Life Science Notes PDF

LIFE SCIENCE Historical Development of Life Theory of Special Creation  Life is created by a Supernatural power  All living organisms were created same day  They were created in the present form  Their bodies and organs are fully developed to live Theory of Cosmozoic  Proposed b...

LIFE SCIENCE Historical Development of Life Theory of Special Creation  Life is created by a Supernatural power  All living organisms were created same day  They were created in the present form  Their bodies and organs are fully developed to live Theory of Cosmozoic  Proposed by Hermann Richter  Life was present in the form of resistant spores and appeared on Earth from other Planet  “Theory of Panspermia”or “Spore Theory”  Fossils of microorganism were found in meteorites Theory of Spontaneous Generations  Abiogenesis  Non-living materials in a spontaneous manner give rise to life  Thales, Anaximander, Aristotle, Harvey, Newton, and Needham  Van Helmon Theory of Biogenesis  Redi, Richter, and Pasteur  Life arose from pre-existing life.  “bio”- life, “genesis”- beginning  Foundation of the Theories of Organic Evolution Modern Theory  Alexander Oparin’s Theory – gradual chemical changes of ornagic molecules, in the “primordial soup”which existed on Earth four billion years ago  Coacervation Theory – origin of life was preceded by the formation of ’coacervates’. Composed of two or more colloids (protein, lipids, nucleic acid)  J.B.S. Haldane’s Hypothesis – oceans served as a huge cooking pot where chemical reaction could occur to form a huge diversity of organic compounds.  “chemical Theory”  “theory of Primary Abiogenesis” – non-living things can give rise to life in the condition of primitive earth. Fossils  Preserved remains or traces of remains of ancient animals and plants  Fossil records are informative about timing  Earth is 4.5 billion years old  Earliest fossil: 3.5 billion years old History of the Earth: Geologic Time Scale & Relative and Absolute Dating Things to Ponder  Fossils are the remains or evidence of ancient life that have been turned to stone or fossilized.  Fossilization is a process by which the remains of ancient living things are turned to rock 1  Fossils give clues about the history of life on Earth, environments, climate, movement of plates, and other events  The fossil record shows us that present day life forms evolved from earlier different life forms. It shows us that the first organisms on Earth were simple bacteria that dominated the Earth for several billion years.  Scientists are able to arrange fossils according to age and this is called the fossil record. By studying the fossil record, scientists have found that the earth and its life forms have gone through many changes in the past.  Fossils have taught us how and when rock layers have formed. They have also helped the scientists to learn about life forms that have come and gone.  Fossils were used as markers when building up the geologic time scale.  Geologic time scale is a timeline that illustrates the Earth’s past and serve as the “calendar” for events in Earth’s history.  Geologic time scale describes the order of duration of major events on Earth for the last 4.6 billion years.  Geologic time scale was developed after the scientist observed changes in the fossils and rocks going from oldest to youngest sedimentary rocks.  Eons is the largest division in the geologic time scale. The names of most of the eons and eras end in “zoic”, because these time periods were recognized by the animal life present at the time.  Geologic time scale is usually presented in a chart like form with the oldest event at the bottom and the youngest at the top. 2   Geologic time scale was divided into four divisions which include the Eons, Era, Period, and Epoch. Eons Era Period Epoch Age (Mya) Holocene 0.01 YOUNGEST Quaternary Pleistocene 1.8 Cenozoic Pliocene 5.3 Miocene 23.0 Tertiary Oligocene 33.9 Eocene 55.8 Paleocene 65.5 Cretaceous 145 Phanerozoic Mesozoic Jurassic 200 Triassic 251 Permian 299 Carbonif Mississippian 318 erous Paleozoic Pennsylvanian 359 Devonian 416 Silurian 444 Ordovician 488 Cambrian 542 bacteria and blue OLDEST Proterozoic 2500 green algae Precambrian Archean oldest fossil 3800 Hadean Beginning of earth 4600  Eons - The largest intervals of geologic time. A single eon covers a period of several hundred million years. The history of the Earth has been divided into three eons: Arhaean, Proterozoic and Phanerozoic.  Archaean Eon – the period where life first formed on Earth, archea and bacteria. Earth cooled down and was able to support continents and oceans.  Proterozoic Eon – the period just before the proliferation of complex life on Earth. There were extensive shallow epicontinental seas and rocks are less metamorphosed than Archean age. 3   Phanerozoic Eon – this is the period of visible life where rapid expansion and evolution of life forms occur and fill the various ecological niches available on Earth. The time between Earth’s formation and the beginning of the Paleozoic era are often called the Precambrian time or also known as the “time of hidden life”. This era ranges from 4.6 billion years ago when the Earth formed to about 544 million years ago when abundant microscopic life appeared.  