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Animal Behaviour

Explain the advantages to organisms of innate behaviour

○ Doesn’t need to be learnt

○ Immediate survival for young, inexperienced animal in a dangerous place

○ Useful for invertebrates with short lifespans who don’t have time to learn

○ Requires few neurones

○ Likely to be appropriate for animal’s habitat, as alleles controlling it will have been subject to natural selection

Describe escape reflexes, taxes and kineses as examples of genetically determined innate behaviours

Escape reflex

Particular stimulus brings automatic response, the function of which is to avoid predators eg. earthworms withdrawing underground in response to vibrations

Taxis

Directional movement in response to external stimulus eg. maggots moving away from light to be less visible to predators

Kinesis

Movement in response to external stimulus. Rate of movement related to intensity but not direction of stimulus eg/ woodlice in dry/bright conditions rapidly and randomly move around the body until they’re in more favourable conditions

Explain the meaning of the term learnt behaviour

Animal responses that change or adapt with experience

Describe habituation, imprinting, classical and operant conditioning, latent and insight learning as examples of learned behaviours

Habituation

Animals learn to ignore certain stimuli because repeated exposure results in neither punishment nor reward. Avoids wasting energy in escaping non-dangerous stimuli

Imprinting

Young organisms associate with another organism, usually the parent. They then only follow and learn from them ~ helps young learn skills from parents

Classical Conditioning

Form of adaptive learning in which an innate response is modified. The animal learns to respond to a different stimulus ~ Pavlov’s dogs

Operant Conditioning

Form of adaptive learning whereby an animal learns to carry out and action for a reward/to avoid a punishment

Latent Learning

Behaviour not directed towards particular outcome ~ animals exploring surroundings which may be useful in escaping a danger at another point in time

Insight Learning

Form of learning where animal integrates memories of two or more earlier actions to produce a new response or gain reward. Organism has ability to think and reason to solve problems or deal with situations that don’t resemble  simple, fixed reflex responses or need for repeat trial and error

Describe, using one example, the advantages of social behaviour in primates

In Gorillas:

○ Females give birth to one or few young. Maternal care and group protection enhances survival of young. At 1, they only move five metres from mother

○ Young learn through observation and play with other group members. Learned behaviour vital to survival of primates. At 2, they play together and imitate adult behaviour

○ 3-6 play with older male to learn new skills

○ Relatively large brain slows maturity ~ security of group enhances survival and learning of young

○ Knowledge, protection and food shared with group

○ Work together to detect and deter predators/threats

Discuss how the links between a range of human behaviours and the dopamine receptor DRD4 may contribute to the understanding of human behaviour

There are a range of dopamine receptors in the brain. Dopamine levels depend on their efficiency. Linked to schizophrenia, ADHD and Parkinson’s disease, DRD4 is the most variable receptor

Animal Responses

Discuss why animals need to respond to their environment

Animals need to respond to their environment to survive. This is done using nerves and hormones to control responses ranging from muscle actions to run away from a predator, to fine control of balance, posture and temperature regulation

Outline the organisation of the nervous system in terms of central and periphery systems in humans

The nervous system branches into the central nervous system and the peripheral nervous system. The peripheral nervous system branches into the somatic nervous system and autonomic nervous system. The autonomic nervous system branches into the sympathetic nervous system and parasympathetic nervous system

Outline the organisation and roles of the autonomic nervous system

Sympathetic nervous system:

○ Most active in times of stress

○ Neurones of pathway linked at ganglion fuse outside spinal chord

○ Pre-ganglion neurones very short

○ Post-ganglion neurones secrete noradrenaline at synapse between neurone and effector

○ Effects of action include ~ increased heart rate, pupil dilation, increased ventilation rate, orgasm

Parasympathetic nervous system

○ Most active during sleep and relaxation

○ Neurones of a pathway linked at a ganglion within target tissue ~ pre-ganglian neurones vary in length

○ Post-ganglion neurones secrete acetylcholine as a neurotransmitter at synapses between neurone and effector

○ Effects of action may include ~ decreased heart rate, pupil dilation, decreased ventilation rate, sexual arousal

Describe, with the aid of diagrams, the gross structure of the human brain, and outline the functions of the cerebrum, cerebellum, medulla oblongata and hypothalamus

