Biology - Characteristics, Classification, & Features of Organisms PDF

Unit 1 - Characteristics, Classification & Features of Organisms 1.1 Characteristics of Living Organisms MRS GREN Movement: an action by an organism or part of an organism causing a change of position or place Respiration: the chemical reactions that break down nutrient molecules in livi...

Unit 1 - Characteristics, Classification & Features of Organisms 1.1 Characteristics of Living Organisms MRS GREN Movement: an action by an organism or part of an organism causing a change of position or place Respiration: the chemical reactions that break down nutrient molecules in living cells to release energy for metabolism Sensitivity: the ability to detect or sense stimuli in the internal or external environment and to make appropriate responses Growth and development: a permanent increase in size and dry mass by an increase in cell number or cell size or both Reproduction: the processes that make more of the same kind of organism Excretion: the removal from organisms of toxic materials,the waste products of metabolism (chemical reactions in cells including respiration) and substances in excess of requirements Nutrition: the taking in of materials for energy, growth and development; plants require light, carbon dioxide, water and ions; animals need organic compounds, ions and usually need water 1.2 Concept & Uses of Classification Systems How Organisms are Classified There are millions of species of organisms on Earth A species is defined as a group of organisms that can reproduce to produce fertile offspring These species can be classified into groups by the features that they share e.g. all mammals have bodies covered in hair,feed young from mammary glands and have external ears (pinnas) The Binomial System Organisms were first classified by a Swedish naturalist called Linnaeus in a way that allows the subdivision of living organisms into smaller and more specialised groups The species in these groups have more and more features in common the more subdivided they get He named organisms in Latin using the binomial system where the scientific name of  an organism is made up of two parts starting with the genus (always given a capital letter) and followed by the species (starting with a lowercase letter) When typed binomial names are always in italics (which indicates they are Latin) e.g. Homo sapiens The sequence of classification is: Kingdom, Phylum, Class, Order, Family, Genus, Species Dichotomous Keys Keys are used to identify organisms based on a series of questions about their features Dichotomous means ‘branching into two’ and it leads the user through to the name of the organism by giving two descriptions at a time and asking them to choose Each choice leads the user onto another two descriptions in order to successfully navigate a key You need to pick a single organism to start with, or you may be presented with an unfamiliar one as part of an exam questions Follow the statements from the beginning. Each statement or question you should be able to answer using the information provided in the question or an image given as part of the question. Eventually there will be no more statements or questions left and you will have the name of the organism. You then pick another organism and start at the beginning of the key again, repeating until all organisms are named Using DNA to Classify Organisms (extended) Organisms share features because they originally descend from a common ancestor. Example: all mammals have bodies covered in hair, feed young from mammary glands and have external ears (pinnas). Originally, organisms were classified using morphology (the overall form and shape of the organism, e.g. whether it had wings or legs) and anatomy (the detailed body structure as determined by dissection) As technology advanced, microscopes, knowledge of biochemistry and eventually DNA sequencing allowed us to classify organisms using a more scientific approach Studies of DNA sequences of different species show that the more similar the base sequences in the DNA of two species, the more closely related those two species are (and the more recent in time their common ancestor is) This means that the base sequences in a mammal’s DNA are more closely related to all other mammals than to any other vertebrate groups 1.3 Features of organisms The Five Kingdoms The first division of living things in the classification system is to put them into one of five kingdoms. Animals Plants Fungi Protoctists Prokaryotes Main features of all animals: they are multicellular their cells contain a nucleus but no cell walls or chloroplasts they feed on organic substances made by other living things Main features of all plants: they are multicellular their cells contain a nucleus, chloroplasts and cellulose cell walls they all feed by photosynthesis Main features of all fungi: (e.g. moulds, mushrooms, yeast) usually multicellular cells have nuclei and cell walls not made from cellulose do not photosynthesize but feed by saprophytic (on dead or decaying material) or parasitic (on live material) nutrition Main features of all Protoctists: (e.g. Amoeba, Paramecium, Plasmodium) most are unicellular but some are multicellular all have a nucleus, some may have cell walls and chloroplasts meaning some protoctista photosynthesise and some feed on organic substances made by other living things Main features of all Prokaryotes: (bacteria, blue-green algae) often unicellular cells have cell walls (not made of cellulose) and cytoplasm but no nucleus or mitochondria The Animal Kingdom Several main features are used to place organisms into groups within the animal kingdom Vertebrates All vertebrates have a backbone  There are 5 classes of vertebrates Invertebrates Invertebrates do not possess a backbone One of the morphological characteristics used to classify invertebrates is whether they have legs or not All invertebrates with jointed legs are part of the arthropod phylum The Plant Kingdom (extended) At least some parts of any plant are green, caused by the presence of the pigment chlorophyll which absorbs energy from sunlight for the process of photosynthesis The plant kingdom includes organisms such as ferns and flowering plants Ferns Have leaves called fronds Do not produce flowers but instead reproduce by spores produced on the underside of fronds Flowering plants Reproduce sexually by means of flowers and seeds Seeds are produced inside the ovary found at the base of the flower Can be divided into two groups – monocotyledons and dicotyledons How do you distinguish between monocotyledons and dicotyledons? Flowers Flowers from monocotyledons contain petals in multiples of 3 while flowers from dicotyledons contain petals in multiples of 4 or 5 Leaves Leaves from monocotyledons have parallel leaf veins while leaves from dicotyledons have reticulated leaf veins Leaves from monocotyledons are narrow and grass-like while leaves from dicotyledons tend to have broad leaves that come in a wide range of shapes Viruses Viruses are not part of any classification system as they are not considered living things They do not carry out the seven life processes for themselves, instead they take over a host cell’s metabolic pathways in order to make multiple copies of themselves Virus structure is simply genetic material (RNA or DNA) inside a protein coat