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Animal Systems 2:
Response
Chapter 28.1
How do animals respond to events
around them?
►Most
animals have a special nervous
system to respond to events around
them
►Nervous systems are composed of
specialized nerve cells called neurons
►Information in the environment that
causes an organism to react is called a
stimulus
Nervous System
► The
nervous system has two primary functions
that are critical in maintaining life of the organism:
► 1. Sensory receptors allow organism to monitor its
external environment and detect changes (ex
increase in temperature)
 This allows for activation of muscles and glands to
respond to these environmental changes
► 2.
Monitors organisms internal environment
 Controlling heart rate and measuring nutrient levels
Neuron
►A
neuron consists of
several parts:
 Soma- cell body
 Dendrites- brings
information to cell body
 Axon-takes information
away from cell body
 Myelin sheath
Detecting Stimuli
► Animals
ability to
detect stimuli depends
on specialized cells
called sensory neurons
► Each type of sensory
neuron responds to a
particular stimulus
such as light, heat or
chemicals
Detecting Stimuli
► Humans
share many types of sensory cells
with other animals, many animals have
types of sensory cells that humans lack.
► This is one reason why some animals
respond to stimuli that humans cannot
detect.
Processing Information
When sensory neurons detect a
stimulus, they pass info about it to
other nerve cells called
interneurons, which process
information and determine how an
animal responds
► The number of interneurons an
animal has determines how
complex an animal can be
 Ex: some invertebrates such as
cnidarians and worms have very
few interneurons and are
capable of only simple
responses to stimuli
►
Responding
► When
an animal responds to a stimulus, body
systems (sensory neurons, nervous system and
muscles) work together to generate a response
► Nerve cells called motor neurons carry
“directions” from interneurons to muscles
Motor Neurons in Vertebrates
►There
are three different forms of
motor neurons in vertebrates
depending on species
 Muscles of the limbs which are involved in
locomotion
 Another involves brachial muscles
(motorize the gills in fish)
 Movement of cardiac and smooth muscles
(muscles of the arteries)
Nervous System Evolution
► Animal
nervous systems exhibit different degrees
of cephalization and specialization
► Cephalization is the process through evolution of
the sensory and neural organs to be
concentrated in an anterior head
Invertebrates
► Invertebrate
nervous systems range from
simple collections of nerve cells to complex
organizations that include many
interneurons
► Cnidarians, such as jellyfishes, have simple
nervous systems called nerve nets
► Nerve nets consist of neurons connected
into a netlike arrangement with few
specializations
Invertebrates
► In
symmetric invertebrates, such as sea
stars, some interneurons are grouped
together into nerves, or nerve cords, that
form a ring around the animals’ mouths and
stretch out along their arms (sea stars)
► In other invertebrates, a number of
interneurons are grouped together into
small structures called ganglia, in which
interneurons connect with one another
Organization of Interneurons
► Interneurons
form ganglia in several places,
with the largest ganglia typically located in
the head region and called cerebral ganglia
► In some species, cerebral ganglia are
further organized into a structure called a
brain
► The brains of some cephalopods, such as
octopi, enable complex behavior, including
several kinds of learning
Parts of the Vertebrate brain
► Regions
of the vertebrate brain include the
cerebrum, cerebellum, medulla oblongata, optic
lobes, and olfactory bulbs
Parts of the Vertebrate Brain
► The
cerebrum is the “thinking” region of the brain.
It is also involved in learning, memory and
conscious thought
 It receives and interprets sensory information and
determines a response
► The
cerebellum coordinates movement and
controls balance
► The medulla oblongata controls the functioning of
many internal organs
► Optic Lobes are involved in vision and olfactory
bulbs are involved in the sense of smell
Brain Evolution
► Brain
evolution, in vertebrates follows a general
trend of increasing size and complexity from
fishes, through amphibians and reptiles, to birds
and mammals
► In fishes, amphibians, and reptiles, the cerebrum,
or “thinking” region, is relatively small
► In birds and mammals, and especially in primates,
the cerebrum is much larger and may contain folds
that increase its surface area
► The cerebellum is also most highly developed in
birds and mammals
Sensory Systems
► Sensory
systems vary in complexity including both
sensory neurons and other cells that help gather
information
► Many invertebrates have sense organs that detect
light, sound, vibrations, movement, body
orientation, and chemicals in air or water
 Flatworms, for example have simple eyespots that
detect only the presence and direction of light
Chordate Sense Organs
► Although
all
mammalian ears have
the same basic parts,
they differ in their
ability to detect sound
► Bats and dolphins can
find objects in their
environment using
echoes of their own
high-frequency sounds
Animal Systems 2:
Movement and Support
Chapter 28.2
Essential Questions
►What
are the 3 types of
skeleton?
►How do muscles enable
movement?
Movement and Support
►An
animal’s ability to move efficiently is
greatly enhanced by rigid body parts.