Cerebrum ~ control of all higher order processes such as memory, language, emotions, thinking and planning

Cerebellum ~ control and coordination of movement/posture

Medulla oblongata ~ control of breathing, heart rate and smooth muscle of the gut

Hypothalamus ~ control of autonomic nervous system and some endocrine glands

Describe the role of the brain and nervous system in the coordination of muscular movement

Conscious decision to voluntarily move is initiated in cerebellum. Neurones from cerebellum carry impulses to motor areas so motor output to effectors can be adjusted accordingly

Describe how coordinated movement required action of skeletal muscles about joints, with reference to the elbow joint

Coordinated and appropriate movement requires controlled action of skeletal muscles about joints. Can be seen in the movement of the elbow

1. Impulses arrive at neuromuscular junction. This causes vesicles to fuse with the pre-synaptic membrane and to release acetylcholine into the cleft

2. Acetylcholine binds to receptors on sarcolemma, causing depolarisation

3. Depolarisation wave passes down T system

4. T system depolarisation releases Ca2+ from stores in sarcoplasmic reticulum

5. Ca2+ binds to proteins in muscle, leading to contraction

6. Acetylcholinesterase in the gap rapidly breaks acetylcholine down so the contraction only occurs when impulses continuously arrive

Explain, with the aid of diagrams and photographs, the sliding filament model of muscle contraction

1. Myosin heads bind to surrounding actin filaments, forming a cross-bridge

2. Heads bend, causing actin to be pulled along and overlap with myosin more. This is the power stroke and ADP and Pi are released

3. Cross-bridges broken as new ATP binds to the myosin heads

4. Head groups move backwards as ATP is hydrolysed to make ADP and Pi

For the myosin head to bind with the actin and form a cross-bridge, Ca2+ must be present. These ions bind to troponin which causes tropoyosin to move away from the myosin binding sites. This exposes them so cross-bridges can form

Outline the role of ATP in muscular contraction, and how the supply of ATP is maintained in muscles

Role

○ Energy from ATP required to break cross-bridge connections so they can reset the myosin head forwards

Maintenance

○ Aerobic respiration in mitochondria

○ Anaerobic respiration in sarcoplasm

○ Transfer Pi to ADP in sarcoplasm

Compare and contrast the action of synapses and neuromuscular junctions

Outline the structural and functional differences between voluntary, involuntary and cardiac muscle

State that responses...

Responses to environmental stimuli in mammals are coordinated by nervous and endocrine systems

Explain how, in mammals, the ‘fight or flight’ response to environmental stimuli is coordinated by the nervous and endocrine systems

Nervous

1. Sensory neurones in SNS carry impulses from receptors to the sensory area of the cerebrum, giving information about danger in the environment

2. SyNS activated

3. Action potentials sent down accelerator nerve to SAN of heart, increasing heart rate and stroke volume

4. Adrenal glands stimulated to secrete adrenaline

Endocrine

1. Caused by adrenaline

2. Smooth muscles surrounding bronchioles relax, increasing airflow to lungs

3. Blood flow to skin and gut reduced

4. Glycogen broken down to glucose in muscle cells

5. Mental awareness increased

Plant Responses

Explain why plants need to respond to their environment in terms of the need to avoid predation and abiotic stress

Plants respond to external stimuli (as well as biotic and abiotic components of the environment) to help the plants avoid stress, be eaten, and survive long enough to reproduce. These responses are coordinated by hormones

Define the term tropism

A directional growth response in which the direction of the response is determined by the direction of the external stimulus

Explain how plant responses to environmental changes are coordinated by hormones, with reference to responses to changes in light direction

Presence of auxin promotes active transport of H+ through ATP synthase enzyme in cell wall. Decreases pH, allows optimum conditions for wall loosening enzymes to work. Enzymes break bonds within cellulose so walls become less rigid and expand as cells take in water

The shoot bends towards the light source because auxin is transported to cells in the shade, causing those to take up more water and elongate

Cells elongate more on the shaded side than where the light is, so the shoot bends towards the light source

Evaluate the experimental evidence for the role of auxins in the control of apical dominance and gibberellin in the control of stem elongation

