Arthropods, from last
time…Diversity of Arthropoda
Diversity of Arthropoda
Crustacea are the dominant marine
arthropods
Crustacea are the dominant marine
arthropods
Should we call them shellfish?
any terrestrial crustaceans?
sowbugs
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Diversity of Arthropoda
Diversity of Arthropoda
Crustacea Morphology
Uniramia - “one branch”
(unbranched appendages)
- each segment of thorax and
abdomen usually has an
appendage
- appendages may be branched
Includes insects, millipedes,
centipedes
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Diversity of Arthropoda
Diversity of Arthropoda
The insects in particular...
The insects in particular…
- three body sections
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Diversity of Arthropoda
Diversity of Arthropoda
The insects in particular…
The insects in particular…
- three body sections
head, thorax, abdomen
- three body sections
head, thorax, abdomen
- six legs
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Diversity of all described species of
animals
Diversity of Arthropoda
The insects in particular…
B’FLIES
& MOTHS
- three body sections
head, thorax, abdomen
- six legs
- comprise most of the animal species
on the planet
FLIES
73 % INSECTS
OTHER
INSECTS
ANTS,
BEES &
WASPS
OTHER
ARTHROPODS
CHORDATA
BEETLES
OTHER
PHYLA
TRUE
BUGS
12 % OTHER
ARTHROPODS
4%
CHORDATES
11 % ALL
OTHER
PHYLA
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Diversity of Arthropoda
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Why have insects been so evolutionarily
successful?
Insect species
Described species of vertebrates 38,000
Described species of insects - 875,00
And the rate of discoveries of new
insect species suggests that there
are many undescribed - estimates of
2 million to 30 million
i. Small size - habitat becomes more
complex as you become smaller,
allows more subdivision
Even the most conservative estimate
suggests that most insect species have
not been described!
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Diversity of all described species of
animals
Why have insects been so evolutionarily
successful?
i. Small size - habitat becomes more
complex as you become smaller,
allows more subdivision
ii. Flight - more movement and rapid
colonization of plants
B’FLIES
& MOTHS
FLIES
OTHER
INSECTS
ANTS,
BEES &
WASPS
OTHER
ARTHROPODS
CHORDATA
BEETLES
What do these
insect groups
have in
common?
OTHER
PHYLA
BUGS
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iii. Complete
metamorphosis change in body
plan
allows
specialization of
immatures for
feeding and
growth, of adults
for dispersal and
reproduction
Why have insects been so evolutionarily
successful?
i. Small size - habitat becomes more
complex as you become smaller,
allows more subdivision
ii. Flight - more movement and rapid
colonization of plants
iii. Complete metamorphosis - change in
body plan
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Animal diversity 4 - The
Deuterostomes (Echinodermata,
Chordata)
Why have insects been so evolutionarily
successful?
i. Small size - habitat becomes more complex
as you become smaller, allows more
subdivision
ii. Flight - more movement and rapid
colonization of plants
iii. Complete metamorphosis - change in body
plan
Key concepts
• Key morphological characters of the
Echinodermata, Chordata
• Distinguish lineages of vertebrates:
Three lineages of fishes (jawless fishes,
cartilaginous fishes, bony fishes) and three
lineages of terrestrial vertebrates (amphibians,
reptiles [including birds] and mammals)
• Distinguish three groups of mammals
• Secondary evolution of ocean dwelling for
terrestrial animals: the marine mammals
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The Echinodermata: Sea stars, sea
urchins,
The Echinodermata
Examples?
Sea stars, sea urchins, sea cucumbers,
sand dollars
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The Echinodermata: Sand dollars, brittle
stars
The Echinodermata: Sea cucumbers
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The Echinodermata Feeding
The Echinodermata
Predacious (sea stars) or
grazers (sea urchins) or filter
feeders (sea cucumbers,
others)
Morphology
“Pentameric” symmetry as
adults - rays or arms
arranged in groups of 5
(but planktonic larvae
bilaterally symmetrical)
Endoskeleton of
interlocking calcium
carbonate plates covered
by epidermis
Water-filled canal system leads to “tube feet”
for moving or manipulating things - feet can be
extended or retracted with water pressure
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Favorite food
of sea stars is
bivalves like
clams and
mussels - how
do they eat
them?
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The Echinodermata Feeding
The Echinodermata Feeding
How do sea stars eat
bivalves?
Anchor themselves,
both sides of shell
with tube feet, exert
constant pressure,
wear out the
muscles of the
bivalve. Then...
How do sea stars
eat bivalves?
Then, the sea
star everts its
mouthparts and
stomach into the
crack,
consumes the
contents!
Tube
feet
After dinner - everted stomach,
and empty shell
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Last, but hardly least, the Chordata
The Chordata
Chordates = Vertebrates + two small
groups
Tunicates
As adults look like sponges! But larvae have
all the defining features of chordates
- the Tunicates and the Lancelates
What feature
in particular?
