Transcript Evolution Power point

Observation & Inference
Observation
• An observation is gathering information
about events or processes.
• They can be quantative which are
measurable or countable or they can be
qualitative which are describable and
not numerical.
• Observation is the skill of describing
events.
Inference
• An inference is a conclusion or deduction based on
observations.
• Making an inference is the process of drawing a
conclusion from given evidence.
Practice:
• Observations:
• A student is in a wheelchair
• The student has a cast on their leg
• The student is wearing a football shirt
• Inference = ?
– The student broke his leg while playing
football.
FRAME 1
Look at these two sets
of animal tracks.
What are 3
OBSERVATIONS
Make an INFERENCE
Now what do you think?
FRAME 2
Make 3 OBSERVATIONS
Make an INFERENCE
Now what do you think?
FRAME 3
Make 3 OBSERVATIONS
Make an INFERENCE
Truth: Evolution is just a theory.
• In everyday language, theory is often used to
mean a hunch with little evidential support.
Scientific theories, on the other hand, are
broad explanations for a wide range of
phenomena.
• In order to be accepted by the scientific
community, a theory must be strongly
supported by many different lines of evidence.
• Evolution is a well-supported and broadly
accepted scientific theory; it is not ‘just' a
hunch.
Misconception:
Evolution is not science
because it is not testable.
Truth: Science is not always testable.
• Many scientific investigations do not involve experiments
or direct observation.
– Astronomers cannot hold stars in their hands and geologists cannot go
back in time, but both scientists can learn a great deal about the
universe through observation and comparison.
– In the same way, evolutionary biologists can test their ideas about the
history of life on Earth by making observations in the real world.
• In organisms with short generation
times like bacteria or fruit flies,
scientists can actually observe
evolution in action over the course
of an experiment.
Remember: Hypothesis vs. Theory
• Hypothesis: Possible explanation for a
set of observations or possible answer to a
scientific question.
• Theory: well tested explanation that
unifies a broad range of observations
How is Evolution Supported?
1. The Fossil Record
2. Geographic
Distribution of Living
Things (Biogeography)
3. Anatomical Evidence
a) Homologous Body
Structures
b) Vestigial Limbs
c) Similarities in Early
Development
4. Molecular DNA
FOSSILS
Evidence for Evolution through
studying fossils
BRAINPOP on Fossils:
http://www.brainpop.com/science/diversityoflife/fossils/preview.weml
The Fossil Record is Incomplete
Fossils = Traces of dead organisms such as footprints, insects,
bones, leaf impressions, etc.
• The fossil record shows a sequential appearance and disappearance
of species
• New species have generally appeared gradually, with species
becoming more complex over time
• Fossils found in rock layers tells us two things:
• What the creatures and plants looked like.
• How long ago they existed. (Generally the deeper, the older.)
• The fossil record is incomplete. This is because
very few species turn into fossils. Most decay away.
Forming Fossils
• Not all parts of an animal become
fossilized.
– It may not be possible to know some
details of what an ancient animal or plant
was like because many parts of the
anatomy may not fossilize.
• What color were the scales on this Allosaurus?
• Why do scientists not know the answer to this
question?
Dating Fossils
•
•
•
•
•
Radioactive decay
determines age.
Half-life = how long it
takes for half of the
radioactive atoms in a
sample to decay.
Carbon 14 has a half life
of 5730 years
It would take 5730 years
for 12 grams of Carbon 14
to breakdown into 6 grams
of Carbon 14.
The process of evolution is
very slow, and takes
thousands of years.
Relative vs. Absolute Dating
• The absolute age of a fossil
can be determined though
radiometric dating and
determining the age of the
layer of rock in which the
fossil was found.
• The relative age of a fossil is
determined by comparing it
to other fossils.
• Older layers are found
deeper within the earth
than newer layers.
Fossil Transitional forms – More evidence
• Transitional fossils are bones that contain traits
ancestral groups and descendent groups. These link new
species to old species
• These intermediate fossils give the history of a slow
transformation
• Example: Whales came from 4 legged animals
• It took them 60 million years to evolve into
what they are today. There are a series of fossils
found that show the tail and fins developing slowly and
the legs disappearing.