►Animals have three main kinds of
skeletal systems:
 Hydrostatic skeletons
 Exoskeletons
 Endoskeletons
Hydrostatic Skeletons
► Found
in many coldblooded organisms and
soft bodied animals
with a fluid filled cavity
► The fluids held in a
gastrovascular cavity
can alter the animal’s
body shape drastically
by working with
contractile cells in its
body wall
Exoskeletons
► Many
arthropods and most mollusks (snails
and clams) have exoskeletons
► The exoskeleton of an arthropod is a hard
body covering made of a protein called
chitin
► Most mollusks have exoskeletons made of
calcium carbonate
Exoskeleton Functions
► The
various functions of an exoskeleton
include:
 Jointed exoskeletons enable various
arthropods to swim, fly, burrow, walk, crawl,
and leap
 Provide watertight coverings that enable some
arthropods to live in Earth’s driest places
 Can provide physical protection against
predators
Exoskeleton Disadvantages
► An
external skeleton poses a problem when
the animal needs to grow
► How is this fixed?
 To increase in size, arthropods break out
of their exoskeleton and grow a new one,
in a process called molting
 Exoskeletons are heavy
Endoskeleton
► An
endoskeleton is a structural support within
the body
► Echinoderms and vertebrates have
endoskeletons
► Vertebrates endoskeleton is made of cartilage or
a combo of cartilage and bone
Advantages and Disadvantages
►Disadvantage
 Since it does
not surround
the body it
cannot protect
the body like an
exoskeleton can
►Advantages
 Provide strong,
lightweight
support
 Can grow as
the animal
grows
 No molting
Joints
► Arthropods
and vertebrates can bend because
many parts of their skeletons are connected by
joints
► Joints are places where parts of a skeleton are
held together in ways that enable them to move
with respect to one another
Ligaments
► In
vertebrates, bones
are connected at joints
by strong connective
tissues called ligaments
► Most joints are formed
by a combination of
ligaments, cartilage,
and lubricating joint
fluid that enables bones
to move without painful
friction
Tendons
► Muscles
are attached
to bones around the
joints by tough
connective tissue
called tendons
► Tendons are attached
in such a way that they
pull on bones when
muscles contract
Muscles and Movement
► In
many animals, muscles work together in
pairs or groups that are attached to different
parts of a supporting skeleton
► Muscles are specialized tissues that
produce physical force by contracting, or
getting shorter, when they are stimulated
► Muscles can relax when they aren’t being
stimulated, but they cannot actively get
longer
Movement
► In
both arthropods and vertebrates, different pairs
or groups of muscles pull across the joint in
different directions
► When one muscle group contracts, it bends, or
flexes, the joint
► When the first group relaxes and the second group
contracts, the joint straightens
► The shapes and relative positions of bones,
muscles, and joints are linked very closely to the
functions they perform
► Differently shaped bones and muscles form limbs
adapted for long-distance jumping (frogs),
manipulating objects (raccoons), climbing trees
(sloths), and flying (birds)
Animal Systems 2:
Reproduction
Chapter 28.3
Essential Questions
►How
do sexual and asexual
reproduction in animals compare?
►How do internal and external
fertilization differ?
►Where do embryos develop?
►How are terrestrial vertebrates adapted
to reproduction on land?
Reproduction
►Asexual reproduction
 Requires only one parent
 Individuals in favorable environmental
conditions can reproduce rapidly
 No genetic diversity
►Sexual




reproduction
Requires 2 parents
New combinations of genes
Maintains genetic diversity
Better able to evolve/adapt to changing
environments
Asexual Reproduction
► Animals
reproduce asexually in many ways:
 Some cnidarians divide into two
 Some animals reproduce via budding, which
produces new individuals as outgrowths of the
body wall
 The process parthenogenesis, produces
offspring that carry DNA inherited only from
their mothers
Sexual Reproduction
►Among
annelids, mollusks, and fishes,
some species are hermaphrodites
 Can be both male and female or can
convert from one sex to the other
 Example: Clownfish may change from
one sex to another as they mature
Reproductive Cycles
► Some
invertebrates
have life cycles that
alternate between
sexual and asexual
reproduction.
► Parasitic worms and
cnidarians alternate
between forms that
reproduce sexually and
forms that reproduce
asexually.
Internal & External Fertilization
► During
internal fertilization, eggs are
fertilized inside the body of the eggproducing individual
 Includes many aquatic and all terrestrial
animals
► In external fertilization, eggs are fertilized
outside the body of the egg-producing
individual
 Includes ranges of aquatic invertebrates
and vertebrate species
Embryos
► Oviparous
species are
those in which
embryos develop in
eggs outside the
parents’ bodies
► Includes: most
invertebrates, many
fishes and amphibians,
most reptiles, all birds,
and a few odd
mammals
Ovoviviparous Species
►
►
In ovoviviparous species,
embryos develop within the
mother’s body, but they depend
entirely on the yolk sac of their
eggs. The young do not receive
any additional nutrients from the
mother
The young either hatch within the
mother’s body or are released
immediately before hatching.
They swim freely shortly after
hatching.
