Transcript Chapter 12 History of Life on Earth

Chapter 12 & 13
History of Life on Earth
& Evolution
Mrs. Cook
Biology
Hypothesis for How life Began
•1920’s- Russian Scientist A.I.Oparin, and British Scientist
J.B.S. Haldam
•Suggested that the early Earth’s oceans
contained large amounts of organic molecules.
•Known as “Primordial Soup” model.
•Thought that oceans were filled with many
different organic molecules, like a pot of soup.
•Hypothesized that there molecules formed
spontaneously in chemical reactions activated
by energy from solar radiation, volcanic
eruptions, & lightening.
Hypothesis for How life Began
• Operin and American Scientist, Harold Urey,
proposed that Earth’s early atmosphere lacked
oxygen.
• Instead believed it was rich in
-Nitrogen (N)
-Hydrogen gas (H2)
-Water vapor (H2O)
-Ammonia (NH3)
-Methane (CH4)
Hypothesis for How life Began
• 1953- Primordial Soup Model was tested by
Stanley Miller, who was working with Urey.
• Miller placed the gases that he and Urey
proposed existed on early Earth into a device.
Hypothesis for How life Began
• To stimulate Lighting- provided an electrical spark
• After a few days Miller found a complex collection
of organic molecules in his apparatus.
- amino acids
- fatty acids
- hydrocarbons
* Supported Hypothesis that some basic
chemicals of life could have formed
spontaneously.
Hypothesis for How life Began
• Reevaluating the Miller-Ulery Model
- Now know that some of the molecules were not
abundant when earth began such as ozone (O3),
which protects Earth from UV radiation.
- UV radiation would have destroyed ammonia and
methane.
- Without ammonia and methane key molecules
that Miller-Ulery proposed could not have been
made.
*Scientists don’t yet know where these molecules
came from.
http://www.youtube.com/watch?v=j9ZRHoawyOg show 1st 3 min
Hypothesis for How life Began
•
1986- geophysicist Louis Lerman suggested that the
key process that formed the chemicals needed for
life took place within bubbles on the ocean’s surface.
1. Gases were trapped in underwater bubbles
ammonia, methane…
2. Gases underwent chemical reactions & were
protected within the bubbles- resulting in amino
acids.
3. Gases were ejected into the atmosphere when
they burst on the ocean surface
4. Gases underwent further reactions when
exposed to UV radiation and lightening
5. Simple and complex compounds fell into the
oceans with rain.
How to Determine Earth’s Age
• Earth is around 4.5 billion years old.
• Measuring Earth’s Age
• Radiometric Dating- use radiometric isotopes in
a substance to estimate its age.
- Radioisotopes release energy in the form
of charged particles.
- The time it takes for these particles to be
given off helps to determine a substance’s
age.
- Half Life- the time it takes for one-half of
a given amount of radioactive decay.
How to Determine Earth’s Age
• When did the first organisms form?
Fossil- is a preserved or mineralized remains (bone,
tooth, or shell) or imprint of an organism that lived
long ago.
• Oldest know fossil, which are microscopic
prokaryotes, come from rock that is 2.5
billion years old.
Fossils
http://www.youtube.com/watch?v=1920gi3swe4
First Cells on Earth
• Cyanobacteria
- first prokaryotic cells on earth
- photosynthetic
- released oxygen in oceans
- after hundreds of millions of years,
oxygen escaped into the air
First Cells on Earth
• Evolution of Prokaryotes
• Two Groups
• Eubacteria - contain a chemical called
peptidoglycan in their cell
walls
- include bacteria that cause disease
and decay
• Archaebacteria- prokaryotes that lack
peptidoglycan in their cell walls &
have unique lipids in their cell
membranes.
- still found today
First Cells on Earth
• The Evolution of Eukaryotes
• 1.5 billion years ago the first Eukaryotes appeared
• Much larger than Prokaryotes
• Complex system of internal membranes
• DNA in a nucleus
• Have mitochondria
• Plants and Protists have Chloroplasts
• Mitochondria & Chroloplasts have their own DNA
First Cells on Earth
• The Origin of Mitochondria and Chloroplasts
- 1966- American Biologist Lynn Margulis- proposed
the Theory of Endosymbiosis.
- states that mitochondria are the
descendants of symbiotic, aerobic (oxygen required)
eubacteria and chloroplasts are the descendants of
symbiotic, photosynthetic eubacteria.
