MODULE B2-UNDERSTANDING OUR ENVIRONMENT

CLASSIFICATION: Organsing living organisms into groups

• they help us to understand how organisms are related (evolutionary relationships)
• we know how they interact with each other (ecological relationship)

NATURAL CLASSFICATION SYSTEMS: based on evolutionary relationships and genetic similarities between organisms.

ARTIFICIAL CLASSIFICATION SYSTEMS: based on appearance rather than genes. Used to identify organisms.

Genus: group of closely related species Species: group of organisms that can interbreed to produce fertile offspringIt can be difficult to classify organisms into these distinct groups because many organisms share characteristics of multiple groups.

Classification changes over time:

• Newly discovered species might not really fit into any of the organisms.    
• DNA sequencing allows us to see genetic differences between different groups.

SPECIES: Group of organisms which can interbreed to produce fertile offspring.

Problems with classifying organisms into species:

• ASEXUAL REPRODUCTION: no interbreeding with another organism so they don't fit the definition of a species.
• HYBRIDS: (male from one species and a female from another species) They are usually infertile so they aren't new species.
• EVOLUTION IS A CONTINUOUS PROCESS: they evolve over time, the classification might have to change. A group of organisms can change so much that it creates a new species.

BINOMIAL SYSTEM: TWO PART LATIN NAME GIVEN TO EACH SPECIES. FIRST PART IS THE GENUS AND THE SECOND PARTY REFERS TO THE SPECIES. 

USED BY SCIENTISTS ALL OVER THE WORLD, AVOIDS POTENTIAL CONFUSION. CLOSELY RELATED SPECIES HAVE RECENT COMMON ANCESTORS.

PYRAMIDS OF BIOMASS:

• Each bar on a pyramid of biomass shows the mass of living material at that stage of the food chain.
• Biomass pyramids are always pyramid shaped BECAUSE biomass is lost at each stage in the food chain.
• To construct a pyramid of biomass you use the 'dry biomass' of the organisms.

DIFFICULTY WITH BIOMASS:

• You have to kill the organisms to work it out- unethical
• some organisms feed at more than one trophic level

PYRAMIDS OF NUMBERS:

• Each bar shows the number of organisms at that stage of the food chain- not their mass.
• usually other shapes but can be pyramids too.

• Energy from the sun is the source of energy for nearly all life on Earth
• The energy lost at each stage is used for STAYING ALIVE e.g. respiration
• Most of this energy is lost to the surroundings as HEAT- their bodies must be kept at a constant temperature (normally higher than their surroundings)
• MATERIAL and ENERGY are also lost from the food chain as WASTE PRODUCTS. e.g. excretion, egestion

You never get food chains with more than about 5 trophic levels because so much energy is lost eat each stage so there's not enough left to support other organisms.

• You get biomass pyramids because most of the biomass is lost and so does not become biomass in the next level up.

efficiency= energy availavble to the next level/ energy that was available to the previous level x100

ORGANISMS COMPETE TO SURVIVE:

• In order to SURVIVE and REPRODUCE, organisms must COMPETE against each other for the resources that they need to live.
• SIMILAR ORGANISMS in the SAME HABITAT will be in the CLOSEST COMPETITION- they'll be competing for similar ECOLOGICAL NICHE

Ecological Niche: It's how it fits into its ecosystem. It depends on things like where the individuals live and what they feed on.

INTERESPECFIC COMPETITION: where organisms compete for resources against individuals of another species.

INTRASPECIFIC COMPETITION: where organisms compete for resources against individuals of the same species.

• Intraspecfic competition often has a bigger impact on organisms than interspecific competition because same species have exactly the same needs so they'll compete for lots of resources.

POPULATIONS OF PREY AND PREDATORS GO IN CYCLES:

• Predator-prey cycles are always out of phase with each other. This is because it takes a while for one population to respond to changes in the other population.

PARASITIC AND MUTUALISTIC RELATIONSHIPS ARE OTHER TYPES OF INTERACTIONS:

• Parasites: They live off a host. They take what they need to survive WITHOUT giving anything back. This often HARMS the host- which makes it a win lost situation.      

              1) tapeworms absorb a lot of nutrients from the host. Fleas are parasites.

• Mutualism: A relationship where both organisms benefit- so its a win win relationship.

