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KINGDOM ANIMALIA
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Are divided into the protostomes and deuterostomes
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They are heterotrophic, multicellular, and eukaryotic.
They are organisms that store carbohydrates as glycogen.
They lack cell walls.
Have nervous and muscle tissue.
They reproduce sexually, with fertilization resulting in a blastula.
The blastula undergoes gastrulation.
Organisms may have complicated life stages, such as a larval stage.
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The Invertebrates:
- Have no vertebrate, or notochord
- Phyla:
- Porifera
- Cnidaria
- Symmetry:
- Radial Body parts are arranged around a central axis.
- These organisms have a top and a bottom, but no front, back, left or right.
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Body Cavity:
- The body cavity is diploblastic (having two germs layer, the endoderm and
ectoderm).
- A gelatinous region often separates the two layers.
Phylum Porifera:
- The sponges
- Show primitive radial symmetry
- A gelatinous region called the mesophyll separates the two body layers
- There are 4 classes based on skeletal structure
- Skeleton is made of spicules (SiO2, CaCO3) or spongin (protein)
- Reproduce sexually or asexually through gemmules
- Primarily marine, a few f.w.
- Sponges are just a large colony of cooperating cells.
- There are many cell types, all performing different functions for the good of
the entire organism.
Phylum Cnidaria:
- Hydra, jellyfish, corals, sea anemones, and box jellies (5 Classes)
- Cells are arranged into two tissue layers:
- The gastrodermis (lines the GVC)
- The epidermis (comes from embryonic ectoderm).
- Mesoglea (jello-like substance) separates the two layers.
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Cnidocytes (nematocysts) are stinging cells that capture prey.
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Two morphos:
- Medusa
- Polyp
Can reproduce sexually and asexually
Only one opening- all food must enter and exit
Are essential in the food web of the oceans
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Symmetry Bilateral:
- Bilateral organisms have a left, right, top (dorsal) and a bottom (ventral).
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Most have a distinct head and tail end (anterior and posterior).
The collection of nerve cells towards the anterior end starts the formation of a
brain. This is called cephalization.
Body Cavity:
- The body cavity is now triploblastic.
- They have 3 embryonic layers:
- Endoderm
- Mesoderm
- Ectoderm
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These are called 'germ layers'.
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Triploblastic animals are divided into 3 categories, based on their type of
coelomic cavity.
- Acoelomates:
- The simplest arrangement.
- Three germ layers packed together and there is no body cavity other than
the digestive cavity.
- There is no body cavity between the gut and the outer body wall.
- Phylum: Platyhelminthes.
- Pseduocoelomates:
- They have a false coelom.
- There is an additional cavity between the endoderm and the mesoderm.
- This is called a pseudocoloem because of the location of the cavity.
- The cavity has no epithelial lining derived from the mesoderm.
- Phylum: Nematoda
- Coelomates:
- They all have a true coelom; a fluid filled cavity that develops within the
mesoderm.
- Within the coelom, the digestive tract and other internal organs are lined
with epithelial tissue.
- These tissues are known as the mesenteries.
- Phyla: Mollusca through Chordates
Acoelomates
- Phylum Platyhelminthes-acoelomate:
- 3 classes:
- Turbellaira
- Cestoidea
- Trematoda
- Class Turbellaira:
- The flatworms
- They have a mouth, pharynx, and a branched gastrovascular cavity.
- Respiration is through the skin.
- Water balance and excretion is via flame cells in Planaria.
- Over evolutionary time, these are the structures that will develop into kidneys.
- There is no brain, instead the beginnings of cephalization, the ganglia.
- Class Cestoidea:
- The tapeworms; all are parasitic
- They are so parasitic that they have no digestive system.
- Have a 'head' called the scolex, which attaches to the intestine of other
animals.
- Body is divided into proglottids.
- These are 'segments' which contain all the necessary structures to form a
new tapeworm.
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Adult tapeworms can get up to 20 meters in length.
Ripe proglottids exit through the feces and contain eggs.
Infection occurs when a new primary host consumes the eggs.
The primary host has the eggs hatch into a larvae, which travel to muscle
tissue.
- The secondary host becomes infected by eating a primary host.
- Ex: dog tape worm (Dipylidium caninum)
Class Trematoda:
- Commonly called flukes
- All are parasitic, but have a digestive system.
- A sucker surrounds the mouth, which pumps in nutrients from the hosts'
intestine or liver.
