AS Biology (SNAB) : Biodiversity and Natural resources & Voice of the Genome

Summary/ Notes on the AS Biology topics (using edexcel SNAB textbook)
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AS Biology notes: Biodiversity and Natural Resources
>What is a species?
`A species is a group of organisms with similar morphology, physiology, and
behavior, which can interbreed to produce fertile offspring, and which are
reproductively isolated (in place, time or behavior) from other species.'
[Identifying species can be done through modern techniques e.g. DNA analysis]
>Habitats and communities
Is literally a place where the organism lives. Each habitat has a particular set of
conditions which supports a distinctive combination of organisms. Populations are
within habitats. Each population is a group of interbreeding individuals of the same
species found in an area.
>Niche / ecological niche
`The way an organism exploits its environment'. If two species occupy the same
niche they will compete with each other, the better adapted organism will outcompete
the other and exclude it from the habitat. E.g. In England the grey and red squirrel.
Example: 3 species of wood pecker can coexist in the same habitat because
each has a different niche. The tiny lesser spotted woodpecker prefers the finer
branches at the top of the trees, whereas the great spotted feed on the broader
branches. The green wood pecker tends to feed on the ground.
>Adapting to environments
Being adapted? = being specialized to suit the environment in which the
organism lives. Adaptations? = features which enable the organism to survive can be
classified as behavioral, physiological or anatomical.
Behavioral: any actions by organisms which help them to survive and
reproduce. E.g. plants respond to their environments by turning their leaves towards
the sun, so maximizing the amount of light needed for photosynthesis.
Physiological: any features of the internal workings of an organism which help
them to survive or reproduce. E.g. hot springs are an extreme environment but
Thermophilious bacteria are physiologically adapted to it. This is because they have
heat stable enzymes which cause them to tolerate the highest temperatures.
Anatomical: the structures we can see when we observe or dissect an
organism. E.g. bumblebee bodies show anatomical adaptations to collect pollen and
nectar. For example a long tongue through which it can suck nectar from flowers and
pollen basket on hind legs allowing pollen to be carried back to the nest.
>Natural Selection

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Is the mechanism by which organisms change over time as they adapt to
changing environments. As a population increases in size organisms will die/ fail to
reproduce due to competition for resources e.g. food/space, also could be due to
disease/ extreme environmental conditions. `Struggle for existence' = striving for
>Survival of the fittest
Those organisms that, by chance, possess some characteristics which gives
them an advantage over others.…read more

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example Homo sapiens
>Sorting and Grouping
Classifying organisms based on shared features is known as taxonomy.
Linnaeus created the first classification system, grouping organisms according to their
visible similarities and differences. A taxonomic hierarchy is created to organize
organisms the hierarchy of groups is as follows:
Kingdom ..........e.g. Animalia
Phylum.............e.g. Chordata
Class ...............e.g. Osteichthyes
Order ...............e.g. Perciformes
Family .............e.g. Chaetodonitidae
Genus ..............e.g. Chaetodon
Species .............e.g. Chaetodon kleinii
There are 5 Kingdoms: Animalia, Plantae, Fungi, Protoctista and Prokaryotae.…read more

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Random mutations ~ changes in DNA sequences in cells= new alleles
Measuring Biodiversity
>Species Richness
Counting the number of species present in a given habitat. E.g. Wood in
southern England (S.E) = 25 butterfly species, but similar area in south America (S.A)
= 10x as many. So S.A. has more biodiversity then S.E.
>Species Evenness
A community in which most of the species have similar abundances is said to
have high evenness no single species dominates a community.…read more

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Cell Walls Cellulose
A plants strength = partly from cellulose walls of plant cells and the `glue' that holds
them together.
(Are two forms of glucose: alpha and
2 beta glucose joined (one
rotated 180o) in condensation reaction ­
in OH groups
glucose chain = molecule of
Cellulose= polysaccharide
Polymer of glucose different to starch
(made of beta glucose) has 1,4
glycosidic bonds instead of 1,6 in
starch cellulose is long unbranched
because of this.…read more

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Tubes for transport and strength
Some cells must be stiffened and some allow water and minerals to pass from roots to
leaves are 2 specialized types of cells to do these functions:
xylem vessels : form tubes for transport, and stiffened cell walls help support
the plant
sclerenchyma fibres: columns of these cells with their stiffened cell walls also
provide support
Are 3 basic types of tissue in plants:
dermis tissue (epidermis)
vascular tissue ( cross section of stem)
ground tissue (roots)
Vascular tissue has…read more

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Xylem vessels also transport minerals ­ inorganic ions.
Movement of water = mass flow system for transport of inorganic ions. Absorbed
through roots by active transport.
Nitrate ions= needed for amino acids in order for plant to grow (cytoplasm is largely
made of proteins, also chlorophyll, nucleic acids, ATP contain nitrate ions.…read more

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Could treat condition called dropsy/Oedema (now) where fluid accumulates in body's
tissues caused by heart/kidney problems fast irregular heartbeat=symptom
William Withering caused it to be an accepted form of medicine steps: ...
1.) Withering tested the drug on patients with the disease and recorded side affects
2.) Used standard procedure to discover the effective dosage
3.) He slowly increased dose until patients experienced diarrhoea and vomiting
4.) Then reduced the dose slightly and recorded all results meticulously
5.…read more

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In flowering plants the ovule is fertilized by the nucleus from the pollen grain and
develops into the seed.…read more

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Definition: It is meeting the needs of the present generation without compromising
the ability of future generations to meet their needs.
Use of oilbased plastics and fuels isn't sustainable because:
~ burning oilbased fossil fuels releases CO2 into atmosphere
~Oil reserves will eventually run out
~Plastics generate nonbiodegradable waste waste disposal problems
Using plant based products reduces these problems > even though still CO2 is
produced it's balanced out so no change in atmosphere.…read more


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