              1) 'cleaner species' (oxpeckers) live on the backs of buffalo, they eat the pest but they also warn the oxpecker of predators.

              2) lots of plants are pollinated by insects, allowing them to reproduce. In return, the insects get a sip of sweet, sugary nectar.

ADAPTATIONS HELP ORGANISMS TO SURVIVE

• adaptations are the features that organisms have that make them better suited to their environment.
• organisms that are adaptated are better able to compete for resources.
• they are more likely to REPRODUCE, SURVIVE AND PASS ON THEIR ADAPTATIONS TO THEIR OFFSPRING.

SPECIALISTS: Organisms which are highly adapted to survive in a SPECIFIC HABITAT

GENERALISTS: Organisms that are adapted to survive in a RANGE OF DIFFERENT HABITATS.

If the conditions are STABLE: specialists will out-compete generalists as they're better adapted to specific conditions

If the conditions CHANGE: generalists will out compete specialists as they won't adapt to new conditions.

Some organisms have biochemical adaptations to extreme conditions:

1)  Some organisms can tolerate extreme conditions.

2) Organisms that are adapted to live in seriously extreme conditions are called EXTREMOPHILES.

EXAMPLE 1)                  

• EXTREMOPHILE BACTERIA: live in very hot enviroments have enzymes that work best at a much higher optimum temperature
• These enzymes are able to function normally at temperatures that would DENATURE enzymes from other organisms.

EXAMPLE 2)

• Organisms that live in very cold environments sometimes have special ANTI FREEZE PROTEINS.
• These proteins interfere with the formation and growth of ice crystals in the cells, stopping the cells from being damaged by ice.

Anatomical adaptations can reduce heat loss:

• Having a THICK COAT or  LAYER OF BLUBBER to INSULATE the body and trap heat in.
• Having a LARGE SIZE and COMPACT BODY SHAPE to give a small surface area to volume ratio. This reduces heat loss as less body heat can be lost through the surface of the skin.

Having COUNTER CURRENT HEAT EXCHANGE SYSTEMS:

1) Blood vessels going to and from the feet carry blood that flows in opposite directions.

2) The vessels pass close to each other, allwing heat to transfer between them.

3) Warm blood flowing in arteries to the feet heats cold blood returning to the heart in the veins.

4) This means that the feet stay cold, but it stops cold blood from cooling down the rest of the body.

• many species migrate to warmer climates during the winter months to avoid having to cope with the cold conditions.
• Some species hibernate during the winter months. They save energy as the animal doesn't have to find food.

BEHAVIOURAL ADAPTATIONS CAN INCREASES HEAT LOSS AND REDUCE HEAT GAIN:

• They often spend time in the shade or underground to minimise the amount of heat their bodies gain from their surroundings.
• Animals can also reduce their heat gain by being active at night, when it is much colder.
• Animals can increase heat loss by bathing in water, as the water evaporates it transfers heat from the skin to the surroundings, cooling the animal down.

ANATOMICAL ADAPTATIONS CAN ALSO INCREASE HEAT LOSS:

• Animals are often small, large surface area to volume ratio which allows them to lose more body heat to their surroundings.
• They can have LARGE EARS, can also increase an animal's surface area to volume ratio. LARGE THIN EARS allow MORE BLOOD TO FLOW near the SURFACE of the skin-so more heat from the blood can be radiated to the surroundings.
• Some animals store fat in just one part of the body- this stops the rest of the body from being from being too well insulated and allows heat to be lost more easily.

SOME ORGANISMS HAVE ADAPTED TO LIVING IN DRY ENVIRONMENTS:

Organisms that live in dry environments have to be adapted to minimise the amount of water that they lose to the environment

Some desert plants...

• have a rounded shape, giving them A SMALL SA TO V RATIO to minimise water loss from the surface.
• have a THICK WAXY LAYER AND SPINES instead of leaves to further reduce water loss.
• STORE WATER in their stems to allow them to survive in times of extreme drought.
• have SHALLOW but very extensive, roots to ensure water is ABSORBED quickly over a large area.

Some desert animals...

• have SPECIALISED KIDNEYS that allow them to produce very concentrated urine, with very low water content.
• have NO SWEAT GLANDS, preventing them from losing water through sweating.
• spend lots of time in UNDERGROUND burrows, where the AIR contains MORE MOISTURE than on the surface.

