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Transcript
SUMMARY Module 1: Characteristics, Classification and Diversity of Living Organisms You learned that an individual living thing is called an organism. The term organisms is used to describe something which have all the characteristics of a living thing. Living organisms are different from non-living things in the way that all living things share seven characteristics. The seven characteristics are: - Organisms reproduce - Organisms grow - Organisms feed - Organisms respire - Organisms excrete - Organisms move - Organisms are sensitive. • Classification is the grouping of organisms according to their structural similarities. These groups can be arranged from the largest to the smallest group, they are arranged in Kingdom, Phylum, Class, Order, Family, Genus and Species. • Kingdoms are the highest class for all living organisms and are divided into five kingdoms (Prokaryotes, Protoctista, Fungi, Plants and Animals). Organisms in a kingdom has broader features to group them together, but organisms that are in the species group, has more specific features that group them together. • A species can be defined as a group of organisms with similar features, which are capable of breeding and producing fertile offspring. • Classification hierarchy helps scientists to sort organisms in order, to identify new organisms by finding the group that fit, and it is also easier to study organisms when they are sorted in groups. When a classification name (in Latin) is written it should be underlined, and when typed it should be in italics. • Classification can be based on two different systems, natural and artificial. Natural classification is based on the ideas of homologous structures and evolutionary relationships. • Homologous structures are features of organisms that are similar in structure, but may differ from each other and might be used for different purposes. • Analogues thus look the same but are different, and homologues look different but are the same. • Body parts are considered homologous if they have - the same basic structure - the same relationship to other body parts, and, as it turns out, - develop in a similar manner in the embryo. • The most useful way for scientists to organize biological diversity is to group organisms according to shared evolutionary history. This way the grouping not only results in an organized classification, it also contains and conveys information about our understanding of the evolutionary history of these groups. • An evolutionary relationship is where biologists group organisms together which are structurally similar and share common ancestors. • Early attempts of classification produced the artificial classification that was based on grouping organisms according to: - the way they affect people (domesticated or wild, edible or poisonous - a superficial characteristic (can or can't fly; does or doesn't walk) • Artificial classification systems are also used as the basis for dichotomous keys that biologists use to identify organisms. In the Binomial System an organism is given two Latin names, the first name is the genus and the second name is the species. The Institute of Information Technology, 2008 SUMMARY Module 1: Characteristics, Classification and Diversity of Living Organisms • A dichotomous key is a series of questions asking you about features which you can see on an organism. In each case, two descriptions are given. You have to choose which one applies. This process is repeating itself, until you arrive at the identity of an unknown organism. • The 5 kingdoms are Prokaryotes, Protoctists, Fungi, Plants and Animals. • We saw that the kingdom Prokaryotes (also known as bacteria) is unicellular (single celled) organisms. Bacteria are classified as living organisms, because they carry out movement, respiration, growth, sensitivity, feeding, excretion and reproduction. • In the Protoctist kingdom all organisms are single celled. The body of Protoctists is one cell that contains different structures called Organelles that carry out daily function much like our organs do. One type of organelle found in many protists is the Chloroplast. Chloroplasts are organelles that produce food for the organism through a process called Photosynthesis. Therefore organisms that have chloroplasts do not ingest their food. Protoctists are aquatic. Nearly every animal, fungus and plant has protoctist associates. • Single-celled organisms look like animals in the way that they feed because they feed on other tiny microorganisms such as bacteria, but they are not classified as animals. • Kingdom fungi include organisms such as mushroom, mould, yeast and toadstool. Fungi look like plants because they grow on substrates, but they are not plants as they cannot make their own food by photosynthesis. Most fungi are multicellular (with many cells) organisms, except yeast, which is a single-celled organism. Their bodies are made up of thread-like structures called hyphae which eventually form mycelium. Fungi reproduce asexually by producing spore. Fungi have no chlorophyl with chloroplasts; therefore they do not make their own food by photosynthesis. They use their hyphae to absorb nutrients from dead plant and animal materials. Before they absorb nutrients, the hyphae of the fungi secrete enzymes into food substances to digest it. This means that digestion takes place externally. This way of nutrition is called saprotrophic nutrition. • The Plant kingdom includes all the green plants on our earth, except algae (which is from the kingdom protoctist). Plants are multi cellular organisms and their cells have nuclei and cellulose cell walls. Organisms in the plants kingdom contain chloroplasts with chlorophyll in their cells; therefore they make their own food by photosynthesis. The Plant kingdom are divided into flowering plants (plants that bear flowers and produce seeds) and non-flowering plants. There are two kinds of flowering plants: monocotyledons and dicotyledons. • Kingdom Animals include all animals, except protozoa. All animals are multi cellular organisms. Animals obtain energy by feeding on organic materials. There are two main groups of animals: invertebrates (organisms without a backbone) and vertebrates (organisms with a backbone). • Viruses are so different from other organisms that they cannot be classified as living organisms. They are non cellular as they are not made up of cells. They do not have organelles that are in all living cells. Viruses are made up of a single strand of either DNA or RNA that is surrounded by a protein coat. Viruses do not have their own metabolism and are parasitic; they do not have all of the functions that all living organisms have, but they can reproduce when they invade a host cell. Viruses are responsible for causing diseases in plants and animals. • Flowering plants has roots, stems