National 5 Revision
Life on Earth
• A BIOME is a region of the planet with
characteristic climate, flora and fauna
• A NICHE is the role an organism has within its
community in an ecosystem
•All of the organisms living together in habitats,
populations and communities as well as the non
living components is called an ECOSYSTEM
• The interaction between organisms requiring
the same resources is called COMPETITION
Food Webs
• The
producer is always the first organism in a food
chain or web
•The first organism that eats a producer is the primary
consumer
•If a primary consumer died out, the producer
numbers would increase and the number of secondary
consumers would decrease
Pyramid of Numbers
•A pyramid of numbers shows the relative numbers of
organisms at each level of a food chain
•In a pyramid of numbers, the organism at the bottom is
always the producer, followed by the primary consumer
above it and the secondary consumer at the top
Measuring Abiotic Factors
• Light intensity can be measured using a light
meter
• To minimise errors when sampling the light in
an area, we would take multiple readings at
the same time of day and also ensure no
shadow is cast on the meter
• Temperature is measured using a
thermometer
• To minimise errors when using a
thermometer, allow the reading to stabilise
and if using a soil thermometer, wipe the
probe between readings
•pH is measured using a pH meter
•To minimise errors when sampling pH we would
wipe the probe between readings
Adaptation, Natural Selection and
Evolution
• Mutations are a random and
spontaneous change in genetic material
• Mutagenic agents such as radiation, (x-rays,
gamma rays, UV rays) and chemicals cause an
increase in mutation rate
• Natural selection allows the best adapted
organisms to survive and pass on their favourable
genes to future generations
• Speciation occurs after a population has become
isolated by an isolation barrier. These can be
geographical, ecological or reproductive barriers
Human Impact on the Environment
• When pesticides are sprayed
onto crops, this affects other
organisms in the food chain.
Pesticide toxicity can build up
and accumulate in the bodies of
organisms higher up the food
chain e.g. the organism at the
top of the food chain will have
the highest toxicity levels from
the pesticide
• As an alternative to pesticides,
biological control can be used
e.g adding ladybirds to a bush to
get rid of greenflies