In this presentation you will: explore the cell theory The Cell Theory Next >

In this presentation you will: explore the cell theory

The Cell Theory

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All living things are made up of cells.

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Introduction

They are the building blocks of life.

Without living cells, an organism is not alive.

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Introduction

Some organisms, like bacteria and yeast, are made up of only one cell.

Unicellular

Multicellular

Multicellular

These are called multicellular organisms.

These are called unicellular organisms.Others, like most plants and animals (including humans) are made up of many cells.

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In the mid-17th century an English scientist named Robert Hooke used a microscope to look at a section of cork.He noticed that cork was made up of microscopic box-like units.

Discovery of the Cell

He called them cells.

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Discovery of the Cell

Hooke was the first person to observe and define the cell.

After Hooke’s initial discovery, more scientists became involved in understanding cells.

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Modern microscopes look quite different from the one Hooke used.

They work in the same way, but can use:

Discovery of the Cell

either one or two eyepieces

either one or two objective lenses

Objective lens

Eyepiece

Monocular

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Discovery of the Cell

One that uses two eyepieces and one objective lens is binocular.

The stereoscope uses two eye pieces and two objective lenses.

Binocular

A microscope that uses one eyepiece and one objective lens is called a monocular microscope.

This makes the specimen appear in 3D to the user.

Stereoscope

Cell Theory

The investigation of the cell led to these accepted facts about cells:

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all living organisms are made up of at least one cell

all cells come from other cells

This is known as the Cell Theory.

cells are the basic unit of life

What Cells Do

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All living organisms must be able to carry out the seven life processes to survive.

These processes are: movement respiration sensitivity growth reproduction excretion nutrition

Life Processes

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Cells can carry out these processes independently.

To be ‘alive’ an organism must be able to carry out all these life processes.

They are the smallest living thing that can.

They are alive.

Life Processes

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There are many different types of cells with many different jobs to do.

However, every cell carries out all of the life processes.

Life Processes

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Cells carry out the same functions, and have the same needs, as a whole organism. In fact, the function and survival of an organism depends on the ability of individual cells to carry out these processes.

oxygen, water and glucose in

carbon dioxide and water out

Life Processes

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For example, you need food and water because your cells need food and water.

You grow because your cells grow and divide.

oxygen, water and glucose in

carbon dioxide and water out

Movement

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Organisms need to be able to move to find food, shelter and avoid danger.

Animals can walk, swim or fly…

…plants can turn to face the light or close their leaves.

Movement

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Cells, and parts of cells, also move.

If you were to examine a live cell using a microscope, you would see things moving about inside.

For example, chemicals and molecules move to other parts of the cell that need them.

Respiration

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Living things need to take in oxygen and food to make energy.

The process that releases energy from these things is called respiration.

carbon dioxideoxygen

Respiration

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ATP is used by the cell to carry out the activities necessary for life.

oxygen + glucose → carbon dioxide + water + energy (ATP)

They use oxygen and glucose to produce energy in the form of a molecule called ATP.

Cells carry out respiration. It is called cellular respiration.

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Sensitivity

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Organisms need to be sensitive to their environment.

Cells also need this ability to sense their environment.

They need to respond to danger, or to a change in light or temperature.

Sensitivity

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For example, when a plant is placed in bright light, the cells on the darker side of the stem get longer.

This causes the whole stem to bend towards the light.

light

bright sideof stem

shaded sideof stem

The cells on the lighter side stay the same.

longer cells

Reproduction

Cells are able to grow and reproduce.

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Each cell originated from a previous living cell.

All cells eventually die.

Mitosis

This process is called mitosis.

Once mature, a cell can divide in half to produce two new identical cells.

Reproduction

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The ability of cells to grow and reproduce in this way, allows organisms to grow and repair themselves.

Nutrition

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Cells need nutrients like oxygen, water and glucose (sugar).

These nutrients are used to provide it with energy to live and grow.

oxygen, water and glucose in

Nutrition

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The cell membrane regulates the movement of water, nutrients and waste products into and out of the cell. 

All cells have a skin, called a cell membrane.

cell membrane

This separates and protects the cell from its surroundings.

oxygen, water and glucose in

Excretion

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Organisms must excrete (get rid of) waste products to stay healthy.

This is the same for cells.

If waste materials are not excreted from a cell, they will poison the cell and possibly kill it.

oxygen, water and glucose in

carbon dioxide and water out

Excretion

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During cellular respiration, carbon dioxide and excess water are produced as waste products.

These must pass out of the cell through the cell membrane.

carbon dioxide and water out

waste products

Question 1

All cells of an organism must carry out each life process so that the organism can survive.

Is this statement true or false?

Answer True or False.

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All cells of an organism must carry out each life process so that the organism can survive.

Is this statement true or false?

Answer True or False.

True

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Question 1

Question 2

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According to the cell theory, cells carry out similar functions in order to sustain life. Which of the following can cells do?

A) Use nutrients to make energy

B) Get rid of waste materials

C) Grow and reproduce

D) All of the above

Question 2

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According to the cell theory, cells carry out similar functions in order to sustain life. Which of the following can cells do?

A) Use nutrients to make energy

B) Get rid of waste materials

C) Grow and reproduce

D) All of the above

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Question 3

Which of the following statements is NOT accepted in the Cell Theory?

A) All living organisms are made up of many cells

B) Cells are the basic unit of life

C) Organisms and cells carry out similar functions in order to sustain life.

D) All cells come from other cells

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Question 3

Which of the following statements is NOT accepted in the Cell Theory?

A) All living organisms are made up of many cells

B) Cells are the basic unit of life

C) Organisms and cells carry out similar functions in order to sustain life.

D) All cells come from other cells

Summary

In this presentation you have seen:

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the Cell Theory