THEORY OF NATURAL SELECTION:

• Darwin knew that organisms in a species show WIDE VARIATION. He also knew that organisms have to COMPETE for LIMITED RESOURCES in an ecosystem.
• He concluded that the organisms that are the BEST ADAPTED would be MORE SUCCESSFUL COMPETITORS and would be MORE LIKELY TO SURVIVE: "SURVIVAL OF THE FITTEST."
• The successful organisms that survive are more likely to reproduce and pass on the adaptations that made them successful to their offspring.

New discoveries have helped to develop the theory of natural selection:

1) He couldn't give a good explanation for why new characterisitcs appeared or exactly how individual organisms passed on beneficial adaptations to their offspring.

2) DNA wasn't discovered until 50 years after his theory was published.

THE DEVELOPMENT OF A NEW SPECIES IS CALLED SPECIATION:

SPECIATION: Over a long period of time, organisms may change so much because of natural selection that a completely new species is formed.

SPECIATION:

It happens when populations of the same species change enough to become REPRODUCTIVELY ISOLATED- this means that they can't interbreed to produce fertile offspring.

Reproductive isolation can be caused by geographic isolation:

1) A physical barrier divides a population of a species- the two new populations are unable to mix.

2) Different mutations create different new features in the two groups of organisms.

3) Natural selection works on the new features so that, if they are of benefit, they spread through each of the populations.

4) Since conditions on each side of the barrier will be slightly different, the features that are beneficial will be different for each population.

5) Eventually, individuals from the two populations will have such different features that they won't be able to breed together to produce fertile offspring. They'll have become reproductively isolated and the two groups will be separate species.

NOT EVERYONE AGREED WITH DARWIN...

• The theory went against common religious beliefs
• He couldn't explain why new, useful characteristics appeared.
• There wasn't enough evidence to convince many scientists.

LAMARCK HAD A CONFLICTING THEORY OF EVOLUTION:

• He said that if a CHARACTERISTIC was used a lot by an animal then it would become more DEVELOPED. That these ACQUIRED CHARACTERISTICS could be passed on to the ANIMAL'S OFFSPRING.
• They concluded that ACQUIRED CHARACTERISTICS DO NOT HAVE GENETIC BASIS- so they're unable to be passed on.

NOWADAYS, PEOPLE ACCEPT DARWIN'S THEORY:

• The theory has been debated and tested
• The theory offers a plausible explanation for so many observations of plants and animals.

THE CARBON CYCLE SHOWS HOW CARBON IS RECYCLED:

• The cycle is powered by PHOTOSYNTHESIS
• The plants convert the carbon from CO2 in the air into sugars. Plants can then incorporate this carbon into their carbohydrates, as well as FATS AND PROTEINS.
• Eating passes the carbon compounds in the plant along to ANIMALS in a food chain or web.
• Both plant and animal RESPIRATION while the organisms are alive RELEASES CO2 back into the AIR.
• Plants and animals eventually DIE AND DECAY. They're then broke down by BACTERIA AND FUNGI IN THE SOIL.
• These decomposers RELEASE CO2 back into the air by RESPIRATION as they break down the material.
• Over millions of years, material from dead plants and animals can also form FOSSIL FUELS like coal and oil.
• When these fossil fuels ARE BURNED CO2 is RELEASED back into the air.

DECOMPOSITION IS SLOWER IN WATERLOGGED AND ACIDIC SOILS:

• RECYCLING of carbon and other nutrients takes LONGER in WATERLOGGED SOILS than in WELL DRAINED SOILS.
• This is because the BACTERIA and FUNGI that decompose organic material usually NEED OXYGEN to RESPIRE and PRODUCE ENERGY. Waterlogged soils don't have much OXYGEN- so the decomposers have LESS ENERGY and work MORE SLOWLY.
• Nutrients recycling also takes LONGER in highly ACIDIC SOILS than in NEUTRAL SOILS. This is because extremes of pH SLOW DOWN the REPRODUCTION of decomposers or KILL them outright.

