Biology – the study of life

Objectives

Define biology.

Describe the seven characteristics of life.

Name and describe the 3 domains and 6 kingdoms of life

What is Biology?

Greek (and Latin) root words:

bios = life & logos = study, so .. Biology means the study of the living world and its organisms. An organism is any living thing.

Greek philosopher to Medieval alchemist to Charles Darwin

The seven characteristics of life

1) All life is made of cells - life has order; most basic.2) Reproduction - life comes from life (biogenesis).3) DNA directs heredity - growth & development.4) Metabolism transforms energy - energy

utilization.5) Homeostasis - maintenance of steady-state

conditions.6) Response to stimuli - organisms sense and react to their environment.7) Evolutionary adaptation - life evolves in response to

interactions between organisms and environment.

All life is made of cells

Cell theory:Φ All organisms are composed of one or more

cells;Φ Cells are the smallest units of life;Φ All cells come from pre-existing cells.

Two types of cellular organization:1) Prokaryotic cells ∙ No membrane-bound organelles ∙ DNA is not separated from

cytoplasm (no nucleus) ∙ Usually very small in size ∙ Describe unicellular bacteria

All life is made of cells

Prokaryotes Usually very small

in size (~1 μm*).

*1 micrometer

= 1 millionth of a meter

(Bacteria on a pinhead)

All life is made of cells

2) Eukaryotic cells

Φ Found in protists, fungi, plants, & animals.

Φ Subdivided by internal membranes

into compartments called organelles.

Φ DNA is segregated

inside a nucleus.

Φ 1000 + times bigger

than prokaryotes.

Φ Unicellular & multicellular forms

All life is made of cells

Although cells can be seen with a light micro-scope, viruses are too small to be seen that way.

(Viruses are not alive – not made of cells.)

All life is made of cells

A comparison of sizeshttp://www.cellsalive.com/howbig.htm

Reproduction

Necessary for survival of every species Φ Sexual reproduction - requires 2 cells

from different individuals. →→ex. egg + sperm (offspring are different from parents)

Φ Asexual reproduction - a single organism reproduces alone.

ex. budding of yeast or splitting of bacteria (offspring are identical

to the parent).

DNA directs heredity

Life contains genetic infor- mation in the form of DNA (deoxyribonucleic acid).

Φ This information is passed from parent to child and is

responsible for all charac-teristics such as hair color,

eye color, body structure, etc.

Metabolism transforms energy

Life uses energy for growth and maintenance.

Φ Def: total sum of all chemical reactions in the body.

ex. Respiration andphotosynthesis

CO2 + H2O → C6H12O6 + O2 :

( Carbon dioxide + water → glucose

+ oxygen )

Homeostasis

From Greek: meaning “Steady state”. Φ Def: The ability to maintain

stable internal conditions, such as body temperature:

perspire to cool & shiver to warm.

Blood capillaries in our skin and muscles can be opened or closed to con-serve or lose heat.

Response to stimuli

Organisms must respond to danger, hunger, cues for reproduction, etc.

Φ Single-celled creatures move toward the food.

Φ Plants grow toward the light. Φ Animals

sense pain.

Evolutionary adaptation

Creatures must “change over time” as the Earth’s environ-

ment changes, or they will die out.

Φ Charles Darwin wrote of this in his book, On the Origin of Species in 1859.

The tree of life

The evolution of life on Earth

over 4 billion yrs

All life fits into 1 of 3 domains

Domains are based on biochemical & genetic differences.

1) Archaea and 2) Bacteria are prokaryotic (all unicellular bacterial

life with no nucleus) 3) Eukarya is eukaryotic (uni- and multicellular organisms with a nucleus.

Animals

Within domains, life fits into 1 of 6 kingdoms

The 6 kingdoms of life

2 kingdoms for prokaryotes (all unicellular) are distinguished by habitat in general.

∙ Archaebacteria (archae = ancient) Domain Archaea

Live in extreme environments similar to early earth:

hot springs, salty seas; oxygen is poisonous.

∙ Eubacteria Domain Bacteria

Live all around us: on the floor, in our mouths,

on our skin, etc.

The 6 kingdoms of life

3 of 4 kingdoms of multicellular eukaryotes are distinguished, in part by nutrition. ∙ Plants are autotrophic (make food by photosynthesis). ∙ Most fungi are decomposers;

they digest food outside their bodies then absorb it.

∙ Most animals digest food within specialized cavities.

All other eukaryotes comprise a group called protists. ∙ All but seaweeds are unicellular (ex: amoeba).