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Transcript of Biology – the study of lif e. Objectives Define biology. Describe the seven characteristics of...
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).