Transcript 28–3 Insects

Biology
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28–3 Insects
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28–3 Insects
Insects
Class Insecta contains more species than any other
group of animals.
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28–3 Insects
What Is an Insect?
What are the distinguishing features of
insects?
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28–3 Insects
What Is an Insect?
What Is an Insect?
Insects have a body divided into three
parts—head, thorax, and abdomen. Three
pairs of legs are attached to the thorax.
Head
Thorax
Abdomen
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28–3 Insects
What Is an Insect?
Insects have a segmented body, an exoskeleton, and
jointed appendages.
A typical insect also has:
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a pair of antennae
a pair of compound eyes
two pairs of wings on the thorax
tracheal tubes that are used for respiration
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28–3 Insects
What Is an Insect?
Responses to Stimuli
Compound eyes made up of many lenses detect
minute changes in color and movement.
The brain assembles information from the eye and
directs the insect’s response.
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28–3 Insects
What Is an Insect?
Insects have chemical receptors for taste and smell
on their mouthparts, antennae, and legs.
Insects have sensory hairs that detect movements in
the surrounding air or water.
Many insects also have well-developed ears.
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28–3 Insects
What Is an Insect?
Adaptations for Feeding
Insects have three pairs of appendages that are
used as mouthparts, including a pair of mandibles.
Insect mouthparts are specialized for feeding.
Many insects produce saliva containing digestive
enzymes that help break down food.
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28–3 Insects
What Is an Insect?
Specialized Mouthparts
Mandibles used to
saw and grind food
Ant
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28–3 Insects
What Is an Insect?
Specialized Mouthparts
Tubelike mouthpart
used to suck nectar
Moth
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28–3 Insects
What Is an Insect?
Specialized Mouthparts
Spongelike mouthpart
used to lap up food
Fly
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28–3 Insects
What Is an Insect?
Movement and Flight
Insects have three pairs of legs, which are used for
walking, jumping, or capturing and holding prey.
The legs of many insects have spines and hooks
that are used for grasping and defense.
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28–3 Insects
What Is an Insect?
Flying insects typically have two pairs of wings made
of chitin.
Flight has allowed insects to disperse long distances
and to colonize a wide variety of habitats.
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28–3 Insects
What Is an Insect?
What two types of development can
insects undergo?
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28–3 Insects
What Is an Insect?
Metamorphosis
The growth and development of insects
usually involve metamorphosis, which is
a process of changing shape and form.
Insects undergo either incomplete
metamorphosis or complete metamorphosis.
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28–3 Insects
What Is an Insect?
Immature insects that undergo incomplete
metamorphosis look very much like the adults.
These immature forms are called nymphs.
Nymphs lack functional sexual organs and other adult
structures, such as wings.
Nymphs gradually acquire adult structures as they
molt and grow.
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28–3 Insects
What Is an Insect?
Adult
Adult
Eggs
Incomplete
Metamorphosis
Nymph
Nymph
Nymph
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28–3 Insects
What Is an Insect?
In complete metamorphosis, animals hatch into
larvae that look and act nothing like their parents.
They feed and grow rapidly and molt a few times.
They undergo a final molt and change into a pupa—
the stage in which an insect changes from larva to
adult.
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28–3 Insects
What Is an Insect?
pupa
Adult
Eggs
Complete
metamorphosis
Adult
Larva
Larva
Pupa
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28–3 Insects
Insects and Humans
Insects and Humans
Many insects are known for their negative effects.
Termites destroy wood structures.
Desert locusts cause billions of dollars in damage
to livestock and crops.
Mosquitoes can infect humans with
microorganisms that cause disease.
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28–3 Insects
Insects and Humans
Insects also contribute to the richness of human life.
One third of the food you eat depends on plants
pollinated by animals and insects.
Insects produce silk, wax, and honey.
They are considered a food delicacy in certain
countries of Africa and Asia.
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28–3 Insects
Insect Communication
Insect Communication
Insects communicate using sound, visual,
chemical, and other types of signals.
Much of their communication involves finding a
mate.
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28–3 Insects
Insect Communication
Visual Cues
Male fireflies use visual cues to communicate with
potential mates.
A light-producing organ in the abdomen is used to
produce a distinct series of flashes.
When female fireflies see the signal, they flash
back a signal of their own, inducing the males to fly
to them.
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28–3 Insects
Insect Communication
Chemical Signals
Many insects communicate using chemical signals.
The chemicals are called pheromones.
Pheromones are specific chemical messengers
that affect the behavior or development of other
individuals of the same species.
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28–3 Insects
Insect Communication
Some pheromones function to signal alarm or alert
other insects to the death of a member of the colony.
Other pheromones enable males and females to
communicate during courtship and mating.
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28–3 Insects
Insect Societies
What types of insects form societies?
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28–3 Insects
Insect Societies
Insect Societies
Ants, bees, termites, and some of their
relatives form complex associations
called societies.
A society is a group of closely related
animals of the same species that work
together for the benefit of the whole group.
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28–3 Insects
Insect Societies
Castes
Within an insect society, individuals may be
specialized to perform particular tasks, or roles.
These are performed by groups of individuals
called castes.
Each caste has a body form specialized for its role.
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28–3 Insects
Insect Societies
The basic castes are:
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reproductive females (queens)
reproductive males
workers
Most insect societies have only one queen.
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28–3 Insects
Insect Societies
A tropical leaf-cutter ant colony is one example of an
insect society.
Individuals in the colony have specific tasks or roles.
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28–3 Insects
Insect Societies
Major workers gather leaf
tissue to use as a food
source for fungus. The
fungus provides food for
the colony.
Smaller worker ants ride
atop the leaf, keeping
alert for potential threats.
Major Workers
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28–3 Insects
Insect Societies
The queen’s sole purpose
is to lay eggs.
Most of the eggs become
worker ants.
Females that will become
queens leave the nest to
start a new colony.
Queen
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28–3 Insects
Insect Societies
Minor worker
ants chop the
leaves into a fine
paste, tend to the
gardens, and
harvest fungus
for other
members of the
colony.
Minor Workers
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28–3 Insects
Insect Societies
Soldier ants guard
the nest from
potential attackers.
Soldiers
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28–3 Insects
Insect Societies
Communication in Societies
Each species of social insect use visual, touch,
sound, and chemical signals to communicate
information among members of the colony.
Honeybees communicate information about food
through a series of complex movements.
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28–3 Insects
Insect Societies
The round dance
indicates that food
is fairly close to
the hive.
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28–3 Insects
Insect Societies
The waggle
dance
indicates that
food is farther
away from the
hive. It also
indicates the
direction of the
food.
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28–3
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28–3
How many body parts do insects have?
a. two
b. three
c. four
d. five
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28–3
Which group contains the most species?
a. vertebrates
b. nonvertebrate invertebrates
c. noninsect arthropods
d. insects
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28–3
Characteristics shared by typical insects include
a. six walking legs and one pair of wings.
b. six walking legs and two pairs of wings.
c. eight walking legs and one pair of wings.
d. eight walking legs and two pairs of wings.
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28–3
The immature form of an insect that undergoes
incomplete metamorphosis is called a(n)
a. larva.
b. nymph.
c. pupa.
d. embryo.
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28–3
Which of the following species form complex
societies?
a. butterflies
b. ants
c. locusts
d. flies
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