Download SPECIES CHANGE OVER TIME

Lesson 6.1
Objectives
 How scientists use fossils to learn about the history of
life
 How organisms evolved more complex forms over time
 About mass extinctions
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Fossil Record –
information provided by
fossil records and their
location.
Fossil record lets
scientists identify periods
during which different
species existed.
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Cyanobacteria – earliest
known organisms in the
fossil record
◦ Contained chlorophyll and
used photosynthesis to
make sugars from carbon
dioxide
◦ The bacteria produced
oxygen as a by-product of
photosynthesis
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The first eukaryotes were
single-celled
The oldest eukaryotes are
from algae that lived 2
billion years ago.
600 mya the first
multicellular animals
(jelly-fish like) evolved.
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Bacteria and algae –
first life forms on
land
Primitive insects –
first land-dwelling
animals
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The loss of all the members of a species
Mass extinctions – several periods of huge
numbers of species have become extinct in a
very short time
Permian extinction – the largest mass
extinction in Earth’s history.
Cretaceous Extinction – dinosaurs extinction
Lesson 6.2
Objectives
•About early ideas and observations on evolution
•How Darwin developed his theory of natural selection
•How new species arise

Refers to the process through which species
change over time
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French naturalist
Proposed that during the
organism’s lifetime, they
change in response to
their environment
Example – giraffes long
neck
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British naturalist
He published a book about a voyage in
Galapagos island
Beagle – the name of a British navy ship
The book described his observations about
how evolution works
Galapagos Island
Darwin observe several types of:
 Tortoises
 Finches
According to Darwin:
 Individuals that are best suited to their
environment survive and reproduce at a
higher rate than other members of species in
that environment
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Overproduction

Variation

Adaptation
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Selection
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Population – is a
group of similar
species
In nature, organisms
reproduce a lot but
not many can survive.
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Variation or
differences among
individuals
Genetic variation
happens when
offspring get a mix
of chromosomes
from both parents
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An inherited trait that gives an organism’s an
advantage in its particular environment
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Individuals that adapted in
their environment have a
good chance of survival.
The adaptive trait will be
passed on to their
offspring.
Overtime, the useful trait
will become more common
in the population
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The evolution of a
new species from
an existing
species.
Isolation is the key
factor that leads to
speciation
Lesson 6.3
Objectives
•How populations increase and decrease in size
•What factors affect population size and survival
•How species can become extinct
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All populations have the ability to grow
rapidly over time
Populations tend to remain about the same
size
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Population increase
through births and
immigration
Immigration – the
movement of
individuals into a
population
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Emigration – the
movement of
individuals out of the
population
Limiting factors:
RESOURCES
COMPETITION
PREDATORS
DISEASE
CATASTROPHIC EVENTS
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Lesson 6.4
Objectives
•How scientists develop theories
•About the evidence Darwin used to support the theory of
natural selection
•About additional evidence most scientists use today
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Theory – is an explanation of natural
phenomena based on a wide range of
scientific evidence
Ancestor – is an early form of an organism
from which later forms descend
Vestigial Organs – are structures that were
fully developed in ancestral organisms but
are reduced and unused in later species

Fossils provided evidence that species in the
past were very similar to species living in
Darwin’s time
 Vestigial
Organs similar structures
with different
functions
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Similarities in Development
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DNA contains the
information that
organisms need to
grow and to
maintain
themselves.
When organisms
reproduce, they
pass on their
genetic material to
their offspring