Chapter 11: Animal Diversification
Visibility in motion
Lectures by Mark Manteuffel, St. Louis Community College
Learning Goals




Define an animal and the key distinctions
that divide the species.
Discuss evolutionary success.
Define and describe vertebrates and their
evolution.
Define and describe the terrestrial
vertebrates, including amphibians, birds,
and mammals.
Learning Goals



Describe early human lifestyles and
human evolution.
Define and describe the invertebrates,
including echinoderms, arthropods,
molluscs, annelids, flatworms, cnidarians,
and sponges.
Are some animals smarter than others?
11.1 What is an animal?
Three Key Characteristics
Take-home message 11.1
Animals are organisms that share three
characteristics:
1) All of them can move during at least one
stage of development.
2) All of them eat other organisms.
3) All of them are multicellular.
11.2 Four key distinctions
divide the animals.
1) Does the animal have defined
tissues, with specialized cells?
2) Does the animal develop with
radial symmetry or bilateral
symmetry?
A body structured like a pie
or
A body with a left and right side,
which are mirror images
3) During development, does the
animal’s gut develop from front to
back or back to front?
Protostomes
and
Deuterostomes
4) Does growth occur by molting or
by adding continuously to the
skeletal elements?
Take-home message 11.2
 The
animals probably originated from an
ancestral protist.
 Four key distinctions divide the extant
animals:
1)
2)
3)
4)
tissue or not
radial or bilateral symmetry
protostome or deuterostome development
growth through molting or not
11.3 Everything that is not
extinct is evolutionarily
successful.
What is “success” evolutionarily?
Extant or Extinct
Take-home message 11.3
 From
an evolutionary perspective, all
extant species are successful.
 However,
some groups are represented
by more species than others.
 Among
the 36 animal phyla, 9 phyla
account for more than 96 percent of all
described animal species.
11.4 All vertebrates are members
of the phylum Chordata.
Four distinct
features of
chordates
The Notochord

A rod of tissue extending from the head to
the tail

Stiffens the body when muscles contract
during locomotion

In advanced chordates
• present only in early embryos
• replaced by the vertebral column (backbone)
A Dorsal Hollow Nerve Cord
 Extends
from head to tail
 In
vertebrates, forms the central nervous
system (spinal cord and brain)
 In
other animals, lies in lower portion of
ventral part of body (and is solid instead
of hollow)
Pharyngeal Slits
 Pharyngeal
region
• the area between the back of the mouth and
the top of the throat
 Pharyngeal
slits are present in the
embryos of all chordates.
 Originally
used for breathing and feeding
A Post-Anal Tail
 extends
back beyond the end of the trunk
The phylum Chordata contains
three sub-phyla:
The Most Diverse Subphylum of
Chordates
Take-home message 11.4
All chordates have four structures:
1)
2)
3)
4)
a notochord
a dorsal hollow nerve cord
pharyngeal gills slits
a post-anal tail
Take-home message 11.4
 The
three subphyla of chordates are very
different
• but all possess these four characteristics,
• although some reveal those characteristics
only during specific life stages.
11.5 The evolution of jaws and
fins gave rise to the vast
diversity of vertebrate species.
The evolution of fins paralleled the evolution of
jaws because the two structures work together.
Fins get you to the organism you are
going to eat.
Jaws capture and kill it.
Take-home message 11.5
 The
development of two structures—fins
and jaws—set the stage for the enormous
diversity of modern vertebrates.
11.6 The movement onto land
required lungs, a rigid backbone,
four legs, and eggs that resist
drying.
Take-home message 11.6

In the transition of vertebrates from life in
water to life on land:
• fins were modified into limbs
• vertebrae were modified to transmit the body
weight through the limbs to the ground
• the site of gas exchange was transferred from
gills to lungs
Take-home message 11.6
 The
only entirely new feature to appear in
the early development of terrestrial
vertebrates was an egg that resisted
drying out.
11.7 Amphibians live a double life.
Take-home message 11.7
 Amphibians
are terrestrial vertebrates
(tetrapods), but most species still lay eggs
in water and the eggs hatch into aquatic
larvae (tadpoles).
11.8 Birds are reptiles in
which feathers evolved.
Feathers
Take-home message 11.8
 Birds
 The
are a branch of the reptile lineage.
complex systems that we see in living
animals are the products of hundreds of
millions of years of step-by-step changes
that began with simple structures.
Take-home message 11.8
 The
function of a structure when it first
appeared was probably quite different
from its current function.
 Feathers
were originally colorful structures
used for behavioral displays. Their current
uses—as insulation and in flight—
developed later.
11.9 Mammals are animals that
have hair and produce milk.
Are all mammals viviparous?
 Viviparity—giving
than laying eggs
 Monotremes
milk.
birth to babies rather
lay eggs, but also produce
Take-home message 11.9
 The
presence of hair and lactation are
defining characteristics of mammals.
Take-home message 11.9

Monotremes are egg-laying mammals.

