UNIT 7 – EVIDENCE OF EVOLUTION

STANDARD: S7L5Students will examine the evolution of living organisms through inherited characteristics that promote survival of organisms and the survival of successive generations of their offspring.

a. Explain that physical characteristics of organisms have changed over successive generations (e.g. Darwin’s finches and peppered moths of Manchester).

b. Describe ways in which species on earth have evolved due to natural selection.

c. Trace evidence that the fossil record found in sedimentary rock provides evidence for the long history of changing life forms.

ESSENTIAL QUESTIONS•How do physical characteristics of organisms demonstrate/support the theory of evolution?•How does natural selection affect the evolution of species on Earth?•How does the fossil record provide evidence of evolution?

Key ConceptsChanges in species occur due to natural selection, reproduction and environmental conditions.

Physical characteristics of organisms change over time.

Fossils provide evidence of change.

Misconceptions:What you think you know!

Evolution means “man from monkey.” Evolution no longer occurs. Evolution is “only a theory.” Fossils are only found in sedimentary rocks. Evolution is an origin of life/a belief system Evolution is something an organism does

on purpose. Individual organism change to meet the

needs of their environment.

MASS EXTINCTIONOne of several periods in Earth’s history when large numbers of species became extinct at nearly the same time.

FOSSILSThe preserved remains or imprints of ancient organisms in the Earth.

Sedimentary Rocks

Most fossils form in sedimentary rock. This rock is formed when existing rock is broken

down by wind, water, or ice. The small particles that result are carried into

lakes or seas, where they settle to the bottom. Over time, layers of particles build up. The weight of the layers causes the lower layers

to turn into rock. If an organism dies and is buried in the

sediment, the remains are preserved within the rock.

How Fossils Form in Sedimentary Rocks:

Types of Fossils

Mold Fossils: made when an impression or imprint of a bone, shell, leaf, etc. is made.

Cast Fossils: made when minerals fill in an animal print, shell, bone, etc.

Body Fossils: are actual remains preserved in tar, ice, amber, etc. Trace Fossils: record movement & behavior such as footprints,

tooth marks, nests, etc. *NOTE: It is difficult for fossils to be found because cells have no hard parts

that will fossilize!

The FOSSIL RECORD

Relative dating/age: compares ages of fossils to determine if a fossil is older than another by the rock layer it was found in.

Radioactive dating: used to determine the actual age of a fossil by looking at the half-life of the radioactive elements it has.

The fossil record is an ordered arrangement of fossils developed using the above dating methods and shows that species evolve over time.

Are there gaps in the Fossil Record?YES! A theory that accounts for these gaps is called punctuated equilibria. According to this theory, species evolve quickly during relatively short periods. These periods of rapid change are separated by long periods of little or no change.

CHARLES DARWINA naturalist (person that studies the natural world) who’s observations led him to develop one of the most important scientific theories of all time: the theory of evolution by natural selection.

CHARLES DARWINImportant observations included:

•The diversity of living things•The remains of ancient organisms•The characteristics of organisms on the Galapagos Islands

Darwin’s Reasoning

Darwin reasoned that plants or animals that arrived on the Galapagos Islands faced conditions that were different from those on the mainland.

He hypothesized the species gradually changed over many generations and became better adapted to the new conditions.

The gradual change in a species over time is called evolution.

Darwin’s Finches

Darwin observed finches on the Galapagos. Were they different finch species or just different varieties of

the same species? Different species –

Beaks were differenton different islands.

But really…the birds changed over time as a result of their surroundings.

Pepper Moths

9th century England: light colored pepperedmoths perched on light colored tree bark.

Dark colored moths were present however not as common.

After the Industrial Revolution, soot from burning coal stained the trees dark brown. More dark colored moths appeared.

Birds are the main predators of peppered moths. Moths that blend into the tree bark are harder to see & catch making them more likely to survive & reproduce.

ADAPTATION

A characteristic, a behavior, or any inherited trait that makes a species able to survive and reproduce in a particular environment.

EVOLUTIONThe process through which species change over time.

NATURAL SELECTIONThe process through which members of a species that are best suited to their environment survive and reproduce at a higher rate than other members of the species.

Natural Selection

Factors that affect the process of natural selection: Overproduction – There are more offspring produced than

resources available (food, water, & living space).

Variation – any difference between individuals of the same species. Color of insects, what they eat, etc.

Competition – members of a species must compete with each other to survive.

SURVIVAL OF THE FITTESTThose organisms that are best adapted to their environment are more likely to survive and reproduce. When they reproduce, their offspring will inherit those traits that helped the parents survive. At the same time, those organisms that are less fit do not survive and reproduce.

Speciation: How do new species form? New species can form when a group of

individuals remains isolated from the rest of its species long enough to evolve different traits.

Isolation (complete separation) occurs when some members of a species become cut off from the rest of the species.

Group members may be separated by such things as a river, volcano, or a mountain range.

Homologous Structures

Similar structures that related species have inherited from a common ancestor.