Living Environment 1
(a) We started the term talking about the Scientific Method. We also learned the steps of the Scientific Method. These steps include: (i) Identify a Problem (ii) Make Observations (iii) Research (iv) Hypothesis (v) Experiment (vi) Data Analysis (vii) Conclusion Notes: The Hypothesis statement MUST start using "If"_____________________ followed by, Then" ______________________________. Your experiment must always be a Controlled Experiment, where ONLY one Variable is being changed by YOU or the Investigator. Also note that their are TWO groups involved in an Experiment: These are the Control group and the Experimental group. In the Control group, everything remains the same, whereas in the Experimental group, here is where you will change the ONE thing (VARIABLE), which will also produce some type of change as a result. We mentioned the TWO types of Variables in an Experiment. One is called the Independent Variable, the ONE thing that YOU change. The other is called the Dependent Variable, this is the thing that changes or HAPPENS as a result of the Independent Variable. When your Experiment is completed, you will need to collect and organize your DATA using Tables and Charts or Graphs. How would you know what Data to collect for your Experiment: Well you should refer to the Hypothesis statement for clues about the type of Data you are to collect. When doing the graph, please note that the Independent Variable goes on the X-axis and the Dependent Variable goes on the y-axis. The graphs that you make can be either Line graphs or Bar graphs. You have a choice unless otherwise instructed. Upon completion of the Scientific Method, we focused on the Safety Procedures needed in the Laboratory. Students should refer to class noters and handouts for all safety measures that MUST be carried out in the Lab. Make sure that you guys are aware of the safety symbols posted all over the Lab. The format for writing up your Lab. report is as follows: (a) Introduction (b) Problem (c) Materials (d) Procedures (e) Data and Analysis (f) Conclusion This was all the material that we covered for the week of Sept. 8th-15th, 2005 Please be aware that ALL LABs. are due Monday morning and that you are having your first EXAM on Thursday Sept. 22nd, 2005. The Exam on Thursday will cover the Scientific Method ONLY. You will have 10 Multiple Choice Questions and a Problem that requires you to set up your OWN Data Table and construct a graph. It will be very much similar to the Homework question you guys were working on on Friday. For the week of Sept. 26th, 2005, we will be looking at our new Topic: Characteristics of Living Things. On Sept. 29th, 2004, we agreed upon some characteristics that were common in every living thing. These characteristics were as follows: (a) Living things are made up of units called cells. (b) Living things reproduce. (c) Living things are based on a universal genetic code. (d) Living things grow and develop. (e) Living things obtain and use materials as energy. (f) Living things respond to their environment. (g) Living things maintain a stable internal environment. On Thursday Sept. 22nd, 2005 we will talk about the components that make up the cell. You should picture this like a team that has many players. It is very important to understand the roles or function of all the players that make up a cell. We already agreed that all living things are made up of cells, and that cells are the building blocks of life. Now we will explore the structure and components that make a cell what it really is. The parts of cell also called organelles, are like players on a team. This means that every part has a specific task in order for the cell as a whole to survive. Think of this like a game, where every player has to do a job in order for the team to win. Let us now get to know these individual players: The first player is the cell membrane. The cell membrane is the outermost part and it gives the cell its shape and it also protects the cell from the outside environment. The cell membrane can also allow certain particles inside the cell, whereas it can prevent other particles from coming in. Once you cross the cell membrane, you will reach a jelly like layer called the cytoplasm. This is the liquid part of the cell and it surrounds all the other parts inside the cell. The cytoplasm can be pictured as the water in a circular pool. The next part is probably the most obvious. The nucleus is located usually in the center of the cell. It controls all the activities in the cell. It is sometimes called the captain of the team or the boss of the cell. The nucleus also contains all the genetic information. This genetic material is carried to the next generation when the cell reproduces or divides. The mitochondria is the organelle responsible for making all the energy for the cell. It is sometimes called the powerhouse of the cell. This organelle also carries genetic material. The ribosome is another organelle in the cell and is responsible for making proteins for the cell. The ribosome can also store and keep proteins there. The lysozome is another organelle that is responsible for digesting and breaking down unwanted particles in the cell. Inside the lysozome is acid and if the lysozome ruptures or breaks, the acid can leak out and kill the entire cell. Before we go further, please realize that in a plant cell you have a few additional organelles. In the plant cell you have a cell wall, which allows the plant to have a rigid and strong stature. It is the reason why plants and trees can stay upright and not fall down. The plant cell also has organelles called chloroplasts. Here in the chloroplasts, is where photosynthesis takes place. We will continue talking about the differences between plant cells and animal cells on Tuesday Sept. 27th, 2005. In the meantime you guys should be studying for your Test #2 on Thursday