Transcript Ch16_lecture - Fullfrontalanatomy.com

Chapter 16
The Diversity of Life
Lectures by
Gregory Ahearn
University of North Florida
Copyright © 2009 Pearson Education, Inc..
16.1 How Are Organisms Named And
Classified?
 Organisms are placed into categories on the
basis of their evolutionary relationships.
• There are eight major categories.
• Domain, kingdom, phylum, order, class,
family, genus, species
• These categories form a nested hierarchy in
which each level includes all the ones
before it.
Copyright © 2009 Pearson Education Inc.
16.1 How Are Organisms Named And
Classified?
Copyright © 2009 Pearson Education Inc.
16.1 How Are Organisms Named And
Classified?
 Each species has a unique, two-part name.
• The scientific name of an organism is formed
from the genus and species categories.
• Each genus includes a group of closely
related species, and within each species are
individuals that can interbreed.
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16.1 How Are Organisms Named And
Classified?
 Each species has a unique, two-part name
(continued).
• Thus, the genus Sialia (bluebirds) includes the
eastern bluebird (Sialia sialis), the western
bluebird (Sialia mexicana), and the mountain
bluebird (Sialia currucoides)—similar birds
that do not interbreed.
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16.1 How Are Organisms Named And
Classified?
 Three species of bluebird
Fig. 16-1
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16.1 How Are Organisms Named And
Classified?
 Each species has a unique, two-part name
(continued).
• Each two-part scientific name is unique;
referring to an organism by its scientific name
rules out any chance of ambiguity or
confusion.
• By convention, scientific names are underlined
or italicized.
• The first letter of the genus name is always
capitalized, and the first letter of the species
name is always lowercase.
• The species name is never used alone but is
always paired with its genus name.
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16.1 How Are Organisms Named And
Classified?
PLAY
Animation—Taxonomic Classification
Copyright © 2009 Pearson Education Inc.
16.1 How Are Organisms Named And
Classified?
 Classification originated as a hierarchy of
categories.
• Aristotle (384–322 B.C.) was among the first to
classify living things; he classified about 500
organisms based on structural complexity,
behavior, and degree of development at birth.
Copyright © 2009 Pearson Education Inc.
16.1 How Are Organisms Named And
Classified?
 Classification originated as a hierarchy of
categories (continued).
• Carolus Linnaeus (1707–1778) placed each
organism into a series of hierarchically
arranged categories on the basis of its
resemblance to other life-forms, and
introduced the scientific name composed of
genus and species.
Copyright © 2009 Pearson Education Inc.
16.1 How Are Organisms Named And
Classified?
 Classification originated as a hierarchy of
categories (continued).
• Charles Darwin (1809–1882) demonstrated
that all organisms are connected by common
ancestry; the more categories two organisms
share, the closer their evolutionary
relationship.
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16.1 How Are Organisms Named And
Classified?
 Biologists identify features that reveal
evolutionary relationships.
• Scientists who devise classifications must
distinguish informative similarities caused by
common ancestry from uninformative
similarities that result from convergent
evolution.
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16.1 How Are Organisms Named And
Classified?
 Biologists identify features that reveal
evolutionary relationships (continued).
• In the search for informative similarities,
biologists look at many kinds of
characteristics.
• Anatomical similarities play a key role in
classification.
• Molecular similarities are also useful in
classification.
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16.1 How Are Organisms Named And
Classified?
 Microscopic structures may be used to
classify organisms.
Fig. 16-2
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16.2 What Are The Domains Of Life?
 Before 1970, all forms of life were classified
into two kingdoms: Animalia and Plantae.
• All bacteria, fungi, and photosynthetic
eukaryotes were considered to be plants, and
all other organisms were classified as animals.
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16.2 What Are The Domains Of Life?
 The five-kingdom system improved
classification.
• Robert H. Whittaker’s five-kingdom system
placed all prokaryotic organisms into a single
kingdom, and divided the eukaryotes into four
kingdoms.
• The prokaryotes were placed in the kingdom
Monera.
