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Chapter 32
Section 2 Invertebrates
and Vertebrates
Objectives
• Compare symmetry, segmentation, and body
support in invertebrates and vertebrates.
• Describe the differences in the respiratory and
circulatory systems of invertebrates and vertebrates.
• Compare the digestive, excretory, and nervous
systems of invertebrates and vertebrates.
• Contrast reproduction and development in
invertebrates and vertebrates.
Chapter 32
Section 2 Invertebrates
and Vertebrates
Invertebrate Characteristics
• Adult invertebrates show large amount of
morphological (form or structural) diversity.
• Invertebrates may be characterized based on their:
– Symmetry (radial or bilateral)
– Segmentation
– Support of the Body
– Respiratory and Circulatory Systems
– Digestive and Excretory Systems
– Nervous System
– Reproduction and Development
Chapter 32
Segmentation
• Segmentation in animals refers to a body composed
of a series of repeating similar units.
– in its simplest form each unit of the body is similar
to the next one
– in more complex forms, segments may look
different and have different functions
Chapter 32
Support of the Body
• An animal's skeleton provides a framework that
supports the animal's body and is vital to an animal's
movement.
• Many soft-bodied invertebrates, such as jellyfish,
have a hydrostatic skeleton, which is a water-filled
cavity that is under pressure. (Balloon)
• An exoskeleton is a rigid external skeleton that
encases the body of an animal.
– Insects, clams, and crabs have exoskeletons..
Chapter 32
Section 2 Invertebrates
Respiratory and Circulatory Systems
• The respiratory system is responsible for
exchanging oxygen and carbon dioxide between the
body and the environment.
– occurs either directly across the body covering or
through internal gills.
Chapter 32
Circulatory System
• In most animals, the circulatory system moves blood
or a similar fluid through the body to transport oxygen
and nutrients to cells, and carbon dioxide and wastes
away from cells.
• Animals may have one of the following:
– no circulatory system
– an open circulatory system
– a closed circulatory system
Chapter 32
Circulatory System
Circulatory System
• In an open circulatory system, a heart pumps fluid
containing oxygen and nutrients through vessels into
the body cavity. The fluid provides oxygen and
nutrients as it washes across the tissues.
• In a closed circulatory system, the blood is pumped
through the body within vessels and is never in direct
contact with the body's tissues.
Chapter 32
Open and Closed Circulatory System
Chapter 32
Section 2 Invertebrates
Digestive and Excretory Systems
• The digestive system is responsible for extracting
energy and nutrients from an animal's food.
• The excretory system removes waste products from
the animal's body.
Chapter 32
Digestive System
• A gastrovascular
cavity is a digestive
cavity with only one
cavity. There are no
specialized digestive
cells.
• The hydra has a
gastrovascular
cavity.
Chapter 32
Digestive System
• In a digestive tract, food moves from one opening,
the mouth, to a second, the anus.
• Digestive tracts allow for specialization and more
efficient digestion.
Chapter 32
Section 2 Invertebrates
Nervous System
• The nervous system carries information about the
environment through the body and coordinates
responses and behaviors.
– range from simple, with no neurons, to complex,
with a high degree of cephalization and a complex
brain.
– The phylum Mollusca exhibits the progression of
cephalization and the evolution of the brain.
• The most highly cephalized mollusk is the octopus.
Chapter 32
Simple Nervous Systems
• All animals except sponges have nerve cells,
neurons.
• In the simplest arrangement of nerves, called a nerve
net, nerve cells do not coordinate actions efficiently.
– Jellyfish and hydras have a nerve net.
Hydra Nerve Net
• Many animals have clusters of nerve cells called
ganglia that can coordinate responses.
• Flatworms have large more-complex ganglia, similar
to a brain.
Flatworm Nervous System
Complex Nervous Systems
• More-complex invertebrates have a true brain with
sensory structures, such as eyes, associated with it.
Chapter 32
Section 2 Invertebrates
Reproduction and Development
• Invertebrates are capable of sexual reproduction, and
many can also reproduce asexually.
– Some invertebrates are hermaphrodites.
• Two patterns of invertebrate development occur :
– Indirect development has an intermediate stage
called a larva (plural, larvae).
– Direct development has no larval stage.
• Pg. 659
Chapter 32
Section 2 Invertebrates
and Vertebrates
Vertebrate Characteristics
• Vertebrates are chordates that have a backbone.
– Classes of vertebrates include fishes, amphibians,
reptiles, birds, and mammals.
• Many characteristics of terrestrial vertebrates are
adaptations to life on land and fall into two broad
categories:
– support of the body
– conservation of water
Chapter 32
Section 2 Vertebrates
Segmentation and Support of the Body
• Vertebrates segmentation is evident in the ribs and
the vertebrae of vertebrates.
– As terrestrial vertebrates evolved from aquatic
vertebrates
– Their limbs and associated muscles evolved to
give the animals better support and greater
mobility.
• Vertebrates have an endoskeleton that grows as the
animal grows.
Chapter 32
Section 2 Invertebrates
and Vertebrates
Vertebrate Skeleton
Chapter 32
Section 2 Invertebrates
and Vertebrates
Body Coverings
• The outer covering of an animal is called the
integument.
– Aquatic animals adapted only to moist
environments.
– Terrestrial vertebrates are adapted to the dry
conditions.
• Integuments serve other purposes such as respiration,
protection, or insulation.
Chapter 32
Section 2 Vertebrates
Respiratory and Circulatory Systems
• Gas exchange occurs in the gills of aquatic
vertebrates.
• Lungs evolved in terrestrial vertebrates.
• Vertebrates have a closed circulatory system with
a multichambered heart.
• In some vertebrates, the multichambered heart has
separate chambers and is more efficient.
Chapter 32
Section 2 Vertebrates
Open and Closed Circulatory Systems
Chapter 32
Section 2 Vertebrates
Digestive and Excretory Systems
Digestive and Excretory Systems
• Digestion occurs in the gut.
• In many vertebrates, the gut is very long and folded.
• Most vertebrates must expel wastes while conserving
water.
– Most convert ammonia to less toxic substances.
• In most vertebrates, kidneys filter wastes from the
blood while regulating water levels in the body.
Chapter 32
Section 2 Vertebrates
Nervous System
• Vertebrates have highly organized brains, and the
control of specific functions occurs in specific centers
in the brain.
• The structure and function of the nervous system
vary among vertebrate classes.
– Fishes have limited neural circuitry devoted to
simple decision making.
– Many mammals display complex and flexible
behavior.
Chapter 32
Section 2 Vertebrates
Reproduction and Development
Reproduction and Development
• External or internal
• Most vertebrates undergo direct development.
Chapter 32
Section 2 Invertebrates
and Vertebrates
Major Vertebrate Organ Systems