Diversity and

EvolutionSC.912.L.151

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Origins of Life on Earth

Original Conditions on Primitive Earth to make life….

• Presence of liquid water• Moderate temperature range• Free oxygen in the atmosphere• Adequate sunlight• Absence of toxic substances in

atmosphere• Absence of lethal radiation

Volcanoes Play a BIG Role• Water vapor (eventually condensed and fell as RAIN)• Methane• Hydrogen • Nitrogen• Ammonia• Carbon Dioxide (we now have oxygen b/c of

photosynthetic bacteria) • Carbon Monoxide

• Evolution is studied using concepts about earth history. The earth is between 4.3 and 4.5 billion years old.

• Approximately 3.9 billion years ago, the surface was likely cool enough for water vapor to condense and form oceans

• Geological evidence suggests that cells similar to modern bacteria were common 3.8 billion years ago.

Earth History

Until the 1700’s people believed that living things could come from nonliving substances, spontaneous generation.

How did life on Earth begin?

Spontaneous generation: Pasteur’s experiment

• Experiment: Pasteur filled a flask with broth with a long S shaped neck. He boiled it to kill all life. It was open and exposed to air, but anything in the air got stuck on the curves of the neck.

• Conclusion: Spontaneous generation was disproved and biogenesis theory was substantiated. Contamination came from other microorganisms, not “air”.

QUESTIONS• What was the hypothesis? What was the experimental group? The

control group? The constants? The variable?

“Primordial Soup Theory”• Conditions on the early Earth were

very different.

• The atmosphere had no oxygen • Energy sources, such as lightning, volcanic activity, and ultraviolet

sunlight (no ozone layer)

Theory of Chemical Evolution

• Earth’s early atmosphere: HCN, CO2, CO, N, H, S, H2O• “Life arose from the oceans”• He believed that energy from lightning and the sun can

spark chemical reactions to create AMINO ACIDS that made proteins.

Chemical Evolution

Urey and Miller

• created in the laboratory, the conditions of early Earth.

• They discharged sparks in an “atmosphere” of the Miller-Urey model consisted of H2O, H2, CH4, and NH3 gases.

• produced a variety of amino acids and other organic molecules.

Chemical Evolution

Chemical Evolution• Alternate sites proposed for the synthesis of organic

molecules include • submerged volcanoes and deep-sea vents where

hot water and minerals gush into the deep ocean.

• Prokaryotes were the earliest organisms on Earth and evolved alone for 1.5 billion years.

• two prokaryotic domains: Bacteria and Archaea

Prokaryotes

• have a cell wall external to the cell membrane

• Lack membrane bound nuclues and organelles

• Double-stranded DNA molecule is in a single ring shaped

Prokaryotes

OXYGEN ATMOSPHERE• Remember the atmosphere

of early Earth was made up of nitrogen, carbon dioxide, water vapor, but no free oxygen

• Oxygen comes from photosynthesis when leaving oxygen gas.

• About 2 billion years ago, the oxygen level in the atmosphere started to rise.

• Aerobic metabolism, much more efficient than anaerobic, became possible.

QuestionWhat are the reactants in

photosynthesis?The products?

The evidence of oxygen gas formation can be seen in rocks when layers of iron oxide on the bottoms of oceans stopped forming when oxygen appeared.

Cyanobacteria created the oxygen in the atmosphere.

Evolution• Process by which species of organisms

change over time• Thing evolve around us all the time• Based on scientific evidence such as…

– Fossils– Comparative morphology/anatomy of organisms– Embryology– Analysis of genetic material (DNA analysis…DNA

fingerprinting!)

Terms to Know• Species

– a group of organisms that share similar characteristics and can interbreed to produce fertile offspring

– As species EVOLVE, they produce new traits and lose other traits….

