B2 - Specification

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Variety of life is a continuous spectrum which makes it difficult to place organisms into distinct groups.

Kingdom - Phylum - Class - Order - Family - Genus - Species

Evolutionary Relationships - common ancestors and how organisms have evolved

Ecological Relationships - relationship between organisms in an ecosystem

Natural classificatoin - based on observed characteristics (evolutionary relationships)

Artificial classification - natural relationships between organisms. It considers more evidence, including internal and external features.

DNA sequencing has lead to changes in understanding of classification because you can see which organisms are closely related.

Systems of classification change over time because more species are found and new discoveries, especially in genetics, are made. Accepted systems of classification have historically changed.

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Classification 2

Evolutionary relationships between organisms in the kingdoms can be displayed in evolutionary trees.

The evolutionary relationships of organisms in a group can be modelled by analysing multiple characteristics and this has been facilitated by ICT.

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Classification 3

Species - a group of organisms which are capable of interbreeding to produce fertile offspring.

The binomial naming system is used as the international basis for the naming system so all languages can understand the classification.

Problems with classifying organisms:

  • hybrids (are not fertile)
  • organisms that only reproduce asexually
  • evolution as a continuing process and organisms are constantly changing to suit their environment.
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Classification 4

Closely related species:

  • share a relatively recent common ancestor
  • may have different features if they live in different types of habitats so may have developed similar features.

For example whales, sharks and dolphins all look quite similar (ecological relationship) but have developed from a different ancestor (evolutionary relationship).

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Pyramids of biomass show the dry mass of living material at each stage in the food chain.

Always pyramid shaped because they take the mass of organisms into account. But pyramids of numbers not always pyramid shaped because they take into account numbers not mass.

Difficulties in constructing pyramids:

  • Some organisms may belong to more than one trophic level.
  • Measuring biomass is tricky because involves drying out and weighing the mass of an organism (difficult with such organisms as trees)

Efficiency of energy transfer explains the shape of biomass pyramids. Biomass is lost through the stages through living processes.

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Energy Flow

Some energy is transferred to less useful forms at each stage of the food chain:

  • heat from respiration
  • excretion
  • egestion
  • movement

Excretory products, faeces and uneaten parts can be used as the starting point for other food chains.

Food chains rarely have fouth or fifth degree consumers as there isn't enough energy to pass on.

Efficiency = Energy converted to biomass/total energy taken in x100

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Recycling of nutrients takes longer in waterlogged or acidic soils than it does in well drained netural soils because waterlogged soil lacks oxygen for decomposers and acidic soil is not the best pH for decomposers.

Recycling carbon in nature:

  • plants removing carbon dioxide from the air by photosynthesis
  • feeding passes carbon compounds along the food chain or web
  • plants and animals releasing carbon dioxide into the air, as a product of respiration
  • burning a fossil fuel (combustion) releasing carbon dioxide
  • soil bacteria and fungi (decomposers) releasing carbon dioxide into the air
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Carbon Recycled in the Sea

1. Marine organisms make shells of carbonates

2. Shells fossilise to become limestone

3. Volcanic eruptions heat the limestone and release carbon dioxide. Also during the weathering of rock.

4. Oceans absorb the carbon dioxide because carbon sinks

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Nitrogen Recycling

Nitrogen is recycled in nature due to:

  • plants taking in nitrates from the soil to make protein for growth
  • feeding passes nitrates along a food chain or web
  • nitrogen compounds in dead plants and animals being broken down by decomposers and returning to the soil

Nitrogen-fixing bacteria: convert atmospheric nitrogen into nitrates in the soil. Bacteria live in the soil while other live in root nudules of plants like peas.

Nitrifying bacteria: convert ammonium compounds into nitrates in the soil.

Denitrigying bacteria: Convert nitrates and ammonium compounds into atmospheric nitrogen.

Soil bacteria and fungi, decomposers, convert proteins and urea into ammonia.

Energy released by lightning causes oxygen and nitrogen to combine into nirtogen oxides which dissolve in water.

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Similar animals in the same habitat will be in close competition because they are competing for the same limited resources.

Animals compete for food, water, shelter and mates.

Plants compete for light, water and minerals.

Intraspecific: individuals of the same species are competing for the same resource.

Interspecific: individuals of different species compete for the same resource.

Intraspecific is more sigificant because these organisms have exactly the same needs.

Ecological niche:an organisms place and function - in direct competition for resources they need. Eg. red and grey squirrels

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Interdependance 2

Within nature there's a delicate balance between the population of the predator and its prey. But the prey will always out number the predators.

There will be cyclical fluctuation in the numbers of each species because the numbers of predator and prey will regulate each other.

Lots of hares, lynx have more food so they breed and numbers go up.

Then eat alot of hares so their numbers go down. With less food availiable, the lynx numbers go down.

Cause and effect, peaks and troughs in predators and prey numbers are out of phase.

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Parasitism: parasite benefits to the living host's detriment, including fleas and tapeworms.

Mutualism: both species benefit including cleaner species and pollution by insects.

Interdepence of organism determines their distribution and abundance.

Nitrogen-fixing bacteria in the root nodules of leguminous plants are an example of mutualism. The bacteria in the root nodules take sugars from the plant to use in respiration. They also convert nitrogen into nitrates, which benefits the plant because it enables it to survive in nitrogen-poor soils. Bacteria gain sugars and plant gains nitrates.

