Download Chapter Seven: Evolution of Living Things

Name:_______________________________ Date:_____________ Class Pd:_______
Chapter 7: The Evolution of Living Things-KEY
1.
Read “The Big Idea” on pg 164. Biological Evolution explains how populations change
over time.
2.
THINK ABOUT IT: What is it called when an organism blends into its environment?
camouflage.
SECTION 1: CHANGE OVER TIME (pg 166-172)
Differences Among Organisms
3. A characteristic that helps an organism survive and reproduce in its environment is
called an adaptation.
4.
Adaptations may be physical (fur color, presence of a long neck) or behavioral (help it
find food, protect itself, or reproduce).
5.
A group of organisms that can mate with one another to produce fertile offspring is
called a species.
6.
A population is a group of individuals of the same species living in the same place.
7.
Scientists theorize that as populations change over time, new species form.
8.
The earth has changed a great deal during its history, and living things have also
changed to adapt to new environments. The process in which populations gradually
change over time is called evolution.
Evidence of Changes over Time
9. Scientists have gathered a lot evidence that change has occurred over time:
1) Fossils - The remains or imprints of once living organisms found in layers of rock.
These are most commonly preserved in sedimentary rock.
2) By studying fossils, scientists have made a timeline of life known as the
fossil record. Fossils from newer layers of the Earth’s crust tend to be similar to
present-day organisms. Older fossils are less similar to present-day organisms.
Evidence of Ancestry
10. Scientists observe that all living organisms have characteristics in common and inherit
characteristics in similar ways. So, scientists think that all living species descended
from common ancestors.
11.
Scientists have drawn a tree of life to include all known organisms.
Examining Organisms
12. Scientists think that the ancient ancestor of whales was probably a mammal that
lived on land and could run on four legs.
13. Each species shown in Figure 7 shared some traits with earlier species. Other
evidence for the relationship between land mammals and whales includes hip bones
found in both modern whales and the four-legged ancestors.
Comparing Organisms
14. Evidence that groups of organisms have common ancestry can be found by comparing
the groups’ DNA.
15. Organisms contain evidence that populations and species undergo changes in traits
and DNA over time.
16. What do your arm, the front leg of a cat, the front flipper of a dolphin, and a bat’s
wing all have in common? And what do these similarities suggest?
The structure and order of bones are similar in all four. This suggests that they
all share a common ancestor.
17. Scientists use molecular data, the comparison of traits, and fossils to support the
theory that because all existing species have DNA, all species share a common
ancestor.
18. THINK ABOUT IT: You are comparing the DNA of a cat (a mammal), a tree (a plant),
and a dog (a mammal). Which two species will be most closely related? Why?
A dog and a cat have more traits in common, so they are more closely related.
They are both mammals which means they give birth to live young, they breathe
air, and they produce milk. A tree does not do any of these things, so trees are
less closely related.
SECTION 2: HOW DOES EVOLUTION HAPPEN? (pg 174-179)
Charles Darwin
1.
Charles Darwin sailed around the earth for five years on a British ship called the
HMS Beagle as a naturalist – a scientist who studies nature. Look at Figure 3 on page
175 to see his journey.
2.
One interesting place that Darwin’s ship visited was the Galapagos islands.
3.
Darwin observed that the birds on the Galapagos Islands were a little different than
the finches in Ecuador, and the finches on each island differed from the finches on
other islands. Look at Figure 4. The differences in each island’s finches were based
on the way the finches obtained food.
Darwin’s Thinking
4. After visiting the Galapagos Islands, Darwin wondered by the animals seemed so
similar to each other yet had so many different adaptations.
5.
Malthus warned that food supplies could not support unlimited population growth.
ACTIVITY #1: Pick up a legal-size paper from the front table titled “Activity #1” and 1
petri dish containing beans, and 1 petri dish containing beads. On the worksheet are blocks
labeled “food supply.” Put one bean in block #1, two beans in block #2, three in block #3,
and continue across the table by adding one additional bean per square for a total of five
squares.
Below these piles are blocks labeled “human population.” Start in block #1 and add 1 bead.
In block #2, add two beads. In block #3, add four beads. In block #4, add 8 beads, and in
block #5 add 16 beads. The population is doubling in each square. All five blocks should be
filled.
QUESTIONS FROM THIS ACTIVITY:
What would happen to the food supply and the human population in this activity if the
population continues to grow at this rate?
The food supplies would diminish, so the human population would starve
What prevents unlimited growth from happening in the human population?
Human populations do not grow indefinitely because they are limited by the
choices they make or by problems such as starvation disease
6.
After reading Malthus’s book, Darwin realized that populations of all species are
limited by starvation, disease, competition, and predation. Only a limited number of
individuals survive to reproduce.
Darwin’s Theory of Natural Selection
7. In his book, “On the Origin of Species by Means of Natural Selection,” Darwin
proposed the theory that evolution happens through natural selection.
8.
Natural Selection is the process by which organisms that are better adapted to their
environment survive and reproduce more successfully than less well adapted
organisms do.
