Transcript Natural Selection - The Science Queen

Adaptation, Mutation, and
Finches?
Natural selection means that traits that
offer an advantage will most likely be
passed on to offspring; individuals with
those traits have a better chance of
surviving.
Lemurs of Madagascar
Amazonian Frogs
Humans select traits for dogs, pigeons and other animals when they breed
them.
Bred Pigeons came from a single original species
Who selects the traits for wild plans & animals?
NOBODY!!
There is no agent involved in natural selection.
Natural selection is a process of elimination
INDIVIDUALS THAT HAVE TRAITS THAT ARE BEST ADAPTED FOR THE
CURRENT ENVIRONMENT ARE THE ONES THAT SURVIVE TO BREED
AND PASS ON THEIR GENES TO THE NEXT GENERATION.
Organisms not possessing the beneficial traits
either die or don’t have as many offspring.
Natural Selection is
Survival of the Fittest

The individuals that survive are not always the strongest, fastest, or smartest. Therefore, "survival of the fittest"
may not be the best way to describe what natural selection really is as it applies to evolution.

Darwin meant "fittest" to mean the one best suited for the immediate environment. This is the basis of the idea of
natural selection.

The individual of the population only needs to have the most favorable traits to survive in the environment. It
should follow that individuals who have the favorable adaptations will live long enough to pass down those
genes to their offspring.

Individuals lacking the favorable traits, in other words the "unfit", will most likely not live long enough to pass
down the unfavorable traits and eventually those traits will be bred out of the population.

The unfavorable traits may take many generations to decline in numbers and even longer to disappear
completely from the gene pool.

This is evident in humans with the genes of fatal diseases are still in the gene pool even though they are
unfavorable for the survival of the species.
Natural Selection is a mixture of both Chance and necessity
Natural Selection is not goal directed. It does not have a long term goal.
What are pressures that act on a
population?
• Competition for food
• Competition for a mate
• Changes in the environment
• Predators
• Parasites
 Predators - variants with adaptations allowing them to
escape predators have more offspring
- e.g. speed, defensive weapons, camouflage, mimicry
 Prey/Food - variants with adaptations allowing them to
obtain food have more offspring
- e.g. Speed, senses for finding prey/food, weapons for killing prey or
obtaining food, camouflage for stealth
 Climate - those who can survive new climate best have
more kids
- e.g. ice age, change in climate due to migration.
 Mates - variants with adaptations allowing them to attract
a mate to have offspring
- e.g. strong, attractive, good provider
 Animals
who have greater fitness survive
in environment and live to reproduce
 Random changes (mutations) can lead
to greater or less fitness
 Adaptations allow an organism to
survive better in their environment
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.
*Follow along with your video note sheet!
 Do
you remember these guys?
 “Industrial
Melanism”- darkness- of the skin,
feathers, or fur. Acquired by a population of
animals living in an industrial region where
the environment is soot-darkened.


Manchester, England
from 1845 to 1890.
Before the industrial
revolution, the trunks of
the trees in the forest
around Manchester were
light grayish-green due
to the presence of
lichens.



Most of the peppered
moths in the area were
light colored with dark
spots.
As the industrial
revolution progressed,
the tree trunks became
covered with soot and
turned dark.
Over a period of 45
years, the dark variety of
the peppered moth
became more common.
Summary: Environmental Influence
due to organism adaptation.
 Mouth
parts
ex: beaks, teeth
 External
color
ex: fur, scales, feathers
 Behavior

1850’s: Charles Darwin
described how
organisms might change
over time.

Theory of Evolution

5 years of observations
on the islands.
 The
smallest, lowest islands were hot, dry,
and nearly barren-Hood Island-sparse
vegetation
 The
higher islands had greater rainfall and
a different assortment of plants and
animals-Isabela- Island had rich
vegetation.
 Darwin
was fascinated in particular by the
land tortoises and marine iguanas in the
Galápagos.
 Giant
tortoises varied in predictable ways
from one island to another.
 The
shape of a tortoise's shell could be
used to identify which island a particular
tortoise inhabited.
 Land
Tortoises
 Darwin
Finches
 Blue-Footed
 Marine
Booby
Iguanas
Darwin
Observed that characteristics
of many plants and animals vary
greatly among the islands
Hypothesis:
Separate species may
have arose from an original ancestor
Summary: Human Influence on
characteristics and behavior.
 Domestic
Animals
 Ex: Chickens, Dogs, Cows
 Plants:
 Ex: Corn, Brasilica, Fruit
hybrids
 Various
animals that have been tamed
and made fit for a human environment.
Bull Terrier
Basset Hound
Pug Boxer
A
shorter
means
a host
of problems.breed
The modern
Boxer
only has
a shorterwith
face
but
the– muzzle
is slightly
The
Pug is face
another
extreme
brachycephalic
and it has
all thenot
problems
associated
that
trait
high blood
pressure, heart
upturned.
The
boxer
–
like
all
bracecyphalic
dogs
–
has
difficulty
controlling
its
temperature
in
hot
weather,
problems, low oxygenation, difficulty breathing, tendency to overheat, dentition problems, and skin fold dermatitis. Thethe
highly
inability
shed heattail
places
limitsa on
physical
performance.
It also
has
one oftothe
highest cancer rates.
desirableto
double-curl
is actually
genetic
defect,
in more serious
forms
it leads
paralysis.
 Nectarcots
 Pluots
 How
many
types of apples
are there?