HONORS BIOLOGY Chapters 17, 20 & 21

Emergence of Evolutionary Thought and

the Origin and Evolution

of Life

Important Dates13700 MYA THE BIG BANG (UNIVERSE IS BORN)12000 MYA THE FORMATION OF THE MILKY WAY GALAXY 4600 MYA THE FORMATION OF OUR SOLAR SYSTEM AND THE EARTH3500 MYA FIRST FOSSIL EVIDENCE OF LIFE ON EARTH (STROMATOLITES,

EARLY PROKARYOTES2100 MYA FIRST FOSSIL EVIDENCE OF EUKARYOTIC CELLS1500 MYA EARLIEST MULTICELLULAR EUKARYOTES 535-525 MYA CAMBRIAN EXPLOSION

CNIDARIA (SEA ANEMONES AND THEIR RELATIVES)PORIFERA (SPONGES)MOLLUSCA (SHELLFISH)

500 MYA THE COLONIZATION OF THE LAND (FUNGI, PLANTS AND ANIMALS)420 MYA SMALL PLANTS WITH A VASCULAR SYSTEM (LACKED TRUE ROOTS OR

LEAVES)365 MYA TETRAPODS (EVOLVED FROM LOPE-FINNED FISHES) AND INSECTS6-7 MYA HUMAN LINEAGE DIVERGED FROM OTHER HOMINOIDS (APES) 

*** IF THE CLOCK OF EARH’S HISTORY WERE RESCALED TO REPRESENT AN HOUR, HUMANS APPEARED LESS THAN

0.2 SECONDS AGO. 

Early thoughts on biological diversity………..

• Aristotle - believed nature to be a continuum of organization….a GREAT CHAIN OF BEING……extending from the lowest forms of life to humans and then to the spiritual world. Each kind of organism was a “species”.

• “Each being (species) had a fixed place in the divine order; unchanged & unchanging since creation.”

• It was believed that all organisms were formed at the same time and had not changed since.

• Once all organisms were identified, the meaning of life would be revealed!!

Biogeography …………...

• The study of the distribution of plants and animals worldwide and the types of climates and geographic barriers that affect gene flow.

• Global voyages (16th century) led to many questions of when new species fit into the “Great Chain of Being.”

• Why are certain species found in only some parts of the world, but not others? How did certain species get from the Center of Creation to islands & isolated places?

• Biologists began to wonder if there is a relationship between life forms and the geography of the land.

The Theory of ………………….. Spontaneous Generation

• Before the microscope, it was commonly believed that life arose from non-living materials!

• Flies came from rotting meat.

• Bacteria came from rotting broth.

• Frogs came from rain & mud.

• Mice came from grain & rags.

• Francesco Redi - disproved the idea that flies came from rotting meat.

• Louis Pasteur disproved the idea that bacteria spontaneously arose from broth.

• BIOGENESIS- Life must arise only from living organisms.

Pasteur’s Experiment

If life comes from life…. where or how did the first life

form arise?

• Simple organic molecules and the organization of these molecules into more complex substances would have occurred.

• Early Earth’s atmosphere did not contain free oxygen. (water vapor, hydrogen, methane, and ammonia)

• Life would have to occur under very difficult conditions- different from today!

Alexander Oparin’s Theory

• As the earth cooled, life began in the oceans as organic molecules slowly assembled.

• Energy from sun and lightning could have triggered chemical reactions to produce simple organic compounds, creating a primordial soup.

Complex Organic Compounds

• 1953 - Miller and Urey set up experiment simulating conditions of early Earth

• Their experiment produced amino acids, sugars, and other organic compounds.

• Similar processes have produced ATP (energy carrier) and nucleotides (building blocks of DNA).

• MILLER - UREY

EXPERIMENT

• CH4, NH3, and H2 represented the primitive atmosphere. Along with water vapor and electrical charges- organic molecules were produced...

The Evolution of Cells• Must be able to survive in harshest of climates

(sulfur springs, extreme heat, little light or oxygen).

• First organisms were:– prokaryotic– anaerobic– heterotrophic

• Similar to oldest organisms - Archaebacteria

• Evolved into autotrophs; photosynthetic (oxygen)

• Presence of oxygen also created ozone.

Early Evolutionary Theories….

