Ch.14 – History of Life 14.1 – Fossil Evidence of Change

Fossils have been found of organisms that no longer live on Earth.

Traces (fossils) of modern organisms can only be dated back to a certain point in

the Earth’s 4.6 billion year history.

Therefore, Life on Earth has changed (EVOLVED) over the course of the

Earth’s history and continue to do so.

What do we know about fossils and their age?How/Why do living things change over time?

Ch.14 – History of Life 14.1 – Fossil Evidence of Change

Fossils Any evidence of an organism

Trace Mold & CastReplacement

Petrified

Preserved

Ch.14 – History of Life 14.1 – Fossil Evidence of Change

Nearly all fossils form in sedimentary rock

because it prevents rapid decomposition(99% of all living things left no fossils behind)

Ch.14 – History of Life 14.1 – Fossil Evidence of Change

Fossil Dating

Relative Dating

Based on the law of superposition:

newer layers of rock form on top of

older layers

-Cannot give exact age

-Earth’s geology is constantly shifting

changing the position of artifacts

Absolute Dating

Radiometric Dating

Uses the half life of radioactive

isotopes in order to determine specific age.

Ch.14 – History of Life 14.1 – Fossil Evidence of Change

Fossil Dating

Relative Dating

Based on the law of superposition:

newer layers of rock form on top of

older layers

-Cannot give exact age

-Earth’s geology is constantly shifting

changing the position of artifacts

Absolute Dating

Radiometric Dating

Uses the half life of radioactive

isotopes in order to determine specific age.

Ch.14 – History of Life 14.1 – Fossil Evidence of Change

Absolute Dating

C14 decays to N14

Half-life – 5730 years

U238 decays to Pb206

Half-life – 4.5 billion years

Ch.14 – History of Life 14.1 – Fossil Evidence of Change

Geologic Time Scale

Precambrian

•Earth formed about 4.6 billion years ago•It took about 500 million years for the crust to form and for water to start collecting on the surface•Prokaryotic & eukaryotic unicellular organisms emerge•Autotrophic prokaryotes begin to enrich the atmosphere with O2. •Multicellular organisms emerge (1st animals)

4600mya – 542mya

Ch.14 – History of Life 14.1 – Fossil Evidence of Change

Paleozoic

•Animals diversify•1st plants•1st vertebrates•Life moves out of the oceans•Insects, amphibians, reptiles scatter•Ferns & Evergreens cover the Earth

488mya – 251mya

Ch.14 – History of Life 14.1 – Fossil Evidence of Change

Mesozoic

•1st mammals•Dinosaurs•Birds•Gymnosperms (seed-bearing plants) diversify•Flowering plants appear•Mass extinction wiped out all dinosaurs, except for the birds, at the end of the era.

199mya – 65mya

Ch.14 – History of Life 14.1 – Fossil Evidence of Change

Cenozoic

•Mammals diversify and scatter•Flowering plants scatter•Primates appear•Humans create civilizations and pollution

55mya – present

Ch.14 – History of Life 14.2 – Origin of Life

Origin of Life

Early Ideas Spontaneous Generation

Life arises from non-life

Francisco Reddi 1668 Louis Pasteur mid 1800’s

Biogenesis Life arises from existing life

Ch.14 – History of Life 14.2 – Origin of Life

Origin of Life

Origin MovieOrigin Movie

Ch.15 – Evolution 15.1 – Darwin’s Theory of Natural Selection

A new era of biology began on November 24, 1859, the day Charles Darwin published On the Origin of

Species by Means of Natural Selection

Darwin made two main points in his book:1. Many current species are descendants of

ancestral species2. Natural selection is the mechanism for this

evolutionary process

Ch.15 – Evolution 15.1 – Darwin’s Theory of Natural Selection

Darwin’s Influences:Geologists Hutton and Lyell (late 1700’s) perceived that changes in Earth’s surface can result from slow continuous actions still operating today (gradualism)

Thomas Robert Malthus (late 1700’s) hypothesized that in nature plants and animals produce far more

offspring than can survive, and that Man too is capable of overproducing if left unchecked

Ch.15 – Evolution 15.1 – Darwin’s Theory of Natural Selection

Darwin’s Observations:

After graduating college Darwin was accepted on board the

HMS Beagle, which circled the world from 1831-1836

He observed plant and animal

adaptations from many diverse environments

Ch.15 – Evolution 15.1 – Darwin’s Theory of Natural Selection

Darwin’s most famous observations were of finches found on the Galapagos Islands off the coast of Ecuador

Many of the islands had unique climate

& vegetation

Similar looking finches found on the different islands had different

adaptations from each other and were

different from finches found on the mainland

Ch.15 – Evolution 15.1 – Darwin’s Theory of Natural Selection

Upon return to England Darwin began reflecting on his observations and started hypothesizing about how

populations change over time.

He did not agree with French scientist

Jean-Baptiste Lamarck that living things changed due to use and disuse of

certain characteristics

Ch.15 – Evolution 15.1 – Darwin’s Theory of Natural Selection

With his knowledge of artificial selection – done by farmers for centuries in order to improve their livestock or crop populations, and the observations made on the

