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Lesson 8: Adaptations (2.1.2)
BEHAVIOR, SURVIVAL AND REPRODUCTIVE SUCCESS
The earth is approximately 4.6 billion years old, with the first life appearing sometime around
3.6 - 3.8 billion years ago. The first life was prokaryotic cells, followed by eukaryotic cells
appearing around 1.8 – 2 billion years ago. Since organisms first appeared on earth, they have
had to develop ways to reproduce and survive within a constant changing environment.
Behavioral and structural adaptations have all helped in the survival and reproductive success
of organisms. An adaptation is a change in behavior, structure, or physiology in response to an
environmental change.
BEHAVIORAL ADAPTATIONS
As an environment changes, an organism often has to change as well in order to survive in the
new environment. Behavioral adaptation is the change in what organisms do or their actions
while carrying out some life processes in order to survive.
UNICELLULAR ORGANISMS
Response to internal and external stimuli by an organism is called behavior. Unicellular
organisms such as bacteria, amoeba, and paramecia have behaviors when they respond to light
and chemical signals. Photosynthetic bacteria, cyanobacteria, and protists move toward light to
ensure survival. Many can detect chemical signals given off by food sources. Some bacteria
even have magnetic crystals inside their bodies that direct their movements. These unicellular
organisms have also adapted mechanisms to avoid negative stimuli such as temperature and
chemical changes in their environments.
PLANT ADAPTATIONS
Plants respond to stimuli in a variety of ways to increase their chances for survival. Tropisms
are the growth of a plant in response to a stimulus. When plant hormones stimulate growth of
cells in one area of the stem and the plant bends toward a stimulus, it is a positive tropism.
When plants bend away from a stimulus, it is a negative tropism. Phototropism is the response
to light. Because plants need light in order to make their own food, the plants tissues will grow
in a variety of direction in order to get the best light possible. Because roots grow away from the
light, they are negatively phototropic.
Geotropism is a plant’s response to gravity. Roots grow toward the Earth in response to gravity
and are therefore positively geotropic. Stems and leaves grow upwards, against gravity, and are
negatively geotropic. Thigmotropism is the plants response to touch. Climbing plants such as
ivy, honeysuckle, or beans generally have weak stems and will wrap around another plant, wall,
fence or other structure for support. The tentacles of climbing plants respond to the touch of
something else and coil around the object.
Photoperiodism is the response of plant processes to the amount of daylight. Because the
amount of daylight in fall and winter is less than the amount of daylight in spring and summer,
photoperiodism explains why plants bloom in different seasons. Long day plants require at least
14 hours of daylight to bloom while short day plants require only 10 hours of daylight. Day
neutral plants flowering period is not affected by a photoperiod.
Table 8.1 Photoperiodism
Short-Day Plants
Long-Day Plants
Day-Neutral Plants
Flowers bloom in fall and winter. Includes
ragweed, goldenrod, and chrysanthemums.
Flowers bloom in spring and summer. Includes
spinach, clover and iris.
Flowers bloom over a range of photoperiods.
Examples include roses, tomatoes and beans.
Both plants and animals follow behavior cycles known as circadian rhythms. Circadian
rhythms are cycles that follow roughly a 24 hour pattern of activity.
Some plants fold their leaves and lowers during the night and open
them during the day in order to preserve water. Other plants have
adapted the ability to secrete nectars or pheromones (chemical scents or
perfumes) during times when pollinators are active to increase chances
of fertilization. Animals often exhibit sleep cycles when they are
awake and asleep at specific times of the day. Think back to a summer
vacation. Have you ever stayed up late every night and slept in the
next morning for a period of time? What did you notice for the first
week or so when you went back to school? You probably had a hard time waking up in the
morning; felt tired during the day, but had a difficult time going to bed early. Why? Your
circadian rhythm is on a different schedule than you.
ANIMAL ADAPTATONS
Animal behavior is broadly divided into three categories, innate, learned, and social behavior.
