BIOL113 Module 3: Animal Diversity

what is a general definition of an animal

• multicellular eukaryotes

• are heterotrophic (obtain carbon and energy via already-formed organic molecules)

• have tissue that develops from embryonic layers

what are some general characteristics of animals

• obviously exceptions to every one

• store carbohydrate reserves as glycogen

• lacks cell walls, with multicellular bodies held together by extracellular proteins (e.g. collagen)

• two unique types of tissues (nervous tissue for impulses and responding to the environment, muscular tissue for movement)

• most reproduce sexually, with a diploid stage dominating their lifecycle (usually flagellated sperm fertilising a nonmoile egg)

• the zygote they form undergoes successive mitotic cleavages to form bastula (multicellular hollow cell balls) - leading to embryo development

name the divisions of animal phylogeny focused on in this course

• eumatazoa and parazoa

• radiata and bilateria

• coelomates and acoelomates and pseudo-coelomates

• protosomes and deuterosomes

when were animals thought to have evolved

770mya in the Precambrian era

what was the animal common ancestor thought to be like

what is the evidence for this

• a common ancestor shared (monophyletic animal kingdom)

• a colonial flagellated protist, likely relating to the choanoflagellates (tiny, stalked)

• these live in shallow ponds / lakes / marine environments

• evidenced by sharing specific DNA data, suggesting them our closest relative

• e.g. protein adhesion gene, and that sponges (Earliest animal) have cells morphologically similar to them

how was the origin of animals thought to occur

• one hypothesis is that a colony of identical flagellated protists (choanoflagellates), evolved into forming a hollow sphere together (alike an animal’s blastula)

• the cells on this became specialised over time, creating multiple layers of cells

• infolding occurred gradually, which eventually formed a digestive cavity (a gut)

• eventually forming a ‘protoanimal’ embryo-like thing

how are animals characterised on their phylogenetic tree

• mainly with grades (groups that dont include all the descendents from a common ancestor)

• these seperate based on key characteristics of body plans, and embryonic development, each branch off representing a new feature that those on the branch share

how do parazoa and eumatazoa differ

when was this seperation on the phylogenetic tree

• this was the first divison on the animal phylogenetic tree

• parazoa (e.g. Porifera - sponges) have no true tissue, only specialised cells dispersed in the organism, not organised into organs or tissues

• eumatazoa (e.g. the rest of animals) have true tissue, groups of specialised cells grouped together with the same function

how do bilateria and radiata differ

when was this divison on the animal tree of life

• this was the second divison on the tree of life, splitting eumatazoa into 2 groups

• radiata (e.g. Cnidaria) have radial symmetry (symmetry on many planes)

• bilateria (e.g. the rest of animals) have bilateral symmetry (symmetry on one plane, a dorsal (top) and ventral (bottom) side, with anterior and posterior ends) - linked to cephatilisation

how do radiata and bilateria also differ in terms of germ layers

• germ layers are the layers of embryonic tissue that go on to form various tissues and organs as the animal develop

• both types have outer (ectoderm) and inner (endoderm) layers, that give rise to the outer covering, and digestive tube lining (and lining of other organs) respectively

• radiata tend to only have these 2 tissue layers (diploblastic), with a non-living layer between

• bilateria instead tend to have an extra layer between these (3 in total - triploblastic), the mesoderm, which gives rise to many organ systems (muscles (true muscles), skeletal / excretory / circulatory / reproductive systems)

how do coelomates / acoelomates / pseudo-coelomates differ

when was this divison of the phylogenetic tree

• this was the 3rd divison, splitting bilateria into 3 groups

• this is based on presence of a body cavity, a fluid filled space within an organism, seperating the digestive tract from the outer body wall

• acoelomates (e.g. Platyhelminthes) lack a body cavity, the body is solid

• pseudo-coelomates (e.g. Rotifera, Nematoda), have a coelom surrounded by 1 layer of mesoderm, the other border being the digestive tract

• coelomates (e.g. rest of the animals) have a coelom (fluid-filled cavity) surrounded by mesoderm on both sides, which connects at the top and bottom (mesenteries) to suspend internal organs

what are the adaptive advantages of a coelom

• the fluid cushions internal organs, helping to prevent injury

• it also allows these organs to grow and move independently of the outer body wall, and from each other - so they don’t clump and become ineffective

• it cushions to protect offspring developing internally

• it provides a hydrostatic fluid skeleton (is noncompressable), allowing for more effective movement as muscles can work against this

what are the differences between protosomia and deuterostomia groups

what group does this divison branch from

• this group divides coelomates, based on differences of early cell / embryo development

• includes: cleavage pattern, coelom formation, blastopore fate - for embryos

• protosomia have spiral and determinate cleavage, coelom developing from solid masses of mesoderm, and the blastopore forming the mouth (secondary opening becoming the anus)

