Download REVIEW 6 Adaptations to the Environment Some animals, such as

REVIEW 6
Adaptations to the Environment
Some animals, such as chameleons and octopuses, can change the color of their skin. This
ability is good for camouflage, or blending into the surroundings. Animals with the ability
to change the color of their skin often use it to avoid predators and (if they kill and eat
other animals) to surprise their prey.
The ability to change skin color is one example of an adaptation. An adaptation is any trait
that helps the individuals of a species survive within an environment. In this review, we
will look at some common adaptations that help animals and plants survive in their
environments.
The ability to change skin color is useful for more than just camouflage. Describe one other
reason why an animal such as a chameleon or octopus might change skin color.
Words to Know
adaptation
angiosperm
camouflage
dormancy
evolution
gymnosperm
hibernation
homeostasis
migration
natural
selection
ovule
pollen
pollination
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Homeostasis
When you think of an organism interacting with its environment, you might first think of the
external environment—the air, water, and/or land in which the organism lives. But an
organism must also respond to changes inside itself, called its internal environment. In
general, organisms must keep their internal environments fairly stable. Take the human
body as an example. The human body works best when its temperature is around 37° C. If
a human body gets too warm, it releases some of that heat by sweating. If a human body
gets too cold, it produces more heat for itself by shivering. The ability to maintain a
constant internal environment is called homeostasis. (Homeo- means "steady" and stasis
means "state.")
Name two other internal conditions to which your body responds.
Different animals maintain homeostasis in different ways. Again, consider an animal's internal
temperature. Mammals have bodies that automatically maintain their internal temperatures.
For this reason, they are called warm-blooded animals. Other animals, such as reptiles,
maintain their internal temperatures through behavior. If a lizard gets too warm, for
example, it will go into the shade to cool off. If a lizard gets too cold, it will bask in the
sun. Animals that maintain their body temperatures through behaviors are called coldblooded animals.
Explain why mammals are found in polar regions but reptiles are not.
Responses to seasonal change
Of course, organisms must also respond to changes in their external environments, or the places
in which they live. Many places on the Earth have seasons—months of rainy weather
followed by months of dry weather, or months of cold temperatures followed by months of
warm temperatures. Seasonal changes usually affect the amount of food available in an
environment. Organisms have evolved different behavioral responses to the changing
availability of food in their environments.
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Hibernation is a condition in which an animal remains in a sleep-like state for weeks, months,
or even years. Black bears, for example, fatten themselves up during the summer months
when food is plentiful. During winter, they hibernate and slowly use up the food energy
stored in their fat. Some insects and reptiles also hibernate when temperatures are low and
food and water are scarce.
Migration is another behavior for dealing with limited food availability. Birds, for example,
rely on insects, nectar, and seeds for food. Because flowers and insects are not easy to find
during cold or dry months, many species of bird migrate to areas where they can find such
food. Some animals also migrate to special places for the purpose of mating and giving
birth to their offspring.
Explain why most animals in Arizona do not hibernate during the winter months.
Are there circumstances when animals native to Arizona will enter a hibernation-like state?
Explain your answer.
Plant adaptations
Most plants produce seeds. Seeds contain a plant embryo called a seedling. Warm, moist soil
conditions help a seedling to grow and break out of the seed. Nutrients stored in the seed
nourish the seedling until its leaves are large enough to begin photosynthesis. It may seem
that a seed is similar to a bird egg about to hatch. However, baby birds must hatch when
they grow too large for their egg, while seeds can lay dormant and not grow for many
years. In deserts such as Death Valley, seeds wait in the soil for many years until a rare
rain shower stimulates them to begin growing.
Plant species develop seeds in different ways. Gymnosperms are plants that do not use flowers
to produce seeds. A pine tree, which is a type of gymnosperm, uses pinecones to
reproduce. A single pine tree makes both male and female pinecones.
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Male pinecones produce pollen (male sex cells), and female pinecones produce ovules (female
sex cells). You have probably noticed female pinecones because they are large. The
smaller male pinecones are easier to overlook.
