Chapter 15: Respiration
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
The respiratory tract
The Respiratory Tract
• Air is cleansed, warmed, and moistened as it
passes the cilia and mucus in the nostrils and
nasal cavity.
• In the nose, the hairs and the cilia act as a
screening device.
• In the trachea, the cilia beat upward, carrying
dust and mucus into the pharynx.
• Exhaled air carries out heat and moisture.
The path of air
The Nose
• The two nasal cavities are divided by a septum.
• They contain olfactory cells, receive tear ducts
from eyes, and communicate with sinuses.
• The nasal cavities empty into the nasopharynx.
• Auditory tubes lead from the middle ears to the
nasopharynx.
The Pharynx
• The pharynx (throat) is a passageway from the
nasal cavities to oral cavities and to the larynx.
• The pharynx contains the tonsils; the
respiratory tract assists the immune system in
maintaining homeostasis.
• The pharynx takes air from the nose to the
larynx and takes food from the oral cavity to the
esophagus.
The Larynx
• The larynx is a cartilaginous structure lying
between the pharynx and the trachea.
• The larynx houses the vocal cords.
• A flap of tissue called the epiglottis covers the
glottis, an opening to the larynx.
• In young men, rapid growth of the larynx and
vocal cords changes the voice.
Placement of the vocal cords
The Trachea
• The trachea, supported by C-shaped
cartilaginous rings, is lined by ciliated cells,
which sweep impurities up toward the pharynx.
• Smoking destroys the cilia.
• The trachea takes air to the bronchial tree.
• Blockage of the trachea requires an operation
called a tracheostomy to form an opening.
Cilia in the trachea
The Bronchial Tree
• The trachea divides into right and left primary
bronchi which lead into the right and left lungs.
• The right and left primary bronchi divide into
ever smaller bronchioles to conduct air to the
alveoli.
• An asthma attack occurs when smooth muscles
in the bronchioles constrict and cause
wheezing.
The Bronchial Tree
The Lungs
• Lungs are paired, cone-shaped organs.
• Lungs are functionally composed of tiny airsacs called aveoli
• The right lung has three lobes, and the left lung
has two lobes, allowing for the space occupied
by the heart.
• The lungs are bounded by the ribs and
diaphragm.
The Alveoli
• Alveoli are the tiny air sacs of the lungs made
up of squamous epithelium and surrounded by
blood capillaries.
• Alveoli function in gas exchange, oxygen
diffusing into the bloodstream and carbon
dioxide diffusing out.
• Infant respiratory distress syndrome occurs in
premature infants where underdeveloped lungs
lack surfactant (thin film of lipoprotein) and
collapse.
Gas exchange in the lungs
Inspiration and Expiration
• There is a continuous column of air from the
pharynx to the alveoli, and the lungs lie within
the sealed-off thoracic cavity.
• The thoracic cavity is bounded by the rib cage
and diaphragm.
Inspiration
• When we inhale (inspiration) the rib cage rises
and the diaphragm lowers, causing the thoracic
cavity to expand.
• The negative pressure or partial vacuum in the
alveoli causes the air to come in.
Control of breathing
Inspiration/Expiration
Expiration
• When we exhale (expiration), the rib cage
lowers and diaphragm to resume dome shape.
• Expiration is passive, while inspiration is
active.
Internal Respiration
• Internal respiration is the diffusion of O2 from systemic
capillaries into tissues and CO2 from tissue fluid into
systemic capillaries through hemoglobin in Red Blood
Cells.
• Oxyhemoglobin gives up O2, which diffuses out of the
blood and into the tissues because the level of O2 in
tissues is lower than that of the blood.
• CO2 diffuses from tissue cells into the blood, it enters
red blood cells where a small amount is taken up by
hemoglobin
Internal Respiration
• All this “internal respiration” occurs at the
capillaries (single-cell thickness allows for
complete diffusion)
• Blood leaving capillaries (which become
“venules” and then “veins” is a dark maroon
color because red blood cells contain reduced
hemoglobin.
External and internal respiration
External and internal respiration
Sites of upper respiratory infections
Sinusitis
• Sinusitis is infection of the cranial sinuses
within the facial skeleton that drain into nasal
cavities.
• It occurs when nasal congestion blocks the
sinus openings and is relieved when drainage is
restored.
• Pain and tenderness over the lower forehead
and cheeks, and toothache, accompany this
condition.
Otitis Media
• Otitis media is bacterial infection of the middle
ear.
