Biology Unit 2

BIOLOGY UNIT 2

7. Variation

7.1_Investigating Variation

·       When one species differs from another, this is called interspecific variation.

·       However, members of the same species also differ from each other, this is intraspecific variation.

SAMPLING

• Involves taking measurements of individuals selected from the population of organisms being investigated.
• Can we be sure the sample is representative?
• Sampling bias – Investigators may be making unrepresentative choices when sampling. E.g. may avoid areas in cow dung or stinging nettles.
• Chance – Individuals may, by pure chance, not be representative.

-Best way to eliminate sampling bias is to eliminate as much human involvement as possible.

-Random sampling – Divide area into grid with numbers > Use random number table to obtain coordinates. > Take samples from these coordinates.

-Cannot completely remove chance but can minimise its effect:

-Use a large sample size – more reliable data.

-Analysis of data collected – Statistical tests can be used to determine to what extent chance may have influenced results – allow us to determine whether variation is due to chance or another cause.

CAUSES OF VARIATION

·        Variation is the result of two main factors:

-         Genetic differences

-         Environmental influences

Genetic differences:

·        Mutations: Sudden changes to genes and chromosomes may, or may not, be passed to next generation.

·        Meiosis: Special form of nuclear division formes gametes. This mixes up genetic material before it’s passed to gametes, all of which are therefore different.

·        Fusion of gametes: In sexual reproduction, offspring inherit some chacteristics of each parent so are different from both. Which gametes fuse is random, adding to variety.

·        Variety in asexually reproducing organisms can only be increased through mutations.

Environmental influences:

·        Genes set limits, but it’s largely the environment that determines where, within the limits, an organism lies.

·        E.g. a buttercup may have genes to allow it to grow tall, but if there is low light in an area, it will not grow properly.

·        Variation is usually due to a mixture of genetic differences and environmental influences.

·        Difficult to distinguish between effects of many genetic and environmental influences so it is very difficult to draw conclusions about what causes variation in any particular case.

8. DNA and meiosis

8.1_Structure of DNA

NUCLEOTIDE STRUCTURE

Individual nucleotides have 3 components:

-Deoxyribose (sugar)

-Phosphate group

-An organic bas belonging to one of 2 groups

  *Single-ring bases – cytosine (C) and Thymine (T)

  *Double- ring bases – Guanine (G) and Adenine (A)

·        The deoxyribose sugar, phosphate group and organic base are combined (through a condensation reaction), to give a mononucleotide.

·        Two mononucleotides may cobine in a condensation reaction between the Deoxyribose sugar of one nucleotide and the phosphate group of another, to form a dinucleotide.

·        A long chain of these is a polynucleotide.

DNA structure

• In 1953, James Watson and Francis Crick worked out the structure of DNA, following on from the work of Rosalind Franklin on the x-ray diffraction patterns of DNA.
• DNA is made up of two strands of nucleotides (polynucleotides), each of which are very long and joined by hydrogen bonds between certain bases.
• Simplified, DNA is a ladder where phosphate and Deoxyribose form the uprights, while the organic base pairs make the rungs.

Pairing of bases

• Organic bases contain nitrogen.
• Double-ring structures (A & G) have longer molecules than Single-ring structures (C & T).
• Therefore, for the rungs of ladder to be same length, base pairs must always form from one double-ring and one single-ring structure.

-Adenine always pairs with Thymine by two hydrogen bonds.

-Guanine always pairs with Cytosine by two hydrogen bonds.

• Adenine is complementary to Thymine and Guanine is complementary to Cytosine.
• Quantities of Adenine and Thymine are always the same, as are the quantities of Guanine and Thymine, but the ratio of A & T and G & C varies between species.

The double helix

• The ladder arrangement of two polynucleotide chains is twisted to form a double helix.
• The phosphate and Deoxyribose form the backbone of the DNA molecule.
• For each complete turn of the helix, there are 10 base pairs.

The function of DNA

• DNA is the hereditary material responsible for passing genetic information between cells and generations.
• There are around 3.2 billion base pairs in the DNA of a typical mammalian cell.
• This means there is an almost infinite variety of sequences of bases along the length of a DNA molecule, which provides immense genetic diversity.

DNA molecule adapted to carry out functions in number of ways:

-Very stable and can pass between generations without change.

-Two separate strands are joined only with hydrogen bonds, allowing them to separate during DNA replication and protein synthesis.

-Extremely large molecule so carries immense amount of genetic information.

-Having the base pairs within the helix means that the genemtic information is somewhat protected from being corrupted by outside chemical and physical forces by the deoxribose-phosphate backbone.

• The function of DNA depends on the sequence of base pairs it possesses.

8.2_The triplet code

WHAT IS A GENE?

