NEW SPEC UNIT 2 (TOPIC 4)

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Salters-Nuffield Advanced Biology Resources

Activity 4.1 Student Sheet

THE GALAPAGOS ISLANDS

Purpose

 To introduce some of the biological ideas covered in the topic.

Darwin and the Galapagos Islands – then and now

Darwin spent five years travelling around the world on the Beagle. The wealth of animals and plants he encountered, and the adaptations they exhibited were the stimulus for the theory he developed over the next 20 years and published in his book On theOrigin of Species. The Galapagos Islands are estimated to have between 5500 and 6000 identified species and most importantly a particularly high level of endemism (species found here and nowhere else).

Look at the interactive map and factfile in the tutorial that accompanies this activity to learn more about the Galapagos Islands and discover some of the species to be found on the islands. Listen to the interview with Sarah Darwin, botanist and great-great-granddaughter of Charles Darwin. Visit the weblinks that accompany this activity, then answer the questions that follow.

Questions

Q1 The Galapagos Islands lie 1000 km off the west coast of Ecuador. The islands are bathed in cool polar ocean currents, and receive rain from the south east winds. What would the climate be like in the Galapagos Islands and why?

Q2 The Galapagos Islands are volcanic, having erupted from the seabed around 3 km below the sea surface. How would the origin of the islands affect the animal and plant life that has become established here?

Q3 Galapagos Island tortoises can grow to over 1.5 m in length and weigh over 250 kg. What advantages could there be to this large size?

Q4 Iguanas are cold-blooded and need to regulate their body temperature by moving in and out of the sun. Suggest why species such as this are more common in the tropics than in temperate climates.

Q5 What adaptations do large cacti such as Opuntia species seem to have for life on the islands?

Q6 Do you think there is any adaptive reason why the blue feet in the blue-footed booby could have evolved?

Q7 The marine iguana is the only truly marine lizard, spending much of its time in the water. What physical adaptations would this species require that would differ from its land-living relative?

Q8 Although they spend most of their lives at sea, female turtles return to lay eggs on the beach on which they were born, often travelling thousands of miles in the process. Why do you think this behaviour has evolved instead of the turtles stopping at the first beach they come to?

Q9 What could be the purpose of the large throat pouch in the magnificent male frigate bird (Fregata magnificens)?

Q10 Galapagos finches are unique to the Galapagos Islands and yet birds such as the frigate bird and the green turtle are found throughout the Pacific. Why could this be?

Q11 Four species of Galapagos finches were sketched by Darwin during his voyage. What clues do you have that these are distinct species and why might these differences have evolved within the same group of islands?

Q12 Most of the native terrestrial animals on the Galapagos Islands are threatened or extinct; for example, four of the original eight species of endemic rice rat have disappeared. What might have caused these extinctions and may continue to threaten many of the animal and plant species on the islands?

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Salters-Nuffield Advanced Biology Resources

Activity 4.1 Teacher Sheet

THE GALAPAGOS ISLANDS

Purpose

 To introduce some of the biological ideas covered in the topic.

Darwin and the Galapagos Islands – then and now

The activity is meant to encourage students to start thinking about some of the ideas that will be covered in the topic, in particular adaptation, the concept of the species, evolution and endemism. Alternatively it could be used later when considering adaptations or at the end of the topic for revision purposes.

The interactive tutorial that accompanies this activity provides a series of photos as stimuli to thinking; in most cases the text in the activity does not provide the answers. The Student Sheet is intended for use with the interactive activity. It could be completed individually or as whole class, using the questions on the sheet for a class discussion. The final two questions are not linked to photographs within the activity.

Answers

Q1 The climate is warm because the islands are on the equator, but the temperature is moderated by the polar currents. Rainfall will be greater on islands on the windward, south east side of the archipelago.

Q2 Because the islands arose from the sea bed as volcanoes, at first they had no land animals or plants. All the animals and plants had to travel the long distance to the remote islands and so only a few species have been able to colonise the islands. They then evolved into new species that are found nowhere else.

Q3 Scientists still do not know for sure why some species are so large on islands. Indeed big species, such as elephants, tended to become much smaller on islands – possibly because there was not as much food for them. On the Galapagos Islands larger tortoises might do better in competition for mates or food.

Another possibility is that larger animals might be better at surviving droughts or other extremes of weather (think about surface area to volume ratios).

Q4 In a warm climate it is easier for reptiles to get enough energy from the sun to maintain their body temperature so they survive in these conditions.

Q5 They store water in their succulent stems to help them to survive drought periods. They have spines to protect them from grazing animals. They do not have leaves, to reduce water loss.

Q6 To attract a mate.

Q7 Adaptations for swimming may include limb action and streamlining. You would also expect feeding and camouflage differences from the land iguana. They need to be able to excrete salt from the sea water they drink. (They have a gland which extracts salt and enables them to sneeze it out through their noses.)

Q8 If they were born on a particular beach, and survived, it is likely that the conditions on that beach were favourable for turtle survival. A strange beach may have all sorts of

disadvantageous factors, such as predators, unfavourable tides, lack of food, etc.

Q9 Attracting a female; displaying to other males (indicating fitness).

Q10 The frigate bird and green turtle move over large distances so there hasn’t been the

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Salters-Nuffield Advanced Biology Resources

Activity 4.1 Teacher Sheet

Q11 The most obvious differences are those in beak shapes due to feeding differences. The finches evolved to eat different food in order to fully exploit the available niches in the islands and avoid competition with other finch species.

Q12 Introduced species caused the rice rat extinctions. Introduced goats, rats, pigs, dogs and cats are a particular problem. The introduced species (including humans) cause habitat destruction and some prey directly on the native species. Disturbance by the growing human population and tourists threatens wildlife, as does pollution.

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Activity 4.2 Student Sheet

WHAT IS IT?

Purpose

 To introduce some of the biological ideas covered later in the topic.

 To develop observation and interpretation skills.

 To highlight the need for detailed information about a species if it is to be conserved.

Identifying organisms

Biologists in the field have to use their observation and interpretation skills to make deductions about the organisms they discover. This lets them build up an accurate picture of the organisms’ lives, how they interact with their surroundings and what threats they may face now or in the future. This observation and interpretation is as important to biologists today as it was for Darwin. In this exercise your task is to make some deductions about the animal in the field sketch provided.

Questions

Study the field sketch and try to answer the following questions, giving a reason for each of your answers. Do not worry if you get the answers wrong, but try to make an intelligent attempt.

Q1 a What animals do you think it is most closely related to?

b Can you suggest anything about what it eats, or how it gets its food?

c What sort of habitat do you think it occupies?

d Is it likely to be active at night or during the day?

Q2 You have less information than most taxonomists would have about a new organism. Normally they would have an actual specimen (usually dead). If they are lucky they have a chance to observe it alive as well. What information could you get from a dead specimen that you could not get from a live one and vice versa?