• Children suffer when a nasal infection spreads
to the middle ear by way of the auditory tube
and antibiotics are usually used to clear the
infection.
• Sometimes drainage tubes (called
tympanostomy tubes) are inserted into the
eardrums of children with recurrent infections.
•
• Tonsillitis
• Tonsillitis is infection of tonsils and recurrent
infections that make breathing or swallowing
difficult may be relieved by a tonsillectomy.
• Laryngitis
• Laryngitis is an infection of the larynx and usually
results in a loss of voice.
• Persistent hoarseness is a warning sign of
cancer.
Lower Respiratory Tract Disorders
• Lower respiratory infections include:
1) acute bronchitis, an infection of primary and
secondary bronchi;
2) pneumonia involving a bacterial or viral
infection of the lungs; and
3) pulmonary tuberculosis (infection caused by
tubercle bacillus).
Restrictive Pulmonary Disorders
• In restrictive pulmonary disorders, vital capacity
is reduced because the lungs have lost their
elasticity due to inhaled particles such as silica,
coal dust, or asbestos.
• Fibrous connective tissue builds in the lungs in
pulmonary fibrosis, caused by exposure to
inhaled particles, including those of fiberglass.
Obstructive Pulmonary Disorders
• In obstructive pulmonary disorders, air does not
flow freely in the airways, and inhalation and
exhalation are difficult.
• Chronic bronchitis with inflamed airways,
emphysema where alveolar walls break down,
and asthma with constricted bronchioles
obstruct the airways and tend to get
progressively worse or recur.
Lower respiratory tract disorders
Lung Cancer
• Lung cancer follows this sequence of events:
thickening of airway cells, loss of cilia on the
lining, cells with atypical nuclei, tumor
development, and finally metastasis.
• Removal of a lobe or lung, called
pneumonectomy, may remove the cancer.
• Smoking, whether active or passive, is a major
cause of lung cancer.
Normal lung versus cancerous lung
• During inspiration, the pressure in the lungs
decreases and air comes rushing in; during
expiration, increased pressure in the thoracic
cavity causes air to leave the lungs.
• External respiration occurs in the lungs where
oxygen diffuses into the blood and carbon
dioxide diffuses out of the blood.
• Internal respiration occurs in the tissues where
oxygen diffuses out of the blood into tissue cells
and carbon dioxide diffuses into the blood.
• The respiratory pigment hemoglobin transports
oxygen from the lungs to the tissues and aids in
the transport of carbon dioxide from the tissues
to the lungs.
• The respiratory tract is especially subject to
disease because it is exposed to infectious
agents; also, cigarette smoking contributes to
two major lung disorders—emphysema and
cancer.
Chapter 17: Nervous System
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Nervous Tissue
• The nervous system is divided into a
central nervous system (CNS), consisting
of the brain and spinal cord, and a
peripheral nervous system (PNS),
consisting of nerves carrying sensory and
motor information between the CNS and
muscles and glands.
• Both systems have two types of cells:
neurons that transmit impulses.
Organization of the nervous system
Neuron Structure
• Neurons are composed of dendrites that receive
signals, a cell body with a nucleus, and an axon
that conducts a nerve impulse away.
• Sensory neurons take information from sensory
receptors to the CNS.
• Interneurons occur within the CNS and integrate
input.
• Motor neurons take information from the CNS to
muscles or glands.
Types of neurons
Myelin Sheath
• Long axons are covered by a protective myelin
sheath formed by another type of cell. This
sheath acts like insulation on a wire, increasing
the speed of transmission.
• The sheath contains lipid myelin which gives
nerve fibers their white, glistening appearance.
• Multiple sclerosis is a disease of the myelin
sheath.
Myelin sheath
The Nerve Impulse
• The nervous system uses the nerve impulse to
convey information.
• The nature of a nerve impulse has been studied
by using excised axons and a voltmeter.
• Voltage (in millivolts, mV) measures the
electrical potential difference between the inside
and outside of the axon.
Resting Potential
• When an axon is not conducting a nerve
impulse, the inside of an axon is negative (65mV) compared to the outside; this is the
resting potential.
• A sodium-potassium pump in the membrane
actively transports Na+ out of the axon and
K+ into the axon to establish resting
potential.
• The membrane is more permeable to K+ and
much of the resting potential is due to the
excess of K+ outside of the neuron.
Resting potential
Action Potential
• An action potential is a rapid change in
polarity as the nerve impulse occurs.
