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Question 1

Describe four processes needed for the spontaneous origin of life on Earth

Answer 1

The synthesis of simple organic moleculesThe assembly of these organic molecules into polymersThe formation of polymers that can self-replicate, enabling inheritancePackaging of these molecules into membranes with an internal chemistry different from their surroundings

Question 2

Outline the experiments of Miller and Urey into the origin of organic compounds

Answer 2

• Miller and Urey recreated the conditions of pre-biotic Earth in a closed system • These conditions included a low-oxygen atmosphere, high radiation levels, high temperatures and electrical storms • Water was boiled to form vapour and then was mixed with methane, ammonia and hydrogen to form a reducing atmosphere • The mixture of gases was exposed to an electrical discharge (sparks) to simulate lightning • The mixture was then allowed to cool and after one week was found to contain some simple amino acids and complex oily hydrocarbons • Based on these findings, it was concluded that under the hypothesised conditions of pre-biotic Earth, organic molecules could be formed

Question 3

State that comets may have delivered organic compounds to Earth

Answer 3

• Comets contain a variety of organic molecules (~20% of a comet’s tail is comprised of organic material) • Heavy bombardment about 4,000 million years ago may have delivered both organic compounds and water to early Earth

Question 4

State the conditions required for the synthesis of organic molecules

Answer 4

Organic synthesis requires the presence of a range of inorganic molecules and an energy source to combine them into organic forms

Question 5

Discuss possible locations where conditions would have allowed for the synthesis of organic compounds

Answer 5

• Hydrothermal vents - Regions of the ocean floor where superheated water is released from the Earth’s crust • Volcanoes - Intensive volcanic activity could provide sufficient thermal activity either on land or under the seabed • Extra-terrestrial locations - Other planets (e.g. Mars) may have been subjected to appropriate conditions (compound transfer via meteorites)

Question 6

State two properties of RNA that would have allowed it to play a role in the origin of life

Answer 6

RNA canself-replicateRNA can act as acatalyst

Question 7

Outline how RNA’s self-replicating properties would have allowed it to play a role in the origin of life

Answer 7

• One molecule can form a template for the production of another molecule, following the rules of complementary base pairing • Can store information in the form of a base sequence

Question 8

Outline how RNA’s catalytic properties would have allowed it to play a role in the origin of life

Answer 8

• Could have taken the role which is now carried out by proteins (enzymes) • Modern cells use RNA catalysts (called ribozymes) to remove introns from mRNA and help synthesise new RNA molecules

Question 9

Outline the theory of protobionts as preceding living cells

Answer 9

• Living cells may have been preceded by protobionts • Protobionts are aggregates of abiotically produced organic molecules surrounded by a membrane or membrane-like structure. • A membrane creates an internal chemical environment different to the surroundings, which could lead to optimal conditions for life activities.

Question 10

Outline how prokaryotes to the creation of an oxygen-rich atmosphere

Answer 10

• Primordial Earth had a reducing atmosphere that contained very low levels of oxygen gas • After about ~2 billion years of prokaryotic life, a form of chlorophyll evolved in prokaryotes • This allowed for photosynthesis to occur, creating oxygen gas as a by-product via the photolysis of water

Question 11

Outline the result of the creation of an oxygen-rhc atmosphere ~2 billion years ago

Answer 11

• The breakdown of chemicals in the atmosphere and oceans to produce oxidised compounds (e.g. CO2) • The evolution of organisms capable of performing aerobic respiration • The formation of an ozone layer which restricted UV radiation to allow for the proliferation of a wider range of life forms

Question 12

Discuss the endosymbiotic theory for the origin of eukaryotes

Answer 12

• An endosymbiont is a cell which lives inside another cell with mutual benefit • Eukaryotic cells are believed to have evolved from aerobic prokaryotes that were engulfed by endocytosis • Mitochondria and chloroplasts are suggested to have originated by endosymbiosis

Question 13

State three pieces of evidence for the endosymbiotic theory

Answer 13

• Mitochondria and chloroplasts have their own DNA which is naked and circular (like prokaryotes) • Mitochondria and chloroplasts have 70s ribosomes • Mitochondria and chloroplasts are roughly the same size as bacteria