• The five-kingdom system was an improvement
over the two-kingdom system.
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16.2 What Are The Domains Of Life?
 A three-domain system
more accurately
reflects life’s history.
• Carl Woese studied the
biochemistry of the
Moneran organisms.
• Despite their superficial
similarities, these two
groups are actually
radically different.
Fig. 16-3
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16.2 What Are The Domains Of Life?
 A three-domain system more accurately
reflects life’s history (continued).
• He found them to be divided into two groups
based on the nucleotide sequences in the
RNA in their ribosomes, and called the two
groups the Bacteria and the Archaea.
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16.2 What Are The Domains Of Life?
 The tree of life
• The five-kingdom system was replaced by one
that divides life into three domains: Bacteria,
Archaea, and Eurkarya.
BACTERIA
ARCHAEA
EUKARYA
animals
fungi
plants
protists
Fig. 16-4
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16.2 What Are The Domains Of Life?
PLAY
Animation—Tree of Life
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16.2 What Are The Domains Of Life?
 Kingdom-level classification remains
unsettled.
• Biologists recognize 15 kingdoms among the
Bacteria.
• There are three kingdoms in the Archaea.
• There are four kingdoms among the Eukarya.
• Animals
• Plants
• Fungi
• Protists
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16.3 Bacteria And Archaea
 Earth’s first organisms were prokaryotes—
single-celled microbes that lacked
organelles such as a nucleus, chloroplasts,
and mitochondria.
• In terms of abundance, prokaryotes are
Earth’s predominant form of life.
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16.3 Bacteria And Archaea
 Bacteria and Archaea are fundamentally
different.
• Two of life’s domains, Bacteria and Archaea,
consist entirely of prokaryotes; yet there are
fundamental differences between them.
• Bacterial cells contain molecules of the
polymer peptidoglycan, which strengthens the
cell wall.
• These two groups also differ in the structure
and composition of the plasma membrane,
ribosomes, and RNA polymerases, as well as
in the processes of transcription and
translation.
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16.3 Bacteria And Archaea
 Classification of prokaryotes within each domain is
difficult.
• The biochemical differences between archaea and
bacteria make distinguishing the two domains an
easy matter, but classification within each domain
poses challenges.
• Prokaryotes have been classified on the basis of such
features as shape, means of locomotion, pigments,
nutrient requirements, the appearance of colonies,
and staining properties.
• More recently, the comparisons of DNA and RNA
nucleotide sequences have been used in prokaryotic
classification.
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16.3 Bacteria And Archaea
 Prokaryotic adaptations provide mobility and
protection.
• Prokaryotes are usually small, 0.2 to 10
micrometers in diameter, compared to 10 to
100 micrometers for eukaryotic cells.
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16.3 Bacteria And Archaea
 The cell walls that surround prokaryotic cells
give characteristic shapes to different types
of bacteria and
archaea; the most
common shapes
are spherical,
rodlike, and
corkscrew-shaped.
Fig. 16-5
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16.3 Bacteria And Archaea
 Prokaryotic adaptations provide mobility and
protection (continued).
• Some prokaryotes are mobile; some may
have flagella.
• Flagella can rotate rapidly and propel the
organism through the environment.
Fig. 16-6
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16.3 Bacteria And Archaea
 Prokaryotic adaptations provide mobility and
protection (continued).
• Many prokaryotes form films on surfaces.
• Some prokaryotes secrete slime that allows
them to adhere to surfaces, or can aggregate
into biofilms made up of one or more species
in colonies.
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16.3 Bacteria And Archaea
 Prokaryotic adaptations provide mobility and
protection (continued).
• Biofilms protect the embedded bacteria
against a variety of attacks, such as from
antibiotics and disinfectants.
• Some of the common biofilms are responsible
for tooth decay, gum disease, and ear
infections.
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16.3 Bacteria And Archaea
 Protective endospores allow
some bacteria to withstand
adverse conditions.
Fig. 16-7
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16.3 Bacteria And Archaea
 Prokaryotic adaptations provide mobility and
protection (continued).