- They are hermaphroditic (monoecious). The fertilized eggs pass out of the
host with feces.
- Larva is eaten by a primary host (i.e. snail). The larva develops into a
sporocyst.
- Sporocyst leaves the snail and changes into a cercariae larva in the water.
- The larvae buries into fish muscle (secondary host).
- Fish is eaten by the final host (man), which the larva grows into the adult.
- Ex: Chinese liver fluke (Clonorchis sinensis)
Pseudocoelomates
- Phylum Nematoda:
- Pseudocoelomate
- Called the roundworms.
- They lack a circulatory system, contractions move the body fluid.
- They have a one-way digestive system with two openings.
- Are mainly dioecious. The female is usually larger than the male.
- Fertilization is internal and females can deposit up to 100,000 eggs per day in
some species.
- Zygotes are resistant to harsh conditions.
- They can be either free-living or parasitic.
- Ex: Ascaris lives in the intestine. The host eats the egg, eggs hatches into a
larva. The larva burrows out of the intestine, into the bloodstream and travels
to the heart, lungs, up to the trachea and is finally swallowed down the
esophagus. The cycle repeats.
- Necator americanus (hookworm)
- Pinworms: account for up to 50% of all parasitic infections in US children.
Coelomates
- Within a coelom, surrounded by lubricating coelomic fluid, an animals’ organs can
now bend, twist and fold back on themselves.
- This increases surface area. They are divided into two groups, based on how their
embryo forms:
- Phylum Mollusca:
- These are protosomes that are soft-bodied, show bilateral symmetry and have a
true coelom.
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Body Zones:
- Head Foot:
- Contains both the sensory and motor organs.
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Visceral Mass:
- Well-developed organs for digestion, excretion and reproduction.
- Mantle:
- Specialized tissue formed from folds of the dorsal body wall.
- The Mantle hangs over and enfolds the visceral mass and secretes the shell
(if present).
Mantle Cavity:
- The Mantle cavity is the space between the mantle and the visceral mass, it
houses the gills
- The digestive, excretory, and reproductive systems discharge into the mantle
cavity.
- Water sweeps into the mantle cavity, passing across the surface of the gills,
aerating them.
Radula:
- This is a movable, tooth-bearing strip of chitnous material. The teeth are
arranged in rows. The number of teeth can be of taxonomic value.
Shell:
- Made of CaCO3
Circulatory System:
- Consist of a pumping organ, the heart, and the vessels that carry the blood to
and from the heart.
- The heart has 3 chambers: two atria and one ventricle.
- All mollusks have an open circulatory system except for cephalods.
- Open systems means that the blood is not contained in vessels. The blood
collected from the gills, pumped through the heart and releases directly into
the tissue.
- The blood-filled spaces are called the hemocoel. Blood us also called
hemolymph.
Digestion:
- The digestive tract is extensively ciliated. Food is taken up by the cells lining
the digestive glands, which arise from the stomach and anterior intestine, and
enter the blood.
- Undigested material is discharged through the anus.
Excretion:
- Nitrogenous wastes produced by metabolic activities are removed by
nephridia (future kidney).
There are 7 classes of mollusks. We are only going to study four.
- Class: Polyplacophora
- Class: Bivalvia
- Class: Gastropoda
- Class: Cephalopoda
Class Polyplacophora:
- Chitons
- Oval-shaped marine
- Shells are divided into 8 dorsal plates
- Mostly in the intertidal are
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They use their radula (often tipped with iron) to scrape algae off of rocks.
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Class Bivalvia:
- Clams, scallops, mussels, oysters
- 2 shells that are hinged
- Have adductor muscle to open and close the shell
- The radula is absent
- Sessile filter feeders.
- Gills are used for respiration as well as for trapping food particles (plankton).
- There is no head or brain.
- Sexes are separate.
- Can be fresh water of marine.
- Donax, Venus
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Class Gastropoda:
- The largest, most successful class of mollusks
- Snails, slugs, abalones, limpets, nudibranchs
- The mantle secretes a shell (if present).
- Great cephalization with two pairs of tentacles with one pair of eyes.
- The radula is present,
- Can be herbivores or carnivorous, even parasitic.
- Most have separate sexes; some hermaphrodites (slugs, sea hares,
nudibranchs)
- Are freshwater, marine, and terrestrial.