Auxins

Apical dominance is when the growing apical bud at the top of the shoot inhibits the growth of lateral buds further down the shoot. Auxins produced in the tip of the main shoot inhibit the growth of side shoots. When the tip of the shoot is removed (or axuin transport inhibitor is applied below the apex of the shoot), side shoots grow. This shows that auxin is produced at the apex of the main shoot and is transported to lateral buds to prevent growth. When auxin is found in low concentrations at the side shoots, their growth isn’t inhibited so they can then grow. This is also shown when, as plants grow taller, lateral buds at the bottom start to grow larger as they’re further from the main shoot so there’s a lower concentration of auxin present

Gibberellins

Genetically dwarf plants are treated with Gibberellic acid so stems considerably elongate

Outline the role of hormones in leaf loss in deciduous plants

○ Cytokinins prevent senescence

○ Make leaves act as a sink for phloem ~ good nutrient supply

○ Cytokinin production drops, nutrient supply decreases

○ Senescence decreases auxin production

○ Auxin decrease causes an ethene increase

○ Cells in abscission zone more sensitive to ethene

○ Cellulase production increases

○ Cell walls in abscission zone digested

○ Petiole separated from cell

Describe how plant hormones are used commercially

Used to maximise profit and minimise labour

○ Ethene stimulates ripening of fruits ~ stimulates enzymes which break down cell walls and chlorophyll, and convert starch into sugar

○ Auxins and gibberellins make unpollinated fruit developed ~ used to produce seedless fruits

○ Auxins ~ sprayed with low concentrations during early development prevents fruit drop. Being sprayed by high concentrations at later stages of development encourages fruit drop. Used to decrease labour as all fruits drop at the same time

○ Auxins used as selective weed killers ~ make apical bud of weeds grow too fast, so weeds can’t take up enough nutrients and die

Populations and Sustainability

Explain the significance of limiting factors in determining the final size of a population

A habitat cannot support a population larger than its carrying capacity due to limiting factors. These include:

○ Resources ~ food, water, light, oxygen, nesting sites, shelter

○ Effects of other species ~ predators, parasites, intensity of competition for resources

Explain the meaning of the term carrying capacity

The maximum population that can be maintained over a period of time in a particular habitat

Describe the predator-prey relationships and their possible effects on the population size of both the predator and the prey

○ Predator population  ↑ = more prey eaten

○ Prey  ↓ = less food for predators

○ Fewer predators can survive =predators  ↓

○ Fewer predators = fewer prey eaten = prey ↑ 

○ More food for predators = predator population  ↑

Explain, with examples, the terms interspecific and intraspecific competition

Interspecific competition

Competition between individuals of different species can affect both population size and the distribution of a species in an ecosystem as no two species can occupy the same niche

eg. Red vs grey squirrel ~ red squirrel out-competes grey squirrels in conifer forests but grey squirrels out-compete red squirrels in forests with less than 75% conifers

Intraspecific competition

Competition between individuals of the same species. If a food supply becomes a limiting factor, individuals best adapted to obtaining food will survive and reproduce, whereas those less well adapted will die and won’t be able to pass on their genes

Distinguish between the terms conservation and preservation

Conservation ~ the active management of a habitat in order to maintain or increase biodiversity in an area/habitat

Preservation ~ the protection of a species by leaving their habitat untouched

Explain how the management of an ecosystem can provide resources in a sustainable way, with reference to timber production in a temperate climate

Small-scale

○ Coppicing ~ trunk cut close to ground at an angle so water runs off and new shoots can grow and mature

○ Pollarding ~ coppicing but higher up so deer don’t eat new shoots

○ Rotational coppicing ~ done in sections so better for biodiversity

Large-scale

○ Clear felling ~ cutting down large areas of forest ~ habitats destroyed, soil minerals reduced and soil susceptible to erosion. Woodland left to mature for a century. Must be replaced by re-planting. Biodiversity must be maintained and local people must benefit

Explain that conservation is a dynamic process involving management and reclamation

Maintaining biodiversity in dynamic ecosystems required careful management to maintain a stable community, or even reclaim an ecosystem by reversing the effects of human activity. Management strategies include:

○ Raising the carrying capacity ~ adding food

○ Moving individuals to enlarge populations/encourage natural dispersal of individuals between fragmented habitats by providing appropriate dispersal corridors

