Download Evolution T/F

Evolution T/F …
_____ explains how organisms change over time
_____ is a theory that has been proven to be true
_____ assumes that all living organisms are somehow connected
to each other
_____ is no longer occurring in humans
_____ produces organisms that are bigger, stronger, faster, and/or
smarter
_____ could be occurring with people in this room right now
_____ happens when organisms want (or need) to change
… be prepared to justify your groups response
Evolution – The process by which modern
organisms have descended from ancient
organisms.
Evolution – The process by which modern
organisms have descended from ancient
organisms.
Adaptation – A trait that helps an organism
be better suited to its environment.
ex) a ducks webbed feet
Another Adaptation!!!
Fitness – The physical traits and behaviours
that better enable organisms to survive and
reproduce in their own environment.
Fitness … can take many forms. It’s not
always the biggest, strongest, & fastest.
EXPLANATIONS FOR EVOLUTION
Around 1800, scientists began to realize
that living things changed over time.
Charles Darwin
(1809-1882)
• English naturalist
• travelled around the world on
the H.M.S. Beagle observing
plant and animal life
• the trip took over 5 years
Darwin’s time on the Galapagos Islands
had a big impact on him developing his
theory of evolution.
marine iguana
flightless cormorant
Galapagos penguin
Sally Lightfoot crab
frigate bird
Galapagos Finches
The 13 species
of Galapagos
Finches were
also important
to Darwin
developing his
Theory of
Evolution.
Observation
Extraordinaire
Finches from
different
islands with
different
sources of
food (nuts,
berries, nectar,
insects, etc)
had different
beaks!
Adaptations develop
through natural selection.
How do adaptations evolve through
natural selection?
Within a species there is Speckled moths may be
variation for all traits.
more white or black in
Organisms that have
certain varieties of a
trait will have a slightly
better chance of
surviving and
reproducing.
color
Moths born with more
black pigment are better
likely to blend into the
dark background of tree
bark and therefore are
less likely to be eaten.
How do adaptations evolve through
natural selection?
Traits are inherited
from parents. Those
that will survive may
pass on their beneficial
traits to their offspring.
The cycle continues and
the population changes …
ADAPTIVE RADIATION
leads to EVOLUTION
through NATURAL
SELECTION.
Surviving moths will
reproduce and pass on
their traits to their
offspring.
Over many generations
the population of moths
evolves to become
darker. Making it better
adapted to its
environment.
• Darwin decided
that species
change over time
• in 1859, he
published his
famous book that
describes his
theory of evolution
• a key part of the
theory was the
idea of Common
Descent. It argued
all species have
evolved from one
common ancestor.
an evolutionary
tree, from one
of Darwin’s
notebooks
Further Influences on Darwin:
Charles Lyell (a rock star - geologist)
• he argued the Earth
was very old while
most believed earth
to be a few thousand
years old
• this meant common
descent could have
had enough time to
occur
Further Influences on Darwin:
Farmers
• Darwin knew farmers
altered their stocks with
breeding programs
(artificial selection)
• with a.s. humans ensure
only animals with desirable
traits are allowed to breed
• Darwin felt nature must
have a similar process only
allowing the best suited to
the environment to survive
Further Influences on Darwin:
Thomas Malthus
• he realized babies were being born
faster than people were dying
• he felt only famine, disease and
war would prevent endless human
population growth
• Darwin extended this to plants &
animals as he realized many
individuals of each species die and
few raise offspring. The question
was what determined who survived
and reproduced?
• In 1858 Alfred Wallace wrote
to Charles Darwin about his
ideas of evolution.
• His work also describes the
theory of natural selection.
• Wallace and Darwin copublished a paper on
evolutionary theory and are
considered the co-discoverers
of the Theory of Evolution.
• Each man gave the other as
much credit as possible.
Traits are
inherited
from
parents to
offspring
Spore
cloud
Reproduction
creates offspring
that have
variations from
their parents …
and each other!
Organisms vary within a species as no two
individuals are exactly alike!
This leads to a great
deal of diversity of
characteristics within
a population.
Members of a population often
vary greatly in their traits
Some traits make an organism more likely to
survive in their environment.
… others … not so much!.
Fig. 22-12
A flower
mantid
in Malaysia
A stick
mantid
in Africa
Offspring
with traits
that are
most “fit”
for their
environment
will
outcompete
others and
pass these
traits on.
Evolution by natural selection results in a
population that is better adapted (suited)
to its environment.
Evolution at its
best?
Divergent Evolution - an ancestral species
gives rise to a number of new species. This
is also known as adaptive radiation!
Darwin’s finches likely
developed different
beaks through
divergent evolution
due to natural
selection.
Diverge you finches!
Diverge you
bear (–like creatures)!
Divergent evolution may produce
homologous structures when
organisms from a common ancestor
adapt to a new environment.
Humerus
Radius
Ulna
Carpals
Metacarpals
Phalanges
Human
Cat
Whale
Bat
Convergent Evolution
- similar structures
develop from separate
ancestors because the
organisms occupy a
similar niche. These
are analogous
structures
Nature selects a
similar outcome!
Similar environment selects
for similar trait
Converge you web-footed
creatures!
Converge you swimmy marine
creatures!
Converge you … wacky looking insect eaters!
Animals in Australia
are weird because
they have been
separated from the
rest of the world for a
long time and evolved
separately.
They still developed
analogous structures
to animals elsewhere
due to having similar
niches.
Converge you crazy
aussies!
Fig. 22-20
Sugar
glider
NORTH
AMERICA
AUSTRALIA
Flying
squirrel
Vestigial organs
are structures that are no
longer used by the organism
in which they exist
They are believed to be
remnants of their
evolutionary past and
suggest adaptive radiation
from a common ancestor
Genetic Drift
• Occurs more frequently in smaller populations
• Genetic drift tends to reduce genetic variation
through losses of alleles
Animation: Causes of Evolutionary Change
The rest of the
population dies
randomly (is eaten)
Remaining
population is
different due to the
Bottleneck Effect
Some brave
Smarties relocate to
a new area
Population is
different due to the
FounderEffect
Fig. 24-6
A. harrisi
A. leucurus
If organisms are well suited to
their environment …
evolution can be very
minimal!
The tuatara is thought to have evolved little
in the last 200 to 250 million years.
The photo shows Henry. He is 111 and is the father
of babies that hatched in January, 2009.
Crocodiles are thought to have evolved little in
the last 200 million years.
Mountain Goats
near Mt. St. Helens
show little variation 
caused by a genetic drift
Horseshoe Crabs were present around 230
million years ago with very similar species
existing over 400 million years ago.
Darwin’s Theory of Natural Selection states:
• survival of the fittest
 organisms with favourable variations survive
and reproduce
 the individuals with characteristics not well
suited to their environment either die or leave
fewer offspring
 in this way, favourable variations are passed
from generation to generation
Evolution by Natural Selection – Key Points
• Note that individuals do not evolve;
populations evolve over time
• Natural selection can only increase or
decrease heritable traits in a population
• Adaptations vary with different
environments
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Natural Selection
Lamarck believed in the inheritance of
acquired characteristics.
Consider the
ears and tails
of Doberman
Pinschers.
Fig. 23-9
Original
population
Bottlenecking
event
Surviving
population