Era - It is the subdivision of eons. The geologic time scale is divided into three eras – Paleozoic (time of ancient life), the Mesozoic (time of middle life) and the Cenozoic (time of recent life). Name of era Transition events Ma First appearance of organisms with Paleozoic era hard parts – specific event : The 544 Cambrian Explosion Extinction of over 90% of living Mesozoic era 250 organisms including trilobites Extinction of dinosaurs and many Cenozoic era 65 other organisms  Periods and Epochs - Each era is further divided into periods and further divided into epochs. The Six Major Periods of Paleozoic Era: o Cambrian Period - Almost all marine organisms came into existence as evidenced by abundant fossils. o Ordovician Period - This period marks the earliest appearance of vertebrates and the jawless fish known as Agnatha. o Silurian Period - This period brought the emergence of terrestrial life, the earliest well developed circulatory system (vascular plants) known as Cooksonia. o Devonian Period - This period known as the “age of fishes”. Lowland forests of seed ferns, scale trees and true ferns flourished. Sharks and bony fishes developed. o Carboniferous Period - Warm, moist climate conditions contributed to lash vegetation and dense swampy forests. Insects under rapid evolution led to such diverse forms of giant cockroaches and dragonflies. o Permian Period - A dramatic climatic shift may have been partially triggered the assembly of smaller continents into a supercontinent, Pangea which was surrounded by an immense ocean called Panthalassa. The reptiles were well-suited to their environment that they ruled the Earth for 200 million years. The two major groups of reptiles – diapsids and synapsids dominated this period. Diapsids gave rise to the dinosaurs while synapsids gave rise to mammals.  The Mesozoic Era - Known as the age of reptiles, it is made up of three periods: Triasic, Jurassic and Creataceous. The most significant event was the rise of the dinosaurs. A famous Jurassic deposit is the Morrison Formation, within which the world’s richest storehouse of dinosaurs was preserved. True pines and red woods appeared and rapidly spread. Flowering plants arose and their emergence accelerated the evolution of insects. A major event of this era was the breakup of Pangea. At the end of this era, the dinosaurs and reptiles were completely wiped out.  The Cenozoic Era - This era is known as the “age of mammals” because mammals replaced the reptiles as the dominant land animal. It is also sometimes called the “age of flowering plants” because angiosperms replaced gymnosperms as the dominant land plants. This era is made up of two periods: Tertiary and Quartenary. From oldest to youngest the periods are broken up into the Paleocene, Eocene, Oligocene, Miocene and Pliocene for the Tertiary period and the Pleistocene and Holocene for the Quarternary period. 4 SUMMARY: BIOENERGETICS: UTILIZATION OF ENERGY Definition of terms o Living cells require energy from outside sources. o Some animals, such as the chimpanzee, obtain energy by eating plants, and some animals feed on other organisms that eat plants. o Energy flows into an ecosystem as sunlight and leaves as heat. o Photosynthesis generates O2 and organic molecules, which are used in cellular respiration. o Cells use chemical energy stored in organic molecules to regenerate ATP, which powers work. CELLULAR RESPIRATION is a process of releasing energy stored in sugar in the presence of oxygen. o Cellular respiration includes both aerobic and anaerobic but is often used to refer to aerobic respiration. o AEROBIC RESPIRATION consumed organic molecules and O2 and yields ATP. o Anaerobic respiration is similar to aerobic respiration but consumes compounds other than O2. EQUATION OF CELLULAR RESPIRATION: Reactants: C6H12O6 + 6O2 Product: 6CO2 + 6H2O + Energy (ATP + heat) Principle of Redox Process  During cellular respiration, the fuel (such as glucose (C6H12O6) is oxidized, and O2 is reduced. Oxidation - loses electron Reduction - gains electron THE STAGES OF CELLULAR RESPIRATION Harvesting of energy from glucose has three stages: 1. Glycolysis is the breakdown of glucose to pyruvate where small amounts of ATP are 5  produced. This process occurs in the cytoplasm of the cell. 2. The Citric Acid Cycle or Krebs Cycle degrades pyruvate to carbon dioxide, water, ATP and reducing power in the form of NADH, H+. This stage happens in the matrix of the mitochondria. 6  3. Oxidative Phosphorylation which includes electron transport chain and chemiosmosis generates high amount of ATP, because it is powered by redox reaction. This stage occurs in the inner membrane of the mitochondria. SUMMARY (DIAGRAM) OF CELLULAR RESPIRATION TYPES OF FERMENTATION  Fermentation consists of glycolysis plus reactions that regenerate NAD+, which can be reused by glycolysis. Two Common Types are: 1. ALCOHOL FERMENTATION – pyruvate is converted to ethanol in two steps, with the first releasing CO2.  alcohol fermentation by yeast us used in brewing, winemaking, and baking. 2. LACTIC ACID FERMENTATION – pyruvate is reduced to NADH, forming lactate as an end product, with no releasing of CO2.  lactic acid fermentation by some fungi and bacteria is used to make cheese and yogurt.  Human muscle cells use lactic acid fermentation to generate ATP when O2 is scarce. 7 Perpetuation of Life (Asexual and Sexual Reproduction, Parts of a Flower) REPRODUCTION is one of the characteristics of life. It is a process in which new individual organisms are produced, may it be sexual or asexual.  Sexual reproduction involves the union of gametes (egg cell and sperm cell) through fertilization. Meanwhile,  Asexual reproduction involves the creation of cloned offspring from a parent organism.  