Forensic Anthropology Forensic Science

Transcription

1 Forensic Anthropology Forensic Science A Closer Look At Bones Science Unit Years 9/10

2 Forensic Science Unit: Forensic Anthropology Years 9/ weeks Forensic anthropology is about obtaining evidence from bones, which can be used in investigating crimes. Pupils will be familiar with some procedures through watching crime investigation programmes on television. This unit explores bones, their structure and make up in different types of skeletons. It looks at how the information contained in bones can be used for identification purposes and give clues about the deceased person s lifestyle. This is quite a long unit teachers may choose to leave out some of the key questions, or choose an order more appropriate for their class. Key Questions What is the human skeleton like? What are other skeletons like? What information can the skeleton give us about a person? What is the structure of bone? What are bones made of? How are the bones different? How can forensics teams identify a person when the skeleton is incomplete? How can forensics teams tell the height of a person from only one bone? Would you consider a career in forensics? Developing Pupils Knowledge, Understanding and Skills Develop creative and critical thinking in their approach to solving scientific problems. Links with Other Learning Areas / Subject Strands Maths This unit contains mathematical calculations including use of formula. Develop a range of practical skills, including the safe use of science Art equipment. Possible collaboration in terms of figure drawing. Learn about: Organisms and Health Exploring roles of forensic artist, sculptor and photographer. Developing Pupils Thinking Skills and Personal Capabilities The main focus in this unit is on developing skills in Thinking, Problem-Solving and Decision-Making o Generating questions o Identifying a range of options and making choices o Finding patterns o Identifying similarities and differences o Linking cause and effect. There are also opportunities to develop the other Thinking Skills and Personal Capabilities.

3 What is the human skeleton like? Setting the scene: Newspaper article/video clip about human remains being found. Example below from BBC NEWS. Discussion activity What do pupils know about this type of scenario, for example, from their viewing of crime programmes on television? Pupil responses could be recorded using a mind map. Simulation activity Crime lab. Gather the pupils around a model skeleton on the table (wearing lab coats if possible). Discuss what happens at this stage of an investigation. What are the different roles of the investigators? to generate questions. Thinking, Problem-Solving, Decision- Making. about bones making up the human skeleton. What questions need to be answered? Pupils work in small groups to generate questions that need to be answered. Groups compare and share their questions. The most common and interesting ones are recorded on thought boards. Looking closer at human skeleton In their own words, pupils describe the structure of the human skeleton. Make a list of ten observations. Pupils examine human skeleton models. Using unlabelled skeleton diagrams showing front and rear views, pupils identify bones that they can name and label these on the diagrams.

4 What are other skeletons like? to compare and contrast Thinking, Problem-Solving and Decision-Making Pupils examine the skeleton of a four legged mammal such as a rabbit or cat. a) Apart from size, in what are the ways does it differ from a human skeleton? b) Explain these differences in terms of function and adaptation. Pupils examine the skeletons of other vertebrates such as a bird, frog and fish. a) How do they differ from each other? b) Relate the structure of the skeleton to the kind of life the animal leads.

5 What information can the skeleton give us about a person? about how to look for evidence to make a decision/prediction. Gender Is the skeleton a Jane Doe or a John Doe Can a skeleton be male or female? What are the clues? (Possibly clip from a forensic science programme or a crime photograph). The sex of a skeleton can be determined in several ways by examining different parts. Most of these differences are due to changes which occur at puberty. The difference in hips is very obvious, as a male's hip are narrower and a female's hips are wider, being built for child bearing. Another way is by examining the skull. Males have a sloping forehead while females have a straighter forehead. Pupils look at the skulls of their classmates to see if they notice this feature. Males have a more square jaw bone while in females it is more V-shaped. Males also have more pronounced brow bones.

6 Age What age was the person? How can we tell? How do teeth change over time? How do bones change over time? What information can the bones give us? Can you tell what injuries the person suffered when they were alive? Teeth Young children will have not lost their milk teeth. Between the ages of 14 and 18, wisdom teeth start to appear. With age there is wearing of the teeth. Bone During the teenage years, bones become thicker and larger and fuse together in a process known as 'ossification'. The bone in the body that finishes growing last is the collarbone, which ceases growth at 28 years. In the bones of the elderly, degeneration begins to occur. Pupils summarise the information gleaned from the skeleton and predict what the possible causes of death could have been.

