Learning objectives / Learning outcomes / Specification link-up / Kerboodle
Students should learn:
·  the nature of fossils
·  how fossils provide evidence for the existence of prehistoric plants and animals. / Most students should be able to:
·  explain what a fossil is
·  describe some of the ways in which fossils are formed
·  suggest reasons why scientists cannot be certain about how life began on Earth.
Some students should also be able to:
·  evaluate what can be learnt from the fossil record. / Evidence for early forms of life comes from fossils. [B2.8.1 a)]
Fossils are the ‘remains’ of organisms from many years ago, which are found in rocks. Fossils may be formed in various ways:
·  from the hard parts of animals that do not decay easily
·  from parts of organisms that have not decayed because one or more of the conditions needed for decay are absent
·  when parts of the organism are replaced by other materials as they decay
·  as preserved traces of organisms, e.g. footprints, burrows and rootlet traces. [B2.8.1 b)]
Many early forms of life were soft-bodied, which means that they have left few traces behind. What traces there were have been mainly destroyed by geological activity. [B2.8.1 c)]
Suggest reasons why scientists cannot be certain about how life began on Earth. [B2.8] / Chapter map: Old and new species
Teachers notes: Old and new species
Support: History of the Earth timeline
Lesson structure / Support, Extend and Practical notes
Starters
Fossil five words – Get the students to explain their current understanding of what fossils are in five words. Read some examples out. Support students by placing some words to choose from on the board. Extend students by allowing them to create more five-word sentences – what they feel about fossils, what their importance is, etc. (5 minutes)
Fossil circus – Arrange a circus of numbered fossils or fossil pictures around the laboratory. Get students to look and make notes on what they might be. (10 minutes)
Main
Create a PowerPoint presentation or exposition on the ways that fossils form, such as cast formation, impressions and ice fossils. Victims of Pompeii illustrate cast formation; mammoths are found in ice; dinosaurs left footprints and animal droppings fossilise over time. For pictures, search the internet using key words and especially look for Ardley Quarry in Oxfordshire for its dinosaur footprints. Provide the students with a worksheet that they can complete as the presentation proceeds.
Give students a timeline exercise linking with the above. Using a long strip of paper (e.g. till roll), students should mark off the major evolutionary events for which there is evidence. An alternative to this is to use a clock face and discover that Homo sapiens evolved in the last few seconds before 12 midnight.
Give students an outline account of some of the methods of dating fossils: layers in rocks and sediments, potassium-argon dating, radiocarbon dating and looking at fossils of other species that overlap. With some more recent human fossils, the presence of artefacts (tools or shaped stones) can give clues as to the age of a fossil.
Try to get hold of some peat, look for plant remains and discuss their age (can be many thousands of years old).
Show students pictures of reconstructions of large fossil dinosaurs (such as are on show in the Natural History Museum) and ask: Were these fossils found as complete skeletons? Show some pictures of how reconstruction of fossils takes place using bits of the original skeleton. Discuss how accurate these reconstructions are. How are scientists sure that what they build up is a true representation? Refer students to reconstruction that has been done with prehistoric human skulls.
Plenaries
What makes a good fossil? – Lead a quick discussion on why some creatures became fossilised and others did not. Ask: ‘Why are there few fossils of worms and other softbodied creatures?’ (5 minutes)
Only half the story … – Display a sentence with many of the letters missing, but enough left to see what it is saying. Ask the students to write their own completed version. Support students by leaving out fewer letters or giving them a list of the missing letters that they can insert in appropriate places. Extend students by leaving out more letters and some words. Read out and discuss. (10 minutes) / Support
Get students to make a fossil using modelling clay or plaster of Paris for a mould and molten stearic acid to pour in and set (take care with hot liquids). Alternatively, students could use a modelling clay mould and pour plaster of Paris into the impression of a shell.
Extend
Set students the problem of finding out how long a representation of a timeline would need to be if the Earth is 4 600 000 000 years old and 100 years was represented by a millimetre. Ask: ‘How many A4 sheets of paper would be needed, allowing 1 cm overlap for gluing?’ [Do not try to make one – it is over 40 km!]
Course / Subject / Topic / Pages
Additional science / Biology / B2 6.1 The origins of life on Earth / Pages 70–71
Learning objectives / Learning outcomes / Specification link-up / Kerboodle
Students should learn:
·  how fossil evidence indicates the extent to which some organisms changed over time
·  that mass extinction of organisms occurred in the past. / Most students should be able to:
·  describe some examples of how much organisms have changed over time
·  suggest why some organisms may have become extinct, including massive natural disasters.
Some students should also be able to:
·  explain how living organisms can cause the extinction of species. / We can learn from fossils how much or how little different organisms have changed as life developed on Earth. [B2.8.1 d)]
Extinction may be caused by:
·  changes to the environment over geological time
·  new predators
·  new diseases
·  new, more successful, competitors
·  a single catastrophic event, e.g. massive volcanic eruptions or collisions with asteroids
·  the cyclical nature of speciation. [B2.8.1 e)] / Bump up your grade: Dead as a dodo
Lesson structure / Support, Extend and Practical notes
Starters
Can you run on your toenails? – Sensitively find out who has got the longest fingernails in the class. Ask: ‘Are they the strongest? Could you do press-ups resting on your middle finger?’ Relate this to how a horse walks, and introduce equine foot development using photographs of ancient hooves. This leads to a discussion of fossil evidence. (5 minutes)
Guinness advert evolution – Search the internet for a clip of the Guinness ‘Evolution’ advert from 2006 where three men are traced back in time through reverse evolution until they are mud skippers not enjoying drinking mud. Ask the students to make a list of the things that have some validity in the advert and to spot any flaws with it. Support students by giving them a list of the organisms and getting them to place them in order. Extend students by asking for their ideas on how the advert would look if they extended the time travel sequence further back into the past. (10 minutes)
Main
Following on from the ‘Can you run on your toenails?’ Starter activity, take the students through the evolution of the modern horse. Point out that this is not necessarily a direct line of evolution, that there could have been many other variations that died out and the evidence we have is probably incomplete.
