Sample ZO208 Sample answers PDF

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Exam sample answers for ZO209 module...

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Sample ZO208 Sample answers. 1. Discuss the unique and defining characteristics of the phylum Cnidaria? Describe the diversity of life cycles found in cnidaria. All cnidaria are aquatic and mostly marine organisms. There are four different major groups of cnidarians: Anthozoa, cubozoa, hydrozoa and scyphozoa. All cnidarians share one specific trait, they have tentacles with stinging nematocysts. This is their defining feature. These nematocysts react to stimuli by throwing out small stinging cells that poison and capture prey using venom. The tentacle attaching the cell to the cnidarian retracts bringing it back so it can be eaten. They have a radial symmetry which is more complex than porifera. There are two main body types: Medusa and Polyp. The medusa is the classic jellyfish structure, and the polyp is like an inverted version where the tentacles facing upwards and the stalk is usually attached to a substrate. The are diploblasts which means they are made up of two germ layers. An endotherm and ectotherm layer. The ectotherm is the outside layer and the endotherm is the inner cavity of the animal. In between these layers is mesoglea, this gives it the jelly like feel. It is a gelatinous non-living tissue. It is mostly made up of water and some connective tissue. It does not require oxygen and food as it is not a metabolic tissue. It gives the body a structure and a skeleton. The internal anatomy of the medusa consists of the epidermis, gastrodermis which is formed by the endotherm. The gastrodermis is the gut, which is where digestion occurs and nutrients are absorbed. The gut forms a gastrovascular cavity and there is only one opening to the gut, this is the mouth/anus. The internal anatomy of the polyp consists of the body stalk and the tentacles facing upwards. It is very similar to the medusa where there is mesoglea in between the epidermis and the gastrodermis. This mesoglea is generally a lot thinner than the medusa. These body plans are quite simple they do not have any circulatory, respiratory, nervous or osmoregulatory system. They have an incomplete gut and simple muscle structure. They do have a nerve net which is naked neurons surround the body so they can respond to stimulus outside the body. On the medusa structure they have a sensory structure called the rhopalium located on the edge of the rim of the medusa. It contains ocelli which are pigmented photosensitive structures which can tell the animal if they are in a light or dark environment. Underneath this they have statocysts which are gravity receptors which allow the animal to know if its upright or not. They also have pacemaker neurons which set the rhythm of their swim. General life cycle based on scyphozoan These can sexually reproduce by egg ans sperm. Form through zygote, no copulation. This forms into a planula larva this then lands on the sea floor and forms into a polyp. This can survive independently. It can asexually reproduce by budding. It can also prduce new medusa asexually, they produce ephyra which are mini medusa forms. They then swim and form into a medusa and from then can sexually reproduce, completing the life cycle of the jellyfish.

2. What are the main characteristics of annelids. Describe using examples the diversity of feeding ecologies found in the major groups of annelids. Annelids have many defining features and characteristics. Based off the body plan of a Ragworm (some features lost in later groups). They have bilateral symmetry and are triploblastic. They are metameric segmented which means they have repeating units that have a similar set of organs in each unit. This also allows for easy adaptation. Their head is comprised of two parts- Prostomium and Peristomium. In the prostomium it contains the eyes and tentacles and in the peristomium which is located just behind it is attached to a pair of jaws which can evert out when needed to catch prey. They also have parapodia which are pairs on the outside of each segment, they act as limbs and have respiratory functions. They bear setae which are hair like features, they help to grip and move. A closed circulatory system is another feature, this allows the blood to be put under pressure and pumped around the body. It allows a more efficient way to transfer gases, energy and wastes. They also have a complex nervous system, in some forms there are complex eyes from the cerebral ganglia which is a concentration of nerves on the anterior f the animal a ventral nerve cord which runs along there stomach, segmental nerves in each segments which intervene the segments. There is also an osmoregulatory system present in the nephridia. These allow the control of internal conditions of the animal; they are analogous to the kidneys. They transfer waste from the blood and have an opening to the 0utside where urine is expelled. An complete digestive system is also present, they have a mouth and an anus. Meaning you can specialize the gut, the food is broken down in different ways at different regions. This allows for more efficient digestion of food. Finally, they are coelomate where they can host all the organs discussed above. It also acts as a hydrostatic skeleton, this is relying on all fluid to move. Each segments is dividied by septa will also completely divide the coelum across them. The septa close off each fluid cavities allowing each segment to act as a little hydrostatic skeleton itself. By contracting and relaxing they can push some parts of the body backwards or forwards. This allows for better movement. There is variety in the feeding methods of annelids. The common earthworm (Lumbricus terrestris) feeds on live and dead organic matter in soil. When food enters the earthworms mouth it’s pharynx brings the food into the oesophagus where it then passes through the gizzard. From contracting and relaxing the food is broken down into mineral particles so it can be ingested. The food then moves into the intestines where specific enzymes are released to digest fats, proteins and cellulose. The nutrients rae then absorbed and waste is excreted via the anus. ADD LIFE CYCLES and REPRODUCTION.