• The endospore forms within the bacterium,
and contains genetic material and a few
enzymes encased in a thick protective coat.
• Metabolic activity ceases until the spore
encounters favorable conditions, which may
take an extremely long period of time.
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16.3 Bacteria And Archaea
 Prokaryotes are specialized for specific
habitats.
• Prokaryotes occupy virtually every habitat,
including those where extreme conditions
keep out other forms of life.
• Many archaea can live in hot springs at
temperatures up to 110°C; they can live at
extreme pressures beneath the Earth’s
surface, and at very cold temperatures of the
Antarctic.
• They can live in the Dead Sea, with salt
concentrations seven times those of the
ocean.
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16.3 Bacteria And Archaea
 Prokaryotes exhibit diverse metabolisms.
• Many prokaryotes are anaerobes; their
metabolisms do not require oxygen.
• Others are opportunistic, using anaerobic
respiration when oxygen is absent and
switching to aerobic respiration when oxygen
is available.
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16.3 Bacteria And Archaea
 Prokaryotes exhibit diverse metabolisms
(continued).
• Prokaryotes feed on many things, including
sugars, proteins, and fats, but also petroleum,
methane, benzene, and toluene; some can
use hydrogen, sulfur, ammonia, iron, and
nitrate.
• Some prokaryotes possess chlorophyll and
are photosynthetic.
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16.3 Bacteria And Archaea
 Prokaryotes reproduce by binary fission.
• Most prokaryotes reproduce asexually by
binary fission, which produces identical copies
of the original cell.
• They reproduce rapidly and can evolve quickly
to adapt to changing conditions.
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16.3 Bacteria And Archaea
 Prokaryotes affect humans and other
organisms.
• Prokaryotes play important roles in animal
nutrition.
• Many animals that eat plants cannot digest the
cellulose in plants themselves and rely on
symbiotic bacteria in their digestive tracts,
which are able to digest cellulose, to liberate
nutrients from this food source.
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16.3 Bacteria And Archaea
 Prokaryotes affect humans and other
organisms (continued).
• Many foods that humans eat are produced by
the actions of bacteria, including cheese,
yogurt, and sauerkraut.
• Some bacteria in human intestines feed on
undigested food and synthesize nutrients,
such as vitamin K and vitamin B12, which the
human body absorbs.
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16.3 Bacteria And Archaea
 Prokaryotes capture the nitrogen needed by
plants.
• Plants obtain nitrogen for growth from bacteria
that live in the soil, or from nitrogen-fixing
bacteria in special nodules on the roots of
certain plants.
• These include legumes such as alfalfa,
soybeans, lupines, and clover.
• These bacteria capture nitrogen gas from air
in the soil and combine it with hydrogen to
produce ammonia that plants use directly.
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16.3 Bacteria And Archaea
 Prokaryotes are nature’s recyclers.
• Prokaryotes consume the organic molecules
in the dead bodies of plants and animals,
decomposing their wastes and recycling them
to the environment.
• Prokaryotes can clean up pollution.
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16.3 Bacteria And Archaea
 Prokaryotes are nature’s recyclers
(continued).
• Nearly anything that human beings can
synthesize can be broken down by some
prokaryote, including detergents, toxic
pesticides, and harmful industrial chemicals.
• Even oil can be broken down by prokaryotes.
• The breakdown of pollutants by bacteria is
called bioremediation.
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16.3 Bacteria And Archaea
 Some anaerobic bacteria produce
dangerous poisons.
• Some bacteria produce toxins that attack the
nervous system.
• Clostridium tetani causes tetanus.
• C. botulinum causes botulism (lethal food
poisoning).
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16.3 Bacteria And Archaea
 Humans battle bacterial diseases old and
new.
• Pathogenic (disease-causing) bacteria
synthesize toxic substances that cause
diseases in humans.
• Bubonic plague (“Black death”) killed 100
million people during the fourteenth century.
• Tuberculosis, gonorrhea, syphilis, and
cholera are bacterial diseases long
associated with humans.
