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Notes - Annelida and Mollusca

- Annelids are another type of worm. ________________ are the most well known of the annelids.

There are over ________ species of annelids with most living in the oceans or in soil. Annelids differ

from flat and roundworms by being ________________. They range in size from less than 1

millimetre to 3 metres long. Annelida is divided into three main classes; Polchaeta, _____________,

and __________________.

Phylum Annelida

- Annelida – ___________________ – the word annelid comes from the _______ word annellus, which

means little rings. Annelid bodies are composed of many segments that are generally the same. The

segments are ___________ by thin internal tissue called __________ (septum pl.).

- Annelids eat using a __________ followed by a long tube that exits the body at the anus. The “tube”

has specialised areas along the way to aid in ____________ and digestion of food. The mouth is

attached to the ____________ by the pharynx. The pharynx can be extended out of the mouth to

aid in food capture or ____________. The esophagus leads to the crop (___________) where food

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is stored and onto the _____________ (mechanical grinding to break-up food) before entering the

intestine (enzyme digestion) and exiting through the anus.

- ____________ annelids use gills to filter oxygen out of the water. Terrestrial annelids use _______

_________ to allow gas exchange to diffuse through. A cuticle is used to keep the skin moist.

- Annelids do have a ______________ circulatory system (vessels) that pump blood towards the head

______________ and returning to the tail _____________. The two main vessels are connected

two each other and tissues, in each segment, by ring vessels. Near the head the ring vessels are

larger and __________ ___ ___________ to allow contraction and pumping of blood. These

anterior ring vessels are therefore called __________ _________ (hearts).

- Metabolic excretion occurs via a pair of nephridium in each segment, while solid waste passes via the

____________.

- Annelids have a well developed nervous system. They have a simple brain connected to a pair of ganglia

in the head. The nerves continue from the pair of ganglia down the annelid via the _________ nerve

chord with small branches in each segment of the worm. Most annelids have many sense organs for

touch, chemicals and light. A few worm species (marine) have eyes developed enough to perceive

images. Most do not have protective adaptations but a few do. Some carnivorous worms use their

jaws or ____________ ____________ (marine worms) to fight back.

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- Movement occurs using _____________ and transverse muscles to lengthen/shorten or dilate/shrink

and essentially “wiggle”.

- Reproduction is commonly __________ with a few annelids able to asexually reproduce via

___________. The sexes are separate in the worms and both fertilisation and development occur

externally. Marine worms often congregate to increase chances of sperm meeting egg. Terrestrial

worms and leeches are often _______________ and undergo internal fertilisation. They rarely

fertilise themselves. The worms pair up and exchange sperm, which they store in a special sac for

later. When ready the ______________ of the worm releases mucous with both sperm and eggs

inside. The clitellum slides off to form a _____________ of protection.

- _______________ – sandworms, bloodworms, and cousins – __________ means bristles. This part of

the name refers to each segments pairs of paddles with many bristles on the end. This class exists in

soil, freshwater and marine environments.

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- Oligochaeta – earthworms and cousins – oligo means “few” so these worms have much fewer bristles.

Most live terrestrially or in freshwater (few in marine). Earthworms eat _______ and pass the dirt

particles out the anus as “___________”.

- Hirudinea – __________ – an exterior parasitic worm with less apparent segmentation and

__________ at both ends. Leeches use razor sharp teeth or a _____________ to pierce tissues

and inject an ____________________ to aid in blood or fluid removal.

Role in Nature

- Annelids function as food for many marine organisms and as fabulous soil aerators terrestrial. Leeches

and their saliva have become a major medical help. They are often used to remove old blood in limb

reattachments and their saliva is an excellent heart attack/stroke medicine used to thin blood.

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Phylum Mollusca

- Commonly known as _____________ they are the second most numerous animal species

(100000������) after arthropods (_________). The name mollusc is from the Latin Molluscus

meaning “________”. Mollusks are defined as a soft bodied animals with an internal or external shell.

