On the wild side revision notes

Notes from the SNAB book. 

About photosynthesis, global warming, succession....

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Ecosystems are made up of abiotic and biotic factors. Abiotic factors are physical or chemical where
biotic factors are to do with other organisms. Within these ecosystems there can be many different
habitats, each with its own set of distinct conditions. There is a community of organisms living in the
ecosystem. These organisms live there because they are adapted to living in those conditions and
are likely to survive and reproduce there.
Abiotic factors include solar energy input, climate, topography, oxygen availability, edaphic,
pollution, catastrophes. Biotic factors include competition [interspecific and intraspecific], grazing,
predation, parasitism, mutualism.
Biotic factors are normally density dependant. Anthropogenic factors arise from human activity and
can be both abiotic and biotic.
A succession is when an ecosystem changes over time. A primary succession is one that takes place
on new ground that has never been colonised before. A secondary succession is one that takes place
where there has been plants before but has been cleared and succession starts again. A deflected
succession is one where succession is stopped from taking place by human activity and maintenance.
A pioneer plant is the first plants to colonise the bare ground. The climax community is the last
organisms to dominate over the ground (usually a wood).
Producers (aka autotrophs) can make their own food by photosynthesis. In photosynthesis there is a
light-dependant and light-independent stage. The diagram below is a basic over-view of the
light-dependant reaction
This takes
place in the
membrane in

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The diagram below shows the light-independent reaction also called the Calvin cycle.
This takes place in the stroma of the chloroplast.
In an ecosystem energy is transferred. Autotrophs make their own food, however heterotrophs
cannot make their own food so need to eat to gain energy. There are a number of different types of
heterotroph. Primary consumers (aka herbivores) eat plants (autotrophs). Secondary consumers (aka
carnivores) eat other animals and don't eat plants.…read more

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The sun radiates energy and is absorbed by the earth which then re-emits infra-red radiation. Gases
that stop infrared radiation from the sun, escaping from the earth are called greenhouse gases (act
like a greenhouse). This keeps the earth warm and is called the greenhouse effect. Methane is
produced through anaerobic decay of organic matter, domestic waste in landfills, belching and
farting of animals and combustion of fossil fuels.…read more

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When we gently heat DNA to separate the double helix (hydrogen bonds break) and replace 1
strand of DNA with a chimps DNA strand we get a hybrid DNA. The more similar the DNA, the more
they will stick together. By comparing the sequence of bases in DNA or the amino acid sequence in
proteins of different species, you can work out how closely related they are on the evolutionary
Organisms experience selection pressures due to climate change.…read more

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Rising temperatures themselves may contribute to more carbon dioxide.
Maintaining the Balance
We may be able to maintain the balance of the carbon cycle by sing biofuels and reforestation.
This is fuel that comes directly from plants. Because the amount of carbon dioxide released when
burnt is the same amount that the plant took up when it was growing it is said to be carbon neutral
and so it would not put more carbon dioxide into the air.…read more

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