Q3 Would a (living) captive specimen give you more or less information than a free-living one? Explain your answer.

Q4 If biologists do not recognise this animal they would use a key to help them identify it. A key lets you name the animal, which is vital if you are going to find out more information about it. It is an aye-aye; this is its common name, its scientific name is Daubentonia

madagascariensis. Aye-ayes are found on only one island; suggest where this might be (the Latin name provides a big clue, if you cannot spot where, use the weblinks that accompany this activity to find their location).

Q5 The first part of the scientific name is shared by the aye-aye’s closest relatives. Do some research and find out how many other species share the name Daubentonia.

Q6 If you look the aye-aye up on the International Union for Conservation of Nature (IUCN) Red List you will find that it is classified as near threatened. Find out what being classed as near threatened really means by visiting the IUCN Red List of Threatened Species website.

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Activity 4.2 Student Sheet

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Salters-Nuffield Advanced Biology Resources

Activity 4.2 Teacher Sheet

WHAT IS IT?

Purpose

 To introduce some of the biological ideas covered later in the topic.

 To develop observation and interpretation skills.

 To highlight the need for detailed information about a species if it is to be conserved.

Identifying organisms

This activity should get students thinking and provide a short introduction to some areas that will be covered later in the topic, for example, adaptation, classification and the role of zoos in conservation. Working in small groups or pairs, students are presented with the sketch of the unknown animal from Madagascar. If they have looked at the introduction to the topic they will have already seen a photo of the animal. Projecting a colour image for the class to see would be useful. They should not be told anything about the animal at the start of the activity.

Students should pool their combined knowledge acquired from previous courses, general knowledge and common sense in order to generate a description of the creature’s lifestyle, adaptations and possible relatedness to other species. Some students will recognise the aye-aye, but others will be unfamiliar with the species. This does not matter; in either case they can still complete the questions. Do not expect them to get everything right in Question 1. Even professional taxonomists classified aye-ayes as rodents in the 19th century – presumably because of their teeth.

The first three questions are not meant to take up a great deal of time; students could have approximately 5–10 minutes to complete the task and then the ideas could either be pooled by the teacher/lecturer, or students could present their results to the class in groups. The ideas presented could be discussed and possible ways of determining the validity of various suggestions could be explored. The point is that we need to know more about the species if we are to build an accurate picture of its life, which is vital for its conservation. The later questions require students to do some research using the Internet or use the information sheet which accompanies these notes. These could be finished outside class time.

Answers

Q1 a The shape of the hands and feet suggests a kinship to primates; the shape of the muzzle suggests lemurs.

b The prominent, continually growing incisors should suggest tough foods (actually used for stripping bark to get to insects). The very long middle finger is used for snagging grubs in crevices in wood, but this takes a leap of imagination or prior knowledge to come up with. (It also eats nuts and nectar and raids crops.)

c The long toes suggest grasping – and therefore climbing in trees. It is found in rainforest, drier forest and scrub.

d It is nocturnal. This is suggested by the large eyes and the fact that they reflect light well (like cats’ eyes).

Q2 Dead specimens can give you precise information about their diet from stomach contents. A living specimen will give you information about how the animal moves and some aspects of its behaviour.

Q3 A live, captive individual can give you some information about the species, but will not tell you much about social interactions, range size or how it behaves in its natural habitat. A free-living individual can give you a clearer picture of these things, but is much harder to observe.

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Activity 4.2 Teacher Sheet

Q5 Only the aye-aye is found in the genus Daubentonia. There was a giant aye-aye, Daubentonia robusta, but this is now extinct, probably as a result of human activity.

Q6 A species is near-threatened if it is considered to be close to facing a very high risk of extinction in the wild.

Q7 Captive breeding programmes; protection of habitats.

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Activity 4.2 Teacher Sheet

Aye-aye information sheet

Scientific name – Daubentonia madagascariensis

Background

This weird and wonderful lemur is without doubt the world’s most unusual primate. Long persecuted in its native Madagascar as an omen of death and evil, the aye-aye, like most of its lemur relatives, faces imminent extinction because of the added pressure of deforestation. This elusive species is the largest nocturnal primate and is the island’s answer to the woodpecker. Its specially adapted,

elongated, flexible and skeletal third finger is used to find nutritious grubs and winkle them out from their woody burrows.

Six aye-ayes arrived at Jersey Zoo in 1990 from Madagascar – the result of Gerald Durrell’s final animal collecting expedition. In 1992, less than two years later, the first ever captive-bred aye-aye infant emerged; no mean feat, as this primate has proved extremely tricky to keep successfully in captivity. Since then, the five surviving youngsters of the seven born here, and around a dozen born at three other institutions, have added to the ‘safety net’ population for this endangered species. Two of the Jersey-bred animals have gone to other zoos involved in the breeding programme to further increase the population and keep it genetically healthy.

The Trust has well-established links with the Madagascan people and government, especially involving the conservation of lemurs, and is part of the Madagascar Fauna Group. Since 1964, a great deal of expertise has been gained at the zoo and in the wild with various species. As well as captive breeding, vitally important habitat protection, research, education and training programmes are ongoing. A number of Madagascan students have completed the course at our International Training Centre and returned home with the skills they need to carry out such work and help save their native wildlife.

Species classification

Lemurs are primates found only on the island of Madagascar, which has been separated from East Africa for over 100 million years. Without competition from other primates, the lemurs evolved into many different kinds, from the size of a mouse to that of a giant panda. Humans arrived on the island just 1500 years ago. Since then about a third of the different lemurs that existed (mostly large, relatively slow-moving ones) have become extinct and about 80% of those remaining are threatened with the same fate. The aye-aye is very different from any other species of lemur and is the only member of the family Daubentoniidae. A second member of this family was the giant aye-aye,

Daubentonia robusta, which no longer exists and was probably driven to extinction by humans. In Malagasy, aye-aye can mean something that someone does not want to talk about. So, because of local superstition, this lemur is thought to have got its name because people do not like talking about it.

Description

This unique primate is strictly nocturnal and its huge, staring orange eyes are well adapted for night vision. The aye-aye’s fur is mainly dark brown to black, with long, white-tipped hairs scattered throughout. It has a long, bushy tail and sparse fur on the face, making it pinkish. Its massive naked ears are highly mobile and give the aye-aye incredibly sensitive hearing. Once mistakenly classified as a rodent, the aye-aye’s front teeth never stop growing and are incredibly efficient at gnawing, just like a rodent’s. They can even bite their way through concrete and aluminium. Aye-ayes also have claws, rather than nails like all other lemurs. Another special characteristic of the aye-aye is the position of its nipples; they are near the genitals, rather than in the armpit and chest area like those of other primates. However, the most specialist feature of all is the third digit of their hands, which is thinner, longer and more flexible than the others (the increased flexibility is enabled by ball-and socket joints, like those of shoulders and hips).