Behavior is influenced by hormones and by the nervous system. Hormones direct certain
behaviors, and the nervous system allows an animal to respond to stimuli. Behavioral
adaptations are used for survival and reproduction.
INNATE BEHAVIOR
Innate behaviors are those controlled by genetics and inherited like physical traits.
Territoriality, protective behaviors, courting behavior, hibernation, and migration are all
examples of innate behavior. When a baby sees a human face and smiles, or an alligator hatches
from its egg, innate behavior is being exhibited. Both reflexes and instinctive behaviors are
innate. Blinking is one of the simplest innate behaviors where as feeding young (suckling) is a
more complex innate behavior. Reflexes are uncontrollable reactions such as jerking your hand
back when you touch something hot. Many living organisms exhibit taxis, the movement in
response to a stimulus. For example, moths move toward light and worms move further into the
ground away from light (phototaxis). Bacteria and paramecia may move away from a toxic
chemical (chemotaxis).
Territoriality is a behavioral adaptation that ensures
enough space and resources for reproduction. Male
elephant seals battle each other for specific beach territories
during the breeding season. Large, strong males typically
have the largest territories, and the most females. When
female seals arrive, they remain on the beach within the
territory of a single male seal waiting for their turn to mate
with the male. Because not all elephant seal pups will
survive, fathering many offspring is one way males ensure
reproductive success.
Dogs and other canines such as wolves mark their territories
through urine. This is why when you walk a male dog, he
me urinate on every mailbox on that street. Cats will mark
territory by rubbing their bodies on tree to leave their scent.
Hormones activate specific forms of innate behavior such as
mating. Courtship is a behavior to help ensure beneficial
genes are passed on to the offspring. Some birds build
colorful or elaborate nests. Others sing mating calls, dance,
or display elaborate feathers, such as a peacock, to gain
potential mates. Male scorpions do elaborate dances for the females. Male lightening bugs
display bright lights to attract females. Frogs, alligators, and whales call for a mate with
elaborate songs. Most of the time, courtship behavior is exhibited by the male and females will
select the males with the best traits. The female will choose the scorpion that dances the best, the
bird with the most decorated and colorful nest, and the whale that is the best singer. The male is
able to pass on his genes to the offspring.
Hibernation is a period of dormancy during cold months. When
food supplies are limited, a bear, for example, will enter a period
of dormancy. The bear lives off its fat stores, while metabolism,
breathing, and body temperature drop to conserve energy. In hot
climates, some animals will go into a period of dormancy called
estivation. Frogs will bury themselves in the mud or soil during
a dry season or drought, and remain there until it rains. Some
animals move to new locations in response to a change in the
weather and decrease in available food. This behavior is called migration. Geese and monarch
butterflies migrate south for the winter where temperature is warmer and food is more abundant.
They generally follow the same pattern each year.
LEARNED BEHAVIOR
Learned behavior is behavior as a result of an animal’s repeated experiences. It allows animals
to adapt and increase chances of survival. Learned behaviors are related to life span and parental
care. Animals with short life spans and little or no parental care have fewer learned behaviors.
Table 8.2 summarizes the different types of learned behaviors.
Table 8.2 Types of Learned Behavior
Type of Learning
Description
A rapid form of learning that
Imprinting
occurs at a young age during a
critical period of development.
Habituation
Reasoning or Insight
Spatial or Latent
Classical Conditioning
Operant Conditioning (Trial
and Error)
An animal learns not to
respond to repeated stimulus
The ability to solve unfamiliar
problems in a new situation.
The ability of an animal to
create a mental map of its
environment.
An animal learns to associate
a stimulus with a response that
would not normally occur.
An animal learns to associate
an activity with a
consequence.
Example
When goslings hatch, what
they see first is what they
think is their mother. They
will follow this animal around.
Dogs stop barking at familiar
people entering the house
An octopus unscrews a jar to
get to food.
