Definition that uniquely defines animals as different from all other organisms
Animal refers multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Some features that differentiate are such as, they are eukaryotic and multicellular, hence different from bacteria and most protists. Secondly, they are heterotrophic, usually digesting food in an internal chamber hence different from plants and algae. They also lack cell walls are motile. All animals have eukaryotic cells, surrounded by a characteristic extracellular matrix composed of collagen and elastic glycoproteins. This may be calcified to form structures like shells, bones. In contrast, other multicellular organisms, like plants and fungi, have cells held in place by cell walls, and so develop by progressive growth. ( Brian et al, 2008).
a comparison of the sponge spongocoel and the cnidarian gastrovascular cavity
Sponge lack definite digestive system and depend on the intracellular digestive processes of their choanocytes for nutrient. They are filter feeders that acquire plankton from the water that pass through pores lined with collar cells. Flagella haul in bacteria, protozoans, & algae that attachess to collar of choanocytes where it is digested. They posses Amebocytes , specialized cells in sponges with ability to roam and collect food from choanocytes & allocate to other parts of the sponge. Amebocytes also conduct waste product of digestion through the excurrent osculum(Barrington & James 1979).
Cnidarians have two layers of tissue. The outer layer, epidermis and inner gastrodermis, lines the digestive cavity. The two layers have non-living, jelly-like mesoglea between them. There are distinguished cell types in each tissue layer, such as nerve cells, enzyme-secreting cells, and nutrient-absorbing cells, as well as intercellular connections between the cells. (Barrington & James 1979)
comparison of the body walls of sponges and anemones with a description of cell types and their functions
Bodies of sponge are full of pores and channels enabling water to circulate through them. They have of jelly-like mesohyl covered between two thin layers of cells. Sponges consist of unspecialized cells with ability to transform into other types then migrate between the main cell layers and the mesohyl in the process. Sponge’s body is aligned in a mesohyl, which is a gelatinous matrix. The mesohyl is reinforcedt by the sponge’s skeleton and composed of canals that run through the sponge’s body. Water passes through these canals and the sponge filters out food for survival. Some of the cells include Coenocytic cells consisting of a collar of fine fibrils that strain the least food particles from the water. The epidermis is made up of Pinacocyte cells. Myoocyte and porocyte cells enclose canal openings and regulate water flow. Archaeocytes help in digestion.
Anemones have a well developed contractile and thicker mesoglea, which often makes a fibrous connective tissue. Corals produce a hard, limy skeleton and can form huge reefs.The body wall of a anemones consists of three layers, an outer layer known as the epidermis, a middle layer called the mesoglea, and an inner layer referred to as the gastrodermis. (Anderson &Donald 1996)The epidermis has a collection of cells such as epitheliomuscular cells that contract and allow movement, interstitial cells that produce various cell types such as egg and sperm, cnidocytes. anemones contain stinging structures, mucus-secreting cells which glandular cells that secrete mucus, and receptor and nerve cells which collect and transmit sensory information(Anderson &Donald 1996).
QUESTION TWO
Moon Jelly (Aurelia aurita)
life cycle of Aurelia aurita consist of two major satges,the polyp stage (asexual reproduction) and the medusa stage (sexual reproduction). Mature polyps replicate asexually, through budding making a complete colony of polyps. Polyps focusing in replication produce ephyra by budding. The medusae swim away and mature after which they sexually reproduce. From the egg and the sperm of two medusae, a zygote is formed. The zygote grows into a planula or larva ( Moen & Svensen, 2004). The planula larvas departs from the adult medusa to a shaded surface and sticks. It finally develops into a new polyp, and the life cycle of the Aurelia aurita repeats The eggs develop in gonads located in pockets formed by the frills of the oral arms. The gonads lie at the bottom of the stomach. Males and females are distinct and reproduction is sexual. ( Moen & Svensen, 2004). Aurelia aurita is adapted in that The sexes are separate and fertilization is internal.