They range from oceans to the tops of trees. Mollusks are very diverse in behaviour and looks. They

are grouped together based on a common larval form called a _____________. Trocophore swim in

open water and feed off small floating plants. Annelids also have a larval trocophore form. It is this

that causes biologists to believe that a common ancestor may have existed.

- All mollusks have four main parts: foot, mantle, shell, and visceral mass. The _______ is a muscular

organ that often contains the _______ and ingestion structures. The foot can be used for crawling,

attachment to substrate, or as tentacles. The mantle is a thin, soft tissue that covers the animal’s

body like a cloak. The shell is for protection, and is made by calcium carbonate (CaCO3) that is

excreted by the mantle. The visceral mass contains the organs. These four parts take on different

roles depending on habitat. The shell and foot are used to categorize mollusks into three classes.

- Molluscs can be carnivorous, herbivorous, detrivores, parasitic, or even filter feeders. Many feed using

a layer of ___________ ______ with small teeth on it called a radula. This can be used to _______

algae, eat buds and roots, or scrape through shells and tear up the soft tissues of prey inside.

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- Some mollusks such as clams, oysters or ___________ are filter feeders instead, and use their gills

to filter small _________________ in the water and have cilia move the particles into the mouth.

- Most mollusks ______________ using gills located in their mantles. If they are terrestrial then they

use a large, ________, folded region on the inside of their ________ to allow oxygen to diffuse

into the animal.

- Slow moving mollusks have an ________circulatory system. This means that the system does not fully

contain blood inside of vessels but rather opens into large areas called _________ that allow the

blood to bath the organs and tissues inside of the sinus. It then returns to vessels leading to the

_________ and ______ before dumping into the sinuses again. Fast moving mollusks like octopi and

squid have a __________circulatory system that uses vessels for transport throughout the body.

- Excretion occurs like annelids. Solid waste is removed via the anus and _____________ wastes are

removed by _______________.

- Mollusks vary in nervous system development as well. Snails and slugs have a __________ and some

nerve chords throughout their body that connect to eyes and touch receptors. However, octopi and

squid have very developed _________ (can learn and remember), advanced nervous systems, and

sensory organs capable.

- Most mollusks have separate sexes. Untentacled mollusks reproduce with ______ fertilising the egg

externally. The sperm and egg meet through chance and a free-swimming larva develops. In tentacled

mollusks and certain hermaphroditic snails the _____________ takes place inside of the female. In

the snails they pair up and fertilise each other.

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Phylum Gastropoda

- _____________ – stomach foot – this class includes _______, ______, abalones, and nudibranchs.

Most have a one-piece shell for protection, while slugs and ____________ do not. They protect

themselves with toxins (brightly coloured nudibrachs!) or by behaviour (slugs hide during day).

Phylum ____________

- Bivalves – ____ ______ – this class includes clams, oysters, and scallops. Most bivalves are ________

filter feeders. They anchor themselves by digging into mud (clams) or using sticky threads (mussels).

The scallop can “swim” by flapping its two shelf halves.

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Phylum Cephalopoda

- Cephalopods – head foot – this class includes squid, octopi, ___________, and _________. The foot

has adapted to become the 8 arms, and 2 tentacles (not in octopi). The arms or tentacles are covered

in __________ _____ and used to grab prey. The shell has been internalised in all but the nautiluses

and lost in the octopus. Most are able to evade predators using ___ ____________, ink, or special

cells (________________) that completely mimic their surroundings.

Role in Nature

- Mollusks are excellent detrivores returning nutrients to the environment as well as some are hosts to

symbiotic algae. Snails and slugs can be pests in gardens as they eat food crops. Also, ___________

(bivalve) cause millions of dollars in damage to boats and docks by drilling through wood with their

shells. Bivalves are excellent indicators of water quality. Because they are filter feeders, monitoring

their tissues for toxins is an excellent way to accurate pollution levels. However, in recent years they

have become very important to science and medicine. The _________ _____ has an amazing toxin

that is being researched as a possible pain reliever or muscle relaxant. Also, some mollusks are

immune to cancer. Scientists are trying to figure out what it is that causes the immunity.

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