Where should eggs be stored?

In the fridge stored in the door

Out of the fridge at room temperature

What does FIFO stand for with regards to food storage?

Federation Internationale de Football Organisation

Bacteria and Food Safety

All animals, most protists, all fungi, and many bacteria are het- erotrophs. Unlike autotrophs, heterotrophs cannot manufacture their own food. Instead, they get energy by eating other organisms or organic wastes. Ecologically speaking, heterotrophs are consumers. They obtain energy by consuming organic molecules made by other organisms. Consumers can be grouped according to the type of food they eat. Herbivores eat producers. An antelope that eats grass is a herbivore. Carnivores eat other consumers. Lions, cobras, and praying mantises are examples of carnivores. Omnivores eat both producers and consumers. The grizzly bear, whose diet ranges from berries to salmon, is an omnivore. Detritivores (dee-TRIET-uh-VAWRZ) are consumers that feed on the “garbage” of an ecosystem. This waste, or detritus, includes organisms that have recently died, fallen leaves, and animal wastes. The vulture shown in Figure 18-8 is a detritivore. Many bacteria and fungi are detritivores that cause decay by breaking down complex molecules into simpler molecules. So, they are specifically called decomposers. Some of the molecules released during decay are absorbed by the decomposers, and some are returned to the soil or water. Decomposers make the nutrients that were contained in detritus available again to the autotrophs in the ecosystem. Thus, the process of decomposition recycles chemical nutrients. Copyright © by Holt, Rinehart and Winston. All rights reserved. 368 CHAPTER 18 ENERGY FLOW When one organism eats another, molecules are metabolized and energy is transferred. As a result, energy flows through an ecosystem, moving from producers to consumers. One way to follow the pattern of energy flow is to group organisms in an ecosystem based on how they obtain energy. An organism’s trophic (TRAHF-ik) level indicates the organism’s position in a sequence of energy transfers. For exam- ple, all producers belong to the first trophic level. Herbivores belong to the second trophic level, and the predators belong to the third level. Most terrestrial ecosystems have only three or four trophic lev- els, whereas marine ecosystems often have more. Food Chains and Food Webs A food chain is a single pathway of feeding relationships among organisms in an ecosystem that results in energy transfer. A food chain may begin with grass, which is a primary producer. The chain may continue with a consumer of grass seeds—a meadow mouse. Next, a carnivorous snake may kill and eat the mouse. A hawk then may eat the snake, as shown in Figure 18-9. The feeding relationships in an ecosystem are usually too com- plex to be represented by a single food chain. Many consumers eat more than one type of food. In addition, more than one species of consumer may feed on the same organism. Many food chains inter- link, and a diagram of the feeding relationships among all the organisms in an ecosystem would resemble a web, as shown in Figure 18-10. For this reason, the interrelated food chains in an ecosystem are called a food web.

