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3.4: Very Basic Features of Life - Biology

3.4: Very Basic Features of Life - Biology


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There are two basic features of all Earth life (and we do not actually know any other Life):

  1. Semi-permeable membranes:

    Most of living cells surrounded by oily cover which consists of two layers made of lipids and embedded there proteins. These membranes allow some molecules (e.g., gases or lipids) to go through, but most molecules only enter “with permission”, under the tight control of membrane proteins.

  2. DNA ( ightarrow) RNA ( ightarrow) proteins:

    That sequence is called transcription (first arrow) and translation (second arrow). DNA stores information in form of nucleotide sequence, then fragments of DNA are copying into RNA (transcription). RNA, in turn, controls protein synthesis (translation). This is sometimes called the “central dogma of molecular biology”.


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Unit Sequence of Lesson Plans:

Students would have looked at the basic needs of living creatures in previous years of study, they will understand the features of living things and that they need to grow. The life cycles of living things would also have been examined earlier in this year level.

  • Understand that living things rely on certain other living things and the environment around them to survive.
  • Identify the conditions that living things need for survival.
  • Computers – with internet for students to complete online activity
  • Interactive Whiteboard – with internet (YouTube video)
  • Paper handouts (in case of technological issues)

Environment:

Students will need to have clear view of the IWB and whiteboard. Students will need to be close enough to the teacher and each to share ideas. Computers – laptops or computer room will be needed for the body of the lesson.

Introduction/Motivation (15 mins)

  • Start the lesson by viewing the video ‘What animals need to survive’ on YouTube. This will revisit some of the concepts learnt in previous years and uses specific examples which will prompt some questions.

  • Ask students about what animals may work together to survive and in what ways animals can also use each other to survive.
  • Write some answers on the whiteboard. Relate information to the answers they give and expand if possible.
  • Explain that animals sometimes use each other as a means of survival and that a food chain exists within the animal kingdom.
  • Ask questions to engage students as well as finding out understanding.
  • Students can then be directed to computers where they will complete an online activity on the food chain via http://www.tesaustralia.com/ResourceDetail.aspx?storyCode=6018715&
  • This quiz will test the knowledge of the students and give them a deeper understanding of food chains that exist between animals.
  • Allow students time to complete the quiz. (In case of any technological issues a printable sheet will be on hand for students to complete should the online form be unavailable).

Students will then come back together. Ask students what they found interesting about the topic.

Lesson Plan 2/3: Sustainability and Environmental Factors

Rationale/Goals:

This lesson will look at the environment and the way that it can impact on the survival of living things. We shall look at the way that we as humans can help in the sustainability of the environment for the protection of all living creatures.

Prior Knowledge and Experience

Students would have looked at the basic needs of living creatures in previous years of study, they will understand the features of living things and that they need to grow. The life cycles of living things would also have been examined earlier in this year level.

  • To understand the role the environment plays in the survival of living things
  • To understand the human impact on living things
  • To develop thoughts on what can be done to help our environment and protect living things.
  • Whiteboard
  • Pens, Pencils, Paper
  • Pictures of animals in the environment (displayed at the front of the room)

Environment:

Working in the classroom every student will need access to the whiteboard to see group answer as well as the opportunity to give their opinions. The classroom will need to be quiet for some parts of the lesson for work.

Introduction/Motivation:

  • Explain that along with animals needing each other to survive that the environment can play a large role in the growth and survival of animals and that for a sustainable future (give a quick definition of sustainability) for living things we need to be mindful of our actions in the environment.
  • Again we shall then move onto a brainstorming activity where we will discuss and write down on the whiteboard some of the things that can environmentally impact on the survival of living things.
  • Discuss the different impacts different events can have on certain living things. For example. Oil spill effects marine life, drought can affect farm animals etc.
  • Now on a separate sheet ask students how they think they can care for the environment in the long term future. What can they do individually and what can we do as humans to help?
  • Once the initial brainstorming is complete send the students back to their tables have them rank the order they think each one of the things we can do to help is.
  • Explain that they need to think and justify why they rate one above another.
  • The prompt question for this activity “What are the most important things we can do for our environment and living things sustainability?”
  • Allow the student’s time to think and during this time talking should be at a minimal level as this is an individual piece of work where solo thinking is involved. There are no right or wrong answers in this piece. Very Open ended.
  • Conduct a poll to survey the students on what they saw as the most important things that can be done.
  • Remind students that there are no right or wrong answers and that science is about justifying your answer.
  • Ask students to justify their answer explaining why they think a particular action would/wouldn’t help the most.

The third lesson in the unit will tie the first two together where both food chains and environment are looked at in a real life situation.

  • 1 Anecdotal note for each student on the following question:
    • Did students come out of the lesson with the knowledge to help them help the environment in a sustainable manner?

    Lesson Plan 3/3: Outside Investigations

    Rationale/Goals:

    This lesson will link to classes together as well as having two teachers work together as students are divided into two groups to conduct hands on field work before bringing their work back to the class to discuss their findings.

    Prior Knowledge and Experience:

    Students would have looked at the basic needs of living creatures in previous years of study, they will understand the features of living things and that they need to grow. The life cycles of living things would also have been examined earlier in this year level.

    As well as this the previous two lesson (completed within the previous week will lay the platform to be able to put their learning into practical sense.

    • For students to understand the environment and the way animals need to survive using each other and the habitat around them.
    • Cameras (computers for printing pictures)
    • Pens and Paper for recording data
    • Students may need other resources at the time that can be arrange within reason

    Environment:

    This lesson will be conducted mainly outdoors. If wet weather is imminent, a time change of the lesson may be required.