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Activity 4.2 Teacher Sheet

Distribution and habitat

The aye-aye is one of the most widely distributed Madagascan primates, where forests still remain. It only appears to be completely absent from the south-western part of the island, where fossils of its close relative, the giant aye-aye, have been found. Aye-ayes live in primary and secondary rainforest, deciduous forest and dry scrub forest, as well as areas of cultivated trees, particularly coconut and lychee. Nocturnal in its habits, the aye-aye sleeps during the day in a nest built in the top of large trees out of twigs and dead leaves.

Feeding habits

Up to 80% of the night is spent foraging and travelling high in the trees, and distances of 2–4 km may be covered in a single night. Like diurnal mammals, nocturnal ones sometimes rest during their active period, and an aye-aye’s foraging sessions are punctuated by inactive periods of up to two hours. The aye-aye’s diet is quite specialised and seasonally variable – it depends on what is available at a certain time of year. Its most important native foods are the ramy nut, the hard shell of which the aye-aye is able to crack open with its chisel-like front teeth, nectar from the traveller’s tree, some fungi and insect grubs. Cultivated crops are also raided opportunistically, including sugar cane, lychees, mangoes and coconut, which brings the aye-aye and local people into conflict.

The aye-aye spends much of its foraging time hunting for nutritious and energy-rich insect larvae. It does this by locating cavities under bark and inside branches and rotting wood by tapping with its long, middle finger. Once it hears the movement of its prey within, the aye-aye gnaws an access hole and uses its special finger again to winkle out the juicy grub. In the zoo this mode of feeding is

encouraged by ‘behavioural or environmental enrichment’, which is a technique used to enable captive animals to behave as naturally as possible. Lengths of bamboo stems and holes drilled in logs are filled with different kinds of insect larvae, so that the aye-ayes have to work to find their favourite food – given the chance they would polish off a bowl of mealworms in no time at all. Despite its preference for invertebrate finger-food, the aye-aye has diverse tastes, but captive animals are fussy eaters; individuals have certain preferences and dietary variety is much appreciated. The aye-aye’s diet in the zoo has been carefully studied to make sure that what they choose to eat contains all the

necessary nutrients. They are fed three times a day and in addition to a special insect feed they get a selection of various fruits and vegetables and other items, such as nuts, eggs, sugar cane and nectar.

Breeding and social behaviour

Aye-ayes are largely solitary and male aye-ayes move through large home ranges, between 100 and 200 ha (40–80 acres), which often overlap to a substantial degree. When males meet their interactions are frequently aggressive, as they are in competition for resources and females. Females have much smaller home ranges of 30–50 ha (12–20 acres), which do not overlap with one another, so they very rarely interact, but are very aggressive when they do. Males and females occasionally come together and interact for brief periods, usually while foraging. Regular scent marking with their cheeks, neck and genitals is a way that aye-ayes let others know of their presence and repel intruders from their territory.

Aye-ayes do not have a fixed breeding season, but at the onset of their three-day receptive period, females move quickly around their home range, advertising their condition to nearby males with distinctive calls. These calls attract the attention of several males, who gather around a female and fight each other for a chance to mate with her. Mating lasts for about an hour and takes place in an upside-down position underneath a branch; and rivals try to dislodge the male who won the scramble. Afterwards the female moves to another location and repeats her call, which means that both males and females may get to mate with several partners. Females build a particularly dense nest to give birth in. A single baby, which weighs about 100 g, is usually produced after a pregnancy of 23–24 weeks, and stays in the nest for about 8 weeks. Aye-aye infants develop slowly compared with other lemurs and have a long period of dependence on their mother, perhaps over a year in the wild.

Females are thought to have a 2–3 year interval between births and sexual maturity is reached at about 3½ years.

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Activity 4.2 Teacher Sheet

Conservation status

The World Conservation Union (IUCN) currently classifies the aye-aye as near-threatened on the Red List of Threatened Species, which means that it is close to facing a very high risk of extinction in the near future. Since 1975 it has also been listed under Appendix I of CITES (the Convention on International Trade in Endangered Species of Wild Fauna and Flora). This affords the species the highest degree of protection against any international trade.

The current size of the aye-aye population is unknown, but decreasing. The species only occurs at low densities and appears to be rare throughout its range. Aye-ayes are found in 16 of Madagascar’s protected areas. It has so far proved impossible to estimate the number of aye-ayes remaining in Madagascar. Further fieldwork is needed to assess the status and distribution of this enigmatic species of lemur. The main threat to the aye-aye’s survival is habitat loss – large tracts of forest are needed to sustain viable populations, because of the relatively low density of animals. The treatment of aye-ayes by humans does vary between areas, depending on religious beliefs and folklore. Although they are often killed on sight as harbingers of evil, some people regard them as ancestral spirits that bring good luck and leave them alone.

In the Zoo

In 1990 the Durrell Wildlife Conservation Trust initiated a breeding programme in collaboration with the Government of Madagascar to safeguard the future of the aye-aye. Six potential founders for the captive population were collected from the wild in what turned out to be Gerald Durrell’s final expedition. This aye-aye survival plan, coordinated in Jersey, is now a collaborative international effort involving four other zoos in Europe, Madagascar and the USA. The Trust also publishes an ‘International Studbook’ – a

regularly updated document that coordinates the

breeding and transfer of the 40 or so aye-ayes in captivity, to ensure that the population is as productive and genetically healthy as possible. There are six aye-ayes currently kept at the zoo: two adult males, two adult females and two sub-adult males, which are still housed with their mothers. The adult aye-ayes are kept separately, except for mating when females are receptive. They have spacious indoor enclosures that contain extensive networks of ropes and branches for climbing and a nest box for sleeping and rearing infants. The aye-ayes in two of the five enclosures share their home with Madagascan giant jumping rats. The two species are relaxed about each other’s presence and this adds extra stimulation to their lives, as well as making an interesting mixed exhibit.

The future

Continued research in captivity and the expansion of the aye-aye breeding programme is important to maintain and strengthen the safety net population. In addition, the implementation of further

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Activity 4.3 Student Sheet

ECOLOGICAL NICHE OF A LEAF-CUTTER BEE

Purpose

 To consider the ecological niche of a leaf-cutter bee.

Working out the niche

In this activity you will be a nature detective and work out one way the leaf-cutter bee is exploiting its environment – an aspect of this type of bee’s ecological niche.

Figure 1 shows a leaf-cutter bee holding a piece of leaf which it has cut from a rose bush. Figure 2 shows rose leaves after a visit by leaf-cutter bees. These bees eat nectar and pollen, so they are not using the leaves for food. Colour versions of these images are present in the online mediabank.

