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3.2: Pre-Lab 3: Insect Development - Biology

3.2: Pre-Lab 3: Insect Development - Biology


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The rigid exoskeleton, also called the “cuticle”, of insects enables them to do many things, but is an obstacle to growth. In order to grow, an insect must periodically shed its exoskeleton and grow a new one that is larger. The process whereby a new cuticle is formed and the old one is shed is called molting. Molting is a complex process which is controlled by hormones.

Insect Cuticle: Draw the layers of the insect cuticle, labeling the following components: epidermis, endocuticle, exocuticle, inner epicuticle, outer epicuticle, wax layer and cement layer.

During insect growth and molting, each successive stage may appear similar to the preceding stage, or the appearance may change from stage to stage. This change in form from molt to molt is called metamorphosis. There are four types of metamorphosis:

  • Ametaboly — No marked change in form between a newly hatched nymph and the adult. The adult differs from the nymph only in size and in having reproductive structures. (Ex. Collembola)
  • Paurometaboly — The nymph does not closely resemble the adult because it lives in the water, breathes through gills, and has gradually enlarging external wings. Odonata)
  • Hemimetaboly — The nymph resembles the adult, except in size and the absence of wings and reproductive structures. Wing buds develop externally. Orthoptera)
  • Holometaboly — The larva does not resemble the adult form and frequently differs in feeding habits and habitat (where it lives). There is a pupal stage intermediate between the last larval stage and the adult. Wing development is internal.

As the insect develops, an interaction between three hormones regulates development in time with ecdysis events in response to environmental and physiological cues.

When the brain receives the appropriate cue, which may be soil temperature for an overwintering insect, day length, or any number of factors, it causes the brain to release Prothoracicotropic Hormone, also called PTTH or simply “brain hormone”. PTTH acts on the prothoracic gland(hence the long name), stimulating the gland to release the hormone Ecdysone. When released, ecdysone triggers an ecdysis event.

The final hormone in the interaction regulates the degree of maturity of the stages between ecdysis events, called “instars”. Juveniles and larvae may go through several immature instars, molting between each and maturing slightly with each stage before becoming a mature adult. As they develop, a special section of the brain called the corpus allatum secretes Juvenile Hormone, known simply as “JH”. The more JH present in the insect, the more immature the tissues remain. JH levels are high in early instar immature insects, and tapers off as the insect matures: less Juvenile Hormone means a less juvenile insect. Juvenile Hormone is in the lowest concentration in the last stage of immaturity: the last juvenile instar or the pupal stage for holometabolous insects. The absence of juvenile hormone at the last ecdysis event allows mature adult tissues to form, including functional wings and mature reproductive systems.

There are a few further conditions that may vary development. Define the following, and give an insect example.

  1. Diapause
  1. Hypermetabola
  1. Sub-imago

The more recently derived (evolved) insect orders are the holometabolous orders, while ametabola, then hemi- and paurometabola are considered more primitive conditions. With the energetic expenditure of metamorphosis and the extended time spent in a vulnerable pupal stage, why do you supposed was favored as a life history strategy and preserved evolutionarily? What are the benefits or reasons for metamorphosis? Defend your answer.


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Contents

There are over 800 extant species of cephalopod, [4] although new species continue to be described. An estimated 11,000 extinct taxa have been described, although the soft-bodied nature of cephalopods means they are not easily fossilised. [5]

Cephalopods are found in all the oceans of Earth. None of them can tolerate fresh water, but the brief squid, Lolliguncula brevis, found in Chesapeake Bay, is a notable partial exception in that it tolerates brackish water. [6] Cephalopods are thought to be unable to live in fresh water due to multiple biochemical constraints, and in their 400+ million year existence have never ventured into fully freshwater habitats. [7]

Cephalopods occupy most of the depth of the ocean, from the abyssal plain to the sea surface. Their diversity is greatest near the equator (

40 species retrieved in nets at 11°N by a diversity study) and decreases towards the poles (

5 species captured at 60°N). [8]

Nervous system and behavior Edit

Cephalopods are widely regarded as the most intelligent of the invertebrates, and have well developed senses and large brains (larger than those of gastropods). [9] The nervous system of cephalopods is the most complex of the invertebrates [10] [11] and their brain-to-body-mass ratio falls between that of endothermic and ectothermic vertebrates. [8] : 14 Captive cephalopods have also been known to climb out of their aquaria, maneuver a distance of the lab floor, enter another aquarium to feed on the crabs, and return to their own aquarium. [12]

The brain is protected in a cartilaginous cranium. The giant nerve fibers of the cephalopod mantle have been widely used for many years as experimental material in neurophysiology their large diameter (due to lack of myelination) makes them relatively easy to study compared with other animals. [13]

Many cephalopods are social creatures when isolated from their own kind, some species have been observed shoaling with fish. [14]

Some cephalopods are able to fly through the air for distances of up to 50 m. While cephalopods are not particularly aerodynamic, they achieve these impressive ranges by jet-propulsion water continues to be expelled from the funnel while the organism is in the air. [15] The animals spread their fins and tentacles to form wings and actively control lift force with body posture. [16] One species, Todarodes pacificus, has been observed spreading tentacles in a flat fan shape with a mucus film between the individual tentacles [16] [17] while another, Sepioteuthis sepioidea, has been observed putting the tentacles in a circular arrangement. [18]

Senses Edit

Cephalopods have advanced vision, can detect gravity with statocysts, and have a variety of chemical sense organs. [8] : 34 Octopuses use their arms to explore their environment and can use them for depth perception. [8]

Vision Edit

Most cephalopods rely on vision to detect predators and prey, and to communicate with one another. [19] Consequently, cephalopod vision is acute: training experiments have shown that the common octopus can distinguish the brightness, size, shape, and horizontal or vertical orientation of objects. The morphological construction gives cephalopod eyes the same performance as sharks' however, their construction differs, as cephalopods lack a cornea, and have an everted retina. [19] Cephalopods' eyes are also sensitive to the plane of polarization of light. [20] Unlike many other cephalopods, nautiluses do not have good vision their eye structure is highly developed, but lacks a solid lens. They have a simple "pinhole" eye through which water can pass. Instead of vision, the animal is thought to use olfaction as the primary sense for foraging, as well as locating or identifying potential mates.

Surprisingly, given their ability to change color, all octopuses [21] and most cephalopods [22] [23] are considered to be color blind. Coleoid cephalopods (octopus, squid, cuttlefish) have a single photoreceptor type and lack the ability to determine color by comparing detected photon intensity across multiple spectral channels. When camouflaging themselves, they use their chromatophores to change brightness and pattern according to the background they see, but their ability to match the specific color of a background may come from cells such as iridophores and leucophores that reflect light from the environment. [24] They also produce visual pigments throughout their body, and may sense light levels directly from their body. [25] Evidence of color vision has been found in the sparkling enope squid (Watasenia scintillans), [22] [26] which achieves color vision by the use of three distinct retinal molecules: A1, most sensitive to green-blue (484 nm) A2, to blue-green (500 nm), and A4, to blue (470 nm), which bind to its opsin. [27]

In 2015, a novel mechanism for spectral discrimination in cephalopods was described. This relies on the exploitation of chromatic aberration (wavelength-dependence of focal length). Numerical modeling shows that chromatic aberration can yield useful chromatic information through the dependence of image acuity on accommodation. The unusual off-axis slit and annular pupil shapes in cephalopods enhance this ability. [28]

Photoreception Edit

In 2015, molecular evidence was published indicating that cephalopod chromatophores are photosensitive reverse transcription polymerase chain reactions (RT-PCR) revealed transcripts encoding rhodopsin and retinochrome within the retinas and skin of the longfin inshore squid (Doryteuthis pealeii), and the common cuttlefish (Sepia officinalis) and broadclub cuttlefish (Sepia latimanus). The authors claim this is the first evidence that cephalopod dermal tissues may possess the required combination of molecules to respond to light. [29]

Hearing Edit

Some squids have been shown to detect sound using their statocysts, [30] but, in general, cephalopods are deaf.