• The action potential occurs if a stimulus
causes the membrane to depolarize past
threshold.
• An intense stimulus causes many firings
(reaching action potential) in an axon; a
weak stimulus may cause only a few.
• The action potential requires two types of
gated channel proteins: one each for Na+
and K+.
• Sodium Gates Open
• The gates of sodium channels open first
and Na+ flows into the axon.
• The membrane potential depolarizes to
+40 MV.
• Potassium Gates Open
• The gates of potassium channels open
next and K+ flows to the outside of the
axon.
• The membrane potential repolarizes to
65 MV.
–
Action potential
Propagation of an Action Potential
• The action potential travels the length of an
axon, with each portion of the axon
undergoing depolarization then repolarization.
• A refractory period ensures that the action
potential will not move backwards.
• In myelinated fibers, the action potential only
occurs at the nodes of Ranvier.
• This “jumping” from node-to-node is called
saltatory conduction.
Transmission Across a Synapse
• The tip of an axon forms an axon bulb that
is close to a dendrite or cell body of another
neuron; this region of close proximity is
called the synapse.
• Transmission of a nerve impulse takes
place when a neurotransmitter molecule
stored in synaptic vesicles in the axon bulb
is released into a synaptic cleft between the
axon and the receiving neuron.
• When a nerve impulse reaches an axon
bulb, gated channels for calcium open and
Ca2+ flow into the bulb.
• This sudden rise in Ca2+ causes synaptic
vesicles to move and merge with the
presynaptic membrane, releasing their
neurotransmitter molecules into the cleft.
• The binding of the neurotransmitter to
receptors in the postsynaptic membrane
causes either excitation or inhibition.
Synapse structure and function
Synaptic Integration
• Many synapses per single neuron is not
uncommon.
• Excitatory signals have a depolarizing
effect, and inhibitory signals have a
hyperpolarizing effect on the postsynaptic membrane.
• Integration is the summing up of these
excitatory and inhibitory signals.
Integration
Neurotransmitter Molecules
• Out of 25, two well-known
neurotransmitters are acetylcholine (ACh)
and norepinephrine (NE).
• Neurotranmitters that have done their job
are removed from the cleft; the enzyme
acetylcholinesterase (AChE) breaks down
acetylcholine.
• Neurotransmitter molecules are removed
from the cleft by enzymatic breakdown or
by reabsorption, thus preventing
continuous stimulation or inhibition.
The Central Nervous System
• The central nervous system (CNS)
consists of the spinal cord and brain.
• Both are protected by bone, wrapped in
protective membranes called meninges,
and surrounded and cushioned with
cerebrospinal fluid that is produced in the
ventricles of the brain.
• The ventricles are interconnecting cavities
that produce and serve as a reservoir for
cerebrospinal fluid.
• The CNS receives and integrates sensory
input and formulates motor output.
• Gray matter contains cell bodies and
short, nonmyelinated fibers; white matter
contains myelinated axons that run in
tracts.
Organization of the nervous system
The Spinal Cord
• The spinal cord extends from the base of
the brain through the vertebral canal.
• Structure of the Spinal Cord
• A central canal holds cerebrospinal fluid.
• Gray matter of the spinal cord forms an “H”
and contains interneurons and portions of
sensory and motor neurons.
• White matter consists of ascending tracts
taking sensory information to the brain and
descending tracts carrying motor
information from the brain.
Spinal cord
Functions of the Spinal Cord
• The spinal cord is the center for many
reflex arcs.
• It also sends sensory information to the
brain and receives motor output from the
brain, extending communication from the
brain to the peripheral nerves for both
control of voluntary skeletal muscles and
involuntary internal organs.
• Severing the spinal cord produces
paralysis.
The Brain
• The brain has four cavities called
ventricles.
• The cerebrum has two lateral ventricles,
the diencephalon has the third ventricle,
and the brain stem and cerebellum have
the fourth ventricle.
The human brain
The Cerebrum
• The cerebrum or telencephalon has two
cerebral hemispheres connected by the
corpus callosum.
• Learning, memory, language and speech
take place in the cerebrum.
• Sulci divide each hemisphere into lobes
including the frontal, parietal, occipital, and
temporal lobes.
Cerebral hemispheres
The Cerebral Cortex
• The cerebral cortex is a thin, highly
convoluted outer layer of gray matter
covering both hemispheres.
• The primary motor area is in the frontal lobe;
this commands skeletal muscle.
• The primary somatosensory area is dorsal to
the central sulcus or groove.
