Pat Hamer
Per. 5
Chapter 13 Outline
I.
Evolution
and Life’s Diversity
a.
i.
ii. At each place he went ashore he collected animal and plant specimen to add to his collection
b. The Diversity of Life
i. Diversity is the variety of living things
ii.
iii. Researchers estimate that 99.9% of species that have at some time lived on earth are now extinct.
c. Fitness: To Survive and Reproduce
i.
Noted that “the
physical traits and behaviors that enable organisms to survive and reproduce in
their environment give them what
ii.
iii. Common Descent – species which descended from common ancestors
iv. Adaptation – Any inherited characteristic that increases an animal’s or plant’s fitness for survival.
II.
The Age
of the Earth
a. Evidence in Stone
i. Originally believed that Earth was only thousands of years old and remained unchanged
ii. in 18th and 19th century opinions changed and made a hypothesis that the Earth was very old and had changed slowly over a long period of time by natural forces.
iii. James Hutton in 1778 proposed that rocks, mountains, and valleys had been changed gradually by rain, heat, cold, and activity of volcanoes, and other natural forces
iv. Forces beneath the Earth’s surface twist and bend some rock layers, bury others, and even push up some parts of the sea floor in mountain ranges which could prove that the earth has changed over a long period of time.
v. Fossils – preserved remains of ancient organisms
b. The Geologic Time Scale: A Clock in the Rocks
i. Geologic time scale – Biologists and Geologists date the Earth’s past with the help of a record in the rocks.
ii. Certain layers of rock often appeared in the same vertical order wherever they were found
1. the position of the layers are relative to each other determines age
iii. Relative Dating – is a technique used by scientists to determine the age of fossils relative to other fossils in different layers of rock.
c. Radioactive Dating
i. Radioactivity provided scientists with a tool that could determine the age of rocks
ii. Radioactive Elements – decay or break down, into nonradioactive elements at a very steady rate.
iii. Half-Life – the length of time required for half the radioactive atoms in a sample to decay
1. Each element has a different half life
iv. Elements that have different half-lives and provide natural “clocks” can be used to help date rocks and specimens of different ages.
1. Carbon 14 is very useful in this as is Uranium 238 and Potassium 40
v. Absolute Dating – enables researchers to calculate the actual age of a sample.
1. Evidence proved by radioactive clocks along with observations of long term geological processes, has enabled geologists to compile a remarkably accurate history of our planet.
vi. The age of the Earth is about 4.5 billion years old.
vii. Earth divided into large units of time as Eras, which are divided into Periods, and in turn further divided into Epochs.
III.
The
Fossil Record
a. How fossils Form
i. Depend on a great deal of chance that the environment and situation must be nearly perfect for it to work.
ii. Sedimentary Rock – are formed when exposure to rain, heat, and cold breaks down existing rocks into small particles of sand, silt, and clay.
1. travel through rivers and eventually settle at bottom of rivers
b. Fossil Evidence: Problems in Assembling the Puzzle
i. “The chancy process by which organisms are fossilized means that the fossil record is not as complete as we would like it to be. For every organism that leaves a proper fossil, many die and vanish without leaving a trace.”
ii. Organisms that live in mountains and deserts may never become part of fossil record since there is no sedimentary rock to encase the fossils.
iii. Quality of fossil preservation varies greatly from almost microscopic view of an entire fossil, to hardly a fossil at all.
c. What the Fossil Record Tells Us
i. Paleontologists – Scientists who study fossils
ii. Fossil Record – collection of millions of fossils and, represents the preserved collective history of the Earth’s organisms.
iii. Fossil record is missing many pieces and is incomplete
iv. Tells of major changes that occurred in Earth’s climate and geography
IV.
Evidence
from Living Organisms
a. Similarities in Early Development
i. Embryos – organisms at early stages of development.
1. Scientists noticed that the embryos of many different animals look very similar.
2. could hint that there are similar genes at work
3. Later in development the embryos gradually became more and more dissimilar
b. Similarities in Body Structure
i. The embryos that look the same in early stages of development have their forelimbs change
ii. Homologous Structures – body structures that develop from the same body parts
iii. Vestigial Organs – organs that seem to serve little or no purpose
1. these serve as new adaptations that could be from evolution
2. Even humans have vestigial body parts
c. Similarities in Chemical Compounds
i. All organisms share many biochemical details
ii. DNA of all eukaryotic organisms always have the same basic structure and replicates in the same way
iii. The more closely related two species are the more closely their important chemical compounds resemble each other.
d. What Homologies Tell Us
i. Similarities in structure and biochemistry provide powerful evidence that all living things evolved from common ancestors.
ii.