Question 14

Define allele frequency

Answer 14

The proportion of an allele within a population

Question 15

Define gene pool

Answer 15

All the alleles present in an interbreeding population

Question 16

Outline how natural selection results in a change in allele frequency in a population’s gene pool over a number of generations

Answer 16

• By natural selection, alleles encoding for beneficial adaptations will result in a survival advantage and lead to improved reproduction • These alleles are consequently more likely to be inherited and thus the population’s gene pool will change over generations

Question 17

Discuss limitations of the definition of ‘species’

Answer 17

• Certain organisms (e.g. bacteria) produce asexually and therefore they do not interbreed • Some organisms are only known through fossil records, making it impossible to ascertain breeding capacity • ‘Sibling species’ look identical but don’t interbreed • Some distinct species can interbreed and produce fertile offspring • Geographically isolated organisms may never come into contact, meaning there is no information regarding their ability to interbreed

Question 18

State three barriers to gene pools

Answer 18

Temporal isolation, behavioural isolation, mechanical isolation

Question 19

Describe temporal isolation

Answer 19

Occurs when two species mate or flower at different timesE.G. Different frog species live in the same pond but breed at different times

Question 20

Describe behavioural isolation

Answer 20

Occurs when two species respond to different specific courtship patternsE.G. Some crickets are morphologically identical but only respond to species specific mating songs

Question 21

Describe mechanical isolation

Answer 21

Occurs when genital differences prevent copulation (animals) or when flowers are pollinated by different animals (plants)E.G. Galagos have distinctly shaped genitalia that will only fit other members from the same species

Question 22

Explain how polyploidy can contribute to speciation

Answer 22

• Polyploidy is a condition in which an organism has more than two complete sets of chromosomes in all somatic cells • It is far more common in plant species as theylack separate sexes and are capable of asexual reproduction (self-pollination) • It may occur as a result of the failure of a meiotic cell to undergo cytokinesis (so chromosome replication occurs minus cell division) • Consequently gametes are diploid (2n) and resulting offspring are tetraploid (4n) • Because tetraploid offspring can no longer mate with diploid organisms(triploid offspring tend to be infertile), speciation has occurred

Question 23

Outline allopatric speciation

Answer 23

Caused by geographical separation of populationsPopulations occupy different geographic areasE.G. Adaptive radiation of Galapagos finches

Question 24

Outline sympatric speciation

Answer 24

Involves a reproductive, temporal or behavioural separationPopulations occupy the same geographical areasExample: Polyploidy in wheat strains

Question 25

State a similarity between allopatric and sympatric speciation

Answer 25

Both involve the formation of a new speciesvia isolation of the gene pool from an existing species

Question 26

Define speciation

Answer 26

The formation of new and distinct species in the course of evolution by the splitting of an existing species

Question 27

Outline the process of adaptive radiation

Answer 27

• Adaptive radiation describes a rapid evolutionary diversification of a single ancestral lineage • It occurs when members of a single species occupy a variety of niches with different environmental selection pressures • Consequently, members evolve different morphological adaptations as a result of natural selection • Adaptive radiation results in speciation (many species from an ancestral line) and may be further enhanced by reproductive isolation • An example of adaptive radiation can be seen in the variety of beaks seen in the Galapagos finches

Question 28

Outline convergent evolution

Answer 28

Different ancestorConverge to produce analogous structuresSpecies appearance becomes more similar over timeSpecies are unrelated (genetically different)Example: Wings in insects, birds and bats

Question 29

Outline divergent evolution

Answer 29

Common ancestorDiverge to produce homologous structuresSpecies appearance becomes more different over timeSpecies are closely related (share genetic homology)Example: Pentadactyl limb structure in vertebrates

Question 30

Outline gradualism as a pace of evolution

Answer 30

• Continuous change at aconstant paceover a long period of time • Arises as a result of the gradual accumulation of mutations / variations • Examples in the fossil record of gradual change with intermediate forms support this theory • An example is the evolution of the modern horse (gradual change in size and foot structure with changing habitat)

