UNIT 13 TARGETS
TARGET 1: ANIMAL BODY PLANS AND PHYLOGENY
1.
Radial symmetry is like a pie; it has no arms or legs and it can be sliced into equal pieces. Examples
include the anemones and jellyfish. Bilateral symmetry is like a banana split; it can be split in half and
have two mirror halves. Examples include humans, bears, and butterflies. Bilateral symmetry allows
for cephalization and streamlining of various bodily systems, especially the nervous system.
2.
Acoelomates have no coelom at all; an example would be a fluke or flatworm. Pseudocoelomates
have a fake coelom that extends from the mesoderm to the gut without a complete covering of
mesoderm; an example would be the nematode. Coelomates have a true coelom which is completely
surrounded by mesoderm. Examples would be humans, annelids and any other animal with a
vertebrate. The coelom is important because an acoelomate is susceptible to any bodily damage if it’s
squished. Having a pseudocoelom is also less efficient because pseudocoelomates have to circulate
waste and nutrients through their body through diffusion because they don’t have a vascular system.
They also don’t have a skeleton and rely on hydrostatic pressure to have structure.
3.
Protostomes develop head-first. They rely on spiral and determinate (dependent cells) cleavage to
develop. The coelom cavities are already formed during gastrulation; the archenteron pushes in while
the coelom elongates. The blastopore becomes the mouth and the resulting gastrula is triploblastic.
The molluscs, the annelids and the arthropods are all protostomes. Deuterostomes develop anus-first.
They rely on radial and indeterminate (independent cells) cleavage to develop. The coelom is formed
through the formation of the archenteron. The blastopore becomes the anus, and the resulting
gastrula is tripoplastic. The Echinodermata and the chordates are all deuterostomes.
4.
Phylogeny has changed with the advent of new molecular data because we are able to check the DNA
sequences of different animals and hypothesize from which common ancestor each animal came
from. Points of agreement include: All animals came from a common ancestor; sponges are basal
animals; the Eumetazoa are the clade with true tissues; most animals belong to the clade Bilateria; and
chordates and Echinodermata are deuterostomes. New technology has allowed for the discovery of
differences within the Protostomia clade. Before, the clades just separated into the phylum, but now
some scientists insist that there are the ecdysozoans, who molt their shells, and the
lophotrochozoans, which either have the lophophore, a ring of ciliated tentacles surrounding the
mouth, or a trochophore larva stage.
5.
In older species, gas exchange was dependent on diffusion through their skin or gills that filtered the
oxygen out of the water. These chordates could only function in the water because their gills were not
adapted to the air. As they evolved, the fish evolved into amphibians, which had begun to develop
lungs to breathe above land on. These lungs weren’t perfect for breathing above water and
amphibians had to return to water or live in damp places in order to avoid dehydration. Finally, the
reptile was able to develop a fully-functioning lung for just air, allowing it to constantly stay above
land.
Organisms that have exoskeletons are generally more advanced; exoskeletons mean notochords and
better nervous systems. Most chordates have exoskeletons, but exoskeletons lack the protection that
endoskeletons provide. Insects and crustaceans both have exoskeletons that protect them from their
predators.
As organisms evolved, they went from the fish-like, unprotected, externally fertilized egg to an
internally fertilized, amniotic egg. This amniotic egg, first seen in reptiles as amphibians’ eggs are still
externally developed, helps increase the chance that there is healthy off-spring. Also, the leathery egg
and protects the reptile baby, the brittle egg that protects the bird baby and the placenta that feeds
the mammalian egg are all more reliable and provide nutrients for a longer period of time before the
actual birth. The mammalian egg is further internally developed, which means that the mother spends
longer period of time caring for the animal and can have less offspring.
As animals were developing a better nervous and cardiovascular system due to bilateral symmetric
development leading to cephalization, they were able to grow larger. A closed circulatory system,
with blood travelling through vessels, replaced a less efficient open circulatory system, where the
blood was pumped into cavities in the body. Furthermore, jointed appendages were a product of
bilateral symmetry; joined appendages specialized different areas of the body and gave rise to more
efficient body parts and better adapted organisms.
