Highschool Biology Questions - Assignment Example

Order# 337492 Word count: 3081 words Topic: High school Biology Questions The theme of Reproduction is clearly illustrated by the fact thatbees pollinate the flowers from which they collect nectar. The pollen grains germinate down the style to the ovary resulting in double fertilization (Roberts 370). The use of nectar by bees for nourishment underscores the importance of the theme of Metabolism which enables bees to oxidize the ingested food to yield energy necessary for growth and repair of tissues (Roberts). The bees use the theme of Homeostasis by relentlessly keeping their hives at acceptable state for their larvae to develop (p 206). The theme of Evolution is responsible for the presence of the diverse range of species present on earth. It is further propagated through the processes of adaptation and breeding as cited by Roberts. Bees are naturally interdependent on other aspects of the environment, both biotic and abiotic to survive, thus demonstrating the theme of Interdependence. 2. The process of cytokinesis occurs immediately after mitosis in both animal and plant cells. This process and its outcome show certain similarities and differences in both animal and plant cells. Cytokinesis is similar in plant and animal cells because it results in the production of two daughter cells resembling the parent cell in all aspects (p 366). Plant cytokinesis on the other hand differs from that of animal cells by forming cell plates which separate the cytoplasm of the two daughter cells along the equator of the spindle instead of a contractile ring as is the case in animal cells (Roberts). 3. Eukaryotes have their nucleus and other internal organelles enclosed within a membrane as opposed to that of prokaryotes. This structural advantage makes eukaryotes capable to metabolize their food more efficiently than prokaryotes. In both cells, the use of flagella is a paramount survival adaptation. The flagella are used as the main tool of locomotion in both the prokaryotes and eukaryotes (p 35). In addition to the use of flagella in locomotion, prokaryotes use it to protect themselves against adversaries by lashing it out. This use is replaced by employment of more complex and well developed organs in eukaryotes (p 37).The cytoplasm in prokaryotes is serves one of the many vital functions served by the cytoskeleton of eukaryotes. These two features serve to bring about transportation of substances within each of the two cell types. 4. The end products of mitosis and meiosis differ in some very important ways. Mitosis occurs in one cell division whereas meiosis occurs in two. While mitosis results in the formation of two diploid daughter cells identical to the parent cell, meiosis results in four haploid daughter cells different from the parent cell. Mitosis facilitates asexual reproduction while meiosis enables organisms to reproduce sexually as explained by Roberts. The two processes differ in that a cell undergoing meiosis will divide two times; that is meiosis 1 and meiosis 2 resulting in the halving of chromosome number (p 372). In meiosis, homologous chromosomes associate during metaphase 1 where chiasmata form leading to the exchange of genes (Roberts). The importance of this crossing-over of genes leads to variations in organisms. 5. The table shows substance A to be an RNA and substance B a DNA. It is also found that substance A is a ribose sugar while substance B is a deoxyribose sugar. My identification of these sugars is supported by findings indicating that RNA is composed of nucleotides called ribonucleotides where the sugar is ribose (Roberts 381) while the DNA contains the sugar deoxyribose. It is also demonstrated that both substance A and B have bases adenine, cytosine and guanine in common but each has a unique nitrogen base absent from either one. Substance A has base uracil which is replaced by base thymine in substance B. The bases of the separate DNA strands associate with each other during replication by forming a template (p 382). 6. To do DNA sequencing gel technology, it is critical to collect undisputable evidence by gathering the right samples. Roberts explains that “in identifying individuals, it is advisable to scan 13 DNA regions that vary from person to person and use the data to create a DNA profile of that individual”. This wide range of sample collection ensures that chances of individuals having the same DNA sequencing for a particular set of 13 regions are minimized (p 400). In view of this, I would collect as many samples as possible including blood traces from the victim’s cuts, torn clothing, and the scraps on each of the suspects. If the DNA sequence from the samples matches that of the suspects, then they are guilty. To prove that the suspects are brothers, their DNA sequence would be matched with parts from their parents (p 401). 