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16.3 Bacteria And Archaea
 Common bacterial species can be harmful.
• Streptococcus causes strep throat.
• Another causes pneumonia, which clogs the
lungs with fluid.
• A common bacterium of the human digestive
tract, Escherichia coli (E. coli), normally is
benign but can transform into a pathogenic
form that can be transmitted from human to
human.
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16.4 Protists
 The protists are eukaryotes that are not a
plant, an animal, or a fungus.
• Most protists are single-celled.
• While most members of this group are small,
they are incredibly diverse in their modes of
reproduction and in their structural and
physiological innovations.
• Some of the larger protists are colonies of
single-celled individuals, while others are
multicellular organisms.
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16.4 Protists
 Protists affect humans and other organisms.
• Protists have both positive and negative
effects upon humans.
• The primary positive impact comes from the
ecological roles of photosynthetic marine
protists.
• On the negative side are the many human
diseases caused by parasitic protists.
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16.4 Protists
 Some of the harmful and helpful protists are
listed on the slides that follow.
• Stramenopiles include photosynthetic and
nonphotosynthetic organisms, and include the
diatoms and the brown algae.
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16.4 Protists
 Diatoms encase
themselves within
glassy (silica) walls,
and are
photosynthetic
phytoplankton that
float passively in
lakes and oceans.
Fig. 16-8
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16.4 Protists
 Brown algae dominate in cool coastal
waters and form multicellular aggregations
known as brown algae seaweeds.
Fig. 16-9
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16.4 Protists
 Alveolates include parasites, predators, and
phytoplankton.
• Most dinoflagellates are photosynthetic and
move with the use of their two whiplike
flagella.
• They are important components of the
phytoplankton and are food sources for larger
organisms.
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16.4 Protists
 Dinoflagellates
Fig. 16-10
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16.4 Protists
 Alveolates include parasites, predators, and
phytoplankton (continued).
• They cause “red tides” during population
explosions, which kill fish by suffocation due to
lack of oxygen from the decay of billions of
dinoflagellates.
• Shellfish filter these from the sea and
concentrate the toxins that they produce,
causing shellfish poisoning.
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16.4 Protists
 A red tide
Fig. 16-11
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16.4 Protists
 Apicomplexans are parasitic and have no
means of locomotion.
• These live inside the bodies or cells of their
hosts.
• An example is the malarial parasite
Plasmodium, which lives in the Anopheles
mosquito and is transmitted to a human victim
by the insect.
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16.4 Protists
 Ciliates are the most complex of the
alveolates.
• They possess hairlike
outgrowths of the
plasma membrane
that are used for
locomotion.
• Two examples are
Paramecium and
the predator,
Didinium.
Fig. 16-12
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16.4 Protists
 Cercozoans have thin pseudopods and
elaborate shells.
• They possess flexible plasma membranes that
can extend in any direction to form finger-like
projections called pseudopods.
• The pseudopods of this group extend through
a shell and are threadlike; the largest group is
the foraminiferans.
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16.4 Protists
 Cercozoans have thin pseudopods and
elaborate shells (continued).
• The shells of foraminiferans are made of
calcium carbonate (chalk) that are pierced by
many holes through which the pseudopods
extend.
• The chalky shells of these organisms may
accumulate over millions of years to form
deposits of limestone.
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16.4 Protists
 Foraminiferans
Fig. 16-13
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16.4 Protists
 Amoebozoans inhabit aquatic and terrestrial
environments.
• This group moves by extending finger-shaped
pseudopods; they don’t have shells and are
composed of the amoebas and the slime
molds.
• Amoebas are predators that stalk and engulf
prey.
• The dysentery-causing amoeba multiplies in
the intestinal wall, triggering severe diarrhea.
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16.4 Protists
 Amoebas
Fig. 16-14
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16.4 Protists
 Amoebozoans inhabit aquatic and terrestrial
environments (continued).
• Slime molds are decomposers that inhabit the
forest floor.
