شرح ساينس الصف الرابع الابتدائي لغات - الفصل الدراسي الأول
شرح ساينس رابعة ابتدائي - ترم أول

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لينك واتس اب
This Lesson:
Unicellular organisms
They are living organisms that their bodies consist of one cell only.
Examples: Bacteria.
Multicellular organisms
• They are living organisms that their bodies consist of many cells.
Examples: Humans, plants and animals.

Structure of multicellular organisms bodies :


Let's see the structure of the human body as an example of multicellular organisms:

Cells
- The human body contains different shapes of animal cells.
Examples:

Tissues
- Each tissue is often composed of a group of similar cells that do the same function.
Examples:


Systems
- Each system is composed of a group of different organs to do a certain function.
Examples:

Organs
- Each organ is composed of a group of different tissues to perform its own function.
Examples:

Whole body
- The human body is composed of a group of different systems.


- Although multicellular organisms are made up of many cells that differ in
shape and structure, most cells have some common characteristics, where
most cells contain

The Functions of Cell Parts
Cell membrane
It is the outer lining of the cell.
Functions:
1. It protects the cell.
2. It controls the substances that can enter or leave the cell through "selective permeability" feature.

Mitochondria
- They are one of the organelles of the cell.
- They are known as the "powerhouses" of the cell.
Function:
They provide the cell with the energy it needs by converting sugar inside the cell into energy
through the "cellular respiration".

Cellular respiration
It is the process that takes place inside the mitochondria, where oxygen is used to obtain the chemical energy stored in food to help the cells make their functions.

Cytoplasm
Function:
It is the gelatinous liquid (thick liquid) inside the cell in which all other cell parts (nucleus and organelles) float.
Nucleus
Function:
It controls all the cell activities such as:
- Formation of proteins.
- Cell division to form new cells.

Endoplasmic reticulum
It is one of the organelles of the cell.
Function:
It helps in assembling (collecting) and transporting proteins inside the cell to build and repair the cell.
Golgi apparatus
It is one of the organelles of the cell.
Function:
It helps in packing and transporting different materials:
- between the cells.
- out of the cell.

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