• The primary visual area is at the back
occipital lobe.
• The temporal lobe has the primary auditory
area.
• The parietal lobe provides taste sensation.
• All have adjacent association areas that
integrate signals; the prefrontal area is an
important association area for appropriate
behavior.
• White matter consists mostly of long
myelinated axons forming tracts; these
cross over so the left side of the brain
handles right side information.
• Basal nuclei are masses of gray matter
deep within the white matter integrate motor
commands.
The lobes of a cerebral hemisphere
The Diencephalon
• The hypothalamus and thalamus are in the
diencephalon that encircles the third
ventricle.
• The hypothalamus controls homeostasis and
the pituitary gland, and the thalamus
receives all sensory input except smell and
integrates it and sends it to the cerebrum.
• The pineal gland is also located here and
secretes melatonin that may regulate our
daily rhythms.
The Cerebellum
• The cerebellum receives sensory input
from eyes, ears, joints and muscles and
receives motor input from the cerebral
cortex.
• It integrates this information to maintain
posture and balance.
• The cerebellum is involved in learning of
new motor skills, such as playing the piano.
• A thin layer of gray matter covers the white
matter.
The Brain Stem
• The brain stem contains the medulla
oblongata, pons, and midbrain.
• The medulla oblongata and pons have
centers for vital functions such as
breathing, heartbeat, and vasoconstriction.
• The medulla also coordinates swallowing
and some other automatic reactions.
• The midbrain acts as a relay station
between the cerebrum and spinal cord or
cerebellum.
The Reticular Formation
• The reticular formation is a complex
network of nuclei and fibers that extend
the length of the brain stem.
• One portion of the reticular formation,
called the reticular activating system,
arouses the cerebrum via the thalamus
causing alertness.
• An inactive reticular activating system
results in sleep.
The reticular activating system
The Limbic System and Higher
Mental Functions
• Limbic System
• The limbic system is involved in our
emotions and higher mental functions.
• The limbic system is a complex network of
tracts and nuclei involving cerebral lobes,
basal nuclei and the diencephalon.
• Two structures, the hippocampus and
amygdala are essential for learning and
memory.
The limbic system
Higher Mental Functions
• Animal research, MRI, and PET scans
allow researchers to study the functioning
of the brain.
•
Memory and Learning
• Memory is the ability to hold a thought in
mind or recall events from the past.
• Learning takes place when we retain and
utilize past memories.
• Short-term memory involves activity in the
prefrontal area.
• Long-term memory includes semantic
memory (numbers, words, etc.) and
episodic memory (persons, events, etc.).
• Skill memory involves ability to ride a bike,
for example, and involves all motor areas
of the cerebrum below the level of
consciousness.
Long-term Memory Storage and
Retrieval
• Our long-term memories are stored in bits
and pieces throughout the sensory
association areas of the cerebral cortex.
• The hippocampus is a bridge between
sensory association areas and the
prefrontal area where memories are
utilized.
• The amygdala associates danger with
sensory stimuli.
Long-term memory circuits
Long-Term Potentiation
• Long-term potentiation is increased
response at synapses within the
hippocampus and is essential to long-term
memory.
• However, a postsynaptic neuron in the
hippocampus can become too excited and
then die.
• Excitotoxicity, a form of cell death, is due
to the neurotransmitter glutamate rushing
in too quickly.
Language and Speech
• Language and speech are dependent
upon Broca’s area (a motor speech area)
and Wernicke’s area (a sensory speech
area) that are involved in communication.
• These two areas are located only in the
left hemisphere; the left hemisphere
functions in language in general and not
just in speech.
Language and speech
The Peripheral Nervous System
• The peripheral nervous system (PNS)
contains nerves (bundles of axons) and
ganglia (cell bodies).
• Sensory nerves carry information to the
CNS, motor nerves carry information
away, and mixed nerves have both types
of fibers.
• Humans have 12 pairs of cranial nerves
and 31 pairs of spinal nerves.
Nerve structure
Cranial nerves
• The dorsal root of a spinal nerve contains
sensory fibers that conduct sensory
impulses from sensory receptors toward
the spinal cord.
• Dorsal root ganglia near the spinal cord
contain the cell bodies of sensory neurons.
• The ventral root of a spinal nerve contains
motor fibers that conduct impulses away
from the spinal cord to effectors.
Spinal nerves
Somatic System
• The somatic system serves the skin,
skeletal muscles, and tendons.