For a seed to develop, pollen must come in contact with an ovule. Gymnosperms use the wind
to blow large amounts of pollen from the male pinecones to the ovules of female
pinecones. The movement of pollen is called pollination. Once pollen comes into contact
with an ovule, a seed can develop. After a time, the female pinecones open and release
their seeds. Either the wind or animals then move the seeds to the new locations where
they may grow into new pine trees.
"The sidewalks are covered by pollen from those pine trees, and the pollen is really
bothering my allergies," said Tom. "Why do those trees have to be so messy?" How would
you answer Tom's question?
Angiosperms are plants that use flowers to produce seeds. Many angiosperms have both male
and female parts in the same flower. The male parts of the flower produce pollen; the
female parts of the flower produce ovules. Pollen must reach an ovule so that seed
development may begin. Flowers often use animals such as birds and insects to help them
move pollen from one flower to another. Flowers use their colors, smells, and a sugar
substance called nectar to attract animal pollinators. In most cases, pollinators move from
flower to flower looking for a snack of nectar. Moving from plant to plant, pollinators
carry the pollen from one flower to the flower of another. For example, bumblebees
moving in and out of flowers are often covered in yellow plant pollen.
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Why do angiosperms make less pollen than gymnosperms?
Once a flowering plant is pollinated and produces seeds, these seeds must be dispersed to a
place that they can grow. Plants will usually produce seeds that are adapted to the type of
environment in which they live. Plants that live in windy environments are likely to
produce seeds with wings that are easily carried by the wind. Plants that live in wet, rainy
environments are more likely to develop hard, water-resistant seeds that can be carried but
not destroyed by water.
Based on their structures, how are the following seeds most likely dispersed? Explain your
answer.
The flowers of angiosperms develop into fruit once the seeds are mature. Either an animal eats
the fruit and moves the seeds away from the parent plant, or the fruit opens and the seeds
are moved away by wind and rain. If the seeds end up in a good location, they may
develop into new plants. Apples, green peppers, and blueberries are examples of
angiosperm fruit.
Eating an apple before it is ripe can give a person a stomachache. Why wouldn't the tree
"want" you to eat an unripe apple?
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Adaptations and evolution
Offspring that inherit a helpful adaptation have a better chance of surviving than offspring that
do not inherit the trait. This process is called natural selection. Over many generations,
helpful traits may become more common within a population, and unhelpful or harmful
traits may become less common. When the traits of an entire population change over
several generations, such change is called evolution.
A famous example of evolution through natural selection is Darwin's finches. (A finch is a type
of bird.) In the 1830s, Charles Darwin traveled to the Galapagos Islands, a group of islands
about 700 km off the eastern coast of South America. Traveling from island to island,
Darwin discovered 13 species of finches. Each species was adapted to particular ways of
eating. For example, the species named the warbler finch ate only insects; the species
named the vegetarian tree finch ate only plants. Other species of finch had different eating
habits.
Darwin asked himself: Why were there so many species of finch on the Galapagos Islands? He
reasoned that, millions of years ago, a single finch species had traveled to the islands and
stayed there. The individuals in that population competed with each other for food in many
different types of environments. Some islands had many insects, and other islands had
many plants. Some islands had trees that produced many nuts, and other islands had plants
that produced seeds and fruits.
All species have a natural amount of variation among their members. Therefore, the
finches in the original population were not identical. The finches had beaks of different
lengths, strengths, and so on.
Describe a beak that would be good for breaking open hard nuts.
Describe a beak that would be good for digging insects out of cracks in rocks.
Darwin reasoned that some birds within the original finch population had more success in some
environments than in others. The finches with the strongest beaks could break open and eat
hard seeds. Those finches outcompeted other finches on an island where hard seeds were
the main food source. The finches with the longest beaks could catch and eat insects.
Those finches outcompeted other finches on an island where insects were the main food
source. Over several generations, the population of finches on a seed island came to have
strong beaks, and a population of finches on an insect island came to have long beaks.
