Transcript Chapter 12 - Jamestown Public Schools

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2. Grab Chapter 12 Packet
Ch. 12
History of Life on Earth

Age of
Earth

1. 4.5 billion years ago Earth
was a fiery ball of rock

2. Surface of Earth cooled

3. Water vapor in air
condensed to form ocean
water where life first evolved
How did Life Begin?
 Measurin
g the Age
of Earth
 Scientist have measured
the age of the rocks found
on Earth using radiometric
dating
 The age of the rock is
measured based on how
much it has broken down
throughout the years
called radioactive decay
How did Life Begin?
 Measuring
the Age of
Earth
 Radioactive Decay of a rock’s
content of certain “isotopes” is
measured in Half-Lives
 Half Life
 Time it takes for one half of a
certain amount of radioisotope to
decay
 By measuring this, scientists can
calculate how many half lives have
passed since a rock was formed
How did Life Begin?
 Measuring
the Age of
Earth
The Theories – How Life
Began
 1.
Formation
of Life’s
Chemicals
 Nonliving matter was
energized by sun and
volcanic heat
 Caused chemical reaction to
produce simple organic
molecules
 Organics became more
complex
 First cells developed
The Theories – How Life
Began
 Primordial
Soup
Model
 Hypothesized that Earth’s
oceans were once filled with
organic molecules (“soup”)
 But, there was no oxygen in
the air: only nitrogen,
hydrogen, water, ammonia,
methane
The Theories – How Life
Began
 Primordial
Soup
Model
 Solar radiation, volcanic
eruptions, lightning excited
electrons in gases
 Electrons reacted with
Hydrogen in the air to form
organic molecules
 This hypothesis was actually
tested and SUPPORTED!
Results – found a complex collection of
organic molecules! Compounds included
life’s building blocks – amino acids, fatty
acids – Hypothesis Supported!
The Theories – How Life
Began
 Bubble
Model
 Scientists Louis Lerman hypothesized
that the key processes that formed the
chemicals needed for life took place
within bubbles on the oceans surface
 The bubbles contained the gases
needed to make organic molecules
 Chemical reactions took place inside
the bubbles and UV radiation made
this process occur quickly
 Lerman suggested this theory
occurred much more quickly than the
Primordial Soup Model
Whiteboard – Quick Questions
 According to scientists how old is the
Earth?
 After three half-lives of a radioisotope
have passed, how much of the original
isotope is undecayed?
(1)1/8
(2) ¾
(3) ½
 What is “Primordial Soup”?
(4) 7/8
When did the 1st Organisms
Form?
 Evolution of
Prokaryotes
 The best evidence we
have to study early life
are fossils
 Fossil- preserved remains
(bone, tooth, shell) or
imprint of an organism
from long ago
How did Life Begin?
 Evolution
of Prokaryotes
 Oldest fossils photosynthetic
prokaryotes
(cyanobacteria)
 2.5 billion years old
 Released oxygen into oceans
 Oxygen eventually escaped
into air as more and more was
produced
Quick Check - Prokaryotes
 Evolution
of Prokaryotes
 Hold up 1 finger if prokaryotes
do have a nucleus
 Hold up 2 fingers if they do not
 Hold up 1 finger if they are
unicellular
 Hold up 2 fingers if they are
multicellular
Two Groups of Prokaryotes
 Evolution
of Prokaryotes
 Eubacteria
 Cell walls contain peptidoglycan
 Cause disease and decay
 Ex: E.Coli
 Archaebacteria
 Cell walls lack peptidoglycan
 Unique lipid cell membranes
 The 1st eukaryotic cells evolved
from archaebacteria
The Evolution of Eukaryotes
 Evolution
of Eukaryotes
 About 1.5 million years ago the first
eukaryotes appeared
 With your shoulder partner try to come
up with 3 characteristics of Eukaryotes
 Eukaryotes
 Larger
 More Complex
 Internal Membranes
 DNA in a nucleus
 Mitochondria
 Chloroplasts
The Kingdoms
 Evolution
of Eukaryotes
 Biologist group all living things into six
kingdoms.
 The first two kingdoms are Eubacteria
and Archaebacteria
 TRY THIS
 Name the other four kingdoms
 Circle the kingdom you believe came first
before all the rest
 Protists – Fungi – Plants - Animals
The 1st Eukaryotes
 The first Eukaryotic Kingdom
were Protists
 Includes both multi and
unicellular organisms
 Single celled organisms STILL
carry out all of activities for life’s
processes (ex: metabolism,
homeostasis)
 Multicellular protists include
Algae
Extinction
 Mass
Extinctions
 Extinction- Death of all members of a
species
 Mass Extinction- Episode during which
large numbers of species become
extinct
 The fossil records show large
percentages of the Earth’s organisms
were becoming extinct
 A total of 5 have occurred
Extinction
 Mass
Extinctions
 Most devastating- end of
Permian period
 245 million years ago
 96% of all species became extinct
 Cause may have been worldwide
geological and weather changes
How did Life Begin?
 Mass
Extinctions
 Fifth mass extinction
 2/3 of all land species (including
dinosaurs) become extinct
Extinction
 Mass
Extinctions
 A sixth mass extinction event?
 May be currently occurring due to
destruction of tropical rain forests
by human activity
 Can you name the most recent
extinction or a species?
The Ozone Layer
 Ozone
Layer
 Life began in the oceans, why
did life suddenly form on land?
 UV radiation from the sun is harmful
 As cyanobacteria began supplying the
air with oxygen, chemical reactions in
the atmosphere created the ozone
 The Ozone layer blocked the UV
radiation and made the Earth’s land a
safe place to live
Whiteboard – Quick Questions
 Name the kingdom that includes
single and multicellular
organisms
 Yes or No would today’s
organisms exist if the mass
extinctions did not occur? Think
– Why or why not
 How did cyanobacteria
contribute to the beginning of
more complex life on Earth?
Do Now
 Grab a textbook
 Turn in Chapter 11 Take home
Exam
 p. 8 Wednesday DoNow
 **Don’t forget – Weekly Due
Friday
Section 3 – Gallery Walk
 Each group will be assigned a
section from Pages 265 – 268
 Make a poster of your section in
15 minutes
 Make sure you can answer your
questions
 We will walk around to each
groups poster and have 5
minutes to review and discuss
each
Section 3 – Gallery Walk
 Each group will be assigned a
section from Pages 265 – 268
 Sections:






Plants & Fungi on Land – p.265
Arthropods – p. 266
Fish – p.267
Amphibians – p.267
Reptiles – p.268
Mammals & Birds – p.268
Section 3 – Gallery Walk
 Each group will be assigned a
section
 Make a poster of your section in
15 minutes
 Make sure you can answer your
questions
 We will walk around to each
groups poster and have 5
minutes to review and discuss
each
How did Life Begin?
 Plants and
Fungi on
Land
 Plants evolved from photo.
bacteria
 Use sunlight to generate nutrients
 Cannot harvest materials from bare
rock
How did Life Begin?
 Plants and
Fungi on
Land
 Fungi
 Can harvest materials from bare
rock
 Cannot use sunlight to generate
nutrients
How did Life Begin?
 Plants and
Fungi on
Land
 Together, they form a mutualistic
relationship (both benefit)
 Mycorrhizae- fungus provides
minerals to plant, and plant
provides nutrients to fungi
How did Life Begin?
 Arthropods
 First animals to successfully
invade land (first most likely
scorpion)
 Hard, outer skeleton
 Segmented body
 Paired, jointed limbs
 Lobsters, crabs, insects, spiders
How did Life Begin?
 Arthropods
 Insects
 Most plentiful, diverse group on
Earth
 First to have wings and fly
 Efficient at searching for food,
mates and nesting sites
How did Life Begin?
 Vertebrate
s (animals
with a
backbone)
 A. Fishes
 First vertebrates- small jawless
fishes
 Jawed fish evolved- allowed
predation
 Most successful of living
vertebrates
 Developed into land dwellers
How did Life Begin?
 Vertebrate
s (animals
with a
backbone)
 B. Amphibians
 First land vertebrates (to come out
of sea)
 Smooth skinned, four legged
 Frogs, toads, salamanders
 Developed lungs for absorbing
oxygen from air
 Limbs derived from bones in fish
fins
 Strong, flexible internal skeleton for
walking
 Lay eggs in moist areas
How did Life Begin?
 Vertebrate
s (animals
with a
backbone)
 C. Reptiles
 Evolved from amphibians
 Snakes, lizards, turtles, crocodiles
 Watertight skin locks moisture in
while living on land
 Can lay eggs on dry land
How did Life Begin?
 Vertebrate
s (animals
with a
backbone)
 D. Mammals and Birds
 Evolved from reptiles
 5th mass extinction: only dinosaurs
that were ancestors to birds, small
reptiles and small mammals
survived
How did Life Begin?
 Continental
Drift
 Movement of land masses over
Earth’s surface through geologic
time
 Explains why there are Marsupials
in both Australia and South
America although they are
extremely far apart

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Assessment Three
 Summarize how ozone was important in
enabling organisms to live on land
 Name the first multicellular organisms that
colonized land
 Identify the first kinds of animals to live on
land
 Describe the first kinds of vertebrates that
inhabited land
 Defend the argument that invasion of land
could not have happened until well after the
evolution of cyanobacteria