Download Sc 8 Unit 2 Topic 5 Notes WP

Topic 5
Cell Specialization and Organization
Cells are specialized for a specific task.
Animal Cells
Nerve cells have long, branched fibers running from the main part of the cell, shaped
to carry nerve signals from one part of the body to another.
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Red blood cells, which carry oxygen in the bloodstream, have a thin, disk like shape.
This gives them a larger surface area to pick up large amounts of oxygen.
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Bone Cells secrete a mineral matrix to provide the body with bony support.
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Muscle Cells affect movement by shortening, at rest they are stretched out.
Epithelial Cells (Skin Cells) Provides physical protection and controls permeability.
Humans are continually shedding and placing the thin outer layer of their skin. They
completely replace the outer layer of skin approximately every 28 days. Most
household dust is made up of dead human skin cells.
Plant Cells
Epidermal
Onionskin cells are flat and brick-shaped, so they can fit closely together to form a
continuous protective layer.
Conductive
The water-conducting cells of a plant are tube like, with thick walls and a network of
holes that let water pass easily through them.
Disadvantages of unicellular Organisms
-In Unicellular organisms one cell must carry out all the functions needed to keep it
alive.
-It must be able to move, obtain food, reproduce, and respond to the environment
-Unicellular organisms cannot grow very large.
Also, because they must take in all the materials that they need through their cell
membranes, most unicellular organisms can only live in watery, food-rich
surroundings.
Multicellular Organisms
- Can live in a wide variety of environment.
- They can grow very large.
- They can get their energy from a wide variety of foods.
- Their cells are more efficient because they can specialize in their particular
function and these specialized cells get grouped together and they can work with
other cells performing the same function.
Many plants and animals are made of trillions of cells.
Cells are grouped into Tissues, Tissues are grouped in Organs, and Organs are
grouped into Systems. These are known as different levels of organization in living
organisms.
Do the Activity on page 142.
Organs
Each organ is made of several tissues working together. For example, your stomach
is made of four main types of tissues. Other examples of organs in your body are the
lungs, the heart, and the kidneys.
Plant Systems
Root System obtains water and minerals as well as anchoring the plant to the
ground.
Shoot System (stems and leaves) make food for the plant.
Reproductive System (flowers, fruit and seeds) produces new plants.
Topic 5 Review page 144
Topic 4,5 Wrap up page 145