Transcript Patterns in Natural Selection

Evolution and
Adaptations
Evolution
Simple Definition – change over time
Complicated Definition – process by which
modern organisms have descended from
ancient organisms
History of Evolution
• Charles Darwin
– Flunked out of medical school
– Sailed around the world on a boat called the
HMS Beagle
– Made many observations about animals
around the world and collected evidence that
led him to propose his hypothesis.
• Birds, Tortoises
– Concluded that Evolution happened because
of Natural Selection
Darwin’s Observations
• Living Organisms and Fossils
– Collected and preserved fossils
– Noticed that some fossils resembled
organisms that were in existence and some
were not like any other animal he had ever
seen
Darwin’s Observations
• Darwin observed 3 different types of tortoises
on the Galapogas.
• What kinds of plants do you think the saddle
tortoise might eat vs. the domed tortoise?
Scientists who influenced Darwin
James Hutton and Charles Lyell
• Their research showing that earth was millions
of years old and that the surface/ features of
earth had been changing for millions of years
helped support/ develop Darwin’s crazy new
idea that the appearances of animals had been
changing throughout time as well.
Who else was thinking about
evolution?
Jean Baptiste Lamarck
Jean Baptiste Lamarck
• Disagreed with Darwin
• Said that Evolution happened because of
TRAITS that organisms ACQUIRED
during their lifetime
• Theory of Use/ Disuse – proposed that
by selective USE or DISUSE of structures/
organs, organisms acquired or lost traits
during their lifetime
– These Acquired or Lost traits could then be
passed on to the offspring
Why Lamarck was wrong
p.425
• Vestigial Structures
– Humans have an appendix – used to be used
for digestion, but now it has no real purpose in
the body, but we are still born with an
appendix
– Snakes have a pelvic bone and leg
attachments in their skeletons, but they do
not walk and they do not have legs – it is
believed that snakes developed from crawling
reptiles
Acquired Traits
Artificial Selection vs. Natural Selection
• Artificial Selection – purposefully
breeding organisms that have the best
traits
– Farmers will breed the best cows in order to
get the best meat or milk
• Natural Selection – organisms that are
most adapted to their environment will
mate with each other to pass on their
genes to the next generation
– Have the greatest fitness
Natural Selection
• Definition – process by which traits become
MORE or LESS common in a population
– 4 principles of Natural Selection
• Variation – individuals in a population are different
from one another
• Heritability – variations are inherited from parents
• Overproduction – populations produce more offspring
than can survive
• Reproductive Advantage – some variations allow
organisms to have more babies than others
Survival of the Fittest
• Fitness – an organisms ability to survive
on its own and to produce viable offspring
• More fitness an organism has, the better
chances it has to pass on its genes to the
next generation
• Adaptation – any inherited characteristic
that increases an organism’s chance of
survival – increases its fitness
Patterns of Natural Selection
• When populations change in physical characteristics
due to Natural Selection, they exhibit 1 of 3 different
graph distributions
– Directional Selection – 1 of the extreme traits is selected
for – ex really tall people become more numerous than
short people
– Disruptional Selection – Both extremes are selected
FOR and the average of the 2 traits is selected AGAINST
– ex really tall people and really short people become
more numerous than average-height people
– Stabilizing Selection – The average trait is more
favorable and the extreme traits are selected against – ex
in a population of short, medium and tall people, you
would expect to see more medium-sized people over time
Evidences of Evolution
Can you pick out the misconceptions
regarding evolution?
• Charles Darwin developed the theory of
evolution.
• Scientists believe in evolution.
• Humans evolved from monkeys.
• Scientists regularly debate whether
evolution happens.
• Evolution as a science deals with the
origins of life on Earth.
5 pieces of Evidence to
support Evolution
Evidence 1: Homology
Homology
• Structures in different species that have a
common evolutionary ancestry or a
common developmental ancestry.
– They may or may not have the same function
in both species.
• Can you think of some homologous
structures? Remember the animals must
be related.
What in this picture shows
evidence of homology?
How are these animals related?
Analogous Structures
• Structures that have the same function
and might look the same, but are NOT
inherited from a common ancestor
• Ex Wings – insects and birds
Homology or Analogy
• Whales are mammals and sharks are not,
yet they both have fins for swimming – are
these structures Analogous or
Homologous?
• A duckbill platypus has fur, so does a
polar bear – are these structures
analogous or homologous?
Evidence 2: Comparative Embryology
What relationship exists?
• If a structure existed before another structure in
evolutionary terms, it will also appear earlier in the
embryo’s development.
• Species which have an evolutionary relationship
typically share the early stages of embryonal
development and differ in later stages.