• deuterostomia have radial and indeterminate cleavage, coelom forming from infolds of the archenteron (embryo inner space) that become mesoderm, and the blastopore forming the anus (secondary opening becoming the mouth)

describe protosomia embryo (Gastrula) development

• cleavage: the embryo (gastrula) undergoes spiral cleavage, so mitotic cell divison occurs in patterns diagonal to the vertical axis

• this is determinate, so each cell formed has a predetermined role in the developing organism

• coelom formation: solid masses of mesoderm (middle tissue layer) split at the blastopore, on either side, forming cavities of coelom within

• blastopore fate: the blastopore (opening to the gastrula cavity, from the outside world), becomes the animal’s mouth, while the secondary opening of the gastrula becomes the anus

describe deuterostomia embryo (Gastrula) development

• cleavage: the embryo (gastrula) undergoes mitotic cell divison in patterns parallel / perpendicular (at 90o angles) to the vertical axis

• these cells formed are indeterminate, so each early formed cell maintains ability to develop into another complete embryo (e.g. a twin could form)

• coelom formation: the archenteron (cavity of the gastrula) infolds, the cells infolding becoming the mesoderm (middle tissue layer), and the hollow cavities within forming the coelom

• blastopore fate: the blastopore (opening of the gastrula internal cavity) develops into the anus of the animal, as the digestive tube develops, while the secondary opening becomes the mouth

why does coelom formation in the gastrula, form two coelom cavities?

coeloms are seperated dorsally and ventrally by the mesoderm, therefore there is technically 2 cavities

name the phyla of focus for this course

name what group they come under

• Porifera (parazoa)

• Cnidaria (radiata)

• Platyhelminthese (acoelomate)

• Annelida (protosomes)

• Mollusca (protosomes)

• Arthropods (protosomes)

• Echinodermata (deuterosomes)

for the Porifera phylum

• habitat, type of organism

• general body structure

• how do they feed

• how do they reproduce

• sponges, marine, some freshwater, sessile

• (parazoa) no true tissue, instead have 2 germ layers (lose collections of unspecialised cells, but they can specialise function), with a non-living gelatinous layer between (mesohyl)

• (asymmetrical) general sponge body is a sac with holes to allow water flow into the central cavity (spongocoel), with a large main opening for outflow (osculum) - no nerves or muscles (but individual cells can sense)

• they filter feed by generating a current in and out of their cavity (via flagellated choanocyte cells which trap food via collar fibres), which is collected and digested by amoebocyte cells, which transport the nutrients to other cells

• to sexually reproduce, they are hermaphrodites that retain their eggs, but release sperm via osculum, which are carried to fertilise other sponges via water

• zygotes form flagellated swimming larvae to disperse

• can asexually reproduce by regeneration of parts broken off the parent

what group / divison are Porifera in

why are they considered basal

• Parazoa - no true tissue

• this is the first divide of the phylogenetic tree, all animals are eumataza and have true tissue

• therefore they are considered basal, as they are most closely related to the animal common ancestor (choanoflagellates)

• evidenced by their molecular and morphological similarities

• e.g. their specialised cells (instead of specialised groups of cells to form tissues) are alike in structure and function to choanoflagellate protists

what divison arose Cnidaria

what type of organisms are they

what groups do they fit into

• they arose from the divison of eumatazoa, into radiata and bilateria (they are radially symmetric while the rest of animals are bilaterally symmetric)

• marine organisms e.g. hydras, jellies, sea anenomies, corals

• (diploblastic): they only have 2 tissue layers, and lack a mesoderm

• (acoelomates): they lack a fluid-filled cavity, instead just have a vascular cavity and tissue

what is the general body structure of Cnidaria

• body is a sac with a central gastrovascular cavity, with one opening (mouth / anus), and 2 true tissue layers (epidermis & gastrodermis), with microfilament bundles as contractile fibres to form muscle-like structures, with a non-living mesoglea between

• no true muscles (no mesoderm) or brains, but have these in simple forms, including an uncentralised ‘nerve net’ associated with simple receptors radially distributed

• have 2 form variations (dimorphic), which depending on the group, are alternated between or just one formed

• the polyps (e.g. sea anenome) are sessile cylinders, which anchor to a substrate at the base of their ‘stalk’, with their mouth facing up to extend tentacles (to feed & defend)

• the medusas (e.g. jellyfish) are motile and float, looking like flattened polyps with bell-shaped bodies, with their head facing down and extending tentacles (to feed & defend)

for Cnidaria

• how do they generally move

• general lifecycle

• how do they feed

• medusa forms move using muscle-like structures (contractile fibres formed by bundles of microfilaments), which work against their gastrovascular cavity (hydrostatic skeleton), when it closes its mouth

