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Transcript
What is science and how is it done?
• What is science?
- Science is the systematic
investigation of phenomena
• How is it carried out?
- The SCIENTIFIC METHOD is the
systematic process by which
such investigations are
conducted
Scientific Method
•
•
•
•
Make an observation
Ask questions about causes
Develop testable hypotheses
Make predictions based on
hypothesis
• Perform experiments to test
hypothesis
We need repeated
observations…replicates!
Select 1 marble = blue
Assumption: all marbles are blue
Sampling error can result
from too few observations!
Select 10 marbles - 3 marbles blue
Assumption: 30% of marbles are blue
A Case Study in Scientific Inquiry:
Investigating Mimicry in Snake Populations
Observation:
1. Dangerous creatures have warning coloration
2. Benign creatures mimic the dangerous
Question: Why?
Hypothesis: Mimicry evolved in harmless species
as an evolutionary adaptation that reduces their
chances of being eaten (Henry Bates)
Fig. 1-25
Scarlet kingsnake (nonpoisonous)
Key
Range of scarlet
kingsnake only
Overlapping ranges of
scarlet kingsnake and
eastern coral snake
North
Carolina
South
Carolina
Eastern coral snake
(poisonous)
Scarlet kingsnake (nonpoisonous)
Field Experiments with Artificial Snakes
• Experimental Design – fake snakes
– An experimental group resembling kingsnakes
– A control group resembling plain brown snakes
• Equal numbers of both types were placed at
field sites, including areas without poisonous
coral snakes
• After four weeks, the scientists retrieved the
artificial snakes and counted bite or claw marks
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
A Case Study in Scientific Inquiry:
Investigating Mimicry in Snake Populations
Hypothesis: Mimicry evolved in harmless species
as an evolutionary adaptation that reduces their
chances of being eaten (Henry Bates)
Hypotheses for this experiment:
H1: The ringed snakes will be attacked less
frequently in the geographic region where coral
snakes were found
Null Hypothesis H0: There will be no difference
Fig. 1-26
(a) Artificial kingsnake
(b) Brown artificial snake that has been attacked
Fig. 1-27
RESULTS
100
84%
Percent of total attacks
on artificial snakes
83%
80
60
40
20
17%
16%
0
Coral snakes
absent
Coral snakes
present
Artificial
kingsnakes
Brown
artificial
snakes
Fig. 1-25
Scarlet kingsnake (nonpoisonous)
Key
Range of scarlet
kingsnake only
Overlapping ranges of
scarlet kingsnake and
eastern coral snake
North
Carolina
South
Carolina
Eastern coral snake
(poisonous)
Scarlet kingsnake (nonpoisonous)
A Case Study in Scientific Inquiry:
Investigating Mimicry in Snake Populations
Hypotheses for this experiment:
H1: The ringed snakes will be attacked less
frequently in the geographic region where coral
snakes were found
Null Hypothesis H0: There will be no difference
Result: The prediction is upheld. The null
hypothesis is not supported, the hypothesis is not
rejected.
Limitations of Science
• repeatable
• peer review
• Old science is replaced by new science when
there is a huge mountain of evidence, not
before.
• Science cannot support or falsify supernatural
explanations, which are outside the bounds of
science
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Theories in Science
• In the context of science, a theory is:
– Broader in scope than a hypothesis
– General, and can lead to new testable hypotheses
– Supported by a large body of evidence in
comparison to a hypothesis
– Vetted
– EXAMPLE: Evolution – the central unifying theory of
Biology and one of the central theories of Geology
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 22-UN1
Observations
Individuals in a population
vary in their heritable
characteristics.
Organisms produce more
offspring than the
environment can support.
Inferences
Individuals that are well suited
to their environment tend to leave
more offspring than other individuals
and
Over time, favorable traits
accumulate in the population.
Fig. 22-2
Big new ideas occur from many smaller breakthroughs
Linnaeus (classification)
Hutton (gradual geologic change)
Lamarck (species can change)
Malthus (population limits)
Cuvier (fossils, extinction)
Lyell (modern geology)
Darwin (evolution, natural selection)
American Revolution
1750
Wallace (evolution, natural selection)
French Revolution
U.S. Civil War
1800
1900
1850
1795 Hutton proposes his theory of gradualism.
1798 Malthus publishes “Essay on the Principle of Population.”
1809 Lamarck publishes his hypothesis of evolution.
1830 Lyell publishes Principles of Geology.
1831–1836Darwin travels around the world on HMS Beagle.