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Adaptations to cold environments:

  • being well insulated to reduce heat loss
  • having a small surface area to volume ratio to prevent heat loss
  • behavioural adaptation to help animal to survive cold temperatures. Eg hiberations and migrations.

Heat Exchange Systems:  Warm blood enters the feet and flippers flows past cold blood leaving the feet and flippers and warms it up. The warmed blood re-enters the rest of the body, doesn't affect core temp.

Adaptations to hot environments:

  • behavioural and anatomical methods of increasing heat loss and reducing gain (finding somewhere cool to go, only going out at night, shedding hair.
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Adaptations 2

Adaptation to dry environments:

  • behavioural and anatomical methods for reducing water loss - CACTI - having long roots to reduce water loss, having thick spines to reduce water loss and protect water stored in the spongy layer from predators.

Some organisms are biochemically adapted to extreme conditions, including different optimum temperatures for enzymes

Extremophiles: organisms that live in extreme environments

Anit-freeze proteins: in some artic fish to provent ice crystals growing inside tissues.

Animals and plants that are adapted to an environment are better adapted to compete for limited resources, so they can survive and produce offspring.

Specialists - well suited to only certain habitats

Generalists - live in a range of habitiats but can easily be out competed.

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Natural Selection

Darwin's theory of evolution by natural selection:

  • presence of natural variation
  • competition for limited resources
  • survival of the fittest
  • inheritance of 'sucessful' adaptations

Adaptations are controlled by genes and that these genes can be passed on to the next generation.

Over long periods of time the changes brought about by natural selection may result in the formation of a new species.

Speciation requires geographical or reproductive isolation of populations.

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Natural Selection

The theory of evolution of natural selection met with an initially hostile response because they went against the church and the Bible.

Now widely accepted because:

  • explains a wide range of observations
  • it has been discussed and tested by a wide range of scientists

Larmark's idea: inheritance of aquired charactoristics but changed during their lifetime.

Rejected because there was no evidence that changes happened in a lifetime. And his explanation didn't have a genetic basis.

Individuals better adapted are more likely to survive. 'Survival of the Fittest'. The survivers will pass on sucessful gene to their offspring. Resulting in an improved organism being evolved through natural selection.

As new discoveries have been made and inheritance is known, the theory has been developed.

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Population and Pollution

Human population is increasing exponentially.

Population growth is the result of the birth rate exceeding the death rate.

Causes and conseqences of:

Global warming: amount of carbon dioxide in the atmosphere has increased, meaning more energy being reflected back. Causing - melting of polar ice caps, flooding and changes in climate and weather patterns.

Ozone depletion: CFCs in factories, fridges and aerosols. Causing - more harmful UV rays reaching earth, skin cancer.

Acid Rain: burning fossil fuels which release acidic gases like sulfur dioxide and nitrogen oxides. Dissolve in rainwater to make acidic rain. Causing - metals corroding, dissolving rocks and statues, destruction of forests and lakes becoming acidic killing fish and wildlife.

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Population and Pollution 2

Developed countries of the world, with a small proportion of the worlds population, have the greatest impact on the use of resources and the creation of pollution. This is because they are developed and are richer to afford the energy.

Carbon Footprint: amount of greenhouse gases a person or event is responsible for emitting in a given timescale.

Consequences of exponential growth:

  • Raw materials like oil and minerals are being used up increaseingly quickly
  • Pollution and waste are building up at an alarming rate
  • Resources in short supply, more and more competition for basic things like food and water, becoming expensive.
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Indicator Species

The presence/absence of indicator species helps to indicate the levels of pollution;

  • water pollution - water louse, sludge worm, rat-tailed maggot, fly larvae
  • air pollution - lichen

Advantages and disadvantages of living: (measure occurence of indicator species)

A: Reliable, long term, easily identified, cheap, minimal impact on other organisms

D: Seasonal, organisms may be killed, organisms may leave area

Advantages and disadvantges of non-living: (direct measurement of pollutant levels)

A: Identify source of pollution, gives quantitive data, easily compared

D: Expensive as specialist equptment needed, more people needed.

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Reasons for conservation:

  • protecting human food supply
  • ensuring minmal damage to food chains
  • future identification of plants for medical purposes
  • cultural aspects

Species are at a risk of extinction if the number of individuals or habitats fall below critical level because they are critically endangered, they have a small chance of survival.

If there isn't enough genetic variation in a population, species become at risk of extinction. This is because if the organisms are genetically very similar, a disease that kills one may kill them all.

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Conservation 2

Conversation programme in terms of:

  • genetic variation of key species
  • viability of populations
  • availible habitats
  • interaction between species
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Whales when alive: tourism and Whales when dead: food, oil, cosmetics

Keeping whales in captivity:

  • entertainment
  • research
  • captive breeding programmes
  • lack of freedom

Not all aspects of whales understood:

  • communication
  • migration programmes
  • survival at extreme depths

Issus concerning whaling: getting international agreement, policing and enforcing such agreements and hunting for research.

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Sustainable Development: ensuring that resources can be used and maintained without compromising the needs of future generations.

Fish stocks and woodland can be developed using:

  • education
  • quotas on fishing
  • re-planting of woodland

Population size, waste products and food and energy demands effect sustainable development as the quickest and cheepest ways to meet demands are not always the most sustainable.

Sustainability requires planning and co-orperation at local, national and international levels.

Sustainable development can help protect endangered species eg quotas for whaling.

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Bhoomi Amin


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