- bacteria entered larger cell as a parasite or
an undigested prey.
- instead of being digested, the bacteria
began to live inside the host cell.
First Cells on Earth
• Support of theory for Mitochondria & Chloroplasts:
1. Same Size and Structure as bacteria
2. Genetic Material- circular DNA present
3. Ribosomes- present
4. Reproduction- produced with in eukaryotic cells by
binary fission.
http://www.youtube.com/watch?v=RaAM8qQcs6E
Multicellular Organisms
• Protists:
make up a large, varied group that includes
both multicellular and unicellular organisms.
• Fungi, Plants and Animals:
make up half the biomass (total weight of all
living things) on earth.
• Most organisms that exist today probably originated
during a relatively short time (10-100 million years).
- Precambian and Early Cambian periods known as
the Cambian Explosion.
Mass Extinctions
• About 440 million years ago, a large percentage of the
organisms on Earth suddenly became extinct.
-Extinction- is the death of all members of a
species.
-Mass Extinction- is an episode where large
numbers of species become extinct.
• There are 5 major extinctions recorded. The latest
was 65 million years ago & brought the extinction of
about 2/3 of all land species & the dinosaurs.
• Scientists believe we are in the mist of another
extinction due to human activity- ex. Destruction of
the Tropical Rain Forests will lead to extinction of
vegetation, birds, insects & other wild life.
http://www.youtube.com/watch?v=ON-m4Yqd7ds
The Ozone Layer
• Before the Ozone layer was formed, organisms were
sequestered to the ocean, where they were protected
from UV radiation.
• 2.5 billion years ago, photosynthesis by cyanobacteria
began adding oxygen to Earth’s atmosphere. O2 reacted
with the sun’s radiation to form O3 or ozone.
• The upper atmosphere blocks the Ultra Violet
radiation of the sun.
• After millions of years Ozone has made Earth a
safe place to live….
….But you Still need to wear sunscreen!
Life on Earth
• First Multicellular Organisms was Fungi living together
with plants and algae.
• 100 million years after first union with fungi, plants
covered the earth forming large forests.
• Land plants provided food source for land-dwelling
animals.
• Arthropods- first animals to successfully make land.
-hard outer skeleton, segmented bodies, and paired,
jointed limbs. (lobsters, crabs, insects, spiders.)
Life on Earth
• First Vertebrates- (animals with a backbone)
• 530 million years ago, small, jawless fish
• 430 million years ago, small jawed fish
• Fish are most successful living vertebrates
• 370 million years ago- Amphibians
-today include frogs, toads & salamanders
• 340 Million Years ago- Reptiles
-today includes snakes, lizards, turtles, &
crocodiles
• 65 Million years ago- birds and small mammals
Continental Drift
• The movement of Earth’s land masses over Earth’s
surface through geologic time.
• Results in the present day position of the continents.
http://www.youtube.com/watch?v=uGcDed4xVD4
http://www.youtube.com/watch?v=TzzGPfVx32M
PART II- Evolution Chapter 13
Pre-Darwin Ideas
• 18th Century Europe: Most scientists believed that all
species were permanent and unchanging.
• They also believed that the Earth was only thousands
(and not billions) of years old.
• By 1800s, scientists in Europe began to study Strata- or
Rock Layers
Pre-Darwin Ideas
• Georges Cuvier (1769-1832) reconstructed unique
organisms from fossils that he found in the layers
• He suggested that the lower the level, or older, the more
different these organisms were to modern organisms.
• He found sudden changes in the organisms and
suggested extinctions occurred in the past
• Not all of his explanations are still accepted, but he
contributed to scientific evidence that geological change
and extinction had occurred.
Pre-Darwin Ideas
• Charles Lyell (1797-1875) Worked with the idea of
uniformitarianism. That geological processes have
changed the shape of Earth’s surface in the past &
continue to work in the same ways today.
• Pangaea
Pre-Darwin Ideas
• Jean Baptiste Lamark (1744-1829) Supported the idea
that populations change over time.
• He thought that simple organisms could arise from nonliving matter
• And that simple forms of life inevitably develop into more
complex forms
• He also thought individuals could acquire traits in their
lifetime and pass those traits on to their offspring.
The ideas of Charles Darwin (1809-1882)
• Mid 1800’s, Charles Darwin and Alfred Russel
Wallace formed a new theory to explain how evolution
took place.