    Introduction/Motivation:

    Students from two classes will come together and then will be divided into two groups. Each class will go with one teacher and set off on a different ‘field trip’ around the school.

    Group One – Will take cameras (ICT) and go on a walk depending on the school environment within the school or to a local park where they will collect data (and take photos) of the local animals that exist within the area.

    These photos will then be used back in the classroom to create a visual food chain web.

    Group Two – Will also venture to a local park or area of habitat and conduct a metre box audit whereby they will examine the animals and the environment that are within it. They will then extrapolate the numbers for the size of the park and determine if it could support larger animals.

    Ensure all students are giving a chance to participate in the activity.

    The two groups will then come together and each group will explain their findings to each other. This part of the lesson should be conducted by the students. Peer teaching is a great way of helping students learn.

    • Peer assessment – Students leading the lesson is a way looking at the work that they put together.

    After this final lesson questions can be asked to gain information on their understandings and future work can also follow up on this, including looking at a specific living thing and compiling a report on it – students could do this individually or in groups.

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    If you like this lesson plan, or have an idea to improve it, please consider sharing it on Twitter, Pinterest and Facebook or leave a comment below.


    Main features of the autobiography

    The autobiography must cover certain points

    You can include all the information that is considered important. It has to be personal, including essential information such as name, age, date of birth, place of residence, etc.

    Within the personal information that is included it should be mentioned to the family that you have, the brothers and sisters, the people that mark the important things in your life.

    In addition it should include the academic information that the author has received, place of studies, the achievements and prizes received.

    It is a non-fiction writing

    The autobiographical pact is established between the author and the reader, where everything that is related is true.

    The writer in this work has absolute freedom in which he expresses his ideas or feelings about the events and how they influenced him.

    It relates the life of the author

    It can be considered a totally intimate confession in which the author narrates his most personal secrets.

    It analyzes all the facts that happened during a life, and in many cases to put them in perspective of what it has lived.

    The autobiography is characterized by the fact that the author, who is also a narrator, is at the same time the protagonist of the stories that are narrated. The writer is the center of the work as he is telling his own story.

    Without fixed structure

    The autobiography is characterized by not having a fixed structure. Each writer chooses his own structure, does not need to follow a chronological order to narrate the facts happened.

    Formal or informal language

    In the autobiography the writer can choose the language he wants to use. You can choose the type of language that best suits you to express yourself and tell your life.

    Tone

    You can choose the tone in which to write the biography:

    • It can be a melodramatic tone where the events that happen to the author are unfortunate.
    • A humorous tone where the story is presented from a laughing or comical point of view.
    • An ironic tone, where an idea is expressed by saying the opposite, but so that the reader understands that it is an irony.
    • Sarcastic tone, where the narrations reflect a lack of respect, where sarcasm is a cruel mockery.
    • Heroic tone where the author has a strong personality and emerges from the dangers that arise.
    • Nostalgic tone where pleasant experiences are evoked and remembered with a lost happiness.

    Focuses on life

    The autobiography is used to tell and narrate the whole life of the author. Unlike memories that focus more on a particular stage or event.

    For this reason the autobiography is more complete, since it is not located in a limited period of time.

    It is not a fixed rule, the author does not always remember all the moments of his life, in addition he can choose which to include in his work or not.

    Draw conclusions and learnings

    The autobiographies serve to draw conclusions from the lives of the people, they serve as an exercise of interiorization where they discover all the way that they have followed until arriving at the place where they are.


    Interactive resources for schools

    Macromolecules

    Very large molecules, often formed by the polymerisation of smaller subunits

    Protein

    A polymer made up of amino acids joined by peptide bonds. The amino acids present and the order in which they occur vary from one protein to another.

    Glossary

    A list of often difficult or specialised words with their definitions.

    Melanin

    Dark brown or black pigment found in the skin, hair and irises of the eyes. The skin produces more melanin when exposed to the sun.

    Lipid

    Molecules which contain a lot of stored energy built up of fatty acids and glycerol. Lipids include oils and fats

    Albino

    A person with little or no pigment in the eyes, skin and hair. They have inherited an altered copy of a gene that does not work properly and so the body does not make the usual amounts of melanin.

    The basic unit from which all living organisms are built up, consisting of a cell membrane surrounding cytoplasm and a nucleus.

    Charge particles formed when an atom loses or gains electrons during the formation of ionic bonds

    Deoxyribonucleic acid. This is the molecule which contains the genetic code. It coils up tightly inside chromosomes. DNA is a double helix made from two strands which are joined together by pairs of bases.

    Adenosine triphosphate

    Molecule which acts as the common energy currency in all cells, providing the energy needed to drive chemical reactions in cells.

    The importance of chemistry in biology

    Why does your skin wrinkle as you get older? If you have osteogenesis imperfecta, why do your bones break so easily? Why do albino rabbits have pink eyes? The answer to all of these questions, at the most basic level, is chemistry!

    Biology is the study of living things. The key to understanding biology is to understand the fundamental chemistry which underpins all life.

    In young skin collagen molecules form elastic triple helices which stretch as the skin moves. With age, the molecular structure changes to become more rigid, brittle and more likely to tear. When collagen combines with bone it gives it tensile strength, like reinforced concrete. In osteogenesis imperfecta, the collagen and bone don’t combine so the bone is brittle and breaks easily. And an albino rabbit lacks one single molecule called melanin.