• direction controlled by nerve-net

• lifecycles which alternate between medusas / polyps involve a reproducing polyp body, which releases a medusa (asexual), which sexually reproduces, and when fertilised the zygote forms a larvae which adheres to a substrate and develops into the polyp

• those with no medusa form, just skip the medusa part of the reproduction and directly release eggs from the polyp

• they feed via tentacles around the mouth, that capture prey and push it into their cavity, via batteries of cnidocytes, that release a coiled thread held within the nematocyst (within the cnidae organ)

• these may inject poison, or tangle the target, and are triggered by mechanical stimulus (on spikey receptors pointing out)

what are the 4 classes of Cnidaria

how are they different in:

• morphology

• life cycle

hydrozoa, scyphozoa, cubozoa, anthozoa

hydrozoa

• (hydras) alternate polyp and medusa forms, except freshwaters which remain polyp and asexually reproduce by budding, and can form resistant zygotes

• e.g. Portugese Man-of-war

scyphozoa

• (jellyfish) alternate forms but medusa dominates, with a reduced polyp stage

• move by pumping the body up and down (vertically through water column), and horizontally move passively via currents

anthozoa

• (sea anenomies, corals) occur as polyps with no medusas, with each polyp generation building on the previous via their secreted CaCO3 external skeletons

• often hide during the day inside these shells, and tentacle feed during the night using a cilliated groove (siphonoglyph) to move water (therefore food) through the digestive system

• the polyp body is divided into sections by mesentaries (mesoglea extensions), which attach muscle-like strands (aids tentacles)

cubozoa

• (box jellyfish) alternate forms but medusa dominates, with a small polyp stage

• are small cube shapes with at least 4 tentacles, being more complex jellies than schyphozoa (Rapid direct movement, more advanced nervous system, functioning eyes)

what division arose Platyhelminthes

what type of organisms are these

what groups do they belong to

• the divison of bilateria, into coelomates and acoelomates, Platyhelminthes being acoelomates, while the rest of thebilateria were coelomates & pseudo-coelomates

• marine / freshwater / damp terrestrial, e.g. flatworms, parasitic worms (flukes, tapeworms)

• (eumetazoa) they have true tissue

• (bilateria) they are bilaterally symmetric

• (triploblastic) they have 3 tissue layers, a mesoderm between their epidermis and endoderm

• (acoelomates) they lack a fluid-filled internal cavity surrounded by

what is the general body structure of Platyhelminthes

• thin, flat bodies (to increase SA due to lacking specialised gas exchange and circulation organs), containing a gastrovascular cavity with one opening (mouth/anus), surrounded by endoderm, surrounded by mesoderm (packed with organs & middle parenchyma tissue), surrounded by epidermis (ectoderm)

• O2 is taken in, and CO2 & nitrogenous wastes removed, via diffusion, their osmotic balance maintained by cilliated flame cells which can reabsorb ions

• (cephatilisation) have a head end with concentrated sense organs (CNS) eyespots and ganglia, and lateral flaps for smell, with ventral nerve cords throughout the body

what are the two types of lifestyles in Platyhelminthes

what does this mean in terms of morphological differences between classes

• free-living (e.g. tubeworms) and parasitic (e.g. flukes, ectoparasites, and tapeworms)

• this means that body structures greatly differ between classes, depending on if they are parasitic or not (e.g. no gut, anchoring organs, tough coverings),

• also differing behaviour and reproduction / lifecycles (e.g. complex alternation between various hosts throughout lifecycle), due to evolutionary adaptations to suit these vastly different niches

what is the difference between definitive and intermediate hosts (for parasites)

why have intermediate hosts been evolved to be utilised

• (definitive host) refers to an animal harboring adult / sexually mature parasites (e.g. tapeworm adult)

• (intermediate host) refers to an animal harboring young / developing parasites (e.g. tapeworm eggs and larvae)

• intermediate hosts allow parasites to amplify their populations and develop their offspring, so when infecting the definitive host, they effectively attack it

• it also allows effective infiltration of their definitive host, if choosing an intermediate host readily accessible, that provides them easy access to their definitive host (e.g. infect cow, to infect human (eats steak))

what are the 4 classes of phylum Platyhelminthes

what types of organisms are in each

Turbellaria

• e.g. free-living flatworms

Monogenea

• e.g. ectoparasites (monogeneans)

Trematoda

• e.g. flukes (trematodes - parasites)

Cestoidea

• e.g. tapeworms

briefly describe the Turbellaria class of Platyhelminthes

(habitat, lifestyle, body structure, reproduction)

• free-living (non-parasitic) flatworms

• most marine, some freshwater & damp terrestrial, predators / scavengers

• follow the typical Platyhelminthes body structure (are free living so aren’t specially adapted to being parasitic), flat body, CNS at head end, gastrovascular cavity with single opening (anus/mouth)