Use of light Edit

Most cephalopods possess an assemblage of skin components that interact with light. These may include iridophores, leucophores, chromatophores and (in some species) photophores. Chromatophores are colored pigment cells that expand and contract in accordance to produce color and pattern which they can use in a startling array of fashions. [8] [29] As well as providing camouflage with their background, some cephalopods bioluminesce, shining light downwards to disguise their shadows from any predators that may lurk below. [8] The bioluminescence is produced by bacterial symbionts the host cephalopod is able to detect the light produced by these organisms. [31] Bioluminescence may also be used to entice prey, and some species use colorful displays to impress mates, startle predators, or even communicate with one another. [8]

Coloration Edit

Cephalopods can change their colors and patterns in milliseconds, whether for signalling (both within the species and for warning) or active camouflage, [8] as their chromatophores are expanded or contracted. [32] Although color changes appear to rely primarily on vision input, there is evidence that skin cells, specifically chromatophores, can detect light and adjust to light conditions independently of the eyes. [33] The octopus changes skin color and texture during quiet and active sleep cycles. [34]

Cephalopods can use chromatophores like a muscle, which is why they can change their skin hue as rapidly as they do. Coloration is typically stronger in near-shore species than those living in the open ocean, whose functions tend to be restricted to disruptive camouflage. [8] : 2 These chromatophores are found throughout the body of the octopus, however, they are controlled by the same part of the brain that controls elongation during jet propulsion to reduce drag. As such, if jetting octopuses can turn pale because the brain is unable to achieve both controlling elongation and controlling the chromatophores. [35] Most octopuses mimic select structures in their field of view rather than becoming a composite color of their full background. [36]

Evidence of original coloration has been detected in cephalopod fossils dating as far back as the Silurian these orthoconic individuals bore concentric stripes, which are thought to have served as camouflage. [37] Devonian cephalopods bear more complex color patterns, of unknown function. [38]

Ink Edit

With the exception of the Nautilidae and the species of octopus belonging to the suborder Cirrina, [39] all known cephalopods have an ink sac, which can be used to expel a cloud of dark ink to confuse predators. [21] This sac is a muscular bag which originated as an extension of the hindgut. It lies beneath the gut and opens into the anus, into which its contents – almost pure melanin – can be squirted its proximity to the base of the funnel means the ink can be distributed by ejected water as the cephalopod uses its jet propulsion. [21] The ejected cloud of melanin is usually mixed, upon expulsion, with mucus, produced elsewhere in the mantle, and therefore forms a thick cloud, resulting in visual (and possibly chemosensory) impairment of the predator, like a smokescreen. However, a more sophisticated behavior has been observed, in which the cephalopod releases a cloud, with a greater mucus content, that approximately resembles the cephalopod that released it (this decoy is referred to as a Pseudomorph). This strategy often results in the predator attacking the pseudomorph, rather than its rapidly departing prey. [21] For more information, see Inking behaviors.

The ink sac of cephalopods has led to a common name of "inkfish", [40] formerly the pen-and-ink fish. [41]

Circulatory system Edit

Cephalopods are the only molluscs with a closed circulatory system. Coleoids have two gill hearts (also known as branchial hearts) that move blood through the capillaries of the gills. A single systemic heart then pumps the oxygenated blood through the rest of the body. [42]

Like most molluscs, cephalopods use hemocyanin, a copper-containing protein, rather than hemoglobin, to transport oxygen. As a result, their blood is colorless when deoxygenated and turns blue when exposed to air. [43]

Respiration Edit

Cephalopods exchange gases with the seawater by forcing water through their gills, which are attached to the roof of the organism. [44] : 488 [45] Water enters the mantle cavity on the outside of the gills, and the entrance of the mantle cavity closes. When the mantle contracts, water is forced through the gills, which lie between the mantle cavity and the funnel. The water's expulsion through the funnel can be used to power jet propulsion. If respiration is used concurrently with jet propulsion, large losses in speed or oxygen generation can be expected. [46] [47] The gills, which are much more efficient than those of other mollusks, are attached to the ventral surface of the mantle cavity. [45] There is a trade-off with gill size regarding lifestyle. To achieve fast speeds, gills need to be small – water will be passed through them quickly when energy is needed, compensating for their small size. However, organisms which spend most of their time moving slowly along the bottom do not naturally pass much water through their cavity for locomotion thus they have larger gills, along with complex systems to ensure that water is constantly washing through their gills, even when the organism is stationary. [44] The water flow is controlled by contractions of the radial and circular mantle cavity muscles. [48]

The gills of cephalopods are supported by a skeleton of robust fibrous proteins the lack of mucopolysaccharides distinguishes this matrix from cartilage. [49] [50] The gills are also thought to be involved in excretion, with NH4 + being swapped with K + from the seawater. [45]

Locomotion and buoyancy Edit

While most cephalopods can move by jet propulsion, this is a very energy-consuming way to travel compared to the tail propulsion used by fish. [51] The efficiency of a propellor-driven waterjet (i.e. Froude efficiency) is greater than a rocket. [52] The relative efficiency of jet propulsion decreases further as animal size increases paralarvae are far more efficient than juvenile and adult individuals. [53] Since the Paleozoic era, as competition with fish produced an environment where efficient motion was crucial to survival, jet propulsion has taken a back role, with fins and tentacles used to maintain a steady velocity. [5] Whilst jet propulsion is never the sole mode of locomotion, [5] : 208 the stop-start motion provided by the jets continues to be useful for providing bursts of high speed – not least when capturing prey or avoiding predators. [5] Indeed, it makes cephalopods the fastest marine invertebrates, [8] : Preface and they can out-accelerate most fish. [44] The jet is supplemented with fin motion in the squid, the fins flap each time that a jet is released, amplifying the thrust they are then extended between jets (presumably to avoid sinking). [53] Oxygenated water is taken into the mantle cavity to the gills and through muscular contraction of this cavity, the spent water is expelled through the hyponome, created by a fold in the mantle. The size difference between the posterior and anterior ends of this organ control the speed of the jet the organism can produce. [54] The velocity of the organism can be accurately predicted for a given mass and morphology of animal. [55] Motion of the cephalopods is usually backward as water is forced out anteriorly through the hyponome, but direction can be controlled somewhat by pointing it in different directions. [56] Some cephalopods accompany this expulsion of water with a gunshot-like popping noise, thought to function to frighten away potential predators. [57]

Cephalopods employ a similar method of propulsion despite their increasing size (as they grow) changing the dynamics of the water in which they find themselves. Thus their paralarvae do not extensively use their fins (which are less efficient at low Reynolds numbers) and primarily use their jets to propel themselves upwards, whereas large adult cephalopods tend to swim less efficiently and with more reliance on their fins. [53]

Early cephalopods are thought to have produced jets by drawing their body into their shells, as Nautilus does today. [58] Nautilus is also capable of creating a jet by undulations of its funnel this slower flow of water is more suited to the extraction of oxygen from the water. [58] When motionless, Nautilus can only extract 20% of oxygen from the water. [59] The jet velocity in Nautilus is much slower than in coleoids, but less musculature and energy is involved in its production. [60] Jet thrust in cephalopods is controlled primarily by the maximum diameter of the funnel orifice (or, perhaps, the average diameter of the funnel) [61] : 440 and the diameter of the mantle cavity. [62] Changes in the size of the orifice are used most at intermediate velocities. [61] The absolute velocity achieved is limited by the cephalopod's requirement to inhale water for expulsion this intake limits the maximum velocity to eight body-lengths per second, a speed which most cephalopods can attain after two funnel-blows. [61] Water refills the cavity by entering not only through the orifices, but also through the funnel. [61] Squid can expel up to 94% of the fluid within their cavity in a single jet thrust. [52] To accommodate the rapid changes in water intake and expulsion, the orifices are highly flexible and can change their size by a factor of twenty the funnel radius, conversely, changes only by a factor of around 1.5. [61]

Some octopus species are also able to walk along the seabed. Squids and cuttlefish can move short distances in any direction by rippling of a flap of muscle around the mantle.

