Chapter 4 Classification Of Living Things PDF

# Chapter 4 Classification of Living Things ## Butterflies are insects. Why? - They have similar characteristics with other insects such as grasshoppers and flies. - All of them have no backbones. - All of them have three body segments and three pairs of jointed legs. ## What will you learn? - Lis...

# Chapter 4 Classification of Living Things ## Butterflies are insects. Why? - They have similar characteristics with other insects such as grasshoppers and flies. - All of them have no backbones. - All of them have three body segments and three pairs of jointed legs. ## What will you learn? - List the levels in the Linnaeus's taxonomic hierarchy system - Describe what binomial nomenclature system is - Describe what a dichotomous key is - Draw a dichotomous key for a group of organisms - List the five kingdoms with examples - Classify animals into vertebrates and invertebrates - Classify plants into non-flowering and flowering plants ## 4.1 Classification System and Naming of Organisms Biodiversity is the variety of all organisms such as animals, plants and microorganisms that interact with one another. ### Taxonomic Hierarchy System Classifying living things with similar characteristics aids in the systematic organisation of scientific discoveries, making it easier for scientists to trace the origins of living things. Carl Linnaeus, also known as the Father of Taxonomy, was a botanist who developed a scientific method of naming and classifying organisms in 1750s. ### Importance of classification - Can identify organisms easily and accurately - Ensure that no two organisms have the same name - Avoid confusion in naming an organism - Facilitate discussions at international level Linnaeus's taxonomic hierarchy system classifies organisms based on their position in the hierarchy. - The highest level is **Domain** which is the most general, followed by **kingdom**, **phylum**, **class**, **order**, **family**, **genus** and **species** which is the lowest level and the most specific. ## Think About It Do tigers and cats belong to the same family? What is the Linnaeus's taxonomic hierarchy system that shows the classification of cats? What are the two plants in the same family but with different species? Show their taxonomic hierarchies? ## Binomial Nomenclature System Carl Linnaeus developed the binomial nomenclature system in the 18th century. - Each species is given a scientific name that consists of two Latin words. - The first word is the genus (generic) name, and the second word is the organism's specific name. - **Humans**, for example, have the scientific name **Homo sapiens**. - **Homo** is the genus name, whereas **sapiens** is the specific name. - The genus name starts with a capital letter, while the specific name starts with a small letter. - The scientific name (both words) is italicised. Both words must be underlined separately if written. - A given scientific name normally refers to the name of person, place or characteristic of the organism. - For example, the scientific name **Escherichia coli** is named after Theodor Escherich, a scientist who discovered the bacterium. - The specific name **coli** shows that E. coli lives in the colon (large intestine). - Although the common names of an organism may differ in different places, it can be identified based on its scientific name which is used internationally. ## Dichotomous Key A dichotomous key is a tool for identifying organisms or things found in nature, such as plants and animals, based on their common characteristics. - Dichotomy means division into two, hence a dichotomous key always provides two choices based on the main characteristics of organisms in each couplet series. - A dichotomous key can be built based on a set of paired statements or clues concerning features or characteristics that serve as a step-by-step guide to identifying each organism or in the form of a flowchart. - The clues steadily narrow down the list of possible organisms as the user progresses from one step to the next, until all are identified. - The chart below shows a guide for building a dichotomous key for plants. ### Rules to build a dichotomous key - Let's take a look at an example of a dichotomous key for plants using a series of statements. - 1 (a) Have flowers. ..........go to 2 - (b) Do not have flowers...... go to 3 - 2 (a) Monocotyledon.....paddy plant - (b) Dicotyledon ---------- hibiscus - 3 (a) Vascular... -----------ferns - (b) Non-vascular.-------- mosses ## 4.2 Classification of Organisms After learning Linnaeus’s taxonomic hierarchy system and binomial nomenclature system, let's learn about the five kingdoms of living organisms: monera, protists, fungi, animals and plants. Unlike animals and plants, there are tiny living organisms known as microorganisms, that can only be observed using a microscope. Examples of these microorganisms are bacteria, protozoa and fungi. ### Monera (bacteria and blue-green algae) Bacteria are single-celled organisms that exist everywhere in the millions either inside or outside other organisms. - They come in various shapes and sizes. - Bacterial cells are different from plant cells and animal cells. - They have no nucleus. - They have cytoplasm which is a substance inside the plasma membrane that contains genetic material (DNA) and ribosomes. - This DNA contains all the genetic information used in the development and function of the bacterium. - Bacteria need food, will respire, grow, reproduce and excrete waste products. - Some bacteria have flagella that are used for movement. - There are good and bad bacteria. Did you know Salmonella is a harmful bacterium that can cause food poisoning? However, there are some good bacteria in our gut that help to keep us healthy. ### Good Bacteria - Lactobacillus - Lactococcus - Streptococcus thermophilus - Propionibacterium - Bifidobacterium ### Bad Bacteria - Salmonella - Escherichia coli - Staphylococcus - Clostridium perfringens - Campylobacter ## Think About It Normally, E. coli bacteria are found in both human and animal intestines. However, some of them can cause diarrhoea because they are pathogenic. How is this type of bacteria transmitted into the human body? ### Blue-green algae or called cyanobacteria - Are unique organisms within the kingdom of Monera. - Monera is a classification that includes simple, single-celled organisms lacking a nucleus, and blue-green algae fit perfectly into this category. - Blue-green algae are a group of bacteria capable of photosynthesis. - These microorganisms can be found in various aquatic environments, such as ponds, lakes and even in damp soil. - What distinguishes them is their vibrant blue-green colour, derived from pigments such as chlorophyll, allowing them to capture sunlight for energy, similar to plants. - Some common examples of blue-green algae include species like Spirulina and Nostoc. - Spirulina, often consumed as a nutritional supplement, forms spiral-shaped filaments, while Nostoc colonies can be seen as slimy gelatinous masses in moist areas. ## Science Facts Blue-green algae played a pivotal role in Earth's history by producing oxygen through photosynthesis, contributing to the development of an oxygen-rich atmosphere. These ancient microorganisms continue to thrive in diverse ecosystems, showcasing their enduring impact on the planet's evolution. ### Protists Protists can be categorised into three main groups: protozoa (animal-like protists), algae (plant-like protists) and slime moulds (fungus-like protists). This classification is based on their similarities to the complex organisms of animals, plants and fungi. ### Protozoa - Are animal-like protists that are heterotrophic, which means they obtain their food by consuming other organisms. They can move around to hunt for food, often using structures like cilia or flagella.. - Examples of protozoa include Amoeba, Paramecium and Euglena. - Like bacteria, protozoa are single-celled organisms and vary in size and shape. Some, like the Amoeba, can change its shape. Others, like the Paramecium, have a fixed shape and complex structures. - They are commonly found in wet habitats such as freshwater, marine environments and soil. - The Amoeba is a single-celled organism that can change its shape. - Ponds, lakes and slow-moving rivers are common places where it can be found. - The structure of Amoeba mainly consists of the cytoplasm, plasma membrane and the nucleus. - Pseudopodia are projections created when the cytoplasm pushes the plasma membrane outward or inward, resulting in blunt, finger-like projections. - Paramecium is a single-celled protist that lives in aquatic environments. - It is usually slipper-shaped, with short hairy projections called cilia covering them. - Certain Paramecium strains are also easy to culture in the lab and can be utilised as model organisms. - Euglena is a single-celled flagellated microorganism with a whiplike appendage. - It is a microorganism with both plant and animal traits. - Euglena can be found in fresh and brackish water that is rich in organic matter, as well as moist soils. - Euglena has chlorophyll to make its own food. ### Algae - Are plant-like protists that are autotrophic, which means they produce their own food through photosynthesis. - They contain chlorophyll to capture sunlight. - Algae can be found in freshwater and marine ecosystems. - They help to provide oxygen and food for aquatic organisms. - Examples of algae include green algae, diatoms and seaweeds. ### Slime Moulds - Are fungus-like protists that are heterotrophic. - They do not have chlorophy and reproduce using spores. - They obtain nutrients by decomposing organic material and grow in moist environments. - During their reproductive phase, slime moulds can form spore-producing structures, which are often seen on decaying logs and leaf litter in forests. - Examples include cellular slime moulds and plasmodial slime moulds. ### Fungi - Do you know what grows on a rotten orange or a rotten bread? What causes this to happen? - Mould grows on a decaying orange and a rotten bread. - Mould is a type of fungi that lives on plant and animal matter, such as food to cause it to deteriorate and degrade. - Mould takes in the nutrients provided by the food, which allows it to grow, reproduce and multiply. - If you take in the contaminated food by accident, you may develop food poisoning, with symptoms that includes stomach aches, vomiting and diarrhoea. - Fungi can be single-celled organisms or multicellular organisms with a great deal of complexity. - They can be found in almost any habitat, but the majority of them reside on land, primarily in soil or plant material, rather than in the sea or fresh water. ### Yeasts - Are single-celled organisms. - They can cause fermentation of various fruits, plants and plant by-products since they thrive on organic compounds such as sugars. - Each yeast cell has a nucleus, cytoplasm, vacuoles and a membrane that is surrounded by a cell wall. - A yeast cell can reproduce via budding as shown in the diagram below. - These are fast-occurring phenomena that can easily be observed through a high-powered optical microscope. - Yeasts can be used to make baked foods as well as alcoholic beverages like beer and wine. - Yeast can also be dangerous and cause infections in a variety of ways. ### Moulds - Are multicellular cells. - They are made up of hyphae, which are very fine threads. - Hyphae form long, branching chains by growing at the tip and dividing periodically along their length. - The hyphae continue to develop and intertwine until they form a mycelium, which is a network of threads. - From the hyphal tip, digestive enzymes are