Figure 1 Leaf-cutter bee and piece of leaf cut from a rose bush.

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Activity 4.3 Student Sheet

Questions

Q1 Look at the shape of the leaf pieces cut from the rose bush. There are two main kinds of shape. Draw a diagram of the two shapes. Work out the approximate ratio of one shape to the other.

Q2 Suggest what sort of structure the bee could make from these leaf pieces.

Q3 Suggest how the bee might use the structures created.

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Activity 4.3 Teacher Sheet

ECOLOGICAL NICHE OF A LEAF-CUTTER BEE

Purpose

 To consider the ecological niche of a leaf-cutter bee.

Working out the niche

In this activity the leaf cutter bee is used to illustrate the idea of ecological niche. Students interpret photos of the cut leaves.

Students think through how the leaf-cutter bee is exploiting its environment; they are considering one aspect of the bee’s ecological niche.

Answers

Q1 There are round pieces and oval pieces (like the one the bee is holding). The round pieces come in smaller and larger types. The oval pieces are wider at one end. The ratio (in the photograph) is approximately 8 round pieces to 24 oval pieces.

Q2 The bee makes a tube (thimble) shape from the leaf pieces. There is a round piece at each end; the oval pieces overlap to form the length of the tube. The bee places the tube in a hollow in the ground, or in something like an old flower-pot.

Q3 The bee lays one egg in each tube, then stocks it with pollen as food for the developing larva.

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Activity 4.4 Student Sheet

WELL-BEHAVED BEETLES

Purpose

 To investigate behaviour of seed beetles as an example of behavioural adaptation.

SAFETY

Wash your hands thoroughly after handling the beetles or their environment.

Callosobruchus maculatus

, the seed beetle

The natural habitat of seed beetles is a field crop of beans (azuki, mung or black-eyed beans) in a tropical or sub-tropical country. When adult seed beetles (Figure 1) emerge from the bean in which they have developed, they live for 2–4 weeks. Amazingly, they neither eat nor drink during their adult lifetime. This is just one fascinating aspect of their behaviour, which can be witnessed in the

classroom.

Figure 1 Male (left) and female (right) adult seed beetles.

A beetle begins life as an egg, laid on a bean. The egg hatches 4–6 days later and the larva eats its way into the bean until it is about 18 days old, when it pupates. About 7 days later, the adult emerges and searches for a mate.

Seed beetles engage in multiple mating. In fact, males appear to do nothing other than mate, recover and look for more mates. Like males, females are also eager to mate, after which they identify good egg-laying sites on beans. This is to ensure that their offspring survive, mate and make a genetic contribution to future generations. Females subsequently mate again and lay more eggs, repeating this pattern of behaviour until they die.

Investigating the behaviour of seed beetles

Seed beetles are remarkably easy to keep, so are perfect for behaviour studies. Most of us know that woodlice seek out dark places during daylight – but what about seed beetles? Are seed beetles positively or negatively phototactic (move towards or away from high light intensity)? Do beetles move as fast on vertical surfaces as they do on horizontal surfaces? Can females recognise a good egg-laying site: what happens if the seed coat of a bean is removed – do females still lay eggs on it? Select one of the questions posed above. Design an experiment to answer the question. Using the Developing Practical Skills Framework to help you plan your investigation, make sure you:

 identify the variables to be measured and controlled

 describe the experimental apparatus and method in detail

 identify any safety and ethical issues, and describe how you will reduce any risks

 identify any sources of error.

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Activity 4.4 Teacher Sheet

WELL-BEHAVED BEETLES

Purpose

 To investigate behaviour of seed beetles as an example of behaviour adaptation.

SAFETY

Ensure students wash their hands thoroughly after handling the beetles or their environment.

Callosobruchus maculatus

, the seed beetle

In this activity seed beetles are used to investigate behavioural adaptation, although alternative organisms can be used. The Association for the Study of Animal Behaviour (ASAB) website has protocols for practical work using maggots and woodlice. The website can be found in the weblinks that accompany this activity.

The Student Sheet provides some general information about seed beetles and poses questions about seed beetle behaviour. Students are asked to select one of the questions and design an experiment to answer it. The Student Sheet does not provide a detailed procedure so students can plan the

experiment themselves using the Developing Practical Skills Framework to help. Students complete the experiment and then explain the advantage in the field of the behavioural adaptations the beetles’ exhibit.

Additional information about seed beetles is provided in this sheet, along with information about how the experiments could be completed. We are grateful for the help of ASAB Education Officer, Michael Dockery, in the production of this activity.

Keeping seed beetles

Seed beetles are remarkably easy to keep in schools and colleges. They can be housed in disused coffee/jam jars with some muslin (or plastic netting) over the top, held in place by an elastic band. They require only a few minutes of maintenance once every 5–6 weeks.

Establish new cultures of beetles in clean jars with fresh beans. This minimises the build up of bean/beetle debris to which some people may be allergic. A barrier of Fluon® around the top 5 cm of

the jar makes the beetles lose their footing, so they cannot reach the top and get under any folds in the muslin. Fluon® is available from Blades Biological.

Investigating the behaviour of seed beetles

Are seed beetles positively or negatively phototactic?

This can be investigated by placing one beetle at a time in the small central circle of Figure 1 and recording where they cross the perimeter of the larger circle. The sectors can be numbered or labelled according to the points of the compass. Students record which of the eight sectors the beetle crossed on leaving the outer circle. The beetles are positively phototactic. If the room has windows down only one side or a light source is set up on one side, this will be clearly demonstrated by their movement preferences.

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Activity 4.4 Teacher Sheet

Figure 1 Wheel diagram used to investigate whether seed beetles are positively or negatively phototactic.

Do beetles move as fast on vertical surfaces as they do on horizontal surfaces?

Speed of movement can be determined by timing how long it takes a seed beetle to travel over a certain distance when placed in a thermometer tube (or tube of similar dimensions). Compare their speeds of movement in the tube placed horizontally and vertically. Beetles move more quickly vertically than horizontally.

Can females recognise a good egg-laying site? What happens if the seed coat of a bean is removed – do females still lay eggs on it?

Put a mated female beetle in a Petri dish with 10 clean azuki beans and 10 azuki beans with the testa removed. Record the number of eggs laid on the two types of beans. Seed beetles attach their eggs to the seed coat. The larvae hatch within about five days and chew through the seed coat into the seed where they complete their development.

Notes on

Callosobruchus maculatus

, the seed beetle

Dr Michael Dockery.

Association for the Study of Animal Behaviour Education Officer.

The seed beetle is a pest of stored legumes, i.e. peas, beans, etc. The legumes that have been most extensively used in research are mung beans (Vigna radiata), black-eyed beans (V. unguiculata) and azuki beans (V. angularis).