Asexual Reproduction in plants, flowers play a major role in sexual reproduction as it houses the structures for this process. “Main Flower Organs” 1. Stamen – The stamen is male reproductive organ, which produces the pollen, which contains the sperm cell. 2. Carpel (Reproductive) 3. Petals 4. Sepals (Sterile)  These organs are held by a structure called a receptacle. Meanwhile, the carpel or the female reproductive organ has the following structures:  Stigma – is the sticky end of the carpel where pollen is trapped during the process of pollination  Style – the style is a slender neck where the sperm cell from the pollen can travel to the base of the carpel called the ovary.  Ovary – In the ovary are ovules, female gametes, which when is fertilized by the sperm becomes the seeds of a fruit. Sometimes, a flower has only one carpel, or has more than one carpel, which is fused, it is called a pistil.  Pollination is the process of transferring pollen from an anther to a stigma.  There are various ways in which pollination occurs whether through self-pollination, wherein the pollen is transferred to the stigma of a plant’s own flower, or Cross-pollination wherein pollen from a different plant is delivered to a stigma of a flower of a different plant.  Pollination is needed in order for fertilization to occur. Compared to self-pollination, cross-pollination can increase genetic diversity of plants as genes from two different individuals are shared by the offspring.  There are different methods on how pollen is transferred from one anther to one stigma. Mainly, pollination is through  Biotic means (80%) and among abiotic methods of pollination,  Wind (98%) and Water (2%) are the main agents. “Biotic Pollinators” 1. Bees – rely on nectars from flowers for they food, as such they pollinate flowers with delicate, sweet fragrance. They are also attracted to bright colors, yellow and blue. 8  Red might be dull to them, but flowers were able to evolve by creating ultraviolet markings as nectar guides as bees can see ultraviolet light. 2. Moths and butterflies – like bees, detect odors and pollinate flowers with sweet fragrance. The difference in activity of a butterfly and a moth allows pollination of different plants, as butterflies are attracted to bright flowers, they are day pollinators while moths, which are mostly active at night, are attracted to white or yellow flowers which are very distinct at night. 3. Bats – like moths are attracted to sweet smelling lightly colored flowers which stand out at night. 4. Flies – are attracted to red, fleshy flowers with a rank odor reminiscent of decaying meat. i. 5. Birds – do not have a keen sense of smell, thus, flower fragrance is not a flower character trait by plants pollinated by birds. Birds are usually attracted to bright flowers such as red and yellow. Also, their nectar has high sugar content which is needed by birds. There are other biotic agents of pollination, which aids in the delivery of pollen to a flower’s carpel.  This organism, as shown above, is adapted to the various characteristics of flowers that require pollination. After the process of pollination, the process of fertilization might occur, which can result in the development of a seed which houses the embryo of a future plant.  Below is the process of gametophyte production, pollination, double fertilization and seed development.  ASEXUAL REPRODUCTION in plants, as some organs grow indeterminately due to tissues that can actively divide (meristem- actively dividing cells) and revert to non- specialized structures (parenchyma tissues).  This indeterminate growth can lead to a form of reproduction called asexual reproduction, as these organs can separate from the parent plant with the ability to grow and develop.  Fragmentation, the most common method of asexual reproduction, can occur through growth from a stem, leaf, root and other plant organ which gained the ability comparable to parent plant.  Not all asexual reproduction is a product of fragmentation, plants can also produce seeds without the process of pollination and fertilization, called apomixis.  Apomixis occurs when diploid cells in the ovule creates an embryo, this can later result in the formation of a seed.  Furthermore, vegetative propagation and grafting are natural and man-made processes of asexual reproduction.  “Different Types of Vegetative Propagation” a Stems: that grow horizontally above the ground is called a runner. The nodes of these plants can allow asexual reproduction through bud growth.  Ex. Grass b Roots: swollen roots called tubers can allow asexual reproduction.  Ex. swollen root of a cassava, not that of a potato. Potatoes are stems, as evidenced of their nodes. c Leaves: that are succulent, such as the catacataca leaf, can allow asexual reproduction. d Bulbs: such as onion (each skin is a leaf) and garlic (each piece is a modified stem and leaf) is attached to an underground stem. Each can form a new bulb underground.  “Artificial propagation” a. Grafting: is composed of the stock (rooted part of the plant) and the scion (the attached part). This is usually done to hasten the reproductive ability of a plant, grow a selected fruiting plant, etc. b. Layering: like what happens to a runner, wherein, a shoot of a parent plant is bent and is covered by soil. This stimulates root growth, after which, the plants can be separated. c. Cutting: is done to propagate a plant by cutting the stem at an angle of a shoot with attached leaves. Sometimes, growth stimulator is given. 9 Perpetuation of Life ((Flowers, Fruits and Seeds) Flowers play a major role in sexual reproduction as it houses the structures for this process.  