Evidence 3: Genetics and DNA
Similarities (Molecular Evidence)
What we know…
• All cells rely on DNA to make proteins.
• Using new technologies, biologists are able to
determine the amino acid sequences in proteins to
determine evolutionary relationships among various
species of organisms.
• The more closely related two species are, the
greater the similarity in amino acid sequences of
their proteins.
• Molecular Genetics provides direct evidence to
evolution.
For example:
Evidence 4: Fossil Record
Paleontology is the Key
• The discovery of fossils showing
forms of animals never previously
seen.
• Fossils provide direct evidence
of the history of evolution.
• Darwin saw fossils of animals that
were similar to one’s that he had
seen before, but weren’t exactly
the same
Evolution of Horses
• Horses do not look
the same as they did
many years ago
• Fossil Record shows
evidence that
animals have
changed over time
and that they share a
common ancestor
based on similarities
in their skeletons.
Evidence 5: Biogeography
Historical Biogeography
Concerned with the origins and
histories of species
• Fossil records
• Cladograms
http://www.cartage.org.lb/en/themes/Sciences/Zoology/Biologicaldiverstity/Classification/cladogram_1.gif
Continental Drift
• Alfred Wegener
• Plate Tectonics
• The case of the mesosaurus
Mesosaurus
How fast can evolution happen?
• Gradualism - very small changes over
long periods of time
• Punctuated Equilibrium - catastrophic
events cause rapid evolution in very short
amounts of time
Gradualism and Punctuated Equilibrium
Adaptations
• Definition – trait shaped by natural selection
that increases and organism’s reproductive
success
– More simply – a body part, body covering, or
behavior that helps an organism survive its
environment
• Type of Adaptations
– Animals
• Camouflage, Mimicry
– Plants
– Antimicrobial Resistance
Animal Adaptations
Mimicry adaptation in which
one species evolves to
resemble another
species for protection
or other advantages
Animal Adaptations
• Fur Color - camouflage
Camouflage – adaptation that
allow organisms to blend into to
other structures
Camouflage
Camouflage – counter-shading
Plant Adaptations
Plants adapt to their environment
• Thorns
– To stop animals from eating them
• Thick stems and leaves
– To hold water
• Shape
– Hold water, attract insects
• Smell
– Attract and Deter
• Bright Colors
– Attract and Deter
• Creative Seeds
– To be carried by animals, water or wind
Sweet Gum Tree – Seed Pods
Maple Trees – helicopter seeds
Dandelions
Piture Plant
Bromelliad
Cactus
Succulent
Fragrant Flowers
Fragrant Flowers
Brightly-colored Flowers
Brightly-colored Flowers
Tropisms
Adaptations that help plants grow
4 Tropisms
•
•
•
•
Thigmotropism
Phototropism
Gravitropism
Hydrotropism
Thigmotropism
• How certain plants can grow and attach to
things that they touch
Phototropism
• Growth of a plant towards sunlight
Gravitropism
- helps the
roots grow
down and the
stems to grow
up
Hydrotropism
– growth of
roots toward
their water
source
Biological Resistance
• Antibiotics and Pesticides have been used
to kill unwanted insects, bateria and fungi
• Some of these organisms do not die when
exposed to the pesticides or antibiotics
– This makes them RESISTANT. The
RESISTANT organism then can pass on its
genes and RESISTANCE to future
generations, causing the current “POISON” to
be ineffective
Antibiotic Use
• Antibiotics used to be very effective
• However, people would stop taking the
antibiotic when they started feeling better
– …..but, not all of the bacteria were killed….so
those bacteria that lived had been exposed to
the antibiotic and developed a resistance to it
– The resistance was passed on to the next
generations….making the antibiotic ineffective
– Always finish a prescription that is an
ANTIBIOTIC
Patterns of Evolution
• Adaptive Radiation (Divergent Evolution)
– Very short time – one species gives rise to
many species in response to the creation of a
new habitat or ecological opportunity
• Coevolution
– Different species evolve in response to one
another
• Convergent Evolution
– Unrelated species evolve similar traits even
though they are in different parts of the world
Adaptive Radiation
Adaptive Radiation – all of these
birds share a common ancestor
Co-Evolution
Co-evolution – Yucca Moth and
Yucca Plant
Yucca flowers are a certain
shape so only that tiny
moth can pollinate them.
The moths lay their eggs in
the yucca flowers and the
larvae (caterpillars) live in
the developing ovary and
eat yucca seeds.
Convergent Evolution – similar
noses, but different species
Convergent Evolution – 2
different types of foxes that look
similar because they both live in
the desert