Living things

This post is recommended for 4th level.



The most important common characteristic in living things is that all of them do the three functions of life: nutrition, interaction and reproduction.

A cell is the smallest unit of life. Cells can work together in order to create a multicellular organism.

If we focus in the quantity of cells and common characteristics of a living thing, we can divide life into five kingdoms.

THE MONERA KINGDOM

 

They are unicellular organisms. They live in different environments: water, air, ground or inside other living things. The most common organisms are bacteria.

THE PROTIST KINDOM

 

It's the biggest kingdom. They can be unicellular like amoebas. There are unicellular and multicellular algae that make their own food by doing the photosynthesis.

THE FUNGI KINGDOM

 

We find unicellular organisms like yeast. Humans use yeast for doing bread, beer, cakes... Mushrooms and mould are multicellular organisms. 

Fungi organisms cannot make their own food. They take nutrients from dead plants or animals so they are decomposers.

mould

mushrooms

  yeast

THE PLANT KINGDOM

 

Plants are multicellular organisms. All of them can make their own food by the process of photosynthesis so they are producers. They cannot move, but they react to some stimulus like light or humidity.

Plants can be divided into two groups: plants that make seeds and plants that don't make seeds.

THE ANIMAL KINGDOM

 

They are also multicellular organisms. They cannot make their own food so they are consumers. They interact with other animals and the environment and we can divide them into two big groups: vertebrates and invertebrates.

If focus in how they interact with the environment, how energy is transmitted, we find: Producers, consumers and descomposers.

PRODUCERS

They can make their own food, like plants. The most common process is the photosynthesis.
Plants take nutrients and water from the ground through the roots; carbon dioxide from the air and the sunlight through the leaves and make their own food and oxygen which is liberated again to the air.

- CONSUMERS

They take their food from other living organims, like animals. Here we can classify them into three groups:
- primary consumers, who are the hervibores, insects, etc. They take their food from plants.
- secondary consumers, who are little carnivores and little omnivores. They take their food from other animals.
- tertiary consumers, who are big cornivores and detrivores. They take their food from secondary consumers.


- DECOMPOSERS

They take their food from dead plants or animals, like fungi organisms. They break organic cells into simple nutrients.

When all of them interact they compound the food chain.

But sometimes, a same producer or consumer can feed different consumers compounding something more complex: a food web.