chapter 10 p5

Question 1

behavioural adaptations fall into two main categories:

Answer 1

Innate (or instinctive) behaviour
Learned behaviour

However, many behavioural adaptations are a combination of both innate and learned behaviours.

Question 2

Innate (or instinctive) behaviour

Answer 2

the ability to do this is inherited through genes.
For example, the behaviour of spiders to build webs and woodlice to avoid light is innate.
This allows the organism to survive in the habitat in which it lives.

Question 3

Learned behaviour

Answer 3

• these adaptations are learnt from experience or from observing other animals.
  An example of learned behaviour is the use of tools.
  For example, sea otters use stones to hammer shells off rocks, and then to crack the hard shells open.

Question 4

Physiological adaptations:
Some examples of physiological adaptations:

Answer 4

Poison production
Antibiotic production
Water holding
Many other examples are less unusual, and include reflexes, blinking and temperature regulation.

Question 5

Poison production

Answer 5

many reptiles produce venom to kill their prey and many plants produce poisons in their leaves to protect themselves from being caten.

Question 6

Antibiotic production

Answer 6

some bacteria produce antibiotics to kill other species of bacteria in the surrounding area.

Question 7

Water holding

Answer 7

the water-holding frog (Cyclorana platycephala) can store water in its body. This allows it to survive in the desert for more than a year without access to water. Many cacti and other desert plants can hold large amounts of water in their tissues.

Question 8

How Anatomical adaptations provide evidence for convergent evolution
Analogous structures:
p1

Answer 8

• Although the tail fins of a whale and a fish perform the same role, when you look at them in detail their structures are very different.
• These are known as analogous structures - they have adapted to perform the same function but have a different genetic origin.
• Convergent evolution takes place when unrelated species begin to share similar traits.
• These similarities evolve because the organisms adapt to similar environments or other selection pressures
• The organisms live in a similar way to each other.
• Using our example of whales and fish, their similar characteristics have evolved over time to allow the organisms to move efficiently through water.
• Marsupials in Australia and placental mammals in the Americas are an example of convergent evolution.
• Species in each continent resemble each other because they have adapted to fill similar niches.

Question 9

How Anatomical adaptations provide evidence for convergent evolution
Analogous structures:
p2

Answer 9

• In placental mammals, a placenta connects the embryo to its mother’s circulatory system in the uterus.
• This nourishes the embryo, allowing it to reach a high level of maturity before birth.
• Marsupials also start life in the uterus, but then leave and enter the marsupium (pouch) while they are still embryos.
• They complete their development here by suckling milk.
• These two subclasses of mammals separated from a common ancestor more than 100 million years ago.
• Each lineage then evolved independently.
• Despite this large temporal and geographical separation, marsupials in Australia and placental mammals in North America have produced varieties of species that bear a strong resemblance in overall shape, type of locomotion and feeding techniques.
• This is because they have adapted to similar climates and food supplies.
• However, these organisms have very different methods of reproduction.
• This is the feature that accurately reflects their distinct evolutionary relationships.

Question 10

Examples include:

Answer 10

marsupial and placental mice
flying phalangers and flying squirrels
marsupial and placental moles

Question 11

marsupial and placental mice

Answer 11

both are small, agile climbers that live in dense ground cover and forage at night for small food items.
The two mice are very similar in size and body shape

Question 12

flying phalangers and flying squirrels

Answer 12

both are gliders that eat insects and plants.
Their skin is stretched between their forelimbs and hind limbs to provide a large surface area for gliding from one tree to the next

Question 13

marsupial and placental moles

Answer 13

both burrow through soft soil to find worms and grubs.
They have a streamlined body shape and modified forelimbs for digging.
They also have velvety fur, which allows smooth movement through the soil.
However, they differ in fur colour - the marsupial mole ranges in colour from white to orange whereas the placental mole is grey.

Question 14

Where are Convergent evolution can also be seen:

Answer 14

in some plant species.
For example, aloe and agave appear very similar as they have both adapted to survive in the desert.
However, these species developed entirely separately from each other. Aloe are sometimes referred to as ‘old world’, having evolved in sub-Saharan Africa. Agave, by comparison, are ‘new world’, having evolved in Mexico and the southern United States.

Question 15

Classification of giant pandas: p1

Answer 15

• Classification aims to place every organism into a particular taxonomical group.
• However, there are a number of organisms that do not fit easily into a group.
• An example of this is the giant panda (Ailuropoda melanoleuca - Figure 10, top).
• Père Armand David, a catholic priest, was the first westerner to see a giant panda.
• He discovered the panda in 1869, and based on its appearance he concluded that it was related to a bear (family Ursidae - Figure 10,
• He gave it a name that included the word ursus (the Latin word for bear).
• A few years later, Alphonse Milne-Edwards, a French scientist, inspected the remains of a giant panda.
• He concluded that its anatomical structure was closer to the red panda (Figure 10, middle), a member of the raccoon family.
• He renamed the giant panda, and classified it into its own category.
• Many people disagreed with Milne-Edwards’ conclusion because of its size.
• Red pandas have a mass of between 3 and 7 kg - the largest raccoons have a mass of around 30 kg.
• By comparison, the giant pandas can exceed 100 kg body mass
• The debate over the classification of the giant panda has continued for several decades.