Some substances, such as macromolecules and nutrients, are too large to pass through the cell membrane by the transport processes you have studied so far. Cells employ two other transport mecha- nisms—endocytosis and exocytosis—to move such substances into or out of cells. Endocytosis and exocytosis are also used to transport large quantities of small molecules into or out of cells at a single time. Both endocytosis and exocytosis require cells to expend energy. Therefore, they are types of active transport. Endocytosis Endocytosis (EN-doh-sie-TOH-sis) is the process by which cells ingest external fluid, macromolecules, and large particles, including other cells. As you can see in Figure 5-7, these external materials are enclosed by a portion of the cell’s membrane, which folds into itself and forms a pouch. The pouch then pinches off from the cell membrane and becomes a membrane-bound organelle called a vesicle. Some of the vesicles fuse with lysosomes, and their con- tents are digested by lysosomal enzymes. Other vesicles that form during endocytosis fuse with other membrane-bound organelles. Two main types of endocytosis are based on the kind of material that is taken into the cell: pinocytosis (PIEN-oh-sie-TOH-sis) involves the transport of solutes or fluids, and phagocytosis (FAG-oh-sie-TOH-sis) is the movement of large particles or whole cells. Many unicellular organisms feed by phagocytosis. In addition, certain cells in animals use phagocytosis to ingest bacteria and viruses that invade the body. These cells, known as phagocytes, allow lysosomes to fuse with the vesicles that contain the ingested bacteria and viruses. Lysosomal enzymes then destroy the bacteria and viruses before they can harm the animal. CYTOSOL EXTERNAL ENVIRONMENT During endocytosis, the cell membrane folds around food or liquid and forms a small pouch. The pouch then pinches off from the cell membrane to become a vesicle. FIGURE 5-7 vesicle from the Latin vesicula, meaning “bladder” or “sac” Word Roots and Origins www.scilinks.org Topic: Endocytosis Keyword: HM60505 mb06se_homs02.qxd 5/18/07 11:03 AM Page 105 106 CHAPTER 5 1. Explain the difference between passive trans- port and active transport. 2. What functions do carrier proteins perform in active transport? 3. What provides the energy that drives the sodium-potassium pump? 4. Explain the difference between pinocytosis and phagocytosis. 5. Describe the steps involved in exocytosis. 6. How do endocytosis and exocytosis differ? How can that difference be seen? CRITICAL THINKING 7. Analyzing Information During intense exercise, potassium tends to accumulate in the fluid surrounding muscle cells. What membrane protein helps muscle cells counteract this tendency? Explain your answer. 8. Evaluating Differences How does the sodium- potassium pump differ from facilitated diffusion? 9. Relating Concepts The vesicles formed during pinocytosis are much smaller than those formed during phagocytosis. Explain. SECTION 2 REVIEW Vesicle Cell membrane EXTERNAL ENVIRONMENT CYTOSOL During exocytosis, a vesicle moves to the cell membrane, fuses with it, and then releases its contents to the outside of the cell. FIGURE 5-8 INSIDE OF CELL Vesicle OUTSIDE OF CELL Exocytosis Exocytosis (EK-soh-sie-TOH-sis) is the process by which a substance is released from the cell through a vesicle that transports the sub- stance to the cell surface and then fuses with the membrane to let the substance out of the cell. This process, illustrated in Figure 5-8, is basically the reverse of endocytosis. During exocytosis, vesi- cles release their contents into the cell’s external environment. Figure 5-8 also shows a photo of a vesicle during exocytosis. Cells may use exocytosis to release large molecules such as pro- teins, waste products, or toxins that would damage the cell if they were released within the cytosol. Recall that proteins are made on ribosomes and packaged into vesicles by the Golgi apparatus. The vesicles then move to the cell membrane and fuse with it, deliver- ing the proteins outside the cell. Cells in the nervous and endocrine systems also use exocytosis to release small molecules that control the activities of other cells.