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Activity 4.4 Teacher Sheet

Variation is largely due to pests and diseases. Beetle damage makes black-eyed beans unfit for human consumption and planting. The beetles colonise seed both in the field and in grain silo storage. Initial infestation is in the field, then transferred into stores. The seed beetle life cycle is 20–30 days

(depending on the temperature), so there are approximately 12 life cycles per year and potential for damage is great.

In 1974 the International Institute of Tropical Agriculture started a programme to identify strains that had some resistance to beetle attack. These strains are not immune to attack, but damage is less. The beetle is also a serious pest of cowpeas. It reduces growth and quality of the seed, and also affects its germination.

The females stick eggs singly to the surface of the host bean. The eggs hatch 4–5 days later (at 28–30 °C). The first instar larva burrows into the bean directly below the egg and begins to feed. The beetles have a generation time of 4–5 weeks. One study gives the following developmental data:

oviposition egg

6 days after the start of oviposition first instar 9 days after the start of oviposition second instar 12 days after the start of oviposition third instar 16 days after the start of oviposition fourth instar 18 days after the start of oviposition pupa

25 days (approx) after the start of oviposition the adult beetle emerges 10–12 days after emergence death of the adult

The larva passes through four instar stages within the bean. During the fourth instar, the cell containing the larva is enlarged so that it is next to the outer skin of the bean (testa). The larva may then be seen through a translucent window. The adult chews a hole through the testa and emerges through this. Occasionally the cell is not adjacent to the testa, so the adult dies because it cannot emerge.

The emerging adult beetles are extremely well-adapted to the bean storage conditions, since they require neither food nor water to reproduce. However, if they are offered water or a sucrose solution this can lengthen their life-span.

The adults will start to copulate very soon after emergence. The females will usually begin egg-laying on the day of emergence. Virgin females, if given access to beans, lay infertile eggs. Females lay fewer eggs if too few beans are offered. Fecundity also drops if there is adult crowding.

Before laying eggs, females ‘inspect’ a bean. They prefer to lay on an egg-free seed. They have been shown to be able to distinguish seeds bearing different numbers of eggs. This does not imply that they can count. Females can detect that eggs have already been laid on the surface of the bean, probably by detecting a marker pheromone left by a previous female.

There are several geographic strains of seed beetle (Callosobruchus maculatus). These strains show differences in their rates of natural increase, oviposition behaviour and dispersal tendencies. A key difference in the strains is their response to competition. An Indian strain produces larvae in which competition for food in the seed is strong. The larvae fight in the bean and only one adult emerges. Each larva can sense the presence of others by the vibrations they emit. The females of the Indian strain distribute their eggs on the surfaces of beans in a uniform manner – that is, they are fairly evenly distributed.

A Brazilian strain produces larvae in which competition is weak and more than one adult can emerge from each bean. If two larval burrows intersect, the larvae gather grass and build up a wall between the two burrows. The females of this strain lay their eggs in a random-uniform manner.

Adults can occur in two forms:

 a ‘normal’ form which doesn’t fly, has a high fecundity and a short life

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Salters-Nuffield Advanced Biology Resources

Activity 4.4 Technician Sheet

WELL-BEHAVED BEETLES

Purpose

 To investigate behaviour of seed beetles as an example of behavioural adaptation.

SAFETY

Wash your hands thoroughly after handling the beetles or their environment.

Callosobruchus maculatus

, the seed beetle

Requirements will depend on the behaviours investigated by students, but all require seed beetles. These are remarkably easy to keep in schools and colleges.

Seed beetles can be housed in disused coffee/jam jars with some muslin (or plastic netting) over the top, held in place by an elastic band. They require only a few minutes maintenance once every 5–6 weeks. Seed beetles are designated pests for food crops (Defra 2015, see weblinks). Therefore, they should not be released into the environment. Dispose of seed beetles by placing jars into a freezer before disposing of the whole jar as normal waste.

Establish new cultures of beetles in clean jars with fresh beans. This minimises the build up of bean/beetle debris to which some people may be allergic. A barrier of Fluon® around the top 5 cm of the jar makes the beetles lose their footing, so they cannot reach the top and get under any folds in the muslin. Fluon® is available from Blades Biological.

The Education Officer at ASAB may provide teachers with egg-laden beans in order to establish their own seed beetle cultures, or they can be obtained from Blades Biological.

Education Officer

Association for the Study of Animal Behaviour Department of Biological Sciences

Loxford Tower

Manchester Metropolitan University Higher Chatham Street

Manchester M15 6HA

Or contact via the ASAB website, which can be found in the weblinks that accompany this activity.

Are seed beetles positively or negatively phototactic?

Requirements per student or

group of students Notes

Seed beetles

Wheel diagram The wheel diagram is shown in Figure 1

Lab With windows or a light source at one side.

Do beetles move as fast on vertical surfaces as they do on horizontal surfaces?

Requirements per student or

group of students Notes

Seed beetles

Thermometer tube Or any similar transparent tube

Ruler

Marker pen To mark a set distance on the side of the tube seed beetles are

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Salters-Nuffield Advanced Biology Resources

Activity 4.4 Technician Sheet

Can females recognise a good egg-laying site? What happens if the seed coat of a bean is removed – do females still lay eggs on it?

Requirements per student or

group of students Notes

Seed beetles Petri dish

20 azuki beans 10 with the seed coat removed

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Salters-Nuffield Advanced Biology Resources

Activity 4.5 Student Sheet

ADAPTATIONS

Purpose

 To explain how an organism’s adaptations help it to survive.

 To communicate knowledge and ideas about adaptation.

 To develop presentation skills.

SAFETY

Wash your hands thoroughly after handling animal or plant materials.

An exhibition on adaptation

In this activity you will work in collaboration with other students to produce an exhibit about a named organism.

Your exhibit will form part of a whole-class exhibition featuring a range of different organisms. The aim of the exhibition is to communicate the concept of adaptation. Some examples of adaptations are described on pages 3–7 of this Student Sheet with questions for you to answer. Colour versions of the images are available in the online mediabank.

Before the exhibition

Discuss as a class:

 What might be the features of a successful exhibit?

 How many students will prepare each exhibit?

 How and where you will most effectively set up the whole exhibition?

 Who will you invite to see it?

 How will each student most effectively learn from others’ exhibits?

 Are there any health and safety implications in setting up the exhibition?

Planning your exhibit

Use the questions below to plan your group’s exhibit and allocate tasks for your group.

What are the aims of your exhibit?

These may, for example, be to communicate information using a variety of media, to communicate specific points about the subject content, communicate to a specific audience, etc.

What are the main adaptations to be featured?

Think about the organism’s environment and how the adaptation helps them to survive.

What objects or media will best illustrate the main points you are trying to

communicate?

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Salters-Nuffield Advanced Biology Resources

Activity 4.5 Student Sheet

What type of space is available for your exhibit?