7. From the feeding relationships shown, algae fall in the first trophic level acting as a producer while the small animals and protists occupy the second trophic level acting as herbivores and are thus considered the primary consumers. The Cod, Krill, Squid and the Adelle penguin are all omnivores with varying sources of food. The carnivores include the Crabeater seal and Elephant seal; Leopard seal and the Killer whale acting as secondary, tertiary and quaternary consumers respectively (Roberts). In the feeding relationship, I would place a detritivore at the bottom of the feeding relationship below the Algae since they form the substratum particularly in an aquatic ecosystem. A decomposer on the other hand could be placed at the top of the feeding relationship above the Killer whale. The feeding relationships represent a food web because it involves several food chains linked to one another (Roberts). 8. Rising levels of CO2 concentration in the atmosphere have been attributed mainly to human activities particularly through burning of fossil fuels, urbanization and increased industrialization as cited by Roberts (254). The burning of fossil fuels such as coal and oil and deforestation have resulted in the accumulation of "greenhouse gases" in the atmosphere with the overall effect of trapping heat as recorded by Roberts (255). Consequently, the earths temperature is ever increasing as evidenced on the graph. From the graph, CO2 concentrations in the atmosphere increased from approximately 280 parts per million in pre-industrial times (Roberts) to about 330 parts per million in 1980. They are predicted to increase further to 390 parts per million by the end of 2010. 9. The controversy whether viruses are alive or not is a long standing one. Scientific evidence available convincingly demonstrates that viruses are NOT alive. At the outset, living organisms are known to have need for nutrition, reproduction, growth and development, irritability, gaseous exchange, respiration, locomotion and excretion (Roberts). In view of this, viruses do not show all of the listed characteristics even though they might manifest just some of them. Roberts argue although viruses mutate and replicate, this cannot be considered as reproduction. In fact they require a living host cell in order for them to reproduce (p 38). It is further noted that since viruses don’t have a need for food, they do not use energy like living organisms. 10. A codon of three base triplets coding for a particular amino acid is transcribed onto the messenger RNA (mRNA) which moves from the nucleus to the cytoplasm (Roberts). In the cytoplasm, the mRNA attaches itself to ribosomes for protein transportation. The process of protein synthesis is started off by ribosomes offering sites for protein synthesis. After the proteins are synthesized in the ribosomes, rough endoplasmic reticulum transports them within the cytoplasm (Roberts). Further, Golgi apparatus form vesicles that contain materials to be transported. An example of these vesicles formed at the last stage of the synthesis process is the lysosomes which destroy worn out organelles (Roberts). Finally, the cell membrane encloses the synthesized proteins within the cell to be metabolized for growth and repair. 11. The genotype for the mother is a carrier for the trait shown as XCXc for color blindness while the genotype for the father is normal for the trait shown as XcY. The X chromosome carry the trait for the disorder while the Y chromosome is genetically empty (Roberts 480). The disorder involved in this pedigree is considered dominant because it is not manifested in the carrier mother. The trait is suppressed in the presence of the dominant gene. The offspring affected by the genetic disorder are the daughters who inherit the trait from both parents (Roberts). The genotype of the affected daughters will be homozygous recessive for the trait shown as XcXc. Genetic counseling and testing can help the victims know the risks of having a child with the same abnormally (p 518) as well as being able to work out the probability of giving birth to an affected child. 12. The “envelope” is used as a “fence” to postpone the infection of host cells by the virus. The strategy used in preventing HIV infection is through reacting weakened viral strains with neutralizing antibodies to activate the immune system to be on high alert for any eventual infection and thus act as a vaccine (Roberts). This approach has not been tried on people for the simple reason that HIV resists antibody neutralization and may thus remain active (Roberts).Reverse transcriptase helps to develop DNA imitations which dupe the HIV virus to be unable to make functional replications thereby terminating its propagation in the body (p 530). 