• The brain is always involved in voluntary
muscle actions but somatic system
reflexes are automatic and may not
require involvement of the brain.
The Reflex Arc
• Involuntary reflexes allow us to respond
rapidly to external stimuli.
• In reflexes, sensory receptors generate
nerve impulses carried to interneurons in
the spinal cord.
• Next, interneurons signal motor neurons
which conduct nerve impulses to a skeletal
muscle that contracts, giving the response
to the stimulus.
• Pain is not felt until the brain receives nerve
impulses.
A spinal nerve reflex arc
Autonomic System
•
The autonomic system of the PNS
regulates the activity of cardiac and
smooth muscle and glands.
• The system is divided into sympathetic
and parasympathetic divisions that:
1) Function automatically and involuntarily;
2) Innervate all internal organs; and
3) Use two neurons and one ganglion.
Sympathetic Division
• The sympathetic division is associated
with responses that occur during times of
stress, including “fight or flight” reactions.
• The postganglionic axon releases mainly
norepinephrine which acts similar to
adrenaline, the hormone from the adrenal
medulla.
Parasympathetic Division
• The parasympathetic system is associated
with responses that occur during times of
relaxation and promotes “housekeeper”
activities.
• The postganglionic neurotransmitter used
by the parasympathetic division is
acetylcholine.
Autonomic nervous system
Drug Abuse
• Stimulants increase excitation, and
depressants decrease excitation; either
can lead to physical dependence.
• Each type of drug has been found to either
promote or prevent the action of a
particular neurotransmitter.
• Medications that counter drug effects work
by affecting the release, reception, or
breakdown of dopamine, a
neurotransmitter responsible for mood.
Drug actions at a synapse
Drug use
Alcohol
• Alcohol may affect the inhibiting transmitter
GABA or glutamate, an excitatory
neurotransmitter.
• Alcohol is primarily metabolized in liver and
heavy doses can cause liver scar tissue
and cirrhosis.
• Alcohol is an energy source but it lacks
nutrients needed for health.
• Cirrhosis of the liver and fetal alcohol
syndrome are serious conditions associated
with alcohol intake.
Nicotine
• Nicotine is an alkaloid derived from
tobacco.
• In the CNS, nicotine causes neurons to
release dopamine; in the PNS, nicotine
mimics the activity of acetylcholine and
increases heart rate, blood pressure, and
digestive tract mobility.
• Nicotine induces both physiological and
psychological dependence.
Cocaine
• Cocaine is an alkaloid derived from the
shrub Erythroxylum cocoa, often sold as
potent extract termed “crack.”
• Cocaine prevents uptake of dopamine by
the presynaptic membrane, is highly likely
to cause physical dependence, and
requires higher doses to overcome
tolerance.
• This makes overdosing is a real possibility;
overdosing can cause seizures and cardiac
arrest.
Heroin
• Derived from morphine, heroin is an
alkaloid of opium.
• Use of heroin causes euphoria.
• Heroin alleviates pain by binding to
receptors meant for the body’s own pain
killers which are the endorphins.
• Tolerance rapidly develops and withdrawal
symptoms are severe.
Marijuana
• Marijuana is obtained from the plant
Cannabis sativa that contains a resin rich
in THC (tetrahydrocannabinol).
• Effects include psychosis and delirium and
regular use can lead to dependence.
• Long-term marijuana use may lead to
brain impairment, and a fetal cannabis
syndrome has been reported.
Chapter Summary
• The nervous system consists of two types
of cells: neurons and mesoglia.
• Neurons are specialized to carry nerve
impulses.
• A nerve impulse is an electrochemical
change that travels along the length of a
neuron fiber.
• Transmission of signals between neurons
is dependent on neurotransmitter
molecules.
• The central nervous system is made up of
the spinal cord and the brain.
• The parts of the brain are specialized for
particular functions.
• The cerebral cortex contains motor areas,
sensory areas, and association areas that
are in communication with each other.
• The cerebellum is responsible for
maintaining posture; the brainstem houses
reflexes for homeostasis.
• The reticular formation contains fibers that
arouse the brain when active and account
for sleep when they are inactive.
• The limbic system contains specialized
areas that are involved in higher mental
functions and emotional responses.
• Long-term memory depends upon
association areas that are in contact with
the limbic system.
• There are particular areas in the left
hemisphere that are involved in language
and speech.
• The peripheral nervous system contains
nerves that conduct nerve impulses toward
and away from the central nervous system.
