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Here are some typical organisms (forms of life on Earth.)

Organisms are made of tissues

Tissues are made of cells

There are many types of tissues in animals, and in plants.

Cells are the basic unit of life.

A cell is the smallest unit that can truly be called living.

Most cells are so small that they can only be seen with a microscope.

Animal cell versus plant cell

We can see that inside cells there are smaller parts.

These are called organelles. They are tiny biological machines.

Each organelle has its own job. Examples include the nucleus, ribosome, mitochondria, Golgi, etc.

Let’s take a closer look at this.

Characteristics of Life

Organelles, an introduction

Organelles: In more depth

Let’s look at what goes on inside a cell

What is the role of enzymes in cells?



Endocytosis and exocytosis

Let’s look at single-celled organisms



How do cells reproduce?

The cell cycle


Asexual reproduction


Honors Biology

Active transport across cell membranes

Ion channels and carrier proteins

Endosymbiosis: origin of eukaryotic cells from prokaryotes

Size and scale

The amazing cell and DNA size and scale app!

Cells – how big? from a hair down to a virus

Interactive scale of the Universe (No, really, the entire known scale!)

Numbersleuth magnifying the Universe

Powers of 10: Molecular Expressions from FSU

If the moon were only 1 pixel: A tediously accurate scale model of the solar system 😉

Nikon Universcale

Powers of Ten (1977) by Charles and Ray Eames


Virtual labs

PhET membrane channels app

Serendip diffusion applet


Sample questions

Feb 2016 MCAS. Beginning with one parent cell, how many daughter cells are typically produced from one mitotic division?
A. 1 .   B. 2 .    C. 4 .   D. 8


Learning Standards

Massachusetts Curriculum Frameworks: Biology

6.MS-LS1-1. Provide evidence that all organisms (unicellular and multicellular) are made of cells.

6.MS-LS1-2. Develop and use a model to describe how parts of cells contribute to the cellular functions of obtaining food, water, and other nutrients from its environment, disposing of wastes, and providing energy for cellular processes.

Disciplinary Core Idea Progression Matrix: LS1.A Structure and function

Grades 6-8: All living things are made up of cells. An organism can be made of one cell
(unicellular) or many cells (multicellular). Within cells, specialized structures are responsible for specific functions. In multicellular organisms, cells work together to form tissues and organs that are specialized for particular body functions.

Grades 9-10: Systems of specialized cells within organisms carry out essential functions of life. Any one system in an organism is made up of numerous parts. Feedback mechanisms maintain an organism’s internal conditions within certain limits and mediate behaviors.

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