Blue jays know where they
have hidden food, even if food
is stored in up to one hundred
locations.
Pavlov’s dogs salivate at the
sound of a bell.
Toads flick their tongues at
flying insects, their food
source. If they are stung by a
bee, they learn to associate the
sting with insects that have
stripes, and they avoid them in
the future.
SOCIAL BEHAVIORS
Social behaviors are those processes
used by animals when communicating
between members of the same species.
Social behaviors can be seen among
many animals including horses, dogs,
whales, apes, birds, fish, and humans.
Members of an ape community will
often groom each other to remove
parasites and bond with one another.
Dogs will exhibit an aggressive posture
before a dog fight. You may have a
facebook or myspace page in which you talk to friends and keep up with their daily activities.
Some insects such as bees and ants communicate using pheromones. Pheromones are chemicals
released to warn others of danger or to share where a food supply was found. Killer bees, for
example, attack in a pack. If one bee is threatened, it releases a pheromone which causes the
entire swarm of bees to come and help with defense. An animal can be stung hundreds to
thousands of times by one pack of bees. When an ant finds a supply of food, it will head back to
the colony leaving a trail of pheromones behind him so that the worker ants can go directly to the
food source and bring it back to the colony. Social behaviors are often reinforced by leaders and
keep members of the same species bonded together. These behaviors can increase positive
relationships and their chances of survival.
DEFENSIVE MECHANISMS
Plants cannot flee from predators, but they do have spines, thorns, and leathery leaves to
discourage predators from consuming them. Some plants manufacture chemicals that are
poisonous or have a foul odor to keep animals away.
Tobacco and cacti are examples of plants with
obvious defense mechanisms. Tobacco releases
toxins that irritate the skin. Cacti have sharp needles
projecting outward, often in all different directions.
Animals also have adapted behaviors to protect them
from predators. Small birds flock together and
smaller fish stay is schools to make them appear
larger to a predator and increase chances for
survival. White tail deer, for example, signal to
other deer that danger is near by raising their white tail into the air. Bees release hormones to
signal danger. Some frogs are poisonous which discourages predators from hunting and eating
them.
REPRODUCTIVE ADAPTATIONS
Reproduction among organisms varies from asexual reproduction to sexual reproduction to
alteration of generations. In chapter 7, you learned the details of asexual and sexual
reproduction. In asexual reproduction, organisms create offspring that are an identical copy of
the parent. Asexual reproduction is advantageous to
organisms because it is fast and does not require as much
energy. However, if all the organisms, such as bacteria, are
the same, and cannot survive in a new and changing
environment, it could lead to extinction of that organism.
Bacteria have overcome this potential problem by developing
the ability to conjugate. Conjugation is the process in which
two bacteria swap DNA and increase their genetic variation.
By increasing the amount of variation within a species, the
species is more likely to be able to adapt to a changing
environment. In sexual reproduction, organisms create
offspring that are genetically diverse from the parents.
Organisms that do alteration of generations reproduce both
asexually and sexually, alternating the type of reproduction
between generations. Bacteria reproduce by binary fission, a
type of asexual reproduction.
Sexual reproduction is advantageous to survival of an organism because sexual reproduction
leads to an increase in genetic variation within a population allowing that population to better
adapt to a changing environment. Many organisms reproduce sexually such as insects, frogs,
dogs, sharks, fish, and humans.
Fungi, plants, and some protists, reproduce by alteration of generations. Alteration of
generations is advantages to an organism because they are able to reproduce both asexually
which is quick, and sexually which increases genetic variation. These organisms alternate
between asexual reproduction and sexual reproduction each generation.