Draw a plan of your exhibit to fit the space you have been allocated, showing what you will include. Annotate the plan with details of each aspect, for example, any objects, photos, labels or text to be used. A planning form like the one shown in Table 1 would help you organise these details.

Add to your planning form details of who is responsible for each part of the exhibit. One additional task for your group is to make an evaluation form for other students to evaluate your exhibit. The evaluation should refer to your aims.

Planning form

Title of exhibit:

Aims of the exhibition:

Date, time and venue:

Name of item Description of item Who is

responsible? Deadline for work to be completed

Evaluation form A form which collects feedback on whether or not the exhibit has successfully fulfilled its aims

Table 1 Example of an exhibition planning form.

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Salters-Nuffield Advanced Biology Resources

Activity 4.5 Student Sheet

Barn owls

Hearing

Barn owls catch their prey – mostly voles and mice – in complete darkness, using hearing alone. Birds have no external ears like a mammal – just simple openings. The ear openings of the barn owl are hidden in the disc of feathers around the face (Figure 1). The left ear hole is slightly higher and at a different angle from the right one. When it hears potential prey, the barn owl tilts its head and moves the ruff of feathers surrounding the facial disc.

Q1 Suggest why the barn owl has a disc of feathers around its face.

Q2 Explain why the owl moves its head when it hears prey.

Q3 Give a reason why an owl has different positioning of its ear holes.

Q4 What selective advantage is there for the owl:

 in having different positioning of its ear holes

 in moving its head when it hears prey?

Figure 1 Young barn owl.

Feathers

The flight of an owl is very quiet. It achieves this by having very soft feathers. In addition, the leading edge of the first primary feather on each wing is serrated (Figure 2). This helps to reduce the

turbulence caused by the wing as it cuts through the air. (Think of the noise made by a swan’s wings for comparison).

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Salters-Nuffield Advanced Biology Resources

Activity 4.5 Student Sheet

Q5 Give two advantages of an owl’s silent flight.

Look at Figure 3, or try pulling the vanes of a bird’s flight feather apart. What do you notice? Pull it firmly until the barbs separate. Now smooth the feather back into shape until the barbs rejoin. Use a hand lens or microscope to study the fine structure of the barbs. To get the best view through a hand lens, hold the lens close to one eye, then bring the object nearer until it comes in to focus. Do not lean over the object, but hold it up in a good light source.

Figure 3 Feather structure.

Q6 Suggest the function of the feather barbs.

Q7 What advantage is this structural adaptation to the bird?

Colour

The barn owl’s spotted, buff-coloured back may help to camouflage the female when on the nest, as this species often nests in hollows in trees lined with yellowish rotting wood.

Barn owls are found worldwide. They have even reached the Galapagos Islands, 400 miles off the coast of Ecuador. The Galapagos barn owl (Figure 4) looks a bit different from the British one.

Figure 4 Galapagos barn owl. The owl nests in caves within the dark volcanic rock that makes up the islands.

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Salters-Nuffield Advanced Biology Resources

Activity 4.5 Student Sheet

Eggs and incubation

Barn owls feed on small mammals, especially field voles. Field voles vary in numbers from year to year, with a peak population every fourth year, followed by a crash. The owls cannot predict how many voles there will be to feed their young when they start laying their eggs.

Many birds start to incubate their eggs only after the whole clutch is laid, so the chicks all hatch at about the same time. Barn owls start to incubate as soon as the first egg is laid. One egg is laid every 2–3 days, so the young hatch at 2–3 day intervals and the chicks differ considerably in size (Figure 5). This staggered egg laying is controlled by hormones.

(a) (b)

Figure 5 (a) Barn owl chicks. Notice the range of sizes. (b) Older barn owl young (owlets) in a nest-box, nearly ready to fly. These owlets were produced in a good vole year, and four have survived. By this stage they show some anxiety and make themselves as tall and imposing as possible (and make a hissing noise).

Q9 If it turned out to be a bad vole year, which of the owlets would survive? Why?

Q10 What might happen in a bad vole year if all the owlets were the same size?

Adaptations of the feet

Figure 6 The third toe of a barn owl, seen from below.

Q11 Use Figure 6, and your biological knowledge, to suggest how the middle toe of a barn owl is adapted to its functions.

Types of owl adaptation

Q12 We can classify adaptations as physiological (P), behavioural (B), or anatomical (A). State which of these three types of adaptation each of the following exemplifies:

a Good hearing

b Feather structure

c Competing for food

d Laying eggs at 2–3 day intervals

e Incubating immediately after the first egg is laid

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Salters-Nuffield Advanced Biology Resources

Activity 4.5 Student Sheet

Mimicry

Many of us have been stung by a wasp and have learnt to associate yellow and black stripes with a sting. We therefore tend to avoid touching any insect with this colour pattern. But do all insects with yellow and black stripes have a sting? The answer is no. Many insects mimic the bee and wasp colouring, but are quite harmless. These include many kinds of hoverflies. You may see these in a garden, collecting pollen from flowers.

Q13 What advantage does a hoverfly gain from mimicking the colour pattern of a wasp?

Stinging species are called the ‘models’. The harmless insects which look like the models are called the ‘mimics’. The models are mostly those with ‘wasp’ or ‘bee’ at the end of their name. Mimicry is an anatomical adaptation, but is closely linked to the behaviour of the predator. In this case the behaviour (avoiding insects with warning colouration) is probably not inherited, but is learned by experience, so it is not a genetic adaptation.

Q14 Suggest what might happen if the mimics became much more common than the models.

Q15 Many plants and fungi are poisonous, yet they do not usually have warning colouration. Suggest why plants and fungi do not usually warn herbivores in this way.

Note: some poisonous plants do have colours that may be warning to herbivores, for example, henbane has purple veins on its flowers and the famous poisonous fly agaric toadstool, Amanita muscaria, is red with white spots. However, most poisonous plants and fungi have no warning colouration at all. The deadly nightshade (Atropa belladonna) purple flowers look uninviting to humans, but the berries look quite tasty. Eating two or three berries would kill you.

Carnivorous plants

Carnivorous plants, such as sundews, pitcher plants and bladderworts, obtain their mineral nutrients – such as nitrates – by trapping and digesting small animals, such as insects. They are well adapted to their habitat.

Q16 Suggest where carnivorous plants might grow and why.

Q17 Which molecules in an animal’s body will provide nitrates to the plant when digested?

Q18 Suggest how the plants are able to break down all the molecules in the bodies of the captured animals.

Q19 Carnivorous plants do not grow in grassland and scrubland in the general countryside. Suggest why not.

Q20 Describe how a pitcher plant traps its prey.

Q21 Suggest why carnivorous plants usually have their flowers on a long stalk.