• The life cycle goes through two phases: a
mobile feeding stage, and a stationary
reproductive stage called a fruiting body.
• There are two kinds of slime molds: acellular
and cellular.
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16.4 Protists
 Acellular forms: the organism is a single
mass of cytoplasm that may spread over an
area of several square yards; this structure
is called a plasmodium
• Dry conditions stimulate the formation of a
fruiting body, which has haploid spores.
Fig. 16-15
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16.4 Protists
 Green algae live mostly in ponds and lakes.
• Some forms are small and live in freshwater,
such as Spirogyra, which forms thin filaments
from long chains of cells.
Fig. 16-16
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16.4 Protists
 Green algae live mostly in ponds and lakes
(continued).
• A marine example, Ulva, or sea lettuce, has
leaves the size of lettuce leaves.
• Green algae are important because it is
believed that they were ancestral to the
earliest plants.
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16.5 Plants
 What are some of the properties that
distinguish plants from other organisms?
• Plants have chlorophyll for photosynthesis.
• Plant reproduction features alternation of
generations.
• Plants have dependent embryos.
• Plants have roots or rootlike structures that
anchor it and absorb water and nutrient from
the soil.
• Plants have a waxy cuticle that covers the
surface of leaves and stems, limiting water
loss.
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16.5 Plants
 Two major groups of land plants arose from
ancient algal ancestors: the nonvascular
plants and the vascular plants.
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16.5 Plants
 Nonvascular plants lack conducting
structures, true roots, leaves, or stems.
• They have rhizoids that anchor the plant and
bring water and nutrients into the plant body
• Body size is limited due to the lack of
conducting tissues, and slow diffusion must
distribute water and nutrients throughout the
plant body.
• Nonvascular plants include the hornworts,
liverworts, and mosses.
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16.5 Plants
 Nonvascular plants
Fig. 16-17
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16.5 Plants
 The reproductive structures of nonvascular
plants are protected.
• An adaptation to terrestrial life is their
enclosed reproductive structures, which
prevent the gametes from drying out.
• There are two types of structures, one in
which eggs develop and one in which sperm
are formed.
• In all vascular plants, the sperm must swim to
the egg through a film of water.
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16.5 Plants
 Vascular plants have conducting vessels
that also provide support.
• The conducting cells of vascular plants are
called vessels, which contain lignin that serve
support and conducting functions.
• Vascular plants can grow tall because of
vessels, both because of the support these
structures provide as well as the conducting of
water and nutrients between the roots to the
leaves.
• There are two groups of vascular plants: the
seedless vascular plants and the seed plants.
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16.5 Plants
 Seedless vascular plants include the club
mosses, horsetails, and ferns.
• These plants require swimming sperm and
water for reproduction.
• They propagate by spores, not seeds.
• Their ancestors were larger than present-day
forms, and they dominated the landscape
hundreds of millions of years ago.
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16.5 Plants
 Seedless vascular plants
Fig. 16-18
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16.5 Plants
 Seed plants dominate the land, aided by two
important adaptations: pollen and seeds.
• Pollen grains are tiny structures that carry
sperm-producing cells.
• Pollen grains are dispersed by wind or by
animal pollinators, such as bees.
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16.5 Plants
 Seeds
• Analogous to the eggs of birds and reptiles,
seeds consist of an embryonic plant, a supply
of food for the embryo, and a protective outer
coat.
• The seed coat keeps the embryo in a state of
suspended animation until conditions are good
for growth.
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16.5 Plants
 Seed plants are grouped into two general
types: gymnosperms, which lack flowers,
and angiosperms, the flowering plants.
• Gymnosperms evolved earlier than the
flowering plants.
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16.5 Plants
 One group, the conifers, include the pines,
firs, spruce, hemlocks, and cypresses that
are still very abundant on our planet today.
Fig. 16-19a
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16.5 Plants
 The other group of gymnosperms, such as
the ginkgos and cycads, have declined to a
small remnant of their former range and
abundance.