Oct. 6th, 2005. This Test will only be on the cell and its parts and functions and Transport. Today we learned the differences between plant and animal cells. We were able to see how these differences gave the cell a whole new function. These differences were: in the plant cell you have chloroplasts, cell wall, and also a large vacuole. There is one or two more differences but we will consider those later on. The animal cell lack these structures and that is what makes the big difference between plants and animals. Once we are aware of all the structures and functions of the organelles in the plant and animal cells, we now have to learn how can materials get in and out of the cell. Recall: that the cell membrane was responsible for allowing materials to enter and leave the cell. Well, in many cases, the cell membrane cannot prevent small particles like gases and ions into the cell. The movement of these gases and ions into the cell occurs as result of Diffusion. Diffusion is the movement of materials such as gases, water, ions and other small particles in to the cell from a degree of higher concentration to a degree of lower concentration. You can think of diffusion as a stadium full of people. When the game is over, the people inside the stadium then gradually leaves. After some time, there will be no one left in the stadium. Outside the stadium is where everyone is going to be. Another example can be the classroom. When you guys are in the classroom, it can be view as a concentration inside the room. When the bell rings, you guys then start to diffuse into the hallways. After a minute or so, there will be no one left in the classroom but ME! Notice how you guys MOVE from a degree of HIGHER concentration from inside the classroom to a degree of LOWER concentration outside the classroom. If you still don't get the concept of Diffusion, send me an e-mail and I will again explain it to you. Next we spoke about how materials like gases, water and ions can get into and out of the cell by a different mechanism. This mechanism does the opposite of diffusion. That is, materials come in and out of the cell by going against the concentration gradient. But for this to happen, ENERGY has to be available. We called this process Active Diffusion, where materials move from a degree of lower concentration to a degree of higher concentration. Energy MUST be used up in this process. Then we mentioned Osmosis. This was like diffusion, where the only difference was that a cell membrane MUST be present. Osmosis is the movement of WATER molecules through a cell membrane. We then introduced the process of Plasmolysis, where water molecules can enter or leave the cell, depending on the salt concentration inside and outside the cell. When a cell is placed into a solution where the salt concentration is higher than the salt concentration inside the cell, the cell will tend to loose water, shrink and eventually die. This type of solution is called a HYPERTONIC solution. When the cell is placed in a solution where the salt concentration of the solution is lower than the salt concentration inside the cell, the cell will tend to gain water, swell up and eventually burst and die. This type of solution is called a HYPOTONIC solution. Please be aware that in the plant cell, the rigid cell wall prevents the cell from swelling in a HYPOTONIC solution. In a Hypertonic solution, the cell wall of plant cells also prevent the cell from collapsing or loosing its shape. However, everything inside the cell menbrane will be affected. That is, in a Hypotonic solution the cell membrane will swell up but the cell will not burst. In a Hypertonic solution, the cell will loose water and the cell membrane will shrink. Well, the first marking period has come to an end! Lets be prepared for the next marking period: We will be talking next about the organization of Living Things. We have seen how the basic unit of life structure and function is the cell. Now we will have to learn how these cells are organized to yield a Living Organism. The organization of Living Things is as follows: Cell -> Tissues -> Organs -> Organ Systems -> Organism. Notice that the organs in our body directly leads to a system. For example, the heart is the major organ in the Circulatory System. The lungs are the major organ in the Respiratory System. We then talked about organisms that just stop at the cellular stage in the organization above. These were cells that you guys saw last week in the lab. Like the ameba and the paramecium. These are called Unicellular organisms, for which the organism is made up of only one cell. Plants and animals are referred to as Multicellular organisms since we are made up of millions of cells. However, these differences still allow both multicellular and unicellular organisms to carry out their life functions. We also talk about Procaryotic cells and Eucaryotic cells. We agreed that in Procaryotic cells, you do not have a "TRUE" nucleus. That is, these cells don't have a Nuclear membrane. Whereas, in the Eucaryotic cells, there is a nuclear membrane. Examples of Procaryotes were the ameba, paramecium and bacteria. Examples of Eucaryotes are animals and plants. DIGESTION AND THE DIGESTIVE SYSTEM: We get our energy from the foods we eat. But before that happens, we all need to break down our foods into more simpler molecules so that our body can absorb all the nutrients. The Digestive System allows us to do that. Like the cell and the Microscope, the Digestive system has many parts, where each part performs a specialized function. Note that the Digestive tract is like a tube that has two openings. The first opening is where food enters. This part is called the mouth or oral cavity. The opening where waste materials from undigested and unused food gets released is called the anus. Once the food enters the mouth, we use our teeth, tongue and saliva (enzymes) to