B2 -Understanding Our Environment


King = Kingdom

Philip = Phylus

Came = Class

Over = Order

For = Family

Gay = Genus

Sex = Species

Species = a group of organisms that can interbreed to produce fertile offspring.

Bacteria reproduce asexually so cannot technically be classed as a species. Mules are infertile hybrids so also cannot be classed as a species.

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Energy Flow

Pyramids of numbers = show the number of living materials at each stage in the food chain.

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

Pyramids of biomass can look different to pyramids of numbers if the producers are very large of if a small parasite lives on a lage animal. Pyramids of biomass are better at showing the trophic levels, but are difficult to construct because it involves removing water from an organism which will kill it.

Throughout the food-chain energy is wasted though egestionexcretion, and heat loss through respiration. Each trophic level 'loses' up to 90% of energy so there is less energy to be passed onto the next trophic level. 

Efficiency (%) = energy used for growth/energy input x 100

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The Carbon Cycle


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Nitrogen Cycle

-Plants take in nitrogen as nitrates from the soil.

-Nitrogen compounds are broken down by decomposers and returned to the soil.

-Plants and animals die and decay.

-Decomposers convert the proteins and urea into ammonia.

-Nitrifying bacteria convert the ammonia into nitrates.

-Denitrifying bacteria converts nitrates into nitrogen gases.

-Nitrogen-fixing bacteria live in root nodules and fix nitrogen gas.

Decomposers need oxygen and a suitable pH to break down dead material.

Decay will be slower in waterlogged soil (less oxygen).

Acidic soil also slows down decay.

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Similar animals in the same habitat compete for resources. Members of the same species will compete for mates.

Ecological niche = describes the habitat of an organism and its role within that habitat.

Interspecific competition = between different organisms.

Intraspecific competition = between the same species.

Predator peaks in numbers often come just after peaks in prey. 

Different species can also become dependant on each other. Parasites feed on or in host organisms, as a result the host suffers from this relationship.

Mutualism = when both organisms benefit from the relationship. eg. with pollination

Pea plants are legumes which have root nodules. The nodules contain nitrogen-fixing bacteria which turn nitrogen into nitrogen-containing chemicals; these are given back to the pea. The pea plant gives the bacteria sugars for photosynthesis (mutualism).

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Adapting to cold environments:

-Thick fur and layers of fat for insulation.

-Large with small ear, to decrease the surface area to volume ration.

-Penguins have a counter-current heat exchange system.

Adapting to warm, dry environments:

-Very little hair.

-Big ears for a larger surface area to volume ratio.

-Seek shade during the day when the sun is hottest.

-Concentrated urine to conserve the limited water supplies.

-Cacti have spines, deep roots and store water in their large stem.

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Natural Selection

Charles Darwin wrote the theory of natural selection to explain the process of evolution. When animals and plants are better adapted to their environment they are more likely to survive. We know now that characteristics are passed on by genes through reproduction.

There is variation in species, there is competition within the species so only the best adapted survive (survival of the fittest).The survivors pass on the better adaptations.

Over time, large amounts of evolution will cause the organisms to be classed as different species.

Bacteria use evolution to develop resistance to anti-biotic drugs.

Darwin's theory was not popularly accepted at first due to his lack of evidence and because of the idea that God created all species.

Now, it is more widely accepted because it has been investigated by a wide range of scientists and explains many observations.

Before Darwin, Lamark's theory (law of acquired characteristics) said that animals such as giraffes develop characteristics such as their long necks to feed and this was automatically passed on to their offspring.

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Pollution types which cause the biggest concern are: CFCscarbon dioxide and sulfur dioxide.

Pollution in water and air can be estimated using indicator species.

Mayfly larva can only live in clean water, whereas waterlouse, bloodworm and mussels can live in pollutedwater. 

Lichen grows on trees when the air is clean, as it is killed by pollution from motor engines.

Using direct methods to measure pollution can give more accurate results.

For example, oxygen probes can be used to measure exact amounts of oxygen in a pond. However, it is expensive and only gives information at any one time.

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Conservation = trying to preserve a variety of organisms and their habitats.

It can protect our food supply, medicinal plants and animals, organisms and habitats used for recreational purposes and prevent damage to food chains.

Important factors of conservation are: the population sizenumber of suitable habitats and levels of competition between species.

Sustainable development = meeting the needs of today, without sacraficing available resources for the future and preventing further, permanent damage.

Fossil fuels will run out, so due to the increase in demand for energy we must find alternative, more sustainable fuels.

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