Lancelate
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The Chordata Morphology
In vertebrates
- dorsal hollow nerve cord
- notochord (a flexible rod, supporting
the nerve cord) for at least part of life
the notochord disappears early in
development, and is replaced by the
vertebral column that surrounds the
nerve cord
Lancelet
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The general vertebrate body plan
The general vertebrate body plan
Dorsal nervous
system
Dorsal nervous
system
Internal skeleton
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The general vertebrate body plan
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The general vertebrate body plan
Dorsal nervous
system
Internal skeleton
Organs suspended
in coelom
Dorsal nervous
system
Internal skeleton
Organs suspended
in coelom
Well developed
circulatory system
with heart
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Evolution of vertebrates
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Modern jawless fishes - Lampreys and
hagfish
• First vertebrates were likely mud-suckers
• similar in morphology to modern jawless
fishes
• ingested mud, removed organic material
• osmoregulatory* abilities allowed fishes
to exploit estuaries**
Mouth of a
lamprey
*osmoregulatory: control of levels of solutes in
cells (in this case salts)
**estuaries: where salty ocean water and fresh
water mix
Lamprey
feeding
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Second group of fishes - the
cartilaginous fishes
Second (?) group of fishes - the
cartilaginous fishes
Examples?
So named because skeleton made
from cartilage
First real jaws? (some have JAWS)
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Third group of fishes - the bony
fishes
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Third group of fishes - the bony fishes
Most fish are bony fish
Cartilage replaced by bony skeleton
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Third group of fishes - the bony
fishes
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Amphibians - the first vertebrates on
land
evolved lunglike sacs for respiration,
became modified into swim bladders
What are swim bladders used for?
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Amphibians - the first vertebrates
on land
Reptiles - better adapted to dry
land
But - confined to moist habitats:
1) Respire with lungs and across
moist skin
2) Reproduce in the water, have
external fertilization
3) Eggs not waterproof - generally
have to be laid in water (video
segment showing exceptions!)
1) skin
covered with
scales
2) Internal
fertilization
3) Egg with
waterproof shell
- the Amniotes
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One hypothesis for terrestrial
vertebrate phylogeny
The reptiles
MAMMALS
AMNIOTES
REPTILES
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MAMMALS
AMNIOTES
TURTLES
REPTILES
TURTLES
TUATARAS
TUATARAS
LIZARDS &
SNAKES
LIZARDS &
SNAKES
CROCODILIANS
CROCODILIANS
DINOSAURS AND
BIRDS
DINOSAURS (INCL.
BIRDS)
AMPHIBIANS
A tuatara - single
species remaining
of this reptile
lineage
AMPHIBIANS
Birds are reptiles and closely related
to dinosaurs: scales have been
modified into feathers
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REPTILES
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Mammalia
I. What unites us? Hair, milk
producing glands
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Mammalia
Mammalia
i. What unites us? Hair, milk producing
glands
ii. Not many species (4,500 compared to
875,000 species of insects)
Iii. But very diverse morphologically,
ecologically
i. What unites us? Hair, milk
producing (mammary) glands
ii. Not many species (4,500 compared
to 875,000 species of insects)
2g
160,000 kg
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Mammalia
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Mammalia
i. What unites us? Hair, milk producing
glands
ii. Not many species (4,500 compared to
875,000 species of insects)
iii. But very diverse morphologically,
ecologically
iii. And our species has the greatest
impact of any animal on life on this
planet
Three commonly distinguished groups of
mammals
Monotremes - egg laying mammals with
reptilian-like splayed legs. Only 3 spp.:
the Australian platypus and 2 spp. of
echidna
Marsupials - give birth to tiny young,
nursed in ventral pouch - most of 240
spp. in Australia
Eutherian mammals - (= “placental
mammals”) by far the most diverse over 4,000 spp.
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Monotremes - egg laying mammals
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Marsupials - mammals with pouches
Platypus
Echidna
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Evolution of Cetacea (whales,
porpoises and dolphins)
Eutherian mammals - the rest of us
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Evolution of Cetacea (whales, porpoises
and dolphins) Likely evolutionary
sequence
Evolution of Cetacea (whales, porpoises
and dolphins)
How did land mammals adapt to the sea?
Entire transition from land mammal to
marine whale - only 8 million years.
Secondary evolution of ocean dwelling in
animals
Secondary evolution - reacquisition of a
lost trait
New fossils show the closest land-living
relatives to whales are the artiodactyls
(includes hippos, pigs, camels giraffes,
deer, sheep and cattle)
Lived on
land - fed
while
wading
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A later group Reconstruction of the first cetacean
were more
like
crocodiles ambushed
prey in
shallow water
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Evolution of Cetacea (whales,
porpoises and dolphins)
Evolution of Cetacea (whales,
porpoises and dolphins)
A later marine group had a very long
snake-like body, a tail-fluke and
complete, tiny hind-limbs with mobile
knee and toes
Modern Cetacea - nearly 80 species
Hind limb
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Forelimbs modified to form flippers
Nostrils on top of the head - blowhole
Hind limbs do not extend out of body
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