    The chemistry of life begins with the basic principles of bond formation and bond breaking, and the nature of the different compounds formed. Life revolves around the balancing act between the energy released as bonds are broken and the energy taken in as bonds are formed.

    Life on earth depends on the nature of the carbon atom and the nature of water. Water is fundamental to life and understanding the properties of water helps to make sense of many other areas of biology.

    Whilst many small molecules and ions play vital roles in cells and organisms, macromolecules are also key. An understanding of the chemistry of compounds including carbohydrates, proteins, lipids, ATP, DNA and RNA gives you the tools you need to make sense of everything from cell biology to ecology.

    Each organism is a collection of carefully controlled chemical reactions

    Photos by Anthony Short unless credited otherwise. Animations and diagrams by Edward Fullick throughout.


    Vaccines need T cell help

    Although most of the evidence points to antibodies being the key mediators of sterilizing immunity induced by vaccination, most vaccines also induce T cell responses. The role of T cells in protection is poorly characterized, except for their role in providing help for B cell development and antibody production in lymph nodes. From studies of individuals with inherited or acquired immunodeficiency, it is clear that whereas antibody deficiency increases susceptibility to acquisition of infection, T cell deficiency results in failure to control a pathogen after infection. For example, T cell deficiency results in uncontrolled and fatal varicella zoster virus infection, whereas individuals with antibody deficiency readily develop infection but recover in the same way as immunocompetent individuals. The relative suppression of T cell responses that occurs at the end of pregnancy increases the severity of infection with influenza and varicella zoster viruses 39 .

    Although evidence for the involvement of T cells in vaccine-induced protection is limited, this is likely owing, in part, to difficulties in accessing T cells to study as only the blood is easily accessible, whereas many T cells are resident in tissues such as lymph nodes. Furthermore, we do not yet fully understand which types of T cell should be measured. Traditionally, T cells have been categorized as either cytotoxic (killer) T cells or helper T cells. Subtypes of T helper cells (TH cells) can be distinguished by their profiles of cytokine production. T helper 1 (TH1) cells and TH2 cells are mainly important for establishing cellular immunity and humoral immunity, respectively, although TH1 cells are also associated with generation of the IgG antibody subclasses IgG1 and IgG3. Other TH cell subtypes include TH17 cells (which are important for immunity at mucosal surfaces such as the gut and lung) and T follicular helper cells (located in secondary lymphoid organs, which are important for the generation of high-affinity antibodies (Fig. 3)). Studies show that sterilizing immunity against carriage of S. pneumoniae in mice can be achieved by the transfer of T cells from donor mice exposed to S. pneumoniae 40 , which indicates that further investigation of T cell-mediated immunity is warranted to better understand the nature of T cell responses that could be harnessed to improve protective immunity.

    Although somewhat simplistic, the evidence therefore indicates that antibodies have the major role in prevention of infection (supported by TH cells), whereas cytotoxic T cells are required to control and clear established infection.


    Matriculation Biology

    Amran Md Said
    Matriculation College of Pahang

    Molecus of life

    TOPIC 1 : MOLECULES OF LIFE

    Amran Md Said
    Matriculation College of Pahang

    1.1 Water
    1.2 Carbohydrates
    1.3 Lipids
    1.4 Protein
    1.5 Nucleic acids

    At the end of this topic, students should be able to:

    • explain the structure of water molecule
    • describe the properties of water and its importance
    • A water molecule consist of an oxygen atom and two hydrogen atom
    • The two hydrogen atoms are combined with the oxygen atom by sharing of electrons
    • The three atoms form a triangle, not a straight line
    • The water molecule is electrically neutral but there is a net negative charge on the oxygen atom and a net positive charge on both hydrogen atoms.
    • A molecule carrying such an unequal distribution of electrical charge is called a polar molecule.
    • The positively charged hydrogen atoms of one water molecule are attracted to the negatively charged oxygen atoms of nearby water molecules by forces called hydrogen bonds.
    • Hydrogen bonds largely account for the unique properties of water. weaker than covalent bonds.
    • But -> strong enough to hold water molecules together.
    • Because of their hydrogen bonds, water molecules are attracted to charged particles or charged surfaces.
    • powerful solvent for polar substances
    • These include ionic substances like sodium chloride (Na+ and Cl-), and also organic molecules with ionized
    • These cations (negatively charged ions) and anions (positively charged ions) become surrounded by a shell of orientated water molecules.
    • This makes them more reactive chemically than when they form part of an undissolve solid.
    • At the same time, non-polar substances are repelled by water, as in the case of oil on the surface of water. Non-polar substances are hydrophobic.
    • This unique property makes it suitable medium of transportation in living organisms.
    • Helps in movement of food substances
    • It also can act as a lubricants in joints
    • A lot of energy is required to raise the temperature of water.
    • Because, much energy is needed to break the hydrogen bonds .
    • The head capacity of water is the amount of head required to raise the temperature of 1g of water by 1oC per calorie (cal) or 1 cal/g of water per oC
    • This property of water is known as its high specific heat capacity.
    • The specific heat capacity of water is the highest of any known substance.
    • Aquatic environments like stream , lakes and seas are all very slow to change temperature when the surrounding air temperature changes.
    • When pure water is heated to 100oC, it boils
    • The water molecules gain sufficient kinetic energy to escape into the air as water vapor
    • The heat energy that is being used to produce this change is called the latent heat of vaporization
    • Water has a high latent heat of vaporization
    • Because → the hydrogen bonds between water molecules make it difficult for them to be separated and vaporized
    • This means that much energy is needed to turn liquid water into water vapor.
    • The amount of heat energy needed to melt ice is very high and the amount of heat that must be removed from water to turn into ice is also great.
    • Many living organism use this feature of water as cooling mechanism.
    • For example, human sweat → the liquid water in sweat absorbs heat energy from the skin or in transpiration from green leaves → to stop the leaves’ temperature from rising too high on a hot day
    • Most liquids contract on cooling, reaching their maximum density at their freezing point.
    • Water is unusually reaching its maximum density at 4ºC.
    • As water freezes, the ice formed is less dense than the cold water around it. The ice floats on top.
    • The floating layer of ice insulates the water below.
    • This is why the bulk of ponds, lakes or the sea rarely freeze solid.
    • Aquatic life can generally survive a freeze-up.
    • Water adheres strongly to most surfaces
    • It can be drown up into long columns through narrow tubes like the xylem vessels of plant stems, without the water column breaking.
    • Compared with other liquids, water has extremely strong adhesive and cohesive properties that prevent the column breaking under tension.
    • The outermost molecules of water form hydrogen bonds with water molecules below them.
    • This gives a very high surface tension to water- higher than that of any other liquid except mercury. Surface skate.
    • The insect’s waxy cuticle prevents wetting of its body, and the mass of the insect is not great enough to break through the surface.