start the digestion process. Therefore, digestion first takes place in the mouth. Our teeth allow us to perform mechanical digestion, where our food gets grinded into small pieces. Then it is the role of the enzymes to now chemically break down the food into even simpler substances. The food then gets pushed down the esophagus. This a tube like structure that pushes food to the stomach. In the stomach, the food is further broken down using Hydrochloric acid and other enzymes like Pepsin. Pepsin is an enzyme that breaks down proteins in the stomach. Once the food leaves the stomach it is ready for absorption. Absorption takes place in the small intestine. In the small intestine are many fingerlike cells called villi. These villi are shape like this to maximize the absorption of the food. Once the food particles are absorbed, they are taken into the blood where the nutrients are carried to all cells of the body. Water is then absorbed in the Large intestine. CHEMISTRY OF LIFE: In our bodies, there are numerous chemical reactions that take place so that we can carry out the necessary functions of life. In a chemical reaction, molecules are broken down, so that new ones are made. New molecules are also made in a chemical reaction. In Living things, there are two types of chemical molecules. They are called Organic and Inorganic. Organic compounds are consisted of Carbon and Hydrogen elements. Inorganic compounds are compounds that do not have Carbon and Hydrogen. For example, glucose contains the elements Carbon, Hydrogen and Oxygen. Therefore glucose is an Organic compound. Others like sodium chloride and Oxygen do not have Carbon and Hydrogen and they are considered Inorganic compounds/molecules. Most of these compounds come from the food we eat. For example, Carbohydrates is an Organic compound that comes from foods like bread, pasta and potatoes. Carbohydrates are grouped into two categories: They are starch and sugars. We use carbohydrates for energy. That means that we get all our energy from foods rich in carbohydrates. Carbohydrates can be simple or complex in the way they are made up. For example: one simple sugar (a monosaccharide) added to another simple sugar gives you a double sugar called a disaccharide. When you add all these monosaccharide together, you get what is called a complex carbohydrate called a starch. Animals and Plants can save these starch compounds for energy to use later on. However, animals save starch in the form of glycogen. Plants save them as starch. Note that the cell wall in the plant cells are made up of a complex carbohydrate called cellulose. Proteins are needed for growth and tissue repairs. We get our proteins from fish, meats and eggs. Like carbohydrates, proteins are also made up of smaller units. These units are called amino acids. Each amino acid is boned to another by a peptide bond. When you have a lot of amino acids together, they bond to form a polypeptide. Therefore, a protein is really a polypeptide that contains many amino acids. Some proteins use more amino acids than others, depending on their size and length. Enzymes, Hormones and other structures are made up of proteins. Fats are needed to keep our bodies warm and it also is used as a form of stored energy. Fats are made up of three fatty acids and glycerol. Another name for a fat is called a Lipid. Please note that the cell membrane of cells are made up of Lipids and Proteins. The other organic compound is the Nucleic Acids that make up our DNA. We will talk about this more when we discuss reproduction and development. Our next Human System deals with the circulation of blood throughout our body. The body gets all of its nutrients and oxygen from our blood. Blood is continuously bringing new oxygen and nutrients to all of our cells in the body. It also allows us to get rid of Carbon Dioxide and other wastes products like urea. The blood is made up of several parts: The liquid part of the blood is called Plasma. It contains mostly water and nutrients, enzymes, hormones and other small proteins. The other component of the blood is red blood cells. These cells are made in the bone marrow and are responsible for carrying oxygen to all of our cells. The hemoglobin in these red blood cells is what makes these cells red. The white blood cells are responsible for fighting and getting rid of infectious particles like bacteria and viruses. These are like the body guards of our Circulatory System. They are responsible for keeping us healthy and free from diseases. The last component of the blood is the platelet cells. These cells are responsible for making blood clots when we get an injury. These cells come together and form a scab to prevent any blood from being lost. People that have genetic disorders in this gene often bleed to death when they get injured. The blood plays are very important role in Circulation. The major organ in our Circulatory system is the heart. The Heart is made up of 4 chambers. The 2 atriums and the 2 ventricles. The right atrium and the right ventricle is located in the left hand side of the heart. The left atrium and the left ventricle is located on the right hand side of the heart. The Aorta is the major artery in the heart. The Heart pumps blood to the lungs ( pulmonary circulation) and also to the rest of the body (systemic circulation). All the deoxygenated blood from all of our cells are taken to the lungs where Carbon Dioxide can be exchanged for fresh oxygen. Then the oxygenated blood is returned to the heart to be pumped to all parts of the body. The body uses a series of veins and capillaries to make sure that oxygen and nutrients reaches all parts of the body. In the veins you have valves that prevent the backflow of blood to the heart. When you do exercise, your heart rate increases and the flow of blood to your body cells also increases. Blood Pressure is the measure of your blood when