Chapter 2: Characteristics of Living Organisms

Section 1: Objectives Describe the 6 characteristics of living

things.

Describe how organisms maintain stable internal conditions.

Explain how asexual reproduction differs from sexual reproduction.

Characteristics of Living Things 1.Living things have cells.

Cells: membrane-covered structure that contains all of the materials necessary for life

How many cells do you have? Why are they important?

Characteristics of Living Things 2. Living things sense and respond to

changes in their environment. Stimulus: anything that causes a reaction

or change in an organism or any part of an organism

Stimuli can be: Chemicals Gravity Light Sounds

Characteristics of Living Things Even though an organisms outside

environment may change, their internal environment must remain constant.

Homeostasis: the maintenance of a stable internal environment

Characteristics of Living Things Organisms must respond to external

changes in their environment.

When animals are cold, what is one way that they respond to this change?

When animals are hot, what is one way that they respond to this change?

Characteristics of Living Things 3. Living things reproduce. Organisms make other organisms similar

to themselves.

They do this in one of 2 ways: Sexual reproduction: 2 parents produce

offspring Asexual reproduction: single parent

produces offspring

Characteristics of Living Things 4. The cells of all living things contain DNA

(deoxyribonucleic acid)

When organisms reproduce, they pass copies of their DNA onto their offspring.

Characteristics of Living Things 5. Organisms use energy to carry out the

activities of life.

These activities include: Making food Breaking down food Moving materials into and out of cells

Metabolism: the sum of all chemical processes that occur in an organism

Characteristics of Living Things

Characteristics of Living Things 6. Living things grow and develop.

Whether an organism is unicellular or multicellular, it grows and develops.

In addition to getting larger, living things may develop and change as they grow.

Chapter 2 Section 1 Review Questions 1)List the 6 characteristics of living things. 2) Give 4 examples of stimuli. 3) Does an organism want its internal

environment to change? Explain your answer.

4) T/F Organisms must never respond to changes in their external environment. Explain your answer.

5) What do organisms use energy to do? 6) T/F Living things grow and develop.

Section 2: Objectives Explain why organisms need food, water,

air, and living space.

Describe the chemical building blocks of cells.

Section 2: The Necessities of Life Living organisms need many things in

order to survive: Water Air Shelter Food

The Necessities of Life 1. Water

Your cells are made up to 70% water.

Most of the chemical reactions in your body require water.

Different organisms require different amounts of water.

The Necessities of Life 2. Air

Air is a mixture of several different gases, including oxygen and carbon dioxide.

Organisms living on land get oxygen from air.

Organisms living in water take in dissolved oxygen or come to the water’s surface to get oxygen from the air.

The Necessities of Life 3. Shelter

All organisms need a place to live that contains everything they need to survive.

Space on Earth is limited.

What does this mean for organisms?

The Necessities of Life 4. Food All living things need food. Food gives organisms energy to carry on

life processes.

Not all organisms get food the same way: Producers: make their own food Consumers: eats other organisms or organic

matter Decomposer: eats dead/decaying organisms

The Necessities of Life Nutrients are made up of molecules.

A molecule is a substance made up of one or more atoms.

Molecules of different atoms combine to make compounds.

Atoms Molecules Compounds

The Necessities of Life Almost all life processes of a cell involve

proteins.

Proteins: molecules made up of amino acids Amino acids are the subunits of proteins.

Some proteins are made up of only a few amino acids, while others are made up of many.

The Necessities of Life Molecules made up of sugar are called

carbohydrates.

Cells use carbohydrates as a source of energy and for energy storage.

Simple carbohydrates are made up of one or a few sugar molecules linked together.

Complex carbohydrates are made of hundreds of sugar molecules.

The Necessities of Life Lipids: compounds that cannot mix with

water

Lipids store energy and form the membranes of cells.

Phospholipids as well as fats and oils are classified as lipids.

The Necessities of Life The head of a phospholipid is attracted to

water but the tail is not.

Hydrophilic: attracted to water (“water-loving”)

Hydrophobic: not attracted to water(“water-hating”)

The Necessities of Life

The Necessities of Life ATP: Major energy carrying molecule of

the cell.

Energy in carbohydrates and lipids must be transferred to ATP.

This then fuels the cell.

ATP: Adensosine Tri-Phosphate

The Necessities of Life Nucleic acids: “Blue-prints” of life.

Contain all information needed for a cell to make proteins.

Made up of nucleotides.

Example: DNA