    At the end of the lesson, student should be able to explain:

    1. Describe various forms and classes
    2. Describe the formation and breakdown of maltose
    3. Structures and functions of starch, glycogen and cellulose.

    • Organic molecule containing the element carbon, hydrogen and oxygen in a 1:2:1 ratio
    • Written as (CH2O)n n = number of carbon
    • Source of energy
    • Storage of energy
    • Structural component of cell membranes and cell walls
    • Carbohydrates can be classified into three classes:

    MONOSACCHARIDES

    1. Small
    2. White
    3. Sweet
    4. Soluble
    5. Can be crystallized

    1. reducing Benedict test
    2. condensation reaction to form disaccharide or polysaccharide

    • Greek words, monos = simple sacchar = sugar, generally have molecular formula that are some multiple of CH 2 O --> (CH 2 O)n For example, glucose has the formula C 6 H 12 O 6 .
    • Most names for sugars end in -ose.
    • basic unit or monomer
    • It can be classified by two ways :

    Classification by the number of carbon in the backbone

    • Three carbon (3C) – triose sugars . Example : glyseraldehyde and dihydroxyaceton
    • Five carbon (5C) – pentose sugars. Example : ribose and ribulose
    • Six carbon (6) – hexose sugars Example : glucose and fructose

    Importance as synthesis of nucleic acid (RNA and DNA)


    Ring Structure for hexose

    Importance as source of energy in cell respiration


    Classification by the functional group

    • Aldehyde group – glyseraldehyde, ribose and glucose
    • Ketone group – dihydroxyaceton, ribulose and fructose
    • Differences between aldehyde and ketone group
    • All sugar contain the C = O. This is called a carbonyl group
    • The monosaccharides which have a aldehyde group is called aldose sugar
    • The monosaccharides which have ketone group is called ketose sugar

    If the location of carbonyl group is in the middle backbone of the corbon, it call ketose

    • Aldehydes are reducing agents.
    • So aldose sugar have reducing agents, and are called reducing sugar.
    • Ketose sugars do not have reducing agents, but in monosaccride form, it react as reducing agents because hydroxyl in functional group have free.
    • Benedict’s reagent contains copper (II) ions, which give a blue colour to the Benedict’s solution.
    • When heated with a reducing sugar, the copper (II) ions are reduced to copper (I) ions, and an orange-red precipitate of copper (I) oxide is formed:
    • Isomer = molecules which have same chemical formula but with different structure
    • Example : glucose and fructose → C 6 H 12 O 6
    • Example : α - glucose and β - glucose
    • With six carbon atoms numbered.
    • At Carbon 1 ,

    DISACCHARIDES

    • Disaccharides are formed when two monosaccharide joined together
    • Physic characteristic
    • Chemistry characteristic
    • A monosaccharide able joined together to form it by a condensation reaction.
    • By hydrolysis reaction to form monosaccharide.
    • Types of Disaccharide

    Formation of disaccharide

    • The two monosaccharide joined together by a condensation reactions in which water is removed
    • The bond formed between two monosaccharide as a result of condensation is called glycosidic bond
    • A glycosidic bond can also be broken down to release separate monomer units. This is called hydrolysis because water is needed to split up the bigger molecule
    • Maltose, malt sugar → α glucose + α glucose
    • Sucrose, table sugar → α glucose + α fructose .
    • Lactose, milk sugar → glucose + galactose
    • Milk sugar, is found exclusively in milk and is an important energy source for young mammals
    • It can only be digested slowly, so gives a slow steady release of energy.
    • Lactose = glucose + galactose
    • All monosaccharides and some disaccharide (maltose and lactose) are type of chemical reaction knows as reduction.
    • Sucrose (non reducing sugar) and polysaccharide can’t reducing Benedict test.
    • Reducing sugar : maltose
    • Non reducing sugar : sucrose
    • Are formed when many hundreds of monosaccharides condense (join) to form chains.
    • The chains formed may be:

    Characteristic of polysaccharides:

    - large,
    - not sweet
    - Insoluble in water

    • Polysaccharides are polymers of hundreds to thousands of monosaccharides joined by glycosidic linkages.
    • Function → is as an energy storage macromolecule that is hydrolyzed as needed.
    • Others → serve as building materials for the cell or whole organism.
    • Starch is a storage polysaccharide in plants.
    • monomers are joined by 1-4 linkages between the α glucose, known as α-1,4 glycosidic bond .
    • unbranched form of starch → amylose → forms a helix.
    • Branched forms → amylopectin.
    • Made from α-glucose molecules
    • Forming unbranched helical chain of 300 units in length.
    • Each α-glucose is joined by a glycosidic bond between neighbouring C1 and C4 atoms.
    • Made from α-glucose molecules
    • Forming branched chains of up to 1500 units
    • Branches occur every 30 units and are formed between neighbouring C1 and C6 atoms which are then held together by glycosidic bond.
    • Animals also store glucose in a polysaccharide called glycogen.
    • Glycogen is highly branched, like amylopectin.
    • Found in liver and muscle tissue and made up of short branched chains of α-glucose units.

    Major component of the tough wall of plant cells.

    Long chains of β-glucose units which are unbranched

    but parallel strands of cellulose are linked by means of hydrogen bonds, making the cell wall a very stable structure.

    The enzymes that digest starch cannot hydrolyze the beta linkages in cellulose.

    Cellulose in our food passes through the digestive tract and is eliminated in feces as “insoluble fiber”.

    As it travels through the digestive tract, it abrades the intestinal walls and stimulates the secretion of mucus.

    Some microbes can digest cellulose to its glucose monomers through the use of cellulase enzymes.

    Herbivores, like cows , have symbiotic relationships with cellulolytic microbes, allowing them access to this rich source of energy.

    Cows do have enzymes → amylases, which can break β - 1,4 glicosidic bonds in starch but which cannot recognize β - 1,4 glicosidic bonds in cellulose,

    the bacteria in the rumen do produce enzymes called cellulles which can recognize and break β - 1,4 glicosidic bonds in cellulose


    3.4: Very Basic Features of Life - Biology

    Insect Biology and Ecology: A Primer

    For the reader who is unfamiliar with the biology or ecology of insects, this primer will provide needed background information.

    This segment is comprised of several paragraphs of general insect information and five subsections:

    Insects are the dominant life-form on earth. Millions may exist in a single acre of land. About one million species have been described, and there may be as many as ten times that many yet to be identified. Of all creatures on earth, insects are the main consumers of plants. They also play a major role in the breakdown of plant and animal material and constitute a major food source for many other animals.

    Insects are extraordinarily adaptable creatures, having evolved to live successfully in most environments on earth, including deserts and the Antarctic. The only place where insects are not commonly found is the oceans. If they are not physically equipped to live in a stressful environment, insects have adopted behaviors to avoid such stresses. Insects possess an amazing diversity in size, form, and behavior.

    It is believed that insects are so successful because they have a protective shell or exoskeleton, they are small, and they can fly. Their small size and ability to fly permits escape from enemies and dispersal to new environments. Because they are small they require only small amounts of food and can exist in very small niches or spaces. In addition, insects can produce large numbers of offspring relatively quickly. Insect populations also possess considerable genetic diversity and a great potential for adaptation to different or changing environments. This makes them an especially formidable pest of crops, able to adapt to new plant varieties as they are developed or rapidly becoming resistant to insecticides.

    Insects are directly beneficial to humans by producing honey, silk, wax, and other products. Indirectly, they are important as pollinators of crops, natural enemies of pests, scavengers, and food for other creatures. At the same time, insects are major pests of humans and domesticated animals because they destroy crops and vector diseases. In reality, less than one percent of insect species are pests, and only a few hundred of these are consistently a problem. In the context of agriculture, an insect is a pest if its presence or damage results in an economically important loss.

    The adage "know your enemy" is especially appropriate when it comes to insect pests. The more we know about their biology and behavior, including their natural enemies, the more likely we will be able to manage them effectively.

    Insects and closely related organisms have a lightweight, but strong exterior skeleton (exoskeleton) or integument. Their muscles and organs are on the inside. This multi-layered exoskeleton protects the insect from the environment and natural enemies. The exoskeleton also has many sense organs for detecting light, pressure, sound, temperature, wind, and odor. Sense organs may be located almost anywhere on the insect body, not just on the head.

    Insects have three body regions: head, thorax, and abdomen. The head functions mainly for food and sensory intake and information processing. Insect mouthparts have evolved for chewing (beetles, caterpillars), piercing-sucking (aphids, bugs), sponging (flies), siphoning (moths), rasping-sucking (thrips), cutting-sponging (biting flies), and chewing-lapping (wasps). The thorax provides structural support for the legs (three pairs) and, if present, for one or two pairs of wings. The legs may be adapted for running, grasping, digging, or swimming. The abdomen functions in digestion and reproduction.

    The internal anatomy of insects is characterized by an open circulatory system, a multitude of breathing tubes, and a three-chambered digestive system. With the exception of a heart and an aorta, there are few blood vessels insect blood simply flows around inside the body cavity. Air enters the insect through a few openings (spiracles) in the exoskeleton, and makes its way to all areas of need by way of branching tubes, which permeate the body. The insect digestive system is long and tube-like, often divided into three sections, each with a different function. The insect nervous system transports and processes information received from the sense organs (sight, smell, taste, hearing, and touch). The brain, located in the head, processes information, but some information is also processed at nerve centers elsewhere in the body.