3. Provide an overview of the subphylum Chelicerata. Describe the relationship between classes within the subphylum and outline key morphological features and general ecology of each class. There are three classes under the subphylum chelicerata. 2 marine and 1 terrestrial. Pycnogonida, merotomata and arachnida. There isn’t much fossil record as spiders don’t preserve well in fossils. However there are chelicerate like creatures dating back to late Cambrian. The oldest fossil of the horse show crab dates back to late Ordovician. Class pycnogonida is composed of a single order comprising 10 famillies and around 1300 species. Their leg span varies from mm to over 60cm. sea spiders are either predators or scavengers. Their mouth extends into a straw like feature called proboscis, in which they can suck the insides of their prey. They have a pair of chelicerae that are like pliars which allow them to forage and being their food to the proboscis. The body is clearly segmented. It is not as clearly divided into tagmata as other arthropods. Class Merostomata is easily recognizable, they are the only cherlicerate that have compound eyes. They predate on small invertebrates using ther legs and chelicerates to bring food to their mouth. The mouth is located at the centre of the body where all the legs join together. There us only four known species of horsehsoe crabs in south east asia where they are pized for their flesh. Class arachnida is by far the largest class with between 75,000 and 100,000 species worldwide. There are eleven orders, Acari, ambyplygi, solifugae, telyphonida, scorpions, Araneae, Opiliones, schizomida, ricinulei, palpigrade and pseudoscorpiones. They all share the same body plan; segmented into two tagmata, cephalothorax (prosoma) and abdomen (opisthosoma). The cephalothorax has a pair of chelicerae, pediphalps and four or five pairs of walking legs. Anatnnae are absent and usually bear simple eyes. For reproduction, all chelicerrate except horseshoe crabs use internal fertilization. External fertilization in the horseshoe crab is an adaptation to the marine lifestyle. Most are egg laying but all scorpions and some mites give birth to live babies. This is known as ovoviviparity.

4. Discuss the structure of mouthparts in arthropods. Make reference to phylogeny, modes of feeding and occupation of ecological niches to structure your answer. Arthropods are characterized by a segmented body, exoskeleton and jointed legs. Arthropods are divided into four extant subphyla and one extinct. Crustacea, myriapodia, hexopoda and chelicerata. Arthropods appeared first in the Cambrian explosion which occurred between 542 and 515 MYA. The oldest fossil is a trilobitomorpha which is dated from 520 MYA. All the early arthropods were marine organisms. The closest relative of arthropods are tardigrades and velvet worms. The chelicerates were the first to branch out from the rest of the chelicerates. The differ in some ways for example they don’t have antennae or manidibles. Within the mandibulta the myriapoda branched out first. Hexopoda and crustacea all form one clade called pancrustacea. The most fundamental evolutionary differences between two major clades (chelicerata and mandibulata) in arthropods is their mouthparts structure. The mandibulata are made up of the crustaceans and myriapoda. They have labrum which is the ‘upper lip’, mandibles ‘teeth’, maxillae ‘fingers and teeth’, labium ‘tongue’ and a hypopharynx ‘throat’. Centipedes have evolved a pair of forciples which are sharp venom claws, they have evolved from a pair of legs. In crustaceans they have maxilipedes which are used for feeding. In chelicerata (spiders, scorpions, horseshoe crabs) they do not have mandibles. They have developed mouthparts independently from the mandibulata. The mouth is a simple round opening and they are appendages bringing the food into the mouth. They can be three different forms depending on the species. 1. Jack knife- In spiders the chelicerae are the fangs. 2. Scissors- in camel spiders the chelicerae act like a pair of vertical scissors. 3. 3 segmented chelate- in scorpions the chelicerae look like mini claws that are retracted on the inside of the mouth. In arthropods there are also various modes of feeding. Generalist feeding is where they can feed on a variety of things. For example, crickets feed on grain, plants or other bugs. Specialist is where they feed on specific items. For example, bugs are herbivorous meaning they only feed on plants. Saprophagous is feeding on decaying plants. Millipedes are saprophagous as they feed exclusively on decaying plants. Predaceous is when an organism feeds by killing other animals. All but one genus of spiders are obligate predators (over 40,000) species. Parasitic is another mode which involves feeding on or in organisms without killing the for example, bed bugs where they suck their blood. Parasitoid is where the animal infests the host organism and always kill them. Parasitoid wasp is well known for this method.