13. The kingdom plantae comprises of four major plant groups including the nonvascular mosses and liverworts collectively known as Bryophytes. Transport in these plants occurs through diffusion. The plants are in permanently moist places like shady river-banks, moist woods and on wet rocks (Roberts).The Pteridophytes have the ferns which are highly differentiated into roots, stems and leaves but have no flowers (Roberts).Most of them grow on rock substrata and waste land. Gymnosperms are the non-flowering plants which produce naked seeds in cones. Their leaves are needle -like structures covered by a thick cuticle and reduced stomata to reduce water loss through transpiration. The angiosperms are the flowering plants capable of forming seeds in the ovary of the flower. This group is divided into the monocotyledons and the dicotyledons. 14. The main parts of a plant include the roots, stems, leaves and even flowers. Roots have the function of anchoring the plant firmly into the soil to provide support as well as absorb water and mineral salts needed for growth. They are also used as storage organs for manufactured food substances and for gaseous exchange. The stems on the other hand provide mechanical support to the plant and conduct water, mineral salts and manufactured food substances to other parts of the plant. They are further used as storage and perennating organs and as surfaces for gaseous exchange (Roberts).The leaves play an important role in photosynthesis and in gaseous exchange as well as in transpiration through the stomata. The presence of the vascular bundle facilitates the transportation of materials within the plant as cited by Roberts (190). 15. An annual plant is any plant that completes its entire life cycle within a single growing season (Roberts). The entire plant dies a t the end of each growing season as observed in most cereals. Biennial plants on the other hand require two years to complete their life cycle where in the first season, growth is characterized by sprouting of small leaves which elongate into a stem, flower and form seeds before dying in the second season of growth (Roberts). A good example of plants in this group is the carrot. Finally, perennial plants persist for many growing seasons like the Tickseed plants which retain their leaves year after year (Roberts). Most of them have underground perennating structures for re-growth during favorable conditions. 16. Reptiles are cold blooded animals while birds are warm-blooded. Cold blooded animals have their body temperatures fluctuating with that of the environment unlike the homeotherms (p 210). They gain heat by absorbing solar radiation from the air in the presence of the sun which is absent in the Arctic. For this reason, reptiles find it hard to live in the Arctic. Birds on the other hand are capable of maintaining their body temperature at a constant despite wide fluctuations in the temperature of the external environment (Roberts). They use physiological and behavioral mechanisms to do this. For instance, they increase their metabolic rate to increase their body temperatures and fluff up their feathers to keep warm (p 211), thus enabling them to live in the Arctic. 17. Fish gills maximize the surface area available for oxygen exchange by having two roles of numerous filaments which are long and trail in water. The filaments are further subdivided into gill lamellae to offer a large surface area for efficient oxygen absorption (Roberts). It is also evident that the filaments are lined with a rich network of blood capillaries and are kept moist throughout to allow for easy diffusion of gases across the thin membranes. Secondly, fish employ the countercurrent flow system where water and blood flow in opposite direction to allow maximum extraction of oxygen from water to blood (Roberts). As the water enters the gill chamber, its oxygen concentration is higher than in the blood, hence increasing the rate of oxygen diffusion. 18. The reptile’s egg is capable of surviving out of water without drying up and can use atmospheric air contained in the airspace of its shell. Similarly, the supply of water in the egg provides the embryo with the aquatic environment it still requires for growth and development as stated by Roberts (444). This adaptation enables reptiles to exploit most of the dry-land environments they occupy. On the other hand, reptiles possess lungs which are used to compensate for a lack of supplemental oxygen intake through moist skin like that of amphibians as explained by Roberts (440). Reptiles have developed scales that reduce water loss to the atmosphere and act as protective devices in larger reptiles. This in my view is more important to reptiles than having internal fertilization. 