Living Things Review Guide

Living Things Review Guide

by 

Mrs. Kamps' 7th Grade Class 

All living things share six important characteristics:

1. All living things are made of cells.
2. The cells of living things are made of similar chemicals.
3. All living things use energy.
4. All living things grow and develop.
5. All living things respond to their surroundings.
6. All living things reproduce.

Living Things Are Made of Cells

All living things are made of cells. Cells are so small, you need a microscope to see them. Some organisms are made of only one cell and are called unicellular organisms. If a living thing is made of only one cell, that one cell has all of the parts necessary to live. (We will learn more about unicellular organisms when we study pond life.)

Living things that are made of more than one cell are called multicellular organisms. Multicellular organisms often have many, many cells. You are a multicellular organism and your body contains trillions of cells! Each type of cell is responsible for carrying out different functions to keep you alive.

Chemicals of Life

The cells of living things are made of specific types of chemicals.

Water is the most abundant chemical in cells. It is important for you to drink plenty of water throughout the day so that your body's cells can do their work.

Other chemicals in cells include carbohydrates, or carbs, which provide your cells with energy; proteins and lipids, which are the building materials of cells; and nucleic acids, which provide instructions for cellular activities.

Cells Use Energy

The cells of organisms use energy to do what living things must do, such as grow, "breathe," move, think, digest food, and repair injured parts.

Food is your source of energy. It is very important that you eat a nutritious breakfast in the morning so that you can think and work at school. When you do not eat, you will begin to feel tired, irritable, and will have difficulty focusing. You make school harder when you come to school without having had breakfast.

All Living Things Grow and Develop

When living things are born, they will be smaller than their parents.  Over the course of time, the organism will grow larger and larger.  Human babies, for example, are much smaller than adult humans.  It usually takes about eighteen years for a human to grow to full size.  Other organisms grow over relatively short periods of time.  Cats are considered full grown after only one year.

Living things also develop over that course of their lives.  This means that the organism will become more complex.  In the case of an oak tree, it starts out as an acorn and becomes a tree with branches, leaves, a trunk, and a root system underground.  It is a much more complex organism when full-grown than when it first began to grow.

All Living Things Respond to Their Surroundings

All Living Things Reproduce

Because all organisms will die, they must be able to reproduce somehow. Different types of organisms reproduce in different ways. For example, birds lay eggs, plants produce seeds, paramecium buddy up and exchange genetic material, ameba duplicate all of the necessary parts and then split into two.

When an organism reproduces, it creates offspring that are similar to the parents.

Life Comes From Life

Today, we know that living things can only come from other living things. Four hundred years ago, however, people incorrectly believed in spontaneous generation, the idea that nonliving things could produce living things. For example, when meat was left on the counter for days and maggots and flies appeared, people thought that flies came from meat. If great amounts of rain left huge puddles that then became home to frogs, people thought mud puddles produced frogs.

Through careful experimentation, an Italian doctor named Francesco Redi was able to prove that only living things could produce living things. Redi conducted controlled experiments, experiments in which only one variable is changed, to show that spontaneous generation did not occur.

Louis Pasteur also conducted controlled experiments to prove that bacteria could only produce bacteria. As a result of Pasteur's work, we now know it is important to treat milk before it is bottled for stores. Through a process called pasteurization, bacteria in milk is killed before that milk is bottled. Pasteurized milk is safer to drink because it does not contain bacteria that may make you sick.

Part 2: Needs of Living Things

All organisms need four basic things to survive:

1. They need a way to get energy.
2. They need a source for water.
3. They need living space.
4. They need to maintain stable internal conditions.

All Living Things Need Energy

For the cells of living things to carry out their functions, they must have a source of energy. Different types of organisms use different sources for energy.

Some organisms, such as plants, are able to make their own food. They use the energy from the sun to create food through photosynthesis. Organisms that make their own food are called autotrophs. Auto- means "self" and -troph means "feeder." Autotrophs are self-feeders. They do not have to find food to eat, they simply find sunlight to make their own food. The food they produce gives them the energy they need to carry out all of their life functions.

Other organisms, such as people, must eat other things to get the energy they need to survive. Organisms that cannot make their own food are called heterotrophs. Hetero- means "other." If a living thing cannot make its own food, it must eat other things to gain energy for survival.

People are heterotrophs. We eat both autotrophs and heterotrophs for energy. If you sit down to a chicken dinner, you may have salad, rice, and chicken. When you eat the salad and rice, they provide you with energy from plants, or autotrophs. When you eat the chicken, it provides you with energy from a heterotroph, the chicken.

All Living Things Need Water

All Living Things Need a Place to Live

All Living Things Must Maintain Stable Internal Conditions

Because conditions in their surroundings can change significantly, organisms must be able to keep their internal conditions stable. This simply means that inside an organism, its conditions must stay about the same all of the time.

People are able to keep our internal temperature about the same. Our normal body temperature is about 98.6ºF. If our body temperature drops too low, we will begin to shiver as a way of generating heat to get warm. If our body temperature gets too warm, we will sweat. The sweat removes heat from deep within our body so that we cool down.

Other organisms, such as barnacles, have different ways of keeping their internal body conditions the same.  Shore-dwelling barnacles need to be in water to survive.  At high tide, all is well because they are covered in water.  At low tide, when the water goes out from the shore, barnacles are exposed to the sun and are no longer covered in water.  To maintain stable internal conditions, the barnacle can close up its hard outer plates, trapping a bubble of water inside, until high tide returns. 

Chapter Review

Words to Review:

• organism
• cell
• unicellular
• multicellular
• development
• stimulus
• response
• reproduce
• spontaneous generation
• controlled experiment
• variable
• autotroph
• heterotroph