• move via cilliated ventral epidermis (glide along secreted mucus), or by wave-like swimming using muscles, coordinating via CNS

• reproduce asexually via regeneration (constrict in the middle, each half regenerates), and sexually via cross fertilisation (are hermaphroditic)

briefly describe the Monogenia class of Platyhelminthes

provide an example organism and briefly describe

• e.g. ectoparasites (monogeneans)

• body structure has usual eyespots, mouth, one-way gut, but also involve adaptations of suckers / hooks for host attachment (e.g. fish gills), and to feed on them, with reproductive organs filling their insides (adaptation to reproduce as much as possible)

• simple lifecycles of eggs released into the water, developing into cilliated larvae (oncomiracidium), which infect their definitive host by clinging on, if their host isn’t available, they can turn neotenic (rapidly produce several eggs - adaptation for success)

• e.g. Polystoma integerrimum, endoparasite in common frog bladder, egg released timed with frog egg release, with larvae attaching to tadpole gills (ectoparasitic) until the frog matures and it moves into the bladder (endoparasitic)

describe the Trematoda class of Platyhelminthes

• e.g. flukes (endoparasites)

• wide range of hosts around the world, so various species

• body structure involves adhesive organs as adaptations to remain on host, storage areas in the body for food, and bodies filled with reproductive organs (increase reproductive capacity & success), can be hermaphrodites or diecious

• complex lifecycles involving asexual and sexual reproduction

  • sexual reproduction to form egg in the definitive host, which are released to the environment

  • hatch into larvae (mercidia) which infect an intermediate, and asexually reproduce to form larvae (cercaria), via sporocyst and rediae structures

  • these infect another intermediate asexually reproduce to form the mature (metacerceria)

  • enter the definitive host and sexually reproduce

• therefore allowing for successive amplifications of populations, for successful paratism

name the three examples of Trematodes, and how they differ

Schistosoma (blood flukes)

• distribution over Africa / South America / Asia, amplified by irrigation, climate change, poor hygiene, and unsanitary water

• definitive host is the human (blood vessels of intestine), where they sexually reproduce, and exit via feces

• eggs develop in water, where mercidia infect snails (intermediate), then asexually reproduce to form cercaria, which are released into freshwater, to infect humans (via skin penetration)

Paronomasia (lung flukes)

• distribution in Far East / Central America / Africa

• definitive host is the human (lungs), where they sexually reproduce, eggs exit via mucus / feces into freshwater

• eggs develop into miracidium which infect snails (intermediate), and asexually reproduce to form cercaria, which are released and infect crabs (intermediate), where they asexually reproduce to form metacercaria

• these infect humans, when the crab is ingested, and migrate to lungs

Clonorchis sinesis / Opisthorchis / Fasciola (liver flukes)

• distribution in China, SE Asia, Russia, Canada

• definitive host is humans (liver, pancreas, bile, depending on species), where they sexually reproduce and exit via feces into freshwater

• eggs develop into miracidia and infect snails (intermediate), which asexually reproduce to form cercaria which infect fish (intermediate), which asexually reproduce to form metacercaria

• these infect humans when the fish is ingested

describe the Cestoidea class of Platyhelminthes

provide an example and describe

• e.g. tapeworms, endoparasites in human guts

• body structure is parasitically specialised, no digestive system / gastrovascular cavity (as they live in the gut), instead absorbing nutrients across skin (via microvillae surface potrusions for SA)

• sensory head reduced, replaced by suckers and hooks on scolex to anchor themselves (aided by secretion of chemicals to prevent digestion)

• hermaphroditic, and have long reproductive ‘tails’ (proglottids - sacs of sex organs filled with eggs), that release eggs out the worms end (and pass on via host eces)

• lifecycles involve

  • sexual reproduction in the definitive host

  • egg release to environment, and infection of intermediate upon consumption

  • eggs hatch (oncospheres) and penetrate intestines to enter blood stream, to circulate and embedd into muscles and develop (cysticerci)

  • move to definitive host via ingestion, where they hook onto intestine and mature

• e.g. Taenia species have human definitive hosts, which they infect via cattle / pig intermediates (depending on species) after they eat eggs in grass

• e.g. Echinococcus granulosus (Hydatid tapeworm) have dog definitive hosts, which they infect via sheep / mouse intermediates (form hydatid cysts within - protoscoleces), as the dogs ingest them (can accidentally infect humans via meat consumption, and encyst to attack brain / abodmen, causing death upon rupture)

what divison arose Annelids

what types of organisms are these

what groups do they fit into

• the divison of bilateria, into acoelomates (e.g. Platyhelminthes) / coelomates (e.g. Annelids)

• (bilateria) are bilaterally symmetric

• (triploblastic) have 3 tissue layers

• (coelomates) have an internal fluid cavity

• (protosomes)