While most cephalopods float (i.e. are neutrally buoyant or nearly so in fact most cephalopods are about 2–3% denser than seawater [14] ), they achieve this in different ways. [51] Some, such as Nautilus, allow gas to diffuse into the gap between the mantle and the shell others allow purer water to ooze from their kidneys, forcing out denser salt water from the body cavity [51] others, like some fish, accumulate oils in the liver [51] and some octopuses have a gelatinous body with lighter chloride ions replacing sulfate in the body chemistry. [51]

Squids are the primary sufferers of negative buoyancy in cephalopods. The negative buoyancy means that some squids, especially those whose habitat depths are rather shallow, have to actively regulate their vertical positions. This means that they must expend energy, often through jetting or undulations, in order to maintain the same depth. As such, the cost of transport of many squids are quite high. That being said, squid and other cephalopod that dwell in deep waters tend to be more neutrally buoyant which removes the need to regulate depth and increases their locomotory efficiency. [63] [64]

The Macrotritopus defilippi, or the sand-dwelling octopus, was seen mimicking both the coloration and the swimming movements of the sand-dwelling flounder Bothus lunatus to avoid predators. The octopuses were able to flatten their bodies and put their arms back to appear the same as the flounders as well as move with the same speed and movements. [65]

Females of two species, Ocythoe tuberculata and Haliphron atlanticus, have evolved a true swim bladder. [66]

Octopus vs. Squid Locomotion Edit

Two of the categories of cephalopods, octopus and squid, are vastly different in their movements despite being of the same class. Octopuses are generally not seen as active swimmers they are often found scavenging the sea floor instead of swimming long distances through the water. Squids, on the other hand, can be found to travel vast distances, with some moving as much as 2000 km in 2.5 months at an average pace of 0.9 body lengths per second. [67] There is a major reason for the difference in movement type and efficiency: anatomy.

Both octopuses and squids have mantles (referenced above) which function towards respiration and locomotion in the form of jetting. The composition of these mantles differ between the two families, however. In octopuses, the mantle is made up of three muscle types: Longitudinal, radial, and circular. The longitudinal muscles run parallel to the length of the octopus and they are used in order to keep the mantle the same length throughout the jetting process. Given that they are muscles, it can be noted that this means the octopus must actively flex the longitudinal muscles during jetting in order to keep the mantle at a constant length. The radial muscles run perpendicular to the longitudinal muscles and are used to thicken and thin the wall of the mantle. Finally, the circular muscles are used as the main activators in jetting. They are muscle bands that surround the mantle and expand/contract the cavity. All three muscle types work in unison to produce a jet as a propulsion mechanism. [67]

Squids do not have the longitudinal muscles that octopus do. Instead, they have a tunic. [67] This tunic is made of layers of collagen and it surrounds the top and the bottom of the mantle. Because they are made of collagen and not muscle, the tunics are rigid bodies that are much stronger than the muscle counterparts. This provides the squids some advantages for jet propulsion swimming. The stiffness means that there is no necessary muscle flexing to keep the mantle the same size. In addition, tunics take up only 1% of the squid mantle's wall thickness, whereas the longitudinal muscle fibers take up to 20% of the mantle wall thickness in octopuses. [67] Also because of the rigidity of the tunic, the radial muscles in squid can contract more forcefully.

The mantle is not the only place where squids have collagen. Collagen fibers are located throughout the other muscle fibers in the mantle. These collagen fibers act as elastics and are sometimes named "collagen springs". [67] As the name implies, these fibers act as springs. When the radial and circular muscles in the mantle contract, they reach a point where the contraction is no longer efficient to the forward motion of the creature. In such cases, the excess contraction is stored in the collagen which then efficiently begins or aids in the expansion of the mantle at the end of the jet. In some tests, the collagen has been shown to be able to begin raising mantle pressure up to 50ms before muscle activity is initiated. [67]

These anatomical differences between squid and octopuses can help explain why squid can be found swimming comparably to fish while octopuses usually rely on other forms of locomotion on the sea floor such as bipedal walking, crawling, and non-jetting swimming. [68]

Shell Edit

Nautiluses are the only extant cephalopods with a true external shell. However, all molluscan shells are formed from the ectoderm (outer layer of the embryo) in cuttlefish (Sepia spp.), for example, an invagination of the ectoderm forms during the embryonic period, resulting in a shell (cuttlebone) that is internal in the adult. [69] The same is true of the chitinous gladius of squid [69] and octopuses. [70] Cirrate octopods have arch-shaped cartilaginous fin supports, [71] which are sometimes referred to as a "shell vestige" or "gladius". [72] The Incirrina have either a pair of rod-shaped stylets or no vestige of an internal shell, [73] and some squid also lack a gladius. [74] The shelled coleoids do not form a clade or even a paraphyletic group. [75] The Spirula shell begins as an organic structure, and is then very rapidly mineralized. [76] Shells that are "lost" may be lost by resorption of the calcium carbonate component. [77]

Females of the octopus genus Argonauta secrete a specialized paper-thin egg case in which they reside, and this is popularly regarded as a "shell", although it is not attached to the body of the animal and has a separate evolutionary origin.

The largest group of shelled cephalopods, the ammonites, are extinct, but their shells are very common as fossils.

The deposition of carbonate, leading to a mineralized shell, appears to be related to the acidity of the organic shell matrix (see Mollusc shell) shell-forming cephalopods have an acidic matrix, whereas the gladius of squid has a basic matrix. [78] The basic arrangement of the cephalopod outer wall is: an outer (spherulitic) prismatic layer, a laminar (nacreous) layer and an inner prismatic layer. The thickness of every layer depends on the taxa. [79] In modern cephalopods, the Ca carbonate is aragonite. As for other mollusc shells or coral skeletons, the smallest visible units are irregular rounded granules. [80]

Head appendages Edit

Cephalopods, as the name implies, have muscular appendages extending from their heads and surrounding their mouths. These are used in feeding, mobility, and even reproduction. In coleoids they number eight or ten. Decapods such as cuttlefish and squid have five pairs. The longer two, termed tentacles, are actively involved in capturing prey [1] : 225 they can lengthen rapidly (in as little as 15 milliseconds [1] : 225 ). In giant squid they may reach a length of 8 metres. They may terminate in a broadened, sucker-coated club. [1] : 225 The shorter four pairs are termed arms, and are involved in holding and manipulating the captured organism. [1] : 225 They too have suckers, on the side closest to the mouth these help to hold onto the prey. [1] : 226 Octopods only have four pairs of sucker-coated arms, as the name suggests, though developmental abnormalities can modify the number of arms expressed. [81]

The tentacle consists of a thick central nerve cord (which must be thick to allow each sucker to be controlled independently) [82] surrounded by circular and radial muscles. Because the volume of the tentacle remains constant, contracting the circular muscles decreases the radius and permits the rapid increase in length. Typically a 70% lengthening is achieved by decreasing the width by 23%. [1] : 227 The shorter arms lack this capability.

The size of the tentacle is related to the size of the buccal cavity larger, stronger tentacles can hold prey as small bites are taken from it with more numerous, smaller tentacles, prey is swallowed whole, so the mouth cavity must be larger. [83]

Externally shelled nautilids (Nautilus and Allonautilus) have on the order of 90 finger-like appendages, termed tentacles, which lack suckers but are sticky instead, and are partly retractable.

Feeding Edit

All living cephalopods have a two-part beak [8] : 7 most have a radula, although it is reduced in most octopus and absent altogether in Spirula. [8] : 7 [84] : 110 They feed by capturing prey with their tentacles, drawing it into their mouth and taking bites from it. [21] They have a mixture of toxic digestive juices, some of which are manufactured by symbiotic algae, which they eject from their salivary glands onto their captured prey held in their mouths. These juices separate the flesh of their prey from the bone or shell. [21] The salivary gland has a small tooth at its end which can be poked into an organism to digest it from within. [21]

The digestive gland itself is rather short. [21] It has four elements, with food passing through the crop, stomach and caecum before entering the intestine. Most digestion, as well as the absorption of nutrients, occurs in the digestive gland, sometimes called the liver. Nutrients and waste materials are exchanged between the gut and the digestive gland through a pair of connections linking the gland to the junction of the stomach and caecum. [21] Cells in the digestive gland directly release pigmented excretory chemicals into the lumen of the gut, which are then bound with mucus passed through the anus as long dark strings, ejected with the aid of exhaled water from the funnel. [21] Cephalopods tend to concentrate ingested heavy metals in their body tissue. [85] However, octopus arms use a family of cephalopod-specific chemotactile receptors (CRs) to be their "taste by touch" system. [86]

Radula Edit

The cephalopod radula consists of multiple symmetrical rows of up to nine teeth [87] – thirteen in fossil classes. [88] The organ is reduced or even vestigial in certain octopus species and is absent in Spirula. [88] The teeth may be homodont (i.e. similar in form across a row), heterodont (otherwise), or ctenodont (comb-like). [88] Their height, width and number of cusps is variable between species. [88] The pattern of teeth repeats, but each row may not be identical to the last in the octopus, for instance, the sequence repeats every five rows. [88] : 79

Cephalopod radulae are known from fossil deposits dating back to the Ordovician. [89] They are usually preserved within the cephalopod's body chamber, commonly in conjunction with the mandibles but this need not always be the case [90] many radulae are preserved in a range of settings in the Mason Creek. [91] Radulae are usually difficult to detect, even when they are preserved in fossils, as the rock must weather and crack in exactly the right fashion to expose them for instance, radulae have only been found in nine of the 43 ammonite genera, [92] [ clarification needed ] and they are rarer still in non-ammonoid forms: only three pre-Mesozoic species possess one. [89]

Excretory system Edit

Most cephalopods possess a single pair of large nephridia. Filtered nitrogenous waste is produced in the pericardial cavity of the branchial hearts, each of which is connected to a nephridium by a narrow canal. The canal delivers the excreta to a bladder-like renal sac, and also resorbs excess water from the filtrate. Several outgrowths of the lateral vena cava project into the renal sac, continuously inflating and deflating as the branchial hearts beat. This action helps to pump the secreted waste into the sacs, to be released into the mantle cavity through a pore. [93]

Nautilus, unusually, possesses four nephridia, none of which are connected to the pericardial cavities.

