Download 3. In complete sentences tell what Pasteur did in the

Spontaneous Generation
• The idea that life arises from non life
ex. Damp hay and corn in a dark corner
give rise to mice.
• Francesco Redi showed that flies and
maggots did NOT arise spontaneously
from rotting meat.
• Redi hypothesized
that flies, no meat,
produced other flies.
• In a closed jar with
meat in it, no flies
were produced.
• In an open jar,
maggots formed,
leading to flies.
Theory of Biogenesis
• States only living organisms can produce
other living organisms.
Pasteur’s Experiment
• Pasteur’s experiment showed that sterile
broth remained free of microorganisms
until exposed to air.
Origin of Life
• Alexander Oparin and John Haldane
suggested the primordial soup hypothesis
about the origin of life.
• They thought that if Earth’s early
atmosphere had a mixture of certain
gases, organic molecules could have
been synthesized from simple reactions.
• They thought the sun and lightning might
have been the energy sources.
Miller/Urey Experiment
Miller/Urey Experiment
• The two scientist took the hypothesis
proposed by Oparin and Haldene and
tested it with a glass apparatus.
• They showed for the first time that organic
molecules could be produced from gases
proposed to have made up the
atmosphere of early Earth.
Earth’s early Atmosphere
• Gases that likely made up earth’s early
atmosphere:
• H2O –Water
• CO2-Carbon Dioxide
• SO2- Sulfur Dioxide
• CO-Carbon Dioxide
• H2S-Hydrogen Sulfide
• HCN-Hydrogen Cyanide
• H2-Hydrogen
• NO FREE OXYGEN (O2)
How the first organic molecule
originated:
• Amino acids are not sufficient for life.
• Life requires proteins (many amino acids
link together to form a protein)
• In the Miller/Urey experiment amino acids
could link together, but did not stay linked.
• One possible mechanism for linking them
together would be clay sediment.
First Genetic Code
• RNA was life’s first coding system.
• All organisms contain RNA.
• RNA sequences have changed little over
the time.
• RNA can behave like an enzyme.
• Some scientists hypothesize that clay
particles could have provided the initial
template for RNA replication.
Cellular Evolution
• Fossilized microbes were found in rock 3.5
billion years old.
• This proves that cellular activity had
become established very early in Earth’s
history.
• Also suggested that early life might have
been linked to volcanic environments.
The First Cells
•
•
First cells were prokaryotic.
Recall that prokaryotic cells are:
– Smaller than eukaryotic cells
– Lack defined nucleus and other organelles
There are two types of prokaryotic cells:
1. Eubacteria
2. Archeabacteria
Archeabacteria
• Closest relative to Earth’s first cells.
• Live in extreme environments, such as hot
springs of Yellow Stone park or the
volcanic vents of the deep seea.
• Live in environments similar to earth’s
early atmosphere.
• Can live without oxygen.
• Chemoautotrophs-get there energy from
chemicals.
Introduction of Oxygen to Earth’s
Atmosphere
• 1.8 billion years ago oxygen appeared in
the atmosphere.
• The oxygen normally combined with iron
to produce iron oxide.
• Earth’s free iron was saturated with free
oxygen.
• This caused oxygen to start accumulating
in earth’s atmosphere.
Photosynthesizing Bacteria
• Photosynthesizing prokaryotes evolved
not long after the archaea.
• Primitive photosynthesizing prokaryotes
were called cyanobacteria.
• Cyanobacteria eventually produced
enough oxygen to support the formation of
an ozone layer.
• This eventually lead to right condition for
the appearance of eukaryotic cells.
Endosymbiont Theory
• Eukaryotic Cells appeared in fossil record about
1.8 billion years ago. (same time when oxygen
appeared)
• Recall that Eukaryotic cells:
- Have a nucleus and membrane bound
organelles.
- Remember mitochondria is the site of cellular
respiration and chloroplasts (Found only in plant
cells) are the site of photosynthesis.
_
• Both mitochondria and chloroplasts are
the same size has prokaryotic cells.
• The contain prokaryotic features that lead
scientist to believe that prokarytoic cells
were involved in the evolution of
eukaryotic cells.
Endosymbiont Theory
• 1966 biologist Lynn Margulis proposed the
endosymbiont theory.
• According to this theory, eukaryotic cells
lived in association with prokaryotic cells.
• In some cases, prokaryotic cells lived
inside of eukaryotic cells.
• Could have entered the cell through
endocytosis (like most large molecules)
• The relationship was mutually beneficial and eventually
the prokaryotic cells became the organelles in Eukaryotic
cells.
• EVIDENCE TO SUPPORT THEORY
-Mitochondria and chloroplasts have their own circular
DNA (just like prokaryotic cells)
-Mitochondria and chloroplasts have their own ribosomes
that resembles prokaryotic ribosomes.
- Mitochondria and chloroplasts reproduce asexually by
fission, independent from the rest of the cell.
The Origins of Evolutionary Theory
• Evolution refers to the process by which a
species of organisms change over time.
• The concept of evolutionary change in
organisms is most often associated with
the British naturalist Charles Darwin.
• Darwin published the book On the Origin
of Species by Natural Selection in 1859.
• Darwin’s ideas built on the work of several
other scientists working in a variety of
fields.
1. Charles Bonnet:
• The Swiss naturalist Charles Bonnet is
credited with being the first person to use
the term evolution to refer to organisms.
