Download Natural Selection

Bellwork: Mon. Feb. 13, 2017
From – Video “Extinction”
1. What is a mass extinction?
2. There have been ____ mass extinctions on Earth?
3. Scientists think we are in the ____ mass
extinction because__________________________
__________________________________________
occurs when more individuals are born than can survive.
Those with the best
traits pass them on.
There is a struggle for existence – competition for
resources
http://www.youtube.com/watch?v=mPTf3DHmHe4
Darwin knew that individuals have natural
Variations: differences among their heritable
traits, and he hypothesized that some of those
variants are better suited to life in their
environment than others.
Adaptation: Any heritable characteristic that
increases an organism’s ability to survive
and reproduce in its environment
Pinta
Pinta Island
Tower
Marchena
Giant Tortoises of
the Galápagos
Islands
Intermediate shell
James
Fernandina
Santa Cruz
Isabela
Santa Fe
Hood Island
Floreana
Isabela Island
Hood
Saddle-backed shell
http://www.youtube.com/watch?v=uakRR7a2f3w
Dome-shaped shell
“The inhabitants...state that they can distinguish the tortoise from different islands;
and that they differ not only in size, but in other characters. Captain Porter has
described those from Charles and from the nearest island to it, namely Hood
Island, as having their shells in front thick and turned up like a Spanish saddle,
whilst the tortoises from James Island are rounder, blacker, and have a better
taste when cooked.” Charles Darwin 1845
Adaptations can involve:
1. Body parts or structures: like a tiger’s claws;
length of body…
2. Colors: Those that make camouflage or
mimicry possible
3. Physiological functions, like the way a plant
carries out photosynthesis.
Fitness describes how well an organism can survive and
reproduce in its environment.
Individuals with adaptations well-suited to their environment
can survive and reproduce = high fitness.
Individuals with characteristics not well-suited to their
environment either die without reproducing or leave few
offspring = low fitness.
This difference in rates of survival and reproduction is
called survival of the fittest.
Darwin named his mechanism for evolution natural
selection because of its similarities to artificial selection.
Natural selection is the process by which organisms with
variations most suited to their local environment survive and
leave more offspring.
In natural selection, the environment—not a farmer or
animal breeder—influences fitness –
if that happens it is called
artificial selection
From generation to generation, populations change - they
become better adapted as their environment changes.
Natural selection acts on inherited traits - those are the
only characteristics that parents can pass on to their
offspring.
This hypothetical
population of
grasshoppers changes
over time as a result of
natural selection.
Grasshoppers can lay
more than 200 eggs at
a time, but only a small
fraction of these
offspring survive to
reproduce.
variations, called
adaptations, increase an
individual’s chances of
surviving and
reproducing.
variation = yellow and
green body color.
Green color is an
adaptation: The green
grasshoppers blend into
their environment and so
are less visible to
predators.
Because their color
serves as a
camouflage
adaptation, green
grasshoppers have
higher fitness and so
survive and
reproduce more
often than yellow
grasshoppers do.
Green grasshoppers
become more common
than yellow
grasshoppers in this
population over time
because more
grasshoppers are born
than can survive,
individuals vary in color
and color is a heritable
trait, and green
grasshoppers have
higher fitness in this
particular environment
 does not make organisms “better.”
 Adaptations don’t have to be perfect—just good enough to
enable an organism to pass its genes to the next generation.
 doesn’t move in a fixed direction. There is no perfect way of
doing something. Natural selection is just a process that
enables organisms to survive and reproduce in a local
environment.

If local environmental conditions change, some traits
that were once adaptive may no longer be useful, and
different traits may become adaptive.