CARBON IS ALSO RECYCLED IN THE SEA:

• Millions of species of marine organisms make SHELLS made of CARBONATES
• When these organisms die the shells fall to the ocean floor and eventually form LIMESTONE ROCKS.
• The carbon in these rocks returns to the atomsphere as CO2 during VOLCANIC ERUPTIONS or when the rocks ARE WEATHERED DOWN.
• The oceans can also ABSORB large amounts of CO2, acting as huge stores of carbon called 'CARBON SINKS'

NITROGEN IS RECYCLED IN THE NITROGEN CYCLE:

• NITROGEN is NEEDED for making PROTEINS for growth, so living organisms have to get it somehow.
• Plants get their nitrogen from the SOIL, so nitrogen in the air has to be turned into NITRATES BEFORE plants can use it. NITROGEN COMPOUNDS are then passed along FOOD CHAINS and WEBS as animals eat plants.
• DECOMPOSERS break down PROTEINS in rotting plants and animals, and UREA in animal waste, into AMMONIA. This returns the NITROGEN COMPOUNDS to the soil- so the nitrogen in these organisms is RECYCLED.
• NITROGEN FIXATION is the process of turning N2 FROM THE AIR into NITROGEN COMPOUNDS in the soil which PLANTS CAN USE.
  • 1) Lightning- energy in a bolt of lightning makes nitrogen react with oxygen.
  • 2) Nitrogen fixing bacteria in roots and soil.

NITROGEN IS RECYCLED IN THE NITROGEN CYCLE:

• NITROGEN is NEEDED for making PROTEINS for growth, so living organisms have to get it somehow.
• Plants get their nitrogen from the SOIL, so nitrogen in the air has to be turned into NITRATES BEFORE plants can use it. NITROGEN COMPOUNDS are then passed along FOOD CHAINS and WEBS as animals eat plants.
• DECOMPOSERS break down PROTEINS in rotting plants and animals, and UREA in animal waste, into AMMONIA. This returns the NITROGEN COMPOUNDS to the soil- so the nitrogen in these organisms is RECYCLED.
• NITROGEN FIXATION is the process of turning N2 FROM THE AIR into NITROGEN COMPOUNDS in the soil which PLANTS CAN USE.
  • 1) Lightning- energy in a bolt of lightning makes nitrogen react with oxygen.
  • 2) Nitrogen fixing bacteria in roots and soil.

THERE ARE FOUR DIFFERENT TYPES OF BACTERIA INVOLVED IN THE NITROGEN CYCLE:

• DECOMPOSERS: decompose PROTEINS and UREA and turn them into AMMONIA
• NITRIFYING BACTERIA: turn AMMONIA in decaying matter into NITRATES.
• NITROGEN FIXING BACTERIA: turn ATMOSPHERE N2 into NITROGEN COMPOUNDS that plants can use.
• DENITRIFYING BACTERIA: turn NITRATES back into N2 gas. This is of no benefit to living organisms.

Some NITROGEN FIXING BACTERIA live in the SOIL.

Others live in NODULES on the roots of LEGUME PLANTS- this is why legume plants are so good at putting nitrogen BACK INTO THE SOIL.

The plants have a MUTUALISTIC RELATIONSHIP with the bacteria- the bacteria get FOOD FROM THE PLANT, AND THE PLANT GETS NITROGEN COMPOUNDS from the bacteria to make into PROTEINS. SO THE RELATIONSHIP BENEFITS BOTH OF THEM.

HUMAN POPULATION IS INCREASING:

• Increases when the birth rate is higher than the death rate.
• The rapidly increasing population is putting pressure on the environment- more resources are being used up and more pollution's being produced.
• The higher standard of living amongst more developed countries demands even more resources and even though the developed countries have only a small proportion of the world's population, they cause a large proportion of the pollution.

INCREASING AMOUNTS OF POLLUTION ARE CAUSING..

1) GLOBAL WARMING- When fossil fuels are burned they release lots of CO2 which is a greenhouse gas. The greenhouse gases trap heat in the atmosphere which causes global temperature to rise. Sea level will rise. People are measuring GG so they can reduce emission.

2) ACID RAIN- When fossil fuels/ waste materials are burned sulfur dioxide is released. It reacts with water to form sulfuric acid. Acid rain damages soils and trees, lakes become acidic, damages limestone and buildings.