it hits the wall of your veins and arteries. If your pressure is too low, you may not be getting the circulation that you require. If the pressure is too high, you may be overworking your heart. In both cases, you may get sick and even die, if immediate attention is not given. There are a host of disorders and diseases of the Circulatory System. Heart Attacks which often occurs when arteries are clogged up with cholesterol and fatty film. Strokes are associated with blood clots in all parts of the body. Anemia occurs when the red blood cells are not carrying enough oxygen to your cells. This is due to a lack of hemoglobin in your red blood cells. We will talk about Autoimmune diseases like AIDS when we talk about the Immune System. The next system that we are going to talk about deals with the exchange of gases in multi-cellular living things. This system is called the Respiratory System. Respiration consists of two concepts: One is how cells break down glucose to get energy (we will talk about this later on) and the other is how Carbon Dioxide is exchanged for Oxygen (gas exchange) in our bodies. Please note that the Circulatory System plays a major role in the delivering of Oxygen to all cells and the removing of Carbon Dioxide from the body. This is done when blood is circulated throughout the body via the blood vessels we spoke about (these were the capillaries, veins and the arteries). The Respiratory System consists of the nose, where air enters, the pharynx, which serves as a passage-way for food and air, the trachea or windpipe which also allows air to pass. The trachea also connects the pharynx to the bronchi, which eventually leads to the lungs. Note: while the air is passing through all these parts, it is cleaned and moistened so that germs and other particles can be removed. The Respiratory tract is lined with tiny hairs that cling on to these particles allowing the air to be clean before it reaches the lungs. Once the air reaches the lungs, by way of the bronchi tubes, it is carried into the millions of air sacs called the alveoli. Here is where the actual gas exchange between Carbon Dioxide and Oxygen takes place. Recall that the alveoli, like the villi in the small intestine is covered with capillaries. This allows the Oxygen and Carbon Dioxide to be exchanged very quickly and efficiently by Diffusion. The heart pumps the blood to the lungs ensuring that the blood gets oxygenated in time for all the cells in the body. The diaphragm is a muscle that lies under the lungs and it contracts when we breathe allowing our chest cavity to expand. This week we will talk about the Excretory System which allows us to get rid of all the metabolic wastes from our body. The Excretory System allows us to get rid of all the metabolic wastes in our bodies. Waste materials include Carbon Dioxide, urea ( a combination of nitogenous waste and other chemicals from cellular metabolism), excess water through our skin and also the removal of dead and old Red Blood cells from our Circulatory System. There are a few organs that play important roles in making sure that our bodies are maintained and waste materials are excreted. These organs include the Kidneys for which cleans and filters our blood from urea and excess water. The Liver, removes the old and dead Red Blood cells that has been in our Circulatory System. The skin, the largest organ in our body, also removes excess salts and water through sweating or perspiration. Not forgetting the Lungs, which allows us to remove toxic Carbon Dioxide gas for the exchange of Oxygen. You should recall that the gas exchanges take place in the alveoli inside of the lungs. Once the blood has been filtered from the removal of urea and excess water by the Kidneys, these waste materials must be shipped and then stored in a container until disposal time has come. The part of the Kidney that does the actual filtering is called the Nephron. These are individual cells that are in the millions and they each perform a specific function: that is to filter and clean our blood. Inside the Nephron, you have two structures called the Bowman's Capsule and the Glomerulus. The Bowman's Capsule is where the actual filtration occurs. The Glomerulus is filled with capillaries which allow the blood to diffuse into the Bowman's capsule for filtration. Recall that the Kidneys also reabsorbs excess water: water absorption takes place in the Loop of Henle. The Loop of Henle absorbs excess water and makes the urine more concentrated. Once the blood is clean, it is returned to the heart. All that urea and excess water(urine) is sent to the Bladder via tubes called the Ureters. Once in the Bladder, the urethra is what then allows the urine to be exited towards the the outside world. Just as a reminder, all single celled organisms like the Ameba and Paramecium, perform Excretion by way of Diffusion directly through their cell membranes. THE NERVOUS SYSTEM: The nervous system allows us to respond or react to changes in our environment. That means that like all the other systems that we have been talking about, the nervous system allow us to maintain homeostasis. In order for us to respond to changes, we must first have a communication system that is quick and effective. For example, if you are crossing the street and you suddenly see a truck speeding towards you, your first impressions would be to speed up and get out of the truck.s way. Well, it is the nervous that allows us to do this. You might wonder how this happen so quickly. Well, first we pick up signals or messages from the environment using our five senses. Recall our Sensory organs are the skin, eyes, ears, tongue and nose. These organs allow us to pick up signals and send it to the Brain where these signals can then be analyzed. The signals get to the Brain via nerve cells called neurons. Once the Brain receives the information, it interprets the signals