Question 16

Similarities to a red panda:

Answer 16

Both eat bamboo and grip bamboo in the same manner.
Both have similar snouts, teeth and paws.

Question 17

Similarities to a bear:

Answer 17

Both are a very similar shape and size.
Both have shaggy fur.
Both walk and climb in a similar manner.

Question 18

Classification of giant pandas p2

Answer 18

• Giant pandas and red pandas may have developed similar ways of eating bamboo separately as a result of convergent evolution.
• Equally, convergent evolution could explain their resemblance to bears.
• In the 1950s, the first molecular-level analysis of the giant panda occurred.
• Biologists used an immunological method to assess the closeness of bears to pandas.
• Through studying blood serum, they concluded that the ‘serological affinities of the giant panda are with the bears rather than with the raccoons’.
• The giant panda is therefore a true bear and part of the Ursidae family, although it differentiated early in history from other bears.
• Despite the shared name, habitat type, and diet, as well as a unique enlarged bone called the pseudo thumb (which helps them grip bamboo shoots], the giant panda and red panda are only distantly related.
• Molecular studies place the red panda in its own family - Ailuridae

Question 19

explain why a particular characteristic has increased in a population

Answer 19

first identify the adaptation.
Then explain how it helps the organism to survive and reproduce so that the organism can pass on the allele coding for the characteristic to the next generation.
Finally, state how this increases the allele’s frequency in the population.

Question 20

Natural selection:

Answer 20

• All organisms are exposed to selection pressures.
• These are factors that affect the organism’s chances of survival or reproductive success (the ability to produce fertile offspring).
• Organisms that are best adapted to their environment are more likely to survive and reproduce.
• As a result of natural selection these adaptations will become more common in the population.
• Organisms that are poorly adapted are less likely to survive and reproduce.
• Therefore their characteristics are not passed on to the next generation.
• As a result, less of the population will display these characteristics.

Question 21

number of steps Natural selection follows:

Answer 21

• Organisms within a species show variation in their characteristics that are caused by differences in their genes (genetic variation).
• For example, they may have different alleles of a gene for a particular characteristic.
• New alleles can arise by mutation.
• Organisms whose characteristics are best adapted to a selection pressure such as predation, competition (for mates and resources) or disease, have an increased chance of surviving and successfully reproducing.
• Less well-adapted organisms die or fail to reproduce.
• This process is known as ‘survival of the fittest’.
• Successful organisms pass the allele encoding the advantageous characteristic onto their offspring.
• Conversely, organisms that possess the non-advantageous allele are less likely to successfully pass it on.
• This process is repeated for every generation.
• Over time, the proportion of individuals with the advantageous adaptation increases.
• Therefore the frequency of the allele that codes for this particular characteristic increases in the population’s gene pool.
• Over very long periods of time, many, many generations and often involving multiple genes, this process can lead to the evolution of a new species.

Question 22

Modern examples of evolution
Antibiotic-resistant bacteria:

Answer 22

• Methicillin-resistant Staphylococcus aureus (MRSA) has developed resistance to many antibiotics.
• Bacteria reproduce very rapidly and so evolve in a relatively short time.
• When bacteria replicate, their DNA can be altered and this usually results in the bacteria dying.
• However, a mutation in some S. aureus arose that provided resistance to methicillin.
• When the bacteria were exposed to this antibiotic, resistant individuals survived and reproduced, passing the allele for resistance on to their offspring.
• Non-resistant individuals died.
• Over time the number of resistant individuals in the population increased.

Question 23

Peppered moths:

Answer 23

• Dramatic changes in the moth’s environment in the 19th century caused changes in allele frequency in peppered moths (Biston betularia).
• Before the industrial revolution, most peppered moths in Britain were pale coloured.
• This provided camouflage against light-coloured tree bark, increasing their chance of survival.
• Those that were dark were easily spotted by birds and eaten.
• The different colourings are due to different alleles.
• During the industrial revolution many trees became darker - partly due to being covered in soot, and partly due to the loss of lichen cover caused by increased atmospheric pollutants.
• The dark moths were now better adapted, as they were more highly camouflaged.
• More dark peppered moths survived and reproduced, increasing the frequency of dark moths (and the dark’ allele) in the population.
• After a few years the number of dark peppered moths close to industrial towns and cities became much higher than pale peppered moths.
• Since the Clean Air Act of 1956 steps have been taken to improve air quality in towns and cities, and to reduce the levels of pollution released from factories.
• The bark on the vast majority of trees in the UK is once again lighter coloured, and therefore the frequency of the pale allele in the moth gene pool has increased.

