Download Introduction: Themes in the Study of Life

8/17/2011
Chapter 1
• Biology is the scientific study of life
Introduction: Themes in
the Study of Life
• Biologists ask questions such as:
– How a single cell develops into an organism
– How the human mind works
– How living things interact in communities
The biosphere
Life- studied at different levels of biological
organization
Ecosystems
Communities
Populations
Organisms
The hierarchy continues downward with
Organ systems
Organs and
organ systems
Cells
10 µm
Cell
Organs
Organelles
Tissues
Cells
1 µm
Organelles
Molecules
Atoms
Tissues
50 µm
Molecules
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Fig. 1-5
Sunlight
Ecosystem
• Living organisms and their environments form
interconnecting webs
– Cycling of nutrients- soil to plants to soil
Cycling
of
chemical
nutrients
Producers
(plants and other
photosynthetic
organisms)
Heat
Chemical energy
– Flow of energy- sunlight to producers to
consumers
Consumers
(such as animals)
Heat
Cell
Cell- lowest level of organization that can perform
all life activities
Prokaryotic cell
Eukaryotic cell
• Eukaryotic cell
Membrane
DNA
(no nucleus)
Membrane
Cytoplasm
• Prokaryotic cell
Organelles
Nucleus (contains DNA)
1 µm
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DNA- the genetic information
• Chromosomes contain DNA
• DNA is the substance of genes
• Genes transmit information from parents to
offspring
• An organism’s genome is its entire set of
genes
Nucleus
DNA
Feedback Mechanismsself-regulate biological systems
Nucleotide
Cell
(a) DNA double helix
(b) Single strand of DNA
Feedback mechanisms self-regulate biological
systems
Fig. 1-13a
Negative Feedback
A
–
Enzyme 1
• Negative feedback
B
• Positive feedback
D
Excess D
blocks a step
D
Enzyme 2
D
C
Enzyme 3
D
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Fig. 1-13b
Diversity of Life
W
Enzyme 4
Positive Feedback
X
+
Enzyme 5
Excess Z
stimulates a
step
Z
Y
Z
Z
• 1.8 million species have been identified
–
5,200 prokaryotes
–
100,000 fungi
–
290,000 plants
–
50,000 vertebrates
–
1 million insects
Enzyme 6
Z
Species Genus Family Order
Class Phylum Kingdom Domain
Ursus americanus
(American black bear)
• Taxonomy
Ursus
Ursidae
Carnivora
Mammalia
Chordata
Animalia
Eukarya
The diversity of life can be arranged
into three domains
Domain Bacteria and domain Archaea
comprise the prokaryotes
Domain Eukarya includes
Protists (protozoans and algae, falling into multiple
kingdoms)
The kingdoms Fungi, Plantae, and Animalia
Domain Eukarya all eukaryotic organisms
275
Kingdom Fungi
Kingdom Animalia
Protists
(multiple kingdoms)
Figure 1.5C
Kingdom
Plantae
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Evolution explains the unity and diversity of life
Charles Darwin
Synthesized the theory of evolution by natural
selection
• Charles Darwin published On the Origin of
Species by Means of Natural Selection in 1859
• Darwin made two main points:
– Species showed “descent with modification”
from common ancestors
– Natural selection is the mechanism
Figure 1.6A
• Darwin observed that:
– Individuals have traits that vary
• Darwin inferred:
– Many traits are heritable
– More offspring are produced than survive
– Individuals best suited to their environment will
survive and reproduce
– Over time, more individuals will have these
traits
– Competition is inevitable
– Species suit their environment
• The natural environment “selects” for beneficial
traits
Fig. 1-22
Insect-eaters
Warbler finches
Green warbler finch
Certhidea olivacea
Gray warbler finch
Certhidea fusca
Bud-eater
Seed-eater
COMMON
ANCESTOR
Sharp-beaked
ground finch
Geospiza difficilis
Vegetarian finch
Platyspiza crassirostris
Mangrove finch
Cactospiza heliobates
Tree finches
Insect-eaters
Woodpecker finch
Cactospiza pallida
Data and the Scientific Method
Medium tree finch
Camarhynchus pauper
Large tree finch
Camarhynchus
psittacula
Small tree finch
Camarhynchus
parvulus
Cactus-flowereaters
Seed-eaters
Ground finches
Large cactus
ground finch
Geospiza conirostris
Cactus ground finch
Geospiza scandens
Small ground finch
Geospiza fuliginosa
Medium ground finch
Geospiza fortis
Large ground finch
Geospiza magnirostris
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Types of Data
Data fall into two categories
– Qualitative
• Inductive reasoning draws conclusions
through the logical process of induction
– Quantitative
Scientific method
• Deductive reasoning draws conclusions from
the general to the specific
Observations lead to ask questions and propose
explanations- hypothesis
... leads to predictions that can be tested by
observation or experimentation
Observations
• For example,
Question
– Observation: Your flashlight doesn’t work
– Question: Why doesn’t your flashlight work?
– Hypothesis 1:
Hypothesis #1:
Dead batteries
Hypothesis #2:
Burnt-out bulb
Prediction:
Replacing batteries
will fix problem
Prediction:
Replacing bulb
will fix problem
– Hypothesis 2:
– Both these hypotheses are testable
Test prediction
Test prediction
Test falsifies hypothesis Test does not falsify hypothesis
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