Darwin & Natural Selection
Adapted from Mr. Gray & Bristol University
Hypothesis: is an educated guess, based on observations . It's a prediction of cause and effect.
Theory:
Summarizes a hypothesis/hypotheses
Supported with repeated testing
Valid as long as there is no evidence to dispute it
Explains how and why something happens
Example: Theory of Plate Tectonics
Law:
Generalizes a LOT of observations
Tells you what IS going to happen
Example: Law of Gravitation
Basic Scientific Terms Review
Directions Manager: read ?’s
1. Can a theory become a law?
Explain.
2. What’s wrong with this statement
– I have a theory that students
get more write ups after the
holidays.
Evolution
Evolution: The process of change over
time; one species gives rise to another &
“tree” grows!
All living things share a common ancestor.
We can draw a “family” tree of life to show
how every species is related.
Learning Manager – read ?
Besides cell phones, what other
non-biological items have
evolved?
Charles Darwin
Father of Evolution
Proposed the theory of evolution, change over time
Made observations on a 5-year trip around the world on the ship the HMS Beagle
Wrote a book “Origin of the Species” that documented his observations
Survival of the Fittest idea came from this book
Darwin’s Finches
Check out their feet!!!
On Task Manager – read ?
Charles Darwin noticed all the
different looks of the same species.
How might different looks affect
whether a species goes extinct?
Natural Selection
Natural Selection: Organisms that are best
adapted to an environment survive and
reproduce more than others
How Natural Selection Occurs – 4 Ways
Overproduction
Variation
Competition
Selection
Overproduction
Each species produces more offspring that can
survive
Each individual has a unique combination of inherited traits (DNA)
Adaptation: an inherited trait that increases an organism’s chances of survival
Environments can changewhich can change the success of an adaptation Same Parents
Variation
Adaptation Categories
Camouflage (Blend in and hide)
Mimicry (Act and look like)
Physiological (Poison)
Behavioral (Group behavior)
Remember the organism doesn’t CHOOSE the
adaptation! They are born with it or the
environment is more supporting of it!
Coral Snake
(Poisonous)Milk Snake
(Not
poisonous)
Stick Mantid
Flower Mantid
What adaptations do
you see?
What adaptations do
you see?
Variation
The more variation within a species, the more likely they are to survive
The more variation of types of species in a habitat, the more likely at least some will survive
Which community has a better chance of
surviving a natural disaster?
Community A Community B
Competition
Individuals COMPETE for food, water, space, etc.
Survival of the Fittest – the fittest is most able to
survive and reproduce
Not all individuals survive to adulthood
Best adaptations will survive and be able to pass on
their traits to their kids
Genotype: your genes/DNA
Ex: Cat’s ear shape
Phenotype: your physical appearance that is
influenced by your genes and the environment
The color of the flamingo is based on what they eat
(environment)
Selection
Materials Manager – read ? ‘s
What are the 4 “methods” of natural
selection?
Which “method” in your opinion
affects humans most?
How It Works
Individuals with traits that are not well suited to their environment either die or leave few offspring.
Evolution occurs when good traits build up in a population over many generations and bad traits are eliminated by the death of the individuals.
50 Million Years Ago
Today
Directions Manager – read ?
Summarize how giraffes evolved.
Peppered Moth
Which moth will the bird catch?
A
B
Evidence for Evolution:
Fossil Record
Homologous Body Structures
Vestigial Organs
Embryology
Biochemical Evidence
Fossils provide a record of the history of life on
Earth
Fossil Record
Progression of Organisms
dinosaurs humansbacteriaorigins
http://en.wikipedia.org/wiki/Geologic_time_scale
en.wikipedia.org/wiki/Image:Eopraptor_sketch5.png© World Health Org.
© NASA
complex cells
The fossil record shows a sequence from simple bacteria to
more complex organisms through time and provides the most
compelling evidence for evolution.
Transitional Fossils – Ex.
Archaeopteryx
Missing link between
reptiles and birds
Geologic Separation
Homologous Body Structures
Body parts that are
similar in different
species
Related organisms have
similar body structures
Humans and Gorillas Bone Structure
“Leftover” organs (traces of
evolution) that serve no
purpose currently (did in the
past)
Examples appendix,
tonsils, tailbone, wisdom
teeth
Vestigial Organs
Embryos of all vertebrates are very similar early
on – yes you had gills!
Embryology
The Pharyngeal Pouches will shape parts of the
pharynx and upper bronchial segments
DNA with more similar
sequences suggest species
are more closely related
Humans and chimpanzees
share > 98% of identical
DNA sequences
Biochemistry
HUMAN CCAAGGTCACGACTACTCCAATTGTCACAACTGTTCCAACCGTCACGACTGTTGAACGA
CHIMPANZEE CCAAGGTCACGACTACTCCAATTGTCACAACTGTTCCAACCGTCATGACTGTTGAACGA
GORILLA CCAAGGTCACAACTACTCCAATTGTCACAACTGTTCCAACCGTCACGACTGTTGAACGA
Genetic code of chimps and gorillas is almost identical to humans
Directions Manager – read ?
What are the 5 types of evidence
used for evolution?
What is your opinion about evolution?
Thinking outside
biology/species – how might
the quote above affect you in
everyday/real life?
Supporting Resources
https://www.youtube.com/watch?v=0SCjhI86grU
Must Watch—Fantastic Review
https://www.youtube.com/watch?v=FW-uW71-DHU
Simpson Evolution