Question 31

Outline punctuated equilibrium as a pace of evolution

Answer 31

• Evolution proceedsrapidly in burstsfor short periods of time, intermittent with long periods of stability • In periods of stability organisms become well suited to the environment, with natural selection acting to maintain characteristics • Equilibrium is punctuated by a rapid environmental change (e.g. volcanic eruption, meteor impact) which leads to directional selection • Gaps in the fossil record and the lack of intermediate forms for many species support this theory • Strata in the fossil record that show the appearance of many new species following a mass extinction support this theory

Question 32

Define transient polymorphism

Answer 32

• A situation when there are two alleles in a gene pool (polymorphic) and one allele is gradually replacing another • This is due to a strong environmental selective pressure causing directional selection to eliminate one allele

Question 33

Outline an example of transient polymorphism

Answer 33

Antibiotic resistance in bacteria

Question 34

Define balanced polymorphism

Answer 34

• A situation when there are two alleles in a gene pool (polymorphic) and the frequency of the two alleles in not changing • Occurs when selective pressures promote the coexistence of the two alleles (i.e. heterozygous advantage) causing a stabilising selection

Question 35

Outline an example of balanced polymorphism

Answer 35

• Sickle cell anaemia is controlled by a single gene mutation • Individuals homozygous for the sickle cell allele have abnormally shaped red blood cells that cause anaemia • Individuals homozygous for the normal blood cell allele are highly susceptible to malarial infection • Malaria parasite is less successful at infecting sickle-shaped blood cells • In areas where malaria is common, heterozygous individuals experience an advantage over either form of homozygote • These individuals are more likely to survive and reproduce, leading to a balance in the frequency of the two alleles (heterozygous advantage)

Question 36

Outline the method of radiocarbon dating for dating rocks and fossils

Answer 36

• All living things are built from carbon-based organic matter • While alive, this carbon content exists as a mixture of two isotopes -12C(stable) and14C(radioactive) - maintained in constant proportions • When an organism dies, the proportion of radioactive14Cbegins to decrease as it is no longer being replaced from the environment • The proportion of14Cremaining can be used to identify the age of a sample • Carbon-14 analysis is only an effective means of dating for sample up to ~60,000 years of age as it has a half life of only 5,730 years

Question 37

Outline the method of potassium-argon dating for dating rocks and fossils

Answer 37

• Longer range dating can be accomplished by dating the rocks around a fossil to determine an age range (i.e. relative dating) • These dating techniques can only be undertaken on igneous rocks, not on the fossils themselves or the sedimentary rock in which they are found • 40K is released in lava from active volcanos and decays into40Ar with a half life of 1,300 million years • Using the time of the volcanic eruption as a zero time point, the age of the strata in which the fossil was found can be determined • As any40Ar would have been released during the eruption as a gas, levels of40Ar in the strata provide an indication of relative age

Question 38

Define half-life

Answer 38

The half life of a radioisotope is a measure of the time taken for the radioactivity to fall to half its original levelIn other words, it is a measure of the time taken for half the atoms in a radioactive sample to decay

Question 39

Describe the major anatomical features that define humans as primates

Answer 39

• Forward facing eyes, giving stereoscopic vision • Large brain volume relative to body • Opposable thumbs capable of grip

Question 40

Outline the trends illustrated by the fossils of Ardipithecusradius, Australopithecus including A. afarensis and A. africanus, and Homo including H. habilis, H. erectus, H. neanderthalensis and H. sapiens

Answer 40

fckn do it

Question 41

State that, at various stages in hominid evolution, several species may have coexisted

Answer 41

Several species of hominid may have co-existed at the same time: • Homo habilismay have co-existed with various species ofAustralopithicus • Homo neanderthalensislikely co-existed withHomo sapiens

Question 42

Discuss the incompleteness of the fossil record

Answer 42

• Fossilisation is an exceptionally rare occurrence that requires an unusual combination of special conditions • Most living things tend to decompose rapidly (or be scavenged) following death • Fossilisation tends to favour hard body parts (bone, teeth, shells, etc.) and exposed fossils will soon be weathered / destroyed • Only a small percentage of fossils have been discovered - fossilisation favours species that were long-lived and widespread

