• The Earth’s age is estimated at about 4.6 billion years old

• Early History of Earth (atmosphere):–Was very hot, bombarded by meteorites

–Volcanic action with lava gases, water vapor, carbon dioxide and nitrogen

3.9 billion years Earth began to cool and first organisms appeared

Fossils–99 percent of all species are extinct

–Fossils give evidence of organisms existence

–Most fossils are found in sedimentary rock and often destroyed ducts change in the earth’s crust

Types of fossils

–Trace – markings left behind

–Casts – minerals fill in space left by organism

–Petrified – minerals penetrate and replace organism

• Molds – empty space left in sedimentary rock

• Imprints – impression left in sedimentary rock

• Amber – preserves organisms intact

Age of Fossil • Hutton and Lyelle helped scientists recognize that Earth is millions of years old and that the processes that changes Earth in the past are the same processes that operate in the present

Relative dating – geologic law says oldest organism are on the bottom layer

Age of FossilsRadiometric dating – radioactive

isotopes break down into new substances–Half-life – decay rate of radioactive isotopes

– Ex: Potassium – 40 Argon – 40 1.3 million years

– Ex: Carbon – 14 Nitrogen – 40 5730 years

PRECAMBRIAN

Origin: the Early Ideas

• Spontaneous Generation (abiogenesis) – the idea that nonliving material can produce life

Experiments:• Fransico Redi –

controlled experiments that tested the spontaneous generation of maggots from decaying meat

• Spallanzani – showed that microorganisms would not grow in boiled and sealed gravy (similar to Redi – still did not receive credit)

RediSpallanzani

•Many scientists still thought that microorganisms were so numerous and widespread that they must still arise spontaneously from a vital force in air

Spontaneous Generation disproved

• Louis Pasteur – showed that microorganisms do not simply arise in broth, even in the presence of vital force

• Biogenesis – the idea that living organisms come from only other living organisms – now the cornerstone of biology

Origin: Modern Ideas

• Simple Organic Molecules Formed:–Alexander Oparin

(Russian) – hypothesized that life formed on early earth.

• Primordial soup – The sun’s energy, lighting, and heat triggered chemical reactions to produce small organic molecules (ex: amino acids) from substances present in the atmosphere; rain molecules into the oceans

• Miller and Urey (Americans) supported Oparin’s hypothesis by simulating the conditions of early earth (primitive earth)

Formation of Protocells

• Sidney Fox showed how the first cells might have occurred as protocells (large, ordered structures enclosed by a membrane that could carry out some life activities) ex: growth, division

Formation of True cells–Thought to have been

mostly prokaryotes (w/o nucleus), anaerobic (w/o oxygen) and were heterotrophs (obtained food rather than making their own food)

• The first autotrophs (The first autotrophs (make their own make their own foodfood) are thought to have evolved ) are thought to have evolved later and were probably similar to later and were probably similar to ArchaebacteriaArchaebacteria that live in that live in harsh harsh environmentsenvironments and make own food and make own food buy buy chemosynthesischemosynthesis rather than rather than photosynthesisphotosynthesis

• Endosymbiont Theory – was proposed by Lynn Margulis; she proposed that eukaryotes evolved through a mutualistic relationship between ancient prokaryotes

• Evidence: mitochondria & chloroplast contain structures similar to prokaryotes & unlike DNA in eukaryotic nuclei; they also have ribosomes & reproduce independently of cells they are in.

Endosymbiont Theory

• Ideas of Evolution Ideas of Evolution – first published by – first published by Charles DarwinCharles Darwin and and now the basis of now the basis of the the Modern Modern Evolution TheoryEvolution Theory..

• HMS Beagle an HMS Beagle an English Ship – at the English Ship – at the age of 21age of 21 Darwin Darwin took a job as a took a job as a naturalistnaturalist..

• It was a It was a 5 year5 year journey where journey where collected collected biologicalbiological specimens at every specimens at every portport

• Galapagos Islands a group of small islands that was of great interest to Darwin.

• He made observations of many species of animals and plants that lead to the possibility that species can change over time

• Next 22 yrs – Darwin worked to find an explanation for how species could change over time. He modified the ideas of Thomas Mathus (who was studying how human population was growing faster than Earth’s food supply).

Darwin & 2Types of Selection:

• Artificial Selection: nature provides the variation but humans select those variations that they found useful

• Natural Selection: when organisms with certain variations survive, reproduce, and pass variations to the next generation “Survival of the Fittest.”