Orchard / fruit trees Importance of fruit trees • Fruit trees are important for the following uses: They are a source of food, they produce fruits Some are used for making medicines Others provide shade and can also act as wind breakers. Those with beautiful flowers are very decorative. They contain vitamins which means they have nutritional value. Classification of fruit trees • Fruit trees are classified as indigenous and exotic. Indigenous fruit trees • are those that natural grow in a country. • They take longer to grow. • Examples of indigenous fruit trees are: English name Shona Name Snot apple Water berry Red ivory Fig Monkey orange Wild custard apple Mobola fruit Exotic fruit trees • These are trees that were brought from other countries. • They are commercially grown in orchards. • Common exotic fruit trees include: • Exotic fruit trees grow faster than indigenous. Ornamental horticulture • It deals with the growing of decorative plants. • Decorative plants are collectively called ornamental plants. • They include trees, shrubs, flowers and lawn grasses. Importance of ornamental plants They beautify the environment. Flowers often produce a pleasing fragrance. Flowers attract insects like bees that are responsible for pollination. Plants produce oxygen that we need for breathing. • Some are used for making medicines. • Lawn grasses prevent soil erosion. • Plants provide shelter for birds and insects. Classification of ornamental plants • There are four classes of ornamental plants. Trees Shrubs Flowers Lawn Trees: • Ornamental trees are very useful as decorative plants. • This is because most of these trees produce beautiful flowers and some are ever green. • Examples of decorative trees include flamboyant, jacaranda, pines, Cyprus. Shrubs: • A shrub is a woody plant with many branches but smaller than a tree. • Some of them are ornamentals because they produce beautiful flowers. • Others can be cut into decorative shapes. • The golden duranta is good example because it can be cut into nice shapes. • The bougainvillea is another example of a decorative plant because: It can act as a climbing plant. It produces decorative flowers. It can also be cut into any shape using a hedge shear. Flowers: • Flowers have the following functions: They are used for decorations at weddings, hotels and parties. They are used as an expression of love and appreciation such as valentine’s day and get well soon messages. They are useful in bee farming called apiculture as they are a source of nectar used for making honey. Flowers produce a pleasant fragrance used in the production of soaps and scents for perfumes, deodorant and lotions. Lawn: • A lawn is an area of grass that is kept cut short and is usually part of someone's garden or backyard, or part of a park. • Some lawn grasses grown in Zimbabwe are Durban, kikuyu, couch and buffalo lawn. • They prevent soil erosion. • They also provide a comfortable outdoor resting place. Forestry Importance of trees • Trees are important to us and animals. • The Forestry Commission is responsible for taking care of trees in Zimbabwe. • Trees are also important to the environment because: They are a source of fuel in the form of firewood. They are used for making most of the furniture we use. Most medicines come from both exotic and indigenous trees, for example pine trees and gum trees are used for making cough medicines. Trees provide browsing animals like the kudu and giraffe with food. Fruits from both exotic and indigenous fruit trees are a rich source of vitamins Trees give out oxygen which we need for breathing. Trees provide timber that can be used for roofing. • Trees are grouped according to where they come from. • The groups are indigenous and exotic. 1 . Indigenous trees : • These are local trees that have always been grown in their country. Shona name English name Mutohwe Snot apple Mususu Yellow wood Mubvamaropa Blood wood Muuyu Baobab Muonde Fig tree Musasa msasa Characteristics of indigenous trees  take longer to mature  Do not produce straight poles  Grow on their own  Hard wood 2 .Exotic trees : • These are trees that have been brought from another country to be grown in Zimbabwe. Characteristics of exotic trees  They are brought in a country from another country. Grow very fast.  Have soft woods  Usually grow straight  Usually grown in orchards and plantations Common exotic trees in Zimbabwe are: Gum trees Pine trees Wattle Cyprus Date palm Mango Apple pawpaw Causes of plant damage • plant damage is when cultivated crops are kept from normal growth that leads to reduced yields. • plant damage is caused by both living and non living things. • Some of the common causes of crop damage are: (a)Pests • These are living organisms that cause physical damage to crops. • Examples of pests are weevils, army worm, aphids, cutworms and locusts. (b) Diseases • Plant diseases are caused by living organisms called pathogens. • These pathogens infest the plant and take away nutrients. • Fruit rot and bacteria spot are some of the examples of plant diseases. (c) Weeds • these are plant which grow where they are not wanted. • For example if black jack grows in a groundnut field, it is a weed. • Weeds compete for nutrients with cultivated plants. (d) Very high temperatures • High temperatures may cause crops to wither. • High temperatures may also lead to lightning and fires. • This can burn up crops. ( e) Frost • Frost damages crops in winter. • Tomatoes, potatoes, and beans are easily damaged by frost. (f) Drought • drought is when there is no rainfall in a season where it supposed to be raining. • It is one of the most serious forms of crop damage. • Plants wither and die if there is no rainfall. ( g) Animals • Wild animals like baboons often eat maize crops before they mature. • Birds also are a problem to crops like sorghum. Signs of plant damage • There are various signs that show plant damage. • Some can be corrected but some lead to total loss. • Some signs of plant damage include: Lodged plants Flowers and small fruits blown to the ground Dull leaf color Wilted plants Stunted growth

