Chapter 6
Evolution (p. 154)
I can:
• Understand the concept of evolution (change) by natural
selection.
• Describe Charles Darwin’s contribution to the foundation
of biology.
• Explain the relationship of artificial selection to natural
selection.
• Know the key points of evolution.
Species - is a group of organisms that share
similar characteristics and can reproduce
among themselves and produce “viable”
offspring.
Evolution – the
change of inherited
characteristics in an
organism over time.
EVOLUTION OF HORSES
55 MILLION YEARS AGO TO TODAY
Horse Legs
The habitat is changing from moist forest
to arid grassland. The fastest horses survive.
All organisms evolve as climate and
habitat changes. Those best suited
to the conditions, survive and pass
those traits to their offspring.
Jean Baptiste de Lamarck’s hypothesis on
the inheritance of aquired traits. (1809)
- said that the offspring keep the traits
that their parents developed during
their lives and lost the traits that were
not used.
Dad
- the theory was rejected
Son
Evolution by Natural Selection.
Charles Darwin: 1850’s
- organisms with traits
best suited to their
environment are more
likely to survive and
reproduce.
Darwin was the naturalist aboard the HMS Beagle
-surveying the east and west coasts of
South America.
Darwin’s voyage in 1831 to 1836
Darwin:
was gone for 5 years,
he spent 5 weeks in the
Galapagos Islands.
The Galapagos Islands are 600 miles off the
coast of Ecuador.
Galopogos Islands.
The species of animals that Darwin found on the
Islands bore similarities to those found on South
America and to each other.
Darwin saw huge tortoises, similar to: but different
from tortoises on the mainland. He could tell what
island a tortoise was from by its shell pattern.
Ecuador
Galapagos
Darwin really noticed the differences
between the finches.was the variety of
Finches.
-there are 13 species.
What is different
about them?
Their beaks were shaped differently. They
adapted to the available food on each island.
- Seed eaters (thick beak)
- Insect eaters (long beak)
- Bud eaters
It’s all about the beak.
They are of different
shapes, and they feed
on different foods.
One even uses a
tool to pick insects
out of cracks.
Ancestor:Grassquit
Adaptation and Variation
Variation:
- is an inherited trait that makes an
individual different from other
members of the same species. (variety)
It gives nature something to pick from!
Variation
Some variations could be harmful.
Albino – no pigments.
- easily seen by predators – their trait is not
passed on to offspring.
Adaptation
- is any variation that makes
an organism better suited to it’s
environment
-more likely to survive and
reproduce and pass on these
traits.
Ex. color, shape, behavior
Ex. Peppered moth in England
The coal from
the Industrial
Revolution
turned the tree
trunks darker
- the dark moth became
more common as it could
‘hide’ from predators.
(great example of natural selection)
Modern coal plants are much cleaner.
Camouflaged Scorpion Fish
Questions
Page 161 1/3/5
Page 169 1
Page 178 8/12
Sources of Variations in Populations p. 159
1. Mutations of the genetic code.
2. Movement of new individuals
into a population.
- they can have different traits.
3. Geographic Isolation (p. 159)
- when a population is separated
from other populations.
- by mountains, rivers, etc
-eventually the populations become
so different they can no longer
reproduce with each other.
In 1856 Darwin published his book:
“On the Origin of Species by Means
of Natural Selection”
It has become one
of the most
influential and
controversial
books ever
written
Darwin’s Principles of Natural Selection
• Organisms must produce more offspring than
can survive.
• Variation must occur in the population.
• The variations must be inheritable.
• The variation must make the individual more
able to survive and pass this trait to offspring.
• The variation must become common in the
population
What if a hare was born with an allele that
caused it’s fur to not change color with
the change of seasons? How would
would it’s survival be affected?
What if the climate changed?…and it did
not snow?
Artificial Selection
- people select the traits they want
in an organism through breeding.
The Speed of Evolution
- some scientists say it takes millions of
years.
- some say it happens quickly.
- some say it is both.
1. Gradualism
- the slow change of a species to
another new species
Ex. horses
- evidence in the
fossil record..