There are a number of reproductive strategies that
organisms have developed to help ensure their survival
as a species. Some plants, called gymnosperms,
reproduce sexually using the wind as a method to
disperse sperm. Pine trees, for example, release pollen
into the wind and depend of this wind to carry the
pollen to another tree for reproduction. Angiosperms, a
type of flowering plant, depend on insects and animals
to pollinate and disperse seeds. When insects land on a
flower, pollen sticks to their feet and body. Insects
travel from flower to flower picking up pollen from one
and depositing it on another flower, fertilizing the plant. Seeds are made by angiosperms and
stored in fruits. When a bird eats berries, for example, the seeds pass through the digestive
system untouched and are dispersed by the bird around the forest in its waste. Angiosperms
depend on insects to pollinate and animals to disperse the seeds.
STRUCTURAL ADAPTATIONS
Plants have adapted a number of structures for their environment, depending on whether they
live in water or on land. Water dwelling plants must stay near the surface in order to catch
enough light for photosynthesis. They have air-filled sacs to help them float. Gases move in and
out of the plant through the process of diffusion.
Plants that live on land have adapted different
mechanisms for survival. Roots help keep a plant
sturdy in the ground, and are used to take up water and
nutrients from the soil. There are two types of roots,
fibrous and tap roots. In dry environments, plants
have fibrous roots which extend outward past the plant
base to increase surface area for water uptake.
Because dry environments gets little water, the plants
roots stay close to the ground surface in order to be
able to take up water as soon as rain falls near the
plant. In moist environments, plants have a tap root. Tap
roots extend deep into the ground keeping the plant sturdy in
the more unstable ground. Land plants must overcome
gravity as they grow upward against gravity. Plants do not
have a skeletal system; instead they have cellulose.
Cellulose, found in the cell walls of plant cells provides
structure and support. Because land plants are not
continuously surrounded by water, they must find a way to
limit the amount of water that evaporates from their cells. A
waxy cuticle on the top side of the leaves helps limit
transpiration, evaporation of water from the leaves. Gases
enter and leave plant cells through a small opening on the
underside of the leaf, called the stomata. The stomata are surrounded by guard cells which
control when the stomata are open to allow gas exchange, or closed to prevent it. When it is
windy, the guard cells close the stomata slightly to help preserve water.
Physical adaptations help animals survive in their
environment. Many species that live in cold
climates grow thick fur during the winter months
and shed this fur during the summer. Polar bears
develop thick layers of fat in the winter, and loose it
during the summer. Animals that live in cold
climates tend to have short limbs, ears and tails.
These shorter extremities reduce heat loss from the
animal’s body. Animals that live in dry deserts,
such as camels, giraffes, and African deer can
survive for long period of time without water.
Camels have a hump which stores water. Some desert frogs have special adaptations that allow
them to absorb water directly from the air. Other frogs can change skin color to a pale white in
order to reflect heat during the hottest part of the day. Animals that live in hot climates typically
have large, long extremities, which allow them to cool off.
Animals can also adapt in response to predator/pre relationships. Porcupines and spiny anteaters
grow sharp quills for protection against predators. Turtles retreat inside a bony shell for
protection. Some animals produce venom or
poison for hunting and protection. The
American alligator has eyes and nostrils located
on the top of its head allowing the body of the
animal to remain hidden. Cottonmouth snakes
and other pit vipers have special heat-sensing
organs, located on the front of their head which
they use to find their prey.
Most land-dwelling predators have eyes located
close together on the front of the head. This
allows the predator to focus specifically on its
prey. Most prey have eyes located far apart of either side of the head. This allows them to see
more of the area around them, perhaps helping them to better spot a predator and escape.
Mimicry is when an animal looks like a different
animal that has a defense mechanism such as thorns or
being poisonous. A coral snake is brightly colored
with red, yellow, and black strips. This bright color
warns predators that the coral snake is poisonous and
helps protect it from predation. The scarlet king snake
also has red, yellow, and black strips, however it is not
poisonous. The scarlet king snake mimics the coral
snake in an effort to trick predators into thinking the
king snake is also poisonous. Side by side, it is difficult to tell which one is the coral snake and
which one is the king snake.