Owls, such as the young snowy owls on the previous page, have for centuries been symbols of both wisdom and mystery. To many cultures their piercing eyes have conveyed a look of intelligence. Their silent flight through darkened landscapes in search of prey has projected an air of power or wonder. For this chapter and this book, owls are an engaging example of a living organism from the world of biology—the study of life. BIOLOGY AND YOU Living in a small town, in the country, or at the edge of the suburbs, one may be lucky enough to hear an owl's hooting. This experience can lead to questions about where the bird lives, what it hunts, and how it finds its prey on dark, moonless nights. Biology, or the study of life, offers an organized and scientific framework for posing and answering such questions about the natural world. Biologists study questions about how living things work, how they interact with the environment, and how they change over time. Biologists study many different kinds of living things ranging from tiny organisms, such as bacteria, to very large organisms, such as elephants. Each day, biologists investigate subjects that affect you and the way you live. For example, biologists determine which foods are healthy. As shown in Figure 1-1, everyone is affected by this impor- tant topic. Biologists also study how much a person should exer- cise and how one can avoid getting sick. Biologists also study what your air, land, and food supply will be like in the near future. SECTION 1 OBJECTIVES ● Relate the relevance of biology to a person’s daily life. ● Describe the importance of biology in human society. ● List the characteristics of living things. ● Summarize the hierarchy of organization within complex multicellular organisms. ● Distinguish between homeostasis and metabolism and between growth, development, and reproduction. VOCABULARY biology organization cell unicellular multicellular organ tissue organelle biological molecule homeostasis metabolism cell division development reproduction gene Copyright © by Holt, Rinehart and Winston. All rights reserved. Biology, the study of life, directly applies to your health, life, and future in ways as simple as daily food choices. FIGURE 1-1 6 CHAPTER 1 Biology and Society By studying biology you can make informed decisions on issues that impact you and our society. Every day newspapers, television, and the Internet contain issues that relate to biology. For example, you may read that your local water or air supply is polluted. How will that pollution affect your health and the health of other living things? You may hear about new technologies or tools that biolo- gists have invented. How will we control how those technologies and tools are used? Biologists actively work to solve these and other real-world issues and problems, including improving our food supply, curing diseases and preserving our environment.