Another good example of a sequence of changes can be illustrated by the fossil evidence for human evolution from Australopithecus to Homo sapiens. Research the Natural History Museum website and the work of Professor Chris Stringer for more information. Discuss the position of the Neanderthals – one of our relatives that died out. Why?
Two good examples of organisms that were thought to have been extinct and only known in the fossil record are the Wollemi pine (Wollemia nobilis) and the Coelacanth (Latimeria chalumnae), both of which have been found alive unexpectedly. Students can compare pictures of real Wollemia pine and Coelacanth specimens with pictures of fossils, commenting on any similarities and differences.
Plenaries
An overactive pituitary gland? – It has been suggested that the demise of the dinosaurs was caused by them developing overactive pituitary glands resulting in the excessive growth of bones and cartilage. Get the students to think of reasons why bigger bones could be a disadvantage. Support students by providing them with a list of suggestions from which they could discuss and choose appropriate reasons. Extend students by asking them to explain their reasoning. (5 minutes)
The extinction game – Five players have cards saying ‘Climate change’, ‘Meteorite’, ‘Predators’, ‘Disease’ and ‘Competition’ with appropriate pictures. Another player represents a species trying to survive. The ‘species’ throws a dice and one of the ‘extinction’ players also throws a dice. If the numbers match, the species is extinct and the players swap places and continue. If the numbers are different, the species has survived, the player collects the combined score on the dice and plays against the next ‘extinction’ player, until they eventually become extinct. Play to a time limit. (10 minutes) / Support
Give students a matching exercise where bits of evidence are placed in one column and the theories that they back up are in another – they have to join the evidence to the theory it supports.
Extend
Ask students to find out the different methods of dating fossils. They could summarise their findings in a poster which can be displayed in the laboratory.
Course / Subject / Topic / Pages
Additional science / Biology / B2 6.2 Exploring the fossil evidence / Pages 72–73
Learning objectives / Learning outcomes / Specification link-up / Kerboodle
Students should learn:
·  that environmental changes over geological time can cause extinction
·  that mass extinctions of the past may have been caused by single catastrophic events. / Most students should be able to:
·  explain what is meant by extinction
·  describe some environmental changes that may have caused extinction
·  suggest ways in which the extinction of the dinosaurs occurred.
Some students should also be able to:
·  evaluate the theories for the extinction of the dinosaurs. / Extinction may be caused by:
·  changes to the environment over geological time
·  new predators
·  new diseases
·  new, more successful competitors. [B2.8.1 e)] / Extension: A Madagascan mystery
Lesson structure / Support, Extend and Practical notes
Starters
Dead as a dodo – Search the internet for a picture of a dodo. Ask students to make a list, in rough, of as many types of extinct animal as they can in three minutes. Check who has the largest number and get the student to read the list. Ask others in the class to check and add. This leads into a discussion of what extinction means. (5 minutes)
What causes extinction? – Get the students to discuss in pairs or small groups the reasons why some species become extinct. Support students by giving prompts to help them identify ways in which animals may become extinct. Extend students by getting them to speculate on future causes of extinction and how they might be discussing this topic in 500 000 years time. (10 minutes)
Main
Visit, for example, www.thedayaftertomorrowmovie.com to find information about global climatic changes. Highlight changes in temperature such as ice ages. Link, if possible, with the geological time scale discussed in B6.1 The origins of life on Earth and the evolution of different groups of organisms. Discuss the impact of these changes on the creatures around at the time. This can link up with the ideas of competition, survival of the fittest and natural selection.
Much has been made of global warming altering our climate and the times at which plants flower, changing patterns of migration and growing different crops in different parts of the world. Ask: ‘If our climate became warmer or colder, what animals and plants would be affected in Britain?’
Show a video clip from the film Deep Impact of a simulated comet strike on Earth (search the web for ‘Deep Impact trailer’). Make a model, using a light sensor attached to a data logger and a glass or plastic container containing some fine dust. Shine a light through and measure intensity before and after shaking up. Discuss the effects of the lack of light on life on Earth.
Get the students to carry out an empathy exercise, imagining what it would have been like for the creatures living at the time of a comet strike or a global winter (if these theories are correct). Get them to write some creative prose or poetry to get across what it must have felt like being plunged into semi-darkness for months or years.
Plenaries
Greatest impact – Write up the words ‘Climate change’, ‘Meteorite’, ‘Predators’, ‘Disease’ and ‘Competition’, or use the cards from ‘The extinction game’. Ask students to rank the words in order of importance. Choose some to explain their choices. (5 minutes)
Mass extinction storyboard – Establish the different theories of why there were mass extinctions at the end of the age of the dinosaurs. Get the students, in pairs or small groups, to come up with an illustrated storyboard to guide production of a film, telling students their age about the different theories. Support students by showing them an example. Extend students by getting them to add a theory of their own. These students should provide more imaginative and complex responses than supported students. (10 minutes) / Support