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People in Science
Charles Darwin studied plant and animal life. He is famous for coming up with the idea that all
animals, including humans, developed from life-forms that lived millions of years ago. We
call his idea the theory of evolution. Darwin spent five years on a boat at sea working on
his ideas. He was very unhappy; he was seasick all the time. When his trip ended, Darwin
decided he would never travel again. He married, had 10 children, and took only short
vacations within Great Britain. He did all his scientific study at home, using the
information and materials he had collected during his sea voyage. He built a big house
with a large study and designed a special microscope. For the first eight years, he studied
only barnacles. When his children were young, they thought all fathers worked at home
and studied barnacles. Later in life, he decided to study earthworms. For a while, he even
kept live worms on top of the piano. He liked to watch the worms' activity when the piano
was played. Darwin published many books about his research. His most famous book is
On the Origin of Species, which explains his theory of evolution.
Charles Darwin
(1809-1882)
Keys to Keep
 An adaptation is a trait that increases the chances that an organism will survive and
reproduce.
 Homeostasis describes how animals and plants keep their internal conditions constant.
Gymnosperms are plants that make seeds without using flowers.
 Angiosperms are plants that use flowers and pollinators to make seeds.
 Evolution is the change in the traits of a population of a species over many generations.
 Charles Darwin developed the theory of evolution based on years of observation.
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Explore It Yourself
In this activity, you will explore how an organism's trait—in this case, its coloring—can aid or
hinder the organism's survival within an environment. You will also investigate how a
natural pressure—in this case, predators—can increase or decrease the frequency of a trait
within a population over several generations. In other words, you are going to simulate
how natural selection causes evolution within a species.
Your teacher will put you in groups of three or four. Each group gets a tub with a layer of black
aquarium gravel at the bottom. Laying on the gravel are 50 white beans and 50 black
beans. Each group also needs a stopwatch.
Step 1: Pick two students to be hungry birds and one student to be the timer. Beans represent
the prey.
Step 2: When the timer says "go," the hungry birds have 30 seconds to capture their prey. The
hungry birds should pick out their prey as quickly as possible, one bean at a time, and
then put beans outside the tub.
Step 3: After 30 seconds, the timer says "stop." The hungry birds are full. Step 4: Count the
number of white and black beans remaining in the tub.
Surviving black beans:
Surviving white beans:
Step 5: Suppose that each surviving individual produces two offspring of its own color, then
dies. The population that remains is generation 2.
How many black beans would be in generation 2?
How many white beans would be in generation 2?
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What Does It Mean?
1. Which color provided better camouflage against the birds? How do you know?
2. Suppose that the birds eat the organisms and the survivors keep reproducing several more
times. Over several generations, what change will occur in the coloration of the
population? Explain why this change takes place.
3. Suppose that, after several generations, you introduce some simulated pollution to the
environment by painting the gravel white. What will happen to the overall coloration of the
population after several more generations?
4. Some people think that evolution involves individual plants or animals somehow "choosing"
to adapt to a change in the environment. Use this simulation to explain why that
understanding of evolution is incorrect.
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AIMS Science Practice
1 When an animal sweats to keep cool, which of the following processes is the animal
exhibiting?
A evolution
B hibernation
C homeostasis
D migration
2 The following pictures show the talons of four different types of bird. Which bird has the
best talon structure for walking on muddy ground?
A W
B X
C Y
D Z
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3 When the seeds of an angiosperm are mature, what do the flowers develop into?
A pollen
B ovules
C leaves
D fruit
4 Maple trees use the specialized structure below to transport their seeds. How are the seeds
transported?
A by animals
B by wind
C by water
D by erosion
5 A certain species of plant produces seeds without the use of flowers. What type of plant is
this?
A a gymnosperm
B an angiosperm
C a pollinator
D a stamen
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6 Suppose two populations of a single species of squirrel are put in different environments for
hundreds of generations. What will most likely happen to the two populations?
A Both populations will become extinct.
B Both populations will develop new sets of traits.
C Both populations will develop larger muscles.
D Both populations will become carnivorous.
7 In which population of organisms could scientists most likely observe direct evidence of
evolutionary change?
A blue whales
B elephants
C fruit flies
D oak trees
8 What characteristic of a population of organisms would most likely be subject to
evolutionary change within 10 generations?
A protective coloration
B type of skeleton
C reproductive strategy
D respiratory organs
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