Question 43

Discuss uncertainties about human evolution resulting from the incompleteness of the fossil record

Answer 43

• Individual fossils may not be representative of species (e.g.Homo floresiensis- ‘Hobbit’ man) • Very few complete skeletons have been discovered, and so paleoanthropology is an inductive (data-poor) science • Many conclusions have been drawn on limited data and are frequently re-interpreted in the light of new discoveries

Question 44

Discuss the correlation between the change in diet and increase in brain size during hominid evolution

Answer 44

• A change in habitat in Africa ~2.5 million years ago may have prompted the emergence of Homo species from forest to savannah • This necessitated a change of diet to include meat (more protein), which increased the skull capacity and brain size of hominids • Improved diet quality provided energy to support greater brain function and learning capacity (positive correlation) • Activities resulting from improved cognition (such as group hunting and cooking food) enabled hominids to eat a wider variety of food

Question 45

Distinguish between genetic and cultural evolution

Answer 45

Genetic evolutioninvolves physical changes in the human genome which become inherited (passed on through reproduction). It involves the transfer of genes from one generation to the next (slow transfer).Cultural evolutioninvolves changes in human thinking and can be passed on by communication/social interaction. It involves the transfer of ideas/information either within or across many generations (fast transfer).

Question 46

Discuss the relative importance of genetic and cultural evolution in the recent evolution of humans

Answer 46

FINISH THIS MOTHERFUCKIN DOT POINT

Question 47

Do the Hardy-Weinberg Principle thing

Answer 47

LEARN HOW TO DO THIS BITCH

Question 48

Outline the value of classifying organisms

Answer 48

• Allows us to distinguish between and compare organisms • Makes it easier to identify organisms • Makes it easier to collect, sort and store information about organisms • Shows how closelyorganisms are related and suggests evolutionary links • Allows predictions to be made about characteristics of members of a group

Question 49

Explain the biochemical evidence provided by the universality of DNA and protein structures for the common ancestry of living organisms

Answer 49

• The genetic code is universal • All organisms use DNA and/or RNA as their genetic material • The same four bases are used • The same codons code for the same amino acids • All living organisms use the same 20 amino acids for protein synthesis

Question 50

Explain how variation in specific molecules can indicate phylogeny

Answer 50

• Phylogeny is tracing evolutionary links and origins by comparing similar molecules from different species • Variations in these molecules (either base or amino acid sequence) will occur due to mutations which accumulate over time • The greater the differences between the common molecules, the longer the time span since the two species had a common ancestor • Mitochondrial DNA is useful for tracing phylogeny as it is inherited via the maternal line, lacks recombination and has a known mutation rate

Question 51

Outline how biochemical variation can be used as an evolutionary clock

Answer 51

• Some genes accumulate mutations at a relatively constant rate • If this rate of change is known, scientists can calculate the time of divergence between two species based on the number of differences

Question 52

Discuss limitations of the evolutionary clock concept

Answer 52

• The rate of change can differ for different groups of organisms (e.g. animals and plants) • The rate of change can vary between different genes • Over long periods, earlier changes may be reversed by later changes

Question 53

Define clade

Answer 53

A group of organisms all descended from a common ancestor

Question 54

Define cladistics

Answer 54

A method of classification of living organisms based on the construction and analysis of cladograms

Question 55

Distinguish between analogous and homologous structures

Answer 55

Analogous from different ancestor (convergent evolution), homologous come from common ancestor (divergent evolution. Analogous have similar function but different structure, homologous don’t have similar function but do have similar structure.