• The autonomic nervous system has
sympathetic and parasympathetic divisions
with counteracting activities.
• Use of psychoactive drugs such as alcohol,
nicotine, marijuana, cocaine, and heroin is
detrimental to the body.
Ex 22: Annelida (segmented worms)
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Evolutionary tree
Annelids
• Annelids are segmented both externally,
and internally by partitions called septa.
• Annelids have a hydrostatic skeleton, and
partitioning of the coelom permits each
body segment to move independently.
• The tube-within-a-tube body plan allows the
digestive tract to have specialized organs.
• Annelids have an extensive closed
circulatory system with blood vessels that
run the length of the body and branch to
every segment.
• The brain is connected to a ventral solid
nerve cord with ganglia in each segment.
• The excretory system has nephridia in
each segment.
• A nephridium is a tubule that collects
wastes and excretes through an opening
in the body wall.
Marine Worms
• Polychaetes are marine worms with
paddlelike parapodia at the side of each
segment.
• Some polychaetes are sessile tube worms.
• A clam worm is a predaceous marine worm
with a defined head region.
• During breeding seasons, some worms form
sex organs in special segments and shed
these segment during breeding.
Polychaete diversity
Earthworms
• Earthworms are oligochaetes having few
setae per segment.
• Most scavenge for food in the soil and the
moist body wall functions in gas exchange.
• When muscles contract in each segment,
setae anchor in the soil, and aid locomotion.
• Five “hearts” pump blood and a branch
blood vessel reaches each segment.
• These worms are hermaphroditic.
• Segmentation in earthworms is evidenced
by:
• Body rings
• Coelom divided by septa
• Setae on most segments
• Ganglia and lateral nerves in each
segment
• Nephridia in most segments
• Branch blood vessels in each segment
Earthworm, Lumbricus
Leeches
• Most leeches are fluid feeders that attach
themselves to open wounds using
suckers.
• Bloodsuckers, such as the medicinal
leech, can cut through tissue.
• An anticoagulant (hirudin) in their saliva
keeps blood from clotting.
Ex 23: Arthropods!
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Evolutionary tree
Arthropods
• Arthropods are the most varied and
numerous of animals.
• The success of arthropods is largely
attributable to a flexible exoskeleton, jointed
appendages, and specialization of body
regions.
• Three body regions – head, thorax, and
abdomen – with specialized appendages in
each region, and a well-developed nervous
system characterize this group.
Arthropod diversity
Crustaceans
• Crustaceans are largely marine and have
a head that bears compound eyes, two pair
of antennae, and specialized mouth parts.
• Five pairs of walking legs include a first pair
of pinching claws.
• In the crayfish, head and thorax are fused
into a cephalothorax which is covered on
the top and sides by carapace.
• The abdominal segments have
swimmerets.
• The crayfish has an open circulatory
system in which the heart pumps blood
into a hemocoel consisting of sinuses
where the hemolymph flows about the
organs.
• Respiration takes place by gills under the
hard carapace, and there is a ventral solid
nerve cord.
• Sexes are separate in the crayfish.
Male crayfish, Cambarus
Insects
• The head of an insect usually bears a pair
of antennae, compound eyes, and simple
eyes.
• The thorax bears three pairs of legs and
up to two pairs of wings, and the abdomen
contains most of the internal organs.
• The insect exoskeleton is lighter and
contains less chitin than that of many other
arthropods.
Insect diversity
• Grasshoppers are examples of insects
adapted to a terrestrial life; they respire by
tracheae and have wings that allow them to
evade enemies; the third pair of legs is
suitable for jumping.
• There is a tympanum for the reception of
sound waves and a male penis for passing
sperm to the female without desiccation.
• Malpighian tubules function in excretion in
grasshopper.
• Grasshoppers undergo gradual
metamorphosis from nymph to adult.
• Butterflies undergo complete
metamorphosis, changing from larva to
pupa to adult.
Female grasshopper
Arachnids
• The arachnids include terrestrial spiders,
scorpions, ticks, and mites.
• The cephalothorax bears six pairs of
appendages: the chelicerae and the
pedipalps, and four pairs of walking legs.
• Scorpions are the oldest terrestrial
arthropods.
• Ticks and mites are parasitic.
• Spiders are well-adapted to life on land
and have Malphigian tubules – they
secrete uric acid, helping to conserve
water.
• Spiders spin silk used in various ways.
• Where spiders spin webs, the type of web
is a feature that demonstrates the
evolutionary relationship among spiders.
Arachnid diversity