Whale Video
Evolution of birds
Today’s organisms
descended from
ancestral species
Fossil of Archaeopteryx
• lived about 150 mya
• links reptiles & birds
Fossil Evidence of Evolution
Evolutionary change in body size and toe
reduction of horses
19
Evidence that Supports Evolution:
Biogeography
• Biogeography: the study of
the geographic distribution of
species over time
– Some plants and animals
have similar appearance
but are only distantly
related
• Convergent evolution: the
independent development of
similar structures in organisms
that are not directly related
• Convergent evolution is
usually seen in animals and
plants that live in similar
environments but in different
locations.
Green Tree
Python from
Australia
Emerald Tree
Boa from
South America
20
Evidence that Supports Evolution:
Biogeography
1. Similar animals on each
continent live in similar
ecological conditions
a. They were exposed to
similar pressures of
natural selection.
b. Because of similar
selection pressures,
different animals ended
up evolving similar
characteristics
Beaver
Beaver
NORTH
AMERICA
Muskrat
Muskrat
Beaver and
Muskrat
Coypu
Capybara
SOUTH
AMERICA
Coypu and
Capybara
Capybara
Coypu
Evidence that Supports Evolution:
Biogeography
• Divergent Evolution: The
process by which an
ancestral species gives rise
to a number of new species
that are adapted to
different environmental
conditions and are less alike.
• Often occurs when a species
colonizes a new environment.
• Also known as adaptive
radiation.
• Examples:
– Darwin’s Finches.
– Brown bears and polar bears
Evidence that Supports Evolution:
Anatomical
• Descent with Modification- Each living organism
has descended, with changes from other species
over time
• Common Descent- all living things were derived
(originated) from a common ancestor.
Evidence that Supports Evolution:
Anatomical
• Homologous Structures =
Structures from different
organisms that have
different mature forms, but
come from the same
embryonic origin
• homo- = same
• -logous = information
– same structure on the inside
– same development in embryo
– different functions on the
outside
– evidence of common
ancestor
Ex) Forelimbs of human, cats, whales, & bats
Evidence that Supports Evolution:
Anatomical
• Analogous
Structures
– Structures that look
similar on the outside
and have the same
function but have
different structure &
development on the
inside
– different origin
– no evolutionary
relationship
Ex) Wing of a bat and wing of a butterfly
Evidence that Supports Evolution:
Anatomical
Vestigial Structures = structures that are present
in an organism but do not serve any function
They are remnants of evolutionary past
Example:
Whales have a
pelvis and femur,
but they
no longer walk
on land.
Evidence that Supports Evolution:
Anatomical
• Pythons have tiny femurs (leg bone)
that are vestigial organs
Evidence that Supports Evolution:
Embryology
1.Embryology – the study of developing
embryos
1. The embryos of vertebrates are
very similar during early
development.
2. The same groups of embryonic
cells develop in the same order and
in similar patterns to produce
tissues & organs.
3. Common cells & tissues growing
in similar ways produce homologous
structures.
4. Implies that common genes are
involved.
Embryos of vertebrates
develop gill slits and tails.
Chicken – 2 ½ days
Human – 31 days
We grow into our “spine”.
At first it appears to be
tail-like.
Pig – 21 days
Human – 9 weeks
Pig – 30 days
Lemur – 3 ½ weeks
The heart
dominates
the body
cavity.
Limb Buds
Pig foot –
30 days
Human hand –
6 weeks
Chicken foot –
5 days
Human – 6 weeks
Pig – 30 days
Macaque – 4 weeks
Evidence that Supports Evolution:
Molecular DNA
• AKA Biochemical
Evidence
• Two closely-related
organisms will have
similar DNA, RNA, and
protein (amino acid)
sequences.
• This also gives evidence
of a common ancestor.
Evidence that Supports Evolution:
Molecular DNA
• Which primate is most related to Humans?