Life’s Structure and Classification

Living Things

What are living things like?

• Any living thing is called an organism• Organisms can be different sizes- from

microscopic things like bacteria, to large things like giant oak trees.

• They may behave differently, and have different needs, but there are traits (characteristics) they have in common that distinguish them from non-living things.

Living Things are Organized

• The cell is the smallest unit of structure and function of living things.

• They take in materials from their environment and use them to help the organism function.

• Some organisms are made of as few as one cell, while others are made of complex groups of cells

• Each cell has a structure specific to it’s job, and has within it directions for how to do the job it’s supposed to do.

Living Things Grow and Develop

• Growth in a single celled organism is due to the increase in size of the one cell.

• There is a limit to how large any cell can grow.• Growth in a multi-cellular organism is due to an

increase in the number of cells. • Organisms change as they grow. This is called

development.• How long an organism is expected to live is called

the life span.

Living Things Respond

• Living organisms interact with their environment in order to survive.• A stimulus is anything that causes an

organism to react. • The reaction is known as the response.

Living Things Maintain Homeostasis

• Organisms also respond to stimuli from within them.

• Example: If you are running on a hot day, your body temperature increases. Your body reacts by making you sweat.

• This inner ability of any organism to balance the outside conditions by changing a condition within them is called homeostasis.

• How different organisms do this varies.

Living Things Use Energy

• Carrying on life activities requires energy.• Most organisms get their energy either directly or

indirectly from the Sun.• Some use the Sun’s light directly to make their

own food that they use for energy.• Others don’t have that ability, so they take in

those that do, and use their energy. • Some organisms need oxygen in order to release

the energy from their food, while others don’t.

Living Things Reproduce

• Living things must replace themselves with others that will continue to live after they die. The method by which this happens is called reproduction.

• Not all members of a given type of organism must reproduce, but if NONE of them reproduce, then the organisms will disappear (become extinct).

What do living things need?

• All organisms need a place to live that is suited to their specific survival needs.

• All organisms need to take in water from their environment.

• All organisms need to have sources from which to take in food or make food, that meets the proper amounts and varieties of elements and compounds needed for them to continue to perform the complex chemical activities of life.

Review

• Living things are also known as what?

Living things are also known as organisms.• What traits do all living things share?

All living things are organized, grow and develop, respond to their environment, maintain homeostasis, use energy, and reproduce.• What do all living things need?

All living things need a place to live, water, and a source of food in order to survive.

How are living things classified?

Classification

• Grouping organisms together is known as classification.•Many different systems were used

throughout history until Carolus Linnaeus (Sweden) developed a system in the late 18th century, that is still used today, called Binomial Nomenclature.

Binomial Nomenclature

• Binomial Nomenclature literally means a two-word naming system. (binomial = two names nomenclature = naming system)

• Latin is the language used for the system.• The first word of a scientific name identifies the

organism’s genus – (a group of similar species). • The second word can describe a trait of the

organism, identify a place (usually where it was discovered), or honor an individual (usually the person who discovered it).

Uses of Scientific Names

• Why are Scientific names used? 4 Reasons.

1. They help distinguish between organisms that have similar names.

2. Since organisms with similar evolutionary histories are grouped together, you know which organisms are related.

3. They give descriptive information about a group of organisms.

4. They allow for information to be organized easily and efficiently.

Modern Classification

•Modern scientists use similarities in structure, fossils, hereditary information, and early stages of development to help them determine an organism’s phylogeny, (the evolutionary history of the organism).

Modern Classification

• Domains- Some Scientists believe this should be the largest group, and that all organisms should be divided into three groups. The organisms in a domain have the fewest number of traits in common.

• As you move through the groups, the organisms in that group have more and more in common, and the groups become smaller. Think of it as an upside-down pyramid.

• Kingdom• Phylum• Class• Order • Family • Genus• Species

Modern Classification Continued…

Tools for Identifying Organisms

• Field Guides and Dichotomous Keys are used to identify organisms.

• Field guides usually contain pictures and descriptions of organisms, as well as information about where they live.

• Dichotomous Keys are detailed lists of traits, where you choose between two possibilities, which lead to a conclusion about which organism you’re identifying.

Dichotomous Key Example

Review

**What sorts of questions would show that you really understand the most important concepts in this section? • On looseleaf paper, write 3 questions, and the

answers that go with them, (in complete sentences) from the section of these notes titled “How are Living Things Classified?”

• Be sure to show which is the question, and which is the answer.

• Turn them in when finished.

Classification Lab Conclusion

• On Loose-leaf paper, using the same process that you just used to identify the Kingdom, Phyla and Classes of the shapes in Kingdom1, find and name the Kingdom, Phyla and Classes for the shapes in Kingdom 2. • Label the Class shapes with the letters C

and D.