Try this

You can buy commercially grown carnivorous plants, such as sun-dew, venus fly-trap or pitcher plants. You can also buy seeds of some of these plants. Try growing them yourself. You will find out a lot about how they are adapted to their niche.

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Salters-Nuffield Advanced Biology Resources

Activity 4.5 Student Sheet

Spider’s web

A spider can construct a very complex sticky web using silk glands in its abdomen. Many spiders never see their parents, so this is a genetically inherited behavioural adaptation. They do not learn by copying the behaviour of other spiders. A garden spider can destroy her damaged web and make a new one in less than an hour. She usually makes a new one every day (Figure 7).

Figure 7 Web of a garden spider.

Q22 Explain how the production of a web helps the spider to survive.

Q23 Suggest why a spider eats the old web as she removes it to build a new one.

Niches and adaptations – True or false quiz?

For each of the following statements decide if it is true or false.

1 Mice have adapted to living in frozen food stores by growing extra thick fur.

2 Hedgehogs living near roads have stopped rolling up into a ball when they are alarmed – helping them to avoid being squashed by vehicles.

3 Some arctic fish have antifreeze in their blood.

4 There is a species of nematode worm which has only been found in German felt beer mats.

5 Midwife toads carry and hatch their spawn on their backs.

6 Hardy’s swift lays its eggs on the male’s back in the air and the young are reared entirely in the air.

7 A fungus that grows on old cow pats is able to fire its spores accurately towards chinks of light between the grass blades.

8 When alarmed, the woodcock (a wading bird) flies off carrying its young between its legs.

9 When plaice are put in an aquarium with chess boards covering the bottom, the plaice change their colour pattern to mimic the black and white squares.

10 Chameleons can swivel each eye independently when searching for insect prey.

11 A shark can detect blood in the water at a concentration of ten drops of blood in a large swimming pool.

12 Racing pigeons use landmarks to find their way home. Studies of marked birds have shown that they follow the M25 and turn off at major junctions leading towards their home.

13 The wild arum metabolises starch in part of its flower, called the spadix, raising its temperature. The heat helps to disperse a smell that attracts pollinating insects.

14 The strangler fig has been known to entwine sleeping people in Africa and squeeze them to death.

15 Jellyfish have specialised cells that shoot out a poison dart, paralysing their prey.

16 Starfish digest their prey by turning their stomachs inside out.

17 If sponges of two separate species are mixed together in a blender, they can reassemble themselves into sponges of separate species.

18 Slime moulds live as single amoeba-like cells most of their lives, but when they reproduce sexually all the cells join up to form a sporangium.

19 Some bacteria glow in the dark using an enzyme called luciferase.

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Salters-Nuffield Advanced Biology Resources

Activity 4.5 Teacher Sheet

ADAPTATIONS

Purpose

 To explain how an organism’s adaptations help it to survive.

 To communicate knowledge and ideas about adaptation.

 To develop presentation skills. There are two approaches to this activity.

SAFETY

Ensure students wash their hands thoroughly after handling animal or plant materials.

Part 1: Research and exhibit

The first part of the Student Sheet suggests that students choose and research the adaptations of an organism and mount an exhibition of their findings.

The exhibition space could be a public area, such as the school or college reception area, library, a corridor or display cases if available. The task should be given in plenty of time to allow good quality research and sourcing of interesting artefacts. If the exhibition is to be set up in a public area which is unsupervised, students need to plan and manage any health and safety issues related to the exhibits used. Discuss any health and safety considerations through with the students making sure they have considered all the potential risks.

Alternatively, it could be done as a post-conference style activity. In pairs, students prepare a poster presentation on one organism’s adaptation(s); these are shared with the rest of the group in an exhibition in class. For half the allotted exhibition time one student presents their poster while the other student circulates. The pair then switch roles. Students are encouraged to evaluate the effectiveness of the exhibition in achieving its aim of communicating knowledge and ideas about adaptations. The Student Sheet suggests the production of an evaluation form: this could be available as a feedback form for visitors to the exhibition or it could be an evaluation completed by the class to consolidate learning.

If less time is available, students could be allocated an organism with some reference material on hand so the task can be completed more quickly. An alternative in the lab would be to have a circus of biological specimens, photographs or video clips that students examine and comment on the specimens’ adaptations.

Part 2: Investigating adaptations

The second part of the Student Sheet illustrates adaptation using questions on a variety of different examples. There are also some short practical exercises.

When considering barn owl hearing, students could also test their own ability to judge direction and distance using only their hearing. Try the following procedure or a variation of it.

Students spread out around the lab or classroom and sit down. Decide on a noise to test, such as tapping the desk with a pencil. The subject of the experiment should sit near the centre of the room and close his/her eyes. One person at the front of the room writes the name of one member of the class on the board, who then taps with the pencil. The subject then opens their eyes and names the person they think did the pencil tapping. Repeat several times to get an overall impression of how well adapted humans are for locating sound.

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Salters-Nuffield Advanced Biology Resources

Activity 4.5 Teacher Sheet

The section on mimicry focuses on the familiar yellow and black colouring of bees and wasps. But three other main colour patterns seem to serve as warning colours in British insects. If pictures of insects are available, students could arrange them in to colour groups noting which are the models and which the mimics. The four colour groups that can be identified are: yellow and black, red and black, black and white, and brown (and black).

Answers

Q1 The facial disc of a barn owl works rather like the pinna of our ears, gathering sound waves and reflecting them towards the eardrum.

Q2 When it hears prey, the barn owl tilts its head and moves the ruff of feathers surrounding the facial disc, maximising the sound reaching its ears.

Q3 As the two ear holes are different the sound arriving at each of them will be slightly different. The owl uses this difference to detect the direction of the sound.

Q4 This helps the owl to detect the direction of the sound and so increases the chance that the owl will successfully locate and then catch its prey.

Q5 Sound from the wings might scare away its prey and prevent the owl from hearing its prey.

Q6 The barbules slide between each other and hook together, holding the parts of the feather together. If pulled too sharply the barbs separate rather than break. When they are stroked together, the barbs rejoin like a zip fastener.

Q7 The bards hold the parts together to make a smooth continuous surface. This helps the bird manoeuvre in the air when catching prey.

Q8 Galapagos barn owls nest in caves. The darker plumage acts as camouflage against the dark rocks and they are less likely to be seen by predators. Darker barn owls are less likely to be seen by their prey among the dark volcanic rocks. The difference in colour may be due to chance – the owls which happened to reach the Galapagos Islands were darker than average.

Q9 The largest is likely to survive because the owlets compete for food; the largest will get more of the food, leaving the smaller chicks to starve. In some cases the larger owlets eat the smaller ones! This means that at least some of the owlets survive.

Q10 If the owlets were all the same size they would all get about the same amount of food and if insufficient they would all starve. So the hatching interval in barn owls is an adaptation to an unpredictable food supply.

