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Phylum Cnidaria and Phylum
Ctenophora
Animal Diversity & Morphology
What is diversity?
→Classifying animals into species, orders, phyla, etc
...
green lettuce sea slug
Class Gastropoda - Pulmonata
Besides sea slugs, there are obviously land slugs
These slugs evolved from lung-having land snails that lost their shell
There are even semi-slugs alive today that show what an intermediate slug
ancestor would have looked like on the way to becoming a slug

Class Bivalvia - Ship Worms
Shipworms are not worms at all
They are actually bivalves that have massively re-shaped their shells into
an elongated tube
Shipworms digest wood through the help of symbiotic bacteria that can
break it down, similar to termites

Class Cephalopoda
Octopuses, squids, cuttlefish, and nautiluses

All marine, all active predators*
→ Except vampire squids
Besides nautilus, all have a reduced or lost shell
Part of the foot formed into a funnel/siphon in a cephalopods that allows
the animal to rapidly expel water from its mantle and jet away
Cephalopods have the highest mobility of all molluscs
Cephalopods are active hunters due to their fast moving, fast grabbing
feeding tentacles
Tentacles are different from arms
Octopuses have 8 arms
Squids have 8 arms and 2 tentacles
Cuttlefish have 8 arms and 2 tentacles
Nautiluses have a MESS of tentacles
Cephalopods use chromatophores to change color

Phylum Arthropoda
Arthropods Have a Cuticle

What are the ecological advantages of a cuticle and tough exoskeleton
Protection from predators like we saw with shellies
Lightweight compared to heavy calcareous shell, so mobility isn’t
impacted
Prevents water loss
How do the habitats of arthropods compare to our previous phyla?
Arthtopods are found in ALL habitats! Not just water or moist
terrestrial areas
Arthropods must molt their exoskeleton to grow in size
One disadvantage of this tough body covering is how vulnerable arthropods
are right after molting
Their new procuticle is soft until it hardens up
On the plus side, they can eat the molted skeleton for nutrients if they want
to

Diagnostic Morphology for Arthropods
The appendages and mouthparts formed by the exoskeleton are used to
figure out what kind of arthropod an individual is
There is some disagreement still about which is better for separating
evolutionary groups
The phylogeny we’ll use supports the mandibulate hypothesis
→This is the idea that the mandible evolved early on and diversified
among myriapods, crustaceans, and hexapods

Subphylum Trilobite
Famous fossil
Extinct for hundreds of millions of years, but was widespread and
successful in its day
Sister taxon to modern arthropods(possibly closely related to chelicerates?)

Subphylum Chelicereta
Includes arachnids like ticks, mites, spiders, and scorpions along with
marine species like horseshoe crabs and sea spiders
8 legs
Chelicerae and pedipalps on their head, but NO mandibles or antennae

Class Merostomata: Horseshoe Crabs
Horseshoe crabs represent an ancient lineage that only has 5 extant
species now
Their tough shell protection has been a good evolutionary strategy against
predators
That long scary-looking telson tail is only for flipping itself over
Their blue blood contains Limulus Amebocyte Lysate(LAL) detects bacteria
on medical equipment and substances

Class Pycnogonida: Sea Spiders
Similar to seahorses, the male sea spiders carry the fertilized eggs until
they hatch
They have special legs called ovigers to carry them on

Class Arachnida: Regular spiders
This class has 2 tagma with a cephalothorax and the abdomen
All spiders are predaors
Some spiders will chase down their prey
Others lay in wait to ambush prey
The third option is trapping prey in a silk web
Except for a few cases, spider venom is only deadly to its insect prey and
not a big threat to humans
Venom can be neurotoxic (attacks nervous system) or hemolytic
(damages tissues)

Class Arachnida: Order Scorpionida
Tagma include cephalothorax, segmented pre-abdomen, and tail-like
post-abdomen
Also capable of producing venom delivered through tail

Class Arachnida: Order Opiliones
“Daddly Long Legs” or “Harvestmen”
NOT spiders
Segmented abdomen that’s not separated from cephalothorax by a
waistline
Chew their food with pedipalps rather tan liquefying it with venom
from fangs
Scavengers instead of predators

Class Arachnida: Order Acari
Includes ticks, like those that spread Lyme disease in the US
Also includes mites like the tiny Demodex which live in most of our hair
follicles
This is the only set of arachnids with no separation or segmentation in their
body plan

Subphylum Myriapoda
Includes millipedes and centipedes
“Myriapoda” = many feet
Mandibles, antennae, and 2 tagmate (head and trunk)
Lost compound eye, simpler ocelli for vision instead

Class Chilopoda: Centipedes
Predators
Up to 177 segments, each with a pair of legs
Class Diplopoda: Millipedes
Herbivores or detrivores
25-100 segments, with most having 2 pars of legs each

Diagnostic Features of Arthropods
Mandibles appear to have evolved once and serve as a better indicator of
phylogenetic relatedness
→ Mandibulate hypothesis
Uniramous vs
...
Deap sea giant isopod
Many isopods are parasites