LESSON 3 Characteristics of Living Things Learning Objectives • Describe each characteristic of life • Relate each characteristic of life with how first forms of life evolved What sets living things apart from nonliving things? Organisms are equipped with different characteristics that allow them to grow, adapt, survive, and perpetuate. These include the ability to metabolize, respond to stimuli, interact, and reproduce, among others What are the characteristics of life? Try to look at your surroundings and identify the living things that you see. You have probably identified a lot. Many scientists believe that there are more than 10 million kinds of living things that exist on Earth today. But the question is, how can something be considered living? There are certain characteristics that all living things exhibit: the characteristics of life. Living things are made up of cells. They metabolize, grow and develop, respond to stimulus, adapt to their environment, and reproduce. Living Things Are Made up of Cells All living things are made up of cells. Cells are the basic building blocks of all living things. Each cell contains materials that carry out basic life processes such as respiration. In the 1600s, an argument against the theory of spontaneous generation was made. Italian physician and biologist Francesco Redi disproved the theory that all living things come from nonliving things. Cells have different properties and characteristics. The cell theory describes the properties of all cells. There are three tenets of the cell theory: 1. The cell is the basic unit of life. 2. All living things are composed of one or more cells. 3. All cells arise from preexisting cells. The discovery of the cell is largely attributed to Robert Hooke. Upon examining a piece of cork using a microscope that he built, Hooke observed tiny compartments that he called "cells" (from the Latin word cella, meaning "little room"). Matthias Schleiden suggested that all structural parts of plants are made up of cells. In 1839, Theodore Schwann stated that along with plants, all animals were composed of cells. From these conclusions about plants and animals, advancement on the study of animal parts and functions began. In 1855, Rudolf Virchow included the idea that all cells came from preexisting cells. Some living things are made up of only single cells. Single-celled or unicellular organisms include bacteria, some protists, and some fungi. Even though composed of single cells, these organisms carry out all the functions necessary for life. Most living things such as animals and plants, are multicellular organisms. They are composed of many cells, which are grouped together and perform specific tasks in the body. In different organisms, cells also vary in sizes, shapes, parts, and functions. There are two kinds of organisms according to their cell structure, the prokaryotes and eukaryotes (figure 5-3). Prokaryotes are single-celled organisms that lack a membrane-bound nucleus, mitochondria, and all other organelles. Its name comes from the Greek words pro, which means "before," and karyon, which means "nut or kernel." Eukaryotes are organisms with cells that contain membrane-bound nucleus and other membrane-bound organelles. The nucleus of a eukaryotic cell contains the genetic material (DNA), enclosed by a nuclear envelope. Other membrane-bound organelles are mitochondria, Golgi apparatus, and chloroplast found in photosynthetic organisms such as algae and plants. There are also unicellular eukaryotes known as protozoa. All other eukaryotes are multicellular organisms, such as plants, animals, and fungi. Living Things Metabolize Essential chemical reactions in life can be best described as building up (anabolism) and breaking down (catabolism) processes. In anabolism, the substances needed by organisms to grow, store energy, and repair tissues are synthesized. In contrast in catabolism, some complex substances are broken down, releasing the energy stored in their molecules. This happens in food digestion. This chemical building up and breaking down processes are collectively called metabolism. Metabolism, from the Greek word metabole meaning "change," is the sum total of all the life-sustaining chemical reactions in living things. It allows living things to grow, maintain their structures and functions, and respond to stimuli. Living Things Grow and Develop Growth and development are not new concepts to many. In all living things, growth involves the increase in one's size or height. However, growth is not just an increase in physical structure. It also involves complex changes in an organism. Growth and development occur rapidly from younger stages of life to maturity. In humans, animals, and plants, distinct changes brought by growth and development can be dearly identified. Microorganisms such as bacteria also undergo growth and development until they reach their maximum size and maturity. A life span is the average length of time a aving thing can live. Living things have different life spans. Humans have average life spectancy of 60 to 70 years, while some plants, such as the narra trees, can live for more than 100. Living Things Respond to Stimuli All living things respond to stimuli the environment. This responsiveness Increases survivability. Stimulus (plural: uli) is any signal or change in he environment of an organism that produces a response or reaction from that organism. Responses to stimuli depend on an organism's need. Responding to stimuli also maintains homeostasis in living things. Homeostasis is the internal balance of a body system. This balance is needed for the proper function and regulation of the living thing's body. For example, when a person is in a warmer environment, the body sweats, keeping the body maintain a temperature suited for the normal function of the body. Living Things Interact No living thing can live alone. Interaction among organisms is simultaneously happening on Earth. From the smallest microorganisms to the biggest organism, and from the North Pole to the South Pole of Earth, all are connected in one living system. An ecosystem is formed when a community of organisms interacts with another community and with their environment. Many processes and interactions, such as in a feeding relationship, life cycle, and the exchange of gases between plants and animals, occur in the ecosystem. These are some of the important processes needed to maintain life on Earth. Living Things Reproduce The ability of living things to produce offspring of their kind is called reproduction. Reproduction is not an individual organism's need, rather, it is for the species' perpetuation. In some cases, animals become extinct because of their inability to reproduce their kind. Higher forms of plants and animals reproduce through sexual reproduction. Sexual reproduction involves the union of sex cells or gametes-the egg cell from a female organism and the sperm cell from a male organism. This union gives rise to a new individual with characteristics or traits from both parents. Other simple organisms, such as bacteria and plants, can reproduce asexually. These organisms give rise to a new individual from their body. A bacterial cell divided in two through asexual reproduction gives rise to new bacteria, as shown in figure 5-5. A yeast can form buds that later on become separate individual. Plants grow new plants using their stem, leaf, and roots. Both sexual and asexual reproductions have important functions. In both cases, the genetic material (DNA) is passed on from one generation to the next, ensuring the survival of the species on Earth. 1. Bacteria copy their DNA by starting at any point on the circular chromosomes. 2. The two copies of DNA attach to the inside wall of the bacterial cell. 3. The cell starts to divide, forming a new membrane and cell wall. 4. The bacterial cell splits into two separate cells, each with their own DNA. Living Things Adapt and Evolve All living things can adapt to their environment. This adaptation is necessary for rvival. Adaptation depends on the need of an individual. A polar bear, for example, would not be able to survive in an extremely cold environment without its capacity adapt. Adaptation is any response or reaction toward a stimulus that helps in the survival of an organism. A seed-eating bird will eventually eat a worm when there are seeds to be found. This change in food choice is therefore its adapting mechanism. Prolonged adaptation to certain environments may lead to the gradual evolution of the succeeding generations. Evolution is the gradual change in organisms over a long period in response to changing environment. Living Things Are Organized Life on Earth exhibits organization. The atom is the smallest unit of matter, lowed by molecules, which are combinations of atoms. When these molecules are grouped together, they form a cell. The cell is the basic unit of life. In multicellular organisms, such as plants and animals, cells are grouped as tissues to perform specific Functions. Different tissues can be grouped further and form organs. Organs in animals include the heart, brain, and lungs, among others. The organs form organ systems that makes the function of the body more complex and efficient. Organ systems form the whole organism. All living things exhibit organization, whether they are unicellular or multicellular organisms..

