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CHAPTER 1 Introduction: Themes in the Study of Life
1. Unifying Themes in Biology
2. Evolution and the Diversity of Life
3. The Process of Scientific Inquiry
1. Unifying Themes in Biology
Chapter Reading – pp. 1-9
Characteristics of Life
Order
Response to the environment Evolutionary adaptation
Regulation
Reproduction Energy processing Growth and development
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Levels of Biological Organization The biosphere Tissues Ecosystems
Organs and organ systems
Communities Cells Organelles
Organisms Atoms
Populations Molecules
Cycling of Chemical Nutrients
Leaves absorb Sunlight light energy from Leaves take in the sun. carbon dioxide from the air CO and release 2 oxygen.
O2
Cycling of chemical nutrients
Animals eat Leaves fall to Water and leaves and fruit the ground and minerals in are decomposed the soil are from the tree. by organisms taken up by that return the tree minerals to the through soil. its roots.
Energy Flow through Ecosystems
SUNLIGHT HEAT
When energy is used Producers absorb light to do work, some energy and transform it into energy is converted to chemical energy. thermal energy, which is lost as heat.
An animal’s muscle cells convert Chemical chemical energy energy from food to kinetic energy, the energy of motion. A plant’s cells use chemical energy to do Chemical energy in work such as growing food is transferred new leaves. from plants to consumers.
(a) Energy flow from sunlight to (b) Using energy to do work producers to consumers
Energy flow through ecosystems is one way: sunlight producers consumers … HEAT
HEAT HEAT
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Structure Correlates w/Function
(a) Wings (b) Bones Infoldings of membrane
Mitochondrion
100 µm 0.5 µm (c) Neurons (d) Mitochondria
Cells are the Basic Unit of Life Prokaryotic cell Eukaryotic cell DNA (no nucleus) Membrane Membrane Cytoplasm
Organelles Nucleus (contains DNA) 1 µm
DNA is the Basis of Inheritance Nucleus DNA
Nucleotide
Cell
(a) DNA double helix (b) Single strand of DNA
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Sexual Reproduction provides Genetic Diversity
Sperm cell
Nuclei containing DNA
Fertilized egg Embryo’s cells with with DNA from copies of inherited DNA Egg cell both parents Offspring with traits inherited from both parents
Sexual reproduction involves the union of gametes • seen in the Kingdoms Animalia, Plantae, Fungi
A Negative Regulation of feedback Enzyme 1
Biological B D Enzyme 2 Excess D blocks a step Processes D D C
Enzyme 3 Negative Feedback D
• counteract change in (a) Negative feedback
order to restore original W
state Enzyme 4
X Positive Positive Feedback feedback + Enzyme 5
• proceed further in Excess Z Z Y stimulates a Z step direction of change Z Enzyme 6 toward new state Z
(b) Positive feedback
2. Evolution & the Diversity of Life
Chapter Reading – pp. 10-14
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Classification by Taxonomy
Species Genus Family Order Class Phylum Kingdom Domain
Ursus americanus (American black bear)
Ursus
Ursidae
Carnivora
Mammalia
Chordata
Animalia
Eukarya
The Domains of Life
(a) Domain Bacteria (b) Domain Archaea
m
m
2 2 2 2
(c) Domain Eukarya Kingdom Animalia
100 m
Kingdom Plantae
Protists
Kingdom Fungi
Diversity via Evolution Evolution explains the diversity of life, both past and present
• first proposed by Charles Darwin and Alfred Wallace
• descent with modification through Natural Selection explains the diversity of life today as well as the fossil record
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The Process of Natural Selection
1 Population with 2 Elimination of 3 Reproduction of 4 Increasing varied inherited individuals with survivors frequency of traits certain traits traits that enhance survival and reproductive success
• selective factors in the environment favor the survival of individuals with certain traits and the
transmission of those traits to the next generation
Warbler finches Insect Green warbler finch
Certhidea olivacea
- eaters
COMMON Gray warbler finch
ANCESTOR Seed Certhidea fusca -
eater Sharp-beaked ground finch
Bud Geospiza difficilis -
eater Vegetarian finch Platyspiza crassirostris
Mangrove finch
Cactospiza heliobates
Insect Tree finchesTree Woodpecker finch
- Cactospiza pallida eaters
Medium tree finch Camarhynchus pauper Large tree finch Camarhynchus psittacula Small tree finch Camarhynchus
parvulus Cactus Large cactus
eaters ground finch - flower Geospiza conirostris
rud finchesGround Cactus ground finch Seed
- Geospiza scandens
- eaters Small ground finch Geospiza fuliginosa
Medium ground finch Geospiza fortis
Large ground finch Geospiza An Evolutionary Tree magnirostris
3. The Process of Scientific Inquiry
Chapter Reading – pp. 16-21
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The Scientific Method Observation > Hypothesis > Experiment > Conclusion • scientific investigation begins with an observation that leads to a question (ideally “Yes/No”)
e.g., “Does vitamin D help prevent colds?”