• damp terrestrial, salt-water and freshwater worms, e.g. earthworms, leeches, tubeworms (worms with segmented bodies)

general body structure of Annelids

• 3 tissue layers (Ectoderm body cover, endoderm lining the digestive tract, and mesoderm layer surrounding the coelom both sides)

• this provides true muscles, in the form of antagonistic muscle layers (circular & longitudinal), with points of muscle attachment / force exertation on the substrate (chetae-setae protrusions on the epidermis)

• segmented bodies, coelom seperated (fully / partial depending on class) by septae, with repeating and seperate organs (metamerism), with digestive systems / muscle / nerves / circulatory vessels, running the length of the worm

• have nervous systems of giant fibres and nerve cords, with a head end with ganglia

• have an advanced closed vascular system, with blood and pigments to carry materials around the body, using capillaries and heart-like structures (integumentary vessel)

• have an excretory and digestive system with 2 openings (through gut = mouth & anus seperate)

name the 3 classes of Annelids

• Polychaeta (e.g. tubeworms / marine worms)

• Oligochaeta (e.g. earthworms)

• Hirudina (e.g. leeches)

for Polychaete Annelids, describe

• lifestyle

• body structure

• movement

• marine segmented worms, carnivores / scavengers / planktonvores, which live in tubes (secreted mucus mixed with sand & shells) or are freeliving (burrow / crawl on seafloor)

• body structure has well-developed head, rich blood vessels (gill-like structures), segments not completely seperated by septae (some coelom fluid exchange), and each segment has feet (paddle-like parapoida) each where several setae potrude from

• movement is serepentine (rather than relying on fluid skeleton), utilising parapoida, and longitudinal muscles, with alternating segments of (contracted left, stretched right) → (relaxed all) → (contracted right, stretched left)

• the number of segments per wavelength, increases with speed (slow walking = 6-8/wave; rapid crawl = 14/wave; swimming = 40/wave)

for Oligochaete Annelids, describe

• lifestyle

• body structure

• movement

• terrestrial and freshwater segmented worms (e.g. earthworms), that burrow into the ground

• body structure has proper segmentation (coelom seperated by septae), with excretory tube pairs (metanephridia) per segment, a full digestive system, but head is reduced (to burrow) but nerves still present

• for movement, each isolated coelom acts as a hydrostatic fluid skeleton (for muscles to move against), moving forward as the middle segments elongate (long. relaxed, circ. contracted), then the head elongates and the middle fattens (long. constrict, circ. relax), and it repeats to pull the body along

• the thick sections anchor to the ground via setae, to stop slipping backwards, and help push forward (have muscle attachments to rotate, retractors)

• to burrow, the head pushes soil particles, setae anchor against the burrow (thick segments), then other segments elongate

• are hermaphrodites so cross-fertilise by exchanging and storing sperm, while the clitellium (organ, band-like structure) secretes a mucus cocoon, which picks up eggs and sperm as it moves along the body (fertilisation) and slips off (can also asexually reproduce via fragmentation and regeneration of segments)

for Hirudina Annelids, describe

• lifestyle

• body structure

• movement

• leeches, freshwater and damp terrestrial, feeding on invertebrates / vertebrate blood (can be parasitic)

• body structure has segmentation (34 segments) but no septae so coelom is continuous, and no chetae/seate, instead have posterior and anterior suckers (attachment point for movement and feeding)

• feeding uses bladelike jaws on sucker, or via secretion of digestive enzymes, then anticoagulent (hirudin) for max. blood flow

• movement untilises suckers as anchor points, and contraction / relaxation of circular / longitudinal muscles, along with their continuous coelom as a hydrostatic fluid skeleton

  • posterior sucker attaches, body elongates by contracting circular muscles (long & thin)

  • anterior sucker attaches, post. sucker detaches, and body is pulled towards ant. sucker by contraction of longitudinal muscles (short & thick)

  • post. sucker touches body, then reattaches, and the cycle repeats to enable movement

what divison arose Mollusca

what groups do they fit into?

what type of organisms are these?

