EvolutionEvolutionEvidence and Evidence and

TheoryTheoryChapter 15Chapter 15

Lab BiologyLab Biology

VocabularyVocabulary

• Absolute age cast• Stratum mold• Fossil extinct• Acquired trait law of superposition• Relative age adapt• Natural selection analogous• Vestigial convergent evolution• Artificial selection divergent evolution• Coevolution homologous• Adaptive radiation fitness

EvolutionEvolution

•A genetic change within a population over time!

FossilsFossils

• Fossil is a trace of a long-dead organism.– Found:

• 1. Sedimentary rock - formed by dust, sand, or mud deposited by wind or water over dead organism

– Usually formed by hard body parts of an organism—shell, bones, teeth, or woody stems

– Hard minerals replace the tissue of the organism leaving rocklike structures

Sedimentary RockSedimentary Rock

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2. mold – imprint in rock in the shape of an organsim

- limestone

3. cast – forms when molds are filled with hard minerals

LimestoneLimestone– Limestone is the most abundant of the non-classic sedimentary rocks.

Limestone is produced from the mineral calcite (calcium carbonate) and sediment. The main source of limestone is the limy ooze formed in the ocean. The calcium carbonate can be precipitated from ocean water or it can be formed from sea creatures that secrete lime such as algae and coral.

– Chalk is another type of limestone that is made up of very small single-

celled organisms. Chalk is usually white or gray in color.

CastCast

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Robert Hooke Robert Hooke 1635-17031635-1703

• He concluded that fossils are remains of plants and animals

• He mostly studied “petrified wood” with the aid of the microscope

• He hypothesized that living organisms had somehow been turned to rock

Petrified WoodPetrified WoodWood that has turned to stone!Wood that has turned to stone!

How is Petrified Wood Formed?How is Petrified Wood Formed?• The mud that covered the logs contained

volcanic ash, a key ingredient in the petrification process. When the volcanic ash began to decompose it released chemicals into the water and mud. As the water seeped into the wood the chemicals from the volcanic ash reacted to the wood and formed into quartz crystals. As the crystals grew over time, the wood became encased in the crystals which, over millions of years, turned the wood into stone.

Distribution of FossilsDistribution of Fossils

• Nicolaus Steno (1638-1686)– “law of superpositon” – states that the top

layers of stratum contain the youngest fossils while the lower ones are older

• This technique helps scientists to determine the “relative age” of a fossil

• “absolute age”- age in years determined by radiological evidence

Succession of FormsSuccession of Forms

• Mass extinctions – brief periods during which large numbers of species disappears.– Some of these life forms were unlike any

organisms alive today– Probably resulted from drastic changes in the

environment, volcanic activity or collisions with asteroids (may have blocked sunlight for long periods of time and decreased temp.)

BiogeographyBiogeography

• Biogeography – is the study of the geographical distribution of fossils and of living organisms.– A comparison of recently formed fossil types

with types of living organisms in the same geographic area shows that new organisms arise in areas where similar forms already lived.

• Ex: armadillos in North & South America where glyptodonts lived in the past.

ArmadillosArmadillos

GlyptodontsGlyptodonts

Scaphognathus crassirostrisScaphognathus crassirostrisLab FossilLab Fossil

Theories of EvolutionTheories of Evolution

• I. Lamarck’s Explanation:– French scientist (1744-1829)– Proposed that similar species descended

from a common ancestor (fossil records)– He hypothesized that acquired traits were

passed on to offspring.

Acquired TraitAcquired Trait

• It’s not determined by genes!

• Instead, it arises during an organism’s lifetime as a result of the organism’s experience or behavior.– Ex: 1. webbed foot on water birds resulted

from repeated stretching of the membrane between the toes

– 2. tails – if you don’t use it you loose it!