The incorporation of ammonia is important for shell formation in terrestrial molluscs and other non-molluscan lineages. [94] Because protein (i.e. flesh) is a major constituent of the cephalopod diet, large amounts of ammonium ions are produced as waste. The main organs involved with the release of this excess ammonium are the gills. [95] The rate of release is lowest in the shelled cephalopods Nautilus and Sepia as a result of their using nitrogen to fill their shells with gas to increase buoyancy. [95] Other cephalopods use ammonium in a similar way, storing the ions (as ammonium chloride) to reduce their overall density and increase buoyancy. [95]

Reproduction and life cycle Edit

Cephalopods are a diverse group of species, but share common life history traits, for example, they have a rapid growth rate and short life spans. [96] Stearns (1992) suggested that in order to produce the largest possible number of viable offspring, spawning events depend on the ecological environmental factors of the organism. The majority of cephalopods do not provide parental care to their offspring, except, for example, octopus, which helps this organism increase the survival rate of their offspring. [96] Marine species' life cycles are affected by various environmental conditions. [97] The development of a cephalopod embryo can be greatly affected by temperature, oxygen saturation, pollution, light intensity, and salinity. [96] These factors are important to the rate of embryonic development and the success of hatching of the embryos. Food availability also plays an important role in the reproductive cycle of cephalopods. A limitation of food influences the timing of spawning along with their function and growth. [97] Spawning time and spawning vary among marine species it's correlated with temperature, though cephalopods in shallow water spawn in cold months so that the offspring would hatch at warmer temperatures. Breeding can last from several days to a month. [96]

Sexual maturity Edit

Cephalopods that are sexually mature and of adult size begin spawning and reproducing. After the transfer of genetic material to the following generation, the adult cephalopods then die. [96] Sexual maturation in male and female cephalopods can be observed internally by the enlargement of gonads and accessory glands. [98] Mating would be a poor indicator of sexual maturation in females they can receive sperm when not fully reproductively mature and store them until they are ready to fertilize the eggs. [97] Males are more aggressive in their pre-mating competition when in the presence of immature females than when competing for a sexually mature female. [99] Most cephalopod males develop a hectocotylus, an arm tip which is capable of transferring their spermatozoa into the female mantel cavity. Though not all species use a hectocotylus for example, the adult nautilus releases a spadix. [100] An indication of sexual maturity of females is the development of brachial photophores to attract mates. [101]

Fertilization Edit

Cephalopods are not broadcast spawners. During the process of fertilization, the females use sperm provided by the male via external fertilization. Internal fertilization is seen only in octopuses. [98] The initiation of copulation begins when the male catches a female and wraps his arm around her, either in a "male to female neck" position or mouth to mouth position, depending on the species. The males then initiate the process of fertilization by contracting their mantle several times to release the spermatozoa. [102] Cephalopods often mate several times, which influences males to mate longer with females that have previously, nearly tripling the number of contractions of the mantle. [102] To ensure the fertilization of the eggs, female cephalopods release a sperm-attracting peptide through the gelatinous layers of the egg to direct the spermatozoa. Female cephalopods lay eggs in clutches each egg is composed of a protective coat to ensure the safety of the developing embryo when released into the water column. Reproductive strategies differ between cephalopod species. In giant Pacific octopus, large eggs are laid in a den it will often take several days to lay all of them. [98] Once the eggs are released and attached to a sheltered substrate, the females then die, [98] making them semelparous. In some species of cephalopods, egg clutches are anchored to substrates by a mucilaginous adhesive substance. These eggs are swelled with perivitelline fluid (PVF), a hypertonic fluid that prevents premature hatching. [103] Fertilized egg clusters are neutrally buoyant depending on the depth that they were laid, but can also be found in substrates such as sand, a matrix of corals, or seaweed. [97] Because these species do not provide parental care for their offspring, egg capsules can be injected with ink by the female in order to camouflage the embryos from predators. [97]

Male–male competition Edit

Most cephalopods engage in aggressive sex: a protein in the male capsule sheath stimulates this behavior. They also engage in male–male aggression, where larger males tend to win the interactions. [96] When a female is near, the males charge one another continuously and flail their arms. If neither male backs away, the arms extend to the back, exposing the mouth, followed by the biting of arm tips. [104] During mate competition males also participate in a technique called flushing. This technique is used by the second male attempting to mate with a female. Flushing removes spermatophores in the buccal cavity that was placed there by the first mate by forcing water into the cavity. [96] Another behavior that males engage in is sneaker mating or mimicry – smaller males adjust their behavior to that of a female in order to reduce aggression. By using this technique, they are able to fertilize the eggs while the larger male is distracted by a different male. [104] During this process, the sneaker males quickly insert drop-like sperm into the seminal receptacle. [105]

Mate choice Edit

Mate choice is seen in cuttlefish species, where females prefer some males over others, though characteristics of the preferred males are unknown. [96] A hypothesis states that females reject males by olfactory cues rather than visual cues. [96] Several cephalopod species are polyandrous- accepting and storing multiple male spermatophores, which has been identified by DNA fingerprinting. [102] Females are no longer receptive to mating attempts when holding their eggs in their arms. Females can store sperm in two places (1) the buccal cavity where recently mated males place their spermatophores, and (2) the internal sperm-storage receptacles where sperm packages from previous males are stored. [96] Spermatophore storage results in sperm competition which states that the female controls which mate fertilizes the eggs. In order to reduce this sort of competition, males develop agonistic behaviors like mate guarding and flushing. [96] The Hapalochlaena lunulata, or the blue-ringed octopus, readily mates with both males and females. [106]

Sexual dimorphism Edit

In a variety of marine organisms, it is seen that females are larger in size compared to the males in some closely related species. In some lineages, such as the blanket octopus, males become structurally smaller and smaller resembling a term, "dwarfism" dwarf males usually occurs at low densities. [107] The blanket octopus male is an example of sexual-evolutionary dwarfism females grow 10,000 to 40,000 times larger than the males and the sex ratio between males and females can be distinguished right after hatching of the eggs. [107]

Embryology Edit

Cephalopod eggs span a large range of sizes, from 1 to 30 mm in diameter. [108] The fertilised ovum initially divides to produce a disc of germinal cells at one pole, with the yolk remaining at the opposite pole. The germinal disc grows to envelop and eventually absorb the yolk, forming the embryo. The tentacles and arms first appear at the hind part of the body, where the foot would be in other molluscs, and only later migrate towards the head. [93] [109]

The funnel of cephalopods develops on the top of their head, whereas the mouth develops on the opposite surface. [110] : 86 The early embryological stages are reminiscent of ancestral gastropods and extant Monoplacophora. [109]

The shells develop from the ectoderm as an organic framework which is subsequently mineralized. [69] In Sepia, which has an internal shell, the ectoderm forms an invagination whose pore is sealed off before this organic framework is deposited. [69]

Development Edit

The length of time before hatching is highly variable smaller eggs in warmer waters are the fastest to hatch, and newborns can emerge after as little as a few days. Larger eggs in colder waters can develop for over a year before hatching. [108]

The process from spawning to hatching follows a similar trajectory in all species, the main variable being the amount of yolk available to the young and when it is absorbed by the embryo. [108]