FEEDING ADAPTATIONS
The way an organism feeds often correlates to the type of food that
is eaten. For example, animals which eat only plants have large,
thick, flat incisors which are able to easily cut grass and leaves.
These herbivores also have longer digestive tubes filled with
bacteria to help breakdown and digest plants. Their bodies are
also adapted to allow them to bend over when collecting plants.
Organisms that eat meat (carnivores) have large canine teeth and
molars for tearing and grinding meat. Some carnivores also have
sharp claws and strong jaws used in capturing prey. An example
would be a tiger, bear, or crocodile. Additionally, animals such as
snakes, can unhinge their jaws in order to eat organisms bigger
than themselves.
Plants have several adaptations to allow photosynthesis to occur more efficiently. In areas where
there is not an extreme range in temperature and precipitation (temperate climates), plants have
broad leaves. Broad leaves help to increase the surface area to which light can be absorbed and
photosynthesis may occur. Pines have needles and sunken stomata that conserve water. Plants
that live in areas with nitrogen poor soil have adapted other ways of getting nitrogen. The Venus
flytrap is able to capture small insects through the process of thigmotropism (leaves close around
insect in response to touch).
Lesson 8 Review: Adaptations
A. Define the following terms.
behavioral adaptation
behavior
negative tropism
phototropism
photoperiodism
circadian rhythm
instinctive behavior
taxis
hibernation
dormancy
learned behavior
social behavior
sexual reproduction
conjugation
roots
cellulose
guard cell
physical adaptation
tropism
positive tropism
geotropism
thigmotropism
innate behavior
reflex
territoriality
courtship
estivation
migration
pheromones
asexual reproduction
alternation of generations
waxy cuticle
stomata
structural adaptation mimicry
B. Choose the best answer.
1. What is the connection between a flower blooming and the amount of daylight
A. If daylight persists for 14 hours, certain plants will bloom.
B. The amount of daylight does not determine if certain plants bloom
C. If daylight persists for 10 hours, certain flowers will bloom
D. Above choices are true for tobacco, corn and a Christmas cactus respectively
2. Which is a response based on a 24 hour period such as a rooster crowing or a day lily
flowering?
A. photoperiod
C. circadian rhythm
B. phototropism
D. geotropism
3. Milkweed, tobacco and peyote have adapted which type of measures to protect themselves?
A. behavioral
C. chemical
B. physical
D. territorial
4. Why is it beneficial for some insects to be able to blend in with their surroundings?
A. it protects them from predators
B. it allows them to regulate body temperature
C. it helps them find a mate
D. it protects their territory
5. You may have noticed when you are walking a male dog that he likes to “mark his territory”
on every mailbox post in the neighborhood. What chemical can be found in his urine that
communicates to other dogs “This is my mailbox post!”
A. toxins
C. pheromones
B. water
D. cellulose
6. What adaptations had to occur in order for aquatic plants to successfully move onto land?
A. cellulose
B. waxy cuticle
C. roots
D. all of the above
7. How is alternation of generations advantageous to reproducing organisms?
A. organisms are able to reproduce sexually to increase genetic variation
B. organisms are able to reproduce asexually, which is quick
C. both A and B are correct
D. alternation of generations has no advantages
8. A teenager cheats on a test, and gets in trouble for it when he gets home from school. He
never cheats again. This is an example of what type of behavior?
A. learned
C. courtship
B. hibernation
D. migration
9. The area in which a lion pride lives is marked off through urine, and also upheld through
intimidation by roaring. This is an example of which type of behavior?
A. learned
C. estivation
B. territoriality
D. dormancy
10. Sharp needles on a plant stem, or the production of toxic chemicals is an example of what
type of adaptation?
A. innate
C. reproduction
B. social
D. defense
C. Complete the following exercises
1. Name two adaptations plants have developed to disperse their seeds.
2. What are some reasons that animals emit sounds?