• Georges Cuvier:– (Anatomist) compared the body plans of fossils and living

organisms.

– noted abrupt changes in the fossil record that corresponded to changes in the sedimentary layers of the earth.

– Theory of Catastrophism:• all life was created at the same time• a series of global catastrophes occurred• proposed that today’s species are descendants of the

survivors of those catastrophes.

The Theory of Acquired Characteristics

• Jean-Baptiste de Lamarck :– stated that environmental pressures and internal desires

brought about permanent changes in an organism.

– internal force to change is a drive for perfection up the Chain of Being.

– fluida: substance in the nerves– EXAMPLE: Giraffe’s neck slowly became

longer.• environmental changes

• fluida within the animal, so its offspring are born with longer necks.

The Theory of Evolution of Life• Charles Darwin -A Naturalist who, in 1831, traveled

on the “HMS Beagle” for a five year expedition to collect, study, and store biological specimens discovered.

• Principles of Geology by Charles Lyell -stated the Theory of Uniformity (geological changes happen at a uniform gradual rate over time, making the Earth very old; millions not thousands of years old.)

• Thomas Malthus -A study of over-population; ‘survival of the fittest’; not all competing members survive.

The Galapagos IslandsThe Galapagos Islands• Darwin observed many

islands with great biodiversity.

• Animals and plants were best suited for their own particular climate and food source.

• He noticed that the organisms on the Galapagos Islands were similar to those on the mainland but seemed to have adapted in different ways in order to survive each island’s unique climate and food sources.

• Reasoned: ‘a population is evolving when its heritable traits are changing through successive generations’.

The Galapagos IslandsThe Galapagos Islands

Was it possible…

..that these two

organisms were related?

If so, how & why did one change into the other?

Darwin’s Finches

Darwin Finches:

• Why are the Galapagos finches different from the same species of mainland finches?

• What caused the changes?

Darwin’s Theory of……………….Darwin’s Theory of………………. Natural Selection Natural Selection• 1. Organisms produce

more offspring than can survive. (limited food)

• 2. Variations exist within populations

• 3. Some variations are more advantageous than others (struggle for existence)

• 4. The “fittest” survive and reproduce! Thus the species modifies itself over time. (Natural Selection)

Artificial Selection vs. Natural Selection

• Artificial Selection - By breeding organisms that had desirable traits, their offspring would inherit these same traits. This process is controlled by man.

• Natural Selection - Nature selects or chooses which traits in an organism will be passed on to future generations. Beneficial adaptations are passed on, harmful adaptations are eliminated.

AdaptationsAdaptation: an anatomical, physiological, or behavioral trait that improves an organism’s ability to survive and reproduce.

Adaptations• Populations adapt as the

environment changes– 1) Mimicry…..A structural

adaptation that provides protection by enabling an organism to copy another species. (Monarch and Viceroy)

– 2) Camouflage….. A structural adaptation that enables the organism to blend in with its environment.

– (Kettlewell’s Peppered Moths)– 3) Physiological Adaptations….

Bacteria that have developed a resistance to antibiotics.

monarch

viceroy

Five Points of Evidence for Evolution• 1. Fossils: Evidence of Ancient

Life – Fossilization is a slow process (what

does it take to make a fossil?)– Stratification

• Layering of sedimentary deposits

• The older the layer, the older the fossils and they are similar on each continent.

– Geologic Time Scale• Based on sequences of fossils in

sedimentary rocks (bases of Geologic Time Scale)

Fig. 20.4, p. 314

1

1

1

23

3

3

4

4

5

STEM REPTILE

PTEROSAUR

CHICKEN

BAT

PORPOISE

PENGUIN

HUMAN

•2.Comparative Morphology: a comparison of body forms and structure.

a) Morphological divergence (Homologous structures – Body parts with similar structure but different functions. Ex: arm of human & forelimb of bat.)

Five Points of Evidence for Evolution

b) Morphological convergence (Analogous structures - Body parts similar in function but different in structure. Ex: wings of birds and butterflies.