as emergency or fear etc. and then sends the message via the neuron once again to the Spinal Cord. Once in the Spinal Cord, the message is then sent to the muscle cells in the body so that we can now make the appropriate movement. As in the example above, our muscle cells will begin to contract allowing us to move quickly out of the truck.s way. Therefore as we have just seen, every sudden change or STIMULI in the environment can have an immediate and appropriate RESPONSE. This is how the Nervous System works and this is how we and other animals are able to maintain Homeostasis. The Brain and the Spinal cord make up the Central Nervous System (CNS). The sensory organs and other neurons make up what is called the Peripheral Nervous System (PNS). Our next System will be the Immune System which allow us to fight and protect ourselves from infections and harmful microbes or pathogens. THE IMMUNE SYSTEM: Antigens: Foreign Proteins that enter our bodies and trigger an immune response. White blood cells in our body does not recognize these proteins and therefore sees the proteins as a threat to our body. In response, the white blood cell attack and kill these proteins. Macrophages: These white blood cells attack and engulf pathogens. Pathogens are foreign cells or substances that enter our body. After eating up the pathogens, these white blood cells often die. T-cells: These are the specialized immune cells that attack specific pathogens and mark them for destruction. B-cells: These immune cells are the ones that make antibodies to make sure the pathogens don.t infect you the second time around. Antibodies are specific proteins that have specialized structure that can only allow them to recognize a specific ANTIGEN (pathogen). That means, only one type of antibody can recognize only one type of pathogen. These B-cells remains in the system as MEMORY cells, so that if the SAME pathogen do comes back, they will be ready to fight them off. Vaccines: Are a weakened form of a pathogen or antigen that is injected into a person.s blood stream. This allows the B-cells to then make the antibodies to that SPECIFIC antigen. The B-cells remain in your body as memory cells and if the pathogen enters the body at a later time, your immune system will be ready and waiting to fight it off. Types of vaccines are for the Flu, Measles, Mumps and Rubella and Chicken Pox. Problems of the Immune System: ALLERGIC REACTIONS: Sometimes the immune system causes problems rather than prevent them. This happens for a number of reasons. When the immune system over-reacts due to some antigen in the environment, it causes discomfort and sometimes pain throughout our bodies. These reactions are sometimes called allergic reactions caused by allergens found in the environment. Examples are pollen, animal fur, food and even insect bites. When you are allergic to something your body often tells you that something has gone wrong. Your body gives you messages like runny nose, sneezing, runny mucus, swelling and even teary eyes. The body does this in an attempt to get rid of the allergens. AUTO-IMMUNE DISEASES: This occur when your body sees and detects that your own body cells are foreign or pathogens. Just as when a bacteria enters your body, it triggers your white blood cells to go to work in attacking and destroying the pathogen. Well, in an auto-immune disease your own white blood cells think that your body cells are pathogens and they attack them. Cases like Rhematoid arthritis and Lupus are examples of auto-immune diseases, where the white blood cells of our immune system, attack and kill our own body cells. TRANSPLANTS: When we get Transplants like heart, lung and kidneys, our body also sees these organs as foreign and launch an attack against these transplanted organs. For the same reason as the auto-immune diseases, our white blood cells sees the transplanted organs as pathogens and they attack them. People with Transplanted organs are often given Immuno-Suppressants to lower the effects of the immune system. But this can lead to infections by other pathogens. A DAMAGED IMMUNE SYSTEM:Diseases like HIV destroys all of our T-cells leaving us open to other pathogenic microbes. People suffering from HIV often die from other diseases resulting from the poor and unresponsive immune system. As people get older, they are also more likely to be open to other diseases and illnesses. Your immune system tends to get weaker as you get older. Tumors and other forms of cancer also tend to be more prevalent in older people. THE MALE AND FEMALE REPRODUCTIVE SYSTEM: The male reproductive systems serves to produce sex cells called sperm and it also produces the hormone testosterone. Testosterone is responsible in making sure the sperm matures and also it causes the secondary sex characteristics in males to show: for example, deep voice, beard, muscular development and growth. It also serves to transport the sperm into the female reproductive system so that fertilization can occur. Sperm is made in the Testes, which are located in the outer sack called the Scrotum. The Scrotum allows the sperm to remain cool so that it cannot overheat and die. When the sperm is ready to come out, it travels from the testes to the outside world via a series of ducts. In order for the sperm to travel smoothly, it has to be coated with a liquid. This liquid is secreted by the prostate gland and the seminal glands. The liquid and the sperm together are called Semen. The semen is finally deposited into the female reproductive tract via the urethra and the penis. The Female Reproductive system serves to make eggs cells and female sex hormones like progesterone and estrogen. The female reproductive organ is called the Ovary. The ovaries produce egg cells and these egg cells are stored in a Follicle. Once a month a mature egg cell burst away from the follicle and begin its journey down the Fallopian