• the divison of coelomates, into protosomes and deuterosomes (Mollusca being protosomes like Annelids & Arthropods)

• (bilateria) bilateral symmetry

• (triploblastic) three tissue layers

• (coelomates) have a fluid filled cavity

• (protosomes)

• these are mostly marine & some freshwater/terrestrial, soft-bodied animals covered by a shell (e.g. gastropods, snails, slufs, oysters, clams, octopuses, squids)

describe the general body structure of Molluscs

• groups share a similar body plan (adapted differently to each lifestyle), soft-body (visceral mass - organs), with a muscular foot (locomotion), covered by a mantle - which secretes their shell (CaCO3)

• this shell creates a point for muscles to work against

• it also creates a water-filled chamber (mantle cavity) to protect gills / anus / genitals / excretory pores

• have nervous systems with sense organs at the head, also containing the mouth & radula

• have circulatory system (open except in cephlapods), with muscular hearts to pump blood to tissues

name the 4 classes of Molluscs focused on for this course

Polyplacophora

• e.g. Chitons

Gastropoda

• e.g. slugs, snails

Bivalva

• e.g. clams, mussels, scallops, oysters

Cephalopoda

• e.g. squid, octopuses, cuttlefish, nautilus

for the Polyplacophora class of Molluscs, describe

• lifestyle

• any adaptation of basic Mollusc body plan

• feeding

• movement

• e.g. chitons, marine rock-dwellers

• shell has 8 dorsal plates, usually oval-shaped

• muscular foot grips rocky substrate tightly, which they creep along

• are grazers, using the radula to scape algae of their rock

for the Gastropoda class of Molluscs, describe

• lifestyle

• any adaptation of basic Mollusc body plan

• feeding

• movement

• e.g. snails, limpets, topshells, slugs, - marine/ freshwater/ terrestrial

• typically spiralled / conical (or flat) shell in 1 piece, with a rotated visceral mass (mantle cavity at the front, above the head) - occurring in embryonic development (torsion)

• feed via radula and mouth

• move via waves of muscular contraction along the foot which is in contact with the substrate w/ a layer of mucus

  • direct movement = waves in the same direction as movement (post→ant), via contractions of longitudinal / dorsal ventral muscles

  • retrograde movement = waves in opposite direction to movement (ant→post), via contractions of transverse muscles → longitudinal muscles

  • ditactic movement = two sides of the foot have independent waves, which can be direct or retrograde

for the Bivalvia class of Molluscs, describe

• lifestyle

• any adaptation of basic Mollusc body plan

• feeding

• movement

• e.g. clam, mussel, oyster, scallops, - sedentary freshwater / marine animals, anchored to rocks/ docks /boats (via secreted threads)

• filter-feeders via mucus coated gills trapping food particles, moved to the mouth via cillia

• shell in 2 parts (2 valves = bivalve) with a hinge at mid-dorsal (powerful addeuctor muscles to tightly close, protecting visceral mass), and water flow generated inside via cillia

• foot is reduced & hatchet shaped, but can be extended out the shell, utilised for digging / anchoring / burrowing

• movement not creeping/crawling, instead

  • burrowing = worm-like using the hydrostatic skeleton (via shell), foot contracts to burrow → valves expand → foot expands to anchor → valves contract and are pulled towards the foot (alternating)

  • swimming = in short bursts as valves flap (open/close), shooting water out the mantle cavity

for the Cephalopoda class of Molluscs, describe

• lifestyle

• any adaptation of basic Mollusc body plan

• feeding

• movement

• e.g. squid, octopus, nautilis, cuttlefish, - marine only, scurrying and camoflaging to seafloor, for active predatecous lifestyle

• shell heavily reduced to a rudimentary internal one, protection instead given by their collagen-rich mantle

• food modified to form the ‘head-foot’, with tentacles / arms surrounding the mouth, and to form the siphon (mantle cavity opening)

• feed by rapidly darting towards prey, capturing with tentacles, and biting / injecting with poison to kill

• well-developed nervous system with complex brain & sense organs (e.g. eye)

• closed circulatory system with 3 hearts (systemic & branchial x2) that pump blood via vessels (allows efficient gas exchange / bodily transport for their larger bodies)

• movement is rapid dartings, done by contracting the mantle cavity and shooting water through the siphon (aimed for different directions of movement0

what divison arose Arthropods

what groups do they fit under

what type of organisms are these

• the divison of Coelomates into Protosomes and Deuterosomes (Arthropods being Protosomes, along with Annelids & Molluscs)

• (bilateria)

• triploblastic)

• (coelomates)

• (protosomes)

• dominant / most successful phylum of animals, in nearly all habitats, due to: exoskeletons / jointed appendages / segmentation (e.g. insects, arachnids, crustaceans)

describe the general body structure of Arthropods

• segmented bodies, segments and their (jointed) appedanges grouped into specialised functions (head, thorax, abdomen)

• well-developed sense organs at the anterior (Cephatilisation) with eyes, olfactory receptors, antennae

• open circulatory systems with a heart pumping hemolympth through short arteries, into the sinuses (hemocel) surrounding tissue areas and organs, then back via valved pores (transport of materials NOT oxygen)

• specialised GE organs (gills in aquatic, tracheal systems in terrestrial)

• coelom reduced but still present, enclosed by an exoskeleton (hardened cuticle layer)

describe the Arthropod exoskeleton

• formed from multiple different (laminated) layers of the cuticle, above the epidermis, secreted by the hypodermis (integumentary epithelial cells, within the epidermis)