• Adaptation– Any physical or behavioral trait

that improves an organisms chance for survival and reproduction

Fossil Evidence for Evolution• Fossils:

– Remains or evidence of organisms that have lived in the past

– Provided clues of when different species lived

• Law of Superposition– States that in undisturbed sedimentary rock,

older rock layers lie beneath younger rock layers

– By Identifying the fossils indifferent layers of rock and applying the law of superposition, scientists can determine:

• when the certain organisms lived• The order in which things evolved

Law of Superposition

Biogeography

• Study of the distribution of Earth’s organisms

• Continental Drift Hypothesis– States that the continents were

once joined in a single, large landmass called PANGAEA

– Pangaea broke up over millions of years and continents ended up where they are today

– Fossil evidence shows that in addition to changing Earth’s surface, continental drift also changed the distribution of organisms on Earth

Comparative Anatomy/Morphology

• Do other organisms have arms like us?

• Many species share similar structures..

• Do flamingos and blue jays have feathers?– Yes…the presence of feathers suggest

that both groups of birds descended from an animal with feathers

– Flamingos and blue jays are more closely related than either one is to an animal without feathers (like us)

Homologous Structures

• Body parts of different organisms that have similar structure but NOT similar FUNCTION

• Homologous structures DO indicate shared ancestor

Analogous Structures• Body parts that have a SIMIALR FUNCTION but NOT

similar structure• Body parts with Different structure, same function• Do NOT indicate shared ancestry • An analogous structure found in two different species

Homologous vs. Analogous Structures

• Homologous= Same structure, DIFFERENT Function

• Analogous= Different Structure, SAME Function

Anatomical features that are similar in structure are called homologous structures, and they

indicate common ancestry.

Comparative Anatomy

Vestigial Structures

• Structures that do not seem to play a role in the body functions of the organism– Appendix

• Rats digestion• Humans no use…appendix is a

vestigial structure• It can be concluded that the common

ancestor of the human and rat had an appendix

Embryology

• Study of embryos• Embryo early stage in the

development of an organism• Scientists compare the

development of the embryos of different species

• Similarities in development =shared ancestor

• More traits in common=more closely related

Modern Organisms

EVOLVED from COMMON

Ancestors in an Evolutionary

Chain

Chemical Evidence of Evolution• Chemicals found in living things

also provide clues to ancestry..what chemical?– DNA!!!

• Comparisons of the sequences of the nucleotides in DNA and the amino acids in certain proteins can also be used to show more common ancestry

• More similarities in two DNA sequences or amino acid sequences = the more closely related the organisms are – DNA fingerprinting

ALL organisms have DNA made up of the same Amino Acids…

The only thing that’s different is the ARRANGEMENT/sequence of amino acids…

The More similar AA sequences= themore closely related the organisms are!

Similarities in Molecular Biology

Common amino acid sequences suggest an evolutionary relationships between

various species of organisms.

Observed Evolutionary Change• Speciation

– Evolution of a new species from an existing species

• Occurs when a population is separated into groups that cannot reach each other to interbreed

• Once groups are separated, environmental conditions in each area influence which traits are helpful or harmful to members of each population– Less helpful traits disappear– Helpful traits become more popular

• Overtime, these changes can produce 2 distinct species that can no longer interbreed

Two Ways Evolution is believed to have Occurred

• Gradualism– Evolution occurring over a long period of

time– Slow and constant change– Small difference between generations– This is how Darwin believed NATURAL

SELECTION worked

• Punctuated Equilibrium– Evolution occurs in spurts – Changes occur rapidly followed by long

period without change– Causes:

• random mutations in DNA• Sudden Major changes in environment

Microevolution

• When evolution occurs quickly enough for scientists to observe

• Bacteria – Reproduce rapidly– Trait for Resistance to antibiotics is

passed down to offspring– This is how bacteria become

resistant to certain medicines…NOT GOOD

• organisms that descended from different ancestors

• Evolve similar anatomies and/ or behaviors if they live in similar environments

Convergent evolution

Divergent Evolution

• Organisms from the same ancestor have developed different anatomies/behaviors (and eventually form new species)

• Environment influences their new anatomy/behaviors

Darwin’s Theory of Evolution by Natural Selection

– Before Darwin people believed Earth was less than 10,000 years old and also relatively unchanged

• Buffon- Studied the fossil record which showed that the Earth might be much older.(4.3 and 4.5 billion years old)

• Hutton - Layers of rock are moved by forces beneath Earth’s surface. Most geological processes operate extremely slowly.

• Lyell - geologic process that shaped the Earth in the past still continue today.