Q11 There are several features that could be discussed. These include:

 bristles are used for touch sense, assisting the detection of moving prey

 tubercles on the underside of the toe are used for gripping prey (compare with your fingerprints and the surface of a rubber glove)

 claw is used for gripping and killing prey

 serrations on the claw are used for grooming the feathers of the facial disc (this comb is present only on the third toe of each foot).

Q12 a Good hearing – P and A.

b Feather structure – A.

c Competing for food – A, B and P.

d Laying eggs at 2–3 day intervals – P.

e Incubating immediately after the first egg is laid – B.

f Toe structure – A (but closely related to B).

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Salters-Nuffield Advanced Biology Resources

Activity 4.5 Teacher Sheet

Q14 Mimicry would become less advantageous, as predators would be slower to learn to avoid the colour pattern.

Q15 Herbivores may take a small piece from a plant or fungus, then stop eating if it is distasteful. This small sample is unlikely to kill the plant, so there is no strong selection pressure for plants to produce warning colours.

Q16 Carnivorous plants live in habitats where nutrients are in very short supply. Here are some examples. Sundew and butterwort live on wet moorland, where dead plant material is very slow to decay, so the nutrients are not released. Pitcher plants live in tropical forests, where the high rainfall washes away nutrients very quickly. Bladderwort lives in freshwater ponds and lakes, where other plants remove nutrients more quickly than they are replaced. They can survive in these habitats because they obtain nutrients from the animals trapped and digested.

Q17 Proteins, amino acids, nucleic acids.

Q18 The plant produces a range of enzymes rather like an animal gut, including protease, lipase and carbohydrase.

Q19 In places where there are lots of nutrients, carnivorous plants are out-competed by more vigorous plants. In places with low nutrients, these vigorous plants cannot grow, so the carnivorous plants have a competitive advantage.

Q20 The pitcher plant has specially adapted leaves – pitchers of fluid containing enzymes. Around the edge of the pitcher sugar is released, attracting insects, but the edge is slippery so the insects fall in. The largest pitcher plant in the world is Nepenthes raja in Borneo, which sometimes traps rats.

Q21 The flowers are kept well away from insect traps, since it would be a disadvantage for the plant to trap its own pollinators.

Q22 The web allows a spider to trap its food without having to chase its prey.

Q23 The web is made of silk (protein) and uses up a lot of the spider’s food resources. It can use the old web as a source of food.

Niches and adaptations – True or false quiz?

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Salters-Nuffield Advanced Biology Resources

Activity 4.5 Technician Sheet

ADAPTATIONS

Purpose

 To explain how an organism’s adaptations help it to survive.

 To communicate knowledge and ideas about adaptation.

 To develop presentation skills.

SAFETY

Wash your hands thoroughly after handling animal or plant materials.

There are two approaches suggested on the Student Sheet. The first involves students choosing and researching the adaptations of an organism, and mounting an exhibition of their findings. Teachers may wish to allocate the students an organism to research so a variety of biological specimens or photographs as stimulus material would be useful. Alternatively, a circus of biological specimens, photographs or video clips could be provided that students examine and comment on their adaptations. The second part of the Student Sheet illustrates adaptation using questions on a variety of different examples. There are also some short practical exercises.

Examine a flight feather of a bird

Requirements per student or

group of students Notes

A bird’s flight feather

Hand lens or binocular microscope To view the barbs on the feather.

Mimicry

Requirements per student or

group of students Notes

Photo or drawings of a wide range of insects

BBC wildlife magazine produced a good poster showing bees, wasps and mimics.

Carnivorous plants

Requirements per student or

group of students Notes

Seeds or small specimens of carnivorous plants

These can be bought at garden centres.

Suitable pots, trays and compost This will depend on the plants to be grown. Fruitfly (Drosophila) colony or other

source of insect food

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Salters-Nuffield Advanced Biology Resources

Activity 4.6 Student Sheet

NATURAL SELECTION IN ACTION

Purpose

 To demonstrate natural selection.

YOU NEED

● Large piece of patterned paper

● 50 cut-out pieces of the same patterned paper

● 50 cut-out pieces of white paper (of the same size and weight as the patterned paper)

● Partner to lay out the equipment and time the activity

● Pair of forceps

● Stopclock

● Beaker

1 Natural selection card sort

Confirm your understanding of the principles of natural selection by putting the cards describing the adaptation of head lice to head lice shampoos, on the next page, in the correct order. Then look at pages 159–160 in the Student Book to check that you got the order right.

2 Natural selection in the classroom

In this activity a predator (you) is presented with a prey population with two different phenotypes, one camouflaged and one which stands out from the habitat background. The predator is given a fixed length of time to find as many prey items as they can.

Procedure

1 Lay out the patterned paper, pattern side up; this represents the habitat.

2 Mix the coloured and uncoloured paper pieces together and put them on the patterned paper. Ensure that the patterned pieces are pattern side up.

3 Give the ‘predator’ 15 seconds to pick up as many pieces of paper as possible using the forceps and put them in a beaker.

4 Count the number of each colour of paper in the beaker and record your results.

5 Replace the ‘eaten’ pieces of paper and rearrange the pieces of paper on the background.

6 Repeat steps 2 to 4 several times.

7 Comment on your results and answer the questions that follow.

Questions

Q1 How many coloured and uncoloured pieces of paper were picked up and put in the beaker over the course of the whole experiment (this is your observed value)?

Q2 How many of each colour would you expect if there were no advantage to being camouflaged (this is your expected value)?

Q3 How could you tell if the difference is statistically significant?

3 Using pastry ‘maggots’ and birds as predators

Pastry ‘maggots’ can be made quite easily using a flour, fat and water dough; your teacher/lecturer can give you a recipe. Design (and you may get a chance to carry out) an experiment to investigate natural selection using different coloured pastry ‘maggots’ for garden birds to ‘prey’ upon. The ‘maggots’ can either be put out on coloured backgrounds or directly on grass for birds to be the predators.

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Salters-Nuffield Advanced Biology Resources

Activity 4.6 Student Sheet

Head lice cards

a The few remaining head lice survive because they happen to have alleles that make them resistant to the chemicals.

b There is a lot of genetic variation in the head louse population due to the large number of different alleles.

Head lice and natural selection

c The survivors get together and breed. They produce offspring that inherit the alleles that make them resistant to the chemical.

d Over the centuries many different mutations have produced different alleles.

e Soon, virtually all head lice are resistant to the chemicals.

f The alleles for resistance to the chemical become more common in the population.

g Now when people use the shampoo it does not kill the head lice.

h Head lice have become a problem once again. This is an example of natural selection at work.

i Head lice have been infesting peoples’ heads for millennia.

j Drug companies develop shampoos containing chemicals which kill the head lice.

Figure

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References

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