HMS Beagle, Darwin put together his theory of Natural Selection

Over-production

Over-production

HeritableGenetic Variation

HeritableGenetic Variation

Reproductive Advantage

Reproductive Advantage

New PopulationNew PopulationOriginal

Population

Original Population

++ ==

Descent with ModificationDescent with Modification

Ch.15 – Evolution 15.1 – Darwin’s Theory of Natural Selection

An adaptation is any characteristic that increases fitness, which is defined as the ability

to survive and to produce fertile offspring

Over-production

Over-production

Genetic Variation

Genetic Variation

Reproductive Advantage

Reproductive Advantage

New PopulationNew PopulationOriginal

Population

Original Population

++ ==

Descent with ModificationDescent with Modification

Survival of the Fittest

Living things adapt to their environment

Ch.15 – Evolution 15.2 - Evidence for Evolution

Evidence for Evolution

The Fossil Record

Comparative Anatomy

Comparative Embryology

Comparative Biochemistry

The Darwinian view of life predicts that

evolutionary transitions should leave signs in the

fossil record

Paleontologists have discovered fossils of

many such transitional forms

Ch.15 – Evolution 15.2 - Evidence for Evolution

The Fossil Record The Darwinian view of life predicts that

evolutionary transitions should leave signs in the

fossil record

Paleontologists have discovered fossils of

many such transitional forms

Ch.15 – Evolution 15.2 - Evidence for Evolution

Most animals show similarities in internal

structure

Comparative Anatomy

Homologous Structures

VestigialStructures

Similar structure – different use Structures with reduced function (“leftover parts”)

Ch.15 – Evolution 15.2 - Evidence for Evolution

Vertebrate embryos exhibit homologous structures

during certain phases of development

Comparative Embryology

Ch.15 – Evolution 15.2 - Evidence for Evolution

Insert info about biological resistance…visualizing evolution…

Ch.15 – Evolution 15.2 - Evidence for Evolution

Many organisms share complex biomolecules.

The more closely related the more similar the

molecules

Comparative Biochemistry

1. How does the concept of “descent with modification” explain both the unity and

diversity of life?

2. Explain how over-reproduction and heritable

variation relate to evolution by natural selection

3. If you found a fossil of a mammal that lived high in the

Andes, would you predict that it would more closely resemble present –day mammals from South American jungles or

present –day mammals that live high in Asian mountains?

Explain.

4. Increased UV irradiation causes the skin of humans to become more darkly pigmented over a

period of days. The notion that the offspring of such tanned

individuals should consequently inherit darkened skin from their

parents is consistent with the ideas of whom?

5. Most species of whale have 5 phalange (finger bones)

supporting their flippers. Why would a whale have fingers?

What would you call those phalange?

Have you been paying attention?

Have you been paying attention?

Ch.15 – Evolution 15.3 – Shaping Evolutionary Theory

Population Genetics Macroevolution

Natural selection works on individuals but only populations evolve

Evolution is the change of the allelic frequency in a population

bbbb BBBBbbbbBbBb

BbBb bbbbbbbbbbbb

bbbb bbbbbbbbBbBb

BbBb BbBbBbBbbbbb

BBBB BbBbbbbbBbBb

BBBB BBBBbbbbBbBb

BbBb bbbbBBBBbbbb

bbbb BBBBbbbbBbBb

BbBb BbBbBBBBbbbb

BBBB bbbbbbbbBbBb

20 bugs40 alleles for color

(incompletely dominant)

20 bugs40 alleles for color

(incompletely dominant)

B – 18/40 = .45b - 22/40 = .55

B – 18/40 = .45b - 22/40 = .55

B – 12/40 = .30b - 28/40 = .70

B – 12/40 = .30b - 28/40 = .70

Over TimeOver Time

Ch.15 – Evolution 15.3 – Shaping Evolutionary Theory

Populations evolve due to three main causes:Natural Selection – Genetic Drift – Gene Flow

Natural Selection alters populations in one of three ways

Original Population Distribution

Original Population Distribution

Stabilizing Selection

Stabilizing Selection

Directional SelectionDirectional Selection

Disruptive Selection

Disruptive Selection

The average is selected forThe average is selected for

One Extreme is selected forOne Extreme is selected forBoth extremes are selected forBoth extremes are selected for

Ch.15 – Evolution 15.3 – Shaping Evolutionary Theory

Populations evolve due to three main causes:Natural Selection – Genetic Drift – Gene FlowGenetic Drift is random changes in a gene pool usually due to independent assortment

Usually only occurs in small populations2 Examples2 Examples

Founder Effect Bottleneck Effect

A small sample of the population relocatesA small sample of the population relocatesA population declines to a small # and then reboundsA population declines to a small # and then rebounds

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Ch.15 – Evolution 15.3 – Shaping Evolutionary Theory

Populations evolve due to three main causes:Natural Selection – Genetic Drift – Gene FlowGene Flow is the exchange of genes between populations from migration

Ch.15 – Evolution 15.3 – Shaping Evolutionary Theory

Populations can also evolve due to nonrandom mating and mutations

Therefore, according to the Hardy-Weinberg PrincipleA population in genetic equilibrium must meet 5

conditions:No Genetic DriftNo Gene FlowNo Mutation

Random MatingNo Natural Selection

Ch.15 – Evolution 15.3 – Shaping Evolutionary Theory

Speciation

New species arise because of reproductive isolation

Reproductive isolation either occurs with a physical barrier or without a physical barrier

Reproductive isolation either occurs with a physical barrier or without a physical barrier

Allopatric Sympatric

Speciation AnimationSpeciation Animation

Ch.15 – Evolution 15.3 – Shaping Evolutionary Theory

There are two hypothesis as to how different species come to exist

GradualismPunctuated Equilibrium

Changes occur little by little

Changes occur rapidly between periods of little

change

Ch.15 – Evolution 15.3 – Shaping Evolutionary Theory

Patterns of Evolution

Convergent EvolutionDivergent Evolution

or Adaptive Radiation

Many species arise from one original species

Organisms not closely related evolve similar

traits

Ch.15 – Evolution 15.3 – Shaping Evolutionary Theory

Patterns of Evolution

Coevolution

Many species evolve in close relationship with other species