1837 Darwin begins his notebooks.
1844 Darwin writes essay on descent with modification.
1858 Wallace sends his hypothesis to Darwin.
1859 The Origin of Species is published.
Fig. 22-5
GREAT
BRITAIN
EUROPE
NORTH
AMERICA
ATLANTIC
OCEAN
The
Galápagos
Islands
AFRICA
Pinta
Marchena
Santiago
Fernandina
Isabela
Genovesa
Daphne
Islands
Pinzón
Santa
Cruz
Florenza
Santa
Fe
Equator
SOUTH
AMERICA
AUSTRALIA
PACIFIC
OCEAN
San
Cristobal
Cape of
Good Hope
Tasmania
Española
Cape Horn
Tierra del Fuego
New
Zealand
Fig. 22-6
(a) Cactus-eater
(c) Seed-eater
(b) Insect-eater
Evolution
• Evolutionary change is
based on the
interactions between
populations and their
environment
• A population is the
smallest unit that can
evolve
– Individuals are selected
– Populations evolve
Fig. 22-12
(a) A flower mantid
in Malaysia
(b) A stick mantid
in Africa
Organisms are adapted to their
environments – How does this happen?
Evolution via Natural Selection
Observations
• Over production:
Organisms produce
more offspring than
can survive
• Limited Resources:
There usually isn’t
enough to go
around.
Fig. 22-11
Spore
cloud
Evolution via Natural Selection
Observations
• Variation:
– Individuals vary
extensively
(phenotype)
• Inheritance of
Variation:
– Much of this
morphological
variation is
inherited
(genotype)
Fig. 22-10
Evolution via Natural Selection
Inference #1
• Struggle for existence:
production of more
individuals than can
be supported leads to
competition for
recourses
Evolution via Natural Selection
Inference #2
• Survival of the best
adapted: Individuals
with traits that give
them an advantage in
the struggle for limited
resources will survive.
These individuals are
more likely to leave
offspring than
individuals that are less
fit
Evolution via Natural Selection
Inference #3
• Accumulation of
adaptations:The
unequal ability of
individuals to
survive and
reproduce will
lead to a gradual
change in
populations
To sum up…
1. Individuals within species vary
(phenotypic variation)
2. Some of this variation is heritable
(genetic variation)
3. Survival and/or reproduction are
non-random (natural selection)
The individuals that survive & reproduce the
most are those with variations most
suited to their environment
Hawaiian
honeycreepers
Evolution is supported by an
overwhelming amount of scientific
evidence – argued for 250+years
• New discoveries continue to fill the gaps identified by
Darwin in The Origin of Species
• Direct evidence – in the lab and in the field
• Fossil Record
• Molecular
• Homology
• Convergent Evolution
• Ontogeny
Fig. 22-9
DE
Terminal
bud
Cabbage
Lateral
buds
Flower
clusters
Brussels sprouts
Leaves
Kale
Cauliflower
Stem
Wild mustard
Flowers
and stems
Broccoli
Kohlrabi
Fig. 22-3
Layers of deposited
sediment
Younger stratum
with more recent
fossils
Older stratum
with older fossils
Fig. 22-16
Fossils
(a) Pakicetus (terrestrial)
(b) Rhodocetus (predominantly aquatic)
Pelvis and
hind limb
(c) Dorudon (fully aquatic)
Pelvis and
hind limb
(d) Balaena
(recent whale ancestor)
Molecular evidence includes:
Direct sequence similarity
Regulatory genes
Hox gene 6
Hox gene 7
Hox gene 8
Ubx
About 400
mya
Drosophila
Artemia
Fig. 22-17
Morphology: Homologous Structures in mammals
Humerus
Radius
Ulna
Carpals
Metacarpals
Phalanges
Human
Cat
Whale
Bat
Fig. 22-18
Morphology: Ontogeny
Pharyngeal
pouches
Post-anal
tail
Chick embryo (LM)
Human embryo
Fig. 25-19b
Morphology: Ontogeny
Chimpanzee fetus
Chimpanzee adult
Human fetus
Human adult
Fig. 22-20
Sugar
glider
NORTH
AMERICA
AUSTRALIA
Convergent Evolution
Flying
squirrel
Fig. 25-24
Pigmented
cells
Pigmented cells
(photoreceptors)
Epithelium
Nerve fibers
(a) Patch of pigmented cells
Fluid-filled cavity
Epithelium
Optic
nerve
Nerve fibers
(b) Eyecup
Cellular
mass
(lens)
Pigmented
layer (retina)
(c) Pinhole camera-type eye
Optic nerve
(d) Eye with primitive lens
Cornea
Lens
Retina
Optic nerve
(e) Complex camera-type eye
Cornea
The pace of scientific change