Great Ideas in Science
Lecture 10 - Living Things
Prof. Robert Hazen
UNIV-301
Every Living thing…
1. Can be classified in one scheme
2. Is modular – composed of a few
simple molecules
3. Is made of cells – life’s chemical
factories
4. Uses the same genetic code
5. Evolved from a first cell by natural
selection
6. Lives in ecosystems of many
interdependent organisms
Ways of Thinking
About Living Things
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Biosphere
Ecosystem
Community
Population
Organism
Anatomy &
physiology
 Cellular
 Molecular
What is Life?
 Encapsulation: All life is separated
from the environment by a
membrane.
 Metabolism: All life obtains energy
and atoms from the environment.
 Reproduction: All life reproduces
via genetics.
The Characteristics of Life
 High degree of order and complexity
 Part of larger systems of matter and energy
 Life depends on chemical reactions in cells
 Life requires liquid water
 Organisms grow and develop
 Regulate energy use
 Share same genetic code, code is heritable
 All living things are descended from a
common ancestor
Great Idea: Living things use many different
strategies to deal with the problems of
acquiring and using matter and energy.
 Linnaean classification
 Hierarchy
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Kingdom
Phylum
Class
Order
Family
Genus
Species
Why is Taxonomy Important?
Think about how to describe a tree.
Names are essential for accurate
communications
But taxonomy can be rather
arbitrary
 Lumpers versus splitters
 Local variations in species
Why is Taxonomy Important?
Dracorex (top left) and Stygimoloch (top right),
as growth stages of Pachycephalosaurus (bottom).
Why is Taxonomy Important?
A
B
C
Classifying Life
 Kingdoms
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Monera
Protista
Fungi
Plants
Animals
Taxonomy of Animals
Classifying Human Beings
 Kingdom: Animals
 Phylum: Chordates
 Subphylum: vertebrates
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Class: Mammals
Order: Primates
Family: Hominid
Genus: Homo
Species: sapiens
A New View:
Three Domains of Life
 Bacteria
 Archaea
 Eukarya
Implications of
Linnaean Classification
 You can use genetic material.
 Similarities depend on time and change.
 Classification results from real events.
“Nothing in biology
makes sense except in
the light of evolution.”
Strategies of Fungi
 Growth
 Filaments
 Decomposers
 Structure
 Mass of filaments
 Many forms
 Reproduction
 Break filaments
 Spores (usually asexual)
 Lichens
 Fungi + Algae
 Two interdependent
species
The Simplest Plants
 Phylum: Bryophytes
 Structure
 No roots
 Photosynthetic
 Reproduction
 Sexual
 Asexual
Vascular Plants
 Phylum: vascular plants
 Structure
 Roots, stems, leaves
 Control water loss
 Reproduction
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Spore = fertilized egg
Cone = holds egg or sperm
Seed = egg plus nutrients
Pollen = sperm
 Strategies
 Seedless (Ferns - spores)
 Seeds but no flowers
(Gymnosperms - cones)
 Seeds and flowers
(Angiosperms)
Angiosperms
Invertebrates
 No backbone
 Most diverse animals
 Arthropods
 70% of known animal
species
 Structure
 Exoskeleton
 Jointed legs
The Molecules of Life
All life is modular – composed
of a few simple molecules.
Key Ideas about the
molecules of life
 Based on Carbon (Organic chemistry)
 Six main elements (CHNOPS)
 Modular; built from simple units
 Molecular shapes determine their function
Nutrition Facts
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Energy
Lipids
Sugars
Amino acids
Carbohydrates (sugars)
Carbon
Hydrogen
Oxygen
Cellulose and Starch
Lipids
Saturated and
Unsaturated Lipids
Amino Acids
 Amino group
 Carboxyl group
 Side-group (20
different things)
Protein – sequence of
amino acids
 Primary – chain of
amino acids
 Secondary – folding of
chain
 Tertiary
 Quaternary
Proteins
 Structural role
Proteins – Enzymes
Dietary Amino Acids