tubes and towards the Uterus. This process is called Ovulation. If sperm is present, then fertilization of the egg as it moves towards the Uterus will occur. The fertilized egg will implant itself in the Uterus and here the Embryo will grow and develop until Birth. If fertilization does not take place, then the egg cell degenerates. The female sex hormones estrogen and progesterone allow the egg cells to mature and also promotes the secondary sex characteristics in the female such as breast development (mammary glands), and broadening of the pelvis area. These hormones are also responsible for the menstrual cycle and pregnancy in the females. FERTILIZATION AND THE MENSTRUAL CYCLE: Fertilization occurs when a sperm (male gamete) fuses with an egg (female gamete). The newly fertilized egg will then implant itself in the uterus via a maternal cord called the Placenta. The Placenta will provide all the nourishment and Oxygen for the developing Embryo. Waste materials produced by the Embryo will also be removed by the Placenta. We will talk more about the stages and what actually happens inside the Fertilized egg a t a later time. During Ovulation, when a mature egg gets released from the follicle in the Ovary, the wall of the uterus starts to build up in the event of getting ready to carry an embryo. The walls must be strong in order to hold and carry the embryo for a long period of time. Well the series of events that allows the uterus for pregnancy is called the Menstrual Cycle. The Menstrual Cycle begins at the onset of Puberty. This cycle is regulated by the female hormones Progesterone and Estrogen. The cycle has four stages: (a)Follicle Stage: when the egg matures in the follicle and the Ovary secrets estrogen. This Estrogen allows the walls of the uterus to thicken up. This lasts for about 14 days. (b)Ovulation: when the mature egg breaks free from the follicle in the Ovary and the egg enters the Fallopian tubes on its journey towards the Uterus. (c)Corpus Luteum: this forms as a result of the ruptures follicle and it secretes progesterone which further thickens the walls of the Uterus. This lasts for about 12 days. (d) Fertilization: If fertilization does not occur by this time (15 days), then the walls of the uterus starts to break down and the materials are passed out of the body through the vagina. The material contains tissue particles and blood that is a result of the lining that once was part of the Uterus. The process by which this material is being removed from the body is called Menstruation and it lasts for up to 4 days. Tomorrow we will learn about the Hormones that are involved in the Menstrual cycle. THE ENDOCRINE SYSTEM The Endocrine System is made up of various glands that release Hormones directly into the Blood. The Hormones are transported by the Circulatory System to all the organs and tissues for which these Hormones act upon. The glands of the Endocrine System are Hypothalamus, Pituitary in the Brain. The Thyroid located in the Chest cavity. The Adrenal gland located just above the Kidneys and finally the Gonads which include the Testes in the Male and the Ovaries in the Female. The Hypothalamus releases Hormones that directly causes the Pituitary Gland to release its own Hormones. The Pituitary gland releases hormones responsible for growth, Thyroid stimulating Hormone (TSH) that causes the Thyroid gland to release Thyroxin ( hormone that maintains the rate of metabolism in our bodies) and Follicle stimulating Hormone (FSH) that causes the Ovary and Testes to produce and release sex cells. The Adrenal glands secrete three types of Hormones. One allows fats and proteins to be converted to glucose causing an increased level of glucose in the blood. The other allows the kidneys to reabsorb salts back into the blood. The third releases the hormone called Adrenaline, which causes your heart and breathing rates to increase and it also increases the glucose level in the blood. The Pancreas also secretes two hormones called Insulin and Glucagon. Insulin regulates the glucose levels in your blood. If there is too much glucose in the blood, it converts glucose to Glycogen. Glucagon increases the blood glucose levels and if there.s too little glucose in the blood, it converts glycogen to glucose. These two hormones work together in a feedback mechanism to maintain the correct levels of glucose in the blood. The Gonads also releases hormones. The male testes release Testosterone and the female Ovary release Estrogen and Progesterone, which allows the Uterus to thicken up in the event of a Pregnancy. THE NEGATIVE FEEDBACK MECHANISM The negative feedback loop works in such a way so that there will be a balance of hormones in the body. For example, if you ate a lot of sugar for breakfast, your blood glucose level will tend to increase dramatically just after eating. The way your body regulates or controls this burst of sugar RUSH is by the Pancreas releasing the hormones Insulin. Recall that Insulin regulates or coontrols the blood glucose level. The insulin then will convert the excess glucose into the storage form known as glycogen. Now, lets say that the blood glucose level is back to normal. Do you think that the Pancreas will still be releasing Insulin? Well you are right!! The answer is NO NO NO NO NO. The fact that Insulin will no longer be released by the Pancreas, is called the Negative Feedback Loop. This mechanism ensures that hormones get released by the Organs only when needed. It allows us to maintain Homeostasis by regulating and controlling the production and release of hormones. THE SKELETAL AND MUSCLE SYSTEM The Muscle and Skeletal system is what allow us to move. This movement is sometimes called locomotion. Locomotion involves the usage of bones, muscles, tendons, cartilage and ligaments. Bones provide support and protection for the body. Red and white blood cells are also made in