7 What is the structure of bone? about the structure of a bone. Bones tend to be classified by their shape. Long bones are found in the limbs and tend to be long relative to their diameter with some curvature to give them strength. Each has a shaft (diaphysis) and two enlarged ends (epiphyses). Safety Any bones which students are to handle must be cleaned and sterilised in advance by teacher/lab technician. Remove as much flesh as possible with a sharp knife. Place bones in a beaker of water and a little sodium carbonate. Simmer (do not boil) until the rest of the flesh is easily removed. Return to beaker and simmer for a few more minutes. Use an old nylon tooth brush or pan scourer to remove flesh. Eye protection should be worn if bones or cartilage are being cut. Hand washing is essential after the investigation. Follow CLEAPSS Laboratory Handbook guidelines (Section 14), CLEAPSS CD-Rom. In this investigation, the structure of a long bone is examined. Ask pupils to : o List the long bones in the human skeleton. o Suggest two reasons why the ends might be enlarged. Show the pupils a long bone cut in half down the middle. Note that the diaphysis encloses the marrow cavity. Questions for pupils: Why do you think long bones are hollow? o What does the marrow look like? o What is the function of the marrow? o The diaphysis is composed of dense bone tissue. What is the thickness of this tissue in millimetres? (opportunity to use callipers for bone measurements)

8 Examine the epiphyses of the long bone. Note that it is filled with a spongy bone. The spongy bone is formed from a network of plates or trabeculae, which produce a honeycomb structure. o What is the thickness of the dense bone at the epiphyses? o What is the advantage of the spongy bone in the epiphyses? Extension: Teacher carefully slices a thin layer of the spongy bone for pupils to examine under a microscope. Alternatively, purchased pre-prepared slides may be used. Take a dry stick about 50cm long. Place one end on the floor and press down on the other end until the stick bends and breaks. From what the pupils observed in breaking the stick, they suggest a reason for the differences between it and a bone. They can use the information from their answers to the earlier questions. If present on the bone, point out and explain the functions of cartilage, tendons and ligaments. Otherwise, a model such as one of the knee joint could be used. Following from this investigation, discuss the different injuries that affect bones and joints.

9 What are bones made of? that calcium is needed for strong bones. to make links between cause and effect. Thinking, Problem-Solving, Decision- Making An Investigation into Bone Composition Bones contain the compound Calcium Carbonate. Pupils observe what happens when a lump of Calcium Carbonate is placed in vinegar. Use clean whole long bones from chicken wings. Take a bone and try to break it. Were you able to bend the bone? Was it easy or hard to break? Place a bone into a beaker of vinegar and leave for 5-7 days. Pour off the vinegar, rinse the bone in water and examine it. Describe any change in the bone since it was left in the vinegar. Try bending the bone. What do you notice? Is it possible to tie a knot in the bone? Suggest a hypothesis for the change in the bone. As an alternative or further activity, use an egg instead of bone. The vinegar will react with Calcium Carbonate in the shell. This would take hours rather than days. (If a hard boiled egg is used, it reduces the risk of messy breakages). Having completed this investigation, consider the following questions: What substances are essential in the diet for the development of healthy bones? What foods are good sources of these substances? What could make bones unhealthy? Are there any diseases that affect bones?

10 How are the bones different? to identify similarities and differences Thinking, Problem-Solving and Decision-Making Pupils discuss possible ways of classifying the different types of bones in the skeleton. They could be given cards with pictures of different bones and asked to sort them into three groups. Pupils consider: the characteristics of each bone; how they will group them into categories; which ones fit best into the different categories; and what additional information might be needed before putting them into a particular category. about the functions of these bones. to make links between cause and effect. Thinking, Problem-Solving and Decision-Making to identify similarities and differences. Thinking, Problem-Solving and Decision-Making Pupils relate the structure of a skeleton to its function. This could be achieved through group/class discussion with guidance as necessary, for example: Which of these bones: a) Hold the body up? b) Are involved in movement? c) Protect the soft organs? Pupils could colour code their diagrams to show which bones are involved in each of the above functions. Compare the shoulders and hipbones. a) What do these have in common? b) In what ways do they differ? c) Can you explain the differences?

11 Examine the hand and foot in detail. In what way are these structures suited to their jobs? Examine and describe a vertebra in detail. What do pupils think are the functions of the vertebrae? Are pupils surprised at the number of bones that make up the back? Are there any advantages in having many bones like this rather than one long one? The human backbone has been described as being mechanically like a skyscraper. It has also been described as being more like the leaning tower of Pisa. Which description do pupils think is more accurate and why?

