Download - Adaptations and Natural Selection
Adaptations and Natural Selection
How Natural Selection, Genetic Variation, and the Environment
Influence Evolution Charles Darwins 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. - Christianitys 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. Darwins voyage aboard HMS Beagle.
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
individuals 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. 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 anti- retroviral drugs
Examples of Adaptations 1. Camouflage (Cryptic) 2
Examples of Adaptations 1. Camouflage (Cryptic) 2. Disruptive
Markings 3. Warning Coloration 3. Mating Coloration 5. Batesian
Mimicry MullerianMimicry 7. Automimicry Camouflage Cryptic:
Concealing form and coloration which enables a species to avoid its
natural predators by camouflage. 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. 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. 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 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.
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. 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.
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) direction. Automimicry is well developed in
Malaysian lanternflies of the large insect order Homoptera