5. Describe the unique characteristics of Echinodermata. Provide an overview of the main morphological and ecological differences between the five echinoderm classes. The phylum Echinodermata means spiky skin in Greek. They are found at every area in the ocean. There are about 6500-7000 living species. They are the largest phylum with no freshwater or terrestrial species. There are five different subphylum, Asteroidea, Ophiuroidea, Echinoidea, Crinoidea and Holothuroidea. They are exclusively marine and free-living species. They are triploblastic meaning they have three layers (endoderm, mesoderm, and ectoderm). They are also deuterostome which means the blastophore develops into the anus. They also have pentaradial symmetry. Some of the unique features to echinoderms are: They have a calcareous endoskeleton of interlocking plates and ossicles. Each plate is a single calcite crystal which forms a complex matrix. Allowing the skeleton to be strong yet light. An epidermis covers this skeleton which has tube feet and respiring structures around it. Tubercles are also present which can have spines or other structures. In sea urchins and starfish, they have a unique feature called pedicellariae. They are small structures that can be made up of a jaw, simple muscles structures that allow them to open and close. Their function is mainly as protection against parasites and for removing debris that may fall on the animal. In starfish the plates don’t fuse together. In sea cucumbers the plates and ossicles remain small and scatter within the dermis. They have a unique water vascular system which is their version of a circulatory system. They use the medreporite which Is on the outside of the animal, water flows through this gap through the stone canal into the central ring canal. It then flows around the central canal into the radial canals. The seawater feeds into the ampulla which are sacs at the end of the branches and the end of these sacs are tube feet. This allows provides locomotion through the tube feet, the water fills the ampulla which contracts muscles in the podium which moves It outwards and then pulls it back in when it takes more water in. These tube feet also act as gills for respiration. Echinoderms can reproduce sexually and asexually. In sexual there is two sexes and external fertilization where the egg and sperm are released into the water column and the larvae will then settle and form into whatever species it is. Crinoids make up 625 species, mostly deep water but some shallow. This group includes sea lillies and sea feathers. The main difference between sea lillies and sea feathers is how they attach themselves to sediment. Sea lillies have a holdfast and sea feathers have a cirri. They both have a calyx where the upper surface bears the mouth and anus. They have 5 arms which is the classic sedimentary. They also have pinnules on the arms which have tube feet which are used for collecting small organisms and for respiratory. They do not have a madreporite so the water vascular system works off coelmic fluid. They don’t have any external opening. They feed using their pinnules which extend outwards adnd using the water vascular system it takes in the food and takes it into the calyx. They are suspension feeders. They can both also move to a better environment or out of danger.

