EVOLUTION CONTINUED“Where’s the Evidence?!”

Chap. 13 The Macroevolutionary Puzzle

VocabularyRead

(282-292)(740)(327)

• 109 paleontologist• vestigial structure• homologous structure• gradualism• punctuated equilibrium• continental drift• analogous character• isotope• 117 radioisotope

Radiometric Dating or Radioactive Dating

• Isotope- 1 form that an element can have. Number of neutrons is variable between isotopes of the same element. (number of electrons and protons stays the same)

• Minerals possess radioactive isotopes (give off energy and subatomic particles) that decay (breakdown) into smaller isotopes.

• Formed in igneous rock, the minerals grow as the liquid rock cools.

• Amounts of the “parent” (or original) and “daughter” isotopes can be measured in a sample collected today.

• The rate of decay can be calculated experimentally.

• “Half Life” is a common unit of measure of the rate of break down.

p

p

p

Atomic mass not changedmuch; atomic numberincreases by 1 becauseNeutron becomes proton

(b) Beta decayBeta particle

Radioactiveparent nucleus

Decay process Daughternucleus

Atomic mass not changed much;atomic numberdecreases by 1

(c) Electron captureBeta particle

Atomic mass decreasesby 4; atomic numberdecreases by 2

(a) Alpha decay

Alpha particle

ProtonNeutron

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Emission of 2 protons and 2 neutrons (alpha particle)

An electron (beta particle) is ejected from the nucleus

electron combines with a proton to form a neutron

Sample Problems

• The half-life of Potassium 40 is 1.3 million years. It breaks down into Argon 40

• 1) If an original rock sample contains 200 micrograms of Potassium 40, how much would remain after two half-lives?

Uranium 238 has a half-life of 4.51 billion years and decays into Lead 206

• 2) A newly discovered rock sample has 15 micrograms of Uranium 238 and 105 micrograms of the daughter material Lead 206. How old is this rock?

Homework 2 sides in binder

• The next 2 slides are more practice problems to work on later.

– U238 decays into Pb206 in 4.51 billion years (HALF LIFE)

– How much U238 and Pb206 are present in a sample after 2 HALF LIVES?

– (original sample is 300 grams)

– U238 75 grams Pb206 225 grams

– How long would 2 half lives be?

– 9.02 billion years

– How old is an igneous rock sample containing 275g U238 and 1925g Pb206?

– 3 x 4.51 = 13.53 billion years

V. EVIDENCE OF EVOLUTION FROM FOSSILS

“any evidence of once living creatures”

Where are fossils most likely to be found?

A. 4 Types of Fossils• 1. Compression- organic material

between layers of sediment, Some details can be observed . ex. fern frond, fish

• 2. Impression- external shape and form, no organic matter ex. foot print, limb print

• 3. Mold and cast- external features in one layer, then the item itself is replaced by other sediments ex. Egg, shark tooth

• 4. Petrifaction- tissues are gradually infiltrated by minerals. No organic material remains ex. petrified wood

8_10

Rock brokento reveal external moldof shell

Rock brokento revealfossil cast

Shellsburied insediment

Mold, or cavity,forms when originalshell materialis dissolved

Cast forms when moldis filled in with mineralwater

Shellssettle onoceanfloor

How impression fossils form (the most common type)

BOG people

• Bogs filled with danger where you could easily get lost and drown. It's not hard to understand why tribes of long ago used to believe that gods and ghosts inhabited the swamps. Gifts and sacrifices were thought to win their good graces. Prehistoric man offered all kinds of objects to the bogs. So it was that bogs became gigantic offering locations.

• Never before had there been so many bog bodies and offering all in one place. Schatten uit het veen provides an impressive picture of the beliefs and rituals of our ancestors in North-western Europe.

http://www.brunel.ac.uk/depts/geo/people/collinssub/wetland_slides/abernethy_bog_600.jpg

B. Distribution of fossils in layers of rocks?many varietiesand great complexity

first fossils wereaquatic and some

are extinct

few varieties and little complexity

OLDEST

Fossils in every layer

YOUNGEST

STRATIFICATION

Each geologic time period is characterized by certain fossils

(remember the GEO TIME TABLE?)

Why do organisms disappear from the fossil record?