Fig. 16-19b,c
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16.5 Plants

Angiosperms are flowering seed plants.
•
Three major adaptations have made
angiosperms so successful as plants.
1. Flowers: contain male and female parts of
the plant; are used to attract insects as
pollinators
2. Fruits: encourage animals to eat the fruit,
which contains the fertilized seed of the
plant, thus dispersing the plant
3. Broad leaves: collect more sunlight for
photosynthesis
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16.5 Plants
 Flowering plants
Fig. 16-20
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16.5 Plants
PLAY
Animation—Evolution of Plant Structure
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16.6 Fungi
 Fungi have distinctive adaptations.
• A typical fungus is a mushroom, which is
actually the reproductive part of a more
extensive organism.
• Fungi feed off dead material by secreting
digestive fluids that break down their food
outside of their bodies.
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16.6 Fungi
 Fungi have distinctive adaptations
(continued).
• The body of a fungus is called a mycelium and
is one-cell thick.
• The mycelium is
made up of
extensive numbers
of filaments called
hyphae, which
grow across a
food source.
hyphae
(a) Mycelium
(b) Hyphae
Fig. 16-21
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16.6 Fungi
 Most fungi can
reproduce both
sexually and
asexually.
• Fungi reproduce by
spores that are cast
to the wind.
Fig. 16-22
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16.6 Fungi
 Most fungi can reproduce both sexually and
asexually (continued).
• Fungi can reproduce both asexually and
sexually.
• Sexual reproduction is reserved for periods of
environmental change or stress.
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16.6 Fungi
 Fungi affect humans and other organisms.
• Fungi play a major role in the destruction of
dead plant tissue by being able to digest both
lignin and cellulose, the molecules that make
up wood.
• Fungi are saprophytes (feeding on dead
organisms) and consume the dead of all
kingdoms.
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16.6 Fungi
 Fungi affect humans and other organisms
(continued).
• The activities of fungi and bacteria return
nutrients and minerals to the environment.
• Antibiotics—such as penicillin, oleandomycin,
and cephalosporin—are made from fungi to
combat bacterial diseases.
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16.6 Fungi
 Fungi make important contributions to
gastronomy.
• The fungi we consume directly, such as wild
and cultivated mushrooms, make important
contributions to human nutrition.
Fig. 16-23
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16.6 Fungi
 Fungi make important contributions to
gastronomy (continued).
• The world’s most famous cheeses—including
Roquefort, Camembert, Stilton, and
Gorgonzola—gain their distinct flavors from
molds that grow on them as they ripen.
• Other foods and beverages that depend on
yeasts for their production are bread, wine,
and beer.
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16.6 Fungi
 Fungi attack plants that are important to
people.
• Fungi cause the majority of plant diseases,
and some of the plants that the infect are
important to humans.
• Especially damaging are plant pests called
rusts and smuts, which cause billions of
dollar’s worth of damage to grain crops
annually.
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16.6 Fungi
 Corn smut
Fig. 16-24
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16.6 Fungi
 Fungi include parasites that attack humans
directly.
• Some of these are athlete’s foot, jock itch,
vaginal infections, and ringworm.
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16.6 Fungi
 Fungi can produce toxins.
• Molds of the genus Aspergillus produce highly
toxic, carcinogenic compounds known as
aflatoxins.
• Some foods, such as peanuts, seem to be
especially susceptible to attack by Aspergillus.
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16.7 Animals
 Characteristics of animals
• Animals are multicellular.
• Animals get their energy by consuming other
organisms.
• Animals reproduce sexually.
• Animal cells lack a cell wall.
• Animals are mobile.
• Animals react rapidly to external stimuli.
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16.7 Animals
 For convenience, animals are categorized
as either vertebrates (with backbones) or
invertebrates (without backbones).
• Sponges have a simple body plan, lack
tissues or organs, and are colonies of singlecelled organisms.
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16.7 Animals
 Sponges
Fig. 16-25
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16.7 Animals
 Sponges (continued)
• Water enters through numerous tiny pores in
the body, and leaves through fewer, large
openings.
