Grade 8 Science: Cells and Body Systems Overview

Cell Theory

All living things are made of one or more cells.

Plant Cell

Has a cell wall & chloroplasts.

Animal Cell

Has no cell wall, no chloroplasts.

Nucleus

Control center of the cell (contains DNA).

Cell Membrane

Controls what enters/exits the cell.

Cytoplasm

Jelly-like substance holding organelles.

Mitochondria

Produces energy ('powerhouse').

Vacuole

Stores food, water, and waste.

Cell Wall (plant)

Provides structure and support.

Chloroplast (plant)

Site of photosynthesis (makes food).

Levels of Organization in the Body

Cell → Tissue → Organ → Organ System → Organism.

Circulatory System

Moves blood, oxygen, and nutrients.

Respiratory System

Brings in oxygen, removes carbon dioxide.

Digestive System

Breaks down food into nutrients.

Nervous System

Sends signals through the body.

Muscular System

Allows movement.

Skeletal System

Supports and protects the body.

Excretory System

Removes waste (urine, sweat, CO₂).

Interactions Between Systems

Respiratory + Circulatory: Oxygen from lungs enters bloodstream.