Lesson 5 Answers:
24.) Plants are classified into four major groups: Bryophytes, Pteridophytes, Gymnosperms and lastly the Angiosperms. Bryophytes are the plants that do not have true vascular systems, which consist of the xylem and the phloem. In this group, includes the mosses, liverworts and hornworts. Together, they are considered as land plants that reproduce their own asexually by producing spores. Spores are produced in the ‘sporangium’ (plural sporangia), a bulb-like structure located at the top of the stalk. It can only be seen through the use of high powered microscope. Because they lack vessels that can bring the nutrients from the roots to the leaves, we can see these plants hanging on top of the trees in order to survive. They needed moist air to grow, and the presence of mosses in a place suggests clean air. The second groups of plants, the pteridophytes are plants that have vascular systems. Like the first group, they reproduce their own kin through asexual reproduction. Plants, which belong to this group, are ferns and horsetails. They have the xylem that regulates the flow of water from the roots to the leaves and phloem that regulates the flow of nutrients from the leaves to the roots. Ferns and horsetails are known to produce spores, which can be seen on the back of a mature leaf. They look like small rows of dots called ‘sori’. Each ‘sori’ contains sporangia, a small bulb-like structure that produces spores and each spore grows into small plants called ‘gametophytes’. The gametophyte reproduction is known as the sexual reproduction and involves the union of the sperm and egg within the plant. On the other hand, the reproduction through spores is known in biology as ‘sporophyte reproduction.’ Like bryophytes, pteridophytes survives in moist air and most of these plants can be seen growing under the shade of much bigger trees. The conifers make up the third group of land plants called gymnosperms, which means ‘naked seed’ in Latin. These plants produce seeds enclosed within a cone. Seeds unlike spores are multi-cellular and they contain enough nutrients to support the growth of the plant. Pollen cones are produced by conifers to develop ‘microsporangia’ and undergo meiosis stages in order to make pollen grains. In order for the fertilization to take place, the pollens need to be blown by the wind to reach the female cones to produce seeds. The produced seeds are not encased within the ovary of the plant; hence, it is called as a ‘naked seed’. Angiosperms or the flowering plants are the final group which is the represents supremacy in the evolution of the plant. Flowers attract many insects, animals and including human which assists them through the reproduction process. They contain the complete vascular structure and the male and female organs responsible for producing both egg and pollen grain. For example, the hibiscus flower is considered as a complete flower because it includes both the stamen and the ovary. The stamen is the male part that produces pollen grain whilst the ovary is known to produce eggs. The fertilization takes place within the ovary of the flower until it reproduces another plant of its own kind.
25.) The four major parts of the plant are the roots, stem, leaves, and flower. The roots absorb the nutrients and minerals from the soil and because the roots are spread out, it helps the plants to stay firm in the soil. The stem is similar to the function of a straw; it serves as a road for transporting minerals from the roots to the leaves. The stem has two parts the phloem and the xylem. They have the xylem that regulates the flow of water from the roots to the leaves and phloem that regulates the flow of nutrients from the leaves to the roots. A leaf is the part of the plant that comes in different sizes, shapes and alignments. Leaves are colored green because of the presence of the chlorophyll in them. They are responsible for making food for the plant and in order to do this, they absorb the sunlight from the sun and carbon dioxide from humans and animals. The last part is the flower, which is the center of the plant reproduction. In this structure, the plant is able to make another plant of its own kind.
26.) Plants are classified according to their lifecycles. Annual is the type of plant that performs their duties of reproducing a seed and a flower in a single season. After one year planted, all of their parts die including roots, stems and leaves leaving only their seeds to grow in another plant. One example of annual plants is the Annual Plains Coreopsis. Biennial are the second type of plants whose lifecycle is for two years. They produce flowers and seeds in their second year and die after it. Biennial Foxglove is the best plant to represent the plants living in this lifecycle. Perrenial is the plant that lives for many growing seasons. These plants can live through years of harsh cold and heat and can survive for many years. Example of a perennial plant is the Perennial Purple Coneflower.
39.) Reptiles do not live in the Arctic because they are ‘ectothermic’. Ectothermic means animals belonging to this kind cannot produce their own body heat so they would likely die in cold climates. Reptiles need warmth in order to survive whilst birds are ‘endothermic,’ meaning they can generate their own body heat just like humans that is why there are some birds that can live in the Arctic. They always have an option to migrate or adapt to the climate changes. The presence of their feather makes it easier for them to generate body heat whereas reptiles does not have any body coverings to protect them from extreme cold.
40.) Fish breathe through their gills and gills maximize surface are available for oxygen exchange by means of counter-current exchange. When immersed in water, the gills pump the blood in the opposite direction to allow more of the fish’s blood to absorb more oxygen. Countercurrent exchange is the process in which blood from the capillaries flows in adjacent directions allowing gases to diffuse faster. The efficiency of this gills is further maximized when the fish through ventilation when the fish is swimming and by opening and closing the ‘opercula’ or the flaps that cover the gills. This movement draws in fresher water with oxygen to their mouth passing the gill slits.
