Biology mock

• Plant cell components:

  • Cell Wall
  • Vacuole
  • Chloroplast
  • Nucleus
  • Cytoplasm
  • Cell Membrane
  • Mitochondria
  • Chloroplasts
• Cell functions:

  • Contains chromosomes which carry genetic information and control the action of the cell
  • Cell Membrane controls the entry and exit of substances
  • Mitochondria: site of most cell reactions
  • Vacuole: contains a watery sugary solution called sap, pushes the cytoplasm against the cell wall
  • Chloroplasts: site of photosynthesis, contains cellulose and provides structural support for cells
  • Cell Wall: provides structural support for plant cells
  • Nucleus: controls the action of the cell
• To examine cheek cells:

  1. Place a drop of methylene blue on a glass slide

  2. Gently rub the inside of your cheek with a cotton bud and transfer the cells to the glass slide

  3. Wipe the end of the cotton bud in the drop of methylene blue

  4. Place the cotton bud in a beaker of disinfectant

  5. Use a mounted needle to gently lower a coverslip over the glass slide

  6. Use a light microscope to examine the slide
• To examine onion cells:

  1. Using forceps, peel a thin layer of epidermis from a freshly cut piece of onion

  2. Lay the epidermis onto a glass slide

  3. Add a drop of iodine solution to the onion epidermis

  4. Use a mounted needle to gently lower a coverslip on the glass slide

  5. Use a light microscope to examine the slide
• Organ: composed of several tissues performing specific functions, e.g., the heart pumps blood
• System: a group of organs working together to carry out specific functions, e.g., the circulation system carries substances around the body
• Blood components:

  • Red blood cells: carry oxygen and defend the body against pathogens/infectious diseases
  • White blood cells
  • Plasma: carries dissolved substances like carbon dioxide
• Platelets: clot the blood, forming a temporary seal to prevent blood from flowing back to the heart
• Light microscopes allow magnification up to x1000, while electron microscopes use a beam of electrons and can magnify up to x50,000,000
• Biological Staining:

  • Iodine Solution: makes nuclei more obvious, stains any starch present blue/black (used to stain plant cells)
  • Methylene blue: stains acidic parts of the cell blue, making nuclei more obvious (used to prepare animal cells and bacteria)
• Specialized cells differentiate to cells with specific functions, e.g., muscle cells, sperm cells, red blood cells with hemoglobin and a biconcave shape for efficient oxygen transport
• Tissues are groups of similar cells with a similar function, e.g., muscles contract and shorten
• Arteries have thicker walls because they carry blood under pressure away from the heart
• Capillaries are the smallest blood vessels that carry blood through the organs of the body
• Capillaries form extensive networks so that no cell is far away from a capillary
• Capillaries have very thin walls to allow materials to diffuse easily between the blood and the body cells
• Effects of an atheroma:

  • Makes it more difficult for blood to flow through arteries, increasing the likelihood of blood clots forming
  • Small arteries can become blocked, leading to conditions like heart attacks or angina
• Pulmonary artery takes deoxygenated blood to the lungs to be reoxygenated
• Vena Cava is the main vein that carries deoxygenated blood to the heart
• The right atrium receives deoxygenated blood from the vena cava
• The tricuspid valve allows blood to flow one way, preventing backflow to the heart
• The right ventricle pumps deoxygenated blood towards the lungs
• The semilunar valves carry oxygenated blood from the heart to the organs
• The left atrium receives blood from the pulmonary vein
• The bicuspid valve allows blood to flow only one way in the left ventricle
• The left ventricle pumps oxygenated blood into the aorta
• Red blood cells have no nucleus, a regular disc shape, and are smaller than white blood cells
• Pulmonary circulation involves blood being pumped from the heart to the lungs and back to the heart
• Systemic circulation involves blood being pumped from the heart to the body and then back to the heart
• Energy from the Sun is the source of all energy for ecosystems
• Light energy is essential for all living things on the planet
• Absorbed energy is used for photosynthesis to produce substances that become part of the cells, increasing the biomass of the plant
• Biomass refers to the mass of living materials in plants and along food chains
• In ecosystems, energy is passed down from producers to consumers:

  • Producer: makes its own food by photosynthesis
  • Consumer: an organism that eats other organisms
  • First stage consumer: first organism that eats in a food chain
  • Second stage consumer: second organism that eats in a food chain
  • Third stage consumer: third organism that eats in a food chain
• Different types of consumers in ecosystems:

  • Herbivore: only eats plants
  • Carnivore: only eats animals
  • Omnivore: eats both plants and animals
• Tertiary consumers are at the top of the food chain, feeding on secondary consumers
• Food webs and food pyramids illustrate the flow of energy and the relationships between organisms in ecosystems
• Pyramids of numbers show the number of organisms at each feeding level in an ecosystem
• Plants absorb nitrates from the soil to make proteins
• Nitrogen in the atmosphere is converted into nitrates by nitrogen-fixing bacteria in the root nodules of leguminous plants and some free-living bacteria in soil