Chapter One

What is Life?

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• Organisms are living things. All living things share six important features:

1. Cellular organization

2. Contain similar chemicals

3. Use energy

4. Grow and develop

5. Respond to their surroundings

6. reproduce

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• A cell is the basic unit of structure and function in an organism.– Unicellular, or singled-celled, organisms

include bacteria, the most numerous organisms on Earth.

– Multi-cellular organisms are composed of many cells.

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• Cells are composed of chemicals. – Water is the most abundant chemical in cells.– Carbohydrates provide energy to the cell.– Proteins and lipids are the building materials of

the cells.– Nucleic acids are the genetic materials that

direct the cells activities.

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• Living things grow and develop. – Growth is the process of becoming larger.– Development is the process of change that

occurs during an organism’s life to produce a more complex organism.

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• Stimulus and Response:– A change in an organism’s surroundings that

causes the organism to react is called a stimulus.

– An organism reacts to a stimulus with a response – an action or change in behavior.

For example, the stove is on, and by accident, you touch the stove – (hot-stimulus). Immediately you pull away from the stove (reaction).

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• Another characteristic of organisms is the ability to reproduce, or produce offspring that are similar to the parents.– People once believed that living things arise from non-living

things – FALSE! However this concept is called spontaneous generation.

– We know that all organisms need four things to stay alive:• Energy• Water• Living space (room to grow and develop)• Stable internal conditions (ex: body temperature)

– The maintenance of stable internal conditions despite changes in surroundings – this is called Homeostasis.

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• Autotrophs are organisms that make their own food.

• Heterotrophs are organisms that cannot make their own food.– All organisms need food, shelter, and water.

– F. Redi• Francesco Redi - One of the first to disprove spontaneous generation.

An Italian doctor who proved maggots came from flies. (Italian 1668)

• Spontaneous Generation: The idea that organisms originate directly from nonliving matter. "life from nonlife"

F. Redi

• Redi's Problem

• Where do maggots come from? Hypothesis: Maggots come from flies.

• Redi put meat into three separate jars.– Jar 1 was left open.– Jar 2 was covered with netting.– Jar 3 was sealed from the outside.

F. Redi

• Jar-3 - Sealed No maggots developed.

• Jar-2 - Covered with netting, Maggots appeared on the netting. Flies were observed laying eggs on the netting.

• Jar-1 - Left open Maggots developed. Flies were observed laying eggs on the meat in the open jar.

Louis Pasteur

Louis Pasteur

• Pasteur boiled some broth to kill any microbes present. With special glassware, he allowed air to circulate over the broth, but prevented microbes in the air from reaching the broth. As Pasteur expected, no microbes appeared in the broth. Pasteur’s findings showed that microbes were not spontaneously generated from the broth itself. Microbes would only appear in the broth if they were allowed in with the air. He clearly showed that even for microbes, life came only from life—‘Microscopic beings must come into the world from parents similar to themselves.

Redi and Pasteur

Read pg 22 and pg 23 and answer the following questions:

1. In Redi’s experiment, what factors were identical in each test?

2. How did the tests differ in Redi’s experiment?

3. What factor is the variable in Redi’s experiment?

4. What is the variable in Pasteur’s experiment?

Redi and Pasteur

1. In Redi’s experiment, what factors were identical in each test? Both had meat in a jar and both were exposed to air.

2. How did the tests differ in Redi’s experiment? Redi covered one jar with a cloth.

3. What factor is the variable in Redi’s experiment? The cloth covering the jar – flies could not reach the meat.

4. What is the variable in Pasteur’s experiment? Whether or not the broth was boiled.

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Discovering Cells

The Cell Theory

The Cell Theory

1. All living things are composed of cells.

2. Cells are the basic unit of structure and function in living things.

3. All cells are produced from other cells.

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Looking Inside Cells

Diagram of 3 types of CellsBacteria Cell Nerve Cell

Blood Cell

Diagram of an Animal Cell

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• Inside a cell are tiny structures called organelles, which carry out the specific functions in the cell.

Cell Membrane

• Let's look at the cell membrane and see how the membrane keeps all of the pieces inside. When you think about a membrane, imagine it is like a big plastic bag with some tiny holes. That bag holds all of the cell pieces and fluids inside the cell and keeps any nasty things outside the cell. The holes are there to let some things move in and out of the cell.

The Nucleus

• The cell nucleus is like the brains of the cell. It helps control eating, movement and reproduction. If it happens in a cell, chances are the nucleus knows about it. The nucleus is not always in the center of the cell. You probably won't find it near the edge of a cell because that might be a dangerous place for the nucleus to be. It will be a big dark spot somewhere in the middle of all of the cytoplasm. If you don't remember, the cytoplasm is the fluid that fills cells.

The Nucleus

Floating in the nucleus are thin strands called chromatic, which contain the genetic material, or the instructions for cell functions.

Cytoplasm

Cytoplasm is the region between the cell membrane and the nucleus. Many organelles are found in the cytoplasm. Cytoplasm is a clear-whitish liquid.

Mitochondria

• The mitochondria are known as the powerhouses of the cell. They are the organelles that act like a stomach that takes in nutrients, breaks them down, and creates energy for the cell.

Endoplasmic Reticulum

• Endoplasmic Reticulum carries proteins and other materials from on part of the cell to another.

Ribosomes

• Ribosomes are the protein builders or the protein synthesizers of the cell. They are like construction guys who take one amino acid at a time and build long protein chains.

Golgi

Collections of sacs and tubes called Golgi bodies distribute proteins and other materials throughout the cell.

Lysosomes

• You will find organelles called lysosomes in nearly every animal-like eukaryotic cell. Lysosomes hold enzymes that were created by the cell. They exist in the cell to digest. They might be used to digest food or break down the cell when it dies.

The Plant Cell

The Cell Wall

• While cell membranes might be around every cell, cell walls made of cellulose are only found in plant cells. Cell walls are made up of specialized sugars called cellulose. This cellulose provides a protected framework for a plant cell to survive and gives the plant its shape.

Vacuoles

• Vacuoles might store food or any variety of nutrients the cell would need to survive. They might even store waste products so that the rest of the cell is protected from contamination. Eventually those waste products would be sent out of the cell.

Chloroplasts

• Chloroplasts are the food producers of the cell. They are only found in plant cells. Every green plant you see is working to convert the energy of the sun into sugars. That process happens in the chloroplast

Bacteria Cell

• What important organelle is a bacteria lacking?

Bacteria Cell

• A bacterial cell is smaller than a plant or animal cell and does not contain a nucleus.– Organisms whose cells lack a nucleus are called

prokaryotes.– Organisms whose cells contain a nucleus are

called eukaryotes.