Below is the picture of a flower and the structures involved directly/ indirectly in sexual reproduction:  Vegetative Part a. Receptacle – holds the floral parts of the flower. b. Sepal – modified leaves that protects a flower in bud and holds the petals when in bloom. c. Calyx – collective term for the sepals. d. Petal – modified leaves that surround the reproductive organ or plants; normally colorful, and with odor, to attract pollinators e. Corolla – collective term for petals f. Inflorescence – cluster of flowers  Reproductive Part a. Stamen – male reproductive organ b. Filament – stalk that holds the anther at the end c. Anther – produces the pollen which houses the sperm cell d. Carpel – Female reproductive organ. Singly or fused, is called a pistil e. Style – the slender neck of the carpel which holds the stigma at its end. f. Stigma – is a structure with sticky substance which traps pollen. g. Ovary – the bulbous structure of the carpel which contains the ovule h. Ovule – has the egg cell of the plant.  Complete vs Incomplete Flower a. A complete flower has all the parts described. b. An incomplete flower is missing one or more parts.  Adaptive mechanisms a. As the flower is important in the development of a fruit and the eventual dispersal of the seed for plant propagation, it has evolved different adaptive mechanisms. b. This structure to function relationship is important as the plant should be able to attract specific pollinators to increasing the success rate of its propagation. c. Competition among plants over one pollinator may result in lesser chance of propagation. FRUITS Fruits – structures that not only protect the seeds of plants but also aid in their dispersal; derived from the maturation of a flower’s ovary. a. The ovary walls eventually become the pericarp during development.  Pericarp-the walls of a ripened ovary/fruit  Parts of a Fruit 1. Exocarp- outer skin of the fruit. 2. Mesocarp- fleshy middle layer of the pericarp of a fruit. Part of a fruit that can be eaten. 3. Endocarp- inside layer of the pericarp which directly surrounds the seeds. b. Depending on fruit adaptations, the pericarp can be stony, woody, fleshy as such the endocarp might not be fleshy, the exocarp might be rubbery or woody, etc. For example: the apple’s seed and fruit are protected by an accessory fruit which formed from the fleshy receptacle. 10  SEEDS a. The seed or mature ovules contain the embryo, which will eventually germinate and grow if properly dispersed in a favorable environment. b. To protect the embryo from harsh environmental conditions, it goes into a state of dormancy until a period for favorable growth and development arrives. The embryo, which is not able to produce its own food, yet, is provided with food by the cotyledon or the endosperm, or both. c. To protect the embryo, the seed coat has a hardened outer covering which protects it from physical or chemical disturbances. d. Parts of a Seed 1. Testa- outer coat of the seed that protects the embryonic plant. 2. Microphyle- it is a tiny pore in the testa and permits water to enter the embryo before active germination. 3. Cotyledon- contains high quantities of starch and will provide a source of food. 4. Epicotyl- is the embryonic shoot above the cotyledon that will eventually develop into the leaves of the plant. 5. Hypocotyl- connection between cotyledon and radicle. Pushes the cotyledons above the ground to develop. 6. Radicle- this is the embryonic root which will develop into the primary root of the plant. e. In grass, the embryo is protected by two sheaths: the coleoptile (protects the young shoots) and coleorhiza (protects the young roots). SEED AND FRUIT DISPERSAL 1. Like pollination in plants, different agents aid seed and fruit dispersal. a. Abiotic agents (wind, water) b. Biotic agents (animals) 2. In order to propagate, plants have evolved in order to adapt to their environments. a. Flowers ensure the formation of the embryo through different adaptations for pollination and fertilization. b. The developing embryo is helped by the adaptation of the fruit and seeds, which further protects and aids in its propagation. Perpetuation of Life (Plants and Animal Reproduction)  Sexual reproduction is the process of joining the haploid gametes (sex cells) to form a diploid cell called a zygote.  A zygote, eventually becomes an embryo and later on develop into an organism.  The female gamete is an egg cell, is usually non-motile, to ensure survival of the embryo by storing energy.  The male gamete is a sperm cell, which is motile to search for the egg cell for fertilization.  Asexual reproduction- fusion of the egg cell and sperm cell does not occur; reproduction is mainly through mitosis which creates a clone of the parent. “The following are the different methods of asexual reproduction: 11 1. Budding- occurs when individuals arise throughout the outgrowths from a parent. This can create a colony of individuals attached to a parent, such as in corals. 2. Fission- is the separation/division of an organism to form individuals of approximately same size. This is usually observed in animal-like protists. 3. Fragmentation and Regeneration- fragmentation is when an animal’s body breaks into different parts, which later regenerate to form several individuals. Sponges, annelids, cnidarians and tunicates are examples of this mode of reproduction. 4. Parthenogenesis- is like apomixes in plants, where the egg cell develops without fertilization. This is exhibited by bees, wasps, lizards, sharks. 