○ Restrict dispersal by fencing

○ Controlling predators and poaches

○ Vaccinating individuals against disease

○ Preserving habitats by preventing pollution or disruption

○ Intervening to restrict process of succession

Discuss the economic, social and ethical reasons for conservation of biological resources

Economic

○ Many species provide a valuable food source

○ Genetic diversity in wild strains of domesticated species may be needed in future for certain characteristics

○ Natural environments are valuable sources of potentially beneficial resources eg. medicine

○ Natural predation of pests can act as biological control agents

○ Wild insect species pollinate crops

○ Other organisms maintain water quality, protect soil and break down waste products

○ Reduced biodiversity may cause reduced climatic stability

Social

○ Ecotourism and recreation relies on biodiversity

Ethical

○ Every species has a value in its own right

○ Every living thing has a right to survive

Outline, with examples, the effects of human activities on the animal and plant populations in the Galapagos Islands

○ 1980 ~ population 5 000, 4 000 annual tourists

○ 2005 ~ population 28 000, 100 000 annual tourists

○ Dramatic population increase placed huge demand on water, energy and sanitation services

○ More pollution and waste produced

○ Oil demand increased

○ 2001 oil spill had adverse on marine and coastal ecosystems

○ Increased pollution, building and conversion of land for agriculture has caused destruction and fragmentation of habitats

○ Species harvested faster than they can replenish ~ giant tortoises taken on long voyages for food; fishing for exotic species of fish has decimated population; depletion of sea cucumbers had drastic effect on underwater ecology; international shark fin market kills 150 000 sharks a year

Ecosystems

Define the term ecosystems

All living organisms and non-living components in a specific habitat, and their interactions

State that ecosystems...

Ecosystems are dynamic systems

Define the terms biotic factor and abiotic factor, using named examples

Biotic factor ~ how living organisms affect each other eg. good supply, predation, disease

Abiotic factor ~ effect of non-living components of an ecosystem eg. pH, temperature, soil type

Define the terms producer, consumer, decomposer and trophic level

Producer ~ an organism that converts simple inorganic molecules into complex organic compounds

Consumer ~ an organism that gains energy from complex organic matter

Decomposer ~ an organism that feeds on waste from other organisms, or dead organisms

Trophic level ~ each level in a food chain/web

Describe how energy is transferred through ecosystems

Transferred by organisms consuming each other. Shown in food web, with arrows representing the flow of energy between organisms

Outline how energy transfers between trophic levels can be measured

Energy content of samples of organisms from each trophic level is measured:

○ Each sample dried in an oven

○ Samples weighed

○ Samples burned in bomb calorimeter

○ Energy produced is passed to known mass of water and temperature rise of water is calculated

○ Energy released per gram is calculated

Discuss the efficiency of energy transfers between trophic levels

Energy is lost between trophic levels because animals:

○ Don’t eat all available food

○ Can’t digest all the food they eat

○ Use energy in respiration

○ Lose heat energy to surroundings

○ Lose energy in urine and faeces

Explain how human activities can manipulate the flow of energy through ecosystems

○ Replacing natural vegetation and fauna with crops and livestock

○ Deflecting natural succession to maintain grassland

○ Increase productivity of producers through:

→ Soil improvement

→ Irrigation

→ Fertilisers

→ Removal of competing weeds/damaging pathogens and pests

○ Increasing productivity of producers through selective breeding/GM

○ Sheltering organisms from damaging environmental factors

Describe one example of primary succession resulting in a climax community

Sand Dunes

1. Pioneer plants like sea rocket colonise the sand just above high water mark. Can tolerate salt water spray, lack of fresh water and unstable sand

2. Wind-blown sand builds up around the base of these plants, forming a small sand dune. As plants die and decay, nutrients accumulate

3. As dune grows, plants like sea couch grass colonise it. They have underground stems to help stabilise sand

4. More stability and nutrients allows marram grass to grow. These trap windblown sand. As this accumulates, the shoots grow taller to stay above dune, trapping more sand

5. Sand and nutrients build up, allowing other plants to colonise sand. Many are bean family. These have nodules in roots containing bacteria which convert nitrogen to nitrates

6. More nitrates means more plants colonise the dunes, colonising it further

Rocks:

1. Algae and lichens begin to live on bare rock

2. Erosion of rock and build up of dead and rotting organisms produces soil for larger plants like mosses and ferns

3. Larger plants succeed smaller plants until climax community is reached

Describe how the distribution and abundance of organisms can be measured, using line transects, belt transects, quadrats and point quadrats

Line transects ~ on a line across a habitat. Record each species touching the line and their position

Belt transects ~ quadrats placed at regular intervals along a line transect

Quadrates ~ square frame placed at random in a habitat. Each species present is recorded, along with their abundance

Point quadrats ~ frames with long pins. Lowered vertically at random. Each species touching a pin (and the number of times it’s touched) is recorded

Describe the role of decomposers in the decomposition of organic material

Feed on waste from other organisms. Recycle materials like carbon and nitrogen. If they didn’t break down dead organisms, energy and valuable nutrients would remain in the dead organism

Describe how microorganisms recycle nitrogen within ecosystems

Nitrogen to ammonium ions:

Nitrogen fixed by bacteria like Rhizobium that live in root nodules. Have a mutualistic relationship with the plant ~ they fix nitrogen for plant and plant provides carbon compounds (glucose). There are proteins which absorb oxygen, keeping conditions anaerobic so nitrogen reductase can reduce nitrogen gas to ammonium ions

Ammonium ions to nitrites:

Ammonium ions released by bacteria in putrefaction of proteins can be found in dead or waste organic matter. Nitrosomonas bacteria obtain energy by oxidising ammonium ions to nitrites under aerobic conditions

Nitrites to nitrates

Nitrobacter obtain energy by oxidising nitrites to nitrates under aerobic conditions

Nitrates

Genomes and Gene Technologies

Outline the steps involved in sequencing the genome of an organism

Genomes are mapped. These are used as landmarks. Samples of the entire genome are taken and sheared into smaller sections ~ 100 000 base pairs. The smaller sections are placed into separate bacterial artificial chromosomes (BACs). These are put into E. Coli cells. These reproduce to form a clone library. The cells containing BACs are taken and cultured. DNA is then extracted from these and restriction enzymes are used to cut the DNA into even smaller fragments. Different enzymes create different fragment types. The fragments are then separated by electrophoresis and sequenced by an automated process. Computer programmes compare overlapping regions from cuts made by enzymes to reassemble the whole BAC sequence

Outline how gene sequencing allows for genome-wide comparisons between individuals and between species

Identification of genes for proteins found in all, or many, living organisms gives clues to the importance of the genes for life. The comparison of interspecific DNA shows evolutionary relationships and can model the effects of changing DNA. Similar genomes from pathogenic and non-pathogenic organisms can be used to identify the genes or base pair sequences that are more important in causing disease. This means that more effective drugs can be developed. The DNA of individuals can be analysed to reveal the presence of alleles associated with particular diseases

Define the term recombinant DNA

A section of DNA, often in the form of a plasmid, which is formed by joining DNA sections from two different sources

Explain that genetic engineering involves the extraction of genes from one organism such as that the receiving organism produces the gene product

1. The required gene is obtained

2. Copy of gene is placed in a vector using restriction enzymes

3. Vector carries the gene to the recipient cell

4. The recipient cell expresses the gene through protein synthesis

Describe how sections of DNA containing a desired gene can be extracted from a donor organism using restriction enzymes

1. DNA probe is used to locate the gene

2. Gene is cut using the restriction enzyme

3. Restriction enzymes only cut where a specific base sequence occurs

4. Enzyme catalyses hydrolysis reaction breaking sugar-phosphate backbone of DNA at different points ~ creates sticky ends

Outline how DNA fragments can be separated by size using electrophoresis

1. DNA samples are treated with restriction enzymes so they’re cut into fragments

2. DNA samples placed into wells at the negative electrode end of the gel

3. Gel immersed in the tank of buffer solution and an electric current is passed through

4. DNA is negatively charged because of phosphate groups in DNA backbone are attracted to the positive electrode

5. Shorter DNA fragments travel faster so move further in fixed time

6. Position of fragments shown by dye that stains DNA molecules

Describe how DNA probes can be used to identify fragments containing specific sequences

○ DNA probe is a short, single-stranded section of DNA which is complementary to a specific base sequence