3) OZONE DEPELTION- CFCs break down ozone in the upper atomsphere- allows UV rays to reach the Earth's surface. Increases the risk of skin cancer- kills plankton in the sea, affects the sea ecosystem, prediction of fish levels dropping.

INDICATOR SPECIES CAN BE USED TO SHOW POLLUTION:

• Lichens- used to monitor air quality- they're damaged by pollution. The cleaner the air, the greater the diversity of lichens that survive.
• Mayfly larvae- used to monitor water quality- they can't survive in polluted water.
• Other species have adapted to live in polluted conditions-
  • Water lice, rat tailed maggots and sludgeworms indicate polluted water.

POLLUTION LEVEL CAN BE MEASURED:

• You can do a survey to see if a species is present or absent from an area.
• Counting the number of times an indicator species occurs in an area will give you a numerical value.
• Sensitive instruments can measure the concentrations of chemical pollutants.
• Satallite data can also be used to indicate pollutant level.

LIVING METHODS (INDICATOR SPECIES):

Advantages/ Disadvantages-

• It is quick, cheap and easy way of saying whether an area is polluted or not
• BUT... factors other than pollution (temp) can influence the survival of indicator species so living methods aren't always reliable.

NON- LIVING METHODS:

Advantages/ Disadvantages-

• Directly measuring the pollutants gives reliable, numerical data that's easy to compare between different sites.
• The exact pollutants can be identified too.
• BUT... non living methods often require more expensive equipment and trained workers.

IF THESE FACTORS FALL BELOW A CRITICAL LEVEL THEN THEY BECOME EXTINCE OR ENDANGERED:

• The number of habitats- it can be hard for them to find food and shelter if there isn't enough suitable habitats.
• The number of individuals- it'll be hard to find mates and there won't be much genetic variation in the population.
• Genetic variation- this is the number of different alleles in a population. If it is low then species are less likely to be able to adapt to changes in the environment.

YOU NEED TO BE ABLE TO EVALUATE CONSERVATION PROGRAMMES: conservation programmes are designed to save endangered plants and animals.

1) Genetic variation: it should have enough GV to survive the appearance of new diseases.

2) Viability of populations: they should be able to reproduce, they should be large enough to prevent interbreeding.

3) Available habitats: right type of habitat is important if the organism is a specialist.

4) Interaction between species: it's important that species interact with each other as they would in their natural environment.

CONSERVATION PROGRAMMES BENEFIT WILDLIFE AND HUMANS:

• PROTECTING THE HUMAN FOOD SUPPLY: over fishing has greatly reduced fish stocks in the world's oceans. Programmes can ensure that future generations will have fish to eat.
• ENSURING MINIMAL DAMAGE TO FOOD CHAINS: if one species becomes extinct it will affect all the organisms that feed on and are eaten by that species, so the whole food chain is affected.
• PROVIDING FUTURE MEDICINES: many medicines come from plants. Undiscovered plants may contain new medicinal chemicals.
• CULTURAL ASPECTS: individual species may be important in a nation's or an area's cultural heritage.

DEVELOPMENT HAS TO BE SUSTAINABLE:

• We need to produce more food so we'll need more land for farming
• We use up more energy, we need to find an alternative energy source.
• We're producing more waste, it needs to be put somewhere.

SUSTAINABLE DEVELOPMENT: Providing for the needs for today's increasing population without harming the environment.

Examples of sustainable development:

• Fishing quotas- prevents certain types of fish from becoming extinct in certain areas.
• To make the production of wood and paper sustainable there are laws insisting that logging companies plant new trees to replace every that are cut off.

Education is important as they become more aware and are likely to help.

CASE STUDY: WHALES- SOME SPECIES ARE ENDANGERED:

• Whales have commercial value- profit can be made dead or alive from them.
• They're a tourist attraction
• Whale meat and oil can be used. Can be used for cosmetics too.
• The INTERNATIONAL WHALING COMMISSION has struggled to get nations to agree to restrict whaling.
• A lot of illegal whaling happens, people don't follow the laws.
• Some whales are kept in captivity:
  • They don't have much space and are used for entertaining people- they lose their freedom
  • Captive breeding programmes allow whales to be bred in numbers and released back into the wild.
  • Research on captive whales can help use understand their needs better to help conservation. There is still a lot we don't fully understand about whales.