A good hypothesis is a statement that: • predicts an answer to the question of interest • contains only objective, well-defined terms • can be tested or challenged experimentally “People who take vitamin D are less likely to get colds.” *A good hypothesis doesn’t have to be correct, just testable!*
Variables in Experiments Hypotheses are tested experimentally, and experiments contain variables: Independent Variable (IV) • the single factor that varies in an experiment • e.g., whether or not one takes a vitamin D supplement Standardized Variables (SV) • all other factors that remain constant • e.g., age, gender, location, stress level, etc. Dependent Variables (DV) • outcome being measured or recorded • e.g., occurrence of colds
Experimental Design Observation Ideally experiments have 1 independent variable.
Question • in this way any changes in the
results (dependent variable) can be Hypothesis #1: Hypothesis #2: Dead batteries Burnt-out bulb attributed to the single IV you tested
Prediction: Prediction: Replacing batteries Replacing bulb • >1 IV makes it unclear which IV will fix problem will fix problem affected the DV!
e.g., if she changes both the batteries and the bulb (2 IVs), she won’t be able to Test of prediction Test of prediction determine which, if either, wasn’t working
***In an experiment, the IV is tested for Test does not Test falsifies hypothesis its effect on the DV*** falsify hypothesis
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Control Experiments
Every experiment should ideally include a test in which the IV is set to zero or some default value, a test referred to as a control: • leave out the IV (e.g., no Vitamin D)
• if IV can’t be left out (e.g., temperature), set it to a default or background level (e.g., room temperature)
This sort of test is also called a negative control. Positive controls (tests that give a known positive result) are also appropriate for some experiments.
***Controls provide a reference for comparison in addition verifying that the experimental results are reliable***
Interpreting Experimental Results
Experimental results (data) are then interpreted to either support or disprove the hypothesis:
• a hypothesis can never be proven, only supported
• an experimental result that is inconsistent with a hypothesis reveals it to be incorrect!
Scientific Theories • in contrast to a hypothesis, a theory is a very general, broad concept that is supported by a vast body of evidence and experimentation • e.g., “Theory of Evolution”, “Cell Theory”, “Germ Theory”
Case Study in Scientific Inquiry Scarlet kingsnake (nonpoisonous) Key Range of scarlet kingsnake only Overlapping ranges of scarlet kingsnake and eastern coral snake
North Carolina Eastern coral snake (poisonous) South Carolina
Scarlet kingsnake (nonpoisonous)
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Testing the Hypothesis
experimental group Hypothesis:
“Kingsnake mimicry of coral snakes provides protection from predators only within the coral snake (a) Artificial kingsnake habitat.” control group Experiment (test): Plant equal amounts of fake kingsnakes and control snakes in habitats with and w/o coral snakes, determine percent of (b) Brown artificial snake that has been attacked fake snakes attacked.
Results and Conclusion
RESULTS 100 Artificial kingsnakes 83% 84% 80 Brown artificial snakes Hypothesis 60 supported!
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on artificial snakes artificial on Percent attacks total Percent of 20 17% 16%
0 Coral snakes Coral snakes absent present
Key Terms for Chapter 1
• homeostasis • hypothesis vs theory • variables: independent, dependent, standardized • positive & negative control experiments
Relevant Chapter Questions 1, 2, 5-8, 10
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