Diphyllobothrium latum
Mature organisms are hermaphroditic and capable of self- fertilization while some develop a second set of reproductive organs. From the host, eggs hatch after 9 to 120 days. The coracidium depart the egg through the operculum, a cap in the egg.The coracidium is ciliated and moves in water, where it is ingested by a copepod. The coracidium then sheds its ciliated epithelium, penetrates the midgut wall of the copepod, and develops into the infective procercoid after 18 days(Brusca, 2003).The copepod is the 1st intermediate host.The procercoid cause the copepod to be sluggish, making it susceptible to be ingested by a 2nd intermediate host, often a frog, snake, or mammal.The procercoid penetrates the gut wall and enters the muscles or connective tissues. The procercoid then develops into the plerocercoid.The 2nd intermediate host is then eaten by either the definitive host (the bobcat) or a secondary definitive host (a dog or cat). The adult penetrates the intestinal wall and enters the muscles, where it absorbs nutrients. The life cycle continues to a first intermediate host (copepod) and second intermediate host (fish). (Brusca, 2003). The organism is adapted by laying a lot of eggs to increase chances of reproduction
Fasciola hepatica
Life cycle begins when eggs are passed out of the liver with bile and into the intestine and disposed as waste. When in contact with water, eggs accomplish development into miracidia and hatch after which it finds an appropriate snail host. sporocysts then produce first generation rediae, which eventually produce daughter rediae that grow in snail’s digestive gland. From the snail, minute cercariae arise and swim in water and encyst as metacercariae. The metacercariae are ingested by the ruminant. Contact with low pH in the stomach causes the early immature juvenile to begin the process of excystment. In the duodenum, the parasite breaks free of the metacercariae and burrows through the intestinal lining into the peritoneal cavity. The newly excysted juvenile does not feed at this stage, but once it finds the liver parenchyma after a period of days, feeding will start. The parasite is able to grow into a variety of hosts hence increasing its chance of existance
Advantages of sexual over assexual
Asexual reproduction is advantageous for organisms that are not motile and unable to look for mates. Nevertheless, it does not lead to variation between organisms may not survive in alteration of stable environment. Sexual reproduction enables variation, the most significant elements of evolution. It therefore makes species that can acclimatize to new environments Nonetheless; sexual reproduction needs significant energy on the part of the organism to find a mate
QUESTION THREE
Describe each of the advances of annelids over flatworms by comparing the Tiger Planaria (Dugesia tigrina), and the Iridescent Phyllodoce (Phyllodoce multipapillata).
Phyllodoce multipapillata have made some advances that take them beyond the simple body plan of the average Tiger Planaria. One important difference is segmentation .Phyllodoce multipapillata unlike Tiger Planaria are segmented and have a very complex and organized organ system. Phyllodoce multipapillata have a head, followed by body segments and a tail. Each segment has its own muscles, nerves and excretory organs, and each segment is independent and yet part of the whole. (Gullan & Cranston, 2005). This is the beginnings of specialisation, where different body segments can have different functions. They posses a reproduction system, and a digestive system as well as a circulatory system. Tiger Planaria are not segmented and have simple and unorganized reproduction system only.
Tiger Planaria do not have a body cavity and therefore the three cell layers are not separated. They have a two way gut in which food enters the gut and waste products leave through same opening because the gut has a dead end and there is no anus. Phyllodoce multipapillata, however, have a body cavity and are round instead of flat. They also have one way gut with a mouth at one end and an anus at the other(Gullan & Cranston, 2005).
Phyllodoce multipapillata have a true coelom, which is formed entirely within the mesoderm on the other hand Tiger Planaria have no body cavity hence do not have a coelom.An important evolutionary advance, in Phyllodoce multipapillata is that their body muscles are made quite separately with their ‘ true’ coelom. Phyllodoce multipapillata movements of the gut (peristalsis) are quite separate from the movements of muscles that propel the body across or through the substrate. In contrast, Mesodermal tissue forming the muscles are joined to the endoderm forming gut in Tiger Planaria hence, they cannot move their muscles separately to their gut (Hutchings, 2007).
QUESTION FOUR
Description of compound eye structure, how the image is processed by the eye and brain and how color vision is accomplished.
A compound eye consists of thousands of individual photoreceptor units or ommatidia. The image perceived is a combination of inputs from the numerous ommatidia, which are located on a convex surface, thus pointing in slightly different directions. The pigment cells ensure that only light entering the ommatidium parallel to its long axis reaches the visual cells and triggers nerve impulses. Thus each ommatidium is pointed at just a single area in space and contributes information about only one small area in the field of view. Color vision requires two or more pigments, each of which absorbs best at a different wavelength. For example ultraviolet vision involves using a special ultraviolet-transmitting lens that navigates ultraviolet light from the sun (Adiyodi, 2002).
The differences between the eyes of nocturnal and diurnal insects
Nocturnal insects have typically much larger eyes that work to gather any night time light in a more effective manner. Some nocturnal insects also have a tapetum, a special reflective layer in the eye that aids their night vision which is absent in diurnal insects. Higher concentrations of rod cells in the retinas of nocturnal insects than diurnal ones help them to form a visual image even in low light levels. Although the image is not as clear as it when seen through a retina made with cone cells, it still allows nocturnal insects the ability to use their vision skillfully at night.
Diurnal insects have a compound eye in which light entering reaches the retina of each ommatidium as a single spot and the image is a composite of all the spots
A description of gradual metamorphosis and complete metamorphosis and the advantages of complete metamorphosis over gradual metamorphosis.