• Section of DNA that contains coded information for making polypeptides.
• Coded information in form of specific sequence of bases along DNA molecule that determines a polypeptide which is a sequence of amino acids.
• Polypeptides combine to make proteins so genes determine proteins of an organism.
• Enzymes control chemical reactions so are responsible for an organisms development and activities.
• Genes determine nature and development of all organisms.

THE TRIPLET CODE

·        Must be a minimum of 3 bases coding for each amino acid:

-Only 20 amino acids regularly occur in proteins

-Each amino acid must have own code of bases on DNA.

-Only 4 different bases are present in DNA.

-If each base coded for different A.acid, only 4 could be coded for.

-Using a pair of bases – 16 (4²) codes possible – still inadequate.

-3 bases produce 64 (4³)codes – more than enough for 2 A.Acids.

• Three bases = triplet code.
• 64 codes and only 2 amino acids = some amino acids have more than one code.
• In eukaryotes much of nuclear DNA doesn’t code for Amino acids,
• These sections are called introns and can occur within genes and as multiple repeats between genes.

INTRONS

8.3_DNA and chromosomes

Prokaryotic cells – e.g. bacteria – DNA molecules are smaller, form a circle and not associated with protein molecules. Do not have chromosomes.

Eukaryotic cells – DNA molecules are larger, form a line and occur in association with proteins to form chromosomes.

CHROMOSOME STRUCTURE

• Chromosomes only visible as distinct structures during cell division.
• Rest of the time – widely dispersed throughout nucleus.
• When visible – two threads joined at a single point. Each thread is a chromatid.
• DNA in chromosomes held in positions by proteins.
• Around 2m of DNA in every human cell is highly coiled and folded.

-Helix wound around proteins to fix in position.

-DNA- protein complex then coiled.

-The coil is looped and further coiled.

Coil packed into chromosome.

• Single DNA molecule has many genes along length.
• Each gene in a specific position.
• Same number of chromosomes for normal individuals of a species e.g. humans have 46, potato plant have 48 an dogs have 78.
• Almost all species have an even number of chromosomes in cells of adults because of homologous pairs.

HOMOLOGOUS CHROMOSOMES

• Reason for pairs – fusion of sperm & egg in sexual reproduction.
• One of each pair from mother(maternal), one from father(paternal).
• Total number of homologous pairs is the diploid number. (46 in humans).
• A homologous pair is always 2 chromosomes that determine same genetic characteristics – ‘determining the same characteristics’ is not being identical – Homologous pair may posses info on eye colour and blood group, one chromosome blue and A, one green and B (alleles).
• During meiosis, the halving of the number of chromosomes is done in such a way that ensures each daughter cell gets a chromosome from each homologous pair – each cell receives one set of information for each characteristic.
• When these haploid cells combine, diploid state with homologous chromosomes is restored.

Geographical investigations - Rebranding places

Geographical investigations

Rebranding places

Time to Rebrand

Rebranding

• Regeneration, rebranding and reimaging of places has become increasingly prominent on government agendas in recent years, especially in areas that have experienced significant economic or industrial decline.
• Process of renewing places is expensive and often involves physical redevelopment of outdated facilities.
• Rebranding and reimaging mean more than just improving the cosmetics of a place, also concerned with reputation, spirit and identity.
• In rebranding there are 4 focuses:
• Environmental – to improve derelict infrastructure and the quality of the environment.
• Social – to overcome spiral of decline and deprivation and cycle of poverty.
• Economic – to improve job opportunities and bring income to the area
• Political – to raise money for projects through the ‘bid industry’ which is necessary for successful rebranding.

The need to rebrand

• Rebranding may be required in a variety of locations: urban areas, former industrial regions or parts of the countryside and coastal areas.

CITIES IN DECLINE

• Increasing costs of upkeep, developing and remodelling of Central business districts (CBDs).
• Many CBDs are becoming increasingly congested, inaccessible and expensive.
• Loss of retailing function from CBDs to out-of-town shopping centres.
• Loss of offices and commercial functions from city centres to suburban and peripheral locations, such as prestige science parks
• City centres perceived as dirty and unsafe.

BIRMINGHAM

• Image for many years was determined by events at the British Leyland factory (later Rover).
• The impression was that of a city with a disruptive and powerful workforce with weak management.
• Reconstruction of image in 1990s caught between 2 factors:

-Historical importance of the car industry to the identity of the region.

-A series of negative associations linked to the industry.