• Bonnet was studying fossils when he
noticed that many of the fossils he
examined did not resemble any living
animals.
• Bonnet developed a hypothesis called
catastrophism to explain these
observations. His hypothesis included two
main ideas:
1. Earth was subjected to periodic
catastrophes that affected the entire
planet, killing all living things. Fossils were
the remains of those now dead life forms.
2. Following each catastrophe, new life
emerged. All these new life forms were
slight improvements over earlier life forms.
These improved life forms resulted from
evolution.
2. Jean-Baptiste Lamarck:
• In 1809, the French biologist JeanBaptiste Lamarck proposed a new theory
of evolution. Lamarck thought that
organisms evolved by acquiring
characteristics during their lifetimes and
then passing on those traits to their
offspring. The classic example of
Lamarck’s theory of inheritance of
acquired traits is the giraffe.
• Lamarck believed that organisms changed due
to the demands of their environments.
• In the case of giraffes, Lamarck proposed that
the neck of the giraffe become longer during its
lifetime because it had to stretch to reach leaves
on high branches.
• He also thought that those giraffes passed the
acquired trait of a longer neck to their offspring.
As a result, over many generations, all giraffes
acquired long necks.
• A second part of Lamarck’s theory is the
principle of use and disuse.
• Lamarck that the parts of its body an
organism used became stronger and
would be passed on to offspring.
• By contrast, if an organism did not use a
part of its body, that structure would
disappear or be lost in future generations.
Influences on Darwin
• In 1831, the British ship H.M.S Beagle set
sail on a scientific expedition that covered
nearly 65,000 kilometers over five years.
Charles Darwin was the naturalist for the
expedition. Darwin’s main job was to
identify areas suitable for mining.
• Darwin was heavily influenced by the
readings of two scientists while on his trip:
Charles Lyell:
1. During the expedition, Darwin read
Charles Lyell’s book Principles of
Geology.
• Geology is the scientific study of Earth
and its features.
• The planet’s great age is important to
understanding both geological and
biological evolution.
2. Thomas Malthus
• Darwin also read Thomas Malthus’s An
Essay on the Principle of Population.
• Malthus wrote that populations will
naturally outgrow their food resources,
leading to competition for food.
• Organisms will compete for food both with
members of their own species and with
organisms of other species.
Darwin’s Observations
• Darwin notices a great diversity and a
very large number of species. In a South
American rain forest, he collected 68
different species of beetles in one day.
• Darwin observed that plants and animals
were suited to the environments in which
they lived.
• 3. He noticed that different species live in similar
ecosystems. For example, Darwin compared
grasslands in South America and Australia. The
grasslands on the two continents on the two
continents had very different animals.
• 4. During his voyage, Darwin began to look at
the fossil record. He collected many fossils in
South America. When he examined his finds, he
observed that some of the fossils resembled
modern animals. Others looked very different
from any modern organisms.
• Darwin observed the different plants and
animals on a group of islands called the
Galapagos.
• The islands are close together, but their climates
differ greatly.
• The low-lying islands are dry, hot, and sparsely
vegetated.
• The islands that have higher elevations get more
rain and have much more diverse plant life.
• Darwin also studied the animals of the
Galapagos.
• He saw that the shells of land tortoises differed
depending on where they lived.
• Tortoises with dome-shaped shells and shorter
necks (domed tortoises) lived on wet, highly
vegetated islands, where they did not need to
stretch to reach food.
• On the other hand, tortoises with curved shells
and long necks (saddleback tortoises) lived on
drier islands. Those tortoises had to stretch to
reach the sparse vegetation.
• Darwin also studied the finches that live in the
Galapagos.
• He collected specimens of about fourteen
different types of finches.
• The finches were all similar except for the
structure of their beaks.
• Darwin observed that each finch’s beak was
suited to what the bird ate. He also observed
that finches in different habitats fed on different
things.
Theory of Evolution
• After his voyage, Darwin spent many
years studying the information he had
collected. From his observations of the
tortoises and finches, Darwin developed
two concepts that form the basis of the
theory of evolution.
1. Natural Selection:
• The idea that organisms with favorable
variations for their environment survive,
reproduce, and pass those variations on
the next generations. The concept of
natural selection was based on Darwin’s
observations that many of these variations
helped species survive.
2.Reproductive isolation:
• A species is a group of organisms with similar
characteristics that can breed with one another to
produce fertile offspring.
• The organisms Darwin observed on the various
Galapagos Islands were separated by the ocean.
• . The physical separations led to reproductive isolation,
an inability or organisms to interbreed due to geographic
barriers.
• Reproductive isolation allows different populations of a
species to adapt to different environments.
• Over time, differences in their adaptations can become
significant enough that different species emerge.
Wallace’s Contributions
• Darwin spent many years analyzing his
data and developing his theory. At this
same time, another scientist, Alfred
Wallace, was also formulating a theory of
evolution. Wallace believed that evolution
resulted largely from competition among
populations for resources a concept that
built upon the ideas of Thomas Malthus.
• Darwin and Wallace shared their ideas about
evolution with each other.
• They agreed that natural selection was part of
evolution.
• However, Wallace thought competition was the
driving force behind natural selection, while
Darwin stressed reproductive success.
• Both scientists published papers on their ideas
in 1858.
• Darwin’s book The Origin of Species appeared
the following year.