3 Types of Natural Selection

• Stabilizing: favors average individuals in a population;

• ex: spiders with average size are more likely to survive

• Directional: favors one of the extreme variations of a trait; ex: woodpeckers with long becks feed on insect under bark

• Disruptive: favors individuals with both extremes of trait ex: light colored and dark colored limpets blend in with light and dark rock

2 Types of Adaptation:

• Structural Adaptations: Arise over time

• ex: teeth, claws, thorns–Mimicry – enables one species to

resemble another–Camouflage – enables species to

blend with their surrounding

• The viceroy (right) and monarch butterflies look very similar but monarch is poisonous to predators

“Batesian Mimicry”

• Physiological Adaptations: can develop rapidly; changes metabolic processes (DNA) ex: Bacterial Resistance to Penicillin – DIRECT EXAMPLE

• Fossils – provide a Fossils – provide a record record of of early lifeearly life and and evolutionary historyevolutionary history

Evidence for EvolutionEvidence for Evolution

Anatomy – structural adaptations

• Homologous Structures: similarities in arrangement (look alike, different functions)

• ex: forelimbs of animals

• Analogous Structures: similarities in function (look different; same function)

• ex: wings of butterfly and bird

• Vestigial Structures: body structures that have no function in present-day organism; probably used by ancestors.

• ex: appendix, snakes with legs

• Embryology – similarities in the earliest stages of growth and development

• ex: in birds, mammals, fish, reptiles it is difficult to distinguish embryos

•Biochemistry – comparison of the DNA, amino acids sequences.

Summary: Evidence for Evolution

1. Fossils2. Anatomy

3. Embryology4. Biochemistry

*All evidence only shows common ancestry

Mechanisms of Evolution

• Populations – consists of all the members of a species that live in that area;

• evolution occurs as a population’s genes change over time not individuals

• Gene Pool – all the genes in a population

• Allelic Frequency – percentage of any specific allele in a gene pool (Hardy Weinberg Principle = p2+2pq+q2=1)

Genetic Equilibrium – population’s genes remains the same (not

evolving)

Changes in Genetic Equilibrium:

1. Natural Selection: Survival of the Fittest – due to variations

2. Mutation: changes in DNA sequence; many are lethal

3. Genetic Drift: alterations of alleles by chance events; usually in small isolated populations ex: Amish

4. Gene flow: movement of individuals in and out of a population

Evolution of a species?? How??• Species – organism that look alike; can

interbreed to produce fertile offspring• Speciation – evolution of new species;

occurs when members of similar population no longer interbreed to produce fertile offspring

Causes of speciation

• Geographic Isolation (allopatry) – when two populations are separated by geographic barriers

• ex: river, mountains

• Behavioral Isolation – when two populations are capable of interbreeding but have differences in courtship rituals

• Temporal (Reproductive) Isolation - when species reproduce at different times ex: orchids pollination on different days

• Polyploidy – multiple sets of chromosomes

Patterns of Evolution

• Divergent Evolution – where species that were once similar become different

Adaptive Radiation - divergent evolution that occurs when a species evolves into an array of species to fit diverse habitats

ex: Galapagos finches

Convergent Evolution – when distantly related organisms evolve similar traits due to similar habitats

ex: dolphin and shark

Patterns of Evolution

divergent convergent

Summary: Patterns of Evolution

• In 1871, Charles Darwin proposed in his book “The Decent of Man” that there might be an evolutionary link among monkeys, apes, and humans.

What is a primate?

• A group of mammals that include lemurs, monkeys, apes, & humans

1. Opposable thumbs

2. Large brain

3. Binocular vision

4. Flexible joints

5. Adapted feet

6. arboreal

7. Round head, flat face

8. nails, claws

PRIMATE ORIGIN

• Scientists use fossil evidence, anatomy, embryology and genetics to propose ideas about how modern primates evolved

2 MAJOR PRIMATE GROUPS

• Prosimians – lemurs, ayes-ayes, tarsiers

• Anthropoids – human like primates, includes monkeys & hominoids

PrimatesProsimians•Live in tress•Mostly active at night•No larger than a house cat•Eat insects, seeds, fruits

Anthropoids•Large brain•Complex skeleton

New World Monkeys•Central & South America•Live in trees-arboreal•Can grab things with their tails (prehensile tail)

Old World monkeys•Africa & Asia•Live in trees or on ground•Some live in cold regions•Use tails for balance

Hominoids•Do not have tail•Use simple tools•Humans have largest brain capacity•Classified as apes or humans

Human Ancestry

• Hominids are primates that can walk upright (bipedalism) & include gorillas, chimpanzees, & humans

• Scientists propose that between 5 and 8 million years ago in Africa that hominids diverged into 2 lines:

1. African Apes – gorillas and chimpanzees

2. Modern Humans-Evolution of Homo Sapiens

Australopithecus afarensis (1924)

Lucy

4 mya

Australopithecus africanus (1974)

3 mya

Skills• Australopithecines climbed trees• They could also walk upright on the

ground• They have a foramen magnum opening in

the skull through which the spinal cord passes

• Possessed ape-like & human-like traits

Homo Habilis (1964)Leaky1.5-2 mya

Homo erectus

1.6 mya

Skills

• Homo habilis used simple tools• “Handy Man”• Homo Erectus used large tools• “Upright Man”; more human like

Archaic Homo Sapiens

Neanderthal

3500-100,000 yrs ago

Homo sapien

100,000 yrs ago

Cro-Magnon

33-40,000 yrs ago

Skills

• Neanderthals seem to have hatchet, culture, and spoken language

• Cro-Magnons were talented artists & tool makers

• Homo sapiens build cities and used technology

• Brain volume of 1,000 to 1,4000 cm3