and leaves. They reproduce by producing seeds from their flowers. Flowering plants are many-celled organisms with cells made up of cell walls, nuclei and chloroplasts containing chlorophyll. Nutrients in soil, The Institute of Information Technology, 2008 SUMMARY Module 1: Characteristics, Classification and Diversity of Living Organisms water and air are turned into food by energy that they receive from sunlight in a process called photosynthesis. • Flowers are the sex organs of plants. • There are two classes of flowering plants, monocotyledons and dicotyledons. Monocotyledonous plants usually have long, narrow leaves with parallel veins. They contain one cotyledon inside their seeds. The flowers of a monocotyledonous plant have petals and sepals that are indistinguishable; their roots are shallow, fibrous and grow from the base of the stem. Flower parts are usually in groups of three or multiples of three. • Dicotyledonous plants have two cotyledons inside their seeds, leaves are broad with branching or network veins, the flowers of the dicotyledonous plants’ petals and sepals are clearly distinguishable, their petals are arranged in groups of four or five. The root system consists out of a main root called the tap root, which grows deep into the soil and lateral roots branch from the tap root. • Animals are classified into two main groups Invertebrates (without a backbone) and Vertebrates (with a backbone). There are three phyla of invertebrates that you need to know: molluscs, annelids and arthropods. • Molluscs have unsegmented soft bodies with slimy skin, and most molluscs have one coiled or two uncoiled hard shells, they live on land and in water. • Annelids are a long cylindrical invertebrate animal that have segments and a body cavity. It includes the earthworms, leeches, and related forms. Annelids have very welldeveloped internal organs. They also have fluid inside their bodies to help them keep their shape, as they do not have a hard exoskeleton or endoskeleton; they also have mucus on their skin to protect them from being damaged. • Arthropods include classes such as insects, arachnids, crustaceans and myriapods. Arthropods are the largest phylum. All arthropods have the following features in common: they have many jointed legs, segmented bodies and an exoskeleton made of chitin and covered with a waterproof cuticle that protects and supports the body. Arthropods are divided into four classes: Insects (insecta), Arachnids (arachnida), Crustaceans (crustacean) and Myriapods (myriapoda). • The main diagnostic features of insects are that they have one pair of antennae, one pair of compound eyes, one or two pairs of wings, three pairs of jointed legs on the thorax and a body that is divided into the head, thorax and abdomen. • The main diagnostic features of arachnids are a body divided into two parts: the cephalothoraxes (head and thorax) and abdomen, no antennae but have chelicerae to hold the prey, several pairs of simple eyes and four pairs of jointed legs. Arachnids are carnivores. • The main diagnostic features of crustaceans are: Eyes in stilts, two pairs of antennae and a body that is divided into cephalothorax and abdomen. Crustaceans have a hard outer shell. • The main diagnostic features of centipedes (myriapods) are: Flattened bodies divided into segments, One pair of legs per segment, A head with a single pair of antenna, poison claws and strong mouthparts. Centipedes are carnivorous. • The main diagnostic features of millipedes (myriapods) are: Rounded bodies divided into segments, Two pairs of legs per segment, A head with a single pair of antenna and strong mouthparts. Millipeds are herbivorous. • Cnidarians are also known as coelenterates; they are some of the simplest animals on earth and live in water. Cnidarians have a sac-like body cavity with a single opening at one end. The body wall consists of two layers of cells; an inner endoderm and The Institute of Information Technology, 2008 SUMMARY Module 1: Characteristics, Classification and Diversity of Living Organisms an outer ectoderm. Cnidarians do not have a middle layer (mesoderm) and does therefore not have body cavity between the two layers of cells. The body plan of a cnidarian is described as diploblastic acoelomate. • Nematodes are described as roundworms. They have long, round, narrow bodies that are pointed at both ends. The body of a roundworm is not segmented and is covered in a smooth cuticle. Nematodes have an anus and mouth. Nematodes are colourless and unsegmented. Nematodes may be free-living, predaceous, or parasitic. Nematodes are the most numerous multicellular animals on earth. Nematodes possess digestive, nervous, excretory, and reproductive systems, but lack a discrete circulatory or respiratory system. • Vertebrates are animals with an internal skeleton made of bone. Vertebrates belong to the phylum chordate. There are five classes of vertebrates: fish, amphibians, reptiles, birds and mammals. • The sub-phylum category for fish is called Pisces. All fish are aquatic, fish have a streamlined body with scales and gills for breathing. Gills perform the gas exchange between the water and the fish's blood. They allow the fish to breathe oxygen in the water. Fishes are vertebrates that have a skeleton made of either bone or cartilage. Fish can be herbivorous or carnivorous. • The class Amphibia includes frogs, toads, salamanders and newts. They have smooth, moist skins with no scales. Amphibians lay their eggs in water and young amphibians tend to resemble small fish. Depending on the species of amphibian, breathing can take place in gills, lungs, the lining of the mouth, the skin, or some combination of these. Amphibian's body temperature changes with its environment. Amphibians hibernate during the winter. • All reptiles are cold-blooded, which is why they warm themselves in the sun, and have bodies covered in dry, horny scales. Some reptiles lay eggs; others give birth to live young. Reptiles breathe with their lungs. Reptiles have scales that protect their skins against dry conditions; their eggs have tough shells that prevent them from being damaged, as most reptiles do not look after their eggs after it was laid. • Birds are warm-blooded vertebrate animals that have wings, feathers, a beak, no teeth, a skeleton in which many bones are fused together or are absent, and an extremely efficient, one-way breathing system. Flying birds have strong, hollow bones and powerful flight muscles. • Mammals have a dry skin that is covered with hair or fur. Unlike other animals, mammals have body hair, have 3 middle ear bones (the malleus, incus, and stapes), and nourish their young with milk that females produce in modified sweat glands that are called mammary glands. Mammals have sweat glands in their skin that produce sweat to regulate body temperature. The Institute of Information Technology, 2008