Beginning of Modern Evolutionary Beginning of Modern Evolutionary TheoryTheory

• II. Charles Darwin (1809-1882) & Alfred Wallace (1823-1913)– “natural selection”-hypothesis that

organisms best suited to their environment reproduced more successfully than other organisms

– Darwin & Wallace announced their hypotheses at the same time

– Darwin’s name became more associated with evolution The Origin of Species published

DarwinDarwin’’s Voyage on the Beagles Voyage on the Beagle

• Sailed in 1831 for five years

• Collected specimens and kept careful records of his observations

• Sailed to South America (Galapagos Islands) and the South Pacific

DarwinDarwin’’s Findingss Findings

• 1. returned to England in October 1836

• 2. collected 13 similar but separate species of finches.

• 3. Each finch species had a distinctive bill for specialized food source.

• Implied that the finches shared a recent common ancestor

DarwinDarwin’’s Finchess Finches

DarwinDarwin’’s Findingss Findings

A GRUB!!!!!!!A GRUB!!!!!!!

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DarwinDarwin’’s Theoriess Theories

• TWO THEORIES;– 1. DESCENT WITH MODIFICATION – The

newer forms appearing in the fossil record are actually the modified descendants of older species

• Organisms similar to each other come from a recent common ancestor, organisms that are more dissimilar such as finches and armadillos share a more remote ancestor

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• 2. MODIFICATION BY NATURAL SELECTION – states HOW evolution occurs.– Organisms having traits that make them

better suited for survival tend to leave more offspring than organisms with fewer beneficial traits. Darwin called the different degrees of successful reproduction among organisms in a population NATURAL SELECTION

Evidence of EvolutionEvidence of Evolution

• 1. HOMOLOGOUS STRUCTURES: similar features that originated in a shared ancestor– Similar in structure BUT differ in

function!!– Ex: penguin, bat, alligator, & human (all derive

from the same embryological structures)– These examples i.e. share a fairly recent

common ancestor

Homologous StructuresHomologous Structures

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• 2. ANALOGOUS STRUCTURES: Similar functions BUT differ in structure and embryological development– Ex: wings of a hummingbird and humming

moth – both can hover to feed

Analogous StructuresAnalogous Structures

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• 3. Vestigial Structure: Features that were useful to an ancestor, but they are not useful to the modern organism that has them. – Ex: tailbone in humans, appendix, some

snakes have tiny pelvic bones and limb bones, some whales have pelvic bones along with four chambered stomach like a cow!

Vestigial StructuresVestigial Structures

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• 4. Similarities in Embryology

– Ex: all vertebrate embryos are similar, but those similarities fade as development proceeds – evidence that indicates that vertebrates share a common ancestor

Vertebrate EmbryosVertebrate Embryos

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• 5. Similarities in Macromolecules: The more similar homologous proteins are in different species, the more closely related the species are thought to be.– Ex: the amino acid sequence in human

hemoglobin and gorilla hemoglobin differ by ONE amino acid

– While the Hb of humans and frogs differ by 67 amino acids!!

Patterns of EvolutionPatterns of Evolution

• 1. Coevolution: the change of two or more species in close association with each other is called coevolution– Predators and their prey sometimes co-evolve

• Ex: “tropical region” bats feed on nectar– Bats have slender muzzle and long tongue that help

them to feed,flowers are light in color which helps bats to see them at night and have a fruity odor that is attractive to the bats.

Tropical Bats!Tropical Bats!

Baby Bats!!Baby Bats!!

CLOSE UP!!!!CLOSE UP!!!!

• COOL!

Flowers with Nectar!Flowers with Nectar!

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• 2. Convergent Evolution: occurs when the environment selects similar phenotypes, even though the ancestral types were quite different from each other.– Analogous structures, such as similiar fins in

very different animals, are associated with convergent evolution

• Ex: sharks and porpoises

PorpoisesPorpoises

SharksSharks

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• 3. Divergent Evolution: two or more related populations or species become more and more dissimilar. Divergence is nearly always a response to differing habitats and can result in new species– A) adaptive radiation: many related species

evolve from a single ancestral species ex: Galapagos finches

– B) artificial selection: all domestic dogs are the same species “Canis familiaris”

Canis familiarisCanis familiaris

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