TARGET 2: INVERTEBRATE CLASSIFICATION
1.
Sponges belong to the Phylum Porifera. They are suspension feeders, or those who feed by straining
out food particles from the water. Water enters the spongocoel, the empty area inside the body of the
sponge, through the porocytes. They exit out through the osculum, which is the opening at the top of
the sponge body. Choanocytes are the cells lining the inside of the sponge along the spongocoel; their
flagella draws water into the sponge. The mesohyl is the matter between the two layers of the sponge
body. Amoebocytes move around and take food from the water to other cells. Sponges are
hermaphroditic, meaning they contain both types of gonads and can cross-fertilize. Finally, sponges
have no distinct tissues, which make them an exception to the invertebrate class.
2.
Cnidarians are invertebrates that include jellyfish, corals, and anemones. They are the first to have a
gastrovascular cavity, which is a sac with a central digestive compartment with one opening for both
the mouth and anus. Polyps are the stationary forms of the cnidarian, medusas are the motile form.
Cnidarians will usually alternate between the two forms during their lifetimes, with the medusas
creating the haploid sperm/egg cells. Cnidarians have cnidocytes that are cells specialized to the
cnidarian which contain the nematocysts. The nematocysts have little lances that are like BAM
MOTHAFUCKA I GOT YOU NOW penetrate the bodies of the prey. Cnidarians are diploblastic and are
radially symmetrical. They’re usually marine organisms, but can be found in freshwater. Anemones,
Class Anthozoa, are all marine, completely sessile with the medusa stage missing and colonial. Sea
jellies, Class Scyphozoa, are also all marine, completely motile with the polyp stage missing and are
free-swimming. Corals, Class Anthozoa, are also all marine, and can also belong to the Class Hydrozoa.
3.
Flatworms belong to the Phylum Platyhelminthes. They have flat bodies, hence their name, and also
contain prontenephridia, networks of tubules with ciliated structures that pull fluid through branched
ducts opening to the outside. Flatworms generally live anywhere there is a good supply of water. They
are acoelomates, which means that they don’t have a coelom. They are, however, tripoblastic.
Planarians, from Class Turbellaria, are flatworms that are nearly all free-living and mostly marine. They
move with cilia on their ventral surface and have a head equipped with eyespots to help sense where
they’re going. Furthermore, their pharynx is used as a food tool to scrape food and consume it. Flukes
are from the Class Trematoda and are parasites. They have alternating sexual and asexual stages and
require an intermediate host before infecting the final host. Tapeworms, from the Class Cestoda, are
also parasites. They’re nasty. Their heads, called scolexes, are armed with little suckers that hook onto
your intestine. Tapeworms absorb all your nutrients in order to grow larger. Gross.
4.
Organisms from the Phylum Nematoda are unsegmented roundworms. They undergo ecydsis, which
means molting. Their bodies are covered by a cuticle that has to shed before the nematode can grow.
They have no circulatory system, but they do have a pseudocoelom, and reproduce sexually through
internal fertilization. Pinworms and Hookworms are parasitic, but many nematodes are free-living.
5.
Mollusks belong to the Phylum Mollusca. They are coelomates and their bodies have three main parts:
the muscular foot, the visceral mass, and the mantle. The foot is used for movement. The visceral
mass is contains most of the internal organs of the mollusk. The mantle drapes over the visceral mass
and secretes a shell. The radula, the mollusk-equivalent of a pharynx, is the tool a mollusk uses to get
food. The Class Gastropoda includes snails. They have a head and use their foot for locomotion. The
Class Bivalvia includes clams and oysters and mussels and scallops. They have a flattened shell with
two halves. They have a reduced head, paired gills and no radula. The Class Cephalopodia includes
squiddies and octopi. These animals don’t secrete shells, are generally marine, and have tentacles with
suckers on them. They move by jet propulsion by directing and ejecting water through their siphon.
