Transcript Animal Adaptation and natural selection

Adaptations and Natural Selection
How Natural Selection,
Genetic Variation, and the
Environment Influence
Evolution
Charles Darwin’s theory of
evolution (the idea that organisms
change through time) challenged
prevailing 19th-century notions of
a static world.
• Previous explanations all linked to theology.
- Christianity’s Great Chain of Being
• Organisms were seen as IMMUTABLE (unaltered since creation).
• Assumed a very young Earth that was formed < 10,000 years ago.
• Catastrophes (e.g. the Noachian Deluge) explained the extinct
organisms found in the fossil record.
Darwin’s voyage aboard HMS Beagle.
• 1831-1836 trip around the world.
• Set out to document the “hand of God” in nature.
• Collected countless specimens and kept detailed notes.
Darwin saw many things that
were difficult to reconcile
with the prevailing view of a
young Earth and the
immutability life.
Blue-footed Booby
(Sula nebouxii)
Finches of
the
Galapagos
Islands
Returning home, Darwin married and
moved to a country home.
For the next 20 years, he published
books about his findings on the Beagle
and worked quietly on the “species
problem”.
Darwin knew about artificial selection, and argued
that a similar process must occur in nature.
Wild mustard
& domestic
cruciform
vegetables
Domestic dogs
Wild canids
This led him to the idea of natural selection.
Natural selection rests on three indisputable facts:
• Organisms produce more offspring than can survive.
• Individuals vary in their characteristics.
• Many characteristics are inherited by offspring from
their parents.
It follows logically that …
• Some individuals will be better suited to their
environment - they will survive and reproduce
more successfully than individuals without those
characteristics.
• Future generations will thus contain more genes
from better-suited individuals.
• As a result, characteristics will evolve over time
to resemble those of the better-suited ancestors.
Phylogeny of the Galapagos Finches
Fitness is the likelihood that an
individual will reproduce and/or the
number of offspring an individual
produces over its lifetime.
Adaptive trait or adaptation is a
trait that increases an individual’s
fitness.
Natural selection or survival of the
fittest states that individuals that are
better suited to the environment (the
best adaptations) survive and
reproduce more successfully.
Gypsy Moths in England
• industrial revolution - coal and other industrial factories
spewed out massive amounts of air pollutants
• The original color of the gypsy moths was a light gray;
• Tree trunks were darker colored from the air pollution.
• The dark gray gypsy, once at a disadvantage and quickly
eaten by predators, now survived and bred, while their
lighter counterparts were eaten.
• The gypsy moths didn't just decide one day to change
their color, at the basis of such a change was the concept
of Natural Selection.
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The development of pesticide resistance in insects is another
example of real-time evolutionary change.
Natural selection is also
responsible for:
• antibiotic resistance in
bacteria
• herbicide resistance of
weeds
• HIV resistance to antiretroviral drugs
Examples of Adaptations
1. Camouflage (Cryptic)
2. Disruptive Markings
3. Warning Coloration
3. Mating Coloration
5. Batesian Mimicry
6. Mullerian Mimicry
7. Automimicry
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Camouflage
Cryptic: Concealing form and
coloration which enables a
species to avoid its natural
predators by camouflage.
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Two examples of
camouflage in San
Diego County: A
canyon tree frog
(Hyla californiae)
on canyon wall
(left) and a desert
horned lizard
(Phrynosoma
platyrhinos) on a
sandy riverbed
Camouflage
These two katydids sitting on a tomato plant
are well camouflaged. Note the veins in the
wings that resemble leaves.
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Disruptive Markings
Disruptive Markings: The
markings on some insects,
reptiles and mammals make it
difficult to distinguish them
from shadows and branches or
from other members clustered
together. The stripes on a
zebra may appear quite
distinctive, but to a colorblind
lioness it is difficult to single
out an individual zebra among
a dense population in the
African grasslands.
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Warning Coloration
Warning Coloration: Insects
with an obnoxious quality (at
least to would-be predators),
such as bad taste, bad smell or
powerful sting, often exhibit
bright colors to warn of their
presence. Warning coloration
is well developed some insect,
including bees and wasps.
Small poison dart frogs of the
tropical rain forest also exhibit
warning coloration. These
frogs contain very toxins in
their skin
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Mating Coloration
Mating Coloration: Bright
colorations among the males
of some animals (particularly
the plumage of birds) gives
the male a definite advantage
in sexual selection and mate
attraction. Mating coloration
and behavior of the most "fit"
and aggressive males serves to
stabilize the population
density because only the most
sexually select males are able
to mate with females of the
species.
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Batesian Mimicry
Mimicry: One insect
(called a mimic) that is
perfectly palatable to its
predator resembles
another insect (called the
model) that is quite
disagreeable to the same
predator. There are
actually two types of
mimicry: Mimicry in
which the mimic is
essentially defenseless is
called Batesian Mimicry.
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
One of these insects is a
stinging honeybee and the other
is a harmless fly that mimics the
bee. Although the fly cannot
sting, it greatly resembles the
bee. Because of this remarkable
resemblance, some of the fly's
predators tend to leave it alone
Mullerian Mimicry
Mimicry in which the mimic
shares the same defensive
mechanism as the model is
called Mullerian mimicry.
The yellow jacket wasp and
bumblebee (Bombus) are
Mullerian mimics because
they both have bright yellow
and black colors and use
powerful stings as a
defensive mechanism.
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Automimicry
In automimicry, an animal
mimics parts of its own body.
For example, some snakes
have a tail that resembles their
head and a head that resemble
their tail. A predatory bird
swooping down on its prey
might miss its capture when
the prey suddenly moves in an
unexpected (backwards)
Automimicry is well
direction.
developed in Malaysian
lanternflies of the large insect
order Homoptera
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