Marsupial mammals have a pouch in which
the baby completes its development.

Placental mammals have a placenta that
provides oxygen and nutrients to embryos.
11.10 Humans tried out
different life styles.
Chimpanzee and
Modern Human Lineages
 Separated
only 5 or 6 million years ago
Humans differ from chimpanzees in
three major anatomical characteristics:
 Humans
are bipedal.
 Humans
are bigger than chimpanzees.
 Humans
have a brain that is about three
times the size of the brain of a
chimpanzee.
What are the advantages of
walking on two feet rather
than four?
Take-home message 11.10
 Humans’
forward-looking eyes, hands and
feet with ten fingers and ten toes, and
shoulder and elbow joints that allow the
arms to rotate are characteristics we
retain from our arboreal ancestors.
Take-home message 11.10
 The
early ancestors of humans, however,
left the trees and took up life on the
ground where they walked on two legs.
 Our
success can be traced to an increase
in brain size combined with a generalized
body form and a diet that included both
animals and plants.
11.11 How did we get here?
The last 100,000 years of human
evolution
Were there ever two species of
humans alive at the same time?
What happened?
Neandertals,
Homo neanderthalensis
 About
the same size as modern humans
 More
robust and muscular
 Lived
in organized groups
 Probably
hunted large mammals
The Indo-Australian Archipelago
 Homo
erectus
 Homo
floresiensis
Take-home message 11.11
humans (Homo sapiens) evolved
in Africa between 200,000 and 100,000
years ago, and all living humans are
descended from that evolutionary
radiation.
 Modern
Take-home message 11.11
 About
100,000 years ago a small group of
modern humans moved out of Africa, and
the descendants of this group ultimately
populated Europe, Asia, and the Americas.
 Three
other species of humans were living
at this time.
Take-home message 11.11
 Other
human species became extinct
between 30,000 and 12,000 years ago,
after modern humans had spread into the
areas where they were living.
11.12 Invertebrates are the
largest and most diverse group
of animals.
Take-home message 11.12
 Invertebrates,
defined as animals without
a backbone, are the largest and most
diverse group of animals, comprising 96%
of all the living species of animals.
 The
invertebrates are not a monophyletic
group, however, and include protostomes
and deuterostomes.
11.13 Echinoderms are
vertebrates' invertebrate
relatives
Sea stars, sea urchins, and sand dollars
Evolutionary Specialization
 Radial
 An
symmetry in adults
evolutionary specialization associated
with their locomotor mode and feeding
specializations
Echinoderms and Chordates
 Bilateral
symmetry in larvae
 The
larvae have anatomical characteristics
in common with the larvae of primitive
chordates.
 Echinoderms
and chordates are each
other’s closest relatives.
Take-home message 11.13
 Echinoderms
are deuterostomes like
chordates, but they lack backbones.
 Their
aquatic larvae are bilateral and share
some anatomical features with chordates,
but adult echinoderms are radially
symmetrical.
11.14 An external skeleton and
metamorphosis produced the
greatest adaptive radiation ever.
Mammals get bigger and
bigger the more they eat.
Why don’t insects?
Take-home message 11.14
 The
arthropods are protostome
invertebrates, including the insects.
 The
life cycle of most insects includes a
larval stage, which is devoted to feeding
and growth, and an adult stage, in which
the insect reproduces.
Take-home message 11.14
 This
separation of life stages has
contributed to the enormous ecological
diversity of insects.
 It
has also produced remarkable
specializations among the nearly 1 million
species of insects that have been named.
11.15. Other arthropods
include arachnids, crustaceans,
millipedes, and centipedes.
Arachnids
 Land-dwelling
arthropods
 Include
spiders, scorpions, mites, and ticks
 Usually
have four pairs of walking legs
• and a specialized feeding apparatus
 Only
have legs on the thorax
Spider Venom
 Arachnids
 Black
are predators
widow spider
 Brown
recluse spider
Scorpions
 Being
stung by most scorpions is no worse
than being stung by a bee
 Nocturnal
predators of insects
The Crustaceans
• Lobsters, crayfish, crabs, and shrimps
• All have five pairs of appendages extending
from their heads
• Many pairs of legs modified for many
purposes
• Most are aquatic
Millipedes and Centipedes
• “A thousand feet” and “a hundred feet”
• Long segmented bodies
• Millipedes feed on decaying plant material
• Centipedes are predators—use venomous
fangs to kill insects and even small mammals
Take-home message 11.15