Subclass Pentastomida
Worm-like Parasites
Hard to believe they belong with other crustaceans

Subclass Branchiura
Another crustacean parasite
Branchiurids are also called “fish lice”

Subclass Thecostraca
Another surprising crustacean → barnacles

Barnacles are sessile and use their long feathery cirri to suspension feed

Planktonic Crustaceans
Other crustaceans rely on filtering particles from water
Usually small plankton like copepods, ostracods, and cladocerans
The largest crustacean (and arthropod) is the Japanese spider crab

Similarities Between Insects and Crustaceans
Both have ommatidia to create compound eyes for vision
Both go thorough body changes during development
The insect metamorphosis is more extreme

Wings are what separate Class Insecta
Wings are an ancestral trait for insects wings have been lost in some
groups later like lice, bedbugs, fleas, and some ants and termites
How have wings influences the evolution and diversity of insects?
Wings have allowed insects to spread to all habitats and sped up
speciation to create the most diverse group of animals in Class Insecta

Phylum Chordata
Phylum Chordata
All vertebrates are chordates
Not all chordates are vertebrates

Hence the Phylum Chordata and Subphylum Vertebrate
Today is about that spineless area in between

Chordates Have a Notochord
Vertebrates reinforce the notochord with a spinal column
All chordates have
A dorsal hollow nerve cord
A supportive notochord underneath the nerve cord
Pharyngeal pouches or slits
An endostyle for filter feeding
A postanal tail for propulsion
Most don’t have all of them as an adult*
*Exceptions:
Phylum Chordata - Subphylum Cephalochordata (Amphioxus)
Phylum Chordate - Subphylum Urochordata (tunicates, AKA sea
squirts)

Fishes
Technically we come from the same ancestor
“Fishes” includes all descendants of the same ancestor except for
tetrapods
“Hagfish” is a monophyletic term that includes all descendants from one
ancestor

“Shellfish” is a polyphyletic term that includes some descendants from
different ancestors like crabs (but not all crustaceans) and clams (but not all
molluscs)

Evolution of Fishes
Tetrapods are grouped into Sarcopterygians, so our closest fish relatives
are lungfishes and coelacanths
The most diverse group of fishes today (and ever) is modern bony fishes
The next most diverse group is the cartilaginous fishes (Chondrichthyes)
that include sharks, rays, and chimaeras

Cyclostomata - Jawless fishes
The most ancestral living fishes are agnathans (“a” meaning no and
“gnath” meaning jaw)
Descended from a common chordate ancestor with vertebrae, cerebellum,
myelinated nerves, and eye lenses
Lamprey have these features still today
Hagfish lost these features but show similar development as embryos

Hagfishes: Myxini
Hagfish depend on their sense of smell to find dead animals at the bottom
of the ocean to feed on
Hagfish are common visitors at whale falls (sites where a dead whale falls
to the deep ocean and provides a banquet of food)

Mouth has keratinized plates (same protein as our nails and hair)
Hagfish produce copious amounts of slime
Hagfish slime could be used for textiles

Lampreys: Petromyzontida
About half of all species are parasites

Cyclostomata: Jawless Fishes
No scales protecting the skin
Cartilaginous skeleton
Notochord is present in adults

Osteichthyes: Bony Fishes
Scales
Bony operculum protects gills
Bone replaces cartilage in skeleton
Swim bladder serves as air-filled buoyancy pouch AND the basis for lungs

Teleosts
Most “fish” we commonly think of are teleosts
Found within Osteichthyes (bony fishes)
Within Osteichthyes they’re classified as Actinopterygians (ray-finned
fishes)
Gar and sturgeon are Actinopterygians, but NOT Teleosts

Sarcopterygians
Lobe-finned fishes
Tetrapods
Diphycercal tails on coelocanths and lungfishes

Sarcoptyerigians: Coelocanths
Thought to be extinct until one species was discovered on a tral in 1938
and the other was found for sale at a fish market in the late 90s

S-shaped swimming pattern
Although most fish contract their muscles in S-shaped waves, the tail
does most of the work

Swim bladder used for buoyancy
Swim bladders are filled with gas and also used for gas exchange,
hence used primarily for breathing in lungfish
Bringing up a deep-sea fish is as dangerous to them as the bends are
to us

Amphibians
Amphibians were not the first land animals
Amphibians were the first land tetrapods

Tetra = 4, Pod = foot
This lineage led to the many 4-limbed animals we’re familiar with today,
including ourselves
Luckily, land plants and those other animals were already on land so early
vertebrates had something to eat
Invading land presented the same issues for tetrapods as we discussed for
previous lineages
Preventing the body from drying out
Amphibians avoid this problem by sticking to moist habitats
Keeping the body supported without becoming too heavy in air

Tetrapod Limbs
Tetrapods supported their bodies on land after the lobe fins of
sarcopterygian fish gained more structure with bones and muscles
Tiktaalik is a famous fossil that shows an intermediate body type between a
fish and a land tetrapod
...