    Knowledge about the structure and function of the insect exoskeleton has proven critical in developing insecticide formulations that are able to penetrate this multi-layered protective covering. Studies of insect communication have led to the discovery of chemical compounds used by insects to locate each other or host plants, and many of these have now been identified and produced synthetically. For example, pheromones are very specific compounds released by insects to attract others of the same species, such as for mating. Synthetic pheromones are now widely used to bait insect traps for detecting the presence of a pest, to determine its abundance, or for control. Control may involve the use of many traps to "trap out" the pest or the pheromones can be dispersed throughout the crop to "confuse" insects, making it more difficult for them to find a mate.

    As simple as it may seem, knowing what type of mouthparts an insect has can be very important in deciding on a management tactic. For example, insects with chewing mouthparts can be selectively controlled by some insecticides that are applied directly to plant surfaces and are only effective if ingested contact alone will not result in death of the insect. Consequently, natural enemies that feed on other insects, but not the crop plant, will not be harmed.

    Since insects obtain oxygen through their spiracles, plugging these openings causes death. That is how insecticidal oils control insects. Components of the microbial insecticide Bacillus thuringiensis enter the digestive system and break down the gut lining. Knowledge of the nervous system of insects has led to the development of several types of insecticides designed to disrupt normal nerve function. Some of these are effective simply by contacting the insect.

    Most species of insects have males and females that mate and reproduce sexually. In some cases, males are rare or present only at certain times of the year. In the absence of males, females of some species may still reproduce. This is common, particularly among aphids. In many species of wasps, unfertilized eggs become males while fertilized eggs become females. In a few species, females produce only females.

    A single embryo typically develops within each egg, except in the case of polyembryony, where hundreds of embryos may develop per egg. Insects may reproduce by laying eggs or, in some species, the eggs may hatch within the female which shortly thereafter deposits young. In another strategy common to aphids, the eggs hatch within the female and the immatures remain within the female for some time before birth.

    Insect Growth and Development (Metamorphosis)

    Insects typically pass through four distinct life stages: egg, larva or nymph, pupa, and adult. Eggs are laid singly or in masses, in or on plant tissue or another insect. The embryo within the egg develops, and eventually a larva or nymph emerges from the egg. There are generally several larval or nymphal stages (instars), each progressively larger and requiring a molt, or shed of the outer skin, between each stage. Most weight gain (sometimes > 90%) occurs during the last one or two instars. In general, neither eggs, pupae, nor adults grow in size all growth occurs during the larval or nymphal stages.


    Complete Metamorphisis : Life Cycle of the convergent lady bug

    The two types of metamorphosis typical of insect pests and natural enemies are gradual (egg > nymph > adult) and complete (egg > larva > pupa > adult). In gradual metamorphosis, the nymphal stages resemble the adult except that they lack wings and the nymphs may be colored differently than the adults. Nymphs and adults usually occupy similar habitats and have similar hosts. Gradual metamorphosis is typical of true bugs and grasshoppers complete metamorphosis is typical of beetles, flies, moths, and wasps. The immatures of these latter species do not resemble the adults, may occupy different habitats, and feed on different hosts. Some moth and wasp larvae weave a silken shell (cocoon) to protect the pupal stage in flies, the last larval skin becomes a puparium that protects the pupal stage.


    Gradual Metamorphisis : Life cycle of the insidious flower bug


    Insects are cold-blooded, so that the rate at which they develop is mostly dependent on the temperature of their environment. Cooler temperatures result in slowed growth higher temperatures speed up the growth process. If a season is hot, more generations may occur than during a cool season.

    A better understanding of how insects grow and develop has contributed greatly to their management. For example, knowledge of the hormonal control of insect metamorphosis led to the development of a new class of insecticides called insect growth regulators (IGR). The insect growth regulators are very selective in the insects they affect. Based on information about insect growth rates relative to temperature, computer models can be used to predict when insects will be most abundant during the growing season and, consequently, when crops are most at risk.

    Insect Classification and Identification

    It is necessary to classify insects so that we can organize what we know about them and determine their relationships with other insects. For example, all members of a particular species will feed on similar foods, have similar developmental characteristics, and exist in similar environments. Most often, insect species are classified based on similarities in appearance (morphology). The flies, for example, can be distinguished and classified separately from all other winged insects because they have only one pair of wings. The hierarchy used to classify the diamondback moth, a worldwide pest of crucifers, is as follows

    • Phylum - Arthropoda
    • Class - Insecta
    • Order - Lepidoptera
    • Family - Plutellidae
    • Genus - Plutella
    • species - Plutella xylostella

    This universal method is used to prevent confusion among geographic regions of the world. Consequently, Plutella xylostella refers to the same insect species in the United States as it does in Asia or anywhere else in the world. Common names, however, can vary from one location to another.

    Ecology is the study of the interrelationships between organisms and their environment. An insect's environment may be described by physical factors such as temperature, wind, humidity, light, and biological factors such as other members of the species, food sources, natural enemies, and competitors (organisms using the same space or food source). An understanding or at least an appreciation of these physical and biological (ecological) factors and how they relate to insect diversity, activity (timing of insect appearance or phenology), and abundance is critical for successful pest management.