Question 24

Sheep blowflies:

Answer 24

• Sheep blowflies (Lucilia cuprina) lay their eggs in faecal matter around a sheep’s tail - the larvae then hatch and cause sores.
• This condition is known as ‘flystrike’, and if left untreated is normally fatal.
• In the 1950s in Australia, the pesticide diazinon (an organophosphate pesticide) was used to kill the blow flies and prevent the condition.
• Within six years, blowflies had developed a high level of resistance to diazinon.
• Individual insects with resistance survived exposure to the insecticide, and passed on this characteristic through their alleles, allowing a resistant population to evolve.
• To investigate how this evolution occurred so quickly, scientists extracted DNA from a sample of 70-year-old blowflies kept at the Australian National Insect Collection.
• Two Australian sheep blowflies were studied, Lucilia cuprina and the closely related Lucilia sericata.
• The researchers compared the blowflies’ resistance genes before and after the introduction of the pesticide.
• Diazinon resistance was not found in the DNA of the 70-year-old flies, whereas it is present in the modern species.
• However, when they performed the same investigation with malathion (another organophosphate pesticide), they found resistance alleles in both the old and modern blowflies, showing there was pre-existing resistance to this chemical.
• The scientists concluded that pre-adaptation contributed to the development of diazinon-resistance.
• Pre-adaptation is when an organism’s existing trait is advantageous for a new situation.
• The alteration in the DNA that caused the pre-existing resistance allowed the flies to rapidly develop resistance to organophosphate chemicals in general, and ultimately a specific diazinon-resistance allele.
• The existence of pre-adaptation in an organism may help researchers predict potential insecticide resistance in the future.

Question 25

Flavobacterium:

Answer 25

• Most evolution occurs as a negative result of selection pressures.
• However, some organisms have evolved due to opportunities that have arisen in their environment.
• For example, scientists have found a new strain of Flavobacterium living in waste water from factories that produce nylon 6.
• Nylon 6 is used to make objects like toothbrushes and violin strings.
• This strain of bacteria has evolved to digest nylon and is therefore beneficial to humans as they help to clear up factory waste.
• These bacteria use enzymes to digest the nylon known as nylonases.
• They are unlike any enzymes found in other strains of Flavobacterium, and they do not help the bacteria to digest any other known material.
• It is beneficial to the bacteria as it provides them with another source of nutrients.
• Most scientists believe that the gene mutation that occurred to produce these enzymes was a result of a gene duplication, combined with a frameshift mutation (an insertion or deletion of DNA bases that causes the genetic code to be read incorrectly).

Question 26

Anolis lizards:

Answer 26

• When a few individuals of a species colonise a new area, their offspring initially experience a loss in genetic variation, often resulting in individuals that are physically and genetically different from their source population.
• This is known as the founder effect.
• A 14-year experiment led by Kolbe, a biologist at the University of Rhode Island) was carried out to study evolution.
  Pairs of Anolis sagrei were released across 14 small Caribbean islands that had no previous lizard populations.
• During the experiment, the lizard populations each became adapted to their respective environments through changes in their body shape driven by the flora in their environment.
• Several new species of lizards evolved.
• To determine how much of the evolution of the new species was due to the founder effect, and how much resulted from natural selection, Kolbe randomly selected pairs of Anolis lizards from the island of Iron Cay.
• He then released these organisms onto seven smaller islands that had no lizard population.
• Each island had the same types of insects, birds and short scrub vegetation but differed from Iron Cay, which is covered in forest.
• Forest Anolis lizards have long hind limbs, which allow them to move quickly across thick branches, whereas short limbs give scrub-living lizards stability to walk along narrow perches.
• The scientists therefore predicted that the lizards in their experiment would develop shorter hind limbs than those of the lizards on Iron Cay.
• After one year, the researchers noticed that the offspring of the experimental lizards had less genetic variability than the Iron Cay lizards - the founder effect.
• There were also significant differences in hind-limb length among the lizards on the islands.
• As the founder effect is a random process independent of the environment, there was no pattern to the length of the lizards’ hind limbs.
• Over the next few years the lizards’ hind limbs on all the experimental islands got shorter, making them better suited for their environment - natural selection.
• A Figure 3 A male Anolis lizard (Anolis sagrei) displaying its eye-catching dewlap. When enlarged it makes the lizard appear much bigger than it really is.
• This mechanism is used to ward off predators and to attract females during the mating season
• Kolbe concluded that both processes were evident during the experimental period.