the bone marrow. Cartilage is a type of flexible and soft connective tissue that is found in areas such as the nose and ears. Also your throat is made up of cartilage. Cartilage keeps our body cushioned and when babies are born, all the cartilage is replaced by bones as they get older. Joints are places where bones are connected to each other. This also allows us to make movements and other flexes as we move. Muscles allow us to make body movements. They are connected to all of our bones in the skeletal system. Muscles are what control the movement of our bones. There are three types of muscles in our body: Skeletal muscle, Cardiac muscle and Smooth muscle. Skeletal muscles are muscles that are activated Voluntarily. For example if you want to pick up a book from the floor, you will use muscles that you can control. Notice that the contraction of skeletal muscle is controlled by the Nervous system. Smooth or Visceral muscle are muscle that cannot be controlled by you. Therefore they are called Involuntary muscles. These muscles can be found in the lining of you stomach and arteries. Cardiac muscle can be found only in the heart and like the smooth muscle you also cannot control this type of muscle movement. Muscles are attached to bones by inelastic fibrous cords called tendons. There are a few disorders associated with locomotion. These are Arthritis and Tendonitis. These disorders come about by a type of inflammation that is more common in athletes. This is the last of all the systems that we will learn. Now that we are done with the systems and Homeostasis, our nest Topic of business is Photosysthesis: The process where by plants make their own food. That is, photosynthesis is a chemical process where plants use light, carbon dioxide and water to make energy (food) for their survival PHOTOSYNTHESIS: All organisms need energy to survive. Animals get their energy from the organic substances found in the food they eat. Animals must also look for their food if they have to stay alive. Since all animals must have to look for their food source, they are called Heterotrophs. Plants on the other hand are immobile and really cannot move around and search for food. They must have to then make their own food in order to stay alive. Organisms that can make their own food are called Autotrophs. Plants use Carbon Dioxide and water along with light energy to make Oxygen and Glucose in a process called Photosynthesis. You may be asking yourself how does the plant or tree do this? Well, this process only takes place in the leaves of these plant and trees. Inside the leaf, there is a green pigment called chlorophyll which captures and transfers light energy from the sun, florescent lights at home etc. into a chemical energy (glucose). Chlorophyll is located inside the leaf in a contained sack called the chloroplasts. There are a lot of chloroplasts in a leaf. Why do you think that a lot of Chloroplasts are needed inside the leaf? The Oxygen that is made by Photosynthesis is released into the air for other organisms like animals to use. The Glucose that is made is used as a source of energy for the plant. The plant used this energy to grow, repair old and broken parts and also for reproducing. The glucose that is left over is stored in a form called starch. Parts and Function of the Leaf: How is the Leaf adapted for Photosynthesis: The flat and thin surface area of most leaves provides maximum absorption of light for photosynthesis. The outermost part is called the Epidermis- this layer protects and prevent the loss of water. The Stomates are tiny openings in the leaf that the exchange of Carbon dioxide, Oxygen and water vapor. The stomates are surrounded by cells called Guard cells.which controls the opening and closing of the stomates. The Palisade layer is the layer that contains the chloroplasts. Here is where the actual photosynthesis takes place. The spongy layer which is located directly below the palisade layer allow air to diffuse from the stomates and into the cells of the plant. The spongy layer also contain some chloroplasts, which tells that some photosynthesis occurs here as well. The veins of the leaf allow for transport of nutrients and water from the leaf to the roots and back. They carry all materials to all parts of the plant. HOMEOSTASIS: As mentioned earlier when we learned about the human systems, homeostais plays a crucial role in maintaining a normal internal environment. If organisms do not maintain this stability, they can become sick and even die. For example, when humans run, our body temperature usually increases to over 100 degrees. However, because we sweat, our body is cooled and this prevents our organs and other internal tissues from burning up. So, by sweating when the body temperature increases, we are always able to maintain homeostasis. Another example is when we eat a large candy or something that contains a lot of starch and glucose. This large sugar rush causes an increase in the blood sugar level in our body. This can cause us to get sick if not resolved quickly. In order to maintai an stable internal environment, our Pancreas releases insulin so that the blood sugar level can come back to normal. Keep in mind that all living things must have to respond to changes in their internal environment and Homeostasis allows this to happen. LIGHT AND DARK REACTIONS OF PHOTOSYNTHESIS: Photosynthesis occurs in the chloroplasts of all plant cells. Inside the chloroplasts are the chlorophyll that are packed into structures called the Thylakoid. The space that surrounds the Thylakoid inside the chloroplast is called the stroma. The Light reaction of Photosynthesis occurs in the Thylakoid. Here the product of this reaction is Oxygen. The dark reaction, also called the Calvin cycle, occurs in the stroma. The product of the dark reaction is high energy sugars or glucose. Remember that plants store their glucose