Question 56

Give an example of analogous characteristics

Answer 56

Wings in bats, birds, insects

Question 57

Give an example of homologous characteristics

Answer 57

Pentadactyl limb in vertebrates

Question 58

Discuss the relationship between cladograms and the classification of living organisms

Answer 58

• Classification was traditionally based on morphology (structural characteristics) • Methods used to construct cladograms typically utilise a different approach (e.g. molecular data - more objective) • Cladograms can show ancestral relationships and reflect how recently two groups shared a common ancestry • As such they should be considered a good complement to traditional classification schemes • In some cases, cladograms have lead to revisions in scientific classifications

Question 59

Define stimulus

Answer 59

A change in the environment (external or internal) that is detected by a receptor and elicits a response

Question 60

Define response

Answer 60

A change in an organism (an action) resulting from a stimulus

Question 61

Define reflex

Answer 61

A response that is rapid and involuntary (unconscious)

Question 62

Describe the role of receptors in the response of animals to stimuli

Answer 62

Detect stimuli and transform them into electrical nerve impulses

Question 63

Describe the role of sensory neurons in the response of animals to stimuli

Answer 63

Relay the nerve impulse to the central nervous system (via the dorsal root of the spinal cord)

Question 64

Describe the role of relay neurons in the response of animals to stimuli

Answer 64

Transmit nerve impulses within the CNS

Question 65

Describe the role of motor neurons in the response of animals to stimuli

Answer 65

Receive nerve impulses from the CNS (via the ventral root) and relays the signal to an effector

Question 66

Describe the role of effectors in the response of animals to stimuli

Answer 66

Produce a response to the stimulus (can be muscles or glands)

Question 67

Describe the role of synapses in the response of animals to stimuli

Answer 67

The junctions between two nerve cells and transmission of a signal across these junctions require chemical neurotransmitters

Question 68

Explain how hedgehog behaviour has been affected by natural selection

Answer 68

• Hedgehogs exhibit different self-defensive responses to danger across different populations: curing into a ball to expose spines which create a shield for skin body and limbs, or running away • In areas where there are vehicles and roads, hedgehogs that run away when faced with danger (oncoming vehicles) will be favoured over ones which curl into a ball, as the spines will not protect against oncoming vehicles • Thus hedgehogs which run away are selected for by the environment

Question 69

List the four kinds of human sensory receptors and their functions

Answer 69

Mechanoreceptors - changes in pressure and textureChemoreceptors - changes in taste and smellPhotoreceptors - changes in lightThermoreceptors - changes in temperature

Question 70

State two similarities between cone and rod cells

Answer 70

• Both types of cell are photoreceptors • Both types of cell are found in the retina

Question 71

Distinguish between cone and rod cells with respect to their optimal light conditions

Answer 71

Rod cells are better in dim light, while cone cells are better in bright light

Question 72

Distinguish between cone and rod cells with respect to the type of vision they provide

Answer 72

Rod cells provide black and white, while cone cells provide colour

Question 73

Distinguish between cone and rod cells with respect to their relative abundance

Answer 73

There are much more rod cells than cone cells

Question 74

Distinguish between cone and rod cells with respect to their location

Answer 74

Rod cells are found throughout the retina, while cone cells are concentrated around the fovea

Question 75

Explain the processing of visual stimuli

Answer 75

• Lens focuses light onto rod and cone cells in the retina • Visual stimuli are processed by the retina and visual cortex in the brain • Bipolar cells in the retina combine impulses from groups of rod or cone cells and pass them on to ganglion cells • Receptive field is region of retina which communicates with one ganglion • Low ratio of cone/ganglion cells in the fovea gives high acuity (small visual fields) • There are two types of ganglion cells • One type of ganglia are stimulated by light hitting the centre of the receptive field and inhibited by light hitting the edge (and vice-versa) • Edge enhancement occurs when light/dark edges fall in the receptive field • Both the left and right visual cortex process images from both eyes • The optic nerves carries impulses from the retina to the visual cortex • Stimulus from the right visual field of both eyes is processed in the right visual cortex (and vice-versa) • This crossing over of nerves is called contralateral processing, and is facilitated by the optic chiasm

Question 76

Explain how sound is perceived by the ear

Answer 76

• Sound waves are collected by the pinna • Ear drum vibrated by air pressure changes (due to sound waves) • Middle ear bones stimulated by ear drum, enhancing sound by 20x • Oval window transmits vibrations from middle ear bones to cochlea • Tiny hairs in cochlea act as receptors for individual wavelengths of sound • Action potential generated in the cochlea • Auditory nerve transmits action potential to brain • Round windows of cochlea dissipate sound