41.) Reptiles have specific adaptations enabling them to survive in the environment. They are cold-blooded animals and because of this, they need sufficient heat to live. They are ectothermic and instead of relying to its body temperature, these animals use the water temperature similar to what amphibians do. They maximize the heat coming from their environment to warm themselves and they hide under the trees when the heat during extreme heat. They lay their eggs covered with thick, hard calcium or leathery coats to keep the water in. By laying eggs with regulated amounts of water, they can monitor the temperature inside and out and thus locking in moisture so that their babies will not dry out. Whenever they are on land, reptiles does not rely absorbing oxygen using their skins just like amphibians, instead they use their lungs too for them to breathe and similar to crocodiles, they rise out from water in order to get air. Internal fertilization in reptiles is more important because it ensures the protection of the developing organism during the reproduction process, and internal fertilization will help them to produce more species of their own kind. In the absence of the internal fertilization, it will be harder for them to reproduce because their eggs will always be on danger whether from extreme climates or other animals. Scales aid them in surviving harsh environment because it regulates the heat and flow of water. In addition, their scales serve as a protection from dangers of the surroundings.
Lesson 6 Answers:
34.) The deoxygenated blood enters the heart through the superior vena cava and inferior vena cava. From the right atrium, the deoxygenated blood goes into the heart’s right ventricle via tricuspid valve. The structure of this valve has three flaps to close the opening between the ventricles and the atrium, thus preventing blood to go back to the atrium. The moment the right ventricle walls contracts, the movement empties the deoxygenated blood through the pulmonary semi-lunar valve towards the pulmonary artery where it transports the blood to the lungs to become oxygenated. This process is known as the pulmonary circulation. Systemic circulation is the process in which the blood leaves the heart to distribute the oxygen into the body’s cells and re-enters the heart again. This starts when the oxygenated blood leaves the left ventricle to go to the aorta, our body’s largest artery. The aorta branches into smaller arteries, arterioles and capillaries. These capillaries merge to become venules which merge into veins. The great veins superior vena cava (responsible for draining blood above the heart) and the inferior vena cava (responsible for draining blood below the heart) pumps the oxygenated blood into the right atrium of the heart. Thus, our four major blood supplies are:
*Deoxygenated blood→venae cavaes (body→right atrium)
*Deoxygenated blood→pulmonary semi-lunar valve→pulmonary artery (right ventricle →lungs)
*Oxygenated blood→pulmonary vein (lungs→left atrium)
*Oxygenated blood→aorta (left ventricle→body)
35.) Our body needs sufficient supply of nutrients to maintain a healthy immune system. Carbohydrates are our body’s prime source of energy and the essential nutrient used by our cells, which promotes the proper metabolism of our nervous system and of our red blood cells. The first three nutrients are classified as macronutrients. Macronutrients like water, carbohydrates, proteins are essential nutrients that we need in large amounts to for our body’s growth and metabolism, hence, ‘macro’ means ‘large’. Micronutrients like vitamins, minerals and fat (lipids) should only be taken in small dosages. A well balanced nutrients present in the body can promotes a healthy living. Water is used by the body to provide fluid needed by our cells to function. Water also helps to regulate our body temperature. Carbohydrates serve as our fuel for our daily activities and for providing heat. Fats or lipids are essential for maintaining energy to do the activities. Vitamins are used for our body’s metabolic processes for strengthening the immune system.
36.) Viruses do not fit into any kingdom of life, They do not have membranes of their own, no ribosomes on which they can create proteins, no presence of cytoplasms and no energy source. Viruses cannot move nor grow and they can only reroduce inside a host cell. HIV or the Human Immuno Virus is a type of virus that belongs to the group Lentivirus, a group of viruses that has long incubation period. HIV virus is trasmitted during sexual intercourse, by having multiple partners. This type of virus is not trasmitted through the air because it is a retrovirus. Retroviruses coming from the prefix ‘retro’ means ‘reverse’. Retroviruses replicate nucleic acid in the reverse of the standard way. Rather than using DNA to make RNA, retroviruses first creates DNA from RNA. The viral core of the HIV virus is made up of RNA and an enzyme that is different from the core of other viruses. The case of retroviruses are studied because they cause some kinds of cancer and leads to AIDS. HIV transmission occurs through blood donation, semen ejaculation, vaginal fluids, saliva and even breast milk. This is a very deadly virus because it weakens the host cell, thus allowing opportunistic ailments to enter the body such as tuberculosis and cancer. Although there are no cure for the HIV virus, scientists has discovered a way in treating the virus. As of this day, there are 31 drugs used in HIV treatment. Abacavir is the main drug prescribed for a person having HIV. This drug is an anti-retroviral agent, meaning it ‘freezes’ the bacteria inside the host cell, thus making the bacteria latent and preventing further damage. Abacavir sulfate and Lamivudine is a combination of anti-retroviral drug used to block HIV reproduction in HIV-1 cases. These drugs interrupt the growth of the HIV bacteria and thus lessen the transfer rate to other people. Drugs are used to reduce HIV bacteria and to stop the transfer to other people.
