evolution. california state standard 3. biological evolution accounts for the diversity of species...

Evolution

California State Standard

3. Biological evolution accounts for the diversity of species developed through gradual processes over many generations.

c. Independent lines of evidence from geology, fossils, and comparative anatomy provide the bases for the theory of evolution.

What is Evolution?

Evolution The gradual change of a species through

adaptations over a period of time.

Adaptation A structure, behavior, or internal process that

makes an organism better suited to their environment.

Change Over Time The Earth has changed over time

TemperatureClimateEruptionsEarthquakesChange in sea levelChange in land masses due to Continental Drift

Pangea

Continental Drift The theory of continental drift, suggests that in the Earth’s

history, continents have moved due to plate tectonics, and are still moving today at a rate of about six centimeters per year. Pangea refers to the supercontinent that connected all of the land masses.

Evidence of Evolution

Fossils Comparative Anatomy Comparative Embryology Comparative Biochemistry

Fossils

Fossils Evidence of an organism

that once existed.

The study of Paleontology uses fossils to understand events that happened long ago, ancient climates, and ancient geography.

How are fossils formed? Fossils are formed by being buried in mud, sand,

or clay after they die.

Most fossils are found in sedimentary rocks. These rocks form at relatively low temperatures and pressures that may prevent damage to the organism.

The Fossilization Process

Few organisms become fossilized because, without burial, bacteria and fungi immediately decompose (break down) the dead bodies.

Occasionally, organisms do become fossils in a process that usually takes many years.

An organism or its body are washed into a body of water.

Sediments rapidly cover the body.

Over time, additional layers of sediments compress the area around the body.

Earth movement or erosion may expose the fossil many years after it formed.

Types of Fossils

Imprint Fossils

Mold & Casts Fossils

Petrified Fossils

Preserved Fossils

Imprint Fossils

Imprint fossils, also called trace fossils, are any evidence left by an organism, such as a footprint, trail, or burrow.

Mold & Cast Fossils

A mold forms when an organism is buried in sediment and then decays, leaving an empty space.

When the empty space is filled in with minerals, a replica or cast is made.

Petrified Fossils

In petrified fossils, minerals sometimes penetrate and replace the hard parts of an organism.

Preserved Fossils A preserved fossil is

an entire organism trapped and preserved in ice, tar, or amber, which is hardened sap.

The Age of Fossils

Scientists use a variety of methods to determine the age of fossils. One method is relative dating.

If the rock layers have not been disturbed, the relative age can be determined by the position in the soil and rock layers.

Relative Age The lower layer

contains fossils that are older and less complex.

The upper layer contains fossils that are younger and more complex.

The Fossil Record

Absolute Age Radioactive dating is used to find the specific

ages of rocks, which may contain fossils. Radioactive isotopes are atoms that are unstable

and break down or decay over time, giving off radiation and forming a new isotope.

Every radioactive isotope has a characteristic decay rate, scientists use the rate of decay as a type of clock, called half-life.

Potassium-40 decays to Argon-40 to half its original amount in 1.3 billion years.

Carbon-14 decays to half its original amount in 5730 years and is used to date fossils less than 70,000 years old.

Geologic Time Scale By examining and dating

sedimentary rock and fossils, scientists have put together a chronology, or calendar, of Earth’s history, called the geologic time scale.

Time frames in evolution are based on the geologic time scale.

Other Evidence of Evolution

Comparative Anatomy The comparison of body structures from different

species.Homologous Structures

Analogous Structures

Vestigial Structures

Homologous Structures

Organs or body parts that are similar in structure, function, or both.

Organisms with homologous structures have a common ancestor.

Homologous Structures

Analogous Structures

Organs or body parts that have a similar function, but a different structure.

Organisms with analogous structures do not share a common ancestor.

Analogous Structures

Vestigial Structures Organs or body parts that do not have a current

function, but may be useful in other organisms.

A body structure in a present-day organism that no longer serves its original purpose, but was probably useful to an ancestor.

TOP 10 Vestigial Organs

10. The wings on flightless birds

1. The human appendix1. The human appendix2. Male breast tissue and nipples2. Male breast tissue and nipples3. Reproduction of whiptail lizards3. Reproduction of whiptail lizards4. Sexual organs of dandelions4. Sexual organs of dandelions5. Wisdom teeth in humans5. Wisdom teeth in humans6. The eyes of a blind fish6. The eyes of a blind fish7. The human tailbone7. The human tailbone8. Erector pili and body hair8. Erector pili and body hair9. Hind leg bones in whales & snakes9. Hind leg bones in whales & snakes

Comparative Embryology

The comparison of the early stages of development of different species.

The shared features in the young embryos suggest evolution from a distant, common ancestor.

fish reptile bird mammal

Evidence from Embryology

58 days old 166 days old

4 mm long 6 cm long

An Elephant Embryo

Comparative Biochemistry

Studying the similarities of organisms at a biochemical level, for example DNA, ATP, and enzymes.

Comparison of OrganismsPercent Substitutions

of Amino Acids in Cytochrome c Residues

Two orders of mammals

Birds vs. mammals

Amphibians vs. birds

Fish vs. land vertebrates

Insects vs. vertebrates

Algae vs. animals

5 and 10

8-12

14-18

18-22

27-34

57

Blood, DNA, RNA, amino acids, enzymes, and other proteins (Example Cytochrome C)

Evidence from Biochemistry

Scientists have constructed evolutionary diagrams that show levels of relationships among species.

Scientists combine data from fossils, comparative anatomy, embryology, and biochemistry in order to interpret the evolutionary relationships among species.