Unlike most other molluscs, cephalopods do not have a morphologically distinct larval stage. Instead, the juveniles are known as paralarvae. They quickly learn how to hunt, using encounters with prey to refine their strategies. [108]

Growth in juveniles is usually allometric, whilst adult growth is isometric. [111]

The traditional view of cephalopod evolution holds that they evolved in the Late Cambrian from a monoplacophoran-like ancestor [112] with a curved, tapering shell, [113] which was closely related to the gastropods (snails). [114] The similarity of the early shelled cephalopod Plectronoceras to some gastropods was used in support of this view. The development of a siphuncle would have allowed the shells of these early forms to become gas-filled (thus buoyant) in order to support them and keep the shells upright while the animal crawled along the floor, and separated the true cephalopods from putative ancestors such as Knightoconus, which lacked a siphuncle. [114] Neutral or positive buoyancy (i.e. the ability to float) would have come later, followed by swimming in the Plectronocerida and eventually jet propulsion in more derived cephalopods. [115]

Possible early Cambrian remains have been found in the Avalon Peninsula, matching genetic data for a pre-Cambrian origin. [116]

However, some morphological evidence is difficult to reconcile with this view, and the redescription of Nectocaris pteryx, which did not have a shell and appeared to possess jet propulsion in the manner of "derived" cephalopods, complicated the question of the order in which cephalopod features developed – provided Nectocaris is a cephalopod at all. [117]

Early cephalopods were likely predators near the top of the food chain. [21] After the late Cambrian extinction led to the disappearance of many Anomalocaridids, predatory niches became available for other animals. [118] During the Ordovician period the primitive cephalopods underwent pulses of diversification [119] to become diverse and dominant in the Paleozoic and Mesozoic seas. [120]

In the Early Palaeozoic, their range was far more restricted than today they were mainly constrained to sublittoral regions of shallow shelves of the low latitudes, and usually occurred in association with thrombolites. [121] A more pelagic habit was gradually adopted as the Ordovician progressed. [121] Deep-water cephalopods, whilst rare, have been found in the Lower Ordovician – but only in high-latitude waters. [121] The mid-Ordovician saw the first cephalopods with septa strong enough to cope with the pressures associated with deeper water, and could inhabit depths greater than 100–200 m. [119] The direction of shell coiling would prove to be crucial to the future success of the lineages endogastric coiling would only permit large size to be attained with a straight shell, whereas exogastric coiling – initially rather rare – permitted the spirals familiar from the fossil record to develop, with their corresponding large size and diversity. [122] (Endogastric mean the shell is curved so as the ventral or lower side is longitudinally concave (belly in) exogastric means the shell is curved so as the ventral side is longitudinally convex (belly out) allowing the funnel to be pointed backward beneath the shell.) [122]

The ancestors of coleoids (including most modern cephalopods) and the ancestors of the modern nautilus, had diverged by the Floian Age of the Early Ordovician Period, over 470 million years ago. [121] [123] The Bactritida, a Silurian–Triassic group of orthocones, are widely held to be paraphyletic without the coleoids and ammonoids, that is, the latter groups arose from within the Bactritida. [124] : 393 An increase in the diversity of the coleoids and ammonoids is observed around the start of the Devonian period and corresponds with a profound increase in fish diversity. This could represent the origin of the two derived groups. [124]

Unlike most modern cephalopods, most ancient varieties had protective shells. These shells at first were conical but later developed into curved nautiloid shapes seen in modern nautilus species. Competitive pressure from fish is thought to have forced the shelled forms into deeper water, which provided an evolutionary pressure towards shell loss and gave rise to the modern coleoids, a change which led to greater metabolic costs associated with the loss of buoyancy, but which allowed them to recolonize shallow waters. [114] : 36 However, some of the straight-shelled nautiloids evolved into belemnites, out of which some evolved into squid and cuttlefish. [ verification needed ] The loss of the shell may also have resulted from evolutionary pressure to increase maneuverability, resulting in a more fish-like habit. [1] : 289

There has been debate on the embryological origin of cephalopod appendages. [125] Until the mid-twentieth century, the "Arms as Head" hypothesis was widely recognized. In this theory, the arms and tentacles of cephalopods look similar to the head appendages of gastropods, suggesting that they might be homologous structures. Cephalopod appendages surround the mouth, so logically they could be derived from embryonic head tissues. [126] However, the "Arms as Foot" hypothesis, proposed by Adolf Naef in 1928, has increasingly been favoured [125] for example, fate mapping of limb buds in the chambered nautilus indicates that limb buds originate from "foot" embryonic tissues. [127]

Genetics Edit

The sequencing of a full Cephalopod genome has remained challenging to researchers due to the length and repetition of their DNA. [128] The characteristics of Cephalopod genomes were initially hypothesized to be the result of entire genome duplications. Following the full sequencing of a California two-spot octopus, the genome showed similar patterns to other marine invertebrates with significant additions to the genome assumed to be unique to Cephalopods. No evidence of full genome duplication was found. [129]

Within the California two-spot octopus genome there are substantial replications of two gene families. Significantly, the expanded gene families were only previously known to exhibit replicative behaviour within vertebrates. [129] The first gene family was identified as the Protocadherins which are attributed to neuron development. Protocadherins function as cell adhesion molecules, essential for synaptic specificity. The mechanism for Protocadherin gene family replication in vertebrates is attributed to complex splicing, or cutting and pasting, from a locus. Following the sequencing of the California two-spot octopus, researchers found that the Prorocadherin gene family in Cephalopods has expanded in the genome due to tandem gene duplication. The different replication mechanisms for Protocadherin genes indicate an independent evolution of Protocadherin gene expansion in vertebrates and invertebrates. [129] Analysis of individual Cephalopod Protocadherin genes indicate independent evolution between species of Cephalopod. A species of shore squid Doryteuthis pealeii with expanded Protocadherin gene families differ significantly from those of the California two-spot octopus suggesting gene expansion did not occur before speciation within Cephalopods. Despite different mechanisms for gene expansion, the two-spot octopus Protocadherin genes were more similar to vertebrates than squid, suggesting a convergent evolution mechanism. The second gene family known as C2H2 are small proteins that function as zinc transcription factors. C2H2 are understood to moderate DNA, RNA and protein functions within the cell. [128]

The sequenced California two spot octopus genome also showed a significant presence of transposable elements as well as transposon expression. Although the role of transposable elements in marine vertebrates is still relatively unknown, significant expression of transposons in nervous system tissues have been observed. [130] In a study conducted on vertebrates, the expression of transposons during development in Drosophila melanogaster activated genomic diversity between neurons. [131] This diversity has been linked to increased memory and learning in mammals. The connection between transposons and increased neuron capability may provide insight into the observed intelligence, memory and function of Cephalopods. [130]

Phylogeny Edit

The approximate consensus of extant cephalopod phylogeny, after Strugnell et al. 2007, is shown in the cladogram. [75] Mineralized taxa are in bold. The attachment of the clade including Sepia and Spirula is unclear either of the points marked with an asterisk may represent the root of this clade.

Certain benthic squids (e.g. Bathyteuthoidea)

The internal phylogeny of the cephalopods is difficult to constrain many molecular techniques have been adopted, but the results produced are conflicting. [75] [132] Nautilus tends to be considered an outgroup, with Vampyroteuthis forming an outgroup to other squid however in one analysis the nautiloids, octopus and teuthids plot as a polytomy. [75] Some molecular phylogenies do not recover the mineralized coleoids (Spirula, Sepia, and Metasepia) as a clade however, others do recover this more parsimonious-seeming clade, with Spirula as a sister group to Sepia and Metasepia in a clade that had probably diverged before the end of the Triassic. [133] [134]

Molecular estimates for clade divergence vary. One 'statistically robust' estimate has Nautilus diverging from Octopus at 415 ± 24 million years ago . [135]

Taxonomy Edit

The classification presented here, for recent cephalopods, follows largely from Current Classification of Recent Cephalopoda (May 2001), for fossil cephalopods takes from Arkell et al. 1957, Teichert and Moore 1964, Teichert 1988, and others. The three subclasses are traditional, corresponding to the three orders of cephalopods recognized by Bather. [136]

Class Cephalopoda († indicates extinct groups)