The Asteroidea consists of starfish. There are about 1500 species. They have the classic symmetary and a vascular water transport system. They are mobile predators that prey on shellfish. They do this using their stomach. They move along using their tube feet and find their prey. Typically in shallow waters. They can manipulate the prey and open it. they can articulate and open the shells. When they do that they evert their stomach out through their mouth and into the shell. They will then release digestive juices into the animal and digest it outside the body. Ophiurodiea which are brittle stars. They are the largest grough of echinoderms. 2000 species. Found in all marine habitats. They use their arms for movement. They are commensals to sponges and corals. They are penetral symmetary. Their arms are not tapered, they are sextremly long and thin. They are composed of vertebrae. Each segment have one pair of suckerless tube feet. The central disc is small. Their epiderms lacks cilia unlike other groups. Sometimes they have chromatophores which allow them to change colours. Unlike starfish they break up matter using their jaw. This allows them to be in different environments and be a scavenger. Basket stars are also part of this group. This animals arms branch off and it is a suspension feeder, when food falls on these arms they curl up and bring the food into the centre of the animal. The second last group echinoidea which consist of sea urchins, heart urchins and sand dollars. There are around 950 species. They have a fused test. The water vascular system are all folded up into a ball. The mouth ans anus are at opposite ends. It still has the penetradial symmetary. It then relies on tube feet for movement. There are ireegular shaped sea urchins which have adapted a bilateral symmetry and short spines. Heart urchins and sand dollars have his make up. Sea urchins have aristotles lantern jaw which allows them to break up food and have geberal ecology. They are important as ecosystem engineers. They can change what an ecosystem looks like. It is a very comple jaw. Pentaradial symmetry. The final group is the Holothuroidea the sea cucumbers. There is about 1200 species. Deep sea and shallow. Their ossicles are reduced making them soft. They vary in size mm to 2 metres. They only reproduce by sexual reproduction. They also have pentaradial symmetry. They often have tentacles at the mouth used for feeing. The unique feature is how they respire. They have a respiratory tree which is a respiratory structure in the animal that is connected to the external environment through the anus. They are mostly deposit feeders, it sifts through sediment using its tentacles. They are important im deep sea environments keeping it aerated. Theyare also filter feeders, the tentavles also capture organic organism and bring it to the mouth. For defence many of these species are poisonous. Other spcies can also cast out their viscera which is essentially their intestine. The cuverian tubules are attached to the intestine, preadtors could get attached to this or sometimes they are toxic. They can regrow these organs pretty quickly. They have a commensal relationship with the pear fish, they can live in their anus.

6. Describe the main feeding strategies of the main different feeding strategies of the eight different classes of phylum Mollusca. Molluscs consist of snails, squids, scallops and some other groups such as chitins and tusk shells. There are about 80,000 and more names species. They are in marine, terrestrial and freshwater habitats. Triploblastic, protomsomes,lophotrochozoan, unsegmented, coelomates with complex nervous, circulatory, respiratory and excretory system. They also possess a mantle and a foot. Unique feature called a radula. It is a rasping tongue in the mouth. Chitinous ribbon of teeth used for feeding. Using for scraping and cutting food. There are eight different classes and in each class they have different feeding strategies. Class polyplacophora which are known as chitons. There are about 1000 speccies. They have a mouth and a radula which is used to scrape algae off rocks. The radula is very important as they feeding using it to scrape rocky the rocky substrates. Class aplacophora which are known as spicule worms. They are split into two groups, Chaetodermomorpha and Neomeniomorpha. The Chaetodermomorpha feed using their radula, they feed on microorganisms and detritus.

Class monoplacophora are a small group. They have one shell. They also use their radula to graze on algae and any detritus. Class gastropods are also within the conchifera meaning they have a single shell. There are about 70,000 species. They have a radula and a complex digestive system. For feeding they also use their radula to scrape particles from surfaces of rocks and seaweeds. There are lots of species of gastropods that are carnivores, nucella use their radula to drill holes in their prey and feed on the animal. They are aided by their glands which secrete enzymes that help break down and digest the animal. Cone snails have another strategy, they have a siphon with a harpoon. They use their harpoon to catch species such as fish. They are very venomous, they have a quick acting neurotoxin that hits the fish and paralyzes it. This is why they are so efficient and effective. Nudibranches are another type of gastropod. This group has lost their shell so for defence they are poisonous. Many of these species will feed on cnidarian prey such as polyps. They sequester the nematocysts from their prey and store them in a specialized area of their body so they can re sue the armry form the cnidarian for themselves. In the class Bivalvia which consist of shelled animals that are filter feeders. There are about 10,000 species, mostly marine but some freshwater species. To fee...