• the epicuticle (outermost layer) is made of proteins / wax

• the procuticle (inner layers) is made of protein & chitin, bound with glycoproteins

  • exocuticle (rigid, missing around joints, rupturing to molt, coloured by melanin pigments) - thin

  • mesocuticle (part of the endocuticle) - medium

  • endocuticle - thick

• infoldings act as muscle attachments to create a leaver system for movement

• may have one/two pairs of wings emerging from the exoskeleton, on the dorsal side of the thorax

list the advantages and disadvantages of an Arthropod exoskeleton

advantages

• impermeable to water = reduces water loss, allowing terrestrial colonisation (due to thickness, hardness, & components like wax)

• aids movement = provides muscle attachment, and a hard skeleton for muscles to work against, allowing for effective movement

• protection = hardiness and many layers provide protection

disadvantages

• prevents growth = due to rigid skeleton, so must molt (ecdysis) via removing it and secreting a larger one, leaving them vulnerable in the process (soft body exposed)

• limits growth = is heavy so potentially prevents evolution to large sizes

• requires specialised organs = for transport of materials into the body, due to skeleton preventing passage in and out (e.g. respiratory, excretory)

• requires special sense organs = sensing also blocked by this skeleton

describe the movement of Arthropods (flying & walking)

walking

• thrust and recovery alternating strokes of legs (forward & backwards) against the ground

• stride length differences allow for different speeds, bigger spaces between points of ground contact, increase speed

• Arthropods with short legs, achieve longer strides by using legs further apart for muscle attachment, the distance increasing speed

flying

• occurs with alternating up and down movements of the wings, as alternating muscles contract/relax, to create leverage against the tergum (top of body)

  • up = longitudinal relaxed, dorsoventral contracted, tergum lowered

  • down = longitudinal contracted, dorsoventral relaxed, tergum raised

• this is aided by forward and backward wing movements, creating thrust / lift / direction control, holding wings at different angles allows either ellipse, or figure eight, movement of the wing tips

• wing beat frequency, determines flight speed and manoueverability, these increasing with beat frequency

name the 5 classes of Arthropods

Arachnida

• e.g. spiders, scorpions

Diplopoda

• e.g. millipedes

Chilopoda

• e.g. centipedes

Insecta

• e.g. insects

Crustacea

• e.g. lobsters, crayfish, prawns, crabs

how may have flight evolved in terrestrial insect Arthropods

• may have evolved as extensions of the cuticle to help absorb heat, which were modified and selected for flight as they allowed gliding off vegetation (Effective movement & evasion)

• may have evolved from modified gills or swimming appendages in aquatic insects, as they provided advantage on land

what distinguishes the Arachnida class of Arthropods?

• type of organism

• lifestyle

• body structure

• e.g. spiders, scorpions

• body has one / two main parts (segments), with 6 pairs of appendages (4 pairs of walking legs, 2 pairs of mouthpieces)

what distinguishes the Diplopoda class of Arthropods?

• type of organism

• lifestyle

• body structure

• e.g. millipedes

• terrestrial (maybe among earliest land animals), herbivores (decaying leaves / plant matter)

• wormlike, many segments, 2 pairs of short walking legs per segment

• distinct head with antennae & mouthpieces

what distinguishes the Chilopoda class of Arthropods?

• type of organism

• lifestyle

• body structure

• e.g. centipedes

• terrestrial, carnivores

• long with many segments, 1 pair of short walking legs on each segment, with the anterior most body segment having these modfied as poision claws (paralyse prey & for defence)

• distinct head with antennae and 3 pairs of appendages modified as mouthparts (jaw / mandibles)

what distinguishes the Insecta class of Arthropods?

• type of organism

• lifestyle

• body structure

• e.g. insects

• mostly terrestrial

• outermost layer of exoskeleton (epicuticle) is embedded with waxes & oils/lipids, so is less rigid, but less water/gas permeable (terrestrial adaptation)

• body segments divided into head / thorax / abdomen regions, with total 3 pairs of walking legs, and usually 2 pairs of wings, with antennae and mouthpieces (feeding)

what distinguishes the Crustacea class of Arthropods?

