The World of Living Things

The World of Living Things

from the Biology: The Science of Life Series

The Characteristics of Living Things

1. LIVING THINGS ARE MADE FROM THE SAME BASIC CHEMICAL INGREDIENTS.

All livingthings are composed of complicated chemical substances not found in non-living things such as rocks. For example, ORGANISMS store biological information in long, twisted, chemical chains known asNUCLEIC ACIDS. The nucleic acid called DNA is by far the most common information-storing chemical. The information stored in DNA contains instructions that control all life processes.

2. LIVING THINGS ARE COMPOSED OF CELLS.

Cells are the basic structural units, or "buildingblocks," of life. Cells are made from precisely arranged chemical ingredients.

3. LIVING THINGS REQUIRE WATER AND A SOURCE OF ENERGY TO RUN THEIR LIFE PROCESSES.

Plants, for example, capture energy from the sun and use it to combine nonliving carbondioxide gas and water into sugars which chemically store the energy. Animals cannot capture thesun's energy directly, but they can eat plants, plant products, or even other animals and get the energythey need in those ways. Living things are also able to METABOLIZE food to release and use itsstored energy.

4. LIVING THINGS HAVE THE ABILITY TO REPRODUCE AND GROW.

This means that living thingsproduce offspring so that their SPECIES will survive for one more generation. This characteristic alsomeans that small organisms that are in the early stages of life can grow and become larger.

5. LIVING THINGS HAVE LIMITED LIFESPANS.

This means that all organisms eventually wear outand die. In this way, old, worn out creatures are replaced by healthy young ones. Dead organisms alsobecome food for other organisms, and as they decay, they enrich the soil.

6. LIVING THINGS CAN RESPOND TO THEIR SURROUNDINGS.

Being able to respond to dangerand locate food are two obvious examples of this trait. But another important way organisms respondto their surroundings is by maintaining a balanced environment inside their bodies when the outsideenvironment changes, a process known as HOMEOSTASIS. A good example of homeostasis is theability of warm-blooded animals to maintain a constant body temperature even though the outside temperatureis changing all the time.

7. LIVING THINGS HAVE THE ABILITY TO MOVE.

The lives of many organisms depend on beingable to move to capture food and to escape from danger. Obviously some organisms move around alot and can do so quite quickly, whereas most plants move so slowly their movements are hard to see,for example, when leaves move toward sunlight or when a flower opens.

8. LIVING THINGS ARE ABLE TO REPAIR INJURIES TO THEMSELVES (provided the damage is not too severe).

The world is a dangerous place and without the ability to repair wounds, huge numbersof creatures would die before they ever reach adulthood.

9. LIVING THINGS CAN UNDERGO CHANGE OVER TIME.

This means that species of living thingsare constantly ADAPTING to meet the challenges of their environments. Through ADAPTATION,species of organisms have been able to develop valuable traits that allow them to survive where othersdie. This is the main reason why there are so many different kinds of living things on earth.

The World of Living Things

from the Biology: The Science of Life Series

The Characteristics of Living Things

THE CHARACTERISTICS OF THE FIVE KINGDOMS OF LIVING THINGS

KINGDOM MONERA

• The very simplest living things belong to the KINGDOM MONERA. Many monerans are of microscopicsize. All monerans are UNICELLULAR, meaning they possess just one cell. Moneran cells areunique because they LACK A NUCLEUS. The other characteristic of monerans is that their cells aresurrounded by a thick outer CELL WALL. Cell walls are found only in monerans, fungi and plants. Some monerans are AUTOTROPHIC (make their own food) some are HETEROTROPHIC (cannot make food). Examples of monerans are bacteria and blue-green algae. There are about 3,000 speciesof monerans.

KINGDOM PROTISTA

• Members of the KINGDOM PROTISTA are microscopic plant-like and animal-like creatures that areoften referred to as PROTOZOA. The Kingdom Protista has about 30,000 species. All protists are UNICELLULAR. They HAVE A NUCLEUS but LACK CELL WALLS. Like the monerans, some protists areAUTOTROPHIC and some are HETEROTROPHIC.

KINGDOM PLANTAE

• The members of the KINGDOM PLANTAE, the plants, are MULTICELLULAR organisms. This meansthey are made from many cells. Plant cells HAVE A NUCLEUS AND CELL WALL. Plants areAUTOTROPHIC and are able to use the sun's energy to make their own food. There are about285,000 species of plants.

KINGDOM FUNGI

• The members of the KINGDOM FUNGI, the mushrooms, molds and yeasts, are also MULTICELLULARorganisms. However, unlike plants, fungi are HETEROTROPHS and cannot make their ownfood. Fungi cells HAVECELLWALLS and almost always HAVE MORE THAN ONE NUCLEUS. Thereare about 100,000 species of fungi.

KINGDOM ANIMALIA

• The KINGDOM ANIMALIA is the biggest one. There are over one million species of animals. Animalsare HETEROTROPHS and cannot make their own food. Like plants and fungi, animals are MULTICELLULARorganisms. Animal cells LACK CELL WALLS but HAVE A NUCLEUS.

The World of Living Things

from the Biology: The Science of Life Series