Biology

• Characteristics of Living Organisms:

  • Movement: action causing a change of position
  • Respiration: chemical reactions breaking down nutrients for energy
  • Sensitivity: ability to detect and respond to changes
  • Growth: permanent increase in size and dry mass
  • Reproduction: processes making more of the same organism
  • Excretion: removal of waste products
  • Nutrition: taking in materials for energy, growth, and development
• Organisms are classified into groups based on shared features

  • Species: group of organisms that can reproduce fertile offspring
  • Classification sequence: Kingdom → Phylum → Classes → Orders → Families → Genus → Species
  • Binomial System of Naming Species: Genus species format, genus capitalized
  • Classification helps show evolutionary relationships
  • DNA base sequence used to classify organisms
  • Dichotomous keys use visible features to classify organisms
• Five Kingdoms:

  • Animals: multicellular ingestive heterotrophs
  • Plants: multicellular photosynthetic autotrophs with cellulose cell walls
  • Fungi: single-celled or multicellular heterotrophic and saprotrophic organisms
  • Prokaryotes: single-celled organisms with no true nucleus
  • Protocists: single-celled organisms with a nucleus, eukaryotes
• Vertebrates:

  • Mammals: fur/hair, internal fertilisation, mammary glands
  • Reptiles: thick, dry, scaly skin, internal fertilisation
  • Fish: wet scales, external fertilisation, uses gills to breathe
  • Amphibians: smooth, moist skin, external fertilisation, gills & lungs
  • Birds: feathers, hard eggs, internal fertilisation
• Arthropods:

  • Invertebrates with three standard features: exoskeleton, jointed legs, segmented body
  • Crustaceans, Arachnids, Myriapods, Insects
• Classification of Plants:

  • Ferns: reproduce by spores, no flowers/seeds
  • Flowering plants: reproduce sexually with flowers and seeds, seeds produced inside the ovary
• Viruses:

  • Not part of classification system
  • Take over host cell's metabolic pathways to replicate
  • Structure: genetic material inside a protein coat
• Cell Structure:

  • Cell membrane, cytoplasm, nucleus, mitochondria, ribosome, endoplasmic reticulum
  • Plant cells: vacuole, cell wall, chloroplasts
  • Prokaryotes: no mitochondria, true nucleus
• Levels of Organisation:

  • Cells, Tissues, Organs, Organ systems
  • Specialised Cells and their functions
• Diffusion:

  • Net movement of particles from higher to lower concentration
  • Important for movement of gases and solutes
  • Factors influencing diffusion: concentration gradient, temperature, surface area, distance
• Osmosis:

  • Net movement of water molecules from higher to lower water potential
  • Role in aiding digestion, excretion, and transport
  • Effects on cell size in different concentrations
• Active Transport:

  • Movement of particles from lower to higher concentration using energy
  • Involves carrier proteins
  • Needed for optimising nutrient uptake
• Biological Molecules:

  • Carbohydrates, Fats and Oils, Proteins
  • Food tests for Starch, Reducing sugars, Proteins, Fats and oils, Vitamin C
• Structure of DNA:

  • Chromosomes made of DNA, double helix structure
  • Bases pairing: A and T, C and G
• Enzymes:

  • Catalysts that speed up chemical reactions
  • Involved in metabolic reactions as biological catalysts
  • Lock and Key Model, Substrate, Product
• Size of Specimens:

  • Magnification formula, unit conversions
  • Actual size, image size, magnification
• Enzymes have an optimum temperature of around 37°C in animals and human bodies
• When temperature increases, molecules move faster, collide more frequently, and are more likely to bind to active sites
• If the temperature is too high, enzymes denature, losing shape and no longer binding with a substrate
• If the temperature is too low, there is not enough kinetic energy for the reaction to occur
• Enzymes are sensitive to pH, with some working best in an acid, others in an alkaline environment
• Enzymes denature if the pH changes, breaking hydrogen bonds and preventing binding with the substrate's active site
• Pepsin works best in acidic conditions, amylase in neutral conditions, and trypsin in alkaline conditions
• Photosynthesis is the process by which plants manufacture carbohydrates from raw materials using energy from light
• Glucose produced in photosynthesis is used for respiration, energy storage, cellulose cell walls, and making proteins and sugars
• Starch is used as an energy store, cellulose to build cell walls, glucose for respiration, sucrose for transport in the phloem, and nectar to attract insects for pollination
• Limiting factors in photosynthesis include light intensity, where increasing light increases the rate until a certain point, then other factors like carbon dioxide or temperature become limiting
• Most dicotyledonous plant leaves have a large surface area and are thin, with structures like cuticle, upper/lower epidermis, palisade and spongy mesophyll, vascular bundles, xylem, phloem, and stomata
• Nitrate ions and magnesium ions are essential for making amino acids and chlorophyll in plants
• A balanced diet contains proper proportions of carbohydrates, fats, proteins, vitamins, minerals, and water to maintain good health and metabolism
• Vitamin C is essential for collagen and resistance to diseases, while Vitamin D is crucial for the absorption of calcium
• The digestive system involves processes like ingestion, physical and chemical digestion, absorption, assimilation, and egestion
• Main organs in the alimentary canal include the mouth, salivary glands, oesophagus, stomach, small intestine (duodenum and ileum), pancreas, liver, gall bladder, large intestine (colon and rectum), and anus
• Teeth include incisors for cutting, canines for tearing, premolars for grinding, and molars for chewing, with structures like enamel, cement, pulp, and dentine
• Enzymes like amylase, maltase, protease, and lipase are involved in chemical digestion, breaking down starch, proteins, and lipids into smaller, soluble substances for absorption
• Absorption in the small intestine involves villi and microvilli to increase the surface area for nutrient absorption, with lacteals absorbing fatty acids and glycerol, and capillaries providing a better blood supply
• Xylem transports water and mineral ions, while phloem transports sucrose and amino acids in plants
• Root hair cells absorb water and minerals from the soil through osmosis and active transport, with a large surface area crucial for water and ion uptake
• Water uptake in plants can be investigated by placing a plant in dyed water and observing the staining of certain plant parts
• Transpiration is the loss of water vapor from leaves, which evaporates from the surface of the mesophyll cells into the air spaces and diffuses out of the leaves through the stomata