Meaning Of Refuse Refuse are dirty substances or unwanted wastes we have used at home and are ready to be disposed. Refuse should not be kept within the home for a long time to avoid breeding space for pests and bacteria which could bring various infections and dangerous diseases. We can clear refuse by sweeping our surroundings and gathering used items such as can, food remnants, leaves, banana peel, etc. in other to avoid infections and dangerous diseases. The following are the materials used to gather refuse. 1. Brooms 2. Packers 3. Waste basket 4. Dust bins 5. Incinerators Types of Wastes 1) Organic Wastes: These are perishables wastes. They can decay easily. Examples are Yam peels, banana peels, fish wastes etc. These wastes could be burnt when dried . 2) Solid Wastes: These are non-perishable wastes. It takes a long process before these wastes can decay. Examples are cans, tins, broken glasses and bottles. These wastes can be buried. It can also be re-cycled for new things. The following are ways of disposing refuse. 1) Gather the refuse at safe distance and burn them. 2) Bury the refuse by digging hole and pouring them. 3) By recycling refuse to become fertilizer for gardening or farming.

Escape from Unsuitable Conditions Some species can survive unfavorable environmental conditions by escaping from them temporarily. For example, desert animals usually hide underground or in the shade during the hottest part of the day. Many desert species are active at night, when temper- atures are much lower. A longer-term strategy is to enter a state of reduced activity, called dormancy, during periods of unfavorable conditions, such as winter or drought. Another strategy is to move to a more favorable habitat, called migration. An example of migration is the seasonal movements of birds, which spend spring and summer in cooler climates and migrate to warmer climates in the fall. THE NICHE Species do not use or occupy all parts of their habitat at once. The specific role, or way of life, of a species within its environment is its niche (NICH). The niche includes the range of conditions that the species can tolerate, the resources it uses, the methods by which it obtains resources, the number of offspring it has, its time of reproduction, and all other interactions with its environment. Parts of a lion’s niche are shown in Figure 18-6. Generalists are species with broad niches; they can tolerate a range of conditions and use a variety of resources. An example of a generalist is the Virginia opossum, found across much of the United States. The opossum feeds on almost anything, from eggs and dead animals to fruits and plants. In contrast, species that have narrow niches are called specialists. An example is the koala of Australia, which feeds only on the leaves of a few species of eucalyptus trees. Some species have more than one niche within a lifetime. For example, caterpillars eat the leaves of plants, but as adult butter- flies, they feed on nectar. Plants and animals are able to share the same habitats because they each have different niches. FIGURE 18-6 niche from the Old French nichier, meaning “to nest” Word Roots and Origins www.scilinks.org Topic: Niche/Habitats Keyword: HM61029 mb06se_iecs02.qxd 5/24/07 10:25 AM Page 365 366 CHAPTER 18 ENERGY TRANSFER All organisms need energy to carry out essential functions, such as growth, movement, maintenance and repair, and reproduction. In an ecosystem, energy flows from the sun to autotrophs, then to organisms that eat the autotrophs, and then to organisms that feed on other organisms. The amount of energy an ecosystem receives and the amount that is transferred from organism to organism affect the ecosystem’s structure. PRODUCERS Autotrophs, which include plants and some kinds of protists and bacteria, manufacture their own food. Because autotrophs cap- ture energy and use it to make organic molecules, they are called producers. Recall that organic molecules are molecules that con- tain carbon. Most producers are photosynthetic, so they use solar energy to power the production of food. However, some autotrophic bacteria do not use sunlight as an energy source. These bacteria carry out chemosynthesis (KEE-moh-SIN-thuh-sis), in which they use energy stored in inorganic molecules to produce carbohydrates. In terres- trial ecosystems, plants are usually the major producers. In aquatic ecosystems, photosynthetic protists and bacteria are usu-

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