    Some insect species have a single generation per season (univoltine), while others may have several (multivoltine). The striped cucumber beetle, for example, overwinters as an adult, emerges in the spring, and lays eggs near the roots of young cucurbit plants. The eggs hatch, producing larvae that emerge as adults later in the summer. These adults overwinter to start the cycle again the next year. In contrast, egg parasitoids like Trichogramma overwinter as immatures within the egg of their host. During the summer they may have several generations.

    Insects adapt to many types of environmental conditions during their seasonal cycle. To survive the harsh winters, cucumber beetles enter a dormant state. While in this dormant state, metabolic activity is minimal and no reproduction or growth occurs. Dormancy can also occur at other times of the year when conditions may be stressful for the insect.

    It is often better to consider insects as populations rather than individuals, especially within the context of an agroecosystem. Populations have attributes such as density (number per unit area), age distribution (proportion in each life stage), and birth and death rates. Understanding the attributes of a pest population is important for good management. Knowing the age distribution of a pest population may indicate the potential for crop damage. For example, if most of the striped cucumber beetles are immatures, direct damage to the above ground portions of the plant is unlikely. Similarly, if the density of a pest is known and can be related to the potential for damage, an action may be required to protect the crop. Information about death rates due to natural enemies can be very important. Natural enemies do nothing but reduce pest populations and understanding and quantifying their impact is important to effective pest management. This is all the more reason to conserve their numbers.


    Basic chemical concepts

    1.1 Do you know the difference between an atom and a molecule?

    1.2 What is the difference between atomic and molecular mass?

    1.3 Define the terms mole and molar.

    1.4 Define what is meant by the terms oxidation, reduction.

    1.5 Define what is meant by the terms cation, anion.

    1.6 Do you understand the nature of the following types of chemical bonds: ionic, covalent, co-ordinate (also known as "dative covalent bond"), hydrogen?

    1.7 What are van der Waals forces?

    1.8 What do these terms mean? Hydrophilic, polar, hydrophobic (non-polar), amphipathic.

    1.9 Describe the structures of the following functional groups: alcohol, aldehyde, ketone, carboxylic acid, amine, amide.

    1.10 Describe the structures of ester, thioester, anhydrides and peptide bonds. Only ester, anhydrides and peptides figure in the syllabus.

    1.11 Define what is meant by the terms acid and base? What is the meaning of pH, defined as the negative log (base 10) of hydrogen ion concentration?

    1.12 Do you have a first-level understanding of what is meant by entropy and enthalpy changes, and of how these are related to the Gibbs free energy change?

    1.13 Define the equilibrium constant for a chemical reaction.

    1.14 What do the terms electrophile and nucleophile mean, as applied to chemical reagents?

    1.15 What are diffusion and osmosis?

    Reading list - Chemistry

    Cambridge Advanced Sciences, Chemistry 1., Ratcliff, Eccles, Johnson, Nicolson & Raffan, Cambridge University Press

    Collins Advanced Modular Sciences, Chemistry A2. Harwood & Hughes

    Collins Advanced Modular Sciences, Physics A2. Kelly


    Characteristics of Three (and a half) Year Old Behavior


    Some time ago I wrote a post on the Characteristics of Two (and a half) Year Old Behavior. In recent weeks, my fourth child’s behaviour has become rather challenging. I was trying to work out what was going on with him and me, that could be contributing to the situation. Going over in my mind, the behaviors he had been exhibiting it came to be straight away, that he has entered another period of disequilibrium – he is the lovely age of three and a half!

    Disequilibrium is the half year period before a child’s birthday, (in this instance from 3 1/2 until 4 years old) where children are confused, emotional, temperamental and may have difficulty completing tasks that they previously have easily accomplished. They then move into phases of equilibrium where they seem to have “got it all together”.


    Your Three Year Old: Friend or Enemy by Louise Bates Ames.
    So I did some research on this stage of child development and came across these couple of paragraphs, which instantly gave me some heart. They are taken from Your Three Year Old: Friend or Enemy by Louise Bates Ames.

    In fact, Three is a highly “we” age. The child likes to say “let’s,” as “let’s go for a walk, shall we?” The sense of togetherness or “we-ness” seems to make him depend on the adult and makes him lean on him or her, though he also enjoys the sense of sharing. The very child who has been so independent earlier may now ask his mother: “Help me,” “show me.”

    Three is a conforming age. Three and a half is just the opposite. Refusing to obey is perhaps the key aspect of this turbulent, troubled period in the life of the young child. It sometimes seems to his mother that his main concern is to strengthen his will, and he strengthens this will by going against whatever is demanded of him by that still most important person in his life, his mother.

    Many a mother discovers that even the simplest event or occasion can elicit total rebellion. Dressing, eating, going to the bathroom, getting up, going to bed – what ever the routine, it can be the scene and setting for an all-out, no-holds-barred fight. Techniques and tricks formerly useful can no longer be guaranteed to work. The mother’s equally resistant response may be tempered by knowing that soon, when he is Four, her child will have developed a self concept strong enough so that he can sometimes conform, and also that he will sometimes enjoy going out of bounds and saying and doing things he knows full well will not be permitted. But even when out of bounds at Four, he will usually be much less difficult to manage then now, at Three and a half.

    How many months is it until April (he will be four then!). Seriously though, reminding myself of how turbulent this age can be and understanding that it is part of his developmental growth, has already given me some feeling of relief and started me thinking of better ways to manage his behaviour. I have listed below some of the characteristics and some “possible” solutions. The solutions are only “possible” because as noted above, they may work one day, but not the next, on these beautiful 3.5 year olds!