Gradual metamorphosis is where three life stages occur that is egg, nymph, and adult. On the other hand, the complete metamorphosis is where four separate stages of growth, as embryo, larva, pupa, and imago (Eernisse,1992).
Advantages
In holometabolous insects, larvae and adults don’t compete for food source, consequently, there is a form of specialization in growing (Larvae) and reproduction (Adult) separately. Larvae and adult live in different habitat. On the contrary in gradual metamorphosis, shares the same habitat and food as the adults, and show similar behaviors and a lot of competition exist hence reduced chances for survival.
description of the structure, function and advantages of the exoskeleton and wings
Microscopically, the exoskeleton has numerous layers. The inner layer, epidermis, secretes a supportive fiber membrane. Above the epidermis there is procuticle layer of of chitin surrounded by a matrix of protein. It layer solidifies to make the rigid plates of the exoskeleton. The outermost layer is epicuticle which prevents the soft tissue of the arthropod from drying out and protection. While the wings aid in motility the exoskeleton anchor muscles sense stimuli.
QUESTION FIVE
The nature and production of the shells of abalone
The low open spiral structured shells have holes that are used in the respiration, sanitation, and reproduction of the abalone. The shell has a thick inner layer composed of nacre which is highly iridescent, giving rise to a range of strong changeable colors. It is made of microscopic calcium carbonate tiles stacked like bricks. Between the layers of tiles is a clingy protein substance.
Feeding mechanisms of a gastropod (such as a sea hare), a bivalve (such as a clam), and a cephalopod (such as a squid).
Some marine gastropods are herbivores, detritus feeders, predatory carnivores, scavengers, parasites, while others are also ciliary feeders. Land-dwelling species can chew up leaves, bark, fruit and decomposing animals while marine species can scrape algae off the rocks on the sea floor. Some species have evolved into endoparasites for example eulimid Thyonicola doglieli. A few sea slugs are herbivores and some are carnivores.
Cephalopod feed by capturing prey with their tentacles, drawing it into their mouth and taking bites from it. 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 mouth. These juices separate the flesh of their prey from the bone or shell. The salivary gland has a small tooth at its end which can be poked into an organism to digest it from within(Allen, 2006).
The bivalves can filter-feed fine particles form the water. Based on the mechanism of food collection, bivalves can be suspension–feeders or deposit–feeders, or even utilize both feeding methods. Some bivalves’ species have ability to regulate filtration and select particles based on their size, shape, nutritive value or chemical component on the surface of the particle. The food source for bivalves include phytoplankton, bacteria, detritus and even zooplankton.
Mechanisms that control buoyancy in Sepia, Nautilus, Loligo and Octopus
Nautilus, allow gas to diffuse into the gap between the mantle and the shell; others like Sepia allow purer water to ooze from their kidneys, forcing out denser salt water from the body cavity while others, like Loligo, accumulate oils in the liver. Some octopuses have a gelatinous body with lighter chlorine ions replacing sulfate in the body chemistry.
Mechanisms of color production and color change in squid
Squids have special pigment cells called chromatophores in their skin that are connected to the nervous system hence their size is determined by muscular contractions. By controlling the size of the cells they vary their color and even create changing patterns. Most of the squid can biologically produce a light called bioluminescence and control its intensity by photophores within their skin.
Reference
Adiyodi, K. G(2002). Reproductive Biology of Invertebrates, Progress in Asexual Reproduction, Volume 11. Wiley. p. 116.
Allen,T G. (2006). Ecology of marine fishes: California and adjacent waters. University of California Press.
Anderson, Donald Thomas(1996).. Atlas of Invertebrate Anatomy. Sydney, Australia: UNSW Press,
Barrington, Ernest James William(1979). Invertebrate Structure and Function. New York: Wiley
Brusca, R., G. Brusca. 2003. Invertebrates. Sunderland, Massachusetts: Sinauer Associates, Inc.
Eernisse, D. (1992). “Annelida and Arthropoda are not sister taxa: A phylogenetic analysis of spiralean metazoan morphology”. Systematic Biology 41 (3): 305–330.
Gullan P.J. & Cranston P.S. 2005. Life history patterns and phases in the insects. In An outline of entomology. Blackwell, Oxford.
Hall et al (2008). Strickberger’s evolution: the integration of genes, organisms and populations. Jones & Bartlett Learning.
Hutchings, P. (2007). “Book Review: Reproductive Biology and Phylogeny of Annelida”. Integrative and Comparative Biology 47 (5): 788
Moen, F.E. and E. Svensen. 2004. Marine fish & invertebrates of Northern Europe. AquaPress: Southend-on-Sea.