• Darwin began his theory while on his voyage on the
HMS Beagle, which he noticed the locations of similar
organisms around the world. He also noticed that
species varied based on their environment.
• He spent much of his time at the Galapagos
islands off the coast of South America
• He studied 13 species of Finches on the different
islands and used this as his argument for Natural
Selection
The ideas of Charles Darwin
• In 1859, Darwin Published a book entitled On the Origin
of Species by Means of Natural Selection.
• He wanted to give evidence that evolution occurs
• And to explain the variety and distribution of organisms
on Earth in the terms of Natural Processes that are
observable everyday.
• Darwin used the phrase decent with modification to
describe evolution- he said that every species, living or
extinct must have descended from a previous species
(or a common ancestor) and that species must be able
to change over time.
Natural Selection
• Natural Selection• Process by which individuals that are better
adapted to their environment survive and
reproduce more successfully than less well
adapted individuals do
• It is also a theory to explain the mechanism for
evolution.
Four Main Parts of Darwin’s Reasoning
1. Overproduction- more offspring can be produced than
can survive to maturity; the environment limits the
populations of all organisms by causing deaths or by
limiting births.
http://www.youtube.com/watch?v=3AZKixtQz_Q
Four Main Parts of Darwin’s Reasoning
2. Genetic Variation- within a population, individuals have
different traits; occasionally new traits may appear in a
population due to mutations, crossing over, random
fertilization, independent assortment.
3. Struggle to Survive- individuals must compete with
each other in a “struggle for existence”. Some traits
improve and individual’s chance to survive while other
traits reduce this chance.
• A trait that makes an individual successful in its
environment is called an Adaptation.
Four Main Parts of Darwin’s Reasoning
4. Differential Reproduction- organisms with the best
adaptations are most likely to survive and reproduce and
through inheritance, the adaptations will become more
frequent in the population.
• Populations may begin to differ as they become
adapted to different environments, even if they
descend from the same ancestors.
Natural Selection
• The theory of Natural Selection proposes that nature
changes species by selecting traits
• Darwin sometimes used the phrase
“Survival of the Fittest” to explain Natural Selection.
• In evolutionary terms, Fitness is a measure of an
individual’s hereditary contribution to the next
generation.
Evidence of Evolution
1. Biogeography is the study of the locations of organisms
around the world. Fossil Records and live organisms are
used.
Evidence of Evolution
2. Anatomy and
Embryology
• Anatomy is the
study of the body
structure of
organisms
• Embryology is the
study of how
organisms
develop
Evidence of Evolution
3. Homologous Structures- are the anatomical structures
that occur in different species and that originate by
heredity from a structure in the most recent common
ancestor of the species
• Often have a related structure even if their functions
differ between species
• Example: the forelimbs of vertebrates
Evidence of Evolution
4. Analogous structures- have closely related functions
but do not derive from the same ancestral structure.
• Examples: wings of birds, bats, and moths
Evidence of Evolution
5. Vestigial Structures- seem to serve no function but that
resemble structures with functional roles in related
organisms.
• Examples: human tailbone, pelvic bones of modern
whales, and the human appendix.
Evidence of Evolution
6. Biological Molecules- in all species, DNA and RNA are
the molecular basis for inheritance of traits.
• You can compare the DNA and RNA of different
species- the greater the number of similarities
between any given species, the more closely the
species are related through a common ancestor.
Types of Evolution
1. Convergent Evolution- is the process by which different
species evolve similar traits.
Types of Evolution
2. Divergent Evolution- is a process in which the
descendents of a single ancestor diversify into species
that each fit different parts of the environment
• Example: Darwin’s finches
Types of Evolution
• Sometimes a new population in a new environment
will undergo divergent evolution until the population
fills many parts of the environment. This pattern of
divergence is called Adaptive Radiation or founders
affect.
• Example: Caribbean anole lizards
http://www.youtube.com/watch?v=9x8lFXgXmZI
Types of Evolution
3. Artificial Selection- is a process when a Human
Breeder chooses individuals that will parent the next
generation with select desirable traits
• Example: breeding dogs, cats, horses
• AKA- Selective Breeding
Types of Evolution
4. Coevolution is when two or more species have evolved
adaptations to each other’s influence
• Evolution is ongoing and many species can be
evolving at once
• Each species is part of the forces of natural selection
that act upon the other species
• Examples: humans have developed and used
antibiotics but many bacteria have evolved
adaptations to resist the effects of some antibiotics.