zoology biology lab 6 PDF

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Laboratory 6 Assignment Note, all questions may not be marked Type your answers in blue font.

Assignment 1: Onychophora

1. Using an image of a cross-section slide from the lab, identify each of the following structures: midgut, heart, longitudinal muscles, slime glands and the foot.

2. At one time Onychophorans were considered the link between the phylum Annelida and phylum Arthropoda. Identify two characteristics shared by members of the phylum Onychophora and members of the phylum Annelida. Be specific- saying that they have a nervous system is not an acceptable answer. - onychophorans similar to annelida in that they have a segmented body with excretory organs/nephridia. - - - Another similarity is that they both have similar structures, they both lack exoskeletons and have chitinous cuticles instead. 3. Identify at least four characteristics that the phylum Onychophora share with members of the phylum Arthropoda? - Both use an antennae as a sensory system. - Both also have a tubular heart structure to be used in their open circulatory system . - Both have paired jaws for breaking up food for mechanical digestion - both have a narrow trachea used in oxygen respiration.

4. What is cryptobiosis? How does cryptobiosis in tardigrades increase the likelihood of survival? - Cryptobiosis is the ability to enter a state in which metabolism virtually halts to preserve energy. - in unfavorable conditions, a tardigrade can enter cryptobiosis to preserve energy and wait until the environment becomes favorable. - Thus, less likely to be die from the environment or lack of food.

5. What is the difference between metamerism and tagmatization? - Metamerism is the segmentation or construction of repeating parts in an organism in a linear series - each segment being called a metamere. - Tagmatization is the specialized grouping of segments to form functional morphological units such as, head, thorax, and tail. Assignment 3

6. Label each of the following structures on the diagram below: basement membranes, exocuticle, endocuticle, epicuticle, and the epidermis.

Epicuticle Exocuticle Endocuticle

Epidermis

Basement Membrane

7. Briefly outline the steps involved in ecdysis. Point form is acceptable.         

Occurs 4-7 times throughout life Inorganic salts withdrawn from old cuticle Old procuticle separates from epidermis Epidermis secretes exocuticle Molting fluid dissolve old cuticle the exocuticle and epicuticle remain from old cuticle These are then removed by the organisms swallowing large volume of water This water increases internal pressure and split cuticle The new soft cuticle stretches and hardens when inorganic salts are deposited during post-molt

Assignment 4

8. Why did trilobites go extinct? - theories support climate change and sea-level fluctuation as a cause to the extinction - this could have occurred as these animals could not adapt to become the most favourable in the environment. - Other theories suggest a sudden increase in Trilobite predators in the form of fish and squid.

Assignment 5 9. Class Merostomata and Class Arachnida inhabit very different environments, identify these habitats, and then discuss at least two ways each of these specimens has adapted for its particular habitat. Again, it is important to be specific- identify specific challenges for each of the environments and then identify specific structures. - Merostomata inhabit saline areas of coastal waters (ex. Bays, wetlands). - Arachnida inhabit a wide range of terrestrial land areas. - Arachnids have developed 8 appendages to aid feeding, defense and sensory functions. - arachnids have a book lung for oxygen exchange with the air (terrestrial creatures) - Merostomata have a book gill for oxygen exchange with water (aquatic creatures) - Merostomata also have a strong exoskeleton which evolved for defense against predators. - The exoskeleton covers the top of their bodies since they tend to dwell on the bottom of the water 10. Most arachnids are harmless to humans and actually do much good. Do you agree or disagree with this statement? In no more than 200 words, defend your position. I agree with this statement as Arachnids are allies to humans and work symbiotically in some senses. They assist to control the population of household pests. Examples include organisms such as grasshopper, aphids, and mosquitoes. By controlling these population, we can ensure infestation does not occur and reducing the need and use of pesticides in our environment.

Assignment 6 11. Identify the tick on display in slide 21. Adult male American dog tick or Dermacentor variabilis 12. Which species of tick is a vector for Lyme disease? How does this species differ from the tick on display? The Species which is a vector for Lyme disease is Ixodes scapularis. This species differs from the Dermacentor variabilis as it possesses no light-coloured markings which has a much smaller body. The Ixodes scapularis also has a large adult female compared to the male, whereas the other species is very similar in size. Assignment 7 13. From your observations in the lab, list two differences between class Diplopoda and class Chilopoda. - Diplopoda have 2 pairs of legs per body segment while the Chilopoda only have 1 pair of legs per segment. - Chilopoda possess very long/large legs in comparison to their body size while the Diplopoda possess very small/short legs in comparison to their body size 14. During a sunny vacation abroad, you put your foot into your shoe and feel something within. Would you prefer it to be from class Chilopoda or class Diplopoda? Why? - I prefer it to be from the class Diplopoda. This is because these organisms are not known to bite humans like the Chilopoda. - In addition the Diplopoda instead impose a defensive mechanism of curling into a ball. 15. Describe a typical insect's tracheal system and explain why it can function efficiently without oxygen-carrying pigments in the hemolymph. Why would a tracheal system not be suitable for humans?

