Chapter 17: The History of Life

Section 17-1: The Fossil Record

I. Interpreting fossil EvidenceA. Paleontologists are scientists who collect

and study fossils.B. Age of fossils is determined using two

techniques:1. Relative Dating: 2. Radioactive Dating

C. Relative Dating1. Comparing a fossils placement

with fossils in other layers of rock.

2. Oldest layers on the bottom, recent layers on top.

D. Radioactive Dating1. Some elements found in rocks are radioactive. 2. Radioactive elements break down, into non

radioactive elements at a steady rate. 3. A half life is the length of time required for half

of the radioactive atoms in a sample to decay.4. The age of a fossil is calculated

based on the amount of remaining radioactive isotopes it contains.

Q. The half-life of Carbon-14 is 5,730 years. How much of the original C-14 in an organism would remain in a fossil that is 11,460 years old? _____________

Q. The half-life of the fictitious radioactive element X is 5,420 years.

• How old is a fossil that has 1/8th the original amount of the element? _____________________________years old

• If I start out with 30 grams of element X, how much will I have after 3 half-lives? _____________________grams

• If a fossil is found that has 5 grams of element X in it and I know that it originally had 40 grams in it, how old is that fossil? ___________________________________ years old

II. Origin of Eukaryotic Cells (with nuclei)A. The prokaryotic cells began evolving internal cell

membranes. The result was the ancestor of eukaryotic cells.

B. According to endosymbiotic theory some prokaryotes entered this ancestral eukaryote & began living inside the larger cell. Over time, a symbiotic relationship evolved.

C. The prokaryotes that had an ability to use oxygen to generate energy-rich molecules of ATP, evolved into the mitochondria.

D. The prokaryotes that carried out photosynthesis evolved into the chloroplasts.

Endosymbiotic Theory

Section 17-4: Patterns of Evolution

Macroevolution - large-scale evolutionary patterns & processes that occur over long periods of time.A. Mass extinction

1. Huge numbers of species along with ecological systems disappear

2. Disrupts energy flow, and food webs collapse.3. Survivors are left with an open habitat = burst of

evolution = many new species

B. Adaptive radiation1. A single species or a small group of species

evolved, through natural selection into diverse forms that live in different ways.

2. Example: Darwin’s Finches

3. The first dinosaurs and the earliest mammals evolved at the same time. • Dinosaurs & ancient reptiles, underwent an

adaptive radiation first & “ruled” Earth for about 150 million years

• During that time, mammals remained small & relatively scarce.

• The disappearance of the dinosaurs cleared the way for the great adaptive radiation of mammals.

Adaptive Radiation of Mammals

C. Convergent evolution - unrelated organisms resemble one another.

1. The organisms undergo adaptive radiation in different places or at different times but in similar ecological environments/climate.

2. Natural selection molds different body structures, and they look similar & function in the same way.• similar shapes of sharks and dolphins (streamlined

bodies with parts that work like paddles• structures such as a dolphin's flukes & a fish's tail fin

(look & function similarly, but are made up of parts that do not share a common evolutionary history, are called analogous structures).

D. Coevolution - two species evolve in response to changes in each other over time.

1. Organisms that are closely connected to one another by ecological interactions evolve together.• flowering plants can reproduce only if the shape, color,

& odor of their flowers attract a specific type of pollinator.

2. An evolutionary change in one organism may be followed by a corresponding change in another organism.• relationships between plants and plant-eating insects.

Some plants have evolved poisonous compounds that prevent insects from feeding on them. Natural selection in herbivorous insects began to favor any variants that could alter, inactivate, or eliminate those poisons.

E. Gradualism versus Punctuated equilibrium 1. According to Darwin, biological change is slow

and steady, known as gradualism. 2. According to Stephen Jay Gould, the long and

stable periods interrupted by brief periods of more rapid change is called as Punctuated Equilibrium.

3. Rapid evolution may occur when a small population becomes isolated and evolve rapidly or when a small group of organisms migrates to a new environment.

F. Changes in developmental genes1. The “master control genes,” called hox genes,

guide development of major body structures in animals.

2. Changes in the expression of developmental genes may explain how evolution occurred.