  • Subclass Nautiloidea: Fundamental ectocochliate cephalopods that provided the source for the Ammonoidea and Coleoidea.
    • Order † Plectronocerida: the ancestral cephalopods from the Cambrian Period
    • Order † Ellesmerocerida ( 500 to 470 Ma )
    • Order † Endocerida ( 485 to 430 Ma )
    • Order † Actinocerida ( 480 to 312 Ma )
    • Order † Discosorida ( 482 to 392 Ma )
    • Order † Pseudorthocerida ( 432 to 272 Ma )
    • Order † Tarphycerida ( 485 to 386 Ma )
    • Order † Oncocerida ( 478.5 to 324 Ma )
    • Order Nautilida (extant 410.5 Ma to present)
    • Order † Orthocerida ( 482.5 to 211.5 Ma )
    • Order † Ascocerida ( 478 to 412 Ma )
    • Order † Bactritida ( 418.1 to 260.5 Ma )
    • Order † Goniatitida ( 388.5 to 252 Ma )
    • Order † Ceratitida ( 254 to 200 Ma )
    • Order † Ammonitida ( 215 to 66 Ma )
    • Cohort † Belemnoidea: Belemnites and kin
      • Genus † Jeletzkya
      • Order † Aulacocerida ( 265 to 183 Ma )
      • Order † Phragmoteuthida ( 189.6 to 183 Ma )
      • Order † Hematitida ( 339.4 to 318.1 Ma )
      • Order † Belemnitida ( 339.4 to 66 Ma )
      • Genus † Belemnoteuthis ( 189.6 to 183 Ma )
      • Superorder Decapodiformes (also known as Decabrachia or Decembranchiata)
        • Order Spirulida: Ram's horn squid
        • Order Sepiida: cuttlefish
        • Order Sepiolida: pygmy, bobtail and bottletail squid
        • Order Teuthida: squid
        • Family † Trachyteuthididae
        • Order Vampyromorphida: Vampire squid
        • Order Octopoda: octopus
        • Order † Boletzkyida

        Other classifications differ, primarily in how the various decapod orders are related, and whether they should be orders or families.

        Suprafamilial classification of the Treatise Edit

        This is the older classification that combines those found in parts K and L of the Treatise on Invertebrate Paleontology, which forms the basis for and is retained in large part by classifications that have come later.

        Nautiloids in general (Teichert and Moore, 1964) sequence as given.

        Subclass † Endoceratoidea. Not used by Flower, e.g. Flower and Kummel 1950, interjocerids included in the Endocerida. Order † Endocerida Order † Intejocerida Subclass † Actinoceratoidea Not used by Flower, ibid Order † Actinocerida Subclass Nautiloidea Nautiloidea in the restricted sense. Order † Ellesmerocerida Plectronocerida subsequently split off as separate order. Order † Orthocerida Includes orthocerids and pseudorthocerids Order † Ascocerida Order † Oncocerida Order † Discosorida Order † Tarphycerida Order † Barrandeocerida A polyphyletic group now included in the Tarphycerida Order Nautilida Subclass † Bactritoidea Order † Bactritida

        Paleozoic Ammonoidea (Miller, Furnish and Schindewolf, 1957)

        Mesozoic Ammonoidea (Arkel et al., 1957)

        Subsequent revisions include the establishment of three Upper Cambrian orders, the Plectronocerida, Protactinocerida, and Yanhecerida separation of the pseudorthocerids as the Pseudorthocerida, and elevating orthoceratid as the Subclass Orthoceratoidea.

        Shevyrev classification Edit

        Shevyrev (2005) suggested a division into eight subclasses, mostly comprising the more diverse and numerous fossil forms, [137] [138] although this classification has been criticized as arbitrary. [139]

        • Subclass † Ellesmeroceratoidea
          • Order † Plectronocerida ( 501 to 490 Ma )
          • Order † Protactinocerida
          • Order † Yanhecerida
          • Order † Ellesmerocerida ( 500 to 470 Ma )
          • Order † Endocerida ( 485 to 430 Ma )
          • Order † Intejocerida ( 485 to 480 Ma )
          • Order † Actinocerida ( 480 to 312 Ma )
          • Order † Basslerocerida ( 490 to 480 Ma )
          • Order † Tarphycerida ( 485 to 386 Ma )
          • Order † Lituitida ( 485 to 480 Ma )
          • Order † Discosorida ( 482 to 392 Ma )
          • Order † Oncocerida ( 478.5 to 324 Ma )
          • Order Nautilida (410.5 Ma-Rec)
          • Order † Orthocerida ( 482.5 to 211.5 Ma )
          • Order † Ascocerida ( 478 to 412 Ma )
          • Order † Dissidocerida ( 479 to 457.5 Ma )
          • Order † Bajkalocerida

          Cladistic classification Edit

          Another recent system divides all cephalopods into two clades. One includes nautilus and most fossil nautiloids. The other clade (Neocephalopoda or Angusteradulata) is closer to modern coleoids, and includes belemnoids, ammonoids, and many orthocerid families. There are also stem group cephalopods of the traditional Ellesmerocerida that belong to neither clade. [141] [142]

          The coleoids, despite some doubts, [1] : 289 appear from molecular data to be monophyletic. [143]

          Ancient seafaring people were aware of cephalopods, as evidenced by artworks such as a stone carving found in the archaeological recovery from Bronze Age Minoan Crete at Knossos (1900 – 1100 BC) has a depiction of a fisherman carrying an octopus. [144] The terrifyingly powerful Gorgon of Greek mythology may have been inspired by the octopus or squid, the octopus's body representing the severed head of Medusa, the beak as the protruding tongue and fangs, and its tentacles as the snakes. [145]

          The Kraken are legendary sea monsters of giant proportions said to dwell off the coasts of Norway and Greenland, usually portrayed in art as giant cephalopods attacking ships. Linnaeus included it in the first edition of his 1735 Systema Naturae. [146] [147] A Hawaiian creation myth says that the present cosmos is the last of a series which arose in stages from the ruins of the previous universe. In this account, the octopus is the lone survivor of the previous, alien universe. [148] The Akkorokamui is a gigantic tentacled monster from Ainu folklore. [149]

          A battle with an octopus plays a significant role in Victor Hugo's book Travailleurs de la mer (Toilers of the Sea), relating to his time in exile on Guernsey. [150] Ian Fleming's 1966 short story collection Octopussy and The Living Daylights, and the 1983 James Bond film were partly inspired by Hugo's book. [151]

          Japanese erotic art, shunga, includes ukiyo-e woodblock prints such as Katsushika Hokusai's 1814 print Tako to ama (The Dream of the Fisherman's Wife), in which an ama diver is sexually intertwined with a large and a small octopus. [152] [153] The print is a forerunner of tentacle erotica. [154] The biologist P. Z. Myers noted in his science blog, Pharyngula, that octopuses appear in "extraordinary" graphic illustrations involving women, tentacles, and bare breasts. [155] [156]

          Since it has numerous arms emanating from a common center, the octopus is often used as a symbol for a powerful and manipulative organization, usually negatively. [157]


          • Complete a minimum of 3 credits of ENY 4911 or ENY 4230
          • 2.0 UF GPA required
          • 2.0 upper division GPA required

          All entomology majors in this specialization must take three credits of ENY 4905 or ENY 4911 . See advisor for details.

          To remain on track, students must complete the appropriate critical-tracking courses, which appear in bold. These courses must be completed by the terms as listed above in the Critical Tracking criteria.

          This semester plan represents an example progression through the major. Actual courses and course order may be different depending on the student's academic record and scheduling availability of courses. Prerequisites still apply.


          The University of Kansas prohibits discrimination on the basis of race, color, ethnicity, religion, sex, national origin, age, ancestry, disability, status as a veteran, sexual orientation, marital status, parental status, gender identity, gender expression, and genetic information in the university's programs and activities. Retaliation is also prohibited by university policy. The following persons have been designated to handle inquiries regarding the nondiscrimination policies and are the Title IX coordinators for their respective campuses: Director of the Office of Institutional Opportunity & Access, [email protected], Room 1082, Dole Human Development Center, 1000 Sunnyside Avenue, Lawrence, KS 66045, 785-864-6414, 711 TTY (for the Lawrence, Edwards, Parsons, Yoder, and Topeka campuses) Director, Equal Opportunity Office, Mail Stop 7004, 4330 Shawnee Mission Parkway, Fairway, KS 66205, 913-588-8011, 711 TTY (for the Wichita, Salina, and Kansas City, Kansas medical center campuses).

