Download Study guide chapter 6 ch_6-concepts-science

Science Study Guide – Lesson 2 - INSIDE LIFE
Chapter 6 – EXPLORING CHANGE
Part 2 of 2 - CONCEPTS
(2/5/07 – 3/07/07)
Learning Log – Your Learning Log, which is your “test aid” should contain the
following PRIMARY CONCEPT followed by the 4 SUPPORTING CONCEPTS AS
NOTED BELOW:
PRIMARY CONCEPT – Evolution explains the diversity of life on Earth
SUPPORTING CONCEPTS:
1. Organisms change across time
2. Natural selection explains how species change across time
3. Multiple lines of evidence that confirm evolution
4. Physical properties change, meaning, Earth’s physical
environment changes over time
Note – Items in this study guide that should be included on your learning log will be
followed by the following notation - **Learning Log recommended**
1. Unity and Diversity – Understand that living organisms are similar, (Unity), in
that they all are made up of cells, have DNA within those cells, may share similar
physical features such as having hair, having wings, having 2 or 4 legs, living in
water, and so forth. Understand also that living organisms are different,
(Diversity), in that many organisms differ widely in physical appearance, in the
environment they live in, the fact that animals must consume their food while
plants manufacture their own food, some fly, some walk and some swim. The
concept of Unity and Diversity includes an understanding that living things
can be organized both according to their similarities and their differences.
2. Fossil Records Provide Evidence of Evolution – Fossil records help provide
evidence of evolution by preserving organisms that lived in past eras. Using rock
layers to determine the relative age of fossils, we can compare the
characteristics of these organisms to other fossils found in the same layers, in
different layers and to organisms that are living today. Similarities in
characteristics across time provide evidence of evolution. Additionally, fossil
records provide evidence of environmental shifts over time such as changes from
desert to ocean to forest which in turn might show how organisms have evolved
to survive during these environmental shifts. *** Learning Log Summary
Recommended ***
3. Rock Layers and Relative Dating – Rock layers occur naturally across time in a
predictable sequence with the oldest layers at the bottom and newer layers
toward the top. Fossils found in various rock layers help us to identify organisms
that are similar in age to each other and they also allow us to compare these
organisms to each other and to organisms from both older and more current
times. Rock Layers provide the Relative Age of fossils because we know
that fossils found in a rock layer are the same relative age as the rock layer
itself, and we also know that fossils found in deeper layers are older than
fossils found in higher layers. Additionally, rock layers allow us to identify
environmental shifts across time in the same geographic area. Comparing
fossil characteristics such as similarities, differences or modifications, along with
the ability to identify environmental changes provide strong evidence of evolution
across time.
4. Absolute Dating – Absolute Dating is accomplished using the principles of
Radiometric or Radio Carbon Dating. These procedures use the scientific
analysis of Radioactive Isotopes as they decay from Parent to Daughter
elements and then comparing the amount of each element against the known
Half Life of the Parent element to determine the exact age of minerals or fossils.
Radiometric Dating is used to determine the absolute age of minerals and Radio
Carbon dating is used to determine the absolute age of previously living
organisms. **** Learning Log summary is recommended, include all
bolded terms ***
5. Understanding Absolute Dating – reference the examples below:
1. If you started with 50g of Uranium 235 which has a Half Life of 710 million
years, how much would you have left after 5,680,000,000 years?
Answer – With a Half Life of 710 million years, the uranium 235 would decay a
Total of 8 Half Lives in 5,680,000,000 years, (5,680,000,000 / 710 = 8 Half
Lives) The amount of Uranium 235 would decrease by half for EACH Half Life,
(50 divided by 2 to the 8th power), or as follows: 50g to 25g to 12.5g to 6.25g
to 3.125g to 1.5625g to .278125g to .390625g and finally to .1958125g after
8 half lives.
2. - Suppose you find a rock with 3 times as much Argon 40 as Potassium
40, How old is the rock? Potassium 40 decays to Argon 40 with a Half Life of
1.3 Billion years. (Answer on Next Page)
Answer – After one Half Life, you would have 50% of Potassium 40, and 50%
of Argon 40, or EQUAL amounts of each. After the next Half Life, you
have 25% of 25% of Potassium 40 and 75% of Argon 40 which means you now
have 3 times as much Argon 40 as you have Potassium 40, (25% VS 75%)
You can conclude that 2 Half Lives have passed or a total of 2.6 Billion
years, the rock is 2.6 billion years old.
6. Effects that Variation in Characteristics have on Survival – Different
characteristics of individuals within a species, or different characteristics between
various species can both effect the survival of those species across time.
Variations such as color, size, or speed within a species can affect the ability of
that species to avoid predators which allows greater numbers of those individuals
with the more favorable characteristics to reproduce in greater numbers,
increasing these favorable characteristics within the species and thus,
improving their chances for survival over time. Similarly, variations in
characteristics between similar species, such as the different types of beaks that
birds might have, might affect their ability to eat available food sources. Changes
in environments that effect food sources could favor the survival of species that
have characteristics that make them more able to eat a greater variety of food.
