What is Life?

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Friday, April 21, 2023

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What is Life Reading pg.1

In the summer of 1973, thousands of slimy “blobs” appeared in towns near Dallas, Texas. The jelly-like masses overran yards and porches all over the towns. They oozed slowly along the ground. Terrified homeowners didn’t know what the blobs were and some thought they were life forms from a different planet. People around Dallas were worried until Biologists, or scientists who study living things, put their minds at ease.

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What is Life Reading pg.2

The blobs were slime molds – living things usually found on damp, decaying material on a forest floor.

The unusually wet weather around Dallas that year provided ideal conditions for the slime molds to grow in people’s yards.

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Characteristics of Living Things pg.3

If you were asked to name some living things, or organisms, you might name yourself, a pet, and maybe some insects or plants. But you would probably not mention a moss growing in a shady spot, the mildew on bathroom tiles, or a mushroom growing on the lawn. But all of these things are also organisms.

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All of these organisms share six important characteristics with all other living things. All living things have a cellular organization, contain similar chemicals, use energy, grow and develop, respond to their surroundings, and reproduce.

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One way to remember the six characteristics of living things is to use the word “ROGERS.” Can you think of another way to remember the six characteristics of living things?

Respond to surroundings

Organization (of cells)

Grow and develop

Energy use

Reproduce

Similar chemicals


In order for a creature to be classified as a living thing, it must demonstrate all six characteristics.

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All organisms are made of small building blocks called cells. A cell is the basic unit of structure and function in an organism. The smallest cells are so tiny that you could fit over a million of them on the period at the end of this sentence. To see most cells, you need a microscope – a tool that uses lenses, like those in eyeglasses, to magnify small objects.

Cellular Organization pg.6

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A million cells could fit right here!

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Organisms may be composed of only one cell or of many cells. Unicellular, or single-celled organisms, include bacteria. Bacteria are the most numerous organisms on Earth. Each bacterial cell carries out all of the functions necessary for the organism to stay alive.


E. Coli bacteria found in human intestine

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Multicellular organisms are composed of many cells. The individual cells of many multicellular organisms are specialized to do certain tasks. For example you are made of trillions of cells. Specialized cells in your body, such as muscle cells and nerve cells, work together to keep you alive. Some nerve cells carry messages from your surroundings to your brain. Other nerve cells carry messages to your muscle cells, making your body move.


Muscle cells with nerve cell connections

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Like all living things, the butterfly and the leaf are made of cells. Although the cells of different organisms are not identical, they share important characteristics.

In what ways are cells similar?


Animal Cells

Plant Cells

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The cells of all living things are composed of chemicals. The most abundant chemical in cells is water. Other chemicals called carbohydrates (kahr-boh-HY-drayts) are a cell’s energy source. The two types of carbohydrates are sugars and starches. Two other chemicals, proteins (PROH-teenz) and lipids (LIP-idz), are the building materials of cells. This is similar to the way that wood and bricks are the building materials of houses. Lipids are fats (so they can also insulate the organism) and proteins control all the chemical reactions that occur in a living thing.

Chemicals of Life pg.10

Proteins

Proteins Proteins

Lipids

Lipids

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Finally, nucleic acids (noo-KLEE-ik) are the genetic material or DNA. Nucleic acids are the chemical instructions that direct the cell’s activities.

Some types of organisms have RNA as their genetic material. This is very similar to DNA, but is a simpler molecule

Chemicals of Life pg.11

Nucleic AcidDNA

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This is the end of Part one.

You should have completed side one of your notes page.

What is Life?

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