molecules in the form of starch. Make sure to look in the textbook to further your understanding of Photosynthesis. CLASSIFICATION OF LIVING THINGS To avoid confusion among living things, scientists have developed a naming procedure so that we can name organisms without being misled. The process of naming these organisms by the way they look and live is called classification. Naming organisms usually comes with two scientific names. These names are called the Genus and the species. The first letter of the first word is always capitalized and the first letter of the second word is always lowercase. For example, us human do to have a scientific identity: Homo sapiens. We are from the Genus Homo and of the species, sapiens. Almost every living thing on earth has this type of scientific nomenclature. Plants and animals are named scientifically so that we cannot mix up their identities. CELLULAR RESPIRATION: We learned a few weeks ago that respiration involved the exchange of gases between living organisms and their environment. For example, humans breathe in Oxygen and release Carbon Dioxide in the process. Well, their is also another type of Respiration called Cellular Respiration. Cellular Respiration is the process where cells break down glucose to make energy. Recall that all living things require energy to perform all life functions. We learned a few weeks ago that respiration involved the exchange of gases between living organisms and their environment. For example, humans breathe in Oxygen and release Carbon Dioxide in the process. Well, their is also another type of Respiration called Cellular Respiration. Cellular Respiration is the process where cells break down glucose to make energy. Recall that all living things require energy to perform all life functions. Cellular respiration takes place in the Mitochondria of living things. The Mitochrondria also called the Power house of the cell, break down glucose to yeild energy in the form of ATP. ATP is the energy form that the cell uses The same way humans use MONEY to buy everything that they want, ATP is what the cell uses to perform all the functions in the body. At the end of one round of Respiration, you have a total of 36 ATP being made. This ATP is divided into 2 separate parts. The first part is a result of Glycolysis. Glycolysis is the breakdown of one glucose molecule to produce 2 ATP molecules. The remainder of the ATP's come from the Kreb cycle in the Mitochondria. Here in the Mitochondria, 34 more ATPs are made in the presence of Oxygen. Since Oxygen is needed for this production of ATP, this type of Respiration is called Aerobic Respiration. When Oxygen is not needed, it is called Anaerobic Respiration. Organism like the yeast uses a process of Anaerobic Respiration to make their ATPs. ENZYMES: All chemical reactions that occur in living things require the use of Enzymes. Enzymes are proteins that perform a specific function in all living things. Enzymes speed up the rate of a reaction. For example, when you eat potato chips, the enzymes that are present in your mouth causes the potato chips to be digested at a faster rate. That allows the nutrients in food to be delivered to our body cells much more faster. If enzymes were not present, the potato chips would be broken down by your teeth only and the nutrients from food would not be delivered to your cells in time. Because enzymes increases the rate of a reaction (example digestion), enzymes are also called Catalysts. Please remember that enzymes do not loose their shape or their figure. They just help out in the reaction processes, so that it occurs much faster. For every enzyme in our body, you have a specific molecule for which that enzyme acts on. For example, the enzyme called Pepsin only acts on Proteins in the stomach. They do not act on other foods like fats or carbohydrates. Because Pepsin can act only on Proteins, this protein is called a Substrate. Substrates are molecules that enzymes bind to. THE LOCK AND KEY MODEL FOR ENZYMES: Enzymes react with its substrates in a specific manner. First the enzyme recognizes and binds to a specific site on the substrate. Usually this site is called the active site and is often represented by shapes or colors. When the enzyme binds the substrate at the active site, then the reaction occurs. If the enzyme is a digestive enzyme like pepsin, then the digestion of the protein substrate will occur. As mentioned above, this reaction will occur faster if more and more of the same enzyme is present. FACTORS AFFECTING ENZYME REACTION: There are four factors that affect the rates of an enzyme: Temperature: The higher the temperature the faster the enzyme tends to work in some organisms. Therefore the reaction time would be faster. However, if the temperature raises beyond the temperature at which the enzyme can function, it will destroy the enzyme and the reaction will not occur. It is always best to first know the optimal temperature for which an enzyme works best. Enzyme Concentration: If you have a lot of the same enzyme attacking one substrate, then the rate of the reaction will increase. If all the substrate gets used up, then the reaction will stop. Substrate Concentration: The same rule applies as above. If you have a lot of substrate with a good amount of enzymes, you will have a fast reaction. The reaction will stop when the substrate gets used up. Recall that the enzyme will never be destroyed or used up, they just make the reaction go faster. pH: Certain enzymes work better at different pH. For example, Pepsin works best if its in the stomach where the pH is very acidic. If Pepsin was place in an environment where the pH was not acidic, then the enzyme would be destroyed and the reaction will not take place, no matter what!! Other enzymes work best when they are placed in high pH. Can you think of an enzyme that works well in a high pH environment? |