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Greatest success is due to torsion: twisting of the body cavity 180 degrees
relative to the head. This results in the mantle cavity and visceral mass
moving to a position over the head.
- Strombus, Philomycus, Helix
- Class Cephalopoda:
- Squid, cuttlefish, octopus and nautilus
- The foot is divided into 8 arms with suckers. Sometimes there is also 2
tentacles
- Move rapidly by jet propulsion using their siphon/
- Closed circulatory system with two types of hearts:
- Arterial heart: pumps blood throughout the body.
- Systematic hearts: receive blood from the body and pump it to the gills.
- May have an external shell (nautilus), internal shell (squid and cuttlefish)
called a pen, or no shell (octopus).
- They show extreme cephalization. They have very well developed brains, and
excellent eyesight – better than mammals. They have no macula (blind-spot).
- They are all marine carnivores.
- Use their beaks to rip and tear flesh. The radula brings the food into the body
for consumption.
- Figure 33.22 Cephalopods: Squid (top left and bottom left), nautilus (top
right), octopus (bottom right)
Phylum Annelida:
- True worms
- True segmentation
- 3 classes:
- Class Oligochaeta
- Class Polychaeta
- Class Hirundinea
- Class Oligochaeta:
- Earthworms
- Regular segments: true metamerism (the serial duplication of body parts)
- Special segments for reproduction, nervous system, and circulatory systems.
- They have a mouth, pharynx (suction pump) esophagus, crop (stores food),
gizzard (grinding), intestine and anus.
- Mostly hermaphroditic
- Earthworms have a clitellum: a special structure for reproduction. They have
both seminal receptacles and seminal vesicles.
- Have small setae (lateral bristles) 4 per segment for locomotion.
- Mostly terrestrial.
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Lumbricous terrestris
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Class Polychaeta:
- Marine worms
- Have visible parapodia on segments (which contain setae).
- Have separate sexes, no clitelum.
- A free-swimming trocophore larvae is present.
- Have a well-developed head with tentacles and eyes.
- Usually bright colored. Setae may contain toxins for protection.
- Important in reef ecosystems.
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Class Hirundinea:
- The leeches
- Mostly freshwater, some marine.
- Parasitic bloodsuckers of vertebrates.
- There is no head, except for a sucker around the mouth and cutting jaws.
There are no setae or parapodia on segments.
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Phylum Onycophora:
- The link between Annelids and Anthropods
- This increases surface area.
- They are divided into two groups, based on how their embryos forms:
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Phylum Arthropoda:
- This is the largest animal phyla, with more than 50 million species (1 million
species of insects).
- ‘Arthro’ means jointed and ‘poda’ means foot. They are characterized by having
jointed appendages and a tough exoskeleton made of chitin.
- Ecdysis (via ecdysone) is the method of growth.
- The arthropods are only invertebrate to enter a new habitat – the air.
- They also inhabit land, freshwater and marine environments.
- Types of Arthropods:
- 1) Trilobites (extinct)
- 2) Chelicerates
- 3) Crustaceans
- 4) Insects
- The exoskeleton is secreted by the underlying epidermis.
- The skeleton is composed of an outer layer (waxy) made of lipoproteins, a
hardened middle layer and a flexible inner layer.
- The exoskeleton is excellent protection against predators and is usually
waterproof.
- Muscles are attached to the various portions of the interior exoskeleton allowing
for complex movement.
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The exoskeleton does not grow. Therefore, in order for growth to occur it must
be shed.
Ecdysis (or molting) is the shedding of the exoskeleton. Ecdysone is just one of
many hormone involved in this process.
After shedding, the animal is vulnerable to predators for a short time while the
new shell hardens.
Appendages:
- In arthropods are very diverse. They can be modified for walking, feeding,
sensory reception, copulation and defense.
- Mouthparts are very complex they can be modified as:
- Mandible: the hard part, which crushes food (caterpillars, roaches,
lobsters).
- Chelicerae: are fang-like appendages, which pierce and suck the prey
(spiders, ticks, mites).
- Maxillae and Maxillary Palps: can manipulate and hold food (part of
mandible).
- Pedipalps: in Chelicarates and Maxillipeds in Mandibulates are also
present for either walking or holding food items.
Excretory Systems:
- Insects have Malpighian tubules, which are located in the coelom and absorb
nitrogenous wastes from the blood and pass it into the rectum.
- Crustaceans have “green glands” which are in the head and absorb
nitrogenous wastes from the blood and pass it out of the body near the
antennae.
