostasis is the maintenance of constant internal conditions despite changes in the external environment.
      - For complex multicellular organisms such as humans, this includes many factors such as keeping the concentration of blood (i.e. water balance), temperature, blood pH and the concentrations of mineral ions within strict limits
      - For unicellular organisms such as bacteria, they clearly have less of an ability to control factors such as temperature, but they still regulate the chemical composition of the cytoplasm such as pH, water levels and mineral ion concentrations.
- - - - Order
      - Family
      - Class
      - Genus
      - Phylum
      - Species
      - Kingdom
  - - - The genus is capitalised but the species is not
      - They should also be either italicised or underlined if handwritten