12 13 Perpetuation of Life “GENETIC ENGINEERING” Genetic engineering is the process in which genetic material is transferred from one organism to another. Artificial selection is the most traditional form of genetic engineering, wherein specificity of synthesis of target DNA sequence is less than current genetic engineering technology. Genetic engineering has application on the pharmaceutical, industrial, aricultural, medical and other industries. One example is the transfer of genetic information from a firefly and a jellyfish for bioluminescence to a tobacco and a pig. This has application for medical technology, especially in tracking cell activities. Example Process of Genetic Engineering 1. Genetic information is inserted via a vector. The small replicating molecule is called a DNA vector (carrier).The most commonly used vectors are plasmids(circular DNA molecules that originated from bacteria), viruses, and yeast cell. A specific target genetic segment is spliced into a bacterial plasmid. The resulting molecule is called recombinant DNA. It is recombinant in the sense that it is composed of DNA from two different sources. (Diagram on the right shows the process in creating a recombinant DNA molecule) 2. Recombinant DNA (plasmid) put into a bacterial cell and allowed to be replicated. 3. This gene can then be transferred to a target organism, such in the case of pest-resistant crop, or proteins can be harnessed, such as in the case of insulin. (sample illustration on the next page) 14 Genetically Modified Organism (GMO) “Genetically Modified Organism” A genetically modified organism, or GMO, is an organism that has had its DNA altered or modified in some way through genetic engineering. Genetically modified organisms (GMOs) are produced using scientific methods that include recombinant DNA technology and reproductive cloning. 1. What are the positive impacts of GMOs? 2. What are the negative impacts of GMOs? Reference:https://www.slideshare.net/mobile/jcedarbaum1/ib-biology-35-slides-genetic-modification-biotechnology 3. Is there a biological reason in resisting the use of GMO? Each gene may control several different traits in a single organism. Even the insertion of a single gene can impact the entire genome of the host resulting in unintended side effects, all of which may not be recognizable at the same time. It is difficult to predict this type of risk. Therefore, there could be a number of predictable and unpredictable risks related to release of GMOs in the open environment. 15  4. What are possible reasons not to allow GMOs in a country? The Philippines is the first country in Southeast Asia to approve the commercial cultivation of a genetically modified crop for feed and food. Its negative effects on human health and the environment are still debatable. When researchers found out its long term negative effects, it's the time to our government to ban the usage of GMOs. 5. As a country with a history of economic, political, psychological dependence and subservience to other countries, do you think the use of GMO will be more beneficial or detrimental? *Subjective answer 6. Barring biological use of GMOs, how is the use of GMO in the country a symptom of political and economic dependency to other countries? Governments of developing countries are responding to those concerns in a variety of ways with some banning GMOs outright, some embracing them, and others attempting to find balance between the concerns and needs of all sides. Developing countries are slowly increasing approved legislation and opening the door to research and commercialization of GMO crops. As these countries seek to expand their export markets, improve domestic living conditions, and address food insecurity in the wake of conflict and climate change, some are seeing a solution in genetically engineered crops. 7. How can the benefits of GMOs outweigh its negative effects? It has been argued that from the available experimental data, currently utilized GM plants appear safe and show no effects on animals or animal products. It has also been stated that risks caused by the use of GM plants appear to be so low that they should be negligible in comparison with their potential benefits. However, long-term risks for most conventional foods have never been analyzed. GM crops are novel foods, and the assessment of their safety is essential to protect the environment, as well as the health of humans and livestock. How Animal Survive (Nutrition) “NUTRITION” Animal nutrition is the process of taking in, taking apart and taking up the nutrients from a food source. Food processing has four main stages: Ingestion, Digestion, Absorption and Elimination or Egestion.  In ingestion, or process of taking in food substances, the animal takes in food in different ways. Microscopic animals, for instance, can use special cavities which can allow entrance of food or they can use phagocytosis or pinocytosis wherein food particles are engulfed, thus, creating a food vacuole. In other animals, such as in cnidarians (jellyfish, anemone, coral) where the entrance and exit of food and waste is the same, the region where this occurs is called the gastrovascular cavity. Gastro for digestion, vascular for circulation of movement of digested food. In other animals, with complete digestive system, where entrance and exit of food and wastes are different; there are different mechanisms of ingestion depending on their evolutionary adaptation to their food. The four main feeding mechanisms are filter feeding, substrate feeding, fluid feeding and bulk feeding. A. Filter feeding- uses adaptation in feeding food particles from the environment, which is usually aquatic. Examples of these are clams, mussels, whales, etc. B. Substrate feeding- animals live in or on their food source. Examples of this are the leaf miner, maggots and other parasites. C. Fluid feeding- animals suck nutrient-rich fluid from a host or a source. They have different adaptations in order to get food such as the proboscis of mosquitoes, the long tongue of nectar-feeding bats and long beaks of hummingbirds. 