Part 2 Examination Answers:
39.) If a plant does not have enough cells, it would be very crucial for the plant to maintain an ample supply of water it needs to make food. Plant transpiration is the systemic process of water movement within the plant and its evaporation from the leaves, stems and flowers. Under the high powered microscope, if we examine a leaf we can see its surface dotted with small opening called stomata. In each stomata, there lies the guard cells that are found enclosing every plant’s stoma. These cells are responsible for regulating transpiration rate. Their main function is to open and close the plant’s stomata. At daytime, guard cells get filled with water to support the plant and this makes them more bulgy and open. During nighttime, guard cells lose their water content that’s why they lose their turgidity which makes them close the openings. Plants that have enough water stored, guard cells around each stoma become bulgy and thus, make the stoma open. In some cases, if the plant does not have enough supply of water, the guard cells becomes flaccid and closes the stoma opening. If the guard cells remains closed, a plant cannot drain the excess water from its stoma and the transpiration process becomes slow.
40.) A neuron is a basic functional unit of the nervous system. It consists of a cell body and two types of fiber-like structures. These branched structures attached to the cell body are called dendrites which receive and carry information toward the cell body. The long structure that extends from the cell body is called an axon which transmits nerve impulses away from the cell body. Each neuron has only one axon but can have many dendrites. The network of axons and the dendriyes of the neurons are collectively called nerve fibers. Nerve fibers are bundled into structures called nerves. In the central nervous system, nerve fibers are bundled in structures called tracts. The nervous system functions to transmit signals through the body in the form of nerve impulses. A nerve impulse is a wave of chemical and electrical change that is conducted along the membrane of a neuron. A neuron can switch from a resting to an active state and back to the resting state in a few thousandths of a second. In the resting state, the inner surface of a neuron has a negative charge compared to the outside. The electrical charge across the cell membrane of a neuron in the resting state is called the resting potential. Referring to the illustration, the locations numbers 1, 3 and 4 are the places in the neuron that is in its resting potential. However, when the neuron is stimulated, the charge across the cell membrane reverses. The reversal and restoration of charges across the cell membrane of a neuron is called the action potential, also known as a nerve impulse. The location number 2 is the part of the neuron in its active state. The locations 1 and 2 are the permeable places to sodium ions. In the middle of the axon, three sodium ions bind to the protein channel and an ATP (adenosine triphosphate) gives the energy to re-shape the channel that drives the ions through the channel. One phosphate group coming from the ATP remains with the channel then the sodium ions are emptied on the other side of the membrane and the new shape of the channel has a high affinity for potassium to bind to the ATP channel. The binding of the ions creates a significant change in the channel’s shape and this change discharges the phosphate ions to the cytoplasm. The release allows the protein channel to return to its original shape to allow the release of more potassium ions inside the cell. Back to its original shape, the protein channel has a high affinity for more sodium ions from the outside part of the cell and when the ions bind once more, another cycle begins. Sodium and potassium pump works when both sodium and potassium ions moves from low concentrated areas to high concentrated ones. Meaning to say, every ion is moving against its own concentration gradient. Sodium and potassium pump can only be made if there is an ample supply of ATP proteins. When the action potential reaches the end of the cell (dendrites), it becomes a synapse which causes the depolarization of the cell membrane, creating an ion influx. The locations 1, 2 and 3 the neuron’s response is mostly chemical due to positive sodium particles outside the cell.
41.) Arthropods make up the largest phylum in the animalk kingdom. They include some of the most valuable and the most destructive animals such as the spiders, scorpions, millipedes, centipedes, lobsters and crabs. Most of them are fairly small, some are microscopic and others can be as large as five meters. They are found in every habitat on earth. Arthropods are segmented and most segments have paired, jointed appedage for flexibility in movement. An appendage is a body extension, such as the antenna or a leg. Arthropods also have exoskeleton, a hard covering that provide support and protection for the animal. The exoskeleton is made up of a protein bound to a tough polysaccharide material called chitin. The exoskeleton provides a framework for the muscles that move the appendages. In order to grow, arthropods shed their exoskeleton in a process called molting. Since arthropods lack an internal skeleton, the external skeleton provides them both skeletal support and barrier. Exoskeletons of various arthropods are made of a carbohydrate called ‘chitin’. Arthropods shed their exoskeleton coverings as they grow and when they became bigger than their coverings, they make another exoskeleton to fit their new size. The importance of these external structures on these animals is the protection and support it provides to them.