Chapter 9 Test Review
Natural Selection, Selective Breeding & Dichotomous Keys
Charles Darwin
Studied birds called finches on the Galapagos Islands
The finches had different beaks due to their different food sources
Organisms produce more offspring than can survive.
There is competition among offspring for food, space, and other
resources.
● Theory of natural selection: organisms that survive have variations
best suited for their environment.
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Can organisms vary?
Variations in organisms can be:
1. External
2. Behavioral
3. Physiological
Darwin’s theory of natural
selection:
● Organisms that survive
have variations best suited
for their environment.
Can you adapt to survive?
Adaptations for avoiding
predators:
● Camouflage
● Living in groups
● Sensitive hearing
Example of adaptations:
● Camouflage
● Camel producing little sweat
● Penguins having wings that look
like flippers
● Cheetahs having long, powerful
legs
● The Arctic snow hare having
white fur to blend in with snow
Vocab, anyone?
● Adaptation: a trait in an organism that helps it survive in its
environment
● Selective breeding: the process of choosing parent organisms for
the characteristics we want in their offspring
● Natural selection: the survival of the organisms that are
genetically best adapted to the environment
The Peppered Moth
● The peppered moths experienced a population shift in England
during the Industrial Revolution because:
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Soot-covered trees camouflaged the dark moths
The light colored moths became more visible
● This is an example of natural selection at work.
Adaptations, Adaptations, Adaptations
● The plant below has seeds attached by light, fluffy threads. This is an
adaptation for seed dispersal.
● To survive in the desert, some plants have a waxy coat on their leaves to avoid
water loss.
● Your teeth are an adaptation! Some animals, like sharks have very sharp teeth
to eat meat. Deer are herbivores, so their teeth are more flat to chew plants.
Dichotomous Keys
● The purpose of a dichotomous key is to identify an organism.
● If trying to identify leaves using a dichotomous key, you might
observe if the leave is compound or simple.
Classification Systems
● As you move from the species to kingdom level in the classification hierarchy
organisms become less closely related.
● As you move from the kingdom to species level in the classification hierarchy,
organisms become more closely related.
● There are several different types of bears that have been identified-Selenarctos thibetanus, Ursus americanus, Ursus arctos, and Ailuropoda
melanoluca. Which two species are more closely related?
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Ursus americanus and Ursus arctos
Selective Breeding
● Humans control selective breeding.
● Examples:
○ Breeding race horses
○ Breeding “designer” mutts like a Malti-poo, Puggle, or Yorkiepoo.
○ Breeding corn for a specific trait
An adaptation...
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An adaptation occurs when all
members of the population have the
favorable trait.
An adaptation helps a population of
species survive and reproduce in
their environment.
An adaption evolves from a mutation
and gives an advantage that
becomes common throughout the
population.
Natural Selection vs. Selective Breeding
A farmer notices that one of his cattle and
their offspring are eating weeds more
often than grasses. The farmer wants to
kill the weeds, but doesn’t want to use
dangerous chemicals to do so. What should
the farmer to do reduce the weeds?
The farmer should breed the cattle eating weeds to
produce more offspring with this desirable trait.
One species of lizards have have spikes on
their backs to defend themselves from
predators. In a population of lizards, a
few lizards do not have these spikes. Why
are the lizards that have spikes more
likely to produce offspring than the
spikeless lizards?
Lizards with the spikes will be better to defend
themselves.
Carolus Linnaeus
● In the 1700’s Carolus Linnaeus created a different classification system
based on similarities in structures.
● Called “the father of taxonomy”
● Latinized his own name from Carl Linne’
● Came up with a way to classify organisms with a two name naming
system (binomial nomenclature) that would be universal to scientist all
over the world.