16 D. Bulk feeding- animals, such as us humans, take in large particle sized food. Different animals have acquired different adaptations such as tentacles, claws, venomous fangs, large mandible and teeth which aids in killing prey or tearing off pieces of meat or vegetation  Digestion of food involves either intracellular digestion or extracellular digestion or both processes. Digestion can either be mechanical or chemical. Mechanical digestion aids in physically breaking down food particles for easier chemical digestion. Chemical digestion is the process of breaking down complex molecules into simpler molecules through chemical hydrolysis.  Absorption allows the animals to acquire the necessary energy, organic molecules and essential nutrients from the digested food. Chemical energy comes from the breakdown of ATP which comes from sources such as sugars from carbohydrates. Organic molecules can serve as the organic building blocks of the body where muscles, connective tissues, nerve tissues are built. These organic molecules are the biomolecules that we acquire from food: carbohydrate, protein, fats and nucleic acids. Carbohydrates are important for instant energy, but if not used will be stored and can turn into fats. Proteins, which are made up of amino acids, are the building blocks of different structures in the organism, e.g. muscles, cells, antibodies, etc. Fats are great source of energy as they can store a lot of energy. Nucleic acids are important for building blocks of genetic information. Essential nutrients are substances which the animal’s own body cannot synthesize, thus, come from the food source. Essential amino acids, essential fatty acids, vitamins and minerals are examples of essential nutrients.  As food is only partially digested, not all particles are absorbed by the body. The semi- digested food, which in turn becomes waste is then eliminated or digested. In some animals, such as humans, water is first reabsorbed before it is eliminated or egested out of the body. Different symbiotic relationships are present in order to fully utilized the substances present in waste (feces) before it is finally released. THE HUMAN DIGESTIVE SYSTEM The human digestive system can serve as a model for other organisms with complete digestive system. The mouth or oral cavity- is responsible for ingestion. In humans, the mouth has specialized dentition for mechanical digestion of food. Also, chemical digestion of food occurs in the mouth, specifically, of carbohydrates. With the aid of the salivary gland, food is softened and rolled by the tongue, which results in a round, semi-digested food called the bolus. Some animals do not have teeth, such as birds and earthworms, they use a structure called gizzard, a muscular organ which grinds food with the aid of ingested pebbles or stones. The bolus enters the digestive tract, via a cross- road of food and air called the pharynx. To prevent food from entering the respiratory system, the epiglottis covers the opening (called the glottis) to the respiratory when swallowing. The esophagus, which has voluntary muscles at the pharyngeal end, allows the movement of bolus to the stomach by lubricating its walls with mucus produced by goblet cells. Movement of food, not only through the esophagus, but throughout the digestive tract is caused by peristalsis or the wavelike movement of the muscles of the organs of digestion. Mucus not only allows easier movement of food, but it also protects the lining of esophagus from acids of the stomach. 17  The stomach is a bag which mainly functions in the storage of food. Chemical digestionXof food starts here through the action of pepsin (an enzyme for protein digestion) and hydrochloric acid (HCl) helps in breaking cells, activating pepsinogen to pepsin, and denaturing proteins. Denaturation is the process of breaking the bonds of protein, through acids, bases, heavy metals, high temperature and others. The product of digestion in stomach is called the chime. The stomach has two valves at each end, which regulates the entrance and exit of food. Cows do not have four stomachs; rather they have four-chambered stomach which aids in chemical digestion of cellulose in plants. As cows do not have the ability to completely digest cellulose, they have mutualistic relationship with bacteria which digests cellulose, needing the four-chambers of the stomach. When the stomach is filled, the product of its digestion called chyme or acidic chyme (due to its acidic nature) moves to the small intestines. In the small intestines, chemical digestion of the four biomolecules occurs. Different enzymes and hormones are activated/released to the small intestine by the small intestine itself, the liver and the pancreas. These hormones, chemicals and enzymes are responsible in turning complex biomolecules into simpler molecules. Bile for example, is a substance produced by the liver and stored by the gall bladder which aids in the digestion of fats by emulsification of fat molecules. Villus (plural- villi) and microvillus (plural- microvilli) are structures responsible for the efficient absorption of the digested molecules. Thus, the small intestine has the largest surface area among the organs in the digestive system. The large intestine, termed for its larger diameter compared to the small intestine, is responsible for water reabsorption and temporary storage of feces. Water from the process of digestion, which comes from the surrounding tissues (mucus, saliva, chemicals), is recycled by the large intestine by reabsorbing it. The rate of water reabsorption has implication on the hardness/softness of the feces to be eliminated. In humans, the cecum is a structure called appendix, a vestigial organ. It does not have any known digestive function, but some argue that it has immune functions. For herbivores, the cecum is a very long structure as they house organisms which can aid in the digestion of cellulose just like in the four-chambered stomach of cows. The rectum is the structure of the large intestine which temporary store feces, the movement of the feces is regulated by a voluntary muscle called the anus. HOW ANIMAL SURVIVE (CIRCULATION AND GAS EXCHANGE) “Circulation and Gas Exchange” The Circulatory System There are different ways in which animals transport substances across their body. Animals with thin body rely on diffusion, which is the movement of substances from high concentration to low concentration, in the transport of substances. Thus, organisms such as those with gastrovascular cavity like cnidarians, flatworms use diffusion in moving substances across and within their bodies. Animals have evolved structures which carry substances (circulatory fluid, e.g. blood), pipes (blood and lymph vessels) and a pumping organ (heart). Animals with these structures either have an open or closed circulatory system.  In an open circulatory system, blood is not fully enclosed in a vessel and is pumped out of the system via an exit called an ostium to a space which surrounds tissues called a sinus. When the heart contracts, the circulatory fluid goes out of the system, if the heart relaxes the fluid returns. As the blood goes directly to the tissues, it mixes with the interstitial fluid which surrounds tissue and cells and is called a hemolymph. 18  The interstitial fluid allows diffusion from the blood to a cell. In an open circulatory system, circulatory and respiratory systems are independent of each other.  In animals with closed circulatory system, the circulatory fluid does not go out of the vessel. Exchange occurs through diffusion via thinner vessels called capillaries across the interstitial fluid. STRUCTURES 1. Atrium- receives blood 2. Ventricle- pumps blood 3. Artery- transports blood away from the heart, muscular 4. Vein- transports blood back to the heart, has valves and thinner in structure 5. Capillary- exchange of substances, has very thin walls 6. Venule- small vein 7. Arteriole- small artery a. The pulse is the wavelike force which is a result of the pumping of blood through an artery with decreasing diameter. As the diameter of the artery decreases, the walls of the artery stretch to accommodate the blood that is passing through it. b. The heart has the ability to produce its own electrical signal to stimulate the contraction of the heart muscles. Thus, the heart is independent from the brain; the brain only affects the rate of heart contraction but not starts the contraction of the heart. The cardiac cycle is the complete cycle of contraction and relaxation, together with the intervening phase. c. Systole- is the contraction phase of the cardiac cycle d. Diastole – is the relaxation phase of the cardiac cycle GAS EXCHANGE Gas exchange is very important animals, as they require oxygen in the production of higher amount of energy compared to process of energy production without oxygen. Aerobic respiration is the term used when oxygen is present in the production of energy, while anaerobic respiration is the process energy production without oxygen. In order to acquire oxygen, different animals have evolved different adaptations in order to adapt to their environment. What is constant among these organisms are 1.) a thin respiratory structure, 2.) moist respiratory surface and 3.) respiratory structure with high surface area. THE TRACHEAL SYSTEM OF INSECTS The tracheal system of insects has a branched network of tracheal tube which responds to the problem of decreased surface area in the respiratory structure. The tracheal system opens externally through the side of the insect through a structure called a spiracle. Air enters and exit through the spiracles. As the respiratory systems of insects are independent from their circulatory system, gases are directly exchanged through tracheales which have extensions that are directly connected to the cells. Air sacs act like aspirator which takes in and push out air out of the body of the insects. TERRESTRIAL VENTILATION Ventilation in lungs is called breathing, the alternating process of inhalation and exhalation. There are two mechanisms of breathing, one is positive breathing and the other is negative breathing. In positive breathing air is pushed into the lungs, such as in frogs. Meanwhile, humans and other mammals use negative pressure breathing by sucking in air in to the lungs through the creation of a negative pressure. When chest muscles contract, they increase the volume of the chest cavity decreasing the pressure inside. As the pressure decreases inside the lungs, air is pulled into the lung cavity. The relaxation of the chest muscles squeezes out air through the process called exhalation. GAS EXCHANGE AND THE CIRCULATORY SYSTEM As the circulatory system functions in the delivery of the energy sources in the form of molecules processed by the digestive system, the respiratory system is important in the released of waste gases (CO2) and the delivery of oxygen for energy production. Sugars are broken down, and the resulting process results in the formation of ATP, which when broken down by cells produce energy which the cells can use for its metabolic activities. The process 19  of glycolysis, is an anaerobic process which does not require oxygen but creates little amount of ATP. The electron transport chain (ETC), which uses oxygen produces the most ATP. Along the process, CO2 is produced as a by-product, which the circulatory system and respiratory system released via exhalation. HOW ANIMALS SURVIVE (HOMEOSTASIS AND WASTE REMOVAL)  Excretion is the process of removing wastes and excess water from the body. It is one of the major ways the body maintains homeostasis. Organs of excretion make up the excretory system. They include the kidneys, large intestine, liver, skin, and lungs.  