Chapter 1An Introduction to Life on Earth

What is Biology?

--- The science of living organisms and life processes.

So what exactly is life?

Life: An evanescent phenomenon dependent for its continued existence, andperpetuation, on cyclic enzymatic reactions in an environment consistingprincipally of protein and water. Student Dictionary of Biology. (1972) Van Nostrand Reinhold Company, New York.

Life: the property by which living organisms are distinguished from dead Organisms or inanimate matter. Websters II New Riverside Dictionary.

These definitions suck terribly.

Neither of the Biology texts (for majors or non-majors) that we use include the term “life” in their glossaries.

The characteristics of life:

1. Complex, organized structure2. Response to stimuli

- a change outside (or inside) leads to another change

3. Homeostasis - the ability to maintain the structure and regulate the internal environment.

4. Ability to acquire material and energy -The material and energy are often transformed

5. Growth6. Reproduction - either sexual or asexual

DNA is genetic information, the “blueprint” for the offspring

7. Ability to evolve - to change to fit the environment

Complex, organized structureThe complexity of life is built in levels.

Fig. 1-8

Each level has ingredients or components which interact to make something greater

than the sum of the parts.

Emergent Properties

Example: NaCl (Sodium Chloride)Sodium = solid metalChlorine = poisonous gas

Put them together = table salt

Biosphere

Ecosystem

Community

That part of Earth inhabitedby living organisms; includes boththe living and nonlivingcomponents

A community together with its nonliving surroundings

Two or more populations of differentspecies living and interacting inthe same area

Earth's surface

snake, antelope, hawk, bushes, grass, rocks, stream

snake, antelope, hawk, bushes, grass

herd of pronghorn antelopePopulation

Members of one species inhabiting the same area

SpeciesVery similar, potentially interbreeding organisms

Fig. 1-1

MulticellularOrganism

Organ System

Organ

Tissue

Cell

A structure usuallycomposed of several tissuetypes that form a functional unit

An individual living thing composedof many cells

Two or more organs working together in the execution ofa specific bodily function

A group of similar cells that performa specific function

The smallest unit of lifenerve cell

nervous tissue

the brain

the nervous system

pronghorn antelope

Fig. 1-1

Organelle

Molecule

Atom

SubatomicParticle

Particles that make up an atom

The smallest particle of an elementthat retains the properties ofthat element

A combination of atoms

A structure within a cell thatperforms a specific function

mitochondrion

water

hydrogen carbon

glucose

chloroplast nucleus

DNA

nitrogen oxygen

electronneutronproton

Fig. 1-1

If you put a plant in your window, the stem will lean in the direction of the sun. This is an example of which characteristic of life?

• Living things are organized.

• Living things respond to stimuli.

• Living things maintain homeostasis.

• Living things need energy.

Response to stimuli

Organisms react to external and internal stimuli.

Some reactions are slow and can’t be seen.

Our body works to keep our temperature at about 98.6ºF. This is an example of which

characteristic of living things?

• Living things are organized.

• Living things respond to stimuli.

• Living things maintain homeostasis.

• Living things need energy.

Homeostasis

-the ability to maintain the structure and regulate the internal environment.

In order to stay alive and function, organisms must keep the

conditions within their bodies fairly constant.

Ability to acquire material and energy

The material and energy are often transformed .

Energy is used to maintain a high level of complexity and

organization, to grow, and to reproduce.

Organisms can take in nutrients (food) for raw materials and energy (heterotrophs)

Or they can use sunlight for energy (photosynthesis) to produce energy-

rich sugar molecules (autotrophs)

The word heterotroph means “other-feeder” or:

• Able to photosynthesize.

• Able to make its own food.

• Must rely on other organisms for energy.

• Make its own energy.

Metabolism changes the raw material and energy into the forms which are

needed for maintenance, growth, reproduction, etc .

Metabolism is basically the sum total of all of the chemical reactions that occur

within an organism.

Growth

All organisms grow during their life

Reproduction

Individuals reproduce their own kind.

The genetic information for “How to build an offspring” is stored in the DNA of the parent(s)

and that information is passed on to the offspring.

Fig. 1.6

Evolution

If the environment changes, then the population of organisms must change

to fit the environment or face the possibility of extinction.

This process of survival of the fittest is natural selection

The evolutionary changes are usually slow, taking several generations and occur by the

accumulation of DNA changes known as mutations.

All life forms have these characteristics in common, yet there is an amazing

diversity in the forms of life on the planet.

All living organisms are organized into groups.

Each of the major organizational groups are called domains

There are two prokaryotic domains; Bacteria and Archaea and a eukaryotic

domain; Eukarya.

Fig. 1.11

In the figure, which organism is most closely related to humans?

• Bacterium

• Protist

• Archaean

• Tree

Figure 1-11

Within the domains are at least 6 groups known as kingdoms

Each kingdom has different attributes which define them. (See table 1-1)

The first difference is cell type

PROKARYOTES EUKARYOTES

No nucleus or nuclear envelope

Nucleus with a nuclear envelope

Genetic material in a “nucleoid region”

Genetic material within the nucleus

No organelles or internal membranes

Contains cytosol with membrane-bound

organelles

Kingdom Cell Type

Bacteria ProkaryoticArchaea ProkaryoticProtista Eukaryotic

Fungi EukaryoticPlantaeEukaryotic

Animalia Eukaryotic

The next property is how many cells the organism has

Single cell (unicellular) or many cells (multicellular)

Kingdom Cell Type

Bacteria ProkaryoticArchaea ProkaryoticProtista EukaryoticFungi EukaryoticPlantae EukaryoticAnimalia Eukaryotic

Kingdom Cell Type Cell Number

Bacteria Prokaryotic UnicellularArchaea Prokaryotic UnicellularProtista Eukaryotic UnicellularFungi Eukaryotic MulticellularPlantae Eukaryotic MulticellularAnimalia Eukaryotic Multicellular

The third attribute in the classification of organisms at the kingdom levels is how the

organism obtains nutrients/energy

Three basic methodsMake food using sunlight - photosynthesisUptake of nutrients by absorption Uptake by eating or ingestion

Kingdom Cell Type Cell Number Nutritional Method

Bacteria Prokaryotic Unicellular Absorp./photosyn.Archaea Prokaryotic Unicellular Absorp./photosyn.Protista Eukaryotic Unicellular Absorp./photosyn./ingestion Fungi Eukaryotic Multicellular Absorption Plantae Eukaryotic Multicellular PhotosynthesisAnimalia Eukaryotic Multicellular Ingestion