Populations
individuals of the same species that live in the same area at the same time
Believes of special creation
1) all species are independent of one another
2) life on Earth is young (6000 years old)
3) species are immutable
Immutable
incapable of change
special creation thought this
Pattern component
part of a scientific theory
a statement that summarizes a series of observations about the natural world
about facts or how things ARE in nature
Process component
part of a scientific theory
a mechanism that produces a pattern or set of observations
Scientific theory
a broad class of observations that is widely supported by overwhelming evidence
Plato and Typological Thinking
Plato claims that every organism was an example of a perfect essence, or type, created by God and that this type was unchanging
Plato explained slight variations as “perfect essence”
Aristotle and the Scale of Nature
Linear scheme of species arranged in increasing size and complexity
“lower” and “higher” species
Lamarck
proposed the first formal theory of evolution
believed that species were always producing “better” species
phenotype develops in response to environment (ex: giraffes neck grows)
Evolution
species are not static, but change over time
What was different about Darwin?
He claims that variation is crucial
Population thinking
variation is key
Typological thinking
variation is abnormal
species conform
the opposite of population thinking
3 things that make Darwin’s ideas revolutionary
1) overturned the idea that species are static and unchanging (suggested change through time and common ancestry)
2) replaced typological thinking with population thinking
3) it was scientific. can make predictions through observation and experimentation
Descent with modification
species that lived in the past are the ancestors of the species existing today, and that species change through time
Pattern component of the theory of evolution
1) species change through time
2) species are related by common ancestry
Evidence for change through time (show change)
fossils, extinction, transitional features
vestigial traits
contemporary populations: like bacterial resistance and weeds resistance to herbicides
fossil
any trace of an organism that lived in the past
fossil record
consists of all the fossils that have been found on Earth and described in scientific literature
extant species
species living today
James Hutton
geologist
principle of uniformitarianism: the idea that geological processes occurring today are what occurred in the past
sedimentary rocks
form from sand or mud and other materials deposited in layers at locations such as beaches or river mouths
take long to form
geologic time scale
a sequence of named intervals called eons, eras, and periods that represent major events in Earth’s history
a relative scale (exact age unknown)
radioactive decay
half-life can function as an absolute dating
“natural clock”
Earliest signs of life
3.4-3.8 billion years
Baron Cuvier
published report that there are extinct species
his report focused on large species like mammoths because it is very unlikely that these large, distinctive terrestrial animals would remain undiscovered if alive
law of succession
pattern of finding fossils of species with similarities to the living species succeeding them
Darwin connects that extinct forms are the ancestors of living forms
transitional feature
a trait in a fossil species that is intermediate between those of ancestral and derived species
Derived traits
a trait that differs from the ancestral trait
Ancestral trait
a trait present in the ancestor of the species
Is evolution goal-oriented or purposeful?
No
Are individual fossils direct ancestors of later species?
Not necessarily
The individual fossil could be a relative of the direct ancestor
vestigial trait
a reduced or incompletely developed structure that has no function but is clearly similar to functioning organs in ancestral species or closely related species
Vestigial traits and special creation
special creation is disproved by vestigial traits because they show that species were not perfectly designed by a supernatural being
Contemporary examples of change through time
Bacteria resistance
Herbicide resistance
Timing of bird migration and flower bloom due to climate change
Evidence of descent from a common ancestor (shows relationships)
similar species are found in the same geographic area
similar species share homologies
current examples
geographic similarities
Darwin discovered that the finches were distinct species on different islands but yet still very similar
Darwin proposes that the finches were similar because they had descended from the same common ancestor and then changed over time
phylogenetic tree
a branching diagram that describes the ancestor-descendant relationships among species or other taxa
homology
a similarity that exists in species due to common ancestry
are vestigial structures homologous?
yes
they must be homologous to some structure in a common ancestor
Genetic homology
occurs in DNA nucleotide sequences, RNA nucleotide sequences, or amino acid sequences
ex: the genetic code is very similar between organisms
Developmental homology
observed in embryos
ex: chick, human, and cat embryos all have similar tails and pouches
Structural homology
a similarity in adult morphology or form
Relationships between three levels of homology
genetic homologies cause development homologies in embryos which then cause the structural homologies in adults
Testing homologies experimentally
can insert homologous genes into different species and observe functioning development to showcase genetic homology
can test drugs on other organisms if they are homologous
current examples of descent from a common ancestor
speciation in fruit flies and sunflowers
internal consistency
most powerful support for a theory
the observation that data from independent sources agree in supporting predictions made by a theory
Steps of the scientific method
Question Hypothesis Collect evidence Make observations Analyze Draw conclusions
Defining alive
Grows and develops
Responds to stimuli from its environment
Reproduce
Must take in nutrients (energy) and release wastes
Maintain homeostasis
Adaption: populations of individuals evolve over time
Order and organization
Stores information
How does an organism maintain “alive”
all activities are mediated by biochemical activities within the cells
What did Darwin and Wallace question?
They questioned the diversity and variety of species