The kidneys filter blood and form urine. They are part of the urinary system, which also includes the ureters, bladder, and urethra.  Each kidney has more than a million nephrons, which are the structural and functional units of the kidney. Each nephron is like a tiny filtering plant.  The kidneys maintain homeostasis by controlling the amount of water, ions, and other substances in the blood. They also secrete hormones that have other homeostatic functions. HOW ANIMALS SURVIVE (HORMONES)  Hormones are chemical substances which can cause a reaction to cell. It is transported to the bloodstream and go to the target cells to elicit a response, which can rapid or slow.  The cell membrane chooses the molecule which can go in and out the cell. It has lipid bilayer which is hydrophobic or water fearing thus prevents the free movement of water-soluble hormones  Water-soluble hormone dissolves in water (rather than oils / fats). It was formed from amino acids. It cannot pass through the target cell membranes (which include fatty components). It affects cells by binding to receptors on the surface of the target cell.  Fat-soluble hormones dissolve in fats rather than in water. It is usually formed from cholesterol (cholesterol molecules being important components of cell membranes) therefore fat-soluble hormones can pass through cell membranes (see also functions of cell membranes). It affects cells by binding to receptors inside the target cell.  The ability of fat-soluble hormones or steroid hormones to pass through the cell membrane allows them to initiate cell response inside the cell. Their receptors are found on the nuclear membrane which can initiate gene expression thus as a result, steroid hormones can have a longer lasting effect that water soluble hormone or peptide hormone HOW ANIMALS SURVIVE (IMMUNE SYSTEM)  Pathogen is a foreign substance, living or non-living which elicit an immune response in a form of illness which is a defense mechanism of the body.  Innate immunity attacks wider range of pathogen. It is not very specific but the response is rapid. Meanwhile, adaptive immunity is specific but has slower response rate.  The line of defenses includes barrier defense (skin, mucous membranes, secretions), internal defense (phagocytic cells, natural killer cells, antimicrobial proteins, inflammatory response).  Specific immune response includes humoral response wherein antibodies defend against infection in body fluids and cell-mediated response where cytotoxic cells defend against infection in body cells  Active immunity is acquired from vaccine or developed by the body after exposure to pathogen while passive immunity is a specific immune response acquired from mother or artificially from an immune serum medicine. 20 HOW ANIMALS SURVIVE (NERVOUS SYSTEM)  The nervous system has two main parts. The central nervous system is made up of the brain and spinal cord. The peripheral nervous system is made up of nerves that branch off from the spinal cord and extend to all parts of the body.  The functional unit of the nervous system is the nerve, which is composed of neurons that have extensions for transmission of messages. The extensions of neurons are called dendrites and axon wherein axons transmit message away from the cell body of the neuron while dendrites transmit message towards the cell body of the neuron  The protein channel or gate allows and inhibits the movement of ions such as K+ and Na+ which creates membrane potential (voltage) that is transmitted as the message throughout the nervous system  Involuntary responses are actions which take place without consciousness or willingness of an individual while voluntary responses are action produced with the involvement of thoughts. HOW ANIMALS SURVIVE (LOCOMOTION)  The sarcomere is the functional unit of the muscle fiber. Z-discs is a three-dimensional cylinder-like arrangement and is bordered by structures connected to thin filament. Actin is thin filament while myosin is a thick filament. The middle of the H zone has a vertical line called the M line, at which accessory proteins hold together thick filaments.  When contraction occurs, the sarcomere shortens and this is reflected in the contraction of a muscle. In terms of the molecular and physiological process of contraction, nerve impulse transmission is needed to depolarize the cell membrane of the muscle to stimulate contraction. The sliding filament theory is the explanation for how muscles contract to produce force  There are different skeletal systems which the muscle can pull on, these are the hydrostatic skeleton, exoskeleton and endoskeleton. A hydrostatic skeleton is a skeleton formed by a fluid-filled compartment within the body. An exoskeleton is an external skeleton that consists of a hard encasement on the surface of an organism. An endoskeleton is a skeleton that consists of hard, mineralized structures located within the soft tissue of organisms Prepared by: MS. HEYDEE CANDAWAN, LPT Stem Teacher 21