An Introduction to Life

Objectives:

• Explain the basic characteristics shared by all living things.

• Identify the levels of organization found in living organisms.

• Explain the system of classification used for living organisms.

A living thing is called an:

Organism

Unity and Diversity of Life

Organisms:

• Share characteristics that distinguish them from non living things (Unity of Life)

• Show tremendous differences in form and function (Diversity of Life)

All Living Things:

• Are Organized

• Acquire Materials and Energy

• Respond to changes in their environment

• Reproduce and Develop

• Have Adaptations

• Have Nucleic Acids as a way to control activities.

All living things:Are made up of one or more cells.• The cell is the smallest unit that can be

said to be alive

• All cells are complex, highly organized, and contain many different types of chemicals or molecules.

These chemicals are made up of smaller units – atoms

• Unicellular organisms have only one cell.

• Multicellular Organisms have more than one cell.

In Multicellular Organisms:

• Similar cells form tissues

• Tissues combine to form organs

• Organs work together in organ systems

• Organ systems form a complex organism.

Levels of Organization:

All Living Things:

Acquire Materials and Energy

• Metabolism is the sum of all the chemical reactions in an organism

• During metabolism an organism will build up molecules or break them down

• Energy is needed to carry on all life functions

All Living Things:

Acquire Materials and Energy• Source of most energy on Earth:

The SUN• Plants create nutrients from the

sun’s energy during photosynthesis

• Other organisms consume plants and animals to get their nutrients.

All living things:

Maintain an internal balance

• Homeostasis – attempt by the organism to maintain its internal conditions as the external environment changes

• Temperature, water, acidity and level of nutrients need to be regulated

All Living Things

Respond to their Environment• External changes:

light, temperature, moisture, gravity

• Internal changes: sugar levels, salt concentration, carbon dioxide levels, temperature

• Includes behavior and instinct

All Living Things• Reproduce and Develop

Asexual reproduction – One parent

Sexual reproduction – Two parents

All Living Things• Have Adaptations

– Modifications that allow them to survive in their environment

All Living ThingsHave Adaptations• Modified over time by natural selection• Preserves genetic changes• Makes them better suited for their environment.

All Living Things

Have Adaptations• Evolution is descent

with modification, driven by natural selection

• One species can be an ancestor to many species

• Explains diversity and unity

All Living Organisms• Have Nucleic Acids to control activities

– DNA (deoxyribonucleic acid) or – RNA (ribonucleic acid) – Contain instructions for the cell– Carry hereditary information to next generation

Organizing Life

• Because living things are diverse, taxonomy was created to group organisms into categories and to understand their evolutionary relationships.

Least inclusive

Most inclusive Domain Kingdom Phylum Class Order Family Genus Species

Organizing Life - Domains

• Three domains:– Archaea– Bacteria– Eukarya

• Based on Cell Structure and Function– Prokaryotic cells do not have a true nucleus– Eukaryotic cells have a membrane around

their nucleus

Organizing Life - Domains

• Archaea and Bacteria are both comprised of prokaryotic bacteria.

• Archaea bacteria live in extreme environments.– Anoxic (no oxygen)– High salinity– High temperature

• Bacteria Domain includes most pathogenic bacteria

Organizing Life - Domains

• Eukarya consists of all non-bacterial organisms.

• Eukarya is divided into four kingdoms.– Protista– Fungi– Plantae– Animalia

The four kingdoms of Eukarya

Organizing Life – Scientific Names

• Unique scientific names are used to identify and classify organisms.

• The scientific name is called the binomial name and consists of a genus and species.– Peas: Genus = Pisum; species = sativa

• Pisum sativa

– Humans: Genus = Homo; species = sapiens• Homo sapiens

Can you:

• Explain the basic characteristics shared by all living things?Are Organized

Acquire Materials and EnergyRespond to changes in their environment

Reproduce and DevelopHave Adaptations

Have Nucleic Acids as a way to control activities

Can you:

• Identify the levels of organization found in living organisms?

AtomsMolecules

cells tissuesorgans

organ systemscomplex organism

Can you:

• Explain the system of classification used for living organisms?

Domain

Kingdom

Phylum

Class

Order

Family

Genus

Species

Largest group

Smallest group