• Also identified with failures of ‘modernist’ project Modernism was an architectural style in 1950s and 1960s relying on simplistic and often angulay form using iron, steel, concrete and glass.
• Current wave of remaking is producing impressive new buildings and using culture and identity to drive regeneration.
• 1976 – National exhibition centre (NEC) opened on greenbelt land near to Birmingham city airport.
• Late 1980s – International convention centre (ICC) and symphony hall opened. Development of areas around broad street. Extention and refurbishment of Birmingham repertory theatre.
• 1193 – Initial development by Argent group of Brindley place – 7ha development costing £350m. Now houses sea life centre, Ikon and Royal bank of Scotland.
• 2003 – Bullring development opened at £530m, creating 8000 new jobs.
• 2005 – Completion of £40m redevelopment of Matthew Boulton college, teaching over 500 courses to 7000 students.
• 2013 – First half of redeveloping New Street Station opened 28^th April.

COALFIELD COMMUNITIES

• UK coal industry been in decline for years, during last 2 decades most coal mines in Britain were closed.
• Between 1984 and 1997, 170,000 coal mining jobs were lost in England.
• This raised problems for communities built around them:

-Areas were characterised by high levels of dereliction and ground contamination, mostly the legacy of mining.

-Not a strong tradition of self-employment.

-Lack of education and training in populations of coalfield areas.

-Proportion of population in 1991 classified as having long-term limiting illness was 15% in coalfield regions, compared to 12% in England on the whole.

COUNTRYSIDE IN CRISIS?

• Recently, the view that rural life is difficult and under threat has become prominent.
• Partly due to media coverage of farming crises, such as the 2001 foot-and-mouth outbreak.
• A number of rural pressure groups and interest groups such as the Countryside Alliance have highlighted difficulties faced by rural residents.
• Created a somewhat ant-idyllic view:

-Backward

-Unsophisticated

-Unfriendly (especially to incomers)

-Environmentally damaged

-Boring

Sleepy & slow

• These viewpoints have been reinforced by media representation. E.g. Tv shows such as Father Ted Portrays rural people as simple and backward.

PROBLEMS AT THE SEASIDE

• Most coastal settlements are dependent on seasonal, resort economy which is shrinking.
• Many coastal areas have also experienced decline in their fishing industries and this is coupled with high concentrations of migrant labour.
• Coastal regions can only be accessed from one direction and tend to be remote and difficult to get to.

BLACKPOOL IN DECLINE

• The Victorian working-class town of Blackpool drew 17 million visitors a year, now struggles to attract more than 10 million.
• Cheap package holidays drew many families away in the 1980s.
• Large Northern cities such as Leeds and Newcastle cornered the ‘weekend break’ market in 1990s.
• Fewer tourists mean fewer jobs.
• Between 1994 and 2005, the number of registered businesses in Blackpool fell by 6%, but the number in the country rose by 15%.
• Unemployment is now at 7% and wages have fallen.
• In 2002, the Average Blackpudlian was paid 17% less than the average Briton, this gap increased to 26% by 2006.

Space

Place

CBD

Rebranding

Reimaging

Regenerating

Geographical investigations - crowded coasts - competition for coasts

Geographical investigations

Crowded Coasts

Competition for coasts

COAST – That part of the land most affected by its proximity to the sea and that part of the ocean most affected by its proximity to the land.

• Coastal zone is most populated part of the world, containing many of the largest cities and manufacturing centres.
• Coastal lowlands are important food producers.
• Coastal ports play leading role in world trade.
• Coast become popular place for leisure, recreation and tourism.
• The coast is an open system involving inputs, internal transfers and outputs of water, sediment and energy in a state of dynamic equilibrium.
• This equilibrium is easily upset by human activities.

Coastal diversity

·        Diversity of landscapes exists along coast.

Nature of coasts:

LAND

-Shape

-Relief

-Presence or lack of beach

-Structure

-Resistance of rocks

-Sub-aerial processes

-River sediments

-Coastal ecosystems

SEA

-Coastal ecosystems

-Wave energy&direction

-Size%type of waves

-Local currents and longshore drift

-Tidal changes

-Water depth

-Offshore sediments

-Long-term changes in sea-level.

WEATHER AND CLIMATE

-Wind strength & direction

-Rainfall & temperature

-Storms & surges

HUMAN ACTIVITIES

-Intervention in natural systems

-Use of land for development

-Exploitation of resources

COASTAL ATTRACTIONS

·        Estimated that over half the worlds population and 2/3 of major cities are found within 60km of the sea.

THE COASTAL MAGNET

• In 1990, 30% of world population lived on the coast (60% in the 60km zone).
• By 2002, it was 40%.
• Coastal populations are growing at a rate 4X global average.
• Some of fastest growing megacities (Lagos, Shanghai) are on coast.
• “People are attracted to gorgeous natural settings until they become so full of people that the attraction is destroyed.”

·        In middle and higher latitudes, the coast has a more equable climate than inland locations = more comfortable living conditions.

·        From earliest times, much human movement between places was by sea rather than over land – no roads and wilderness impeded transport.

