Transcript evolution - GordonOCDSB

EVOLUTION
Objectives:
1. Explain how natural selection works?
2. What observations did Darwin helped him
develop the theory of evolution?
3. What does adaptation mean? Give an
example of an organism adapting to its
environment.
Quiz
1.
2.
3.
4.
What don’t harmful mutations accumulate
over time?
Why can we use observations of bacteria as
evidence of evolution?
What is the difference between a hypothesis
and a theory?
What is selective breeding?
Early theories (pre-1700’s)
 Before Darwin, nature was seen as not
changing but as having originated through
spontaneous generation.
1700’s
 An understanding of the age of the Earth develops
through geology.
 The Earth has been and is still gradually changing.

Inheritance of acquired traits (use and disuse).
ex. Baby giraffes are born with long necks because
their parents stretched their necks to reach leaves
(Jean-Baptiste Lamarck, 1801)
Misconception
Genetics and the Passing on of
Traits
 Living
organisms pass on their traits to
their offspring.
 Today’s species came about through
gradual change.
 What drove that change?
SURVIVAL/SEX/!!!!
Darwin and the Voyage of the
Beagle
 December,
1831’s, Charles Darwin, a
naturalist in his 20’s began a 5-year
journey around the world on a ship called
HMS Beagle
 Darwin’s
role was to
observe, record, and
collect specimens of
rocks, minerals, plants, and animals

Darwin collected 1000’s of specimens and
shipped them to England, mainly from South
America and a chain of volcanic islands called
Galapagos

He did not realize what he was seeing until
years later (ex. didn’t catalogue the finches very
well, ate turtles that would later support his
theories, etc.)

Darwin spent the next 20 yrs analyzing his
findings in light of artificial selection (ex.
breeding of pigeons, breeding of dogs, etc.)
Darwin’s Finches
 Arrival
 Success
 Competition
 Diversity
&
Opportunity
 Radiation
 Perhaps
a single ancestral species
transported from nearby land might give
rise to a number of similar but distinct new
species.
 Hawaiian
honeycreeper
What Darwin Observed

1) Homologous Features

Homologous
features: different
functions, but
similar structure
(flippers, hands,  All forelimbs of
wings)
vertebrates have the
same pattern of bones
ex. The
flippers of
whales, and
the wings of
birds
 2)
Analogous features: similar functions,
but different structure (wings of birds and
bees)
 Darwin’s
conclusion: organisms with
homologous features likely shared a more
recent ancestor, while those with
analogous features do not!

3) Vestigial Features:
non-functional
structures that are
homologous to fully
functioning structures
in closely related
species.

Example: whales have
pelvic bones that do
not attach to legs

4) Similarities in Early
Development
(tailbones)
 Goosebumps
 Darwin’s conclusion:
these ‘leftover’
features must have
once had a use!
Other Evidence for Evolution…
 Stuff
that we have seen in our time…
When comparing
the DNA of one
species to
another, more
similarities are
found in
species that
are more
closely related.
Evidence for Evolution


The Fossil Record-Layer
show change
Shows numbers extinct animals
 Shows similarities between extinct
animals and animals that are alive
today
 The earth’s layers show a time
scale of species and when they
appeared on earth (and when they
died out)
Transitional fossils
are fossils that
show intermediary
links between
groups of
organisms
 They can provide a
link between the
past and present

Direct observation of species
change

Bacteria become
resistant to
antibiotics

Wolves were bred over
many generations to
become dogs (artificial
selection) • and then bred
further to create a variety
of breeds
But how does evolution really
work???
 How
does evolution really work?
http://www.pbs.org/wgbh/evolution/educat
ors/teachstuds/svideos.html
What did Darwin think drove
Evolution???
 1)



Artificial Selection
Selecting offspring with desirable traits as
breeding stock for succeeding generations
Example: corn with higher oil content
Darwin’s conclusion: if people could alter the
appearance and behaviour of species through
artificial selection, then the environment could
have a similar selective effect on wild species!
Natural Selection & Artificial
Selection

Natural variation--differences among
individuals of a species

Artificial selection- nature provides the
variation among different organisms, and
humans select those variations they find
useful.
Evolution by Natural Selection

The Struggle for Existencemembers of each species have to
compete for food, shelter, other life
necessities

Survival of the Fittest-Some
individuals better suited for the
environment

The Struggle for Survival


Plants and animals produce more offspring
than are able to survive
Favourable variations would tend to be
preserved, unfavourable ones would be
destroyed.
INTENSE COMPETITION!!!!!
Natural Selection as the Cause of Evolution
- called “natural selection” because it happens on
its own
1. Genetic Variation
- there are many varieties of alleles
- caused by random mutations
- can be passed onto offsprings (inherited variation)
2. Overproduction of Offsprings
- organisms make too many offsprings
3. Struggle for existence
- competition for limited resources
4. Differential survival and reproduction
- only organisms that have certain
characteristics will survive to reproduce
- non-random, caused by the environment:
amount of food, competition (ex. Darwin’s
finches)
 PBS
Evolution: The Evolutionary Arms
Race (12 min)
 Answer questions on video.
All of this takes a LOOOOOOONG
time
 Your
1.
2.
task… (Due for tomorrow!!!)
Read through the handout on Adaptation
and Variation
Answer questions 1-5