1 Characteristics of living organisms and classification .pdf

1 Characteristics and classification of living organisms 1.1 Characteristics of living organisms  We know that the dog running on the road is alive, however the broom being used to sweep the floor is not  Though the ability to distinguish between something that is alive or not is not...

1 Characteristics and classification of living organisms 1.1 Characteristics of living organisms  We know that the dog running on the road is alive, however the broom being used to sweep the floor is not  Though the ability to distinguish between something that is alive or not is not always so obvious  For example is a dried seed living or non-living  A virus, like the corona virus, that causes COVID-19, is it living or non-living  Biologists answer this question by using a list of characteristics that living organisms show  The characteristics of living organisms are 1. Movement 2. Respiration 3. Sensitivity 4. Growth 5. Reproduction 6. Excretion 7. Nutrition  The characteristics can easily be remembered using the mnemonic MRSGREN  The first letter of each of the characteristics is taken to make up the mnemonic Define the terms: 1. Movement is an action by an organism or part of an organism causing a change of position or place 2. Respiration is the chemical reactions that break down nutrient molecules in cells to release energy. There are two forms of respiration Aerobic Anaerobic Feature respiration respiration Amount of energy large little produced Oxygen used Yes No Please note that respiration is not breathing i. Breathing is the process of moving air into (inhalation) and out of (exhalation) the lung in order to facilitate gas exchange. ii. Breathing is not a characteristic of all living organisms. Plants do not breath. 3. Sensitivity is the ability to detect or sense changes in the internal or external environment and to make appropriate responses Note that The changes in the internal or external environment are called STIMULI (singular = stimulus) 4. Growth is a permanent increase in size and dry mass by an increase in cell number or cell size or both 5. Reproduction is the processes that make more of the same kind of organism An organism may simply split into two, or reproduction may be more complex, involving fertilization Reproduction makes new organism of the same species as the parent. 6. Excretion is removal from organisms of the toxic waste products of metabolism and substances in excess of requirements 7. Nutrition is taking in of materials for energy, growth and development Plants require light, carbon dioxide, water and ions and make their foods using a process called photosynthesis. This type of nutrition is called AUTOTROPHIC nutrition Animals need organic compounds and ions and usually need water and obtain their foods by eating other organisms This type of nutrition is called HETEROTROPHIC nutrition 1.2 Concept and use of a classification system  State that organisms can be classified into groups by the features that they share  Define species as a group of organisms that can reproduce to produce fertile offspring  Define and describe the binomial system of naming species as an internationally agreed system in which the scientific name of an organism is made up of two parts showing the genus and species  Explain that classification systems aim to reflect evolutionary relationships  Explain that classification is traditionally based on studies of morphology and anatomy  Explain that the sequences of bases in DNA and of amino acids in proteins are used as a more accurate means of classification  Explain that organisms which share a more recent ancestor (are more closely related) have base sequences in DNA that are more similar than those that share only a distant ancestor Each species of organism has different characteristics, and some of these characteristics can be inherited by successive generations. Observing these inherited characteristics allows scientists to put organisms into categories on the basis of their observable characteristics, this is called classification Classification is the process of sorting a variety of items into manageable groups. Explain why it is important to classify organisms.  By classifying organisms it is possible to identify those most at risk of extinction.  Strategies can then be put in place to conserve the threatened species.  potential sources of valuable products such as drugs.  By classifying organisms it is also possible to understand evolutionary relationships.  Vertebrates all have the presence of a vertebral column, along with a skull protecting a brain, and a pair of jaws (usually with teeth).  By studying the anatomy of different groups of vertebrates it is possible to gain an insight into their evolution.  E.g. The skeletons of the front limb of five types of vertebrate are shown 1. Name the animal to which the skeleton could belong a. _ _ _ _ _ _ _ _ _ _ _ _ _  b. ___ _______ c. _ _ _ _ _ _ _ _ _ _ _ _ d. _ _ _ _ _ _ _ _ _ _ e. _ _ _ _ _ _ _ _ _  Although the limbs have different functions, such as grasping, flying, running and swimming, the arrangement and number of the bones is almost the same in all five.  