They are not all the descendants of a shered tetrapod ancestor
Mammals and birds came from the same ancestor
Are reptiles monophyletic, polyphyletic, or paraphyletic?

Paraphyletic, like fishes
Crocodiles are actually closer related to birds than other nonavian reptiles

Environmental Limitations
Which environments were amphibians limited to?
Amphibians are at risk of drying out if they leave moist environments
High species diversity in rainforests
Completely absent from deserts
Do we find reptiles in different environments?
Yes, reptiles can thrive in the desert
Still successful in rainforests and moist areas too
Still have temperature limits as ectotherms
What adaptations made this possible?
Evolution of the amniotic egg
Scales
Changes in Respiration
Water-conserving excretion

Reptile Amniotic Egg
With protection against dehydration for their eggs, reptiles are no longer
limited to staying close to water sources during their lifetime
The watery environment is encapsulated inside the egg, no longer an
external requirement
Unlike amphibians, reptiles have NO gilled larvae or need for aquatic life
stage

Scales
Adult bodies have to be protected from drying out too
Reptile scales are different than fish scales
Reptiles build scales out of the protein keratin
Fish scales were mostly made of bone
Tough outer layer means
Internal fertilization instead of external fertilization
No more skin respiration
Using keratin to protect the body is a homology among tetrapods

Changes in Respiration
No more skin respiration or gills requires a change in breathing
mechanisms
Amphibians and fish use buccal pumping to push water or air into their
body
When the mouth closes and the floor of the mouth rises, the volume
of the buccal cavity decreases
...

Th only members alive from that clade today are crocodilians (which have
changed very little from the days of the dinosaurs) and birds (which have
diversified widely)

Crocodilia
Crocodiles aren’t the ONLY crocodilians
Caiman
Gharial
Alligator
Crocodiles do have the most widespread distribution and diversity, and
include the largest species in this group(22 foot long saltwater crocodile)

Crocodiles are fearsome predators due in no small part to their impressive
bite force

Birds
Evolutionary History of Birds
As we have already learned, birds are a group of dinosaurs that survived to
today
They have massivey diversified since then
How do we know birds descended from dinosaurs?
Archaeopteryx is a famous fossil that helped solidify the connection

It is not a direct ancestor of modern birds, but it does represent
what the intermediate forms between dinosaurs and birds would have
looked like

Archaeopteryx
Dinosaur traits
Bony tail
Teeth
Abdominal ribs
Clawed fingers
Bird traits
Similar skull shape
Feathers*
*There were also dinosaurs that had feathers but these don’t preserve well
in fossils, so it took a while for scientists to recognize many “scaly” species
probably had feathers

Endothermy in Birds
Reptiles, like all the animals before them we’ve covered, ar exothermic
(“cold-blooded”)
Birds need to be endothermic to keep up with intense metabolic demands
for flight
Many dinosaurs weres endothermic as well to be speedy predators
...
the arctic fox

Sweat glands vs
...
4 billion
Advertising budget of top 10 car manufacturers in 2019→$14 billion
The COVID-19 lockdown gave us an opportunity to see what the impact is
of more of the population staying home, grounding flights, etc
...
But more than that
they are often the masterminds behind propaganda campaigns that make
us think individuals are the cause of and solution to the pollution, climate
change, etc
...
BP invented the term “Carbon Footprint” to shift guilt onto
consumers

Yes, This BP
BP was the company famously responsible for the Deepwater Horizon oil
spill in the Gulf of Mexico in 2010
Releasing over 200 million gallons of crude oil in the deap seaa, this spill
was the worst marine spill in history
Oh, and the dispersant they used to try to clean it up was even worse for
the deep-sea corals in the area

Humans and Nature
Humans are not inherently a problem for nature
The indigenous peoples have lived for thousands of years in harmony
with their environment, stewarding the land for mutual benefit to both
humans and wildlife
However, it is impossible to deny that humans have done great harm to the
environment

Indigenous Knowledge

Unfortunately, Indigenous knowledge is still undervalued in the scientific
community
Another reason we need to diversify STEM is for the future of our
planet

Worms
Phylum Platyhelminthes: Flatworms
These worms are limited in size and shape, and most have parasitic
lifestyles
Their flat shape means they primarily rely on diffusion for exchange with
their environment, and they have no distinct circulatory or respiratory
systems
Simple body plans are easy to regenerate after injury
Tapeworms are so flat and simple that they actually have no digestive tract
The scolex is a ring of hooks that grab onto the inside of our intestines
The proglottids after the scolex are flatt enough to directly absorb nutrients

Proglottids are essentially egg packets that drop off the end of the
tapeworm as a new proglottids grow near the scolex

Phylum Nematoda: Roundworms
Also a small simple body plan, but with more complex organ systems than
flatworms

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