·        Coastal lowlands were well suited to farming and inshore waters provided fish.

·        Food security and transport were the original attractions for living in coastal locations.

The Lancashire coastal plain

• Stretches from river Mersey in south to southern edge of Lake district in north.
• Bounded by Pennine hills in Easter and low-lying coastline in west.
• The plain is very flat, much is only a few metres above sea level.
• Continuously inhabited since prehistoric.

• Human resources also play their part in development in coastal areas.
• As well as supply of labour, human resources include vision, skills and enterprise.
• These are critical in the transitions between stages – in case of Lancashire coastline, most recent of its transitions has been demanding.
• New uses must be found for redundant buildings & large areas of Liverpool, preston, southport and Blackpool need to be rebranded.
• Much of modern economy is about providinf services.
• Attraction & value of coast is largely to do with resources and opportunities.

Blackpool, UK

• For over 100 years, Blackpool was one of Europe’s leading coastal resorts, renowned for tower, lights & rock.
• During 18^th century it became fashionable for British rich to travel to seaside in summer, it was believed bathing in sea water could cure diseases.
• Some came to Blackpool but it remained a hamlet until first half of 19^th century.
• The railway in 1846 cut costs and time taken to reach Blackpool.
• Huge numbers of working-class began coming to Blackpool every weekend.
• In 1870s, each of the cotton textile towns of Lancashire began announcing “wakes week” when mills were shut for servicing.
• Thousands from these towns visited Blackpool during holiday period.
• Tower, promenades, piers, amusement arcades, theatres & music halls were built.
• By WWI = 4 million visitors during high season.
• During interwar years, prosperity continued and a new law that gave workers paid holiday.
• The town’s population reached almost 150,000.
• After WWII, fortunes began to decline with the advent of the package holiday and cheap air travel.
• Competition was from resorts in the Mediterranean which was also able to deliver guaranteed sun.
• Blackpool has since developed conference facilities and casinos but the town is still struggling to survive.

Benidorm, Spain

• Permanent population of 67,000.
• During summer peak season, population exceeds half a million.
• Development of Benidorm as coastal resort started in 1954 when the mayor drew up a plan of urban development.
• This took off in 1960s when it became popular with British tourists on package holidays.
• Tourist season is now all year round.
• Night life revolves around bars and clubs and is a strong pull for younger visitors.
• Within a few decades, Benidorm has transformed from a small village to an urban area of skyscraper hotels and apartment blocks, theme parks, pubs, clubs and restaurants.
• All three main beaches have ‘blue flag’ status.
• At height of season, they are some of the most densely populated parts of the world.

• Many traditional seaside resorts in UK seeking to rebrand e.g. Boscombe in Dorset.

Making waves at Boscombe, UK

• Plans to build an artificial surf reef close to Boscombe pier.
• To occupy 1 hectare.
• Made from large geotextile sand bags.
• Land-based tourist attractions around Boscombe need rejuvenation.
• Surf survey showed 77 good surfing days, but takes place on 153 days – 5,000 visits/yr.

-Reef to double good surfing days and host 10,000 visits per year.

• Estimated Cost - £1.1 million but business it brings to cancel that out.
• Actual cost - £4 million.
• Estimated to produce £10 million per year.
• Claim environmental effects =neutral – marine life thrives on beach & no effects to beach.
• Could accelerate erosion further down beach.
• Opened November 2009 – over a year late.
• Only achieved 4 of 11 design objectives.
• Closed since 2011 due to damage from boat propeller.

Radio silence

Sorry for the lack of posts recently, my laptop refuses to connect to the Internet and that's where all my posts are saved, I'll try and get it up and running this weekend but I can't promise anything as I'm doing the St George's Day Parade on Sunday.
Hopefully be back soon.
Alons-y

Holiday? What on earth are you talking about?

I'msorrywhatnow?

I say this, because i've seen a few family members this easter (mainly on egg collection) and they've all asked if i'm enjoying my easter holidays, my responses have been a mixture of "Of course not, i'm 17!" and "Holidays, are you mad?" and "I'm not on holiday".

Unfortunately, all of them being 70+ meant that my wit left them more mystified than humoured, turns out none of them had any idea I had exams - what did they think I was at school for? :P

Actually had a pretty productive week of revision so far, i'm ahead of schedule, despite spending the first half of it tearing house apart and helping my dad with various DIY jobs.

Productive Revision

Anyway, i've just been a complete idiot so will give you a life lesson, then drink about 10 litres of water - No matter how positive you are that the chocolate in the red wrapper is strawberry creme...READ THE DESCRIPTION, just in case it is in fact Hazelnut and causes you to swell up like that fish in Finding Nemo, it's not attractive, take my word for it.

Right, i'm to try and deflate now.

Alns-y! x

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