There is a single top bone (the humerus), with a ball and socket joint at one end and a hinge joint at the other.  It makes a joint with two other bones (the radius and ulna) which join to a group of small wrist bones.  The limb skeleton ends with five groups of bones (the hand and fingers), although some of these groups are missing in the bird.  The argument for evolution says that, if these animals are not related, it seems very odd that such a similar limb skeleton should be used to do such different things as flying, running and swimming.  If, on the other hand, all the animals came from the same ancestor, the ancestral skeleton could have changed by small stages in different ways in each group.  So we would expect to find that the basic pattern of bones was the same in all these animals. 2. Fill in the missing words Classification is traditionally based on studies of _ _ _ _ _ _ _ _ _ _ _ _ _ (the study of the form, or outward appearance, of organisms) and _ _ _ _ _ _ _ _ _ _ _ _ (the study of their internal structure, as revealed by dissection). Organisms which are more closely related have DNA that are more similar than those that share a distant ancestor Eukaryotic organisms (.................................................................) contain chromosomes made up of strings of genes. The chemical which forms these genes is called DNA (which is short for deoxyribonucleic acid). The DNA is made up of a sequence of bases, coding for amino acids and, therefore, proteins Each species has a distinct number of chromosomes 3. Complete the table by filling in the number of chromosomes found in the cells of : a. Man and b, Chimpanzee Hint: Read lower down No. of you may find the Animal chromosomes appropriate responses Cat 38 Dog 78 Onion 16 Man a. Chimpanzee b. and a unique sequence of bases in its DNA, making it identifiable and distinguishable from other species. This helps particularly when different species are very similar morphologically (in appearance) and anatomically (in internal structure). Organisms which have many of the same features are normally descended from common ancestors The more features shared by different organisms the more recently they will have separated from one another The process of biological classification called cladistics involves organisms being grouped together according to whether or not they have one or more shared unique characteristics derived from the group‟s last common ancestor, which are not present in more distant ancestors. Organisms which share a more recent ancestor (and are, therefore, more closely related) have DNA base sequences that are more similar than those that share only a distant ancestor. Human and primate evolution is a good example of how DNA has been used to clarify a process of evolution. Traditional classification of primates (into monkeys, apes and humans) was based on their anatomy, particularly their bones and teeth. This put humans on a separate branch, while grouping the other apes together into one family called Pongidae. Evidence using DNA analysis provides a different insight Humans are more closely related to chimpanzees there is a 1.2% difference in the DNA Gorillas show a 1.6% different difference in DNA with humans Whilst orang-utans show a 3.1% difference in DNA with humans Also, chimpanzees are closer to humans than to gorillas. Bonobos and chimpanzees are found in DRC and were only identified as different species in 1929. The two species share the same percentage difference in the genome from humans. When molecules of DNA are used to classify species, only one of the two DNA strands is sequenced. First the DNA sequence from one strand of a DNA molecule from each species is lined up against one strand from another species. The bases of the DNA sequences from the same strand can then be compared with each other. The diagram below shows a short section from the DNA sequences of eight plant species Notice that there are ten differences between species A and species B. These differences are shown by boxes drawn across the regions where the differences occur. Count the number of differences between the DNA sequences shown for: a) species C and species D ……………….. b) species G and species H ……………….. Classification Keys or Dichotomous keys People who study the classification of organisms are called taxonomists In order to group organisms having the same characteristics together, taxonomists ask questions about the characteristics of the organisms Such as “” Does the organisms have many cells” Only two possible responses to each question are permitted Yes…………………. Go to 5 No………………….. Go to 2 The response to the question will then direct you to another question, again with two responses, Yes or No The process is repeated until all the organisms have been sorted in groups having similar features. 4. The diagram shows part of a flowering plant. Using the key, identify this plant. 