• type of organism

• lifestyle

• body structure

• e.g. lobsters, crayfish, prawns, crabs

• mostly marine

• exoskeleton epicuticle (outermost layer) embedded with mineral salts (CaCo3 & calcium phosphate), creating a rigid calcified layer

• body segments arranged in specialised groups of 2/3 parts (head/thorax/abdomen), with 3 or more pairs of legs total, and a head end with mouthparts for chewing and antennae

what divison arose Echinodermata

what groups do they belong to

what kind of organisms are these

• the division of Coelomates into Protosomes and Deuterosomes (Echinoderms being Deuterosomes, alongisde Chordata - vertebrates & mammals)

• (bilateria)

• (triploblastic)

• (coelomates)

• (deuterosomes)

• e.g. sea stars, sea urchins, sea cucumbers

describe the general body structure of Echinodermata

• body structures (internal/external) radiate from the centre (often in fives) - which is secondary radial symmetry occurring in adult maturation (bilaterial to begin with)

• have the unique water vascular system, storing water as a fluid body for muscles to work against

  • a network of hydraulic ((fluid moving in a confined space under pressure) ring canals (centre) connecting to radial → lateral canals (in arms)

  • these branch into tube feet (poida: fluid-filled extensions out the epidermis), which have mucus glands and suckers, with longit. muscle in the walls

  • where these connect to the canals, is an enlarged sphere (ampulla) with a valve to the canal, and musculed walls (circ& long)

  • (movement) when ampulla muscles contract, water moves into the poida, and they elongate, and when poida contract, water moves to the ampulla, and the poida contract

  • (feeding) they pass food to the centre mouth

  • (gas exchange) site of GE is the tube feet membranes via diffusion (thin surfaces)

• pinchers (pedicellariae) surrounding the tube feet protect them from other organisms

• have an endoskeleton

describe the Echinodermata endoskeleton

what are the advantages of this adaptation

• endoskeleton made up of hard calcaerous plates, with skeletal potrusions

• this is covered by a thin skin (echinoderm), prickly due to these potrusions

• this endoskeleton is advantageous because

  • it provides body support in air and water

  • provides muscle attachment, and a body for muscles to work against, aiding movement

  • it protects brain and internal organs

describe the reproduction of Echinoderms

• diecious (males & females)

• gametes released into water, which fertilise the other gender

• larvae and young Echinoderms show bilateral symmetry (bilateria), which develops via metamorphosis into secondary radial symmetry at maturity (not truly radial) - adaptation to sessile lifestyle

• can asexually reproduce from regeneration off chopped off limbs

name the 6 classes of Echinoderms

Asteroidea

• e.g. sea stars

Ophiuroidea

• e.g. brittle stars

Echinoidea

• e.g. sea urchins, sand dollars

Crinoidea

• e.g. sea lillies, feather stars

Holothuroidea

• e.g. sea cucumbers

Concentricyloidea

• e.g. sea dasies

how to distinguish Asteroidea of Echinoderms

• e.g. sea stars

• have a central disk (mouth, stomach, anus), with 5 arms radiating out (gills, digestive glands, gonads) each with pinchers and tube feet

• this allows each arm to suction onto substrate with tube feet, allowing creeping slowly, via hydraulic (fluid moving in a confined space under pressure) and muscular action

• can asexually reproduce to regenerate removed arms, or regenerate a new body from a removed arm

• can feed via vomiting out their stomach, to digest prey externally using digestive enzymes, which are then reabsorbed to gain nutrients (E.g. into a mussel shell)

how to distinguish Ophiuroidea of Echinoderms

• e.g. brittle stars

• body structure of a distinct central disk, radiating out 5 long / thin / flexible arms

• these arms lack suckers, so they instead lash them around via muscles to move via serpentine movements (through the water column)

• to feed, some are suspension feeders, some are scavengers / predators

how to distinguish Echindoidea of Echinoderms

• e.g. sea urchins, sand dollars

• body structures roughly spherical with long spines (urchins), or flattened discs (dollars)

• have no arms, but 5 rows of tube feet on the body (and urchins can move via pivoting of spikes)

• to feed, (urchins) complex jaw-like (aristotle’s lantern) structures are used which surround their mouth - adapted for seaweed consumption (are grazers)

• (urchins) populations cluster and form barrens where they graze on seaweed together

how to distinguish Crinoidea of Echinoderms

• e.g. sea lillies, feather stars - deep sea dwellers, showing very conservative evolution (similar to 500myo fossils)

• (sea lillies) body structures of a central disk and arms, attached to the substrate by stalks

• (feather stars) central disk and long flexible arms to crawl

• feed by suspension feeding using arms

how to distinguish Holothuroidea of Echinoderms

• e.g. sea cucumbers

• body structure (quite different from other Echinoderms) lacks spines/spikes, with a reduced endoskeleton, and an elongated oral-aboral axis (body is just a mouth and gut tube)

• body structure does include tube feet, 5 rows, some with function of feeding tentacles around the mouth for suspension or deposit feeding

what is a hydrostatic skeleton

• how does this allow movement

• where is this advantageous

• how is this disadvantageous

• fluid in a closed body compartment, held under pressure

• movement is controlled by changing shape of the compartment, therefore changing the properties of this fluid

• advantegous in aquatic environments, and to burrowing and crawling movements

• disadvantageous as it prevents running and walking, and is probably less suited for terrestrial life