Natural Selection
(Environmental)
vs.
Selective Breeding
(Human Influences)
Environmental
And
Human Influences
Natural Selection
• Process by which
organisms that are
most suited to their
environment survive
and reproduce most
successfully.
Selective Breeding
• Method of breeding
that allows only
those organisms
with desired
characteristics to
produce the next
generation.
Charles Darwin
• Born 02/12/1809 – Shrewsbury, England
• Father was a medical doctor, and paternal grandfather (Erasmus
Darwin) was a famous botanist
• Attended medical school, but could not stand the sight of blood and
turned to natural history
• HMS Beagle Voyage from 12/27/1831 - 10/02/1836
• Influenced by the writings of Thomas Malthus – “An Essay on the
Principle of Population”
• Pushed by Alfred Wallace (1858) who independently hit upon the
idea of Natural Selection to complete and publish his great work “On
the Origin of Species – by Means of Natural Selection, or the
Preservation of Favoured Races in the Struggle for Life”
• Darwin’s Theory supplanted Lamarck’s (French, 1809) Theory that
simple creatures “strived” to become more complex
Darwin’s Voyage
• Charles Darwin
– Set sail on the HMS Beagle in 1831 as the ship’s
naturalist
– Arrived in the Galapagos Islands in 1835
– Observed that the animals on the islands were similar
to those on the mainland
Darwin’s Voyage
• Galapagos Animals
– The Galapagos animals,
while similar, were also
different from island to
island as well as to the
mainland
– Most obvious difference
were the sizes and shapes
of the finches’ (small
birds) beaks
– Sizes and shapes of the
beaks were adapted to
Natural Selection
Galapagos Islands
• Charles Darwin described
how organisms might
change over time based in
part to his observations of
the finches Galapagos
Islands.
• The Islands are
geographical different.
• The island’s geography
(environment) cause
different types of species
to be selected.
Darwin’s Voyage
• On the Origin of Species (Darwin’s book, 1859)
– For the 20 years that followed his return to England Darwin
studied plants, animals and adaptations
– Darwin wrote about how species can change gradually over
many, many generations and become better adapted to new
environmental conditions.
Galápagos Finches

Berry
eater
Insect
eaters
Seed Cactus
eaters eaters
Beak
shape
varies
depending
on diet
Evolution
• The gradual change in a
species over time.
Natural Selection
Organisms that are better adapted to an environment
are more likely to survive and reproduce than
organisms that are less well adapted.
Adaptations
Katydids have camouflage to look like leaves.
Non-poisonous king snakes mimic poisonous coral snakes.
Factors that affect Natural Selection:
Overproduction most species produce far more
offspring than will/can survive
Overproducers
Producers
mature rapidly
mature slowly
short-lived: most die before
they reproduce
live long lives: low juvenile
mortality rate
have many offspring - tend to
overproduce
have few offspring at a time
invest little in individual
youngsters
care for their young
population not regulated by
density: boom and bust
population figures
population stabilizes near
carrying capacity
Factors that affect Natural Selection:
Competition: since food and resources are
limited, the offspring have to compete to
survive
Darwin called it: “Struggle for existence”
Factors that affect Natural Selection:
Variation: Members within a species exhibit
individual differences – these differences must
be inheritable
Natural selection won’t work in a
population of clones! Remember that a key to
variation is sexual reproduction.
Factors that affect Natural Selection:
Survival to reproduce: Only those individuals
within a population that survive to
reproduce are considered successful
(“Survival of the fittest”).
Fit individuals pass on to a portion of their
offspring the advantageous characteristics.
Changes in the Environment
Example, the pepper moth.
Originally, the pepper moth was white, which
was good because it could blend in.
Then, trains were invented and the soot they
produced covered the trees. Making the trees
black. The moths that were black could now
survive better.
How many moths do you see in . . .
Picture #1
Picture #2


 Picture #3
The Peppered Moth
In Great Britain there
are two forms of
peppered moth--dark
and light forms.