1 three petals................................................. go to 2 more than three petals............................... go to 3 2 leaves longer than they are wide................ A leaves wider than they are long.................. B 3 leaves parallel-veined................................. C leaves not parallel-veined........................... D Sometime the dichotomous key can be represented in the form of a diagram as shown in the question below 5. The diagram shows a leaf. Use the key to identify the plant to which the leaf belongs. Notice that in the question above the names of the plants are written in italics Also notice that the names are not English 6. In what language are the names written? …………………………………………… 7. Also notice the number of names each of the plants A,B,C and D have = ……………….. Each of the plants has been given a scientific name, called a Binomial All organisms are named using the BINOMIAL SYSTEM The BINOMIAL SYSTEM consists of two names 1. Genus 2. Species Both names are Latin or Latinized The Genus is always written beginning with a capital letter The species is always written beginning with a small letter A species is a group of morphologically similar individuals, that can reproduce together to produce fertile offspring. Features of organisms All living organisms have certain features in common, all living organisms are made up of................... and therefore all contain a...........................,.................................................., and......................................................................... They also contain........................................ in the........................................., these are free floating proteins, or they may be attached to membranes called........................................................................................................................ (...........). Ribosomes are responsible for protein synthesis. Proteins make up the structures of cells and the enzymes in the cytoplasm. Viruses are not living organisms Viruses are not included in any kingdom Viruses are not considered to be living organisms because they................................................................................................................................................................................................................................................ They do not demonstrate the characteristics of living things: they do not..........................,..........................,.............................. or........................................ Although viruses do..................................., this only happens inside the cells of living organisms, using materials provided by the host cell. Viruses are small particles, smaller than bacteria They infect every type of living organism They have a wide variety of shapes and sizes They have no cellular structure but have a protein coat and contain one type of nucleic acid, either DNA or RNA Generalized Diagram of a virus Examples include the tobacco mosaic virus, the influenza virus (causes „flu‟) and the HIV virus (causes AIDS) tobacco mosaic virus influenza virus HIV The hierarchy of classification system Classification systems aim to group organisms in to groups of............................................. feature. Plants Multicellular organisms Their cells contain chloroplasts- able to carry out photosynthesis Their cells have cellulose cell walls They store carbohydrates as starch They have roots, stem and leaves Examples include flowering plants, such as a cereal (for example maize), and a herbaceous legume (for example peas or beans) Animals These are multicellular organisms They have no cell walls They usually have nervous coordination and are able to move from one place to another They often store carbohydrate as glycogen Examples include mammals (for example humans) and insects (for example mosquito) Fungi Usually organised into a mycelium made from thread-like structures called hyphae, which contain many nuclei Some examples are single-celled Their cells have walls made of chitin They feed by extracellular secretion of digestive enzymes onto food material and absorption of the organic products (saprotrophic nutrition) They may store carbohydrate as glycogen Examples include Mucor (hyphal example) and yeast (single cell example) Prokaryota/ Bacteria These are microscopic single-celled organisms They have a cell wall, cell membrane, cytoplasm and plasmids They lack a nucleus They contain a circular chromosome of DNA Some bacteria can carry out photosynthesis but most feed off other living or dead organisms Examples include Lactobacillus bulgaricus (used in the production of yoghurt from milk) and Pneumococcus (pathogen causing pneumonia) Protoctists These are microscopic single-celled organisms Some, like Amoeba, that live in pond water, have features like an animal cell Some like Chlorella, have chloroplasts and are more like plants A pathogenic example is Plasmodium, responsible for causing malaria Vertebrates  are animals which have a vertebral column.  