The typical tracheal system of an insect consists of spiracles located on the body surface that act as channels to bring air in and out of the body. This air is then transported into a trachea, which branches out perpendicular to the body length. These branches continue to get smaller and branch out to all the internal organs and muscles. Therefore, air enters at multiple points of the body. This system would not be suitable for a human as this system does not allow sufficient air temperature regulation and moisture control to increase diffusion rates. Also, humans do not contain a hard outer layer of the body, thus making it less favourable to support spiracle structures. The size of humans may also be difficult as our volume to surface area ratio is much greater than most insects, meaning we have more internal structures requiring oxygen, and less skin space to hold spiracles. 16. The tracheal system is an adaptation for air-breathing, but many insects (nymphs, larvae and adults) live in water. How do these animals exchange gases? A lot of water dwelling insect will possess either external gills or superficial gills that produce the gas diffusion exchange, and then transport these gases throughout their narrow tracheal system to deliver to internal structures. 17. Assignment 8 Examine the model of the insect on slide 26. Identified the labelled structures and list their functions. Letter A B C

Structure Esophagus Crop Gastric Seca

D E

Heart Brain

F G H I

Exoskeleton Colon Ovary Salivary Gland Midgut

j

Function Transports food from the mouth to the crop Stores food before releasing to the midgut Act to increase surface area to aid in enzyme secretion and nutrient absorption Pumps blood fluid throughout the body to supply tissues with oxygen Controls movement, regulates homeostasis, processes sensory information. Protects the organism’s organs and internal structures Final absorption of nutrients and then excretes waste through the anus Production of egg cells Creates saliva and releases into the mouth Metabolizes food, absorbs nutrients and releases left over food into the colon

18. Arthropods represent the cumulation of evolutionary development in the protostomes. From your observations in the lab today, identify at least four characteristics that contribute to their success. Briefly explain the advantage conferred by each of these characteristics. One advantage for Arthopods is their very high rate of reproduction. - characteristic allows for the best chance of species survival as a high rate of reproduction - allows for both increased genetic diversifications along with increased number of offspring to carry on the genes. - This phylum also has highly developed sensory organs that can allow for increased detection of food along with increased awareness of predators increasing chance of survival. - Metamorphosis in some Arthopods can allow for increased survival for early lifestyle. - An example of this is the mosquito that begins its life in the water and can be protected from prey while it develops into its adult life.

- Tagmatization allows for the advantage of organized exoskeleton developed as “plates” over segmented sections of the body. - These exoskeleton “plates” allows for protection along with allowing movement around the joint sections of tagmatization. 19. Within the arthropods, the insects are the most successful and speciose group. Discuss the insects' formula for success. Use essay format and include specific examples. (400 words max) It is certainly no accident that insects are the most abundant and most diverse group of organisms on earth. They have maintained a position of ecological pre-eminence for over 400 million years. Some attributes which lead to their success lie in their exoskeleton, locomotion, reproductive potential, metamorphosis. First, unlike vertebrates, an insect's supporting skeleton is located on the outside of its body. This exoskeleton is a marvelous structure that not only gives shape and support to the body's soft tissues, but also provides protection from attack or injury, minimizes the loss of body fluids in both arid and freshwater environments, and assures mechanical advantage to muscles for strength and agility in movement. Secondly, flight gave these insects a highly effective mode of escape from predators that roamed the prehistoric landscape. It was also an efficient means of transportation, allowing populations to expand more quickly into new habitats and exploit new resources. In addition, more than 200 species, including moths, dragonflies, locusts, flies, and beetles are known to migrate over long distances by air. Third, Reproductive success is one of the most significant measures of an organism's fitness. In insect populations, females often produce large numbers of eggs (high fecundity), most of the eggs hatch (high fertility), and the life cycle is relatively short (often as little as 2-4 weeks). Together, these three characteristics enable insects to produce remarkably large numbers of offspring. A typical female lays 100-500 eggs in her lifetime, but numbers in the thousands are not uncommon. The queen of an African termite colony may be the mother of more than ten million workers during her 20–25-year lifespan. Fourth, most insects undergo significant developmental changes as they grow from immatures to adults called metamorphosis. These changes, collectively known as metamorphosis, may involve physical, biochemical, and/or behavioral alterations that promote survival, dispersal, and reproduction of the species.

20. What is meant by homologous structures? What is meant by serial homology, and how do crustaceans show serial homology? - Homologous structures are characterized by different species containing the same or very similar structures that have similar function and/or position within the body. - Serial homology is characterized as repetitive structure within an organism that have the same basic structure but are not necessarily restricted to one specific function. - an example can be seen between the Crayfish has 19 pairs of appendages that all have very similar repeating structures, but can be specialized in function (e.g., walking, feeding, mating, swimming). 21. Identify each of the structures on the model of the crayfish on slide 47. A: Antennal Gland B: Pyloric Stomach C: Testes D: Heart E: Ventral Thoracic Artery

22. Identify each of the structures indicated on the crab in slide 48. A: Heart B: Gills C: Middle Vas Deferens D: Gastric Muscles

23. Describe respiration and circulation in the crayfish or the crab. - crabs breathe underwater by drawing water over their gills using an appendage called a scaphognathite located on the crab’s underside. - Water then passes over the gills which are within their own specialized chamber. - water leaves the crab through the mouth region. - When a crab goes onto land, their gill chamber can maintain moisture by using articulating plates to seal the gill chamber keeping the gills wet. - Often crabs will find shaded or damp places on land to further enhance or extend their moisture within the gill chamber. - Some crabs can draw in water from dew or other moist objects, while others “blow bubbles” as they draw in air over the moistened gills, producing bubbles....