          The University of Kansas is a public institution governed by the Kansas Board of Regents.


          BRANCH 3 PRE-OPERATORS COURSE

          Completion of this course will enable students to sit for the SPCB Branch 3 Operators Exam. After purchasing this course, a link will automatically be sent to your email and you can start immediately. The course is split up into 3 sections, all of which need to be completed before a certificate can be mailed out.

          Branch 3 topics covered include: Wood Destroying Organisms, termite Biology and Identification, Social Structure, Termite Species, The Role of IGRs in Termite Biology, Termite Characteristics, IGRs and Termite Biology, Termite Entry Points in Constructions, Tools, Considering Construction Elements During Inspection, Wood Treatment Techniques, Protecting People and Property During Structural Work, and Construction Knowledge and Techniques in Termite Work.

          Other important topics covered are: Federal Pesticide Laws, Toxicity of Pesticides, Ecological and Environmental Concerns, Safety Precautions with Pesticides, Personal Protection For The Applicator, Symptoms of Pesticide Poisoning, First Aid, Integrated Pest Management, Pests, Pesticide Resistance, The Label, Formulations, Calculations, Storage, Recordkeeping and Liability, Protecting Water, EPA Glossary of Pesticide Terms, Contract Law, Laws Pertaining to Corporation Type, Contract Negotiation, enforceability of Contracts, Contract Amendments, Basic Law Concepts, Lawsuits, Provisions, Administration, Performing Pesticide Work, Issuance of Licenses, Renewal of License, Regulation of Licensees, Disciplinary Proceedings, Revenue, Financial Responsibility, Continuing Education, General Law Information, Enforcement, Pesticide Handling, Use, and Storage, General concepts in Business Practices, Financing, Permits, Registering a Business, Compensation, Benefits, and Wages, Bankruptcy, Liability, and Subcontracting.

          This course has been designed in a Distance Learning format and approved by the California SPCB as a Pre-Operator course. NOTE: This course is online. All that is required is a strong internet connection and an email address. Quizzes are given at the end of each section to enhance the student’s learning. This course is narrated and self-paced, with high quality images of insect and animal species as well as equipment.


          Curriculum at Columbia

          For the 3+2 and 4+2 BA/BS programs, students complete the set of foundational courses required by Columbia plus courses specific to their intended major at Columbia. These are detailed in Columbia&rsquos Pre&ndashCombined Plan Curriculum Guides (see below). Equivalences between Bard and Columbia foundational and field-specific courses can be found below.

          Students applying for the 3+2 program must meet Bard&rsquos requirements. Students in the 4+2 program must complete all of Bard&rsquos graduation requirements in their four years at Bard and can apply up to one year after graduating.


          PROCEDURE

          Materials

          Proper personal protective equipment (PPE), including gloves, lab coats, and eye protection, is necessary for students performing this activity. In addition, each pair of students will require the following materials: two Mueller-Hinton agar plates, one nutrient (or tryptic soy) broth culture each of Bacillus cereus str. 971 and Escherichia coli str. K12, a bent-rod bacteria spreader (or two sterile swabs), a 1,000-μL micropipette and four sterile tips, two screw-cap centrifuge tubes (15 mL), two small beakers, two disposable sterile petri dishes, two Luer-Lok syringes (10 mL), two syringe membrane filters (sterile, 0.2𠄰.45 μm), four blank paper disks (sterile), two tetracycline disks, two penicillin disks, one mortar and pestle, one pair of forceps, one 10-mL graduated cylinder (or a 10-mL pipette with pipettor), one weighing spatula, two moringa seeds, one clove of fresh garlic, and 5 mL of 60ଌ water ( Fig. 1A ). If necessary, the students can share a tabletop microcentrifuge, ethanol, forceps, and a Bunsen burner. To save time, one half of the students can prepare the moringa extract, and the other half can prepare the garlic extract.

          Images of laboratory procedures. (A) Materials needed for the activity (B) Moringa seed with hull removed (C) Mortar and pestle grinding of moringa seed (D) Ground moringa seed slurry being poured into a 15-mL centrifuge tube (E) Slurry supernatant sterilized through a membrane filter (0.2𠄰.45 μm) (F) Sterile disks soaked in sterile extracts (G) Plating extract-soaked disks onto inoculated plates (H) Disk placement on plates of either E. coli (left) or B. cereus (right) (I) Zones of inhibition apparent on plates following 24-hour incubation (37ଌ).

          Student instructions

          Detailed student instructions to perform this activity are provided in Appendix 3. Briefly, the students worked together as a class to prepare filter-sterilized moringa and garlic extracts in water ( Fig. 1B𠄾 ). They then plated a “lawn” of each of the provided bacteria (one plate of E. coli and one plate of B. cereus) using either an ethanol-flamed bacteria spreader or sterile swabs. Ethanol-flamed forceps were then used to apply both extract-soaked and antibiotic-infused disks to each inoculated plate ( Fig. 1F–H ), and the plates were incubated for 24 hours at 37ଌ. After incubation, the students measured zones of growth inhibition around each disk ( Fig. 1I ) and completed a post-lab analysis, which included recording their data and answering the post-lab summary questions.

          Faculty instructions

          The instructor may obtain the moringa seeds from several possible sources. We obtained our seeds from www.echonet.org. Other vendors may be available via the Internet. Fresh garlic may be purchased from a local grocery store. Fresh (approximately 24-hour) bacterial cultures should be provided for the students to conduct this activity (see Appendix 4 for more details). All other materials are standard laboratory supplies.

          Present a pre-lab lecture to ensure the students are familiar with basic microbiological concepts (Appendix 4). If it has not already been covered in the course, the pre-lab lecture should include an introduction to artificial culture media and the use of proper growth conditions to cultivate bacteria. Students should also be made aware of the structural differences between gram-positive and gram-negative bacteria, as these often determine the efficacy of antibiotics that affect cell wall biosynthesis, such as penicillin, versus those that target other processes in the bacterial cell, such as tetracycline, an inhibitor of protein synthesis. In addition, students should be given basic background information regarding plants that produce antimicrobial compounds and the use of moringa and garlic as medicinal plants.

          The students should also be reminded of their training regarding the safety precautions for handling bacterial cultures, including their proper disposal, and an instructor demonstration of aseptic technique is recommended. As it is a potential source of injury, students should also be shown the correct technique for ethanol and flame sterilization of forceps and inoculating tools.

          Suggestions for determining student learning

          Before beginning the activity, the students were given an unannounced Pre-Lab Quiz ( Table 1 also see Appendices 1 and 2). The quiz was designed to assess the students’ existing knowledge of plants as a source of antibacterial products and how the activity of these products can be measured. After completing the activity and obtaining their results, the students were required to complete a post-lab analysis (Appendices 3 and 4), which included several summary questions to encourage critical thinking and assess student comprehension. The post-lab analysis, with its accompanying collection of data and answers to the summary questions, was due at the beginning of the next lab period. To gauge their retention of key concepts introduced the previous week, the students were then given the same Pre-Lab Quiz (unannounced and completed without the aid of notes) as a Post-Lab assessment.

          TABLE 1

          Pre- and post-lab activity quiz, including the learning objective to which each question corresponds.

          Question NumberQuiz QuestionCorresponding Learning Objective
          1Some plants have been shown to have medicinal value. How might you test a plant for production of antibacterial compounds?1
          2What are the requirements for growing bacteria in the laboratory, and what is the significance of aseptic technique in this process?2
          3What do clear zones around antimicrobial disks on a bacterial petri plate culture indicate?3
          4Bacteria are often categorized as either gram-positive or gram-negative. Why might an antibacterial compound inhibit the growth of gram-positive but not gram-negative bacteria?4
          5Why do some plants produce chemicals that have antimicrobial properties?5
          6How might humans make use of antimicrobial plant products to combat infectious disease?6

          Sample data

          Students measured zones of inhibition 24 hours after plating and incubation. They were able to see the effect of moringa and garlic extract and compare it with penicillin and tetracycline. Classroom results were generally uniform since all students shared the same extracts and tested the same strains of bacteria. Several observations were made, including the effects of penicillin and tetracycline on gram-positive versus gram-negative bacteria and the effects of garlic and moringa extracts on the two bacteria. The students could clearly see that tetracycline was more effective against both gram-positive and gram-negative bacteria than penicillin ( Fig. 2 ). Garlic was also effective against both types of bacteria, whereas moringa was more effective against gram-positive than gram-negative bacteria ( Fig. 2 ). Table 2 shows an example of quantitative data typical of that collected by the students.