Question 77

Describe innate behaviour

Answer 77

• Develop independently of the environmental context • Controlled by genes and inherited from parents • Uniform throughout population • Product of natural selection • e.g. suckling instinct in newborns, hunting instinct in some dogs

Question 78

Describe learned behaviour

Answer 78

• Develops as a result of experience • Modified by trial and error • Variation within population • Capacity to learn may be innate (language in humans, learning period) • e.g. dolphin learning to perform, learning to drive a car, domestication of animals

Question 79

Define taxis

Answer 79

An innate directional response to a (directional) stimulus

Question 80

Define kinesis

Answer 80

An innate non-directional response to a stimulus

Question 81

Discuss how the process of learning can improve the chances of survival

Answer 81

Learning involves acquiring information from past experiences to adapt to new situations. Organisms capable of learning can modify their behaviours in response to environmental change in order to survive • Animals learn how to avoid dangerous situations and predators • Birds learn that scarecrows pose no actual threat, and so eat crops • Animals can learn who their mother is and stay close to avoid predators • Animals learn how to hunt and obtain food

Question 82

Outline Pavlov’s experiment

Answer 82

• Dogs normally salivate (unconditioned response) in anticipation of being fed (unconditioned stimulus) • Pavlov sounded a bell (neutral stimulus) prior to feeding a dog • After many repetitions, the dog came to associate the bell with food and began to salivate when the bell was rung (conditioned response)

Question 83

Outline the role of inheritance and learning in the development of birdsong in young birds

Answer 83

• Birdsong has both inherited and learned components • Each species has a species-specific crude template which is genetically inherited • Within a species, birds have varied song, as they can learn to improve the song they have inherited • After hatching there is a ‘sensitive period’ lasting about 100 days during which birds listen to adult song and modify their template • If a bird does not hear song within this period, it will not modify its template. • The second phase is a motor phase in which the young bird practices singing the song it has learnt

Question 84

Explain how psychoactive drugs affect the brain and personality

Answer 84

• Psychoactive drugs may either increase postsynaptic transmission (stimulants) or decrease postsynaptic transmissions (depressants) • Stimulants produce psychomotor arousal and increased alertness, whereas depressants slow down brain activity and relax muscles • Both act primarily on the CNS and can cause a chemical dependency, leading to substance abuse and addictions

Question 85

List three excitatory psychoactive drugs

Answer 85

Cocaine, Amphetamines, Nicotine

Question 86

List three inhibitory psychoactive drugs

Answer 86

Benzodiazepines (BZD), Alcohol, THC

Question 87

Explain the effects of THC in terms of its effect on synapses in the brain

Answer 87

• Before THC enters the system, neurotransmitters are released into the synapse which inhibit the release of dopamine • THC mimics the neurotransmitter anandamide by binding to cannaboid receptors, preventing the release of this inhibitory neurotransmitter • This allows dopamine to be released into the synapse

Question 88

Explain the effects of Cocaine in terms of its effect on synapses in the brain

Answer 88

• Dopamine transporters remove dopamine from the synaptic clef after they have done their job • Cocaine blocks, these transporters, leaving dopamine trapped in the synaptic clef • As a result, dopamine binds repeatedly to the receptors, overstimulating the neuron

Question 89

Discuss the causes of addiction, including genetic predisposition, social factors and dopamine secretion

Answer 89

Genetic • Possible genetic predisposition to additionSocial • Alcohol problems among family members • Poor school performance • Stress • Having friends who drinkDopamine and addition • Dopamine is a chemical in the brain that is associated with pleasure and reward • Substances with addictive potential stimulate the release of dopamine • Substance use causes a flood of dopamine, which alters the chemistry of the brain

Question 90

Outline the function of the medulla oblongata

Answer 90

Controls automatic and homeostatic activities, such as swallowing, digestion and vomiting, and breathing and heart rate

Question 91

Outline the function of the cerebellum

Answer 91

Coordinates unconscious functions, such as movement and balance

Question 92

Outline the function of the hypothalamus

Answer 92

Maintains homeostasis via coordination of the nervous and endocrine systems, produces hormones secreted by posterior pituitary