Circulatory System:
- All Arthropods have an open system, just like many of the mollusks (no
vessels, arteries, veins, hemolymph).
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Respiratory System:
- They have many gills to take in oxygen from water. Many have “book gills”
(seen in horseshoe crabs) which work like gills. They are thin “pages” of
tissue.
- Book lungs (spiders) are a series of page-like air sacs that take oxygen from
air.
- Tracheal tubes have outside holes (spiracles) that lead to tracheal tubes, which
end in tiny moist tubes (trachioles). Trachioles exchange gases with the body
cells.
Reproduction and Development:
- All members of this phylum are diecious (separate sexes).
- Fertilization occurs inside the female who lay eggs.
Metamorphosis:
- There are two types:
- 1) Incomplete: egg -> nymph -> adult
- 2) Complete: egg -> larva -> pupa -> adult
- All metamorphosis is regulated by hormones.
Nervous System:
- Arthropods have a brain with ventral nerve cords and ganglia that run down
the length of the body. The arthropods that have compound eyes have special
lobes of the brain devoted to sight.
- Arthropods have five senses:
- 1) Sight:
- Some Arthropods have simple eyes (ocelli) that detect light and dark
only.
- Others have compound eyes made up of over 2,000 facets (little eyes)
that see images in a mosaic pattern. Studies show that insects do see
color (except red).
- 2) Taste:
- Maxillary palps, labial palps and Pedipalps are the taste organs.
- 3) Smell (chemical detection)
- Antennae are the primary organs for this.
- 4) Touch:
- Antennae (and antennules if present) and sensory ‘hairs’ and bristles
on the body.
- 5) Hearing:
- Arthropods detect vibrations, not sound. The tympanum is a
specialized organ to detect vibrations. Sensory hairs and bristles are
also used.
Note: each Class, Order, Family, etc. Can very in the type of structures used.
Subphylum: Chelicereta
- These arthropods feed via Chelicerae (spiders). There are no antennae or
mandibles.
- The 1st pair of appendages are Chelicerae (or fangs).
- The 2nd pair of appendages are Pedipalps that may have pincers, modified
walking legs, or sensory organs.
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Posterior to the Pedipalps are the jointed walking legs. The head and thorax
may be fused; this structure is then called Cephalothorax. They respire with
Trachea. No living Chelicerate has antennae.
There are 4 classes:
- 1) Trilobita
- 2) Merostomata
- 3) Pycnogonida (sea spiders)
- 4) Arachnida
1) Trilobites:
- The Cambrian Period (540-500 mya) was known as the Age of the
Trilobites.
- A massive extinction at the end of the Cambrian wiped out all Trilobites.
- Their head and Thorax was fused together (Cephalothorax).
- They had the ability to curl up into a tight ‘ball’ for protection.
2) Merostomata:
- The horseshoe crabs are the most ancient living arthropods.
- There are only 4 species. Limulus is genus off the coast of Florida.
- They have been extremely important in cancer and AIDS research.
- They live in shallow water, commonly found in the Intercoastal
Waterway.
- Their eyes are simple.
- Reproduction takes place out of water in sandy areas.
3) Pycnogonida:
- The sea spiders.
- There are marine organisms that feed on other invertebrates, such as soft
coral hydroids.
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There not true spiders – they have 10 legs.
In males, they use the ‘extra’ set of walking appendages to brood the eggs.
These organisms are small, usually about ¾ of and inch or less in length.
4) Arachnida:
- There are 57,000 species of spiders, ticks, mites, and scorpions. They all
have 4 pairs of walking legs.
- Spiders:
- Their Chelicerae are highly specialized for feeding.
- Spiders have Pedipalps, which they use to sense their environment.
Males will also use these Pedipalps to transfer sperm to the female.
- Spiders live on liquid diets, their prey are bitten and then paralyzed.
- They produce an enzyme in their midgut, which pours into the tissue.
- The tissue is liquefied into broth.
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Ticks:
- Are blood-sucking parasites on mammals.
- American dog tick (Dermacentor variablis).
- Deer ticks (Ixodes scapularis) are carriers of the bacteria that cause
Lyme disease (bacteria).
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Mites:
- Are ‘harrier’ than ticks. Mites are also extremely small compared to
ticks, ~ 1mm or less in length. Mites on humans eat dead skin cells.
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Scorpions:
- 8 walking legs and 2 pinchers.