19. The mammalian heart has two upper atria which receive blood and two lower ventricles which pump blood (p 170). The right atrium receives blood from body parts via the vena cava while the left atrium receives blood from the lungs via the pulmonary vein. The right ventricle pumps blood to the lungs via the pulmonary artery for oxygenation and the left ventricle pumps blood to all parts of the body under pressure via the aorta (p 170). For the heart to functioning properly, it is divided into pulmonary and systemic circulations. The former carries oxygenated blood from the lungs through the left atrium into left ventricle then to body parts while the latter carries de-oxygenated blood from body parts through the right atrium into right ventricle then to the lungs (p 168). 20. Carbohydrates, proteins and lipids are mainly for energy giving and body building to while vitamins, minerals and water are basically for protection and regulation of body functions (p 60). According to Roberts, carbohydrates and lipids are the major sources of energy for the body with lipids yielding twice as much energy obtained from the same amount of carbohydrates (64). Proteins form the major structural component in most body tissues and fluids (p 72) in addition to supplying energy. Vitamins on the other hand are required for normal growth and regulating metabolism while minerals are critical in certain physiological functions such as the functioning of the nervous system (p 58). Finally, water is used as a universal solvent and as coolant in the body. 21. HIV transmission is through sexual activities where as non sexual activities provides the widest range of avenues (Roberts). Drug addicts who share needles and syringes or other skin piercing instruments may cause mixing of infected blood. Transfusion of contaminated blood and organ transplants may expose patients to the virus (Roberts). Also mother to child transmissions have been reported. Studies have shown that HIV cannot be transmitted through air because the virus is destroyed through desiccation when exposed to air (Roberts). The virus disables the immune system by damaging the CD4 cells which help the body fight against diseases. The victim’s viral load rises as the CD4 count drastically declines making their bodies susceptible to opportunistic infections as a result of reduced immunity (Roberts). 22. The guard cells contain chloroplasts which have chlorophyll necessary for the process of photosynthesis. When photosynthesis occurs in the guard cells, sugars accumulate raising the cell sap concentration in the guard cells. This forces the guard cells to draw water from the adjacent cells through osmosis to bring the concentrated cell sap to equilibrium with that of other cells (p 181). This causes the guard cells to swell, bulge outwards thereby opening the stomata. The open stomata eventually allow water molecules to escape into atmosphere. If the plant does not have enough water therefore, the rate of transpiration will be greatly lowered. This is due to the fact that the guard cells remain flaccid and hence close the stomata as explained by Roberts (182). 23. The numbered locations 1, 3 and 4 are at the resting potential because the neuron negatively charged in the inside. The predominant ions inside the neuron are sodium (Na+) and chloride (Cl -) ions while those on the outside are potassium (K+) and negatively charged organic ions (Roberts).The numbered location 2 shows an action potential since the neuron is positively charged in the inside. At location 2 the cell membrane is permeable to sodium ions because it is the location where the nerve cell is stimulated. Here, Na+ diffuses rapidly into the inside of the neuron increasing the permeability of the membrane to K+. When an action potential reaches location 4, it stimulates the knob to discharge certain transmitter substances which facilitate the transmission of the impulse across the synapse (Roberts). The response is chemical at location 4. 24. Since arthropods are invertebrates, they lack a vertebral column found in the vertebrates. To have support for tissues and organs, arthropods have developed a hard exoskeleton made of chitin and cuticle which protects the arthropod against desiccation, mechanical injuries and predation (p 439). Additionally, the exoskeleton acts as sites for muscle attachments for wings in the flying arthropods. However, the exoskeleton becomes a limitation during the growing process of the arthropod. But arthropods have been able to overcome this handicap by being able to shed off the hardened exoskeleton through molting or ecdysis. The molting process is under the influence of hormones secreted from the endocrine glands. List of works cited Roberts, M. B. V. Biology: A functional approach. Nelson Walton. Kensington, London, 1985, 4th ed. Read More