Question 93

Outline the function of the pituitary gland

Answer 93

Produces and secretes hormones regulating many body functions

Question 94

Outline the function of the cerebral hemispheres

Answer 94

Act as the integration centre for highly complex functions, such as learning, memory and emotion

Question 95

Explain how animal experiments can be used in the identification of the brain part involved in specific functions

Answer 95

• One method of investigating the function of specific brain regions is to either stimulate the region with electrodes or remove the region (lobotomy) and assess the physical effect • Because such procedures are highly invasive and potentially damaging, animal models are frequently used • Such studies may be limited by the fact that animal brains may be dissimilar to human brains, so valid comparisons can be hard to make • The best comparisons are made with primates, however ethical considerations are of greater concern with these models • Animal experimentation using rats and mice have been used to understand and develop drug treatments for brain diseases such as MS

Question 96

Explain how lesions can be used in the identification of the brain part involved in specific functions

Answer 96

• Lesions are abnormal areas in brain tissue (either from accidents or congenital) which can indicate the effect of the loss of an area • Such studies may be limited by the fact that many functions involve multiple brain areas, making complex effects difficult to interpret • The brain also has the ability to re-learn skills by re-routing the function through another part of the brain (plasticity) • Split brain patients have been used to identify the functional roles of the left and right hemispheres • Individuals with aphasia (impairment to use or understand language) often have damage to specific regions of the left hemisphere

Question 97

Explain how fMRI scanning can be used in the identification of the brain part involved in specific functions

Answer 97

• fMRI records changes in blood flow and can indicate active regions of the brain via an increase in blood flow • Oxygenated haemoglobin (oxyhaemoglobin) responds differently to a magnetic field than deoxygenated haemoglobin • These differences in oxygenation (reflecting level of brain activity) can be represented visually by different colours • When a subject is given a stimulus designed to stimulate specific brain activity, fMRI can be used to localise regions involved • Temporal activities can also be recorded to allow identification of sequential collaboration between brain parts • While this procedure is non-invasive and can be performed on healthy subjects, not all brain activity is detected by fMRI • fMRI studies have been used to diagnose ADHD and dyslexia, in addition to being used to monitor recovery from strokes

Question 98

Explain sympathetic control of the heart rate, movement of the iris and flow of blood to the gut

Answer 98

• Involved in processes that prepare the body for action (‘fight or flight’ responses) • The sympathetic nervous system releases noradrenaline (adrenergic) via sympathetic nerves • Heart rate will increase to improve blood flow (via release of adrenaline) • Pupils will dilate to improve vision (via contraction of radial muscles) • Blood flow to gut will decrease (due to vasoconstriction of blood vessels by smooth muscles)

Question 99

Explain parasympathetic control of the heart rate, movement of the iris and flow of blood to the gut

Answer 99

• Involved in processes that occur when the body is relaxed (‘rest and digest’ or ‘feed and breed’ responses) • The parasympathetic nervous system releases acetylcholine (cholinergic) via parasympathetic nerves • Heart rate will decrease to reduce blood flow (via stimulation by vagus nerve) • Pupils will constrict to restrict light and potential retinal damage (via contraction of circular muscles) • Blood flow to gut will increase to facilitate digestion (due to vasodilation of blood vessels by smooth muscles)

Question 100

Explain the pupil reflex

Answer 100

• The pupil reflex is a cranial reflex originating at the brainstem and under the control of the autonomic nervous system • Bright light can overstimulate photoreceptors and potentially damage the retina • In changing levels of light, the iris will automatically resize to regulate the amount of light that reaches the retinaIn dim light conditions: • Relay neurons stimulate thesympatheticnervous system, causingradial musclesto contract and the pupil todilateIn bright light conditions: • Relay neurons stimulate theparasympatheticnervous system, causingcircular musclesto contract and the pupil toconstrict

Question 101

Discuss the concept of brain death

Answer 101

• Whole brain death is the loss of measureable activity in the brain stem and cerebrum • Failure of the pupil to response to light indicates brain stem death • Without brain stem function, life cannot continue • Cerebrum involves higher order brain function • Non-functioning cerebrum with functioning brain stem is vegetative state • Some would argue that this is the death of the person, although brain stem function alone may be able to maintain homeostasis