Comparing Convergent andDivergent Evolution

Fig. 20.5, p. 315

jawless fishes

land-dwelling stem reptiles

class Chondrichthyes (cartilaginous fishes)

class Reptilia (reptiles) class

Aves (birds)

class Mammalia (mammals)

shark

penguin

porpoise

pectoral fin

flipper (derived from a wing)

flipper (derived from a foreleg)

These parts all function similarly, but probably developed because of common environmental pressures. Natural selection probably

caused similar modifications.

Vestigial Features

3. Vestigial Organs - Structures that have no

function in the organism today but may have been

useful at one time. Example: appendix

pelvic girdle (hind

legs attach to these)

coccyx (bones

where many

other mammals

have a tail)

small bone

attached to

pelvic girdle

thighbone

attached to

pelvic girdle

Similarities in Embryology

4. Comparative Embryology – early vertebrate embryos strongly resemble one another. – WHY? – They inherited the same ancient plan for development.– Then, how did adults of different groups get to be so

different?• Heritable changes in the onset, rate or time of completion of

developmental steps which could increase or decrease relative size of tissue or organs.

Five Points of Evidence for Evolution

Fig. 20.7, p. 317

FISH REPTILEBIRD (chicken)

MAMMAL (human)

adult shark Early human embryo (three millimeters in length)

Changes in timing of developmental steps

• Britten and Reynolds hypothesized that transposons brought about variation among lineages.– Transposons: DNA segments

move spontaneously from 1 location to another on the same or different chromosome.

– They often deactivate genes– Can cause interesting traits

Which one of the infant skulls is an ape?

Five Points of Evidence for Evolution

• 5. Evidence from Comparative Biochemistry (Genetic Similarities) - DNA and RNA sequences are similar in related organisms.– Molecular clocks: neutral mutations (no affect on survival &

reproduction rates; can be used to date times of divergence of species.

– Protein comparisons • amino acid sequence in DNA• Cytochrome C (used to place humans, chimps, rhesus monkeys)

– Nucleic Acid comparisons (base-pairing of DNA/RNA from one species to another)

3 Versions of Cytochrome C (a major component of electron transport systems in cells)

• The 3 amino sequences about are; yeast, wheat and a primate.

•What do the colors indicate?

•GOLD = SEQUENCES OF AMINO ACIDS THAT ARE IDENTICAL IN ALL 3 SPECIES.

RACCOONRED PANDA GIANT PANDA

DIVERGENCE approximately

40 million years ago

DIVERGENCE 15-20 million years ago

SPECTACLED BEAR

SLOTH BEAR

SUN BEAR

BLACK BEAR

POLAR BEAR

BROWN BEAR

DNA-DNA Hybridization Studies• comparing 2 stands of DNA from 2 different species

• measuring heat of separation (more heat, related)

What about the “missing links”?

If each species evolved from others, where were the fossils of the transitional species?

In 1860, the fossilized skeleton of Archaeopteryx was found in Germany. It was the first of many transitional fossils to be found, demonstrating how one species had lead to another.

Dromaeosaurus Archaeopteryx

Mechanisms of Evolution

• Evolution occurs when there is a change in the genetic makeup of a population.

• Evolution occurs in a population over many generations, and thus is a very slow process.

• Gene pool - all the genes in a population• Allele frequency - Proportion of each allele

in a gene pool (SS,Ss, Ss, ss - 3:1 spotted to black)

Changes in Genetic Equilibrium

• Genetic equilibrium - Allele frequencies do not change over time (non–evolving)

1) Mutations - Cause genetic changes in gene pool.

2) Genetic Drift - Changes due to chance events (Small populations)

3) Gene flow - Movement of genes into or out of a population

Speciation• The formation of a new species from an ancestral form (species

only mate with each other).

• This can only occur when inter-breeding or the production of fertile offspring is somehow prevented.

• Physical barriers - new mountain ranges, canyons, or water barriers can create geographical isolation.

• Reproductive Isolation -either by mutations that prevent offspring development, or seasonal mating changes that prevent mating.

• Speciation can occur quickly or slowly.

• Gradualism- Species originate through a gradual accumulation of adaptations.

• Punctuated Equilibrium - Occurs in rapid bursts with long periods of stability in between.

• Adaptive Radiation - An ancestral species evolves into many different species( Divergent Evolution)

• Convergent Evolution -Distantly related organisms evolve similar traits. Ex. whales and fish……………………………………..el fin !