          Measuring zones of inhibition after 24-hour incubation. Inhibition of bacterial growth was evaluated by measuring the diameter (mm) of each zone of inhibition. Comparisons of individual antibacterial agents can be made between the gram-negative E. coli (A) and the gram-positive B. cereus (B). Disks clockwise from top left: P, penicillin T, tetracycline G, garlic M, moringa.

          TABLE 2

          Example of typical data collected and reported by the students.

          Bacterial SpeciesZone of Inhibition (diameter, mm)
          Moringa Seed ExtractGarlic ExtractPenicillinTetracycline
          Bacillus cereus11156.512
          Escherichia coli7207.518

          Safety issues

          The bacterial strains used in this activity (E. coli strain K12 and B. cereus strain 971) are classified as BSL 1 organisms. (Note that several alternative bacterial strains or species may be suitable for use in this activity, but some of these are classified as BSL 2 organisms (see “Possible modifications” below) and, as such, must be handled accordingly in a properly equipped lab.) The students were trained in the safe handling of these microorganisms according to the ASM Biosafety Guidelines (https://www.asm.org/images/asm_biosafety_guidelines-FINAL.pdf) described by Emmert et al. (12). The students acknowledged their training by signing a safety agreement and adhered to standard laboratory safety procedures, which included disinfecting lab surfaces before and after completing the activity and using proper personal protective equipment (because of the potential splash hazard associated with the manipulation of plant extracts and liquid bacterial cultures, PPE should include eye protection). Contaminated pipet tips and swabs, and all bacterial cultures were disposed of by autoclave sterilization after use.

          Finally, for this activity, it is necessary for the students to sterilize laboratory utensils (e.g., forceps and bacteria spreader) by dipping in ethanol and flaming with a Bunsen burner. Ensure that student training includes how to properly carry out this procedure.


          Egg Osmosis Sample 2 lab

          Introduction:
          Transport can be either passive or active. Passive transport is the movement of substances across the membrane without any input of energy by the cell. Active transport is the movement of materials where a cell is required to expend energy. In the case of this lab the discussion will be centered on passive transport.
          The simplest type of passive transport is diffusion. Diffusion is the movement of molecules from an area of higher to an area of lower concentration without any energy input. Diffusion is driven by the kinetic energy found in the molecules. Diffusion will eventually cause the concentration of molecules to be the same throughout the space the molecules occupy, causing a state of equilibrium to exist.
          Another type of passive transport is that of osmosis. Osmosis is the movement of water across a semi-permeable membrane. The process by which osmosis occurs is when water molecules diffuse across a cell membrane from an area of higher concentration to an area of lower concentration. The direction of osmosis depends on the relative concentration of the solutes on the two sides. In osmosis, water can travel in three different ways.
          If the molecules outside the cell are lower than the concentration in the cytosol, the solution is said to be hypotonic to the cytosol, in this process, water diffuses into the cell until equilibrium is established. If the molecules outside the cell are higher than the concentration in the cytosol, the solution is said to be hypertonic to the cytosol, in this process, water diffuses out of the cell until equilibrium exists. If the molecules outside and inside the cell are equal, the solution is said to be isotonic to the cytosol, in this process, water diffuses into and out of the cell at equal rates, causing no net movement of water.
          In osmosis the cell is selectively permeable, meaning that it only allows certain substances to be transferred into and out of the cell. In osmosis, the proteins only on the surface are called peripheral proteins, which form carbohydrate chains whose purpose is used like antennae for communication. Embedded in the peripheral proteins are integral proteins that can either be solid or have a pore called channel proteins. Channel proteins allow glucose, or food that all living things need to live, pass through.

          Hypothesis:
          In the syrup solution, there will be a net movement of molecules out of the egg, and in the water solution, the molecules will diffuse in and out of the cell at equal rates.

          Materials:
          The materials used in this lab were 2 fresh eggs in the shell, an overhead marker, 400 ml of water, graduated cylinder, 1 large beaker, 2 medium beakers, 1 small beaker, white vinegar, Karo syrup, distilled water, pencil, paper, lab apron, lab goggles, saran wrap, masking tape, plastic tray, tongs, electronic balance, osmosis lab sheet, and computer.

          Methods:
          On day 1, measure the masses of both the eggs with the shell. Label 1 beaker vinegar, and then use the graduated cylinder to measure 400 mL of vinegar to put in the labeled beaker. Place both eggs in the solution (place a small beaker on top of the eggs, if necessary) then cover. Let the eggs stand for 24 hours or more to remove the shell.

          On day 2, record the observations of what happened to the eggs in the vinegar solution. Carefully, remove the eggs from the vinegar, gently rinsing the eggs off in water. Clean the beakers used for the vinegar solution preparing them for the syrup solution, and then label the 2 medium beakers syrup. Before the eggs are placed in the syrup solution record the mass of both eggs then put it on the datasheet. After that has been done, place the eggs in the beaker, pouring enough syrup to cover the eggs, cover them loosely and let them stand for 24 hours.

          On day 3, record the observations of the egg from the syrup solution. Carefully, remove the eggs from the beakers, gently rinsing the syrup off of the eggs. Pour the remaining syrup in the container provided by the teacher. Clean the two beakers used in the syrup solution, preparing them for the water solution. Before the eggs are placed in the water solution record the mass of both eggs then put it on the datasheet. After that has been done, using a graduated cylinder, measure out 200 mL of water for each beaker. Place the eggs in the water solution, cover and let stand 24 hours.

          On day 4, record the observations of the egg from the water solution. Carefully remove the eggs from the beakers, gently rinsing them off. Mass both of the eggs. After the teacher has came and looked at the eggs, discard in the proper place.


          3.3.4 Mass transport

          Over large distances, efficient movement of substance to and from exchange surfaces is provided by mass transport.

          3.3.4.1 Mass transport in animals

          The haemoglobins are a group of chemically similar molecules found in many different organisms. Haemoglobin is a protein with a quaternary structure.

          The role of haemoglobin and red blood cells in the transport of oxygen. The loading, transport and unloading of oxygen in relation to the oxyhaemoglobin dissociation curve. The cooperative nature of oxygen binding to show that the change in shape of haemoglobin caused by binding of the first oxygens makes the binding of further oxygens easier. The effects of carbon dioxide concentration on the dissociation of oxyhaemoglobin (the Bohr effect).

          Many animals are adapted to their environment by possessing different types of haemoglobin with different oxygen transport properties.

          The general pattern of blood circulation in a mammal. Names are required only of the coronary arteries and of the blood vessels entering and leaving the heart, lungs and kidneys.

          The gross structure of the human heart. Pressure and volume changes and associated valve movements during the cardiac cycle that maintain a unidirectional flow of blood.

          The structure of arteries, arterioles and veins in relation to their function.

          The structure of capillaries and the importance of capillary beds as exchange surfaces. The formation of tissue fluid and its return to the circulatory system.

          Students should be able to:

          • analyse and interpret data relating to pressure and volume changes during the cardiac cycle
          • analyse and interpret data associated with specific risk factors and the incidence of cardiovascular disease
          • evaluate conflicting evidence associated with risk factors affecting cardiovascular disease
          • recognise correlations and causal relationships.

          Students could design and carry out an investigation into the effect of a named variable on human pulse rate or on the heart rate of an invertebrate, such as Daphnia.

          Students could be given values of cardiac output (CO) and one other measure, requiring them to change the subject of the equation:

          Required practical 5: Dissection of animal or plant gas exchange system or mass transport system or of organ within such a system.

          3.3.4.2 Mass transport in plants

          Xylem as the tissue that transports water in the stem and leaves of plants. The cohesion-tension theory of water transport in the xylem.

          Phloem as the tissue that transports organic substances in plants. The mass flow hypothesis for the mechanism of translocation in plants. The use of tracers and ringing experiments to investigate transport in plants.

          Students should be able to:

          • recognise correlations and causal relationships
          • interpret evidence from tracer and ringing experiments and to evaluate the evidence for and against the mass flow hypothesis.

          Students could set up and use a potometer to investigate the effect of a named environmental variable on the rate of transpiration.


          Watch the video: EMBRYONIC DEVELOPMENT IN INSECTS (October 2022).