• Oxygen and food is filtered out of the water
during passage.
• Reproduction can be asexual through
budding, or sexual by the release of eggs and
sperm into the water.
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16.7 Animals
 Cnidarians are well-armed predators.
• Representatives are jellyfish, corals, and sea
anemones.
Fig. 16-26
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16.7 Animals
 Cnidarians are well-armed predators
(continued).
• Their body parts are arranged in a circle
around the mouth and digestive cavity.
• Tentacles are armed with stinging cells that
inject poison into prey and kill it so that it can
be eaten.
• Corals form a large calcium carbonate
skeleton that can build up over long periods of
time and last long after the animal that built it
has died.
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16.7 Animals
 Annelids are composed of identical
segments.
• An example is earthworms with segmented
bodies.
• Internally, most of the segments contain
identical copies of nerves, excretory
structures, and muscles.
• Representatives are oligochaetes
(earthworms), polychaetes (marine worms),
and leeches.
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16.7 Animals
 Annelids
Fig. 16-27
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16.7 Animals
 Most mollusks have shells.
• Snails and slugs are collectively called
gastropods—they crawl on a muscular foot,
and many are protected by shells.
• Sea slugs lack shells.
• Gastropods feed with a radula, a flexible
ribbon of tissue with spines that scrape algae
off rocks.
• A few gastropod species live on land and use
a simple lung for breathing.
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16.7 Animals
 Gastropod mollusks
Fig. 16-28
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16.7 Animals
 Bivalves are filter feeders.
• Scallops, oysters, mussels, and clams are
bivalves.
• Bivalves have two shells connected by a hinge.
Fig. 16-29
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16.7 Animals
 Bivalves are filter feeders (continued).
• They use a muscular foot for burrowing in
sand or mud.
• Scallops lack a foot and move by jet
propulsion, achieved by flapping their shells
together.
• Water is circulated over the gills, which are
covered with mucus that traps food particles
and conveys them to the mouth.
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16.7 Animals
 Cephalopods are marine predators.
• All cephalopods are predatory carnivores, and
all are marine.
• Their foot is developed into tentacles that are
used for detecting and grasping prey.
• This group has highly developed brains and
sensory systems.
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16.7 Animals
 The cephalopods include octopuses,
nautiluses, cuttlefish, and squids
Fig. 16-30
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16.7 Animals
 Arthropods are the dominant animals on
Earth.
• The Arthropoda includes the insects,
arachnids, and crustaceans.
• They all have an exoskeleton; in insects, the
body is divided into three parts: head, thorax,
and abdomen.
• Insects are the only flying invertebrates.
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16.7 Animals
 Insects
Fig. 16-31
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16.7 Animals
 Arthropods are the dominant animals on
Earth (continued).
• During their development, insects undergo
metamorphosis, a radical change from a
juvenile body form to an adult body form.
• The immature stage of the insect is referred to
as a larva, which grows until it reaches
maximum size.
• It then forms a nonfeeding stage called a pupa.
• An adult emerges from the pupa.
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16.7 Animals
 Most arachnids are predatory meat eaters.
• They have eight walking legs and are
carnivorous, feeding on a liquid diet of blood
or predigested prey.
• Spiders produce silk from special glands in
their abdomens, which they us to build webs
to capture prey and to wrap up the prey once
it is caught.
• Spider silk is amazingly strong; it can be
stronger than steel wire of the same size, but
is as elastic as rubber.
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16.7 Animals
 The arachnids include spiders, mites, ticks,
and scorpions.
Fig. 16-32
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16.7 Animals
 Most crustaceans are aquatic.
• The crustaceans include crabs, crayfish,
lobster, shrimp, and barnacles; they only live
in the water.
• Crustaceans have two pairs of sensory
antennae, but the remaining appendages vary
with habitat and lifestyle of the species.
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16.7 Animals
 Crustaceans
Fig. 16-33
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16.7 Animals
 The chordates include both invertebrates
and vertebrates.
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16.7 Animals
 All chordates have the following features.
