Cells and Systems. Grade 8 Science. Topic 1 – Living Organisms. Take a moment to talk to the person next to you about all of the functions an organism needs to do to survive. Functions and Structures.
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Cells and Systems
Grade 8 Science
Take a moment to talk to the person next to you about all of the functions an organism needs to do to survive
Relate the three to one another in a sentence or two.
And Our Discovery of the Cell
From the top:
The Cell and its Structures
Grade 8 Science
Topic 4: Fluid Movement in Cells
Diffusion refers to the process by which molecules intermingle as a result of their kinetic energy of random motion.
Consider two separated containers of gas A and B. The molecules of both gases are in constant motion and make numerous collisions with the separation.
If the separation is removed, the gases will mix because of the random movement of their molecules. In time, a uniform mixture of A and B molecules will result.
Semi Permeable Membrane
A semi-permeable membrane is a membrane which will allow the passage of certain molecules through it (by the process of diffusion), and not other molecules.
The rate of passage depends on the pressure, concentration and temperature of the solvent on either side, as well as the permeability (how much it will let through) of the membrane to each type of molecule or solute.
Osmosis is the diffusion of particles across a semi-permeable membrane
The semi-permeable membrane only allows the solvent particles to cross. The solvent particles diffuse until a balance between all the particles is reached.
Osmosis is of great importance in biological processes where the solvent is water. The transport of water and other molecules across biological membranes is essential to many processes in living organisms. The energy which drives the process is usually discussed in terms of osmotic pressure.
Vascular plants contain two main types of conduction tissue, the xylem and phloem. These two tissues extend from the leaves to the roots, and are vital conduits for water and nutrient transport. In a sense, they are to plants what veins and arteries are to animals.
Vascular tissue consists of xylem and phloem. These two types of vessels run side-by-side, extending from roots to leaves. They provide channels for the transport of water and nutrients.
The function of xylem tissue is to:
• conduct water and dissolved minerals• Structural support
Tracheids Vessel Members
Transpiration - transfer of water from plants to the atmosphere.
Plants pump the water up from the soil to deliver nutrients to their leaves. This pumping is driven by the evaporation of water through small pores called “stoma” (singular: Stomata), which are found on the undersides of leaves.
Each stomata pore is bounded by two crescent shaped guard cells. Their opening and closing releases or retains the water within.
The evaporation produces what is known as the transpiration stream, a tension that draws water up from the roots through the xylem (water-carrying vessels in the stem).
This replaces the water that is lost, and allows minerals absorbed from the soil to be transported through the xylem to the leaves. This is important because many plant cells need the minerals as nutrients.
Grade 8 Science
You can think of the cells in your body as an orchestra. If you only had one type of cell or instrument in the orchestra, the orchestra would sound very plain. Orchestras are made up of many different types of instruments. Our bodies are made up of over 100 types of cells, this allows the music of our complexity to be incredibly intricate!
Nerve Cell – Elongated (long) and highly branched to allow for very quick transmissions of information
Xylem cell – perforated to allow water (and the minerals dissolved in them) to freely travel through them.
Food enters your body through your mouth and then passes to the stomach and intestines. It is broken down along the way into usable, soluble particles that can be used by different cells.
Sphygmomanometer measures blood pressure.
The blood is slowed and then listened to by a doctor with a stethoscope.
The volume of blood
High fibre diet is important to the colon to process waste materials.
Low fibre can lead to colon cancer.
Long-term stress, smoking, excessive alcohol or aspirin use can lead to a peptic ulcer.
Smoking, air pollution and industrial by-products (coal dust) can lead to disorders of the respiratory system.
Cilia – hair-like projections in the lungs are used to remove debris and particles. Poisons in cigarette smoke irritate the cells lining the lungs causing cells to produce more mucus.
Lung cancer is caused by tar and smoke in cigarettes, which cause the lung cells to grow out of control.
Proper care means maintaining healthy organs and organ systems. This can be accomplished with clean air and water, nutritious foods, exercise and sleep.
Your immune system will work best when you are well fed, rested and healthy.