The vertebral column is sometimes called the spinal column or just the spine and consists of a chain of cylindrical bones (vertebrae) joined end to end.  Each vertebra carries an arch of bone on its dorsal (upper) surface. This arch protects the spinal cord which runs most of the length ofthe vertebral column.  The front end of the spinal cord is expanded to form a brain which is enclosed and protected by the skull.  The skull carries a pair of jaws which, in most vertebrates, have rows of teeth.  The are five classes of vertebrates  1. ………………………………………………… 2. ………………………………………………… 3. ………………………………………………… 4. ………………………………………………… 5. ………………………………………………… Body temperature  Fish, amphibia and reptiles are often referred to as „cold-blooded‟. This is a misleading term. A fish in a tropical lagoon or a lizard basking in the sun will have warm blood.  The point is that these animals have a variable body temperature which, depends on the temperature of their surroundings.  Reptiles, for example, may control their temperature by moving into sunlight or retreating into shade but there is no internal regulatory mechanism. It is better to use the terms poikilothermic (variable temperature).  So-called „warm-blooded‟ animals, for the most part, have a body temperature higher than that of their surroundings. The main difference, however, is that these temperatures are kept more or less constant despite any variation in external temperature.  There are internal regulatory mechanisms which keep the body temperature within narrow limits. . It is better to use the terms homoiothermic (constant temperature).  The advantage of homoiothermy is that an animal‟s activity is not dependent on the surrounding temperature. A lizard may become sluggish if the surrounding temperature falls. This could be a disadvantage if the lizard is being pursued by a homoiothermic predator whose speed and reactions are not affected by low temperatures. Fish  are poikilothermic (cold blooded) vertebrates.  have a smooth, streamlined shape which offers minimal resistance to the water through which they move  bodies are covered with overlapping scales  they have fins which play a part in movement.  breathe by means of filamentous gills which are protected by a bony plate, the operculum.  Fish reproduce sexually but fertilisation usually takes place externally; the female lays eggs and the male sheds sperms on them after they have been laid. Amphibia  The name, amphibian, means „double life‟ and refers to the fact that the organism spends part of its life in water and part on the land.  are poikilothermic (cold blooded) vertebrates  no scales.  body covered in smooth, moist skin  usually have lungs but they can also absorb oxygen through their moist skin.  they have four limbs  Reptiles  Reptiles are poikilothermic (cold blooded)  they have a dry, scaly skin that resists water loss  Most reptiles have four legs, although snakes have lost theirs. Birds  Body covered in feathers  Have wings  Have a beak  Lay eggs that have a hard calcareous shell  2. State the main features used to place organisms into groups within the animal kingdom, limited to: b) the main groups of arthropods: myriapods, insects, arachnids, crustaceans  In this section we are introduced to the Invertebrates  Invertebrates = animals without a back bone  Invertebrates include the worms, snail and the Arthropods  In this section will shall concentrate on the Arthropods Arthropods  Arthropods are invertebrate animals that: i. have an exoskeleton ii. have jointed limbs  exoskeleton = hard, firm external skeleton, which encloses their bodies.  Their bodies are segmented  between the segments, there are flexible joints which permit movement  There are 4 arthropod classes i. Insects ii. Arachnids iii. Crustacea iv. Myriapods Insects  body divided into 3 segments, Head thorax and abdomen  The abdomen is divided into segments and has no limbs on it  they have three pairs of jointed legs or they have 6 jointed legs  on the head, they have one pair of antennae  They usually have wings may have two pairs, one pair, some insects have no wings on the thorax Arachnids These are the spiders 1. body divided into two regions, the cephalothorax and the abdomen mite 2. They have four pairs of limbs on the cephalothorax or They have 8 legs 3. on the cephalothorax they have another pair of limbs called the pedipalps Spiders use the pedipalps as sensory organs (kinda like antennae) 4. they have chelicerae = pincerlike mouth parts The chelicerae are use to pierce their prey and paralyse it with a poison secreted by a gland at the base. Spider Tick Scorpion Crustacea  body is divided into two parts cephalothorax and abdomen.  They have two pairs of antennae  They have more than 4 pairs of jointed legs  have a pair of jointed limbs on each segment of the body, but those on the head segments are modified to form antennae or specialised mouth parts for feeding Myriapods  body not obviously divided into thorax and abdomen  body has many segments  ten or more pairs of legs  usually one pair of legs per segment  one pair of antennae  simple eyes