biology

• The cytoplasm is the gel-like substance inside the cell that contains various organelles and is the site of many cellular processes.
• Types of dichotomous keys


  • Written in a and b choices
  • Making a physical table
• Species


  A group of organisms that can reproduce to produce fertile offspring
• Kingdoms


  • Prokaryote
  • Plant kingdom
• Ferns


  • Have roots, stems, complex leaves and vascular tissue
  • Produce spores
  • No thick cuticles so can only survive in shady, humid areas
  • Gametes swim through film of moisture to reach the site of fertilisation
• Angiosperm


  • Flowering plants
  • Plants with enclosed seeds
• Monocotyledons


  • The seeds of monocotyledons each contain one embryonic leaf (the ‘cotyledon’). Many monocotyledons have leaves with parallel veins and the parts of their flowers come in threes. Examples of monocotyledons include: palms, orchids, grasses
• Dicotyledons


  • The seeds of dicotyledons each contain two embryonic leaves. Dicotyledons have leaves with branching veins, and the parts of their flowers come in fours or fives. Examples of dicotyledons include: buttercups, dandelions, oak tree
• Invertebrates


  Stay small
• Vertebrates


  Grow larger
• Phylum


  • Arthropod
  • Insect
  • Arachnid
  • Crustacean
  • Myriapod
• Classes


  • Fish - lose wet scales on their skin, have gills, have soft eggs
  • Amphibian - smooth moist skin, adult live on land, have loose legs
  • Reptile - dry fixed scales, lay eggs with rubbery shells on land, have lungs
  • Bird - skin covered with feathers, wings and two legs
  • Mammal - have hair or fur, have a placenta, young feed on milk from mammary glands, external ears visible, give birth to live young, endothermic
• Ways to identify animals

  • Limbs [appendages (fins, wings, leg, horns)]
  • Body coverings [smooth skin, scales, feathers, hair]
  • Temperature regulations, ectothermic (outside of body, reptiles, amphibians, fish) endothermic (heat comes from the inside of their body)
  • Breathing mechanism (gills or lungs)
• Viruses do not fit in the five-kingdom classification system as they do not show the typical features of living things. Unless they are inside a host cell they do not undergo respiration, nutrition or reproduction. There is great variation between different viruses although all have a protein coat and genetic material (can be DNA or RNA or both)
• Topic 2: Organisation of an organism
• Practice questions - Outcomes - Slides
• Indro


  • Cytoplasm: liquid environment inside the cell
  • Cell membrane: boundary of the cell, keeps things in and out
  • Genetic material (DNA): stores code for production of proteins that run the cell
  • Ribosomes (RNA): site of protein production
  • Enzymes involved in respiration: essential for energy production
• Animal Cell


  • Cell membrane: Double layered membrane made of proteins and fats. Around the entire cell. Holds cell contents in shape. Controls the movement of substances into and out of the cell. It is selective in the molecules that can pass and those that cannot. This is called ‘selective permeability’.
  • Cytoplasm: Jelly-like substance that fills spaces within the cell. Mostly water, with a variety of chemical substances dissolved in it (salts, sugars, enzymes). The fluid of the cytoplasm allows many chemical reactions to take place inside the cell.
  • Nucleus: Large, spherical structure in cytoplasm. Colourless, transparent. Most organisms have one nucleus per cell. Surrounded by cytoplasm and organelles. Control centre of cell, contains chromosomes (DNA) - genetic information; controls cell reproduction; controls protein synthesis e.g. enzyme production
  • Rough endoplasmic Reticulum: Network of flattened, interconnected membranes. Ribosomes are attached to it. Connects cell membrane with cytoplasm. Ribosomes are attached
• Endoplasmic Reticulum


  • Throughout the cytoplasm
• Ribosomes


  • Site of protein synthesis
• Cell


  Contains chromosomes (DNA) - genetic information; controls cell reproduction; controls protein synthesis e.g. enzyme production
• Rough endoplasmic Reticulum


  • Network of flattened, interconnected membranes
  • Ribosomes are attached to it
  • Connects cell membrane with cytoplasm Ribosomes are attached
• Endoplasmic Reticulum


  • Found throughout the cytoplasm
• Ribosomes


  • Site of protein synthesis (link amino acids together in correct sequence)
  • Newly synthesised proteins pass from ribosomes to ER where folding occurs
• Mitochondria


  • Found in the cytoplasm
  • Aerobic respiration occurs here
  • Cells with high rates of metabolism require large amounts of mitochondria to provide sufficient energy
• Vesicles


  • Membrane-bound sacs that function in storage and transport
  • The membrane of a vesicle can fuse with the membranes of other cellular components
• Chloroplast


  • Found in the cytoplasm of plant cells where photosynthesis occurs
  • Site of photosynthesis
  • May serve as organelle for storing starch
• Cell Wall


  • Made up of cellulose (little elasticity)
  • Some are thickened with chemicals such as lignin (for strength eg in tree trunks) or suberin (for waterproofing eg in leaves)
  • Around the entire cell in plant cells and fungi
  • Provides support and strength
  • Not selective like the cell membrane
• Vacuole


  • Large, fluid (sap) filled sac surrounded by a membrane (tonoplast)
  • In the cytoplasm (large vacuoles more common in plant cells)
  • Storage → Contains substances such as mineral salts, sugars and amino acids dissolved in water. Can also contain dissolved pigments
  • Support → Pushes outward on cytoplasm making cell firm or turgid
• Magnification calculation


  1. Magnification = Image/Actual Size

  2. You may be given the value of magnification only and then asked to calculate the actual size. In this case, you will need to measure the drawing (across its widest length) on the paper itself to get a value for the image size. Cells are often measured in micrometres (µm [1mm is 1000 µm])
• Specialised Cells


  • Dedicated to one particular function in an organism
  • The shape of these cells suits their function
  • Specialised cells in all multicellular organisms
  • All specialised cells start from the same stem cell before being assigned a ‘job’
• Ciliated Cells


  • Has a layer of tiny hairs (cilia) which can move and push mucus in the trachea and bronchi
  • The mucus can transport trapped dust and microbes when it is pushed by the cilia
• Root Hair Cells


  • Absorb water and minerals from the soil and store it until it can be passed into the vascular system
  • Large extension (the root hair) to give it a large surface area for absorption and a large vacuole for storing the water
• Xylem Vessels


  • Transports water and supports the plant
  • No cytoplasm (so water can freely pass), no end wall (so many cells can form a continuous tube), walls strengthened with a waterproof substance called lignin
• Palisade mesophyll cells


  • In the middle of the plant leaf
  • Tall, thin cells arranged in columns and separated by very narrow air spaces
  • Contain many chloroplasts, and densely packing of cells allow for the absorption of the maximum amount of light energy
• Nerve Cells


  • Conducts nerve impulses
  • Has a long fibre called an axon along which impulses travel, a fatty sheath which gives electrical insulation and a many branched ending which can connect to other cells
• Red Blood Cells


  • Transport oxygen
  • No nucleus, leaving more space for haemoglobin (a pigment which carries oxygen)
  • Very flexible, meaning they can be forced through narrow blood vessels
  • Large surface area to ensure the efficient uptake of oxygen
• Sperm and egg


  • Sperm: Are motile, have flagellum that beat to move towards the ovum. Small
  • Egg: Much larger, Do not move, have a large food store
• Organs


  • Structure made up of a group of tissues, working together to perform specific functions
• Tissues


  • Group of cells with similar structures, working together to perform a shared function