Question 102

Outline how pain is perceived and how endorphins can act as painkillers

Answer 102

• Pain is perceived when impulses pass from pain receptors to sensory areas of the cerebral cortex • Endorphins are released by the pituitary gland during stress, injury or exercise, and act as painkillers by blocking pain perception • They do this by blocking the release of neurotransmitters at the synapses involved in pain signal transmission

Question 103

Describe the social organisation of honey bee colonies

Answer 103

• Bees live and interact together in a community divided into caste system consisting of a queen, drones and workers • Queens are fertile females who lay eggs, and produces pheromones • Drones are fertile males who can mate with the queen • Workers are infertile females who gather food

Question 104

Outline how natural selection may act at the level of the colony in the case of social organisms

Answer 104

• Natural selection is a mechanism of evolution that acts on the gene pool of a given population • Beneficial alleles become more frequent in a population as individuals with those alleles are more likely to achieve reproductive success • Many organisms form social clusters as their survival prospects are improved by cooperative group organisation • Because colonies are usually comprised of genetically related individuals, behaviours or traits that benefit the colony will improve the reproductive success of the group, even if it does not directly benefit the individual • Such characteristics are more likely to be passed on to subsequent generations and hence become more frequent in the gene pool

Question 105

Discuss the evolution of altruistic behaviour using two non-human examples

Answer 105

• Altruistic behaviour is behaviour that benefits other individuals and may be harmful to the self • It is common in animals with complex social structures • It increases survival of the colony or species as a whole, but not of individuals • Natural selection works at the level of the population, and normally works against behaviour that reduces the chance of survival and reproduction • In a naked mole rat colony, non-breeding animals help to raise offspring • Sometimes, individuals care for related individuals who are not their own offspring e.g. vampire bats share regurgitated blood with other unrelated colony members who haven’t fed • It is difficult to explain altruism towards unrelated individuals

Question 106

Outline how foraging behaviour optimises food intake, using bluegill fish foraging for Daphnia

Answer 106

• Foraging is the act of searching for, and finding, food • As the availability and abundance of food sources will vary, animals must adapt their feeding behaviours to account for these changes • The bluegill fish feeds on the aquatic crustaceanDaphniaand has been shown to change its foraging behaviour if prey availability is altered • If a feeding population is at high density, bluegill fish will predominantly eat largerDaphnia(high energy payoff at low search cost) • If a feeding population is at low density, bluegill fish will eat a range ofDaphniasizes (high search cost outweighs benefit of high energy payoff)) • The bluegill fish has also been shown to demonstrate different foraging behaviour depending on the availability of types of prey

Question 107

Explain how mate selection can lead to exaggerated traits

Answer 107

• The success of an organism is not only measured by the number of offspring left behind, but also by reproductive fitness of the offspring • Features that improve a male’s chances of successfully competing with other males for the best mate will become more prevalent within the gene pool • As exaggerated traits are more likely to attract female attention and consequently promote successful reproduction, these traits will be selected for through sexual selection, even though they may increase predator attention and diminish the survival prospects of the individual • E.g. plumage feathers of the peacock

Question 108

State that animals show rhythmical variations in activity

Answer 108

Animals often show behaviours that follow rhythmical variation, including: • Diurnal (daily) cycles • Lunar cycles (monthly) • Seasonal changes

Question 109

Outline the behavour of moonrats as an exmple illustrating the adaptive value of rhythmical behaviour patterns

Answer 109

Moonrats are nocturnal. Their excellent sense of smell helps them to forage at night when much or their prey is active (insects and other invertebrates). They are also less vulnerable to predation at night, and they rest in holes among tree toots or in hollow logs during, where they are unlikely to be discovered.

Question 110

Outline the behavour of red deer as an exmple illustrating the adaptive value of rhythmical behaviour patterns

Answer 110

Reproduction follows an annual cycle in red deer. Males and females are only sexually active during autumn. Males fight to establish dominance over groups of females with whom they mate. The advantage is that if the females start gestation in the autumn, the offspring are born in spring, when most food is available for feeding the offspring.