Before the industrial
revolution, which of
the two moths in the
picture were the most
common and why?
(Look at the back
ground.)
After the Industrial Revolution, which of the
two moths were the most common and
why? (Look at the background.)
Since smoke pollution has decreased
in the UK, the light colored moths
have started to become more
common again. The process which
took place after the industrial
revolution is beginning to be
reversed. By 2019, the dark moths
are only expected to make up 1% of
the peppered moth population in
Britain.
Modified From:
Bibliography
Proffitt, F. 2004 In defense of Darwin and a Former Icon of Evolution. Science 304:1894-1895
Majerus, M. 2004 The Peppered Moth: decline of a Darwinian Disciple. Lecture to the British Humanist Association, 12 th February 2004
Updated 01/10/2006
Mutations
Some species are more susceptible to
mutations. Some mutations allow the
animal to survive; other mutations do not
allow the animal to survive. The mutations
that are not decrease the chance of survival
remain.
Natural Selection
Summary:
Environmental
Influence cause
organisms to be
selected that
adapt the best.
Man: Artificial Selection
• Selective breeding as practiced by humans on
domesticated plants and animals….
• For example: Dogs
Selective Breeding
Summary: Human Influence
on characteristics and
behavior.
• Domestic Animals
– Ex: Chickens, Dogs, Cows
• Plants:
– Ex: Corn, Brasilica, Fruit hybrids
HYBRIDIZATION
-Crossing dissimilar individuals to bring
together the best traits of both
organisms
-Produces hybrids:
* Hybrids can be different species
crossed together or different types within the
same species.
GOLDEN DOODLE
PUGGLE
Designer breeds or
mutts?
INBREEDING
Inbreeding = continued breeding of
similar individuals (ex. pure breed dogs)
-Has risks… increases breed’s susceptibility
to disease & deformities
EX: Golden retrievers - epilepsy
Dalmatians - hereditary deafness
Domestic Animals
• Various animals that have been tamed and
made fit for a human environment.
Selective Breeding
Look, there
they are again!
Selective Breeding In Animals
Animal
Characteristic
Improved
Cattle
Beef and Milk Production
Pig
Growth Rate and Litter Size
Sheep
Wool Quality and Quantity
Chicken
Growth Rate and Egg
Production
Behaviour, Appearance and
Abilities
Dog
Would this cow survive in nature?
• Did nature or man cause there to be Brussels
Sprouts?
Which ear of corn do you want?
Selective Breeding In Plants
Plant
Characteristic
Improved
Maize
Oil Content and Size of Cob
Tomato
Size, Colour and Flavour
Wheat
Apple
Height (being the same height
makes it easier to harvest )
Size, Colour and Flavour
Beans
Colour of Bean
Selective Breeding
(done by man)
Hybrid Fruits
How many types
of apples are
there?
MANIPULATING DNA
How are changes made to DNA?
Scientists use their knowledge of the
structure of DNA & its chemical
properties to study & change DNA
molecules
*This is GENETIC ENGINEERING
GENETIC ENGINEERING
= making changes in the DNA code of a
living organism
TRANSGENIC ORGANISMS
Contains genes from other species
1. Microorganisms (bacteria)
2. Animals (mouse; medical uses)
3. Plants (agricultural uses)
*Genetically Modified Crops
Gene causes these mice to glow in the dark. Normally,
the gene is found in jellyfish.
GROWING NERVE CELLS...GLOW IN THE DARK
MICE
http://www.youtube.com/watch?v=n0UzdYRnMtY
CLONING
•
member of a population of genetically
identical cells produced from a single cell
• easy to clone single cell organisms
• multicellular organisms more difficult to
clone
• a twin is a natural clone
• 1997 - Dolly the sheep cloned, 1st mammal
Which type of selection does man
control, Natural Selection or
Selective Breeding and why do you
think so ?