released. - These enzymes break down organic materials in the soil into smaller molecules that the fungus consumes as food. ### Animals The animal kingdom can be divided into two groups which are vertebrates and invertebrates as shown in the chart below. The two groups can be further divided into smaller groups based on common characteristics. ### Vertebrates - Have backbones - They are divided into five groups: mammals, amphibians, reptiles, fish and birds. - **Mammals** - They have hair on their body. - They breathe with lungs. - They give birth to live young and nurse their young. - They are warm-blooded. - They, except whales, have four limbs with claws, nails or hooves. - Examples: bat, whale, hippopotamus - **Amphibians** - Generally, they have smooth, moist skin without any coverings. However, certain species of salamanders and newts have rough or bumpy skin. - Adults breathe with lungs and moist skin on land while the young breathe with gills in water. - They lay eggs, usually in a jelly-like mass in the water. - They are cold-blooded. - They have four legs without claws or nails on their toes. - Examples: salamander, frog, toad - **Reptiles** - They are covered with scales. - They breathe with lungs. - They lay eggs with leathery shells. Some species give birth to fully-formed young. - They are cold-blooded. - They have no legs or have four legs with clawed toes. - Examples: turtle, snake - **Fish** - They have fins, tails and streamlined bodies to help them move in water. - They are covered with scales or smooth, leathery skin. - They live in water and breathe with gills. - They are cold-blooded. - Examples: stingray, shark, seahorse - **Birds** - They have a beak or bill, two legs, hollow bones and two wings used for flying. - They are covered with feathers. - They breathe with lungs. - They lay eggs with a hard shell. - They are warm-blooded. - Examples: ostrich, penguin, owl ## Science Facts Have you ever seen a duck waddling about in the snow? Ducks do not require anything to keep their feet warm, their feathers are only for keeping their body warm. Since their feet lack nerves and blood vessels, their webbed feet are unable to sense the cold. ### Invertebrates - Do not have a backbone. - They may have shells outside their bodies or an external skeleton (exoskeleton) in the form of a hard outer covering of the body. - They are divided into two groups, invertebrates with jointed legs and invertebrates without jointed legs. - **Arthropods** are invertebrates that have jointed legs, segmented bodies and exoskeletons. - **Cnidarians**, **Echinoderms**, **Nematodes**, **Annelids**, **Platyhelminthes**, **Poriferans** and **Molluscs** are invertebrates without jointed legs. Some of them are worm-like and some are not. - **Arthropods** - They have jointed legs (three, four or more than four pairs of legs). Some have many legs. - They have segmented bodies. - They have exoskeletons. - Some of them have antennae and some do not. - Some have compound eyes and some have simple eyes or no eyes. - Examples: scorpion, crab, praying mantis, centipede - **Cnidarians** - They have tentacles to catch their food. - They do not have true organs. - They have jelly-like bodies. - Examples: jellyfish, sea anemone - **Echinoderms** - They have hard, spiny covering or skin. - Some feature a radial symmetry star-shaped pattern. - They have organs but no brains. - Examples: starfish, sea urchin - **Nematodes** - They have round, thin and unsegmented bodies. - They have organs. - Examples: roundworm, pinworm ## Plants In the plant kingdom, plants are divided into non-flowering and flowering plants. ### Non-flowering Plants The most primitive plants on the Earth are non-flowering plants. They can be divided into Bryophytes, Pteridophytes and Coniferophytes. - **Mosses and liverworts** are examples of Bryophytes. - They do not have true leaves, stems and roots. - The leaves and stems are usually small and simple. - They are usually found in damp places because they do not have a transport system for water and food. - They do not produce seeds or flowers, instead they reproduce by spores. - **Ferns** are an example of Filicinophytes without seeds. - They have strong stems, roots and leaves. - They have a transport system for water and food. - Ferns reproduce by making spores. These spores can be found on the underside of the leaves. - **Gymnospermae** are an example of Coniferophytes that produce seeds which are formed inside the cones. - They have true roots, stems and needle-like leaves. - They also have a transport system for water and food. - They do not produce flowers or fruit. ### Flowering Plants - Are plants that bear flowers and fruits. - They have a system for water and food. - They are angiosperms. - They reproduce by flowers. - The flowers produce fruits which contain seeds. - The seed consists of three parts, namely the plumule (embryonic shoot), the radicle (embryonic root) and the cotyledon (seed leaf). - A cotyledon is the part of a plant embryo that is the first to emerge from a seed. - **Monocotyledons** and **dicotyledons** are two groups of flowering plants, named based on the number of cotyledons in their seeds. - **Monocots** - Are not usually woody. Most of them are herbaceous plants. - They have leaves of parallel veins. - They have fibrous roots. - They produce seeds that have one cotyledon. - Examples: maize plant, banana tree, pineapple plant, coconut tree - **Dicots** - Are usually woody. - They have leaves of a network of veins. - They have taproots. - They produce seeds that have two cotyledons. - Examples: mango tree, tomato plant, sunflower plant, rose plant ## Science Facts Rafflesia is a parasitic flowering plant found in Indonesia, Malaysia, Thailand and the Philippines. It is the largest flower in the world and can grow as large as 100 cm across and weigh up to 7 kg.