Finally, the cephalopods have a pen which is a brittle pseudoskeleton.
6.
Segmented worms belong to the Phylum Annelida. They help maintain soil fertility by leaving their
shit in the soil and toiling it for us, almost. They are hermaphroditic and can cross-fertilize. The Class
Oligochaeta is named because worms in this class have brittle chaetae to help them move made of
chitin. They are segmented, which means that their body cavity is split laterally by septums. Each
segment contains a metanephridium, which remove wastes from the body, like kidneys. They are
coelomates! So they do have a true coelom.
7.
Arthropods belong to the Phylum Arthopoda. These animals have segmented bodies, a hard
exoskeleton and jointed appendages. The appendages have been specialized for different uses, like
walking and reproducing. The body is completely covered by a cuticle, the exoskeleton made of chitin,
and has to undergo ecdysis in order to grow. The arthropods have an open circulatory system, which
means that the blood doesn’t travel in vessels to various parts of the body, but just is emptied into
large areas of the body. Hemolymph is the fluid pumped around the body. Spiders belong to the Class
Cheliceriformes, along with crabs and scorpions. These arthropods have one/two main body parts and
six pairs of appendages. On the other hand, lobsters belong to the Class Crustacea. The crustaceans
have two/three body parts and have chewing mouth parts.
8.
Echinoderms are named for their spiny skin. They also all have a backbone, are deuterostomes, and
are usually slow-moving or sessile. Their water vascular system is a network of hydraulic canals
branching into extensions called tube feet. These feet function in locomotion, feeding and gas
exchange. Madreporites dot the surface of the echinoderm, functioning as water filters. The anus is
right on top of the stomach, which is located in the center above the ring canal. The ring canal is
located in the central disc, in the middle of the echinoderm. Large gonads or digestive glands are
located in an arm of the sea star from Class Asteroida, for example, which makes the echinoderm notbilaterally symmetrical. The ampullae are connected to the radial canal. Ampullae bring water to the
tube feet of the sea star. Sea urchins, from Class Echinoida, do not have arms and are disc-shaped.
Their mouths are ringed by a complex, jaw-like structure. Sea cucumbers, from Class Holothuroidea,
do not have spines. They just resemble a large blobby thing.
TARGET 3: VERTEBRATE CLASSIFICATION
1.
Chordates all have a notochord, a dorsal, hollow nerve chord, pharyngeal slits, and a muscular, post
anal tail. Furthermore, they are all deuterostomes and exhibit bilateral symmetry. Chordates include
hagfish and lancelets
2.
Vertebrates all have back bones, have Dlx genes that helped to develop the advanced nervous system
and skeleton all vertebrates have. Finally, they have a skull and are all chordates. Examples include
fish, sharks, rays, reptiles, amphibians, birds and mammals.
3.
All vertebrates are chordates, but not all chordates are vertebrates. Vertebrates have a spinal column
and a backbone. Chordates don’t necessarily have backbones, just a notochord.
4.
Trait
Skeletal Comp
Gas Exchange
Air Bladder?
Operculum
Oviparous
Buoyancy
Chondrichthyes
Cartilage
Out of mouth/gills
No
No
Varied
No
Osteichthyes
Bone
Gills
Yes
Yes
Yes
Yes
5. Reptilia, Aves, Mammalia all are amniotes. Now, animals are able to have their offspring on land and
don’t have to return to the water to reproduce. This allows greater mobility and animals can truly become
terrestrial critters.
6.
Trait
Amphibians
Moist, smooth
skin
Reptiles
Scales—
keratin
Birds
Feathers –
Keratin
Fertilization
location
Internal/external
Internal
Internal
Internal
Development
location
External
Internal: Egg
(leathery)
Internal: Egg
(brittle)
Internal
(Placental/Marsupials/monotremes)
Three
Three
Four
Four
External in the
Larval Stage
Internal
Internal
Internal
Skin made of…
# Heart
Chambers
Resp
Membrane
Location
Mammals
Hairs—Keratin