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Ideas About Evolution
A.
Evolution:
changes in inherited
characteristics of a
species over time

SPECIES: is a group
of organisms
–
–
share similar
characteristics
can reproduce
among themselves
Lamarck's the Hypothesis of
Acquired Characteristics
–Traits acquired by parents => offspring
(large muscles)
–was not supported by evidence.
Charles Darwin
–
–
hypothesized that plants
and animals on Galapagos
Islands came from Central
and South America.
Observed that species of
finches on the islands
looked similar to a
mainland finch species.
Darwin’s Voyage
Map
DARWIN’S THEORY
– Reasoned that
members of a
population best able
to survive and
reproduce will pass
their traits to the
next generation;
over time, differences
can result in separate
species.
– Published in book,
Origin of Species, in
1859
Theory of Evolution by
Natural Selection
Darwin’s observations => experiments by
other Scientists => theory
 Natural Selection: organisms with traits
best suited to their environment will more
likely survive and reproduce.

Variation and Adaptation


Variation: an inherited trait that makes an
individual different from other members of its
species
Adaptation: is a variation that makes an
organism better suited to its environment.
–
–
Many kinds of environmental factors can cause
changes in the sources of genes.
Geographic Isolation can make two populations so
different they become different species.
Speed of Evolution


Scientists disagree on speed of evolution
Evidence supports both
– Gradualism Model: describes evolution as
a slow, ongoing process
– Punctuated Equilibrium model: gene
mutation can result in a new species in a
relatively short time.
Clues about
Evolution


Fossils found in sedimentary rock show
evidence that living things evolved.
Fossil age can be determined by two basic
methods.
–
–
Relative Dating looks at fossil location in a
particular layer of rock; older rock layers are
under newer rock layers.
Radiometric Dating: compares the amount of
radioactive element with the amount of
nonradioactive element in a rock.

Fossil records have gaps.
– Incomplete rock record; most
organisms do not become fossils.
– Enough fossils have been
discovered for scientists to
conclude that complex organisms
appeared later than simpler ones.
– Most organisms that ever existed
are now extinct.
More Clues…
Direct evidence, such as the
development of
antibiotic resistance in bacteria,
supports evolution.
Example:
•Pesticide-resistant insect species
Indirect Evidence

Supports idea –
does NOT provide
proof
–
Embryology: the
study of embryos
and their
development, shows
similarities among all
vertebrate species.
– Homologous body
parts can indicate
two or more species
share common
ancestors.
Vestigial
structures that
don't seem to have
a function but
might have once
functioned in an
ancestor
– DNA can provide evidence about how closely
related organisms are.
Evolution of Primates

Primates—group of mammals with
opposable thumbs, binocular vision, and
flexible shoulders
– Hominids - appeared about 4 to 6 million
years ago and had larger brains than apes.
– Fossils, such as Australopithecus, point to
Africa as the origin of hominids.
– Homo habilis and Homo erectus are thought
to be early human ancestors
Lucy Fossil
Adaptations Over Time

Homo Sapiens began evolving about 400,000
years ago.
–
Neanderthals had short, heavy bodies with thick
bones, small chins, and heavy brow ridges.


–
Disappeared about 30,000 years ago
Not thought to be direct ancestors of modern humans
Cro-Magnon Human fossils date from around
10,000 to 40,000 years ago;


thought to be direct ancestors of early Homo sapiens.
Cave Men
Neandrathal vs. Cro-Magnon
Reviewing Main Ideas
3
The Evolution of Primates
• Primates include monkeys, apes, and
humans. Hominids are humanlike primates.
• The earliest known hominid fossil is
Australopithecus.
• Homo sapiens are thought to have evolved
from Cro-Magnon humans about 400,000
years ago.
Chapter Review
Question 1
Charles Darwin observed that the beak shape
of each species of finch is related to its eating
habits. Which beak would best be used for
probing beneath tree bark?
A. long, slender
B. long, fat
C. medium-sized
D. short, strong
Chapter Review
Answer
The answer is A. A long, slender beak would
be best for probing beneath tree bark.
Chapter Review
Question 2
What would a short, strong beak be best used
for?
A. eating insects
B. drinking nectar
C. prying insects out of small holes
D. breaking hard shells
Chapter Review
Answer
The answer is D. Finches that eat nuts and
seeds have short, stout, “crushing” beaks.
Chapter Review
Question 3
A _______ is an inherited trait that makes an
individual different from other members of its
species.
Answer
The answer is variation. Variations result from
permanent changes, or mutations, in an
organism’s genes.
Chapter Review
Question 4
_______ are scientists who study the past by
collecting and examining fossils.
A. Biologists
B. Entomologists
C. Ecologists
D. Paleontologists
Chapter Review
Answer
The answer is D. Paleontologists study fossils
in order to learn which plants and animals
lived during various periods of Earth’s history.
Chapter Review
Question 5
_______ and _______ are two basic methods
used to estimate the ages of rocks and fossils?
Chapter Review
Answer
The answer is relative dating and radiometric
dating. Relative dating is based on rock layers
and radiometric dating compares the amount
of radioactive element with the amount of
nonradioactive element in the rock.
Standardized Test Practice
Question 1
Which is an imprint on sediment that later
hardens to become rock?
A. cast fossil
B. frozen fossil
C. imprint fossil
D. mineralized fossil
Standardized Test Practice
Answer
The answer is C. A leaf, feather, bones, or
even the entire body of an organism can leave
an imprint on sediment that later hardens to
become rock.
Standardized Test Practice
Question 2
Which is NOT an example of an adaptation?
A. albinism
B. camouflage
C. hibernation
D. nocturnal behavior
Standardized Test Practice
Answer
The answer is A. An adaptation is any
variation that makes an organism better suited
to its environment. Albinism prevents an
organism from blending into its environment.
Standardized Test Practice
Question 3
Which is the best example of punctuated
equilibrium?
A. alligator evolution
B. camel evolution
C. human evolution
D. penicillin-resistant bacteria
Standardized Test Practice
Question 4
According to the Principles
of Natural Selection, which
of the following is the best
answer?
Standardized Test Practice
A. Organisms produce
just enough offspring
to survive.
B. All variations are
helpful.
Standardized Test Practice
C. Organisms with traits
best suited to their
environment are more
likely to survive.
D. Variations are never
passed to offspring.
Standardized Test Practice
Answer
The answer is C. Organisms produce more
offspring that can survive, not all variations
are helpful, and some variations are passed to
offspring.
Standardized Test Practice
Question 5
Body parts that are similar in origin and
structure are called _______.
A. homologous
B. hominids
C. sedimentary
D. vestigial