Species with these characteristics will reproduce in greater numbers,
increasing these favorable characteristics and thus, improving their
chances for survival over time.
EXAMPLES OF Variations –
1. If LARGE RED INSECTS and TINY GREEN INSECTS within the same
species of insects both live in a green, grassy field and are both
considered as a good food source for the SPOTTED INSECT EATER,
it is likely that the VARIATION in the size and color of the insects will
result in the Large Red Insects being eaten more often. This
Variation is a favorable characteristic for the Tiny Green Insect and
might eventually result in the reduction or extinction of the Large
Red Insect and a population that has many more Tiny Green Insects.
2. If two species of Spotted Insect Eaters live in the forest and one
species has a long nose, a long tongue and claws on its feet and the
other species has a short nose, a short tongue and webbed feet,
what would happen if all of the insects in the forest live inside hollow
logs? The VARIATION in the species of Spotted Insect Eaters would
most likely result in the long nosed species having success in
catching and eating insects while the short nose version would have
trouble finding food. This VARIATION in characteristics might
eventually result in the reduction or extinction of the short nose
species and the survival of the long nosed version in larger
populations.
7. Natural Selection Explains How Species Change Over Time – Natural
Selection is the process by which favorable traits or characteristics are able
to be passed on to future generations through the reproductive process.
(These are traits or characteristics that are coded in the genes of a species and
are able to be passed on from generation to generation through natural
reproduction) Organisms that have favorable traits, such as color, size, and
speed, or predators that are “generalists” in that they can catch and eat a wide
variety of prey, are more likely to survive and reproduce in larger numbers than
those organisms with unfavorable traits or characteristics. Selective Pressure is
the term that is used to explain the pressure that a predator places on its Prey to
survive, or the pressure that is placed on predators when they must compete for
a limited or specific type of Prey. Natural Selection explains how species
change over time because it provides species with favorable traits a
greater ability to survive the selective pressure across a wider variety of
long term catastrophic or environmental changes. In addition to having a
greater chance for survival, natural selection over long periods of time, (many
generations), may actually lead to even stronger favorable traits through
adaptations or modifications within the genes, providing more evidence
that species change over time. *** Learning Log entry is recommended,
include all bolded items. ***
Examples of NATURAL SELECTION and SELECTIVE PRESSURE
1. Reference Example #1 of VARIATION on Concept 6 above. The
survival of the Tiny Green Insect is an example of Natural Selection,
where the favorable characteristics of the variation result in survival
and growth of the organism with the favorable characteristics. In this
example, the Selective Pressure is provided by the Spotted Insect
Eater and the Natural Selection favors the survival of the Tiny Green
Insect.
2. Reference Example #2 of VARIATION on Concept 6 above. The
survival of the Long Nose Insect Eater is an example of Natural
Selection, where the favorable characteristics of the variation results
in survival and growth of the organism with the favorable
characteristics. In this example, Selective Pressure is provided by
the insects that only live in hollow logs and the Natural Selection
favors the Insect Eater with the long nose that can reach the insects
in the hollow logs.
8. Darwin’s Evidence and Observations from his 5 year journey – During
Darwin’s journey that began in 1831, he collected thousands of specimens and
recorded extensive notes about his journey. Many of these key observations
and the evidence he collected and wrote about helped him to support his
theories about how life changes over time and were the basis for his theory of
Evolution. Some examples of his observations are as follows:
a. Plants and animals have adaptations, which are characteristics
that help organisms survive and reproduce in particular
environments.
b. Some species have similar body structures that are adapted for
different purposes. Examples: Wings of Penguins are used as
flippers, wings of Rheas are used as sails, wings of the Steamer
Duck are used as paddles while the majority of bird wings are
used to fly
c. Organisms living in temperate areas of one continent were more
similar to organisms living in tropical areas on the same continent
than they were to organisms living in temperate areas on different
continents. This led him to believe that in Geographical
Distribution, similar species came from a common ancestor
that lived in the same geographical area rather than from a
particular environment that may be similar in many different
geographical areas on different continents.
d. Many fossils look similar to existing species
e. Younger rock layers had more fossils that were similar to existing
species than did older rock layers. (meaning older rock layers
contained more fossils of organisms that no longer existed)
9. Understanding Darwin’s Theory of Evolution – Evolution provides an
explanation for how species change across time. Evolution only occurs when
there are variations in populations and when there are selective pressures
acting on those variations. For example, some individuals within a population
might have variations in one or more characteristics. Selective pressures cause
individuals with beneficial characteristics, also called adaptations, to survive and
cause individuals without the adaptations to die off. This process is called
natural selection. Across time, more of the individuals with the adaptations
survive and reproduce. As more of the populations have the adaptations,
eventually the population can be recognized as a distinct new species.
***** Learning Log entry is recommended. A complete explanation of
evolution should include all of the bolded words in this concept.