12 How can forensics teams identify a person when the skeleton is incomplete? Different parts of the body are in proportion to each other. This is reflected in the bones as well. Knowing the length of one bone, especially long bones like the femur, forensic scientists can estimate the height of a person. What other occupations need to know about body proportions? (Examples include artists, fashion designers, clothes production, medical doctors, etc.)... about identifying a range of options and making choices. Thinking, Problem-Solving and Decision-Making to record measurements accurately using appropriate units. Pupil generated model Pupils predict possible relationships between the sizes of different parts in the body, for example, height and arm span are equal lengths. Pupils measure some or all of the following in centimetres(cm): Total height Length of foot Ankle to hip Knee to ankle = tibia Length of thigh = femur Length of arm (wrist to shoulder) Length of forearm (wrist to elbow) = radius Length of upper arm (elbow to shoulder) = humerus Index finger Circumference of wrist Circumference of neck Circumference of leg (just above the knee) Arm span (finger tip to finger tip) Width of back (shoulder to shoulder) Opportunity to assess Using Mathematics

13 to look for and find patterns in numerical data. Thinking, Problem-Solving and Decision-Making Pupils should tabulate results for boys and girls separately (due to different proportions between the different sexes). They could record these measurements on a spreadsheet. Opportunity to assess Using ICT Ask the students if they see any relationships between the measurements. Are any of the numbers similar? What information can be extracted from these statistics? What questions do they stimulate? Plot a graph between two different body measurements, for example, height to arm span, hand to face or height to face. Ask pupils to analyse their results to see if they support their hypothesis. Give reasons to justify their conclusion(s). Are all bone measurements proportional to total height? Could pupils build a mathematical model to describe this? Could this model be used to determine height, if only one bone is recovered from a crime scene? Opportunity to assess Using Mathematics

14 How can forensics teams tell the height of a person from only one bone? to use mathematical formula in solving forensics problems. Forensic scientists use mathematical models to determine total height for a person when alive with information from the skeleton or isolated bones. The bones that are used are the femur (F), the tibia (T), the humerus (H), and the radius (R). Where in the body are these bones? Locate them on a model skeleton. The following formulae* can be used to determine the height, h. Measurements are in centimetres (cm). Male Female h = F h = F h= T h = T h= H h = H h= R h = R After the age of thirty, the height of a person begins to decrease at the rate of approximately 0.06 cm per year. This shrinkage must be considered when the age of the victim is known. Working out the height of a crime victim makes identification of the person more likely. Use the above formulae to work out the following: Forensic Science Problems 1. The femur of a 25-year-old male measured 49.7 cm. What was the height of the person? 2. The tibia of a 32-year-old female measured 33.5 cm. What was the height of the person? 3. Pupils use the formulas to calculate the lengths of their own femur, tibia, humerus, and radius. Opportunities to assess Using Mathematics * Formulae taken from: George Knill, Mathematics in Forensic Science, Mathematics Teacher, February: 31-32

15 Would you consider a career in forensics? about careers involving forensic science. to generate own questions for different purposes. Thinking, Problem-Solving and Decision-Making Forensic artists can create a life-like reconstruction of a human face using modelling clay built up on a skull. If a model of skull is available, pupils could attempt to do this using plasticine. Alternatively, they could watch a video/programme extract showing the process. Useful resources: Pupils reflect on the questions that they generated at the start of this unit. They group them under the headings answered and not yet answered. They select one or more not yet answered questions for further research/extension activities. Make pupils aware that some of their questions may not have answers. Further research could involve inviting a speaker to the classroom for a question and answer session. Contact the local forensic science branch of the police department or the coroner s office to see if they would be available to do this. Pupils prepare questions ahead of the visit. Useful Resource:

16 Development of Learning Outcome Demonstrate a range of practical skills in undertaking experiments, including the safe use of scientific equipment and appropriate mathematical calculations. Show deeper scientific understanding by thinking critically and flexibly, solving problems and making informed decisions, Using mathematics and Using ICT where appropriate. Work effectively with others. Links with Key Elements Personal Health Employability Links with Learning for Life and Work Employability Key Concept Career Management (Forensic Science career opportunities) Personal Development Key Concept Personal Health (Healthy bones) Home Economics Key Concept Healthy Eating (Eating for bone health)