The Nature and variety of living organisms IGCSE Biology

Syllabus a) Characteristics of living organisms Recall that living organisms share the following basic characteristics b) Variety of living organisms Understand that there is a wide variety of living organisms and that modern biology classifies organisms on the basis of their structure and how they function Describe the common features shared by organisms within the five main groups, plants, animals, fungi, bacteria and viruses and for each group describe examples and their features.

What are the differences between the living and non-living things on this page?

Characteristics of living things: M ovement R espiration S ensitivity G rowth R eproduction E xcretion N utrition The process by which living cells release energy from organic molecules The ability to detect and respond to changes in the environment either inside or outside the organism Creation of new organisms that are the same species as the parents Removal of wastes from the organism’s body. Supplies an organism with the food it needs to respire, grow, repair and reproduce. Change in position by the action of muscles in animals, and slow growth movements in plants Increase in size and mass

Classification Scientists classify organisms into categories (groups) to: –make it easier to study them –communicate with scientists from other country. Classified based on their structure and how they function

Classification Organized using a hierarchical system introduced by Carolus Linnaeus Seven taxa groups – Kingdom, Phylum, Class, Order, Family, Genus and Species Taxonomists study organisms to determine which group they will go in.

Classification Linnaeus also introduced the bionomial nomenclature system –This is where all living things were given two names written in Latin. –The first is the Genus name, always with a capital letter –The second is the species name, always small letter Example –Homo sapien (human) –Canis lupus (wolf) –Equus burchelli (zebra) When you write the scientific name of an organism you should either write it in italics (computer) or underline it (hand written)

Kingdoms 5 Kingdoms –Bacteria (Prokaryotae - includes bacteria and blue- green algae) Some scientists have separated this group into 2 different kingdoms –Protoctist (algae and protozoans) –Fungi –Plantae –Animalia Virus

Bacteria Examples – bacteria and cyanobacteria Unicellular (single-celled) or filamentous No nucleus Circular DNA (plasmid) Cell wall present Source of diagrams:

Protoctist Examples – algae, protozoans (Amoeba, Paramecium etc.) Unicellular or simple multicellular organisms Nucleus present Can photosynthesize or absorb food Source of diagrams:

Fungi Examples – yeast, mushroom, mould fungi Cell wall made of chitin Nucleus present No chlorophyll Absorb food Source of diagrams:

Plantae Examples – grasses, oak tree, dandelions, moss, conifers Multicellular Cell wall present Chlorophyll present = photosynthesis Source of diagrams:

Flowering Plants Monocotyledons –Eg. Grasses, iris –Parallel veins –Narrow leaves –1 leaf in the seed Dicotyledons –Eg. Sunflower, willow tree –Broad leaves –Veins branching –2 leaves in the seed Source of diagrams:

Other Plants Moss and liverworts –No xylem –No roots –Asexual and sexual stages to lifecycle Conifers –Needle-like leaves –Cone-bearing plants Ferns –Reproduce using spores Source of diagrams:

Animalia Examples – ants, horses, snails, humans, whales Multicellular Nucleus present, no cell wall Heterotrophic (cannot make their own food) Source of diagrams:

Virus Non-living and living Smallest –Smaller than bacteria Parasitic Reproduce inside a host Protein coat Contain either DNA or RNA strand

Arthropods Insects –3 body segments –3 pairs of legs –2 pairs of wings –antennae Crustaceans –More than 4 pairs of jointed legs –2 pairs of antennae –Breathe through gills Arachnids - 2 body segments - 4 pairs of legs - No wings - No antennae Myriapods - One pair of antennae - many segments of body - Many pairs of legs

Other invertebrates Annelids –Long segmented body covered with mucus –Chaetae (bristles) present Molluscs –Animals with soft, unsegmented body, may have shell –No limbs –Foot present Nematoda –Long thin bodies with no rings –No legs –No obvious head

Vertebrates Mammals –Live mainly on land –Have fur or hair –Mammary glands Birds (Aves) –Feathers –wings Fish (Pisces) –Gills –Skin covered with scales –fins Reptiles –Scaly skin (dry) Amphibians –Smooth, moist skin

Adaptations Bacteria –Eg. Flagellum, used to move –Single cell (less complex), so they can live in extreme conditions (can live in 60°C temperature of mineral hot-springs) Viruses –Eg. Very, very small so can easily be transferred to a host. –DNA free (not in nucleus), so can easily be copied within host cell and therefore more viruses can be made. Fungi –Eg. Hyphae used to grow through whatever the fungus is feeding on.

Used by scientists to identify unknown organisms Keys consist of a series of choices that lead the user to the correct name of a given item. "Dichotomous" means "divided into two parts". Therefore, dichotomous keys always give two choices in each step. Dichotomous keys