Spiders and scorpions are arthropods that eat
insects and occasionally small vertebrates.

Lobsters, crabs, shrimps, and barnacles are
predatory marine crustaceans.

Centipedes are predators with fangs that
inject venom, while millipedes are herbivores
that feed on dead plant material.
11.16 Most molluscs live in shells.
The Three Major Groups of
Mulluscs
1) Gastropods
2) Bivalve molluscs
3) Cephalopods
Gastropods
 Snails
and slugs are called gastropod
molluscs.
 “Belly
 Found
foot”
in both aquatic and terrestrial
environments, snails and slugs account for
three-quarters of all molluscs.
Bivalve Molluscs
 Clams,
scallops, oysters, and mussels have
a pair of shells that clamp together.
 Roughly
8000 species of bivalve—most of
them live in the ocean.
 All
are filter feeders.
Cephalopods
Take-home message 11.16
 Molluscs
are protostome invertebrates that
do not molt.
 Including
the snails and slugs, clams and
oysters, and squid and octopuses, the
molluscs are the second most diverse
phylum of animals.
Take-home message 11.16
 Most
feature a shell for protection, a
mantle of tissue that wraps around their
body, and a specialized tongue called a
radula.
11.17 Are some animals
smarter than others?
Are octopuses smart?
Take-home message 11.17

The predatory behavior of octopuses involves
exploration and manipulation

These behaviors are considered as intelligent by
humans, but the concept of intelligence cannot be
applied objectively to other species.

Rather, species should be viewed as having
evolved in response to the selective forces
relevant only to their own particular environments.
11.18
Segmented
worms,
flatworms, and
roundworms
come in all
shapes and
sizes.
Polychaetes
 Marine
worms
 “Many
bristles”
 Some
are burrowing
 Some
are tube dwelling
Earthworms
 “Few
 Bulk
bristles”
feeders
• consume particles of soil and organic material
 Castings
are valued by gardeners
Leeches
 The
saliva of blood-sucking leeches
contains an anticoagulant substance that
prevents blood from clotting.
 Not
all leeches are blood suckers.
• More than half the species of leeches are
predators.
Roundworms
Take-home message 11.18
 Worms
fall into several different phyla and
are not a monophyletic group.
 All
are bilaterally symmetrical protostomes
with defined tissue.
 The
segmented worms (annelids) and
flatworms do not molt, whereas the
roundworms do.
Take-home message 11.18
 Earthworms
play an important role in
recycling dead plant material.
 Roundworms
are often parasites of plants
or animals and are responsible for several
widespread human diseases.
 Flatworms
include parasitic flukes and
tapeworms, many of which infect humans.
11.19 Jellyfish and other
cnidarians are among the most
poisonous animals in the world.
Cnidarians
 Two
types of cnidarian bodies:
• a sessile polyp
• a free-floating medusa.
 Reproduce
both sexually and asexually
 Carnivores
that use cnidocysts
• stinging cells
Although all cnidarians possess
cnidocytes, there is great diversity
among the three major groups.
 Jellyfish
 Sea
anemones
 Corals
How is global warming affecting
the coral reefs of the world?
Take-home message 11.19
 Jellyfish,
sea anemones, and corals are
radially symmetrical animals with defined
tissue, from the phylum Cnidaria.
 All
cnidarians are carnivores and possess
specialized stinging cells located in
tentacles to capture prey.
11.20 Sponges are animals
that lack tissues and organs.
Take-home message 11.20
 Sponges
are among the simplest of the
lineages of animals.
A
sponge consists of a hollow tube with
pores in its wall, it has no tissues or
organs, and only three kinds of cells.
Take-home message 11.20
 Sponges
reproduce asexually (by budding)
and sexually by producing eggs and
sperm.
 The
fertilized eggs grow into freeswimming larvae that settle and
metamorphose into sessile adult sponges.