○ Labelled

→ Radioactive marker

→ Fluorescent marker

○ Copies of probe added to sample of DNA fragments

○ Probes anneal to fragments where complementary base pairs are present

○ Check for annealed probes

→ Photographic film

→ UV light

Outline how the polymerase chain reaction (PCR) can be used to make multiple copies of DNA fragments

1. Get double-stranded DNA sample

2. Heat to 95oC so strands separate

3. Add primers and reduce temperature to 55oC so primers can anneal

4. Raise temperature to 72oC so DNA polymerase can bind and extend primers using free nucleotides

Explain how isolated DNA fragments can be placed in plasmids, with reference to the role of ligase

Plasmids and fragments are both cut with the same restriction enzymes. This means they have complementary sticky ends. Base pairs anneal and DNA ligase joins together sugar-phosphate backbone to form recombinant DNA

State other vectors into which fragments of DNA may be incorporated

Liposomes

Viral DNA

Hybrid vectors with properties of plasmids and bacteriophages

Explain how plasmids may be taken up by bacterial cells in order to produce a transgenic microorganism that can produce a desired gene product

Large quantities of plasmid mixed with bacterial cells. Calcium salts are added, the temperature reduced to freezing and then quickly raised to 40oC. Increases rate that plasmids are taken up

Describe the advantage to microorganisms of the capacity to take up plasmid DNA from the environment

Plasmids may contain:

○ Genes for antibiotic resistance, increasing survival chances

○ Genes which help bacteria to invade hosts

○ Genes which help bacteria to break down different nutrients/sugars

○ Genetic variation

Outline how genetic markers in plasmids can be used to identify the bacteria that have taken up a recombinant plasmid

Not all bacteria takes up the plasmid ~ some re-seal themselves

1. Plasmid used which carries genes which make any bacteria receiving them resistant to two antibiotics ~ resistant genes known as genetic markers

2. Plasmids cut by restriction enzyme in the middle of one of the resistant genes so that, if the required gene is present, it doesn’t work for antibiotics but the others do

3. DNA placed in plasmids and plasmids into bacterial cells

4. Bacteria grown on agar plate to produce colony

5. Some cells transferred to agar made with intact antibiotic so those that have taken it up will grow

6. Same with agar of second antibiotic

7. Those that have taken up non-recombinant plasmid will grow

8. Those that grow on first agar but not second have taken up recombinant plasmid

8. Required colonies identified and grown on a large scale

Outline the process involved in the genetic engineering of bacteria to produce human insulin

1. mRNA from human insulin extracted from pancreatic cells

2. Reverse transcriptase uses mRNA as a template to make single-stranded cDNA ~ made double stranded by DNA polymerase

3. Nucleotides added to both ends of DNA to make sticky ends

4. Plasmids cut open with a restriction enzyme

5. Cut plasmids have complementary sticky ends

6. Plasmids and insulin gene mixed so sticky ends form base pairs

7. DNA ligase binds sugar-posphate backbone of plasmid and insulin gene

8. Plasmids mixed with bacteria in presence of Ca2+

9. Bacteria take up plasmids and multiply to form clones

10. Genetically engineered bacteria use protein synthesis to produce insulin

Outline the process involved in the genetic engineering of Golden Rice

Two genes from daffodils and one from bacteria Erwina urefovora inserted into plasmids and taken up by bacteria Agrobacterium tumefaciens. Introduced into rice embryos

Resulting rice plants produce seeds with beta-carotene are in the endosperm (which is yellow)

Body uses the beta-carotene to produce vitamin A

Outline how animals can be genetically engineered for xenotransplantation

Pigs are engineered to lack ezyme alpha-1,3-transferase. It’s a key trigger for rejection of organs in humans

Human nucleotidase grafted into pig cells in culture. Reduces number of immune cell activities in xenotransplant rejection

Explain the term gene therapy

Therapeutic technique where a functioning allele of a particular gene is placed in the cells of an individual who is lacking the functioning alleles. Used to treat recessive conditions

Explain the differences between somatic cell and germline cell gene therapy

Discuss the ethical concerns raised by the genetic manipulation of animals, plants and microorganisms

○ Religious objections

○ Objections to tampering with organism’s natural genotype

○ Fears of unforeseen effects of gene

○ Fears of consequences if it affects wild organisms