 Includes guppies and some shark
species
Viviparous Species
► Viviparous
species are those in which embryos
obtain nutrients from the mother’s body
 Occurs in most mammals, sharks, amphibians and reptiles
► In
viviparous insects and in some sharks and
amphibians, young are nourished by secretions
produced in the mother’s reproductive tract
► Placental mammals use a placenta, an organ
which enables exchange of respiratory gases,
nutrients, and wastes between the mother and her
developing young.
Metamorphosis
► Metamorphosis
is a developmental process
that leads to dramatic changes in shape and
form
► In aquatic invertebrates they have a larval
stage, which looks nothing like an adult
► Terrestrial invertebrates go through
incomplete or complete metamorphosis.
► Amphibian metamorphosis is controlled by
hormones.
Terrestrial Metamorphosis
►
►
Incomplete metamorphosis: They
have immature forms called nymphs
that resemble adults but lack
functional sexual organs and some
adult structures (wings)
 As they molt they acquire adult
structures
Complete metamorphosis: Larvae look
nothing like their parents. A final molt
causes a dramatic change into a pupa
(larva to adult stage).
Reproductive Diversity in Chordates
► The
amniotic egg evolved
in reptiles, birds, and a
few mammals, which is
an embryo that develops
outside its mother’s body
and out of water.
► Early chordate eggs
needed to develop in
water.
Reproductive Diversity in Chordates
► Mammalian
Reproductive
Strategies
 Monotremes: Lay
amniotic eggs that are
incubated outside her
body, but are
nourished by milk
produced in mammary
glands after the eggs
hatch.
Reproductive Diversity in Chordates
► Mammalian
Strategies
Reproductive
 Marsupials: Bear live young
that complete their
development in an external
pouch.
 Placentals: Use a placenta
to exchange nutrients
between embryo and
mother.
Embryological Development
►
During embryological development,
the cells of most animal embryos
differentiate into three layers called
germ layers.
 Endoderm (Innermost germ layer):
Develop into the linings of the
digestive and respiratory tract.
 Mesoderm (Middle layer): Give rise
to muscles, circulatory,
reproductive, and excretory organs.
 Ectoderm (Outermost layer):
Produces the nervous system and
skin.
Ectotherm
►
►
►
Ectotherms are animals that
regulate body temperature
primarily by absorbing heat
from, or losing heat to, their
environment
They have relatively low
metabolic rates when
resting, so their bodies don’t
generate much heat
Their muscles generate heat
when active, but since most
ectotherms lack effective
body insulation, their body
heat is easily lost to the
environment
Endotherm
An endotherm is an
animal whose body
temperature is regulated,
at least in part, using heat
generated by its body
► Have high metabolic rates
that generate heat, even
when they are resting
► Conserve heat through
feathers, body fat, hair
► Remove excess heat
through panting or
sweating
► All mammals and birds
►
Animal Systems 2:
Homeostasis
Chapter 28.4
Homeostasis
► Homeostasis
or control of internal
conditions, is essential to an organism’s
survival.
► For example, brain cells must be bathed in
fluid with a constant concentration of water
and be cleansed of metabolic waste
products. Failure of this, for even a few
minutes could lead to brain injury or death.
Interrelationship of Body Systems
►
►
►
►
The digestive, respiratory, circulatory, excretory, nervous,
muscular, and skeletal systems are all interconnected and
work together to maintain homeostasis
In most animals, respiratory and digestive systems would
be useless without circulatory systems to distribute oxygen
and nutrients
The excretory system needs a circulatory system to collect
carbon dioxide and nitrogenous wastes from body tissues
and deliver them to the lungs and excretory organs
Muscles wouldn’t work without a nervous system to direct
them and a skeletal system to support them
Homeostasis Examples
► Fighting
Disease
 Immune system to distinguish foreign pathogens from
own cells
► Chemical
Controls
 Endocrine glands regulate body activities by releasing
hormones into the blood, where they are carried to the
designated organs
► Body
temperature control
 Requires three components: a source of heat, a way to
conserve heat when necessary, and a method of
eliminating excess heat when necessary
Ectotherm
►
►
►
Ectotherms are animals that
regulate body temperature
primarily by absorbing heat
from, or losing heat to, their
environment
They have relatively low
metabolic rates when
resting, so their bodies don’t
generate much heat
Their muscles generate heat
when active, but since most
ectotherms lack effective
body insulation, their body
heat is easily lost to the
environment
Endotherm
An endotherm is an
animal whose body
temperature is regulated,
at least in part, using heat
generated by its body
► Have high metabolic rates
that generate heat, even
when they are resting
► Conserve heat through
feathers, body fat, hair
► Remove excess heat
through panting or
sweating
►
Analgesia
► It
is the loss of sensation of pain that results from
an interruption in the nervous system pathway
between a sense organ and brain.
► Different forms of sensation (touch, temperature
and pain) can stimulate an area of skin travel to
the spinal cord by different nerve fibres in the
same nerve bundle. Therefore, any injury or
disease affecting the nerve would abolish all forms
of sensation in the area supplied by it
► When sensory nerves reach the spinal cord,
however, their fibres separate and follow different
courses to the brain