Ex. camels
Worksheet
“Natural Selection”
2. Punctuated Equilibrium:
- the rapid evolution of a species, usually
due to a huge change in the environment
ex. bacteria becoming antibiotic
resistant.
ex. peppered moths.
gradualism
Punctuated
Equilibrium
EVIDENCE FOR EVOLUTION
1. Fossils
- the remains of life
from an earlier time.
Insect in amber - 45 million
years old
Clam – 400 million years old
Most fossils are found in sedimentary rock
Ex. limestone / sandstone
- sand / silt / clay are
compacted and
cemented together.
Archaeopteryx: a transitional fossil, the link
between dinosaurs and birds.
Determining a Fossil’s Age
A) Relative Dating
-the oldest fossils are at
the bottom layer
B) Radiometric Dating
• Rocks contain a small amount of radioactive elements that
decay at a certain rate
• By finding how much of it remains can date the rock
Worksheet
“Evolution”
2. Embryology
- the study of embryos
and their development.
- mammals, birds,
fish and reptiles
share similar traits.
3. Homologous Structures
- body parts that are similar in structure and origin.
- can indicate the species share a common ancestor.
4. Vestigial Structures
- organs that seem to
not have a function.
Ex. appendix
-but once functioned
in their ancestors.
Ex. whale – pelvic bones for legs.
ex. ear muscles to rotate ears
5. DNA
- by studying DNA sequences, scientists can determine
how closely organisms are related.
Chapter 6
Evolution (p. 154)
I can:
• Understand the concept of evolution (change) by natural
selection.
• Describe Charles Darwin’s contribution to the foundation
of biology.
• Explain the relationship of artificial selection to natural
selection.
• Know the key points of evolution.
Geologic Time Scale p.164
Scientist’s divide the earth’s history into
eras and periods.
Cenozoic: present to 65 million
Mesozoic: 65 million to 250 million
Paleozoic: 250 million to 400 million
Precambrian: 400 million to 4 billion
225m.
65m
125m
present
The amazing thing is not that we don’t have
more fossils, but that we have any at all.
It requires a unique series of events to cause
a life form to be preserved…
6.3 Primate Evolution
Some Traits all primates share:
• Opposable thumbs
• Binocular vision
• Rotating forelimbs and shoulders
• Increasing brain size
• Flat finger nails.
Primates are divided into 2 major groups:
Prosimians
Higher Primates
Lemurs
Tarsier
Monkeys
Apes
Hominids
Hominids:
• ate both meat and vegetables
•Primates: Walked upright on 2 feet.
•They had a larger brain.
Australopithicus: (Lucy) = Southern ape
• hominid
•3 million yrs old.
•Small brain
•Human-like jaws and teeth.
•From Africa
Homo habilis = handyman
•2 million yrs old
•Used stone tools
•Direct human ancestor.
Homo erectus:
•Larger brain
•About 1.5 million years old.
•Migrated out of Africa 1 million
years ago.
Homo sapiens = wise human
250,000 years ago.
By 125,000 years ago 2 groups of
Homo sapiens lived in Africa and Europe.
Modern humans left Africa 60,000 years
ago in several migrations.
Neanderthal
Short heavy body
Massive bones
Cro Magnon
In Europe 40,000+ yrs
Cave art
Cared for the elderly
Family groups in caves Buried their dead
Well made tools
They are Us
Adapted to cold weather.
Extinct 35,000 yrs.
neanderthal
Cro magnon
Direct
Ancestor
To humans
6.4 Extinction: the dying out of species.
Extinction occurs naturally because the
environment is always changing. Those
individuals unable to survive are naturally
removed.
There have been 5+ mass extinctions in the
earths history, each followed by an explosion
of new species that evolved rapidly to fill the
empty environment.
Endangered species: organisms with so
few individuals left they are in danger of
extinction.
Since the 1500s over 500 species have
become extinct in the U.S. alone.
There are now 1090 animals
1838+ plants worldwide
on the endangered species list.
In the States alone there are:
398 animals and 599 plants in
immediate danger of becoming extinct.
All but 3 are considered to be the result
of human action.
Based on past rates of extinction, most
life scientists agree that we are now
in another age of mass extinction.
We are changing the environment by
our actions.