• The notochord: a stiff, flexible rod that extends
the length of the body and provides
attachment for muscles
• The nerve cord: a dorsal hollow tube; one end
becomes the brain during development
• Pharyngeal gill slits: these may develop into
functional gills or just remain as grooves in
early development
• A post-anal tail: extends beyond the body, past
the anus
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16.7 Animals
 The invertebrate
chordates live in the
seas.
• The invertebrate
chordates are the
lancelets and the
tunicates.
Fig. 16-34
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16.7 Animals
 The invertebrate chordates live in the seas
(continued).
• Larvae of lancelets lack a backbone, but the
adults possess all four chordate features.
• The tunicates (sea squirts) have a larva that
swims and has all chordate features.
• Adults are attached to the sea bottom and do
not move.
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16.7 Animals
 Vertebrates have a backbone.
• In vertebrates, the embryonic notochord is
normally replaced during development by a
backbone, or vertebral column.
• Vertebrates are represented by fish,
amphibians, reptiles, birds, and mammals;
there are more ray-finned fishes than any of
the other vertebrate groups.
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16.7 Animals
 Ray-finned fishes
Fig. 16-35
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16.7 Animals
 Ray-finned fish are an important food
source for humans.
• Overfishing has sharply reduced the size of
the fish populations in the oceans today; some
fish species have been reduced to 10% of
their numbers when commercial fishing
started.
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16.7 Animals
 The amphibians straddle the boundary
between aquatic and terrestrial existence.
• Amphibians have a three-chambered heart.
• Amphibian lungs are poorly developed and
have to be supplemented by skin respiration.
• Amphibians are tied to the water for
reproduction; many undergo metamorphosis
with aquatic larval forms and terrestrial adults.
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16.7 Animals
 Amphibians
Fig. 16-36
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16.7 Animals
 The reptiles include lizards, snakes, turtles,
alligators, and crocodiles.
• Many species are completely independent of
water as a result of three adaptations:
• Evolution of a tough, scaly skin that resists
water loss and protects the body
• Evolution of internal fertilization
• Evolution of a shelled egg
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16.7 Animals
 Reptiles
Fig. 16-37
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16.7 Animals
 One very distinctive group of reptiles is the
birds.
• Birds have developed feathers, which are
highly specialized versions of reptilian body
scales.
• Modern birds retain scales on their legs,
evidence of the ancestry they share with the
reptiles.
• Birds have hollow bones for flight, and
produce a shelled egg.
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16.7 Animals
 Birds
Fig. 16-38
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16.7 Animals
 One branch of reptiles gave rise to a group
that evolved hair and diverged to form the
mammals.
• Mammals are named for the milk-producing
mammary glands used by female members of
the group to suckle their young.
• In most mammals, fur protects and insulates
the warm body.
• The mammals are divided into three groups:
montremes, marsupials, and placentals.
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16.7 Animals
 Monotremes are found only in Australia and
New Guinea, and include the platypus and
two species of spiny anteaters, also known
as echidnas.
 Monotremes lay eggs.
Fig. 16-39a
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16.7 Animals
 All mammals except monotremes have
embryos that develop in the uterus of the
female reproductive tract.
• In marsupials, embryos are only in the uterus
for a short time and are then born at a very
immature stage of development.
• Immediately after birth, they crawl to a nipple,
firmly grasp it, and complete their
development.
• In many marsupial species, this postbirth
development takes place in a protective
pouch.
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16.7 Animals
 Marsupials
Fig. 16-39b
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16.7 Animals
 Most mammal species are placental
mammals.
• Compared to marsupials, placental mammals
retain their young in the uterus for a much
longer period, so that offspring complete their
embryonic development before being born.
• The bat, mole, impala, whale, seal, monkey,
and cheetah exemplify the radiation of
mammals into nearly all habitats, with bodies
adapted to their varied lifestyles.
• The largest group of placental mammals are
the bats and rodents.
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16.7 Animals
 Placental mammals
Fig. 16-39c,d
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