Download Sc 8 Unit 2 Topic 3 Notes WD

Unicellular and Multicellular Organisms
Unicellular (single-celled):
-Made up of only one cell
-Unicellular organisms are simple- lack tissues and organs
-Cannot grow very large, must take in all materials they need through cell
membranes so most can only live in watery, food-rich surroundings
Multicellular (many-celled):
-Made up of 2 or more cells
-Bigger and more complex
-May look different because they are specialized for specific functions
-Can live in a wide variety of environments (get energy from variety of foods)
-Have specialized cells (more efficient than unicellular organisms)
The cell is the smallest unit of life. Cells with similar structure and functions
are organized into tissues. Tissues that work together for a common purpose
from organs, and an organ system is a group of organs that work together
for a common purpose.
Cells TissuesOrgansOrgan System
Cell Size: Why don’t we see very big cells?
All cells need a supply of materials and get ride of wastes.
Materials leaving and entering the cell must do so across the cell membrane.
A larger cell needs more material and produces more wastes. With a larger
volume the materials and wastes have to travel further .
So… Cells are at a size in which they function most efficiently
Organisms get bigger by adding more cells.
Organelles: Structures inside the cell that has a specific function
Structure
Function
Nucleus
“Command center”
Directs all cellular activities such as
movement, growth and other life functions.
Mitochondria
“Powerhouse”
Where the energy the cell receives is
converted into a form it can use
Cell Membrane
“Controllable gateway”
Lets needed materials in and waste out
Vacuoles
Where nutrients, water and other
substances can be stores by the cell. Plant
cells have one big one but animal cells have
many smaller ones.
Cytoplasm
“Kitchen”
Contains the nutrients required by the cell.
Cell Wall
“Fame”
Found only in plant cells. Provides strength
and support to the plants.
Chloroplast
“Solar Panels”
Contains chlorophyll for photosynthesis,
converting the sun’s energy into food for
the cell. Found only in plant cells