    And of course three and a half is not only just challenging behaviours! There are plenty of gorgeous and fun moments in there too, so I have ended the list with some of the more endearing characteristics of this age.

    1. Indecisive

    Me: “What game would you like to play?”
    Master 3.5: “I don’t know.”

    Possible Solution: At this stage of development, going back to offering limited choices, has begun working much better. So by asking him something like “Do you want to play lego or do a puzzle?” it limits his options, but still gives him control in choosing his activity.

    2. Whining

    We have hit some peak levels with whining recently. But at least I know that it is completely normal for this age:

    Tensional outlets increase. There may not be only eye blinking and stuttering, but rubbing of genitals, chewing on clothes, excessive salivation, spitting, tics and whining. In fact, whining is a hallmark of Three-and-a-half, and can be extremely irritating…..Emotional insecurity, which so many seem to feel at this age, may be due to a large extent on the temporary inadequacy of the motor system.

    Possible Solution: No solutions to eliminate this one unfortunately, but am just trying to work with him on it. I calmly state that when he asks for something, he needs to use a clear and calm voice so that I can understand him and respond only once he has done this.

    3. Mum Do!

    Many mornings master 3.5 is not interested in dressing himself and I am told “You dress me.”

    Possible Solution: Firstly he needs to repeat the request using a happy voice and with manners. I then aim for a compromise, something along the lines of “I will do your t-shirt and you can do your shorts.” Knowing that he will move out of this stage and start wanting to dress himself again, and that there are many battle grounds at the moment, I am choosing carefully which ones that I take on!

    4. Volatile Emotions

    Some days it takes only the smallest thing to set of a very loud and long outburst of tears. I may have said that he can only have one yoghurt or he may break his banana while opening it and its like his whole world has just fallen apart.

    Possible Solution: I find trying to reason with him at this point is completely futile. I have had the best results by implementing the hug strategy. Bringing him into me and given him a hug and holding him has helped him regain his composure more quickly.

    5. Falling Over

    There have been many mornings recently on the walk to school where master 3.5 seems to trip over his own feet and ended up flat out on the ground. This usually then sees an episode of point 4 above, which is generally well out of proportion for the actual injury sustained.

    Thus, there is at this age much stumbling and falling. Lack of smooth interplay between flexor and extensor muscles results not only in the gross motor coordination evidenced by stumbling and falling, but also by lack of coordination in the fine motor field as shown by a marked hand tremor in many children.

    Possible Solution: Encouraging him to slow down. He wants to get to places first (see the next point below). I also ask his siblings not to race him on the way to school and keep that activity for at home.

    6. Winning

    Master 3.5 now understands the concept of winning and likes to win. Conversely he can often become very unhappy when he loses.

    Possible Solution: We have had numerous conversations about games being fun and winning not being the most important thing, but it hasn’t really done anything to change the situation. As I said at the beginning, the behaviour of 3.5 year old does vary day to day, if it looks like he is having a day where he is finding things particularly hard, then I will avoid playing competitive games. Also I make sure I choose times when he is less likely to be tired – early morning as opposed to evening, to play these types of games.

    6. Attachment To Every Day Items

    Particular items have taken on much more significance at the moment. He likes to eat his breakfast with a “shiny” spoon and he has a favourite colour cup he likes to drink out of. Volatile emotions can be freely flowing if substitute items are given.

    Possible Solution: This is another one where it is a matter of choosing the right battles with him. It is not really a big deal for me to have the right spoon or cup available and I can then take up bigger issues, like not hitting his siblings when frustrated!

    7. Enforcement Of Rules

    Although he may not want to always follow the rules of the house, he certainly knows them and likes to keep an eye on every one else and see if they are following them. He will quite happily tell his eldest brother “stop swinging on your chair” or his sister “you need to pack up your mess”.

    Possible Solution: It is great that he knows the rules, but I am having a number of chats with him about leaving the commenting on the other children’s behaviour to mum and dad.

    8. Sense Of Humour

    Master 3.5 has really started to display a sense of humour. He laughs at the jokes of his siblings and has started trying to make up his own jokes as well. Naturally the tag line involves either poo or wee, but he thinks they are hilarious and it is very cute to see him join in with the older kids.

    9. Friends

    Recently he has started talking about his “friends” and requesting to have them to play or go and visit them to play. He also on the whole has been managing to keep it together when he has his friends over and is so proud to tell his siblings he had his friend come to play. It is quite heart warming to see him interact with others his own age and have conversations with them.

    10. Love

    As he looks for more security at this stage of his life, I am having a lot more “huggles” as he likes to call them and time with him sitting on my knee. I especially love it when he has just woken up and is all warm and toasty from bed. So also on the plus side to this period of development is that I receiving a lot more physical affection.

    This stage in a child’s life is definitely a challenging one and like all stages, I need to remind myself that this will too pass! In the mean time, I need to focus on choosing the right battles, removing points of conflict and helping him feel secure in his environment.

    Are school mornings stressful for you?

    Are any of these scenarios familiar to you:

    • Are your school mornings currently a harder version of Groundhog Day?
    • Do you sleep a bit longer than planned in the mornings then rush to get you and the kids ready?
    • Do you wake up to a house that is already in a state of mild chaos?
    • Do the kids end up buying their lunches more than you planned because you ran out of time or food?
    • Do you drop the kids off at school with you feeling frazzled and the kids grumpy?

    Then my super simple system will help revolutionise your school mornings! Sign up to my E-news and receive my guide here.


    Watch the video: Characteristics of Life (January 2023).