9.
The process of natural selection is explained in 4 parts. Look at Figure 7. Explain each
of the four elements in your own words.
1) Overproduction:
A species produces more individuals than it needs. Some will develop into
adults and others will not survive.
2) Inherited Variation:
Each individual has its own set of traits similar to (but not identical to) its
parents.
3) Struggle to Survive:
Some individuals will not survive to adulthood. They will get eaten, starve, or
die of disease.
4) Successful Reproduction:
The adults that are most suited to their environment will reproduce offspring
that are more likely to survive.
10. Darwin knew that there is great variation among organisms, but not how that variation
occurs. We now know that variation happens as a result of differences in genes. Some
genes make an organism more likely to survive to reproduce. The process called
selection happens only when organisms that carry these genes can survive to
reproduce. New fossil discoveries and new information about genes add to scientists’
understanding of natural selection and evolution.
SECTION 3: NATURAL SELECTION IN ACTION? (pg 180-183)
1.
Modern day evidence of natural selection in today’s world can be seen in bacteria
populations. A few bacteria survive antibiotic treatment because they have an
adaptation that makes them naturally resistant to, or not killed by, the antibiotic. The
surviving bacteria continue to reproduce, and pass the adaptation to their offspring.
After several generations, the population of bacteria is resistant to the antibiotic.
Changes in Populations
2. In 1930, about 1% of the male elephants in Uganda were born without tusks. Today, as
many as 15% of the elephants lack tusks. Read the section “Adaptation to Hunting” on
page 180. Explain why there are more elephants without tusks living in Uganda today.
Hunters killed elephants with tusks. This meant that the elephants most likely to
survive into adulthood and reproduce were the elephants without tusks. Therefore
the genes that were passed on were the tuskless genes, so now there are more
elephants without tusks.
3.
Read the section “Insecticide Resistance” on page 181. Explain how the insects build
up a resistance to pesticides and why it happens so quickly.
Insect populations change quickly because they have a short generation time.
The insects that are resistant to pesticides survive. When they reproduce, they
pass on the resistant gene to the new insects. Due to the short generation time,
a new population of insects appears very quickly.
4.
Generation time is the average time between one generation and the next. Insect
populations evolve quickly because they have a short generation time.
5.
Competition for mates can select for adaptations.
Forming a New Species
6. A species is a group of organisms that can mate with each other to produce fertile
offspring.
7.
8.
9.
When a group is separated from the original population, it forms a new population. The
formation of a new species as a result of evolution is called speciation. This occurs
when the new population and the original population differ so much they can no longer
mate successfully.
Speciation may happen in several ways. Explain 3 ways speciation may occur:
1) Separation:
Occurs when a part of a population separates from one another due to events
like canyon or mountain formation, a new lake, etc.
2) Adaptation:
After two groups have separated, natural selection acts on each group
differently, and the separated groups may evolve different sets of traits.
3) Division:
After many generations, the two separated groups have enough differences
they will no longer be able to successfully mate and are therefore considered
different species.
THINK ABOUT IT: Most kinds of cactus have leaves that grow in the form of spines.
The stems or trunks become thick, juicy pads or barrels that lock in lots of water.
Explain why each of these cactus parts might have evolved.
SAMPLE ANSWER: Cactuses evolved from plants that had adaptations to dry
conditions, such as spiny leaves that keep animals from eating the plant or thick
stems that store water. These were the features of plants that were most likely
to survive and reproduce, and therefore those successful traits were passed on.
DIRECTIONS: Read the paragraphs below. Highlight (or underline) at least 2 important
facts in each paragraph.
Gradualism is selection and variation that happens gradually. Over a short period of
time, it is almost impossible to notice any changes. Small variations occur that adapt an
organism slightly better to its environment. A few more individuals with more of the
helpful trait survive while organisms with the less helpful trait die. Very gradually, over a
long period of time, the population changes. Change is slow, constant, and consistent.
In punctuated equilibrium, change comes in spurts. There is a period of very little
change, and then one or a few huge changes occur, often through mutations in the genes of
a few individuals. Mutations are random changes in the DNA that are not inherited from
the previous generation but are passed on to generations that follow. Though mutations
are often harmful, the mutations that result in punctuated equilibrium are very helpful to
the individuals in their environments. Because these mutations are so different and so
helpful to the survival of those that have them, the proportion of individuals in the
population who have the mutation/trait and those who don't changes a lot over a very
short period of time. The species change very rapidly over a few generations, and then
settle down again to a period of little change.
Organisms adapt to their environment in a variety of ways, including mimicry (the
similarity in appearance of one species to another that protects one or both), camouflage,
speed, particular physical features, etc.
You are responsible for knowing the following definitions:
1. A habitat is the place an organism lives which provides food, shelter, and climate.
2. Niche is how something lives, eats, and survives in its ecosystem.
3. Mutations are an important source of new traits.
4. An organism can change over time through either gradualism or punctuated
equilibrium.