Cells
Organisms can either be unicellular or multicellular. All cells work in specific ways and have different functions. Some
animals or plants have few cells while others have trillions.
Cells: All living things have cells. A cell is the smallest unit of life, anything below that is nonliving. A cell has a membrane
around it that separates its interior from the environment.
Unicellular: A unicellular organism is the one that has only one cell and grows as the cell grows. They are always going to be
microscopic or extremely small. One example is bacteria.
Multicellular: A multicellular organism is the one that has more than one cell. It can either be big or small in size and it
increase size as more cells are created. In these organisms cells are grouped and each group has a different function. An
example is humans.
This is an animal cell.
This is a unicellular organism.
This is a multicellular organism.
Sense and Respond to Change
All living things feel the change in the environment or inside their body and react to it. These can be internal or external. An
internal is when you feel hungry, you eat. The external is when the environment is cold, you try to get hot to stay the same.
Stimulus: A change that causes and organism to react. Stimuli can either be internal or external.
Homeostasis: This is when your body tries to maintain the same when something in the environment changes. It is the
organism’s ability to maintain the same internal conditions.
This hamster is hungry so he is eating
to keep the same. He sensed the
change inside his body and
responded to it by eating.
Reproduce
As the organisms grow and develop they should be able to reproduce. Organisms can reproduce in different ways. Some
need a mate, others divide, and others have special cells. Organisms need to reproduce so that they can exist. Organisms
reproduce by either sexual or asexual reproduction.
Asexual: A reproduction that does not involve the union of two sex cells. One parent has an offspring without a partner. This
baby is exactly the same as his parent. Most unicellular organisms are reproduced this way. For example, sea anemones
reproduce asexually.
Sexual: A reproduction in which two sex cells meet. This reproduction is where a mate is needed. The baby will have
characteristics of both parents. For example, humans reproduce sexually.
This is an asexual reproduction. First, the baby is formed in the
parent. Then, it grows. Third, it starts to separate from the
parent. Last, it totally separates and is a new organism.
In this picture the sex cells
of these two bugs are
meeting so that they can
have a baby. This is a
sexual reproduction.
DNA
DNA stands for deoxyribonucleic acid. DNA determines many characteristics in the living thing. They provide instructions for
creating molecules called proteins.
DNA: DNA is genetic information that is passed from parents to offspring. DNA is found in cells.
This is an example of DNA.
This is another example of DNA that shows you a pattern of DNA.
Energy Use
The cells of organisms use energy to do things that living things must do; such as repair injured parts and grow. Many living
things eat energy (food) and plants go through a process called photosynthesis. Everything you do requires energy. For
most organisms energy comes from the sun directly or indirectly. For example, running requires energy.
Metabolism: The sum of all the chemical activities that an organism performs. When your body metabolizes food it
separates it, sometimes rearranges it and sends it to different parts of the body.
This baby is eating so that he gets
Growth and Development
energy and grows up.
Then he becomes like this and eats more to get more
energy and grow more.
All living things grow and develop during their life. Unicellular organisms develop as the cell increases size, while the
multicellular gets bigger as more cells are produced. Living things don’t just change in size, they also change in their
appearance and internally.
Growth: The process of becoming larger. For example, babies become taller.
Development: The process of change that occurs during an organism’s life to produce a more complex one. For example, a
seed becomes a tree.
In here it shows the
development of a tadpole to a
frog. It comes from an egg,
becomes a tadpole, and slowly
becomes a frog.
This panda will grow to be the size of the
other panda beside it.
Water
Almost all the body of all living things is made up of water. About 70% of each cell is made up of water. Water is needed for
almost all the chemical reactions involved in metabolism. Humans can’t live more than three days without water. Some
animals such as the desert-dwelling kangaroo rat don’t drink water. They get all their water from the food they eats.
These people
are drinking
water and
showing that
everyone and
every living
thing needs
water.
This picture
shows that the
human body is
mostly made
of water.
Air
All living things need air to live. Most living things need oxygen to go through the process in which energy is taken from the
food. Living things that need oxygen to live are called aerobic. The ones that don’t need oxygen to live are called anaerobic.
This an
anaerobic
organism
Underwater volcano animals are anaerobic because they live of what comes out from the volcano and don’t have access to
oxygen..
Both of these living things
are aerobic.
This is a
picture
of air.
A Place to Live
All living things need a place to live. This place must have all the things the living thing needs to survive. Large animals like
elephants need a large space to live, while bacteria need a small place to live. Living things fight for food and territory.
Plants fight for water and sunlight and animals don’t allow other animals to get close to their territory.
All these pictures show living things in their habitats. These are their homes, their places to live and where they should
always be. This will allow them to survive because they will have all they need to live in this place.
These animals all have a place to live so that they can survive.
Food
All living things need food because it gives organisms energy and the raw materials that it needs to carry out life processes.
Producers are living things that create their own food. One example is plants. Consumers are the living things that get food
from other living this. An example is a salamander. Decomposers are consumers that get their food by breaking down the
nutrients of dead living things or organisms. An example is a mushroom.
This bear gets its food from other
living things, like fish. This is why it is
a consumer. It eats food.
Mushrooms are decomposers.
They also eat.
This tree gets its food from the sun.
It produces it. (Producer) It eats food.
Proteins
Carbohydrates
Lipids
Nucleic Acids
ATP
Are the most abundant in the body and cells after water. It is a molecule made up of amino
acids and that is needed to build and repair body structures and to regulate processes in the
body. Some examples are meat and muscle.
Is a class of molecule that includes sugars, starches, and fiber. Cells use it as a kind of energy
and energy storage. When an organism needs energy the cell breaks to release it. There are
simple and complex carbohydrates. An example of simple carbohydrate is a fruit. Some
examples of carbohydrates are bread, rice, pasta, potatoes, and fruit.
A fat molecule that cannot mix with water. Lipids have many important functions in cells.
Some form membranes and others store energy. Some examples are oils, fat, and butter.
Have all the information required for cells to make proteins. They are compounds formed of
subunits called nucleotides. A nucleic acid can have thousands of nucleotides. DNA is a
nucleic acid.
Stands for adenosine triphosphate. It is a molecule that acts as the main energy source for
cell processes. Everything that we eat is ATP because it gives us energy.