• 1. unable to adapt to a changing environment

• Ex. lake drying, cooling climate ,glaciers• 2. out competed by organisms more

suitable to the new environment• Ex. reptiles competing with early mammals• Or fish vs. amminoids

Diagram of species abundance over time

• Flowering plants and ferns

Diagram of species abundance over time

• Bony fish and amminoids

Notes in student binder

• GREAT! Less writing

VI CONTINENTAL DRIFT or PLATE TECTONICS

• Alfred Wegener early 20th century• initially incorrect explanation but

modified theory is widely accepted (seafloor stationary

and continents move WRONG!!!!)

• 10 MAJOR PLATES AND MANY MINOR PLATES UP TO 100 KM THICK

• Continents ride on the moving crustal plates (less dense material )

•

These are the possible events at the boundary of plates

• Slide• Spread

These are the possible events at the boundary of plates

• Subduction• Subduction w/continents

1. Theory and Evidence• OLD• 1. puzzle pieces• 2. fossil distribution• 3. sediment layers "Gandwanan

Sequence" similar geology on the 4 southern continents sandstone with coal

• black shale• glacial till

NEW• 1. earthquake distribution• shallow quakes at ridges Mid Atlantic• shallow and deep quakes at trenches

subduction• distribution of the RING OF FIRE pg 3032. Movement of plates can be measured

from space3. Dating rocks on opposite sides of ridges

Draw ring of fire on map

End of geological evidence• * the earth is old and has changed

(volcanoes, glaciers, earthquakes)• * organisms that lived in the past are now

gone• * different organism appear in later rocks

than in early ones• therefore new organisms must be

developing from old EVOLUTION

VII EVIDENCE OF EVOLUTION FROM LIVING CREATURES

• Common Ancestry through comparative anatomy

• Georges Buffon 1760 French Naturalist• - observed the feet and legs of many

animals• - concluded that they were but variations

on a single theme

• "The ancestors of backboned animals must have had the same limb structure but has been modified for the life of the individual"

• *This suggests that organisms have changed with time and had a distant common ancestor **

What similarities must exist for organisms to have a common ancestor?

• 1. anatomy (talons, bones, coloration)• 2. physiology (DNA, hemoglobin, digestion)• 3. behavior ( instinct, learning)

Evidence of Evolution from living creatures continued

• HOMOLOGOUS STRUCTURES- organs or parts that are structurally similar but may have different functions (Indicates common ancestry or origin) SEE HANDOUT

• ANALOGOUS STRUCTURES- same function but structurally different (bird and moth wing) Does not indicate any relatedness SEE HANDOUT

• VESTIGIAL ORGANS- remnants of organs or parts that are believed to have been well developed in ancestors but have little function now. (genes are still present)

• (tailbone, appendix, pelvic bones, ) SEE HANDOUT

Vestigial organs• Modern animals may have structures

that serve little or no function– remnants of structures that were functional

in ancestral species– evidence of change over time

• some snakes & whales show remains of the pelvis & leg bones of walking ancestors

• eyes on blind cave fish

• human tail bone

Vestigial organs

• Hind leg bones on whale fossils

Why would whales have pelvis & leg bones if they were always sea creatures?

• BIOCHEMICAL- organic compounds that are essential to certain processes

• (blood proteins, cytochrome C universal and essential to aerobic respiration, DNA , ribosomes) SEE LAB ACTIVITY

Molecular biology• Comparing DNA & protein structure

– universal genetic code! • DNA & RNA

– cytochrome C (respiration)• protein structure

– hemoglobin (gas exchange)• protein structure

Evolutionary relationships among species are documented in their DNA & proteins.Closely related species have sequences that are more similar than distantly related species.

Before comparing the amino acidsHypothesize on closely related pairs

• Pair Reason• 1.• 2.• 3.

Before comparing the amino acidsHypothesize on unrelated pairs

• Pair Reason• 1.• 2.• 3.

• EMBRYOLOGICAL- the study of early developmental forms between organisms can suggest relatedness. (ex. larva forms may look similar though the adults do not) SEE HANDOUT

Comparative embryology• Similar embryological development in

closely related species– all vertebrate embryos have a gill pouch at

one stage of development • fish, frog, snake, birds, human, etc.

