10 Biodiversity Support. AQA Biology. Biodiversity. Specification reference. Learning objectives. Introduction. Background

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Dinah Dixon
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1 Biodiversity Specification reference Learning objectives After completing this worksheet you should be able to: recall the definition of a species and know how the binomial system is used to name organisms interpret examples of hierarchical classification systems understand how modern molecular methods contribute to working out evolutionary relationships understand the terms biodiversity and species richness calculate an index of diversity. Introduction There is a huge variety of life on Earth, and biologists have classified organisms using different systems over the centuries. You will learn about the currently accepted classification system and find out how organisms are placed into groups. The terms biodiversity and species richness will be introduced, and methods for investigating genetic diversity will be explained. Background In order to study organisms and the possible evolutionary relationships between them, biologists must have an agreed and reliable classification system. In the currently accepted system, organisms are first divided into large groups. These are then further divided into smaller and smaller groups. The groups are called taxa and are based on shared characteristics. This system is known as hierarchical because the taxa fall into different levels. You will not be required to remember any classification system, but you do need to be able to interpret examples. Currently accepted classification The classification system that has been in use since 1990 divides organisms into the following groups: domain kingdom phylum class order family genus species This resource sheet may have been changed from the original 1

2 You must be careful about using words like family or class when writing exam answers about groups of organisms, as they have special meanings in this context. Use the word taxa to mean groupings. The domain is the largest group with the most organisms. For example, one of the three domains is called Eukarya which includes all the types of organisms with eukaryotic cells. The species is the smallest group containing just one type of organism, each species being unique. Therefore a classification, tree is narrow at the top (three domains) and very wide at the base (all the different species). Species and naming organisms Organisms are said to be in the same species if they can reproduce to give fertile offspring. Most organisms are named using an internationally agreed binomial (meaning two name) system in the form Genus species. For example the lion is named Panthera leo because it is in the Panthera genus and its species is leo. It would be possible to list all the taxa for the lion, for example its domain is Eukarya (it has eukaryotic cells), its kingdom is Animalia (it is an animal), its phylum is Chordata (it is a vertebrate), its class is Mammalia (it is a mammal), its order is Carnivora (it is a carnivore) and its family is Felidae (it is in the cat family). Modern classification methods Besides looking at appearance, behaviour, and adaptations to their habitats, biologists now use other methods to classify and study relationships between organisms. Biologists believe that the more closely related two organisms are, then the more recently they shared a common ancestor. These modern methods include comparisons of: DNA nucleotide sequences of their entire genomes DNA nucleotide sequences of certain genes RNA nucleotide sequences amino acid sequences of shared proteins the antigens found on cells. One of the proteins often used for comparison is called cytochrome C because it is found in so many different types of organisms. Sampling methods In order to study organisms, whether to measure their distribution in their environment, or to collect DNA samples for analysis, they have to be sampled. In order to provide reliable data, the sampling must be random. This could involve the random placing of quadrats using a previously prepared coordinate system, or setting some sort of trap (that does not harm the organisms) in random locations. Numerical data that are collected are analysed statistically by calculation, first of the mean, then the standard deviation. This resource sheet may have been changed from the original 2

3 Biodiversity This is a measure of the variety of organisms in a particular area. Simply put, it is the variety of life in that area, which could be measured as genetic variation or number of species. You need to be able to work out a diversity index, d, using the formula: where: N = total number of organisms of all species n = total number of organisms or a particular species The higher the value of d, the greater the biodiversity. Farming, especially intensive crop cultivation, reduces biodiversity. Worked example of diversity index The numbers of insects of different species in a field were recorded. The results are shown in the table. species number of insects A 54 B 0 C 32 D 146 E 0 Use the results to work out the diversity index. Method use the formula work out N, total number of organisms in all species = = 232 the top line of the formula is 232 (232 1) = = for the bottom line, we need to work out n(n 1) for each species and add them: o = 2862 o = 992 o = o total = = finally, d = = 2.14 answer = 2.14 This resource sheet may have been changed from the original 3

Species richness This is a measure of the number or different species in a particular ecosystem. It takes no account of the relative numbers of each species or where they are distributed.

4 Species richness This is a measure of the number or different species in a particular ecosystem. It takes no account of the relative numbers of each species or where they are distributed. Questions 1 The olinguito is an animal newly discovered in The olinguito lives in trees in the Andes mountains. It is a carnivore. a In the currently accepted classification system, one of the groups is class. Give one piece of evidence from the information given, that the olinguito should be placed in the mammal class. b The olinguito is similar in appearance to a type of racoon that has already been classified. Describe how biologists could determine whether the olinguito was in the same species as the racoon. c The sloth is another animal that lives in trees. Describe how biological molecules could be used to determine how closely related the sloth and the olinguito are in evolutionary terms. (4 marks) 2 The diagram shows part of the phylogenetic, or evolutionary, tree for fish. The closer to the top of the tree, the more recent the timescale. This resource sheet may have been changed from the original 4

5 a Name the most recent common ancestor for: i the tuna and the halibut ii the cod and the squirrelfish. b Name the fish that share the most recent common ancestor. c The Teleostei first evolved around million years ago. How do we know this? 3 a A group of students carried out an investigation into the variety of plant species in a field. i State what is meant by the term species richness. ii They decide to use a quadrat to sample the species. One of the students decides to place the quadrat alternately in areas where there is first high and then low diversity of plants. Explain whether this is a reliable strategy. iii Suggest how they could identify unfamiliar plants. b Their results are shown in the table. plant species number of plants daisy 39 plantain 24 clover 248 buttercup 17 i Use the formula to calculate the diversity index for the plants in this field. Show your working. ii The students compared their results with another group who did the same investigation six months previously. The way the field was used had not changed in that time, yet their results were very different. Suggest reasons for the differences. c Explain why using land for intensive crop culture reduces biodiversity. (3 marks) (3 marks) This resource sheet may have been changed from the original 5

Classification Revision Pack (B2)

Classification Revision Pack (B2) Grouping Organisms: All organisms (living things) are classified into a number of different groups. The first, most broad group is a kingdom. The last, most selective group is a species there are fewer