Ideas that shaped Darwin

Before Darwin people believed that species were fixed, plants and animals had always been the way they are today

Cuvier – based fossils from different rock layers gave evidence that organisms from the past differed greatly from living species,

Ideas that shaped Darwin

•Lamarch’s Use or disuse1st to suggest that species change evolve or evolve over time. But his explanation was flawed.

He thought characteristics acquired through your life could be passeddown from parent to offspring.

Ideas that shaped Darwin

• Malthus – suggested that if the human population continued to grow unchecked, eventually there wouldn’t be enough food and living space for everyone.

• As Malthus predicted, world population growth is exponential:

• 1 billion in 1830 • 2 billion in 1930 • 3 billion in 1960 • 4 billion in 1974 • 5 billion in 1987 • 6 billion in 1999 • 7 billion in 2013 • 8 billion in 2028 • 9 billion in 2048

• Darwin made a voyage around the word collecting thousands of plant and animal specimens.

• His observations and collected evidence led him to propose hypothesis that living things change over time

• Theory of Evolution through natural selection.

Voyage of the Beagle

• Darwin noticed that plants and animals on the Galapagos islands of the coast of Ecuador were different from those on the mainland and also from island to island

• .

Voyage of the Beagle

Neck-size vs. Vegetation height

Galapagos’ Finches

Galapagos’ Finches

• In 1859, Darwin published a book titled,• “On the Origin of Species”

• In this book he presented all the evidence he had gathered over the past several years supporting his theory that evolution has been taking place for millions of years—and continues in all living things.

Darwin’s Theory

• In his book he also proposed a mechanism for evolution called

• Natural Selection

• DNA is the blue-print for building ALL living things on planet Earth.

• DNA sequences are changed by:• random mutations• Radiation• Viruses• Chemicals• sexual reproduction• Migration• geological events

• As a result there is variation within populations of a species.

• Those individuals of a particular species with a phenotype (as a result of their genotype) that is more fit to survive in a given environment has a better chance to reproduce.

• Those individuals who reproduce more pass-on their genes at a higher frequency than those who do not.

Summary of Evolution

The ability of an organism to survive and

reproduce in its specific environment is called

fitness.

• Individuals with characteristics that are not

well suited to their environment either die or

leave few offspring

• Individuals that are better suited to their

environment survive and reproduce most

successfully.

• Darwin called this process Survival of the

Fittest, or Natural Selection.

NATURAL SELECTION

4 Principles of Natural Selection

• Variation• Competition• Excess offspring• Survival of the Fittest

4 Main Principles of Natural Selection

1. Variation exists within a population

2. Organisms compete for limited resources

3. Organisms produce more offspring than can actually survive

4. Individuals with variations suitable for their habitat are the ones that SURVIVE and REPRODUCE

• Three species of lizard. • B- The ones at the bottom live in the shrubland, and

are colored to blend in. •The top pictures show the

same species of lizard, but the variety that lives in the White Sands•They all evolved to become white (camouflage)

•The DNA on the bottom shows the location of the mutation that gives the white color

Individual organisms within the population differ. Most of this variation is determined by genetic inheritance (recombination), but sometimes it is the result of genetic mutations.

1. Inherited Variation

2. Struggle for Existence Because so many offspring are produced, many will die due to a lack of resources, predation, disease, or other unfavorable conditions.

3. Overproduction of Offspring

Organisms produce more offspring than can survive. Many of the offspring do not survive to reproductive age.

4. Differential ReproductionIndividuals best suited to their environment survive and reproduce most successfully. Therefore these organisms pass their advantageous traits to their offspring while offspring with disadvantageous traits die or produce fewer offspring.

Descent with Modification• Natural selection

causes species to change over time.

• Species alive today descended with modification from ancestral species.

• Genetic Drift• Sometime changes in the allele frequency

within a population occur by chance. This is called genetic drift.

• The genes of the next generation will be the genes of the “lucky” individuals, not necessarily the healthier or “better adapted” individuals.

Evolution of populations

Before After

Gene Flow• the process of genes moving

from one population to another. For example: The immigration and emigration of organisms. The dispersal of seeds or spores.