If environmental conditions change faster than a
species can adapt to those changes, the species may
become extinct.

http://www.youtube.com/watch?v=WbW8GgAWKi8&feature=fvst
Darwin based his explanation for
the diversity of life on the idea
that species change over time.
“A single ‘tree of life’ links all
living things…”
1 on the chart represents
a “Common Ancestor” an
ancestor from which all the
others descended
Natural selection produces organisms that have different
structures, establish different niches, or occupy different
habitats.
descent with modification: Darwin theorized that
each living species has descended, with changes,
from other species over time.
http://www.youtube.com/watch?v=_ksdV9HPwBY
Bellwork: Tues. Feb. 14, 2017
Name as many Evidences of Evolution you can
think of (look in your notes):
1
2
3
4
5
6
Evidences of Evolution
1. Fossil Record
2. Geographical Distribution: Plate Tectonics
(Biogeography)
3. Transitional Forms: Homologous Structures/
Analogous /Structures/Vestigial Structures
4. Embryology
5. Genetics and Molecular Biology – DNA: hox Genes
- major control genes every organism has
6. Molecular Clock: constant mutation rates
Pre-Registration info.:
Freshmen
< D in Algebra = Environmental Science
> C in Algebra = Physics
> C in Geometry = pre-AP Physics
Sophomores
< D in Algebra = Chemistry Essentials
> C in Algebra (with intent to register in Algebra II) = Chemistry
> C in Algebra (with intent to register in Intermediate Algebra) = Chemistry Essentials
> C in Algebra II = pre-AP Chemistry
Relative age: Law of Superposition in a
sequence of undeformed sedimentary rocks
the oldest beds are at the bottom and the
youngest ones are at the top
1. layers were originally deposited horizontally
2. the beds are not overturned (sedimentary
structures can be used to determine whether a
sedimentary succession is overturned or not).
Which
layer is
the oldest
here?
Other Scientists
Many scientists recognize that Earth is millions
of years old and things (like earthquakes and
erosion) that changed Earth in the past are still
doing so today.
Like Hutton and Lyell
Charles Lyell in “Principles of Geology”
stressed that scientists explain past events in terms
they can actually observe.
James Hutton’s the idea of: uniformitarianism:
that the earth was shaped by slow-moving forces
still in operation today.
think of Haiti
living things have changed over time.
all species were descended from other
species.
organisms were adapted to their
environments.
Lamark: (Giraffe Neck Theory)
selective use or disuse of
organs - organisms acquired or
lost certain traits during their
lifetime – which could then be
passed on to their offspring.
Lamarck’s hypotheses of evolution are incorrect in
several ways:
Lamarck did not know:
 how traits are inherited (DNA)
 that an organism’s behavior has no effect on its
heritable characteristics.
But he paved the way for discoveries of
later biologists.
As in the study of epigenetics today
The idea that phenotype (or gene expression –
remember protein synthesis?) can be caused by
mechanisms other than changes in DNA sequence
Copyright Pearson Prentice Hall
http://news.nationalgeog
raphic.com/news/2011/0
1/110118-oldestdomestic-dogs-northamerica-eaten-texascave-science-animals/
Darwin noted that plant and animal breeders would breed only
the largest hogs, the fastest horses, or the cows that produced
the most milk.
He called this process:
Artificial selection: selection by humans for breeding of useful traits
from the natural variation among different organisms.
Compare it to: Natural Selection: Process where
individuals better suited to their environment survive
and reproduce most successfully
Copyright Pearson Prentice Hall
Copyright Pearson Prentice Hall
 Cocoa Bean and Clyde
Animal mutations and structural variations –
one of the first to come up with the idea of
Master (or hox) Genes
Hint words: partial word
bank (look for the rest of
the terms in your notes)
Relative dating
Radiometric dating
Half-Life
Geologic Time Scale
Cenozoic erz
Precambriam Era
Mesozoic Era
Transitional forms: Fossils or organisms that
show the intermediate states between an
ancestral form and that of its descendants.
 Common Ancestor:
Proposed ancestor from
which other organisms evolved
 http://evolution.berkeley.edu/evolibrary/news/060501_tikt
aalik
Transitional forms: Fossils or organisms that
show the intermediate states between an
ancestral form and that of its descendants are
referred to as transitional forms.
Bellwork: Thurs. Feb. 14, 2013
1. A tetrapod is any
2. The “Cambrian Explosion” is
when