Transcript Chapter One - My Teacher Pages

Chapter One
What is Life?
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•
Organisms are living things. All living things
share six important features:
1.
2.
3.
4.
5.
6.
Cellular organization
Contain similar chemicals
Use energy
Grow and develop
Respond to their surroundings
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.
2.
3.
4.
In Redi’s experiment, what factors were identical in each
test?
How did the tests differ in Redi’s experiment?
What factor is the variable in Redi’s experiment?
What is the variable in Pasteur’s experiment?
Redi and Pasteur
1.
2.
3.
4.
In Redi’s experiment, what factors were identical in each
test? Both had meat in a jar and both were exposed
to air.
How did the tests differ in Redi’s experiment? Redi
covered one jar with a cloth.
What factor is the variable in Redi’s experiment? The
cloth covering the jar – flies could not reach the meat.
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
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2.
3.
All living things are composed of cells.
Cells are the basic unit of structure and function in living
things.
All cells are produced from other cells.
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Looking Inside Cells
Diagram of 3 types of Cells
Bacteria Cell
Blood Cell
Nerve 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.