bio revision

• 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 organisms with non-cellulose cell walls
  • 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, 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: exoskeleton, one pair of compound eyes, two body segments, more than four pairs of legs
  • Arachnids: two body segments, four pairs of legs
  • Myriapods: segmented body, one pair of antennae, 10+ pairs of legs
  • Insects: three body segments, three pairs of legs, one pair of antennae, 1 or 2 pairs of wings
• 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, not considered living
  • Take over host cell's metabolic pathways to replicate
  • Structure: genetic material inside a protein coat
• Cell Structure:

  • All living things made of cells
  • Typical cells have cell membrane, cytoplasm, nucleus, mitochondria, ribosome, endoplasmic reticulum
  • Plant cells have vacuole, cell wall, chloroplasts
  • Prokaryotes (Bacteria) lack mitochondria and true nucleus
• Levels of Organisation:

  • Cells: building blocks of life
  • Tissue: groups of cells with similar structures
  • Organ: group of tissues working together
  • Organ system: group of organs with related functions
  • Specialised Cells: ciliated cells, root hair cells, palisade mesophyll cells, neurones, red blood cells
• Movement In and Out of Cells:

  • Diffusion: net movement of particles from higher to lower concentration
  • Factors influencing diffusion: concentration gradient, temperature, surface area, distance
  • Osmosis: net movement of water molecules from higher to lower water potential
  • Active Transport: movement against concentration gradient using energy
• Biological Molecules:

  • Carbohydrates: made from Carbon, Hydrogen, Oxygen
  • Fats and Oils: made from Carbon, Hydrogen, Oxygen
  • Proteins: made from Carbon, Hydrogen, Oxygen, Nitrogen, sometimes Sulfur
• Food Tests:

  • Starch: iodine solution test
  • Reducing sugars: Benedict's solution test
  • Proteins: Biuret solution test
  • Fats and oils: Ethanol Emulsion test
  • Vitamin C: DCPIP decolourisation test
• Structure of DNA:

  • Chromosomes made of DNA
  • DNA is a double helix with bases A-T, C-G
• Enzymes:

  • Catalysts that speed up chemical reactions
  • Enzymes are proteins that lower activation energy
  • Lock and Key Model: substrate fits into the active site
• 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 and lose their shape, 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 and work best at their optimum pH
• Changes in pH can denature enzymes, preventing them from binding with the substrate's active site
• Some enzymes work best in acidic conditions (e.g., Pepsin), others in neutral conditions (e.g., Amylase), and others in alkaline conditions (e.g., Trypsin)
• Photosynthesis is the process by which plants manufacture carbohydrates from raw materials using energy from light
• Chlorophyll traps light energy and converts it into chemical energy to form carbohydrates
• 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, carbon dioxide, and temperature
• Most dicotyledonous plant leaves have a large surface area and are thin
• Leaf structure includes the cuticle, upper/lower epidermis, palisade mesophyll, spongy mesophyll, vascular bundles, xylem, phloem, and stomata
• Mineral requirements for plants include nitrate ions for making amino acids and magnesium ions for making chlorophyll
• A balanced diet contains proper proportions of carbohydrates, fats, proteins, vitamins, minerals, and water
• Nutrients like carbohydrates provide energy, fats and oils serve as a source of energy and building materials, proteins are used for energy and building materials, and vitamins and minerals have various functions in the body
• Deficiencies in nutrients like Vitamin C can lead to scurvy, while deficiencies in calcium/Vitamin D can cause rickets and osteoporosis
• 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, pancreas, liver, gall bladder, large intestine, rectum, and anus
• Teeth include incisors for cutting and biting, canines for piercing and tearing, premolars for chewing and grinding, and molars for further chewing and grinding
• Chemical digestion involves enzymes like amylase, maltase, protease, lipase, and hydrochloric acid in gastric juice
• Absorption in the small intestine occurs through villi and microvilli, 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
• Root hair cells absorb water and minerals from the soil through osmosis and active transport
• Water uptake in plants can be investigated by placing a plant in dyed water and observing the staining of certain plant parts