Building “family” treesClosely related species (twigs of tree) share same line of descent until their recent divergence from a common ancestor

PATTERNS OF EVOLUTION• MORPOLOGICAL DIVERGENCE related

organisms become less similar due to different environmental circumstances . Develop features to suit their habitat

• MORPHOLOGICAL CONVERGENCE organisms may have similar features but are unrelated. This results from being exposed to similar environmental conditions

• (ex. wombat vs. ground hog )

The Rate of Evolution• Gradualism-(Darwin) small changes

accumulate over a long period of time. (Transitional fossils would be expected)

• Punctuated Equilibrium- (Stephen J. Gould) long periods of uneventful time passes until a catastrophe creates opportunities for new species to flourish. Little change is punctuated by rapid evolution of new species.

Evidence of relatedness

• Example: Transitional forms in the fossil record

Hypothesis: If terrestrial vertebrates (tetrapods) evolved from lobe-finned fish (sarcopterygians), then there should be transitional forms that possess traits that are intermediate.

Previously identified transitional forms

From Ahlberg and Clack, Nature 2006

General Methods

• Scientists looked specifically for the transitional form of interest by sampling…– Appropriate habitats

(stream system)– Appropriate geologic time

(early Late Devonian = 385-376mya)

From Daeschler et al., 2006

http://tiktaalik.uchicago.edu/photos.html

They found Tiktaalik roseae!

From Ahlberg and Clack, Nature 2006

From Daeschler et al., Nature 2006

http://tiktaalik.uchicago.edu/photos.html

From Shubin et al., Nature 2006

http://tiktaalik.uchicago.edu/photos.html

Summary

• The study of and the evidence for evolution clearly fits within the scientific framework.

• We use current evolutionary theory to make and test hypotheses

• There are many thousands of examples of evidence for evolution

What about man?

• Where is the evidence of human ancestry?

What data from whole genome sequencing can tell us about evolution of humans

Example: the Evolutionary Hypothesis

of Common Ancestry

Chromosome Numbers in the great apes:

human (Homo) 4646chimpanzee (Pan) 48gorilla (Gorilla) 48orangutan (Pogo) 48

Testable prediction:Testable prediction: If these organisms share a common ancestor, that ancestor had either 48 chromosomes (24 pairs) or 46 (23 pairs).

Chromosome Numbers in the great apes (Hominidae):

human (Homo) 46chimpanzee (Pan) 48gorilla (Gorilla) 48orangutan (Pogo) 48

Testable prediction:Testable prediction: Common ancestor had 48 chromosomes (24 pairs) and humans carry a fused chromosome; or ancestor had 23 pairs, and apes carry a split chromosome.

CentromereTelomere

Ancestral Chromosomes

FusionHomo sapiens

Inactivated centromere

Telomere sequences

“Chromosome 2 is unique to the human lineage of evolution, having emerged as a result of head-to-head fusion of two acrocentric chromosomes that remained separate in other primates. The precise fusion site has been located in 2q13–2q14.1 (ref. 2; hg 16:114455823 – 114455838), where our analysis confirmed the presence of multiple subtelomeric duplications to chromosomes 1, 5, 8, 9, 10, 12, 19, 21 and 22 (Fig. 3; Supplementary Fig. 3a, region A). During the formation of human chromosome 2, one of the two centromeres became inactivated (2q21, which corresponds to the centromere from chimp chromosome 13) and the centromeric structure quickly deterioriated (42).”

Homo sapiens

Inactivated centromere

Telomere sequences

Hillier et al (2005) “Generation and Annotation of the DNA sequences of human chromosomes 2 and 4,” Nature 434: 724 – 731.

Human Chromosome #2 shows the exact point at which this fusion took place

Chr 2

• Test topics evidence of evolution • EVOLUTION TEST #2• Notes over• Geological evidence of evolution• Biological Evidence of Evolution• Amino Acid Lab• Radiometric Dating• Text (282-292, 740, 327)• Vocabulary (105-113)• Worksheets x2 (History of Life and Evolution)• Plate tectonics Map Know the continents• Homologous vs. analogous• Gradualism vs. Punctuated Equilibrium• Comparative Anatomy Buffon (1-2-5)